Calibration Procedure for Standardization of SAE J175 Shock Absorbers

In the design phase of aluminum wheels for passenger cars, the wheel's ability to withstand low speed side impacts with minimal damage inflicted to the wheel is of major concern. There are two side impact test standards available today. The one that appears to better simulate an actual wheel-curb impact situation is the SAE J175-88. Part of the test setup includes a deflection check of elastomeric shock absorbers under specified load. The authors have devised a technique to obtain the data for this calibration from a monotonic load/displacement curve. Curve fitting is followed by intercept calculation and a check against specifications. The specified elastomer deflection range under load dictates the expected dynamic response in the actual test. Therefore, in addition to the SAE recommended natural rubber, the authors also investigated the deflection characteristics of alternative polymeric materials, such as EPDM, neoprene and urethane. The technique used to obtain the data yielded repeatable results, based on replication trials. Polymeric materials of different chemistry but similar Shore A durometer hardness values did not yield the same deflection at intercept.