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DATA GATHERING(for engineering research)

MOHD NASIR BIN TAMIN(Ph.D. Mechanical Engineering and Applied Mechanics)

ProfessorDepartment of Applied Mechanics and Design

Faculty of Mechanical Engineering, UTM

ULP 0010 - Research Methodology

8th November 2014

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Mohd Nasir TAMINPh.D. Mechanical Engineering and Applied Mechanics, 1996 (USA)Professor, CEngDepartment of Applied Mechanics and Design, Faculty of Mech. Engng., UTMHead, Computational Solid Mechanics Laboratory

Some Research and Engineering Consultation:Fatigue damage mechanisms in SiC/Ti MMCFatigue characterization of TiAl intermetallic alloysFatigue life prediction of NGV compressor componentsReliability stress analysis on solder interconnects and TSVsFailure analysis of machine component and structures

Courses delivered:Mechanics of materialsFinite element methodFailure of engineering components and structuresFatigue and fracture mechanicsMaterials engineeringApplied Numerical MethodsAdvanced materials

BRIEF CV

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RESEARCH – a process

Identify researcharea

Literature review

ProblemIdentification

TheoreticalFramework

MethodologyResearch Design

Data Collection & Analysis

Conclusions

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A COURSE ON RESEARCH METHODOLOGY- A Typical Outline

Philosophy and Overview of Research Literature Review Problem Formulation Research Design Data Gathering, Instrumentation and Measurement Sampling Techniques of Data Analysis Academic Writing Thesis Presentation

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OBJECTIVES

To describe issues related to the working principles of devices associated with instrumentation.

To illustrate the principles and procedures involved in sampling and measuring physical quantities.

To identify methods and techniques in gatheringexperimental data.

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Prerequisite to data gathering

To review general considerations in the analysis of experimental data.

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Following data gathering…ROADMAP OF DATA ANALYSIS

MEASURED DATA

Curve-fitting

Numerical & Analytical

Models

(Extract model Parameters)

Verification & Validation

Reliability Analysis

Physical Aspects

Information / Knowledge

(Interpret & Establish)

(Comparative Study)

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TYPES OF DATA Generated data

Measured data Single reading

Random measurements

Time-dependent data

Others (micrographs)

Composition of steel (wt. %)

Introduction

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NATURE OF MEASURED DATA

Consistency

Uncertainty

Scatter

Outliers

Trends

Physical-based content

Evolution / history

Introduction

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CONSIDERATIONS IN DATA ANALYSIS Anticipate the results from theory

Examine the data for consistency

Reduce the data

Perform a statistical analysis of data where appropriate

Estimate the uncertainties in the results

Correlate the data

Interpret and extract information

Introduction

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Data Gathering InstrumentationMeasurement Sampling

OUTLINE

Servo-hydraulic universal testing machine with furnace for high-temperature test.

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DATA GATHERING (EXPERIMENTAL)

Activities of acquiring (measuring, observing, surveying) physical quantities of selected samples employing specific technique and instrument.

Collecting published information and data.

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Material: AISI 4340 SteelEXAMPLE 1 - MECHANICAL (TENSION) TEST

P

P

Lo+LLo

Ao

Elongation, L (in.)

Load

, P(lb

f)

THE SAMPLE

THE MACHINE / INSTRUMENT

THE MEASUREMENTS

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DATA GATHERING (EXPERIMENTAL)

WHAT is the data.

HOW to collect the data Direct measurement Observation / Survey Published data / Database

WHEN to collect data / measure

WHY need data collection.

WHERE data gathering is to be performed.

- SAMPLING

- INSTRUMENTATION

- MEASUREMENT

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OBJECTIVE

To determine the hardness number for a material by measurements of surface indention

Force

Indenter

SampleIndentation

EXAMPLE 2 – INDENTATION HARDNESS TEST

Data Gathering InstrumentationMeasurement Sampling

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INSTRUMENTATION

Micro-hardness tester

Working/ Test Principle

Machine/ System Characteristics

Calibration

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TEST PRINCIPLEHardness is determined by forcing a hardened indentor under a known load into the surface of a material and measuring the size of the indentation left after the test.

Select a suitable indentor

eg. 10-mm sphere

Apply known force(1 to 1000g)

Measure size of indentafter load removal

dDSmaller indent reflectsgreater hardness

2d2D-DDπ

P2BHN

BRINELL HARDNESS TEST

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Square-Based Diamond Pyramid d1

d2

HV = 1854.4L/d2

L is the load in gfd is the mean diagonal in µm

VICKERS HARDNESS TEST

TEST PRINCIPLE (Cont.)

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MACHINE / SYSTEM CHARACTERISTICS

Sensitivity Resolution Range Response Zero-setting Shake-downAutomatic features Repeatability and Reproducibility SAFETY

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DESIGN OF MEASURING SYSTEM

Sensitivity, S The change in output signal relative to the

change in input signal at an operating point k.

Resolution, R The smallest change in the input signal

that will yield an interpretable change in the output of the measuring device

Example: Resistance-based thermometerR() T(oC)307 200314 230321 260

kp

p

kIp

p

ΔI dIdO

ΔIΔO

Sp

p

0

lim

divisionscaleS

R 11

CΩ/.dIdO

S o

kp

p 2330200230307314

To ensure accuracy of measured quantity, sensitivity, resolution, range andresponse of the measuring device or system must be known.

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Range The maximum and minimum measurements that can be detected

by a measuring device.( Example: The range of a thermometer is between -10 oC to 110 oC.

The span is 120 oC)

Response The time taken by a measuring device to generate a signal to the

designed (uniform) level after receiving an input.

UNDERSTAND THE CHARACTERISTICS AND WORKING PRINCIPLES OF ALL MEASURING DEVICES / SYSTEMS USED.

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SENSITIVITY

When a small increment of input (excitation) causes a large change in the response (read-out) of the instrument.

Terikan

0.0 0.1 0.2 0.3 0.4 0.5

Tega

san

( MPa

)

0

200

400

600

Ujikaji AUjikaji B

E = 200x103 MPaRequires sensitive strain measuring device

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440C at 62.7 HRC

BUILT-IN SYSTEM RESPONSE

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REPEATABILITY(Hardness Test)

For each standardized block, let d1, d2 ..., d5 be the diagonal lengths of the indentations, arranged in increasing order of magnitude.

The repeatability of the machine is expressed by the quantity (d5 - d1)/ davg, where davg is the average of d1to d5.

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REPEATABILITY

Ability of the measuring instrument to produce identical readings repeatedly.

Hardness Test

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Universal testing machine

Specimen

Load cell

Specimen grips

Crosshead

Data acquisition system

Extensometer

ZERO-SETTING

FORCE DISP.

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SHAKE-DOWN

Application of repetitive small load magnitude to set-in the load train and avoid lag or back-lash.

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AUTOMATIC FEATURES

On-line data processing software provides a quick glance of the quality of collected test data.

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SAFETY

The operator (YOU) People around test set-up Machine and devices

Adopted from W. Wood, McGill University

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CALIBRATION

Setting/ tuning of measuring devices so as to output actual/ true quantity being measured.

Extensometer calibration curve for Instron 4206+8801Gauge Length = 25 mm

Travel Length = 12.5 mm22-02-2006

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45Measured Strain (mm/mm) [readings from console/PC]

App

lied

Stra

in (m

m/m

m) [

Rea

ding

s fr

om m

icro

met

er]

MeasuredStrain (Instron 8801)

MeasuredStrain (Instron 4206)

Measured quantity

True

/ ref

eren

ced

quan

tity

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What and How to measure

How many measurements are sufficient

Accuracy, Precision and Bias

Uncertainty

Error

MEASUREMENT

Data Gathering InstrumentationMeasurement Sampling

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Square-Based Diamond Pyramid d1

d2

HV = 1854.4L/d2

L is the load in gfd is the mean diagonal in µm

MEASUREMENT – VICKERS HARDNESS, HV

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HOW TO MEASURE

(MEASUREMENT OF LENGTH)

Learn how to read vernier sacles, dial gages and estimate of uncertainties.

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Near SurfaceMicrocracks

Case Structure Core

2% Nital

Flame Hardened 8660 Gear

FREQUENCY OF DATA COLLECTION

How many Hardness measurements are sufficient?

Depth

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Automated MHT HV Traverse

Flame Hardened 8660 Alloy Steel Gear

FREQUENCY OF DATA COLLECTION

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Accuracy – the degree to which the measurements deviate from the true value.

Precision – ability to give multiple estimates that are near to each other.

Bias - a systematic deviation of values from the true value.

Accuracy

Precision

ACCURACY, PRECISION AND BIAS

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Instrument Factors

(Hardness Test)

Accuracy of applied load Inertia effects, speed of loading Lateral indenter movement Indentation time Indenter shape deviations Damage to the indenter (plus films) Insufficient spacing between indents and from edges

FACTORS AFFECTING PRECISION AND BIAS

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Measurement Factors

(Hardness Test)

Calibration of measurement system Resolution of the opticsMagnification Operator bias in sizing indents Inadequate image quality Non-uniform illumination

FACTORS AFFECTING PRECISION AND BIAS

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Material (Specimen) Factors

(Hardness Test)

Heterogeneity in composition and microstructure Crystallographic texture Quality of specimen preparation Low reflectivity or transparency

FACTORS AFFECTING PRECISION AND BIAS

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UNCERTAINTY ESTIMATION

Report: Pressure, p = 100 kN/m2 ± 1 kN/m2

For a set of n experimental measurements {x1, x2, x3,…,xn}with uncertainty {w1, w2, w3,…,wn}

The uncertainty, wR, in the desired result, R = R(x1, x2, x3,…,xn) is

2/122

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2

11

...

nn

R wxRw

xRw

xRw

Ref: Kline, S.J. and F.A. McClintock, “Describing Uncertainties in Single-Sample Experiment”, Mech. Eng., pp. 3, Jan. 1953

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Example 3:

The resistance of a certain size of copper wire is given as:

R = Ro [1 + (T – 20)]

Where Ro = 6 ± 0.3 pct. at 20 oC = 0.004 /oC ± 1 pct.T = 30 oC ± 1 oC

Calculate the resistance of the wire and its uncertainty

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Solution 3:Nominal value of the resistance:

R = Ro [1 + (T – 20)] = 6 [1 + (0.004) (30 – 20)] = 6.24 Uncertainties:

= 1 + (T – 20) = 1 + (0.004) (30-20) = 1.04

= Ro (T-20) = 6 (30-20) = 60

= Ro = 6 (0.004) = 0,024

oRR

R

oRR

wRo = 6 (0.003) = 0.018

w = (0.004) (0.01) = 4x10-5 /oC

wT = 1 oC

wR = [(1.04)2 (0.018)2 + (60)2 (4x10-5)2 + (0.024)2 (1)2 ]1/2 = 0.0305 or 0.49 pct.

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ERROR(Hardness Test)

• The error of the machine is expressed by the quantity dstd - davg, where davg is the average of the indentation diagonals and dstd is the value provided on the test block certification.

• The average observed diagonal shall not differ from the certificate diagonal by more than 2% or 0.5 mm, whichever is greater.

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INACCURACY OF MEASUREMENTS

Instrument Calibration

Instrument Reproducibility

Measuring arrangement

Work piece

Environmental Conditions

Observer’s Skill

The purpose of measurements is to describe some physical properties of an object / material / system quantitatively

Sources of Error

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SCATTER OF MEASURED DATA

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Stress-Life (S-N) Curve

Wrought steel

Dealing with inherently large scatter in the measured quantity

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SAMPLING DESIGN

Materials:• Virgin• Retired

Location of cut for retired samples

Direction of cutfor specimen

Shape, size and numberof specimens

Example 4:

Creep-fatigue interaction effects on high-strength steels

Data Gathering InstrumentationMeasurement Sampling

Ref. : ASTM E370

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STATISTICAL CONSIDERATION

Influence of the distribution of variables

(e.g. Stress and strength, household expenditure and income)

Pf = P( Stress Strength)

R = 1 - Pf

QUALITY versus

RELIABILITY

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SAMPLING PROCEDURES

Unrestricted Random SamplingRandom sample selection from the population as a whole.

Stratified Random SamplingPartition the population into known meaningful strata. Random selection is made within each stratum, making sure all strata are represented.

Optimum-allocation-of-strata Random SamplingIf information about the population strata and the way they will be used is available, optimum sample selection is made to give the most representative information about the population.

To obtain a representative sample with maximum randomness.

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FATIGUE TEST PROCEDURES

P, R = -1

Stre

ss

Time

Completely reversed axial fatigue

(This test is commonly done in reversed bending cycles)Raw data:

Stress(MPa)

Nf

(cycles)

1 pair of data per specimen

0

SAMPLING

How many test samples are sufficient?

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Fatig

ue s

treng

th, S

f(M

Pa)

300

400

500

600

800

1000

Cr-Mo steel, normalized

SUT = 800 MPa

Se = 338 MPa

Ref: Shigley, J.E., Mechanical Engineering Design, First Metric Edition, McGraw-Hill, 1986

Fatigue limit /

Endurance limit

Stress-Life (S-N) Curve

IDENTIFY THE DESIRED RESULTS

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Fatigue limit – tensile strength relationship

Adding to available published data

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REGRESSION / CURVE FITTING

Regression is a process used by statisticians to obtain a curve which best fit a set of data points.(But you are not a statistician!)

To plot curves of experimental data and extract various significant facts from these curves(Must understand physical phenomena involved in the experiment)

Correlation of experimental data is desired in terms of an analytical expression between variables that were measured in the experiment.

Requirements for a regression analysis

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Material: AISI 4340 SteelMECHANICAL (TENSION) TEST

P

P

Lo+LLo

Ao

Elongation, L (in.)

Load

, P(lb

f)

DEMO

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STRAIN,

0.0 0.1 0.2 0.3 0.4 0.5 0.6

STR

ESS,

(M

Pa)

0

200

400

600

800

Example 6 – Curve fitting

ALYAWS RELATE EXPERIMENTAL DATA TO THE PHYSICS OF THE PHENOMENON

STRAIN,

0.0000 0.0002 0.0004 0.0006 0.0008 0.0010ST

RES

S,

(MPa

)0

50

100

150

200

= ELinear

Non-linear /Power-law

= E

= K(p)n

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PLASTIC STRAIN, p

0.0 0.1 0.2 0.3 0.4 0.5 0.6

STR

ESS,

(M

Pa)

0

100

200

300

400

500

600

700

PLASTIC STRAIN, p

0.01 0.1 1

STR

ESS,

(M

Pa)

100

1000

= Kn

log K = 2.8735n = 0.1992r2 = 0.9772

199.03.747 p

ALYAWS RELATE EXPERIMENTAL DATA TO THE PHYSICS OF THE PHENOMENON

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Fatigue crack growth rate data for TiAl intermetallic alloyExample 8 – Physical Mechanisms

Indirect measurement of property

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Fatigue crack growth rate data for TiAl intermetallic alloy

Trends of measured / analyzed data

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Fatigue crack growth rate data for TiAl intermetallic alloy

We should be able to describe the physical mechanism of observed phenomenon

Gathering physical information

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• American Standard for Testing and Materials (ASTM)ASTM E139 – 00 Standard Test Method for Conducting Creep, Creep-Rupture,

and Stress-Rupture Tests of Metallic Materials

• International Standard (ISO)ISO 6892:1998(E) Metallic Materials – Tensile Testing at Ambient Temperature

• European Standard (EN), British Standard (BS)EN ISO 7500-2:1999 E Metallic Materials – Verification of Static Uniaxial Testing

Machines – Part 2: Tension Creep Testing Machines – Verification of the Applied Load

• Japanese Industrial Standard (JIS)JIS Z 2271:1999 (E) Method of Creep and Creep Rupture Test for Metallic Materials

• Malaysian Standard (MS)MS ISO 1352:1998 Steel – Torsional Stress Fatigue Testing

TESTING STANDARDS

STANDARDS AND GUIDELINES

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LEVEL OF EXACTNESS

DATA

INFORMATION

FACTS

KNOWLEDGE

Level of improvements in decision making

Leve

l of e

xact

ness

of

stat

istic

al m

odel

WISDOM

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Q & A SESSION