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

AN ANALYSIS OF PHYSICAL SIGNIFICANCE OF CONSTITUTIVE EQUATIONS FOR CREEP UNDER CONSTANT LOAD AND CONSTANT STRESS

恒载恒应力蠕变本构方程的物理意义分析

基本信息

批准号：
08650813
负责人：
ENDO Takao
金额：
$ 1.41万
依托单位：
YOKOHAMA NATIONAL UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08650813/
关键词：
creep aluminum aluminum-magnesium alloy omega method effective stress constitutive equation heat-resistant steel aluminum ω method Omega method activation energy for creep strain rate acceleration factor imaginary initial strain ra

项目摘要

Creep life of low alloy heat resistant steels can be successfully predicted by use of two parameters, namely, imaginary initial strain rate and strain rate acceleration factor, OMEGA. In spite of this practical convenience, the physical significance of these parameters remain unclear. The present study was undertaken to accumulate and analyze the data on stress and temperature dependence of these parameters not only for heat resistant steels but also for single phase materials such as aluminum and aluminum-3at.%magnesium alloy. It was made clear that the magnitude of omega for single phase materials was almost equal to that of stress exponent for imaginary initial strain rate at lower stresses and basically independent of stress. In case of aluminaum-3at.% magnesium alloy at higher stresses, the values of omega decreased with increasing stress and they became less than the stress exponent for their imaginary initial strain rate. In contrary to the case of single phase materials, the magnitude of omega in heat resistant steels which were strengthened with precipitates was much larger than that of stress exponent and they decreased with increasing stress. To understand the physical significance of the omega, the ratio of effective stress (sigma^<**>) to total flow stress (sigma) was determined from the analysis of stress relaxation curve of single phase aluminum-3at.% magnesium alloy. From the analysis based on the effective stress, it was demonstrated that OMEGA was expressed as below ;OMEGA=n_p+m^<**> (* ln sigma**/* In ln sigma),where n_p is the stress exponent for mobile dislocation density, m^<**> is the effective stress exponent for mobile dislocation velocity. Thus we inferred from the present results that the presence of precipitates in heat resistant steels affect the magnitude of (* ln sigma**/* In ln sigma).

利用虚初始应变速率和应变速率加速因子Ω这两个参数可以成功地预测低合金耐热钢的蠕变寿命。尽管这些参数在实际上很方便，但它们的物理意义仍然不清楚。本研究不仅对耐热钢，而且对单相材料如铝和铝-3at.%的应力和温度依赖性进行了数据积累和分析镁合金结果表明，在较低应力下，单相材料的Ω与虚初始应变率下的应力指数的大小几乎相等，且基本上与应力无关。在氧化铝的情况下-3at.%镁合金在较高应力下，ω值随应力的增加而减小，并小于其虚初始应变速率的应力指数。与单相材料的情况相反，析出相强化的耐热钢中Ω的大小远大于应力指数的大小，且随着应力的增加而减小。为了理解Ω的物理意义，从单相铝-3at.%的应力松弛曲线的分析确定有效应力（σ ^**>）与总流动应力（σ）的比率。镁合金从基于有效应力的分析中，证明了Ω的表达式为：Ω =n_p+m^<**>（* ln sigma**/* In ln sigma），其中n_p是移动的位错密度的应力指数，m^<**>是移动的位错速度的有效应力指数。因此，我们从目前的结果推断，耐热钢中沉淀物的存在影响（* ln σ **/* ln σ）的大小。