Reliability-Based Analytic Models for Fatigue Lifetime Distribution Estimation of Series Mechanical Systems under Random Load considering Strength Degradation Path Dependence

Peng Gao,Liyang Xie

doi:10.1155/2017/5291086

Abstract

Time-dependent statistical characteristics of load process and strength degradation process are critical to lifetime distribution of series mechanical systems. Conventional rain-flow counting method for lifetime distribution estimation has limited practical application due to its strict requirement for statistical properties of load process. Besides, dynamic interaction between load process and strength degradation process results in strength degradation path dependence (SDPD). SDPD and failure dependence of components jointly bring considerable difficulties in prediction of system lifetime distribution and system residual lifetime distribution. To address these problems, reliability-based analytic models for estimation of whole lifetime distribution and residual lifetime distribution of series mechanical systems under random load are developed in this paper, which take the time-dependent statistical parameters of load process and strength degradation process as the input of the models. Furthermore, SDPD and failure dependence of components are taken into account in the proposed models in an explicit mathematical expression. The results show that SDPD, failure dependence of components, and initial strength dispersion have significant influences on system lifetime distribution.

Highlights

With the function, structure, and working environment of mechanical products becoming complicated, accurate assessment of fatigue lifetime distribution of mechanical systems in their full lifetime cycles is encountered with new challenges and has attracted extensive attention from researchers and engineers [1,2,3]
Reliability-based analytic models for estimation of whole lifetime distribution and residual lifetime distribution of series mechanical systems under random load are developed in this paper, which take the time-dependent statistical parameters of load process and strength degradation process as the input of the models
strength degradation path dependence (SDPD) and failure dependence of components are taken into account in the proposed models in an explicit mathematical expression

Summary

Introduction

Structure, and working environment of mechanical products becoming complicated, accurate assessment of fatigue lifetime distribution of mechanical systems in their full lifetime cycles is encountered with new challenges and has attracted extensive attention from researchers and engineers [1,2,3]. To address the aforementioned problems, analytic models for fatigue lifetime distribution estimation of mechanical systems under random load are developed in this paper, which can take the time-dependent statistical characteristics of load and the failure dependence of components into consideration and provide an explicit expression of the PDF of systematic lifetime that characterized the systematic lifetime distributions. Numerical examples are given to validate the proposed models and illustrate key factors that have great influences on system lifetime distributions

Randomness and Dependence of Fatigue Lifetime Distributions of Components

Reliability-Based Analytic Models for Systematic Lifetime Distribution

Numerical Examples

Conclusions