Characterization of Sealing Surface forStatic Seals

Anandu Raja MohanNiranjan Sutar

Master of Science Thesis TRITA-ITM-EX 2019:591KTH Industrial Engineering and Management

Machine DesignSE-100 44

STOCKHOLM

Abstract

Master of Science Thesis TRITA-ITM-EX 2019:591

Characterization of Sealing Surface for Static Seals

Niranjan Sutar, Anandu Raja Mohan

Approved Date

11/09/2019Examiner

Ulf SellgrenSupervisor

Stefan Bjorklund

Commissioner

SCANIA CV ABContact Person

Mikael Sundgren

Leakages from seals are one of the important factors that are taken into considerationwhile designing any machining element. This is because leakages can affect the perfor-mance of any component and can also turn into a catastrophe. If looked into it, manyparameters can be pointed out that can enhance leakages within the system, some ofthem may be pressure, temperature, clamping force and bolt distance etc.But the main parameter is the surface roughness, higher the roughness more the leak-age and vice-versa. Thus, in this thesis an attempt has been made how the surfaceroughness can affect the performance of the sealing concept for metal bounded gasketwith above four mentioned parameters. Also how leak proof surface can be definedusing standard tribological parameters is the aim of this thesis.This report includes the results for methodologies implemented during the thesis andtrack down the leakages. The leaked surfaces were carefully studied and analyzed usingdifferent standards compared with the non leaked surfaces’ roughness parameters.

Keywords: Ladder frame gasket, surface roughness parameters

i

Sammanfattning

Examenarbete TRITA-ITM-EX 2019:591

Karakterisering av Tatningsytan for Statiska Tatningar

Niranjan Sutar, Anandu Raja Mohan

Godkand Datum

11/09/2019Examinator

Ulf SellgrenHandledare

Stefan Bjorklund

Kommissarie

SCANIA CV ABKontaktperson

Mikael Sundgren

Lackagerisk fran tatande forband ar en av de viktigaste faktorerna som beaktas vid utformning av kon-struktionsartiklar. Detta pa grund av att konsekvenserna kan bli forodande. Det tatande forbandetpaverkas av manga olika parametrar sasom till exempel tryck, temperatur, klamkraft, skruvavstandoch val av packning. En viktig faktor ar ytans beskaffenhet; Generellt lacker en grov yta och vagigyta mer an en fin och plan yta. Saledes har i denna avhandling ytans beskaffenhet studerats tillsam-mans med en packning av typen metallburen gummipackning for att pavisa tathetfunktionen som enfunktion av tryck, temperatur, klamkraft och skruvavstand. Denna rapport innehaller resultat ochanalys av olika standardmetoder for de ytor som ingick i utredningen.

ii

Foreward

The research for this thesis work was carried out in collaboration with Scania CV AB andMachine Design Department at KTH ROYAL INSTITUTE OF TECHNOLOGY,Stockholm from January 2019 to July 2019. We are very grateful to Scania for giving us anopportunity to work in their organization. It was our pleasure to work at NMBC, R&D,Scania and the journey was full with immense learning experience. We would like to takethis moment to express our heartfelt admiration to those who helped in our way to completethis thesis.

We would like to thank our supervisor Mikael Sundgren for giving us a wonderful oppor-tunity to work under such a challenging and interesting project. He has been our backbonestrength and support throughout this project guiding and showering us with his invaluableinsight and knowledge in this topic which we cannot thank him enough. Also we would liketo thank all the other people from Scania who helped us in different stages of our thesis tokeep it moving and achieving our goal.

Stefan Bjorklund, our supervisor at KTH has been a constant source of help for us. He wasalways available for us when we ran into problems or being stuck at some point by guiding usthrough the right path and also giving us alternatives of approaching a problem. We wouldalso like to thank Ulf Sellgren, our examiner at KTH for giving us the timely support andproviding us with help whenever needed.

We would like to thank our parents and friends for their constant support and encouragementthroughout our studies and through the process of thesis. Finally, all praises to almighty.

Anandu Raja Mohan , Niranjan Sutar

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’

Nomenclature

FEA Finite Element Analysis

MR1,MR2 Material ratio delimiting the core area

Ra Arithmetic mean deviation of the assessed profile

Rk Core roughness depth

Rp Maximum profile peak height

Rpk Reduced peak height

Rsk Skewness of assessed profile

Rt Total height of the profile

Rv Maximum profile valley depth

Rvk Reduced valley depth

Rz Maximum height of the profile

2D Two Dimensional

3D Three Dimensional

AC Air Conditioning

ANSYS Analysis Systems

ASCII American Standard Code for Information Interchange

HV High Voltage

ISO The international organization for Standardization

KTH Kungliga Tekniska Hogskolan

STD Standard

UV Ultra Violet

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Contents

Abstract ii

Foreword iii

Nomenclature iv

1 Introduction 11.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Overall Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.4 Delimitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41.5 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.5.1 Requirement Specifications . . . . . . . . . . . . . . . . . . . . . . . . 51.5.2 Methodology Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.5.3 Methodology Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2 Frame of Reference 92.1 Surface measurement standards . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2 Surface parameters definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.3 Surface measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142.4 Manufacturing process for milling . . . . . . . . . . . . . . . . . . . . . . . . . 182.5 Surface contacts and 3D plotting of surfaces . . . . . . . . . . . . . . . . . . . 182.6 Previous work regarding similar sealing concept . . . . . . . . . . . . . . . . . 192.7 Sensors and Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.7.1 Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192.7.2 Pressure Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192.7.3 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3 Implementation 223.1 Rig Modification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.1.1 Test Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223.1.2 Seal Modification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.2 Preliminary Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253.3 Methodology Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273.4 Methodology Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313.5 Auxiliary Experimental Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . 333.6 Tracking of Leakage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4 Result and Discussions 354.1 Results from Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.1.1 Preliminary Experiments . . . . . . . . . . . . . . . . . . . . . . . . . 354.1.2 Methodology Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354.1.3 Methodology Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364.1.4 Auxiliary Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.2 Results from Analysis and 3D Plots . . . . . . . . . . . . . . . . . . . . . . . 38

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5 Conclusions 48

6 Future Work 51

7 Appendix 527.1 Gantt Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527.2 Work Breakdown Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 527.3 Risk Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

8 Additional Figures 54

List of Figures

1 Ladder Frame Gasket . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Overall Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Evaluation, Sampling and Cutoff length . . . . . . . . . . . . . . . . . . . . . 94 Roughness Parameter Rp,Rv . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Roughness Parameter Ra,Rq . . . . . . . . . . . . . . . . . . . . . . . . . . . 116 Roughness Parameter Rt,Rz . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 Abbot Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 Probability Density Curve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 Taylor Hobson PG800 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1410 Taylor Hobson user interface . . . . . . . . . . . . . . . . . . . . . . . . . . . 1511 Mahr MarSurf M300C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1612 Optiv321GLtp machine and camera . . . . . . . . . . . . . . . . . . . . . . . 1613 ZYGO Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1714 ZYGO User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1815 Temperature Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1916 Pressure Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2017 Multi-Point Curve Fitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2118 Chamber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2219 Original Seal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2420 Milling on Seals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2421 1. Whole milled surface 2. Cross milled surface . . . . . . . . . . . . . . . . . 3522 Leaked Aluminum Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3823 Non-Leaked Aluminum Surface . . . . . . . . . . . . . . . . . . . . . . . . . . 3924 Roughness Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3925 Leaked VS Non Leaked Surface . . . . . . . . . . . . . . . . . . . . . . . . . . 4026 Reduced Peak Height and Reduced Valley Depth . . . . . . . . . . . . . . . . 4127 Material Ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4128 Rpk to Rvk ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4229 Peak and Valley Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4230 Leaked Mild Steel Surface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4331 Non-Leaked Mild Steel Surface . . . . . . . . . . . . . . . . . . . . . . . . . . 4432 Roughness Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4433 Leaked VS Non Leaked Surface . . . . . . . . . . . . . . . . . . . . . . . . . . 4534 Reduced Peak Height and Reduced Valley Depth . . . . . . . . . . . . . . . . 4635 Material Ratios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4636 Peak and Valley Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4737 Reduced Values and Area Ratios . . . . . . . . . . . . . . . . . . . . . . . . . 4738 Gantt Chart 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5239 Gantt Chart 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5240 WBS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5241 Line formation and bubbles formations . . . . . . . . . . . . . . . . . . . . . . 54

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List of Tables

1 Requirement Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 Methodology Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Design of Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Roughness Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Recommended cut-offs for different surface finishes . . . . . . . . . . . . . . . 106 Preliminary Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 Marking Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268 Methodology Stage 1 test with Single Seal . . . . . . . . . . . . . . . . . . . . 289 Methodology Stage 1 test with 3 seals . . . . . . . . . . . . . . . . . . . . . . 2910 Limits of Temperature and Pressure . . . . . . . . . . . . . . . . . . . . . . . 3011 Maximum and Minimum Limits . . . . . . . . . . . . . . . . . . . . . . . . . . 3112 Methodology Stage 2 - Critical Conditions . . . . . . . . . . . . . . . . . . . . 3213 Testing with Scania Oil - 10W 40 . . . . . . . . . . . . . . . . . . . . . . . . . 3314 Line formation pressure temperature and time relations . . . . . . . . . . . . 3615 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4916 Risk Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

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1 Introduction

Seals are mechanical components that are mostly used in different engineering appli-cations that help to avoid leakages in the system. Sealing concepts took a boom inadvancement after the invention of internal combustion engines and especially moreduring first and second world war. Advancement in technology also widened the ap-plications of seals. In todays world, seals are not only used in automobile industrybut also in medical and electrical applications. Based on the applications, seals can bedivided into two main types.

• Static Seals

• Dynamic Seals

When the relative motion between the sealing surfaces is zero then Static Seals areused. But in some applications, where there is relative motion between the sealingsurfaces dynamic seals are used. These seals can also be further classified on the basisof its shape, material properties and manufacturing processes. In this thesis, staticseals are the ones dealt with. There are different types of static seals in which, onecalled as rubber bonded metal gaskets or ladder frame gaskets is considered for testing.

1.1 Background

The test rig used in this thesis is been built by a group of students from KTH RoyalInstitute of Technology within the Machine Design Advanced Course. The test rigwas built for Scania under the intension of future research. The test rig has somemodifications done in order to make this thesis work possible which will be explainedlater in this report. It included the design of a chamber that has capabilities to replicatethe conditions in the engine oil sump. Rubber bonded metal gaskets also known asladder frame gaskets (Figure 1) which are attached to the oil sump are used in realitybetween the aluminium oil sump and grey cast iron engine block. Hence the test rigis also designed in such a way that it has a chamber as shown in Figure 18 with sealsin-between replicating the engine block. In this thesis an attempt will be made onfinding how the surface roughness parameters affect the performance of static seals.

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Figure 1: Ladder Frame Gasket

Initially, when investigating external parameters that may cause the seal to leak,only the temperature and pressure were considered. But at a closer look, there aremany other parameters that cause leakages through the seals. Those parameters arebriefly discussed in the methodology section. The test rig chamber was modified fortesting three surfaces roughness combinations in parallel to reduce the time for theremaining tests. The next section describes overall concept and the test chamber andwill give an idea of complete working of the rig.

1.2 Overall Concept

The selected system is viewed schematically in Figure 2. The fundamental part is atest chamber that contains of two halved seal joint together with the silicon. The testchamber is placed in a circulating system where the working fluid is oil. The circulationis done by a electrically driven pump and the system is pressurized by a hand pump.The components are generally connected with hydraulic hoses but one section in theflowing system is a metallic tube. To heat the oil, this metallic tube is wrapped witha heating belt. The working principle is that the circulating pump will transmit theliquid to the metal tube and the heating belt will heat the metal tube and the oilpassing through it. After some time of circulation, the temperature will reach therequired value. The temperature and pressure in the oil is measured before it entersthe chamber using sensors which transmits signals to an Arduino logic board. If thetemperature and pressure are out of set limits, Arduino will shut down the power ofthe circulation pump and heating belt by using a four channel relay control system.Two pressure relief valves will be included in the system. The opening pressure is 20bar. If the internal pressure is over 20 bar, the pressure relief valves opens so that thecomponents are safe. These pressure relief valves opening pressures can be varied by

2

a set screw. The hydraulic system is designed in such a way that there are 3 differentflow paths for different purposes.

• First is for filling up the oil in the chamber. In this the oil is pumped fromreservoir using a pump to the chamber through the heating coil.

• Second is the circulation mode. In this mode, the reservoir is cut off fromthe previous path so that oil which is filled in the chamber itself is circulatedagain and again. The reservoir is bypassed to reduce the heating time of the oil.The reservoir has 40L of oil and circulating the oil through the reservoir wouldincrease the heating time by several hours.

• Third is the draining mode. In this mode the reservoir is connected back to theoil flow circuit. Also the top valve from the chamber is cut.

Figure 2: Overall Concept

The oil is mixed with a fluorescent additive in order to make it easy to identifythe leakage. An UV light torch is used for inspecting the chamber. Inspection is donethroughout the testing and if there is an oil leakage, oil at the position of leakage willglow in UV light due to the effect of the additive. The leakage position is noted andstudied further for its surface characteristics.

3

1.3 Purpose

The test rig is built to serve the purpose of testing different sealing concepts undergiven conditions. The main purpose of this thesis is to test the rig using a Ladderframe gasket under different conditions. Scania, in same cases, uses only Rz as aroughness parameter in the drawing for manufacturing different parts. Scania hasobserved leakages also with earlier sealing concepts like fibre gaskets and rubber coatedsteels and therefore Scania has chose more robust sealing concept like metal boundedgaskets. This thesis is mainly focused on checking which combinations of parametersthat are best suited for leak proof surfaces. The different deliverable aimed for aregiven below.

1.4 Delimitation

As this project aims to evaluate the factors which affect the design of a sealing conceptand to understand how these components interact, all the major possible factors aretaken into account. But still there are few that are considered to be acceptable ifneglected.

• A chamber developed for the project will be used instead of complete engineblock.

• The testing time will not be as long as real life engine life.

• The seal is reduced in size in order to avoid handling large components.

• All the effects caused due to flow variations of oil during circulation are neglected.

• Effects of vibrations are neglected.

1.5 Methodology

After a series of brain storming section, the response variables causing leakage is pointeddown. In order to set the Design of Experiments, a test is done on the rig to findthe limits. The modified test rig is used to find the parameters causing leakage inan engine when static seals are used. This is achieved by conducting experimentsusing the concept of factorial design. The parameter range is essential to conduct theexperiments and hence the methodology is divided into two stages to obtain the limits.The experiments are also conducted by using two different oil to check whether oilproperties an effect on leakage. First the experiments are conducted by using oil grade5W20 (Motor Oil) and then results are also obtained by using Scania engine oil 10W40. This experiment also compares the different surface leakage behaviour with the oilproperties.

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1.5.1 Requirement Specifications

Scania has provided the requirements that has to be maintained while testing. Theseranges are maintained to find the prime factors responsible for leakage and also to comeup with how to make it leak proof. Table 1 shows the requirements.

Table 1: Requirement Specification

Property Value Comments

Sealing Conditions

Medium to be sealed from Oil primarily, fuel and -coolant as option

Peak Temperature and Duration 140 ◦C ≥ 24h -

Working Pressure 1 - 15 bar Absolute Pressure

Technical Requirement

Clamping Torque 26Nm -

Force per bolt 18kN -

Pitch between bolts Max 130 mm/ Min 27 mm -

Bolt specification Flange screw M8 -

Scania p/n 2505658

Material Requirements

Material Specification STD4498; STD4495; STD4494 -

Working Hours

Testing time per sample 1100 hrs -

Mating Parts and Sealing Faces

Mating part 1 Mating part 2

Material type Aluminum (STD4286) Cast Iron (CGI400

ISO 16112)

Surface Structure Rz 16 Rz1max 22 Rz16/Rp10

Surface Flatness 0.05/50 0.2

Porosity STD4369 Defect class 1/ STD4100 Defect

defect level 1 class 1/ defect level 1

Waviness N/A N/A

Surface treatment No No

Test Specimen Dimensions

Length, width, Height Related to the tested seal -

Specimen Shape Closed loop -

Leakage Detection and Control

Leakage Detection Visual/ Camera/UV -

Control temp and pressure PC Keyboard/Control knob -

Display LED Screen / PC Monitor -

5

1.5.2 Methodology Stage 1

Methodology Stage 1 is done to find the extreme limits of pressure and temperatureat which the seals work fine. Experiments are conducted according to the Table 2.The values of pressure and temperature are gradually increased from minimal valueto maximum value every 30 minutes and leakages are inspected every 5 minutes. Thevalues at which oil leaks are noted. This helps the user to monitor effectively at thenext stage.

Table 2: Methodology Stage 1

Temperature Pressure Motor Speed Time (mins)(Deg Cel.) (Bar) (RPM) 5 10 15 20 25 30

20 4 55530 5 55540 6 55550 7 55560 8 55570 9 55580 10 55590 11 555100 12 555110 13 555120 14 555130 15 555140 16 555

The test is done by assuming that other parameters are constant. The clamping torqueof the bolt is kept at 30 Nm and the pitch between the bolt 69 mm. Vibrations areneglected and flow rate is kept constant. The experiment is conducted for 30 min pereach condition. The tests are repeated to find the repeatability of the results.

1.5.3 Methodology Stage 2

Methodology Stage 2 is an extension of the previous one. It is initially important tounderstand which parameters would affect the leakage in the seal during its service.Some of the parameters within the scope of this thesis would be:

• Pressure

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• Temperature.

• Bolt Distance.

• Clamping Force/Bolt

• Surface Roughness

Vibrations can also be a parameter but it was excluded from the scope of this thesis.To include all these variables, it is efficient to use an experimental design setup. Inthis case it would be a full factorial design is used. The rig is tested under differentconditions for all the parameters according to the design structure. The limits ofpressure and temperature values are decided from Methodology Stage 1 as explainedin 1.5.2 and the rest parameters’ range are decided after close discussion with Scania.Scania has given requirements which have to be maintained during testing. The limitsfor bolt distance and clamping torque are decided considering the requirements andfrom which extreme ends are used as limits for both distance and clamping torque.

Table 3: Design of Experiments

Sr No ParametersPressure Temperature Bolt Distance Clamping Torque

(Bar) (Deg Celsius) (mm) (N-m)1 + + + +2 - + + +3 + - + +4 - - + +5 + + - +6 - + - +7 + - - +8 - - - +9 + + + -10 - + + -11 + - + -12 - - + -13 + + - -14 - + - -15 + - - -16 - - - -

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The experiment is about testing the different parameters each having two differentvalues probably the low and high extreme values which is denoted as + and - in thetable. The different combinations of parameter values are tested under which leakageis checked. Thus helping to track down the parameter affects on the system.In table 4. R1, R2 and R3 represents the different values of roughness for the platesused in the chamber. This experiment combinations in table 3 helps to achieve the pur-pose of finding the boundary conditions of various parameters for specified roughnessvalues. This information also helps to come up with a recommendation for defining theroughness parameters in the drawings for machining which is mentioned in the section5. The notations R1, R2 and R3 indicates the roughness values that SCANIA uses fordefining surfaces during its manufacturing. The following table 4 shows the values forR1, R2 and R3.

Table 4: Roughness Definition

NotationRz Value

(µm)

R1 20

R2 10

R3 5

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2 Frame of Reference

As this project covers vast number of theories and standards, it is important to identifyand learn the same. Following are references searches that are relevant within thisproject

2.1 Surface measurement standards

Understanding the standards is important for setting up a relevant measurement ofthe surface. Factors such as, cutoff length, filtering, sampling length and evaluationlength. As a conclusion from the meeting in SCANIA Sodertalje, it was understoodthat SCANIA uses a handful of standards which were provide to us (STD SS-EN ISO1302, STD 4261, STD SS-EN ISO 4287,4288).ISO 4288-1996 defines standards for different measuring techniques for surface.ISO4287-1995 defines different roughness parameters.[2]The following parameters are important to be considered before a measurements areconducted.

• Sample Length,lThe nominal wavelength used for separating roughness and waviness. It is alsoknown as Cut off or Cut off Length.

• Evaluation Length,LIt is also known as Assessment Length. It is the length over which values ofsurface roughness are measured.

Figure 3: Evaluation, Sampling and Cutoff length

• Cut off length It is also called as sampling length as shown is figure 3 and isdefined in table 5.

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Table 5: Recommended cut-offs for different surface finishes

Recommended Cut-offs ISO 4288-1996

PeriodicProfiles

Non-PeriodicProfiles

Cut-off

Samplinglength/

Evaluationlength

SpacingDistance

(mm)Rz (µm) Ra(µm) λ c(mm) λc(mm)/L

>0.013-0.04 To 0.1 To 0.02 0.08 0.08/0.4

>0.04-0.13 >0.1-0.5 >0.02-0.1 0.25 0.25/1.25

>0.13-0.4 >0.5-10 >0.1-2 0.8 0.8/4

>0.4-1.3 >10-50 >2-10 2.5 2.5/12.5

>1.3-4.0 >50 >10 8 8-40

ISO 4288-1996 also defines these above lengths for various cases. Table 5 definesstandard length sizes for different roughness profiles.

2.2 Surface parameters definitions

As the main purpose of this project is to find which surface roughness along-withits parameters is suitable for a leak proof sealing concept. For example Ra, Rz, Rp,Rv, Rvk, Rpk etc. are the parameters suggested to be studied in order to predictleakage. In this project the preferred text book in the subject is Handbook of SurfaceMethodology [1] in which parameters are defined for surface roughness.

The terminologies which are studied are explained below.[2]

• Maximum Profile Peak Height,Rp

The distance between the highest point of the profile and the mean line withinthe evaluation length

• Average Maximum Profile Peak Height,Rpm

It is the average of the successive values of Rp calculated over the evaluationlength.

10

Figure 4: Roughness Parameter Rp,Rv

• Maximum Profile Valley Depth,Rv

It is the distance between the deepest valley of the profile and the mean linewithin the evaluation length

Figure 5: Roughness Parameter Ra,Rq

• Roughness Average,Ra

It is the arithmetic average of the absolute values of the profile heights over theevaluation length.

• RMS Roughness,Rq

It is the root mean square average of the profile heights over the evaluation length.

11

Figure 6: Roughness Parameter Rt,Rz

• Maximum Height of Profile,Rt

It is the vertical distance between the highest and lowest points of the profilewithin the evaluation length.

• Average Maximum Height of the Profile,Rz

It is the average of the successive values of Rt calculated over the evaluationlength.

• Maximum Roughness Depth,Rmax

It is the largest of the successive values of Rt calculated over the evaluationlength.

Figure 7: Abbot Curve

• Core Roughness,Rk

It is the core height of the profile along the Y axis of the Abbot curve generatedby placing a 40% line on the curve at the minimum slope point and extending

12

the lines to the 0% and 100% points. In simple terms can be said as the depthof core roughness profile.

• Reduced Peak Height,Rpk

It is the height on the Y-axis of a triangle with the same area as the BAC curvefrom the 0% point to the Mr1 point. It can also be explained as the mean peakheight protruding from the core roughness profile.

• Reduced Valley Depth,Rvk

It is the height on the Y-axis of a triangle with the same area as the BAC curvefrom the Mr2 point to the 100% point. It can also be explained as the meanvalley depth protruding from the core roughness profile.

A1 =1

2.Mr1.Rpk

A2 =1

2.(1 −Mr2).Rvk

• Mr1 and Mr2 are the smallest and highest material ratios of the roughness coreprofile.

Figure 8: Probability Density Curve

• Skewness,Rsk

It is a measure of asymmetry of the profile with respect to mean line. Positiveskewness means more values are below the mean line and negative is vice versa.

13

2.3 Surface measurements

Different kind of surface measurement machines were used for evaluation. Differentmachines were used to serve to different purposes.

• Taylor Hobson PG 800 [3]This machine is the contact type surface measurement machine. It has a probethat slides on the surface to be measured for set length. For this thesis, thismachine was used to conduct 2D surface measurements during initial stages butlater on it was discontinued to use because of its limitations.

Figure 9: Taylor Hobson PG800

The Figure 9 above is the actual machine Taylor Hobson PG800 machine with itsdiamond tip (dia 0.2 µm). This machine can also measure surfaces in 3D but thatis quite time consuming. The Figure 10 shows that how the surfaces are definedaccording to the required standards. It can also plot the Abbott-Firestone curvewith Material ratio graphs.

14

Figure 10: Taylor Hobson user interface

• Mahr MarSurf M300 C

This machine is a portable surface measurement device used for 2D plotting andis used extensively on the production floor. Since it is portable it is easy to usefor checking surfaces which are freshly machined. This machine is also of contacttype with a diamond tip which slides on the surface to be measured. It has twomodules: Probe Stick and Output display. These two modules are connected byBluetooth. The Probe is kept on surface to be measured and the display unitshows the plot for roughness. It can also calculate and plot complex parameterslike Abbott Firestone curves and its parameters. These plots and parameters canalso be exported in ASCII file format and the machine has the ability to printresults on place. This machine was used at two occasions; while manufacturingsurface roughness plates and while tracking the leakage path. The Figure 11shows the two modules of a system. [12]

15

Figure 11: Mahr MarSurf M300C

• Optiv 321GLtp [13]

This machine does not measure surface parameters. It consists of a simple camerawith different magnifying lenses. With the help of this machine it is easier tospot the leakage paths and how oil flows through the rubber area.

(a) Optiv 321GLtp

(b) Zoom Camera view

Figure 12: Optiv321GLtp machine and camera

16

• Zygo Metropro

This machine is of non contact optical machine type and plots the 3D surfacesusing reflected light from the surface within the limits of the light flash.The Figure13 depicts the actual machine [14]

Figure 13: ZYGO Machine

This machine is one the most efficient and can achieve high resolution. It canplot the surface with three different lenses (5x, 10x and 50x) within seconds orcouple of minute depending which lens is been used and the resolution. It canalso stitch the surfaces in order to study surfaces with large areas. For example,in this thesis 10x zoom lens is used that can plot a 1 sq.mm area in one run. Butusing stitching concept it was possible to study the surface with 4mm x 2.5mm.

Figure 14 shows the user interfaces where one can study the surface in 3D at theupper right corner of the interface. The software also allows the user to observethe surface in top view as can be seen in on top left side of figure 14 and the usercan draw lines anywhere to obtain 2D surface profile as seen in bottom left corner.The roughness parameter values are also shown at respective 2D line which canbe noted. One can also see an actual image of the surface in the zoomed cameraview.

17

Figure 14: ZYGO User Interface

2.4 Manufacturing process for milling

The manufacturing parameters like feed rate, spindle speed, depth of cut etc. affectsadversely on the surface roughness. These parameters are defined by SCANIA as theyare responsible for manufacturing the roughness plates and the chamber. There areplenty of work done in this subject and lots of research papers and thesis reportsare available over internet and library. One of them is written by group of Indianprofessors , and the reports name is Prediction of Surface Roughness in Milling byMachine Vision using ANFIS. While manufacturing, same machining parameters wereused as recommended in the above mentioned research paper.[4] But due to someunknown factors those recommendations did not gave anticipated surface roughnessvalues.

2.5 Surface contacts and 3D plotting of surfaces

Many people have worked with 3D plots showing the contact between two surfaces. Itwould be necessary to observed about what parameters of surface roughness parametersare considered and why. One recent PhD was done in Lulea University in which thatstudent plotted 3D map of the surface and simulated the flow of the oil though thevalleys of the surface. But in this report no sealing material was considered. But itcan prove important to know his methodology for plotting 3D map. [5]

18

2.6 Previous work regarding similar sealing concept

A lot of work is been done within similar sealing concept before, especially in gasketsand many research papers can be found. However, no articles have been found whereoptimal surface roughness for this kind of seals are addressed. A research paper namedLeakage Monitoring in Static Sealing Interface Based on Three Dimensional SurfaceTopography Indicatormight was useful because how the leak rate can be measured wasmore explained in reference [9][10].

2.7 Sensors and Calibration

2.7.1 Temperature Sensor

A temperature sensor is a device, usually an RTD (resistance temperature detector) ora thermocouple, that collects the data about temperature from a particular source andconverts the data into a form understandable by user. The temperature sensor usedfor the rig is a RTD and is shown in figure 15

Figure 15: Temperature Sensor

The temperature sensor used in this project is a screw-in RTD temperature probewith J head form Terminal.It can work effectively in a temperature range of -50◦C to400◦C. This sensor comes with a transmitter which helps to connect the sensor withArduino and thus in turn with laptop for efficient monitoring. As the temperaturerange of oil in this project varies from 0◦C to 150◦C, this temperature sensor servesthe best.

2.7.2 Pressure Sensor

Pressure Sensor is an instrument consisting of a pressure sensitive element to deter-mine the actual pressure applied to the sensor and uses transmitter to convert this

19

information into an output signal. The pressure sensor used in this project is a Piezoresistive one which measures 0-25 bar relative pressure. The sensor is shown in Figure16

Figure 16: Pressure Sensor

The pressure probe can withstand only up to a temperature of 100◦C. In order toresolve this problem, a cooling element is used to between sensor and the valve. Thehot oil passes through the cooling element to reach the sensor at which the temperatureof the oil will be reduced to a certain extend. This helps the sensor to work efficientlyat higher temperatures.

2.7.3 Calibration

A sensor must be calibrated in order to achieve the best possible accuracy. No sensoris perfect and the sensor is only one of the many components used in a measuringsystem. For example, temperature sensor is subjected to thermal gradients betweenthe sensor and the measuring point. The two most important characteristics of a sensorare precision and resolution. Precision of a sensor can be affected due to noise andhysteresis. The different methods of calibrating a sensor are

• One Point Calibration

• Two Point Calibration

• Multi-Point Curve Fitting

• Maxim 31855 Thermocouple Linearization.

In this project, the sensors are calibrated using the Multi-Point Curve Fitting method.Figure 17 shows the plot comparing ideal and actual response using Multi-Point CurveFitting.

20

Figure 17: Multi-Point Curve Fitting

Since the temperature and pressure sensor has to work under its maximum mea-suring limits, linearity cannot be expected. The responses from the sensors are takenat multiple points and the slope is found by using polyfit command in Matlab. Idealresponses are measured by using a calibrated device and the slope for the same is alsocalculated. The factor in which the ideal and actual response are varied is calculatedand rectified in order to calibrate the sensor.

21

3 Implementation

3.1 Rig Modification

3.1.1 Test Chamber

The chamber is sealed by the actual seal that is to be tested and the shape of thechamber therefore closely relates to the seal. the chamber lid with roughness plate areassembled using M8 screws. The design is simple and allows easy serviceability. Theoriginal metal bounded gasket is large by nature and will therefore be reduced in sizebefore testing. This will be done by removing sections of the gasket and form a smallerversion of the gasket, now with unintentional seams. The reasons for this is that theladder frame gasket is much bigger than other seals potentially used and the design ofthe test rig gets simplified if the test chamber is in roughly the same dimensions. Theunintentional seams will have to be sealed by the use of two component silicone. Thechamber design consists of the following parts viewed in Figure 18.

Figure 18: Chamber

22

• Position of fluid inlet and outlets.

• Cover of chamber.

• Seal

• Bottom half of chamber.

Two additional plates (one aluminium and one mild steel) are assembled as a partof modification. They are sandwiched between the upper and bottom chamber in anorder that no same material comes together. This is done to ensure that the realengine condition of aluminium engine block and cast iron oil sump joined using seal isreplicated. In the chamber there will be three seals kept in each total with the intentionof testing three different roughness conditions in one time. This is achieved by millingthe plates to different surface roughness allowing for different surfaces being in one testtime, three different combinations of sealing surfaces can be studied within the samecondition. This is a time efficient method.

3.1.2 Seal Modification

It was necessary to conduct some modifications within the seals itself. As shown inFigure 19, there are imprints in the seal which are found at the corners of the sealand at the centre. For example, if there is a leakage at point A , the oil could leakthrough the imprints at B or it could spread around the seal by travelling through theimprints. This would misguide the researcher and let him not finding the exact surfaceof leakage. In order to avoid this problem, actions were suggested which are explainedlater.

23

Figure 19: Original Seal

The seal surface is milled in order to create grooves at each interval so that the oilpath is directed through the pathway and can be seen close to the origin of leakage.This makes it easy to track down the exact position of surface which is responsible forleakage of oil. The modified seal is shown in Figure 20.

Figure 20: Milling on Seals

24

3.2 Preliminary Test

Initial checkups are done in order to make sure that the test rig works fine. They areexplained below.

• The hydraulic hoses where tightened and oil flow was tested throughout thecircuit to make sure that there is not leakage of oil at the connections.

• The sensors where inspected and calibrated for their limits.

• The insulation was inspected and increased on the modified chamber to reducethe heat loss and thereby reducing the time for heating the oil.

• The circulating pump and heating coil were tested for its proper functioning.

• The hand pump was drained and checked for its function.

• The pressure relief valve was tested at its maximum limits and checked for itsperformance.

• The silicon component was inspected and changed from one component siliconeto two component silicone since one component silicone takes longer time forcuring, which directly affects the time between testing.

Making sure that every individual component on the rig works fine, the initial testingfor functioning of whole test rig was done and findings are shown in Table 6. Also thestages of leakages are explained in table 7. The real experimental results for line andbubble formation is shown in figure 41.

Table 6: Preliminary Test

Temperature(◦C)

Motor Speed(RPM) Time(mins) 5 10 15 20 25 30

Pressure(bar) 2 3 5

70 100 3 3 3 3 3 3

80 250 3 3 3 3 3 3

90 400 3 3 m m m m

100 555 m m m m m m

110 555 m m m m m m

120 555 m m m m ⊗ ⊗130 555 ⊗ ⊗ ⊗ ⊗ ⊗ ⊗140 555 ⊗ ⊗ ⊗ ⊗ ⊗ ⊗

25

Table 7: Marking Definition

Markings Explanation

3 The surfaces show no oil stains or any sign of leakage

m The surface shows oil stains formed as a line surrounding the seal

7 Bubbles of oil popping out from specific spots

⊗ Silicone Burst

The preliminary tests can also be considered as a preparatory test for methodologystage 1. In this test, the temperature of the oil was varied from 70◦C to 140◦C andthe pressure values were varied between 2 bar to 5 bar. Each condition are tested for30 minutes and checked for leakage. Using the UV light torch, oil leakage was checkedcontinuously and noted. The 3 noted down in the table show that there is no leakageat any point in the chamber. The m show that there is a line formations of oil stainsaround the seals. Due to high temperature and pressure oil starts to appear as bubblesat some places on the seal which means that the oil starts leaking slightly. This ismarked as 7 in the table. A similar test is conducted three times in order to inspect forrepeatability. All tests were done with just one seal in the chamber. The metal plateswere not included in these tests. During these tests, the silicone was also inspectedand sometimes it bursts after some time due to less curing time. This is the reasonwhy silicone was changed from one component to two component.The temperatures were controlled using the heater control unit where the temperaturewas set in the heater control unit higher than that of required temperature because ofthe losses. For example, if the temperature need is 80 ◦C, then the temperature in theheating control unit would be around 95 ◦C. These values were obtained based on theexperience working with the rig until the steady state was achieved.From transitioning from one temperature to another temperature, it is obvious thatthe pressure would increase since the system is iso-volumetric, when the temperatureincrease or vice-versa. The pressure rise in the system was controlled by either usingpressure relief valves or inbuilt pressure relief valve in the pump whilst monitoring livefeed of pressure and temperature from Arduino code. But pressure was mostly controlusing inbuilt pressure relief valve in pressure pump as this was easy to access duringthe experimentation. However, the pressure relief valves in the hydraulic circuit wasset at 20 bar for safety.The motor speed also played important role in keeping the system at steady state. Thisis obviously because the motor speed is directly proportional to the mass flow rate ofthe oil in the system. If the mass flow rate of the oil is less then the temperature losswould be high when the oil travels one complete cycle through the system. If the motorspeed is high then it would cause the turbulence within the system which will causethe bubble formation. It may also affect the sudden pressure rise in the system that

26

can be catastrophic for the rig. The motor speed of 555 RPM was hence decided onthe basis of the experience with the working with rig while test the rig itself.

3.3 Methodology Stage 1

As explained in the introduction section, this stage is to define the limits of pressureand temperature. This is done according to table 2. This test is done in two ways.First with one seal in the chamber and second with three seals. These tests are donein a different way than the preliminary test. In stage one tests, the temperature andpressure values are changed step by step to study the effect of pressure and temperaturevalues on oil behaviour. Transition time in table 8 is time required for the oil to changeits steady state temperature from value to another. Also, the pressure also changedas during the transition time due to temperature increment. Hence, it was necessaryto monitor the pressure using inbuilt pressure relief valve in pressure hand pump.The allowable change in pressure during transition was from 0.5 bar to 16 bar. Thisindirectly proved advantageous since it was possible to inspect varying pressure withrespect to relatively slow rise in oil temperature giving the initial idea of relationaleffects of pressure and temperature. This makes it easy to decide on the maximum andminimum values of temperature and pressure. The RPM as decided is kept constantand also all the other parameters are tried to kept constant so that the reliability ofvalues obtained from experiments on pressure and temperature are more. The resultsare shown in table 8 and table 9.In this test as shown in table 8, only one seal is used or only one roughness combinationwas tested. This is done to reduce the complexity of the testing during the initial test.It also helps to understand the behaviour of oil at different temperature and pressure.

27

Table 8: Methodology Stage 1 test with Single Seal

Temperature Pressure Motor Speed Time (mins) Transition Time

(◦C) (Bar) (RPM) 5 10 15 20 25 30 (min)

20 4 555 3 3 3 3 3 3

30 5 555 3 3 3 3 3 3 20

40 6 555 3 3 3 3 3 3 22

50 7 555 3 3 3 3 3 3 22

60 8 555 3 3 3 3 3 3 30

70 9 555 3 3 3 3 3 3 42

80 10 555 3 3 3 3 3 m 37

90 11 555 m m m m m m 40

100 12 555 m m m m m m 40

110 13 555 m m m m m m 43

120 14 555 m m m m m m 70

130 15 555 7 7 7 7 7 7 90

140 16 555 7 7 7 7 7 7 90

28

Tab

le9:

Met

hodol

ogy

Sta

ge1

test

wit

h3

seal

s

Tem

pera

ture

Pre

ssure

Moto

rSp

eed

R1

Tim

e(m

ins)

R2

Tim

e(m

ins)

R3

Tim

e(m

ins)

(◦C

)(B

ar)

(RP

M)

510

1520

2530

510

1520

2530

510

1520

2530

204

555

33

33

33

33

33

33

33

33

33

305

555

33

33

33

33

33

33

33

33

33

406

555

33

33

33

33

33

33

33

33

33

507

555

33

33

33

33

33

33

33

33

33

608

555

33

33

33

33

33

33

33

33

33

709

555

33

33

mm

33

33

33

33

33

33

8010

555

mm

mm

mm

33

33

33

33

33

33

9011

555

mm

mm

mm

33

33

33

33

33

33

100

1255

5m

mm

mm

mm

mm

mm

m3

33

33

3

110

1355

5m

mm

mm

mm

mm

mm

m3

33

mm

m

120

1455

57

77

77

77

77

77

7m

mm

mm

m

130

1555

57

77

77

77

77

77

77

77

77

7

140

1655

57

77

77

77

77

77

77

77

77

7

29

In this test as shown in table 9, the metal plates are included and consequently 3seals are also added. In this test, 3 roughness surfaces are inspected simultaneously(R1,R2,R3). The points at which each surface shows difference in behaviour is noteddown. This helps in finding out leakage surfaces at different surfaces in the same testand also helps in saving time. This experimental gave the initial idea of some kindof patterns in the leakages through the gasket which is discussed in later section 4.2.This proved advantageous since this was the first testing method in this thesis wherethe estimation of leakage and its characteristics like size of bubble formation etc canbe studied.Single Component Silicone was used till these tests to seal the gap between the cutseals. These seals take 3 to 4 days to cure and also it bursts when the rig operates athigh temperature and pressures. In order to avoid these issues, a remedy was takenbefore the final and important test stage. A 2 component silicone was used laterinstead of single component silicone which reduced the curing time and also lasted forlong. This accelerated the testing frequency. Each test is repeated twice to find therepeatability. After close analysis of the behaviour of seal at different conditions, thelimits are decided for pressure and temperature which is shown in Table 10.

Table 10: Limits of Temperature and Pressure

Temperature (◦C) Pressure (Bar)

Low High Low High

80 110 2 3

30

3.4 Methodology Stage 2

The Design of Experiments is conducted in this stage. The limits of pressure andtemperature obtained from Methodology Stage 1 is used here. The experiments areconducted according to the table shown in Section 1.5.3. The + and - symbols used intable are the maximum and minimum values of each parameter. The values of otherparameters are decided from the requirement specifications. These values are shownin Table 11. These values are changed accordingly to the design of experiments.

Table 11: Maximum and Minimum Limits

Parameter + -

Pressure 3 2

Temperature 110 80

ClampingTorque

30 Nm 20 Nm

Bolt Distance 138 mm 69 mm

Out of 16 tests conducted, the result for the crucial conditions which are all maximumvalues except clamping torque is shown in table 12. The results obtained from theMethodology Stage 2 gives an idea of how oil shows leaking property with the combinedeffects of all the parameter. These leaking surfaces are noted down and studied infurther to learn how the surfaces parameters affect leakage.

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Table 12: Methodology Stage 2 - Critical Conditions

Temperature Pressure TimeBolt

DistanceClamping

TorqueR1 R2 R3

(◦C) (Bar) (hr) mm Nm

110 2 0.5 138 20 3 3 3

110 2 1 138 20 m 3 3

110 2 1.5 138 20 m 3 3

110 2 2 138 20 m 3 3

110 2 2.5 138 20 7 3 3

110 2 3 138 20 7 3 3

110 2 3.5 138 20 7 3 3

110 2 4 138 20 7 3 3

110 2 8 138 20 7 m 3

110 2 8.5 138 20 7 m 3

110 2 9 138 20 7 7 3

110 3 25 138 20 7 7 3

110 3 26 138 20 7 7 3

110 3 27 138 20 7 7 3

110 3 28 138 20 7 7 7

110 3 36 138 20 7 7 7

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3.5 Auxiliary Experimental Tests

After conducting all the tests till now it was also essential to check the behaviour ofsurface roughness with the oil (10W40) which is used in real applications in trucks.So this test was the last test where the test parameters are in Table 13. The mainobjective for this experiment is to see if the viscosity of the oil plays an important rolewhile leaking through rubber. All the earlier tests were done on less viscous oil (5W20)just to get more leaking patterns at lower values of pressures and temperatures.

Table 13: Testing with Scania Oil - 10W 40

Temperature Pressure DayBolt

DistanceClamping

TorqueR1 R2 R3

(◦C) (Bar) mm Nm

110 2 1 138 20 3 3 3

110 3 2 138 20 m 3 3

110 4 3 138 20 m m 3

110 6 4 138 20 7 m 3

110 9 5 138 20 7 m 3

This test is done for 5 continuous days with no interruptions. The pressure isvaried after each day to accelerate the leaking and also keeping an aim for checking theextreme limits of pressure the seal can work fine. The result also gives an idea of howthe viscosity of oil behaves at each temperature and how it affects leakage at differentroughness surface which are discussed in results and discussion section.

3.6 Tracking of Leakage

This is the most crucial and sensitive part to find the leaking area or defected area.In-case of Mild steel plate, it was easy to track down leaking path because of heated oilstains that were left behind as previously shown in figure 12. But in-case of aluminumno post oil stains were found, hence it was difficult to find leaking paths. Initially,from test results the overall estimated area of leakage was deduced. This area wascritically inspected under the zoom camera using Optiv 321GLtp as shown in figure12a. If some unusual patterns are observed under the camera it was immediatelycheck using portable surface measurement machine as shown in figure 11. Inspectionof profiles were conducted by checking the same profile area twice or thrice to see ifwe some irregularities are observed. If some possible irregularities are observed then

33

it was thoroughly checked under 3D plotting machine 13. Since the inbuilt softwarewas not available on other computer thus it was exported into Matlab to rotate, panand examine 3D surfaces. The validation of leaked surface can be done by comparingthe roughness parameters of leaked surface to parameters of non leaked surface. Thedifferences can be found out by observing the surface profile for both leaked and nonleaked surfaces. More about this will be discussed in Result and Discussion Section 4.

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4 Result and Discussions

4.1 Results from Experiments

During the experiments, leakages were duly noted and the surfaces where taken intostudy. Out of all the tests conducted, the leaking spot was seen common in AluminumPlate and Metal Plate. The results obtained after each stages are explained below.

4.1.1 Preliminary Experiments

The Preliminary Experiment is conducted with just one seal. Which means it has thealuminum top plate, seal in between and the metal bottom chamber. The aluminumplate has a roughness which is Rz 5 µm and metal plate has roughness Rz value 20 µm.Throughout the experiment conducted,the surfaces was in constant observation usingUV light. The line formation was found at a particular spot in metal chamber whichwas repeating in 3 continuous tests. The surface was then noted down. It came intonotice that the surface has cross milling operation done which is different from the restsurface which is straight milling. The image of that is shown in Figure 21. The lineformation outside the cross milled surface is formed after 90 ◦C and 3 bar of pressurewhich can be seen in Table 6

Figure 21: 1. Whole milled surface 2. Cross milled surface

This test is also for inspecting every components was working fine and also to helpin understanding more about how the rig behaves at different conditions. This studymade it easy in later tests to make the fluid system steady in less time.

4.1.2 Methodology Stage 1

• Methodology Stage 1 with single seal

As mentioned before, it was necessary to specify the values of pressure and tem-perature for next stage of methodology. So this was the preliminary testing for

35

methodology 1 just with one seal. From table 8, it is evident that the line forma-tion from the R1 surface at 80 ◦C and pressures at around 10 bar at 25 mins afterthe system attained steady state at 80 ◦C. The line formation continued until 120◦C. But when the temperature attained its steady state at 130 ◦C and pressureat 14 bar, the bubble formation as observed. Total 3 repeating tests were carriedout with this type of testing. One test failed due to silicon burst at 130 ◦C and14 bar. Rest of the two tests one leakage was found at same place as found inpreliminary testings. The leakage area can be seen in figure 21.Even though, itwas not advisable to take the rig at 140 ◦C from preliminary test experience, butconstant monitoring was kept during this temperature ranges in order to avoidcatastrophe.

• Methodology Stage 1 with three seals

During this as mentioned all 3 surfaces were tested at time. There were 3 suc-cessful tests carried out. The new silicon type (Two Component) was introducedwhich reduced the curing time drastically and gave promising results at very hightemperatures and pressures within the scope of thesis. Hence it was possible totest the gaskets at 140 ◦C and 16 bar pressures. From table 9 it can be observedthat which surface leaked at what pressures and temperatures and at what timeafter the circulation of oil has reached a steady state.

Surface number Temperature (◦C) Pressure (bar)Average time toleakage (hh:mm)

R1 70 9 2:36

R2 100 12 3:33

R3 110 13 6:11

Table 14: Line formation pressure temperature and time relations

Table 14 shows the average time from the start of the test including steady stateand transition time between moving from one temperatures to other.

4.1.3 Methodology Stage 2

As mentioned before in Section 1.5.3 and table 3 using design of experiments in totalof 16 experimentation were needed to be done. But out of these 16 test the mostextreme tests were test no 9 and test number 10. In case of test nine it can be alsothe extreme test since this combination had maximum pressure, temperature and boltdistance but less clamping torque. Refer table 11 for maximum and minimum valuesof these parameters. While in test number 10 only the pressure was at minimum value.

36

Test number 10 was also important since effect of pressure at high temperatures canalso be studied.The table 12 shows the results for test number 10 and 9. The total duration for thecombined test 10 and 9 was set as 36 hours. It took almost three hours to reachthe steady state. When steady state was achieved the roughest surface leaked firstafter 1 hour. The surface R2 surface showed thin line formation after 8 hours but aftersometime that line vanished and re appeared for two times and was never visible again.But the smoothest surface or surface R3 didn’t showed and leakage during test number10. But when the rig set to conduct the test 9, where only the pressure was set toits maximum at 3 bar, minute bubbles were observed at the surface R3 after 28 hourswhen it reached its steady state. The bubbles were quite small and continued to burstout until the end of the test.

4.1.4 Auxiliary Tests

The tests done till now is with the oil grade (5W20). Scania uses oil of grade (10W40).These tests would obviously show different results. This test is done to inspect this.Scania oil is used to do the same methodology stage 2 test. The critical conditions wereapplied to the system and conducted the experiments. This experiments were explainedin section 3.5. The test showed promising results. It was noted that the surfaces R2and R3 showed the same leaking behaviour as the other oil. The interesting fact foundwas that surface R1 dint show any leaking property with this oil. This shows thatviscosity of oil does have a predominating influence in oil leakage at particular surface.

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4.2 Results from Analysis and 3D Plots

• AluminumFigures 22 and 23 shows the 3D plots of leaked and non-leaked surfaces in alu-minium plate. This is done in Matlab. The non-leaked surface is selected fromthe same plane to the leaked one. The leaked surface shows a different lay patternas compared to the non-leaked pattern. It is clearly evident that the cross-millingpattern can create a different path for oil to travel. These 3-D plots are of 2.5x 4 mm size which are not possible to see by naked eyes. These values are plot-ted from the inputs from Zygo machine as explained in section 2. The variousroughness parameters of the both leaked and non leaked 3D profiles at differentsections (400 microns, 650 microns, 900 microns) are studied and comparisonbetween leaked and non-leaked surface is studied. The abbot curve and its pa-rameters are shown in Figure 25. Figure 24 shows the comparison of Rz valuesof leaked and non-leaked surfaces. It can be seen that the values are almost thesame throughout every section considered. Figure 25 shows the comparison ofabbot curve for leaked and non-leaked at different surfaces. The differences canbe noted from the figure.

Figure 22: Leaked Aluminum Surface

38

Figure 23: Non-Leaked Aluminum Surface

Figure 24: Roughness Parameters

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Fig

ure

25:

Lea

ked

VS

Non

Lea

ked

Surf

ace

40

Figure 26: Reduced Peak Height and Reduced Valley Depth

Figure 26 shows the comparison of Rpk values at 3 different sections and Rvkvalues at 3 different sections. It can be seen that the leaked surface parametersdiffers drastically at each plane sections while the non- leaked surface parametersbe in the same range. Figure 27 shows the material ratios MR1 and MR2 at eachsections. The same trend can be observed.

Figure 27: Material Ratios

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Figure 28: Rpk to Rvk ratio

Figures 28 and 29 represents the ratio of Rpk to Rvk at each section and A1and A2 at each sections respectively. The variations of each values at differentsections can be evidently seen. The non leaked surfaces shows uniformity inparameter values while the leaked surface does not.

Figure 29: Peak and Valley Areas

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• Mild Steel

Figure 30: Leaked Mild Steel Surface

The figure 30 and figure 31 shows the leaked and non leaked 3D plots respectively.For this three sections at taken for examination from the width side of the plot,i.e. at 1500 µm 1700 µm and 1900 µm. Those disturbances or white spotsbecause of oil stains. Since the oil stains are in black in colour and Zygo or 3Dplotting machine is optical measurement machine, it has issues when scannedtest surface has black colour because of high absorptivity index of surface. Thefigure 33 shows the difference between the leaked (red) and non leaked profile(blue). It is important to note that the leakage was only found the oil gradeof 5W20 was used. But when the original Scania oil (10W40) was used even atconsiderable high pressures this surface did not leaked. Here viscosity of oil mighthave important role. When observed closely in figure 33, the lay of both surfacesis same, but the leakage when used 5W20 grade is caused through the scratchescaused due to handling, which can be also one factor for damaging the surfaceand ultimately the leakage. Those scratches can also be observed via naked eyesfigure 30 somewhere between 500 µm and 2000 µm from the length side or Oilside.

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Figure 31: Non-Leaked Mild Steel Surface

The figure 32 shows the basic roughness parameters that Scania currently usesduring its manufacturing processes. When compared these parameters it seemsthat the Rz and Rz max at every section for both the leak and non leaked surfacescomes in same range. Hence in some case these parameters are not effective todefine if the surface would leak or not. But due to scratches Rz values of leakedsurfaces are higher than Rz values of Non leaked surfaces.

Figure 32: Roughness Parameters

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Fig

ure

33:

Lea

ked

VS

Non

Lea

ked

Surf

ace

45

Figure 34: Reduced Peak Height and Reduced Valley Depth

When observed the reduced peak height and reduced valley depth in figure 34,the values are almost same at three sections for same surface. But when observedclosely, valleys in surface plays an important role for leakages. It is hence alsoevident that the Rpk values at three sections for leaked surface is greater thatRpk values of respective three sections of non leaked surface. But when observedfigure 35 also gives almost same results.

Figure 35: Material Ratios

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Figure 36: Peak and Valley Areas

From figure 36 its can deduced that this surface is more dominated with peakssince values of A1 are much more higher than that of A2. This may also becauseof higher Rpk values as A1 is function of Rpk and Mr1. Similarly, figure 37 alsoshows the ratios of reduced values Rpk to Rvk and A1 to A2.

Figure 37: Reduced Values and Area Ratios

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5 Conclusions

In this thesis an extensive background study has been conducted and the purpose ofthe thesis has been completed. The study on how different surfaces behave when metalbounded gasket is placed has been studied very well. The requirement specificationsgiven from Scania is observed and accordingly plans has been made to test differentroughness surfaces under different conditions. However not all the conditions could beattained due to time limit. For example, an important criteria is vibration, which mighthave the capability of drastically changing the entire result has been removed from thescope of this thesis due to the time limit. The tests were conducted successfully andthe parametric relations were found. The following conclusions were made from thestudy.

• Rz value which is been used now in drawings are not sufficient enough to providea leak proof surface. For that Rpk, Rvk, A1, A2 values are needed to control theproblem. These values can be measured by using the machine used in shop floornow a days.

• The method of measurements has to controlled. The place where the rubber ispositioned on the surface has to noted and at least the parameters has to bestudied at 3 different positions and studied for the repeatability of values. Theparameters has to be in the same range. Basically the uniformity of the profilehas to be maintained throughout.

• Even mishandling of the component thereby causing even small scratches couldtrigger leaking behaviour in oil.

• It is also evident that the smoothest surface R3 has most promised surface againstleakage when vibrations are neglected in the system. When the profile for nonleaked MS plate or surface R3 observed closely the surface is quite peaks domi-nated which can prove advantageous since the leakages are caused mainly throughthe valleys of the surface profile. Same trend can also be seen in non leaked pro-file for Aluminum. Hence one point can be made that Rp must be greater thanRv, but these values cannot be enough was well. Hence, Rpk and Rvk can playimportant role since it covers majority of peaks and valleys respectively. Fromthe figure 33 and 25 Rpk and Rvk values are also mentioned. From these values itcan be observed that Rpk is comparatively greater than Rvk. But the differencebetween Rpk and Rvk must not be more at every section of measurement. Theserelations are given in the table 15.

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Table 15: Recommendations

Sr No Parameter Range

1 Rz 6-10

2 Rpk 2 - 5

3 Rvk Rpk/1.5

4 Mr1 1-15

5 Mr2 75-95

From all the experiences with experimentation it would naturally recommendedthat surface must be as smooth as possible. But keeping cost of manufacturing,it can be hence recommended range for Rz value from 6 - 10 µm. As mentionedbefore the difference between Rpk and Rvk must not be more, hence it can beseen that these two parameters can be constrained by using relation between Rpkand Rvk. It can given as:

Rvk = 0.67Rpk (1)

Where the range of Rvk can be set between 2-5. The material ratio 2 (Mr2)should be between 75-95 as shown in table 15, if Mr2 is greater than 90 percentsfor respective Rvk, the narrower valleys can be estimated. This may becomeharder for sealing rubber to seal such narrow and deep valley. Same may go withMr1. A1 and A2 will also change its characteristics since they the function ofRpk, Mr1 and Rvk, Mr2 respectively. One thing can be seen it smoother thesurface gets smaller becomes these areas.

• The method of milling the surface is also a factor which could affect the leakage.The surfaces with cross milled pattern and straight milled pattern within thesame component showed difference in behaviour. The cross milled eventuallylead to a reason for oil leakage. The profile along the sections showed differencein parameter values while the uniformity in pattern was maintained in straightmilled surface.

• In general, the roughest surface with R1 (Rz 20µm) leaked first in every testfollowed by R2 (Rz 10µm ) and R3 (Rz 5µm) respectively.

• As studied from the parameters of Aluminium Plate, the roughness of the surfacewas Rz 20µm and the parameters were showing large deviation in 3 planes in eachsection in leaked one compared to non leaked. The Rpk and Rvk values werefluctuating which could cause the rubber material not fitting in properly in the

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surface that caused leakage of oil. While at the same time, the mild steel platehas the smoothest surface of Rz 5µm which also showed leaking behaviour withless viscous oil. The peak and valley values were considerable the same whichmakes it difficult to analyze the reason for leakage. The only possible reason forthat is the scratch mark due to mishandling of the plate during manufacturingcaused a small disturbances in the surface which accelerated the leakage.

• In short as the surface gets smoother the complexity of leak proof surface param-eters increases.

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6 Future Work

There is always a possibility for future work. As mentioned before, the result would bemore promising to real case scenario if more parameters are included. One of the mostimportant factor to be considered is vibration between the seals. It could change theentire result till now. In this thesis a brief study on vibration is also done. A 3D modelof the possible modifications to be done when piezo electric actuator is added has alsobeen developed. The chamber is really stiff that a huge amount of energy is neededto get the desired displacement between the seals. For this the total model frequencyhas to be calculated and also the blocking force needed by the piezo actuator is alsoneeded. These are essential criteria for selecting a particular actuator. These detailshas also been calculated.Right now the chamber has metal bottom chamber and aluminum metal upper plate.These has limitations in tracking the oil leaking path. It would be easy if instead ofaluminum upper plate, manufacture a glass upper plate with desired roughness so thatit will be easy to track the oil leaking path. Other factor like the rubber material andhow it deforms at different load conditions and also its temperature behaviour is alsoa scope of future work.The robustness of different sealing concepts can tested. As the rig is good enoughto give engine conditions, the chamber models can be varied according to the sealingconcept and studied for its behaviour. Also the metal gasket used in this thesis is ashortened version of original one. The whole metal bounded rubber gasket can also beinspected.Oil stains were seen on the metal plate and not on the aluminum plate. This could bea result of some chemical deposition reaction. This can also be an additional study forfuture.The viscosity study for oil behaviour can also be done. As all know the viscositychanges at different temperatures. This could affect the leakage negatively. This is yetanother factor to be considered when studying leaking surfaces.

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7 Appendix

7.1 Gantt Chart

Figure 38: Gantt Chart 1

Figure 39: Gantt Chart 2

7.2 Work Breakdown Structure

Figure 40: WBS

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7.3 Risk Analysis

Table 16: Risk Analysis

Risk Probability Impact Planned Action

Delay in Testingdue faulty rig

Medium MediumContinuous evaluation

of the rig

Delays in Testingdue to Silicone issue

Medium HighMore dry time for silicone

and use of less silicone

Faulty Sensors Low MediumContinuous evaluation of the

connections and proper calibration

Design fault High HighProper design and

consulting Supervisor

Delay in delivering parts Medium MediumPlan ahead and

continuous tracking

Bolt Breakage Low High Replace Bolt

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8 Additional Figures

Figure 41: Line formation and bubbles formations

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References

[1] D J WhiteHouse ”Handbook of Surface Metrology”. Chapter 2,Page 7-202,Instituteof Physics Publishing.

[2] Scania ISO Standards STD SS-EN ISO 1302,STD SS-EN ISO 4287,STD SS-ENISO 4288,STD 4261

[3] Surface Measurment Manualhttps://docplayer.net/21013675-Form-talysurf-pgi-series.html

[4] U.Natarajan,S.Palani,B.Anandampilai Prediction of Surface Roughness in Millingby Machine Vision Using ANFIS. January 2014

[5] Ulf Olofsson,Yezhe Lyu Open System Tribology in the Wheel–Rail Contact— ALiterature ReviewS. [DOI: 10.1115/1.4038229] KTH Royal Institute of Technology

[6] ”Machine Design Integrated Approach”. Chapter 14, page 901-906.

[7] ”Engineering Analysis with ANSYS Software”. Page 49, 345

[8] Dr Saman Fernando ”MECHANISMS AND PREVENTION OF VIBRATIONLOOSENING IN BOLTED JOINTS”.

[9] Christophe Marie,Didier Lasseux Experimental Leak-Rate Measurement Through aStatic Metal Seal. [DOI: 10.1115/1.2734250]

[10] Yiping Shao,Yaxiang Yin,Shichang Du,Tangbin Xia,Lifeng Xi Leakage Monitor-ing in Static Sealing Interface Based on Three Dimensional Surface TopographyIndicator. [DOI: 10.1115/1.4040620]

[11] Jie Zhang,Jingxuan Xie Investigation of Static and Dynamic Seal Performancesof a Rubber O-Ring. [DOI: 10.1115/1.4038959]

[12] [Online] https://www.bergeng.com/mm5/downloads/mahr/

MarSurf--3750474--FL--Mobile_roughness_measuring_

instruments--EN--2017-09-07.pdf

[13] [Online] http://www.lakara.si/wp-content/uploads/2012/09/

datasheet-classic-321gltp-EN.pdf

[14] [Online] https://zeus.phys.uconn.edu/halld/diamonds/Zygo/MetroPro_

docs/

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