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Biaxial Wheel Test Development and Minimum Cycle Requirement

Users Conference 12 November 2015

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• Circa 1980s LBF put wheel force transducers on wheels in “normal” service and collected Wheel Force Transducer Data (WFTD)

• Circa 1990’s two N.A. vehicle manufacturers built load files by strain matching from proving ground to strain matching on Zwarp.

• WFTD from both vehicle manufacturers is nearly identical between sedans and minivans.

Background of North American (N.A.) Biaxial Wheel Test Development

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JOIB Matrix for Sedans and Minivans with rated wheel load 6,196 N

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• 2004 - The methodology of building SAE J2562 is spelledout in SAE 2004-01-1578

• 2005 - SAE J2562 is published without minimum cycleacceptance criteria

• 2005-01-1862: The Science and Methodology of SAE WheelFatigue Test Specifications where sampling is introduced

Background of North American (N.A.) Biaxial Wheel Test Development

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• 2005-2015 vehicle manufacturers specified minimum cyclesfor their J2562 tests based on theoretical cumulativedamage.

• 2014-01-0073 – Minimum cycle requirement for SAE J2562(N.A. Passenger Car Zwarp)

Background of North American (N.A.) Biaxial Wheel Test Development

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Minimum Cycle Requirements for SAE J2562

Ref. SAE 2004-01-1578, J2562

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J 2562 Silhouette

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Ken Archibald, Independent Test Services

William Schnaidt and Rick Wallace, General Motors Co.

Kyle Archibald, Independent Test Services

Minimum Cycle Requirements for SAE J2562 - Authors

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Vehicle manufacturers have been replicating N.A. vehicle service on proving grounds for over 70 years.

Proving Grounds Allow Accelerated Vehicle Tests

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• “Development of the SAE Biaxial Wheel Test Load File,”SAE Technical Paper 2004-01-1578, 2004

• SAE shows how to reduce proving grounds wheel forces and strain data into a load file.

• Load file is to be run on a laboratory machine called biaxial fatigue.

SAE J2562 Biaxial Fatigue Testing Replicates Proving Grounds

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• Apparatus • Machines type ABC (pictures)

• Methodology• Procedure • Load file unique to application• Broken up into Scaled Base Load Sequence Repeats (termed

Repeats). Each Repeat contains 240,433 wheel revolutions

SAE J2562

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Snapshot of load file sequence:

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Load File Illustration

• No acceptance criteria because everything is based ontheoretical fatigue calculations

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• 14 wheel designs evaluated to SAE J2562 apparatus and methodology

• Steel wheel designs• Ballasted passenger vehicle wheels, sedan, minivan

• All wheels tested to fracture over 7 years of validation testing• Proving grounds testing found two designs unacceptable• Lives of acceptable and unacceptable designs evaluated

Empirical Evidence of Wheel Lives

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Proving grounds vs biaxial fatigue data:

• Lives of unacceptable wheel designs (determined on proving grounds) were less than those of acceptable wheel designs.

• Biaxial fatigue data is evaluated using Weibull B10C50 statistics. Same as other SAE wheel recommended practices.

Statistical Evaluation of Test Results

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• Minimum Cycle Requirements - The amount of cycles under test below which wheels in the population have been found to be unserviceable in their intended service.

• Wheel manufacturers must design and build to exceed the minimum cycle requirements. With some confidence level in SAE Wheel Recommendations B10C50 is used.

SAE Wheel Conventions

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Unserviceable Wheel Designs (Dashed Lines)

Serviceable Wheel Designs (Solid Lines)

Level of reliability deemed acceptableRecommended 4x

Minimum Cycle Repeats

Conclusions and Recommendations

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Cumulative Percent Failed versus Cycles

Plot of Cumulative Percent Versus Cycles

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Wheel Type (Material

Minimum Scaled Base Load Sequence Repeats

Sample Size = 3 4 5 6 7

Ferrous 5.3 4.6 4.1 3.8 3.6

Cycles x1000,000

1.27 1.11 0.99 0.91 0.87

Performance Requirements in SAE J2562 Based on SAE Paper

Where:• Minimum Scaled Base Load Sequence is the file that includes all load pairs. The number of cycles is 240,433 or basically 240,000 cycles.

•Multiplying the number of sequences repeats times 240,433 cycles/sequence provides the minimum cycles for the amount of samples.

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• At seven samples the minimum cycle requirement is 3.6 x 240,000 or 864,000 cycles

• All other combinations of samples and associated number ofrepeats results in the same B10C50 confidence level.

• The minimum cycle requirement is applicable to ferrouswheels only.

Performance Requirements in SAE J2562 based on SAE Paper Continued

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• Motorsport

• Light Truck

• Applications of other materials such as aluminum and composites.

Opportunities

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Comparison of Shape of SAE and AKR Load Files

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• The SAE and AKR do not have sufficient lateral loads to replicate damage from race track

• The maximum radial load occurs at a high lateral load, presumably due to load shift

• The radial loads are relatively low during low lateral loads, suggesting unballasted vehicle (not five passengers and luggage)

• The above reasons indicate SAE has an opportunity to develop a motor sport load file.

Observations of Comparison of SAE and AKR Passenger Car and Ferrari Race Track

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Comparison of Shape of Load Files

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• Neither the SAE or AKR are sufficient for motorsport service.

• The load file will be for unballasted vehicle service.

• Concessions might have to be made to accommodate the high laterals relative tothe radial loads.

Observations of Comparison of Ferrari File to SAE and AKR

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Biaxial Wheel Test Development and Minimum Cycle Requirement ���Background of North American (N.A.) Biaxial Wheel Test Development JOIB Matrix for Sedans and Minivans with rated wheel load 6,196 NBackground of North American (N.A.) Biaxial Wheel Test Development Background of North American (N.A.) Biaxial Wheel Test Development Minimum Cycle Requirements for SAE J2562J 2562 SilhouetteMinimum Cycle Requirements for SAE J2562 - AuthorsProving Grounds Allow Accelerated Vehicle TestsSAE J2562 Biaxial Fatigue Testing Replicates Proving GroundsSAE J2562Snapshot of load file sequence:�Load File IllustrationEmpirical Evidence of Wheel LivesStatistical Evaluation of Test ResultsSAE Wheel ConventionsConclusions and Recommendations Cumulative Percent Failed versus CyclesPerformance Requirements in SAE J2562 Based on SAE PaperPerformance Requirements in SAE J2562 based on SAE Paper ContinuedOpportunitiesComparison of Shape of SAE and AKR Load FilesObservations of Comparison of SAE and AKR Passenger Car and Ferrari Race TrackComparison of Shape of Load FilesObservations of Comparison of Ferrari File to SAE and AKR