Accelerated life test with some parameter change in life-stress relation

In most literature, accelerated life testing (ALT) models always assume the parameters in the life-stress relation remain unchanged under all stress levels. But in many practical situations, the upper bound of the stress levels under which such parameters keep unchanged is often unknown. In this paper we study the situation that the life-stress relation keeps unchanged, however, some parameters involved may be changed if it is over-stressed. A general method is propsed to consider such situations.