A REVIEW ON STRESS RELAXATION AND BOLT LOAD RETENTION OF MAGNESIUM ALLOYS FOR AUTOMOTIVE APPLICATIONS

Abstract An attempt has been made to comprehensively review the stress relaxation and bolt load retention (BLR) test procedures and behaviour of Mg alloys. The aim is to provide a basis for a common test procedure for BLR testing of Mg alloys for automotive applications. The review indicates that bolt load retention behaviour of Mg alloys, an important engineering design property, depends on both compressive creep property and the compliance of the bolt joints. The stress in Mg components in bolt joints is usually highly non-uniform and the magnitude of the stress is sometimes high, up to yield or even above yield strength. BLR behaviour can be understood qualitatively from these characteristics, but currently, BLR cannot be quantitatively predicted from stress relaxation or creep test results. The literature review shows that there is a need for a common BLR fixture and BLR specimen (shape and dimensions) representative of the joined components in automotive applications. Needs for future research on the...