摘要
疲劳寿命的预报在船舶与海洋工程领域中相当重要 ,但其关键问题是要找到一种较科学的疲劳寿命预报方法。最近 ,本文第二作者提出了一种海洋结构物疲劳寿命预报的统一方法。该方法是基于疲劳裂纹扩展理论而发展起来的 ,在其九个参数模型的假设之下 ,能够较好地解释一些其它方法所不能解释的现象。采用该方法的主要障碍在于需要确定疲劳裂纹扩展率。作者通过对不同的疲劳裂纹扩展率的比较研究 ,并推广Mc Evily模型后 ,提出了一个具有较宽适用范围的九个参数疲劳裂纹扩展率模型 (从门槛域一直到不稳定断裂域 )。本文的主要目的是解决如何根据一些现有的疲劳试验数据来确定这九个模型参数的问题。文中给出了通过实验数据确定裂纹扩展率模型中各个参数的方法 ,并进行了模型参数的灵敏度分析。通过对文献中一些试验数据的收集 。
Recently, the second author proposed a unified fatigue life prediction method. The essence of the unified method is to predict the fatigue life of marine structure using fatigue crack propagation (FCP) theory instead of the currently used cumulative fatigue damage (CFD) theory using S N curves. There have been some fatigue life prediction methods in the recent decades, but most of them cannot explain some known fatigue phenomena. However, Unified Fatigue Life Prediction Method can manage to explain them. It can consider the influences of initial defects and load sequences. The main obstacle of adoptimg the unified fatigue life prediction method is the determination of the fatigue crack growth rate. Based on a comparative study of several existing crack growth rate laws, a new 9 parameter fatigue crack growth rate law was proposed by the second author which was derived from extending the McEvily crack growth rate law. It offers a general formula which can illustrate the condition from threshold to unstable fracture, also, it uses the conception of virtual strength (σ V), which can solve the paradox that the static test of the material′s ultimate strength (σ u) is generally higher than the yield stress (σ Y). The purpose of this paper is to address the problem how to estimate the 9 model parameters using the existing fatigue data. To solve this problem, nonlinear curve fitting theory is used. A sensitivity analysis is also carried out for the 9 model parameters to show some parameter′s sensitivity property. Based on the collection of some experimental data, fatigue crack growth rates for some metals are given.
出处
《中国造船》
EI
CSCD
北大核心
2003年第3期74-79,共6页
Shipbuilding of China
