Development of the SAE Biaxial Wheel Test Load File 2004-01-1578
Recently published SAE Recommended Practice J2562 - SAE Biaxial Wheel Test standardized the terminology, equipment, and test procedure for the biaxial wheel test. This test was originally presented by Fraunhofer Institut Betriebsfestigkeit - LBF (Fraunhofer Institute for Structural Durability) in SAE paper 830135 “Automotive Wheels, Method and Procedure for Optimal Design and Testing”. The first release of SAE J2562 included a generic, scalable load file applicable to wheels designed for five to eight passenger vehicles with capacity to carry a proportional amount of luggage or ballast. Future releases of SAE J2562 would include two additional load files; one applicable to light trucks that have substantial cargo capacity and one for sports cars typically limited to two passengers and marginal luggage.
This report details the process used to develop the SAE Biaxial Wheel Test Load File for passenger vehicles. The process included fatigue analysis technologies developed over the last 25 years. These technologies included a two dimensional (radial and lateral) histogram, called Joint-Occurrence-In-Band (JOIB), for cycle counting of wheel load histories that represent actual customer usage. Peak-valley strain values from these block-cycle loading events were load inputs for a strain-life fatigue damage analysis. Using a constant fatigue damage approach, high cycle, low loads were replaced with equivalent damage at higher loads using fewer cycles. The final load file was simplified into 37 unique load pairs of radial and lateral loads divided into two speed files; a high speed file with 96 steps and a low speed file with 30 steps. The high speed was applied 8 times before each application of the low speed. It was left up to the equipment users to determine the appropriate tilt angle for each load pair and each user must establish their own performance criteria.