Testing of motor cars in South Africa - VDI R1.0 of motor cars in South Africa... · • Engineering Certification • Products • Manufacturing • Hydraulics – design & installation

Testing of passenger cars & light trucks in South Africa

Dr. Michiel Heyns Pr.Eng. & Cornél BothaT: +27 12 664-7604C: +27 82 [email protected]

Agenda

• Thank you for the opportunity to address members of the largest engineering association in Western Europe

• Topics– Background on Investmech– Background on automotive testing in SA– Mission profile driven full vehicle testing– Component testing– Test equipment– Test laboratories in SA

• Closure

6/8/2013 Solutions in Engineering 2

Investmech

• ISO 9001:2000 certified company• Head office:

– 8 Topaz Avenue, Lyttelton Manor X3, Centurion• Investmech test laboratory

– Factory 2, Kruger Avenue, Centurion• Investmech test laboratory

– SASOL Laboratory at the University of Pretoria


Investmech services


Business consulting• Business analysis• Plant & process optimization• Project management • Feasibility studies• Screening of project ideas• Product development • Financial analysis • Customer – suppliers analysis • Scenario planning and analyses • Portfolio analysis and

optimization of investment frontiers

• Operations management in the mining and automotive industries

• Courses– Financial decision making– Operations management– Project management

Mechanical engineering• Structural Integrity - Fatigue life

expectance/fracture mechanics• Durability testing • ROPS & FOPS • FEM • Design - manufacturing drawings • NVH• Engineering problem solving• Courses

– Fatigue– Fracture Mechanics– Vibration measurement and control– Structural integrity– Condition monitoring and condition-

based maintenance• Engineering Certification • Products• Manufacturing• Hydraulics – design & installation• Test rigs• HVAC design and specification

SA’s motor industry

• SA’s motor industry is global (www.southafrica.info)– Manufacture & export vehicles and components– Accounts for ~10% of SA’s manufacturing exports– Contributes ~7.5% to SA’s GDP– Employs ~36,000 people– Exports to 70 countries

• Japan – 29% x value of total exports• Australia – 20% x value of total exports• UK – 12% x value of total exports• US – 11% x value of total exports


SA Automotive Industry

• Challenges– Shorter time to market– Rapid technology development– Increase in quality– Cost reduction– Globalisation– Reduction of warranty expenses

• Major Portion is Unrecognized user environments that escape the quality system• Even if tests pass prescribed criteria, the test plan could not reflect the full customer

environment or full range of manufacturing variability– In this case quality-planning efforts are focused on verification and not validation

• SOLUTION?

– MISSION PROFILE DRIVEN DESIGN AND TESTING


SA customer

• Has a unique mission profile– Long distances through the Karoo– Bad roads and overloading

• Choose well known, established brands such as (www.southafrica.info):– Toyota, Volkswagen, Ford, Mazda, Nissan, Mercedes-Benz and BMW– These makes up for 80% x (new vehicle sales) in SA


Terminology

• Fatigue testing– To verify the relationship between stress range and number of cycles to failure– Normally cyclic loads– Compare against the S-N curve

• Reliability testing– Measure of unanticipated interruptions during customer use

• Represents interruptions during ownership– Goal: To maximize opportunities for observing unexpected failures – so they can be fixed

• The fewer the opportunities to observe unpredictable failures, the greater the chance that not testing to measure reliability– Takes precedence over durability

• Durability testing– Subset of a reliability test– Durability can be estimated from reliability – reliability cannot be estimated from durability– Duration of product ownership– Similar to reliability test except with opportunities to discover unscheduled interruptions minimized (intentionally or

unintentionally)• Endurance testing

– Test to confirm that the vehicle complies with its mission profile• Accelerated testing• NVH – Noise, Vibration & Harsness• Test acceleration vs. Program acceleration

– http://www.sae.org/servlets/pdEvent?OBJECT_TYPE=PDEventInfo&PAGE=getPDEventInfo&EVT_NAME=C0316


Reliability testing – statistics applied

• Reflects a true customer– If possible, use actual users in an actual environment

• In a laboratory, a reliability test shall reflect a true user customer• Shall reflect sample coming from a true production environment• Shall use random samples• Shall be validation test, not just a verification test


Life testing

Reliability test –random

samples tested under actual environment

Success testing Run to a bogey

Failure testing Run to failure

Durability test –Pre-qualified

samples tested under

simulated environment

Success testing Run to a bogey

Failure testing Run to failure

Test types

• Component testing– Tyres– Engines– Drive trains– Fuel tanks– Exhaust pipes – Thermal fatigue,– Springs– Shock absorbers – Characterization + Fatigue– Clutch discs and pressure plates– Lifting devices– Clutch pedals, etc.

• Full vehicle testing– Road: Fingerprinting, subjective evaluations– Laboratory: Accelerated durability

• Characterization– Stiffness, damping, resonance


Rim and Tyre tests


Tests carried out:• Axial fatigue• Radial fatigue• Energy absorption

Guidelines and StandardsETRTO – European Tire and Rim Technical OrganizationSAE

Endurance testingFirestoneContinental

http://www.conti‐online.com/generator/www/com/en/continental/fmf/themes/products/testing/cwl_6position_en.html

Other types of component testing and problem solving


Fuel tank hose pull off tests(AIDC, Kaymac)

Squeak elimination on leaf springs(Mercedes-Benz)

Rear window failure investigation

• Problem statement– Spontaneous catastrophic fracture of

vehicle rear window – even when parked in garage, etc.

• Failure mode(s)• Metallurgy

– Sulphide inclusions delays fracture– Also used to infer heat input at

contactor• Impact resistance


Glass is a viscosity fluid and does not posses a rigid crystalline structure – is therefore is sensitive to temperature


• Structural responses– Strain gauges and accelerations– Strains within acceptable limits

• Subtract surface residual compressive stress = 69 MPa (ASTM C1048-04, 2007)

• Temperature distribution and levels


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Principal stresses at measuring Position #1

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Minimum tensile strength, t 86MPa

Minimum compressive strength, c 963MPa

Modulus of elasticity, E 73GPa

Plain strain fracture toughness, K1C 3.71MPa.m0.5

Density, 2,504kg/m3

Poisson’s ratio, 0.22

Typical mechanical properties of tempered automotive glass



Photo-elastic (polarization) results indicated on no problems with tempering process. However, in critical areas the edge residual stress was below the required compression stress of 66.9 MPa

A heat treated glass will break if the compression layer is penetrated

Fringe order (N) & colourused for residual stress

N=1.5

N=1.0

Re-design of load box

Measure strain and acceleration responses

Define mission profile

Quantify structural inputs on FEA

Re‐design for conformance

Also:Nissan load box re-designIsuzu load box redesignEtc.

Strain gauge mounted on the inside of an LDV load box

Failures:Maize testingSheep railsOver speeding whilst overloaded on bad gravel loads

Do not develop a vehicle without a proper mission profile

Vehicles were manufactured without mission profile and fatigue design. Severe cracking occurred before 10,000km.

Welds in the chassis cracked

Bullbar brackets cracked

Vehicle modified to carry vault and seating for armed guardVehicle driven in off-road conditions –but is 4 x 2Attackers

Shoot out radiatorShoot out tyresVulnerable when crossing ditches

OperatorsNo air-conditioningNo 4 x 4They cross ditches at high speed

ResultVehicle that do not last

Fender and fender trimming fell off

Noise, Vibration and Harshness

Differential noise control on RG32M

1. NVH fingerprinting2. Noise control3. Vibration control4. Modal analysis

Noise, Vibration and Harshness

Solving of interior vibration problems on 4‐poster test rig

Pseudo‐random driven rattle and squeak tests

Whole body and hand‐arm vibration assessment and control

Multi-axial durability testing

Clients: General Motors SA, Mercedes-Benz, Ford Motor Company of SA, Nissan SA, Fiat, BMW, Bell, John-Deere

Fuel tank accelerated durability

• Mission profile driven accelerated durability testing

• Time domain acceleration and strain responses reconstructed

• Accuracy – R2 ≈ 0.9

Ford fuel tank accelerated durability test. The Ford test track as well as gravel and other roads used for user profile reconstruction. Vehicle driven at different fuel and load levels.

This is a 6-axis test on a Mercedes C-Class fuel tank to verify the integirty of the fuel tank cross-member.

Structural integrity

The engine mount bracket had to be certified for SA mission profiles.

Strain and acceleration recordings and FEA used to confirm structural integrity.

Accelerated durability testing of connecting rod

Mission profile verification of a Road Rail Vehicle

Thermal fatigue testing of exhaust pipe (Ford Motor Company of SA, Bosal)

• Investmech test rig can heat to 800 °C• Can be combined with durability test• Case in South Africa:

– 4 litre Ford LDV, 4 x 4, driven uphill in Drakensberg fully loaded– Exhaust pipes heated to ~ 700 °C– Exhaust hangers needed to be improved as well – SN Rubber in PE


Quality tests for Fiat

Shock absorber durability

Client: Arvin Mentor (Gabriel)

Test: Heat up, fatigue test, characterize.

Low temperature brittleness

Test rig cools down to ‐100°C

Clients:

Nissan SA

Dunlop

Durability testing of towing devices

• At present – According to SANS 1505

• Part 1 – Towing device brackets• Part 2 – Coupling ball & ball supports• Similar to ISO 3854

– Cyclic test to 2 million cycles• Report issued per specimen tested

– Implications• Design for 50% probability of failure• Test 3 specimens

– Any one passes – certificate can be issued• Design for 2.3% probability of failure

– Test specimens until it passes the test

• Proposed– Prescribe probability of failure during the

design phase– Equivalent quasi-static test

• Lower cost• Shorter test time• Shorter Time to Market


The SANS standards do not prescribe the probability of failure that shall be used in the design of the towing device.If designed on the 50% probability of failure, just test until a specimen pass the test.If designed on 2.3% probability of failure, materials thicker and more costly

Mean Sr-N curves


Mean line Sr-N curve (BS 7608, 1994:41)

A stress range of 80 MPa on Class F2 weld detail will result in life of 2 million cycles.

If 10 specimens are loaded, 5 might fail before reaching 2 million cycles.

Design Sr-N curve


Basic design Sr-N curve (BS 7608, 1994:42)

A stress range of 80 MPa on Class F2 weld detail will result in life of 1 million cycles.

If 100 specimens are loaded, 2.3 might fail before reaching 2 million cycles.

Servo-hydraulic products

• Servo Controller• Servo hydraulic actuator• Several measurement modules• Loadcells

Who uses it: DLS (Previously LEW), Gerotek, SABS, Mercedes‐Benz, VWSA, Nissan, EDC – Koedoespoort, BTM, Steellite, Bosal, University of Pretoria

Crashworthiness of Ladle trailer - Strain rates

• Low strain rate = 10-5 to 10-1 /s• Medium strain rate = 10-1 to 102 /s

– Typical for vehicle collisions– Strain rate sensitivity becomes pronounced at 10-1 /s– At strain rate of 102 /s, behaviour of material resistance to impact changes

• High strain rate = 102 to 104 /s– Travelling wave can cause varying strain response

• Transmitted waves and reflected waves may be excited

• High strain-rate is not necessarily strain events that occur over a short interval– This is a high frequency event

• Strain rate sensitivity– Positive = strength increase with increase in strain-rate – Steel has this

characteristic• Model with Cowper-Symonds model

Ladle


MPCVirtual clamps modelled as multi-point constraintForces can be calculated for clamp designClamps designed for forces and actual clamps modelled in simpler model

Coupling: Euler elements = fluid elementsLagrangian elements = structural elementsEulerian and Lagrangian solver = separateCoupling algorithm computes interaction between the two sets of elements

Liquid volume


Liquid metal in the ladle before impact

Dynamic response of the liquid metal in the ladle during impact

Liquid metal modelled as Euler volumeSloshing was simulated and dynamics of sloshing included in all simulationsLiquid forces on the lid and clamps calculated

Trailer


Suspension axle modelled as beamLeaf springs = surfaces with thicknessWheels = surfaces with thickness with same stiffness as real tyreCoefficient of friction: rolling = 0.1, sliding = 0.6 (Johnson, Baughn and Johnson, 1992:510)

Trailer:Solid model used for the trailer connectionsBeam elements for chassisSurface with thickness for plates

Towing vehicle super structure


Model for the chassis bought from InternetAxle modelled as beam elementLeaf springs modelled as surface elements with thicknessChassis super structure – beam elementsReal vehicles investigated to update model to be accurate structural reconstructionBody plate not modelled

The same approach was modelled for the impact vehicle

Verification

• Conservation of angular momentum– This is only applicable

around the wheel set assumed to touch the ground

• Conservation of linear momentum:– Only applicable for before

and immediately after the collision with assumption of no tyre traction forces

• Conservation of energy– Only applicable in parts of

motion where energy is not lost

• What was compared:– Energy loss– Velocities after the collision

• Compliance criteria:– Difference of less than 10%


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Tip: Use dynamically equivalent systems where possible! That is, equivalent mass , centre of gravity and mass moments of inertia

Typical results obtained


Force between impacting bodies•Maximum resultant force 550kN at 21 ms

Computer:Intel Core2DUO CPU2 x 3.00 GHz6GB of RAM

Analysis time:15 hours

Timestep:1E-3 seconds (1ms)

Click here if movie does not start automatically

Stress on the shell inner surface after 40ms


Click here if movie does not start automatically

ROPS & FOPS analysis and testing

• ISO 3449


Mortar launcher simulation

• Accelerations measured• Force with unknown value at discrete

time steps used as reference• Force values calculated at each time

step to reconstruct recorded acceleration– Nelder-Mead global optimization

algorithm applied• Impulse used to calculate change in

linear momentum of mortat• Muzzle velocity was within 5%


Why laboratory testing?

• Reduces time to market• Minimize warranty cost• Increase product quality• Available time for testing is continuously decreasing

– Need for accelerated testing• Towing devices – why not a static test only?

• Need to verify models to estimate reliability and durability– Not possible to accurately calculate reliability or durability from basic principles alone

• Take weld failures as example

• Laboratory tests– Quick– Repeatable– Allow in-test inspection– Does not strike, get exhausted, etc – sorry, except for the rig’s solidarity with ESKOM– Can reconstruct client mission profiles


Testing in the Year 2020

• www.saaw.co.za– Economic growth rate 5% - 8% per annum– Annual job growth rate – 3.5%– 60% reduction of households living under the poverty line– More local content and local value must be created

• Investmech:– Alternative propulsion

• Energy source, drive lines, tyres, etc.

– Advanced recyclable materials• Some might not have infinite fatigue life

– Emphasis on reliability testing

– More vehicles on the road = More emphasis on crashworthiness and safety


Role players in testing

• Investmech• AIDC – Automotive Industry Development Centre• Gerotek

– Wide range of structural, mechanical, electrical, ergonomics and other tests– Offers relevant training and R&D

• Standards and design/test codes• Towing device manufacturers• Manufacturers:

– Mercedes Benz, Volkswagen, Nissan SA• Universities:

– University of Stellenbosch– University of Pretoria– University of Cape Town– University of Witwatersrand


Conclusion

• South Africa offers what is needed for durability testing of cars and light trucks:– Components– Full-scale– Characterization

• Future of testing in SA:– Will reduce time for product development due to powerful computers

and simulation software• Complex real-life situations can be simulated

– Increased use for mission profile driven durability and reliability:• Low volume in SA

– 70% growth over next 10 years – be prepared• Complex real-life situations can be reconstructed

• I trust that you now have a picture of what is offered and can be offered in SA to meet your test requirements


Documents

Testing of motor cars in South Africa - VDI R1.0 of motor cars in South Africa... · • Engineering Certification • Products • Manufacturing • Hydraulics – design & installation