用非线性加速模型评估步降应力加速退化数据

基于累积损伤等效方法提出一种能够描述产品性能非线性退化过程的分段非线性加速退化模型(SNADM,Segmented Nonlinear Accelerated Degradation Model),有效解决了产品性能退化率为时变函数时其寿命难以准确评估的问题.推导了总体累积退化量函数的分段表达式,结合非线性函数和加速方程得到SNADM的表达式;用数值迭代法对SNADM进行参数辨识进而对贮存条件下产品退化轨迹统计量函数进行外推,由产品退化量分布随机过程类型确定可靠度函数,再结合失效阈值对产品贮存寿命进行评估.对某导弹制冷器进行了步降应力加速退化试验,评估结果验证了该方法的有效性和正确性.

Assessing step-down stress accelerated degradation data via nonlinear accelerated model

A segmented nonlinear accelerated degradation model (SNADM) was introduced based on the equivalent method of accumulative damage theory, which tackles the problem that product life is difficult to determine with degradation rate being a function of the variable of time. A segmented expression of the function of overall accumulative degradation was derived and combined with nonlinear function and accelerated degradation function, from which a expression of SNADM was obtained. The parameters of the SNADM were identified by numerical iteration; further the statistical function of degradation track was extrapolated. The reliability function was determined through the type of random process of the degradation distribution. Then an evaluation to product storage life was undertaken by combining the statistical function of degradation track, reliability function and failure threshold value. An example of a missile refrigerator undergoes a step-down stress accelerated degradation test while test data were evaluated with SNADM. The technology introduced is validated with the resultant coincidence of both evaluated and field storage lives.