RELIABILITY ANALYSIS BASED ON THE WEAKEST-LINK-MODEL AND PROBABILITY FRACTURE CHARACTERISTICS OF WELDED STRUCTURE

摘要

This paper studies the weakest-link model for welded joint using three points bending fatigue specimen. Using IDPC method, the fatigue crack extension law is measured. The crack initiation life is defined when the crack size reaches 0.5 mm. In this model, the welded joint is considered as a chain that contains three-independence link, and the weakest link determines the strength of the chain. In the work, crack propagation speeds are tested on 16MnR steel at stress ratio R=0.1. The crack growth rates are tested respectively in three independent parts of welded joint: BM, HAZ and WM. With the data of the crack size vs. cycle number, the low cycle fatigue life is obtained. By statistic theory, the probability distributions for these individual parts are drawn out. Probability distribution functions are obtained and the reliability can be calculated.