15. ROMAX Test Duty Cycle Generation for Drivetrain Systems

@ Copyright 2011

Test Duty Cycle Generation for Drivetrain

Systems

Dr Jamie Pears

@ Copyright 2011SHARING INNOVATION IN BEARING, GEARBOX AND DRIVELINE

About this Presentation

•

The Importance of Duty Cycles Definition

•

Duty Cycle processing -

3 methods in RomaxDesigner

•

Case Study

•

Demo…


The Importance of Duty Cycle Definition•

Targets for gearbox design:

o

Durability/Reliability

o

Packaging

o

Cost

o

Weight

o

Efficiency

o

Noise

o

Maintainability

o

Shift quality/refinement

o

…

•

Durability always ranks highly


The Importance of Duty Cycle Definition•

…. “time to failure”

means component/system “life”

•

….. the gearbox designer needs to predict this and results are substantially affected by the duty cycle definition

•

Conclusion: Getting the duty cycle correct is vitally important in any gearbox design project

Log (Number of Cycles)

Load

Gear Contact

Gear Bending

Change load (torque) by 20%, gear bending life changes by 5 times


The need for Duty Cycle Processing

•

For testing: to reduce the duration

for rig testing

o

Full in-service duty for a vehicle is 200,000 to 1m km

•

For design analysis: to reduce the number of loadcases

o

A full histogram has 50+ loadcases

for 6-16 ratios in a vehicle

•

Impact on gearbox (component durability) must be the same as original data (in-service loads) despite condensation


What is Duty Cycle Processing?

Duty Cycle

Duty Cycle

Component Damage

Prediction

Component Damage

Prediction

Rig TestingRig Testing

TestTest Raw DataRaw Data

Design IntentDesign Intent Historical/Estimated DataHistorical/Estimated Data System Damage

Prediction

System Damage

Prediction


Raw data to condensed Single load

case

Raw data to condensed Single load

case

Raw data to Multiple

load cases


load cases

Three methods of Duty Cycle Processing

Raw data to condensed

Accelerated loadcases

Raw data to condensed

Accelerated loadcases

Component Damage

Prediction

Component Damage

Prediction

System Damage

Prediction

System Damage

PredictionRig TestingRig Testing

Requirement:



Load Cases


Load Cases


time (s) gear clutch 1 / rpm

clutch 2 / rpm

engine speed /

rpm

clutch pressure

1 / bar

clutch pressure 2

/ bar

switch shift

active

oil sump temp / °C

throttle / %

wheel speed left

/ rpm

wheel speed right

/ rpm

output torque

left / Nm

output torque

right / Nm

total distance

/ km

1379.472 1 3968 2348.8 4096.6 3.8 4.6 0 80 100 285.99 284.667 1047.991 1028.884 13.9631379.474 1 3968 2361.6 4100.2 3.8 4.6 0 80 100 286.109 285.159 1045.698 1028.632 13.9631379.476 1 3968 2374.4 4103.8 3.8 4.6 0 80 100 286.228 285.651 1043.865 1027.878 13.9631379.478 1 3968 2387.2 4107.4 3.8 4.6 0 80 100 286.347 286.143 1040.197 1026.119 13.9631379.48 1 3968 2400 4111 3.8 4.6 0 80 100 286.465 286.635 1036.071 1023.102 13.963

1379.482 2 3968 2400 4113.4 3.8 4.6 1 80 100 286.177 286.465 1033.091 1020.588 13.9631379.484 2 3968 2400 4115.8 3.8 4.6 1 80 100 285.888 286.296 1028.965 1017.069 13.9631379.486 2 3968 2400 4118.2 3.8 4.6 1 80 100 285.6 286.126 1024.61 1013.298 13.9631379.488 2 3968 2400 4120.6 3.8 4.6 1 80 100 285.312 285.956 1018.421 1009.025 13.9631379.49 2 3968 2400 4123 3.8 4.6 1 80 100 285.023 285.787 1012.003 1002.238 13.963

1379.492 2 3968 2400 4124.6 3.8 4.79 1 80 100 285.091 285.736 1007.19 996.959 13.9631379.494 2 3968 2400 4126.2 3.8 4.98 1 80 100 285.159 285.685 1001.459 991.429 13.9631379.496 2 3968 2400 4127.8 3.8 5.17 1 80 100 285.227 285.634 995.5 985.647 13.9631379.498 2 3968 2400 4129.4 3.8 5.36 1 80 100 285.295 285.583 989.54 981.122 13.963

1379.5 2 3968 2400 4131 3.8 5.55 1 80 100 285.363 285.532 983.351 975.592 13.9631379.502 2 3968 2400 4134 3.8 5.55 1 80 100 285.685 285.498 977.162 971.319 13.9631379.504 2 3968 2400 4137 3.8 5.55 1 80 100 286.007 285.464 970.973 967.045 13.9631379.506 2 3968 2400 4140 3.8 5.55 1 80 100 286.33 285.43 966.159 962.269 13.9631379.508 2 3968 2400 4143 3.8 5.55 1 80 100 286.652 285.396 962.721 960.258 13.9631379.51 2 3968 2400 4146 3.8 5.55 1 80 100 286.974 285.363 958.595 957.241 13.963

1379.512 2 3968 2400 4148.4 3.8 5.55 1 80 100 286.991 285.634 956.074 955.985 13.963

1. Raw Data > Multiple LoadcasesRaw DataRaw Data Multiple

Loadcase

‘Bins’

Multiple Loadcase

‘Bins’

Typical test data –

instrumented vehicle (recorded @ 500 Hz):


1. Raw Data > Multiple Loadcases

•

Represents equal damage as the raw data for all components.

•

This is highly suited to assessing damage of many components where no one particular component is of interest or considered critical.

•

However, this relies on many load cases and can lead to long duty cycle times –

so not suitable for physical testing


Raw data to Single

Load Case

Raw data to Single

Load Case


2. Raw Data > Single Load Case

Raw DataRaw Data Chose Damage Type /Component

Chose Damage Type /Component

Equivalent Single Load Case

Equivalent Single Load Case

No of Cycles

Stre

ss

abcdefg

107%

Matched Component Damage

Matched Component Damage

Com

pone

nt

abcdefg

107%

Com

pone

nt

Raw Data Component Damages


Matched damage for individual component


2. Raw Data > Single Load CaseAssuming a continuous slope and no discontinuities in the S-N curve,

it is possible to calculate an equivalent reference torque

to predict component damages.

This gives the

same component damage, at a higher torque, for a reduced No of Cycles (i.e

duration).

The slope of the S-N curve is defined by the component type/damage type.

a

torqueSampletorqueReference

torquesampleatTimetorquerefatTime

Damage type

a

Gear bending

6.61

Gear contact

8.73

Ball bearing

3.00

Roller bearing

3.33

Tor

que

Number of cycles

Raw Data torque

Reference torque

a



Select ‘Generate single load case at a specified reference torque (Miner’s rules)

Specify a reference torque

Select either matching gear contact; gear bending; ball bearing or roller bearing damage. These define the exponent a

in the previous slide.

The load case must have a speed defined. Either specify a speed or use the mean speed of the recorded data


•

Produces one load case that represents the equivalent damage seen by a component.

•

This is suited to assessing the durability of a critical component, however calculated damage of other components in the system will be inaccurate

•

Typically leads to having one duty cycle for gears, one for ball

bearings, etc

•

Equivalent load is an approximation that can lead to severe distortion in life calculation results

o

Some people use Equivalent Loads to carry out initial component sizing, then full fatigue analysis using LDD later

o

Two methods will give different results, leading to re-work in the design process



Raw data to Condensed Accelerated Load Cases

Raw data to Condensed Accelerated Load Cases


3. Raw Data > Accelerated Duty Cycle

Matched Component Damages

Matched Component Damages

abcdefg

Com

pone

nt

Gear Bending

Gear Contact

Stre

ss

Bearings

Number of cycles

Raw DataRaw Data Chose Damage Types /Components

Chose Damage Types /Components

Equivalent Accelerated Duty Cycle

Equivalent Accelerated Duty Cycle

abcdefg

Com

pone

nt



250 hours 10 hours


3. Raw Data > Accelerated Duty Cycle•

Optimised algorithms developed to create a single, multiple-loadcase

duty cycle appropriate for all selected failure modes

•Damages in accelerated duty cycle exactly equivalent to that for

the original time history of loads

•Gives a test (accelerated) duty cycle that can be used for rig testing and/or RxD

analysis

•

Increased confidence that the test duty cycle properly represents road data


Three methods of Duty Cycle Processing


Case Study -

Accelerated Duty Cycle Condensation

Work Scope

o

Client (Major EU sports car manufacturer) provided a series of raw data files collated from instrumentation of one of their test vehicles

o

A series of driving profiles were replicated in the testing and included in data acquisition

o

This information was then upscaled

to represent the total operational life of the vehicle

o

Information was used for the detailed fatigue analysis of the transmission

o

Romax created an accelerated Duty Cycle, allowing shortened test

rig times, whilst still resulting in the same damages for both gear contact and bending, and bearings

o

Both Drive and Coast conditions were considered


Work Flow•

Measure time domain data in vehicle and create Histogram

•

Condense Histogram to an equivalent duty cycle with reduced total duration

-100 -50 0 50 100 150 200 250 3000

2

4

6

8

10x 10

4

Input torque (Nm)

Sam

ples

(1 s

ampl

e =

0.00

2 s)

Histogram of 4th gear input torque

Time signal from instrumentation

Distribution of speeds and torques per ratio

Histogram of loadcases for a given ratio


The Big Question

How did the component damage results compare between

the “Original”

data and the “Accelerated”

data?


Bearing Damage DC Comparison

•

Excellent correlation between bearing damages –

Original and Accelerated


Gear Contact Damage DC Comparison

05

101520253035404550

pinion 6N Pinion 4-5N Pinion 3N Gear 6N Gear 5N gear 4N gear 3N

Gea

r Con

tact

Dam

age

Gear

Gear Contact DC Damage Comparison

G1 Condensed Contact Damage Left G1 Contact Damage Lef t

•

Excellent correlation between gear damages –

Original and Accelerated

•

Accelerated Duty Cycle duration –

43% of the original test duty cycle being used


Conclusion•

Correct definition of the duty cycle is essential for a robust design process

•

Simplifications in duty cycle processing can lead to substantial

and damaging errors, possibly leading to over-

or under-design, or re-work, or in-service failures

•

Romax has developed a ground-breaking methodology for the creation of condensed duty cycle, that gives an accurate representation of in-

service loads for all failure modes

•

This methodology has been successfully demonstrated for a Major EU Sports Car Manufacturer


Romax Technology is the technology leader in the precision simulation and analysis of bearing, gearbox and driveline systems. In over 20 years of providing expert engineering services to the global vehicle, aerospace, marine, rail and wind energy industries, Romax created and refined Romax Designer, the world’s first object orientated engineering analysis software package. Today Romax Designer has evolved into the world’s most comprehensive whole-system simulation and analysis platform, enabling fast, high precision results in one seamless development environment.

Romax believes in excellence through collaborative research and development with leading wind turbine manufacturers and operators; vehicle manufacturers; gearbox and driveline manufacturers; gear and bearing manufacturers; and with certification, research and academic institutions. As an innovative specialist Romax adopts a partnership style with customers and industry players to facilitate knowledge transfer and integrated solutions. Headquartered in Nottingham, UK, Romax provides an award winning localised service through an extensive global network, with 12 offices located in the UK, France, USA, Korea, Japan, China and India.

UK Head OfficeT: +44 (0)115 951 8800E: [email protected]

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15. ROMAX Test Duty Cycle Generation for Drivetrain Systems

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