Integrating Simulated Loads with Measurements and Strength

Testing Dr. Henrik Wentzel

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Outline

• Problem description

• Current practise

• Challenges & future development

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

This talk is about choosing appropriate fatigue design loads

Design load

Customer load

?

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Heavy loads Poor roads

Hurried drivers Heavy duty

Verifying strength

Strength is verified on the test track, and ultimately by the customers.

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Designing for strength

Development requires sound engineering principles supported by FE-simulations using

limited geometry and simplified design loads

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Appropriate design loads

• A good design load:

– Fast to evaluate

– Easy to understand

– Appropriate

Examples: NCAP (Appropriate, Easy to understand, Fast is a relative term)

Allows for optimization

with FEA!

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Appropriate fatigue design loads

• No accepted standards, each OEM has unique methods.

• Examples: quasi static, random noise, harmonic, transient,…

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

This talk is about choosing appropriate fatigue design loads

Design load

Customer load

?

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Fatigue design loads are generated by:

• Measure loads on existing products.

• Simulate vehicles on the test track in the design phase.

• Use vehicle simulations to derive development loads.

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Static inverse force method (yesterday)

Physical Calibration

Measurement Design load FEA

optimization

εtest (t) εref =g·Pref Pdesign = g-1·εtest

Pdesign

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Pdesign

Design load used for optimization

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Simulating the static inverse force method

Unit load

εref =g·Pref

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Static inverse force method (today)

FEA Calibration Measurement Design load FEA

optimization

εtest (t) εref =g·Pref Pdesign = g-1·εtest

Pdesign Pref

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Simulating a vehicle on road is difficult

Major challenges:

• Model assembly

• Tyre modelling

• Suspension modelling

Low quality design loads suboptimization

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Measuring the design load is difficult

• Many interface forces can not be measured, for example the forces through the cabin suspension.

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Dynamic inverse force method (today) FEA Calibration Measurement Design load

atest (t) aref =g·Pref Pdesign = g-1·atest

Pref

aref

Pref

The design forces are the forces that give measured response.

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Dynamic inverse force method (today)

In the simulation model it is easy to measure the interface forces in the cabin

suspension.

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Future trend/possibility - sensors

• Today 6 accelerometers on every vehicle.

• Manual download.

• Trend (internetification): Lots of low quality data

Downloading a Scania

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Future: sensors-models-loads

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Measure usage

Dynamic inverse methods

Measure interface loads

Pdesign

Optimize

Challenge – vehicle models

• Model assembly is a bottleneck.

• Stress-evaluation of truck 107 nodes.

• Managing such a model in the preprocessor.

• Integration between MBD and FEA

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014

Future work

• lots of low quality data

• high quality models

• integration between MBD and FEA

Develop new practices for specifying the design

load based on:

Recognizing that some users may still

subject the vehicle to unforseen loads…

2014-06-26 Info class Public, RTCC/Hwentzel/ATC2014