Structural Strength Degradation Model Based on Non-stationary Gamma Process

Strength degradation is a stochastic and irreversible process.Gamma process is an independent nonnegative increment process which can be used to describe the characteristics of strength degradation.It is unreasonable to choose a linear function to describe the strength degradation trend considering that the degradation rate may change over time.So,a non-linear power law is proposed to describe the strength degradation trend based on preliminary work.It is more general compared with the linear one and the inadequacy of strict linear assumption is overcome.Then,the model parameters of non-stationary Gamma process are estimated based on the maximum likelihood method.Finally,it is proved that the non-stationary Gamma process can accurately reflect the strength degradation law through comparative analysis of a real example.