权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Study of Stress-Strain Relation and Fatigue Strength of Steel under Random Loading Conditions

随机载荷条件下钢的应力应变关系和疲劳强度研究

基本信息

批准号：
04650393
负责人：
TOMITA Yasumitsu
金额：
$ 1.28万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1993
项目状态：
已结题

项目摘要

Inorder to obtain the stress-strain relation, axial static and cyclic loading tests were performed for three kinds of steels (mild steel, conventional high strength steel, thermo-mechanical controlled process steel) for mother materials and heat-treated materials. The stress-strain ralation under cyclic-loading conditions and random loading conditions differs from the one under static loading condition.The characteristics of the response such as hardeing, softening, elastic-plastic transition stress value, Bauschinger effect, ets.vary as the number of loading cycles proceeds, and after a certain number of loading cycles, the stress-strain relation preserves stable characteristics. The relationship between parameters of the stress-strain relation and the fatigue strength obtained from constant amplitude loading fatigue tests was investigated.The main resuls obtained in this research are as follows.1) For mother material specimens tested in this research, the clastic limit stress under cyclick-loading condition and random loading conditions decreases as compared with one under ststic-loading condition, and softening appears during cyclic-loading tests. For heat-treated specimens, the elastic limit stress increases under cyclic-loading condition, and hardening apppears during cyclic-loading tests.2) There is a close correlstion between 0.2% proof stress under cyclic-loading condition and the fatigue strength. We can regared 0.2% proof stress under cyclic-loading condition as one of parameters which estimate the fatigue strength of material.3) It can be considered that materials, of which cyclic elastic limit stress is closer th the tensil strength and cyclic strain-hardening exponent n is smaller, are good for fatigue strength.

为了获得应力-应变关系，对母材和热处理材料的三种钢（低碳钢、常规高强度钢、热机械控制工艺钢）进行了轴向静载荷和循环载荷试验。循环加载条件和随机加载条件下的应力应变关系与静态加载条件下的应力应变关系不同，硬化、软化、弹塑性转变应力值、鲍辛格效应等响应特性随着加载循环次数的进行而变化，经过一定次数的加载循环后，应力应变关系保持稳定的特性。研究了等幅加载疲劳试验得到的应力应变关系参数与疲劳强度之间的关系。本研究得到的主要结果如下：1）本研究试验的母材试件在循环加载和随机加载条件下的碎裂极限应力较静载条件下有所降低，且在循环加载试验中出现软化现象。对于热处理后的试件，在循环加载条件下，弹性极限应力增大，并且在循环加载试验中出现硬化。2)循环加载条件下0.2%屈服强度与疲劳强度之间存在密切的相关性。可以将循环加载条件下的0.2%屈服强度作为估计材料疲劳强度的参数之一。3）可以认为，循环弹性极限应力越接近拉伸强度、循环应变硬化指数n越小，材料的疲劳强度越好。