Reliability assessment of seat belt webbings through accelerated life testing

Abstract

A reliability assessment method for seat belt webbings is proposed based on life–stress relationships combined with statistical distribution using a newly designed accelerated test equipment. The method was successfully used to predict lifetimes of webbing by performing an accelerated life test (ALT) which was designed using more severe temperatures, UV irradiance and abrasion as stress factors. The failure times obtained from the ALT were converted into those under the service conditions assuming an Arrhenius life–stress relationship for temperature and an inverse power life–stress relationship for UV irradiance. In estimating the lifetimes, the underlying distributions of the failure times were determined based on identification of the degradation mechanism. The results confirm that the assessment method through ALT is effective for lifetime prediction with shorter test times. Most significant is that good quality webbing does not always guarantee good reliability, demonstrating the importance of, and the challenges in, identifying failure causes and designing in reliability in the process of webbing manufacture.