应力松弛法确定材料蠕变参数

Determination of Creep Parameters of Materials Using a Stress Relaxation Method

摘要:

对圆棒试件在不同初始应力下的单轴拉伸应力松弛过程进行了有限元模拟。假定材料的蠕变行为遵循Norton蠕变法则：(为蠕变速率，B为蠕变常数，σ为施加的应力)，通过对应力松弛曲线的分析和推导，提出了2种通过应力松弛试验来确定材料蠕变参数的新方法。第1种方法仅需要单次的应力松弛试验即可得到材料的蠕变应力指数；第2种方法需首先通过外推法求得初始应力松弛速率，进而通过多条应力松弛曲线求得蠕变应力指数。提出的方法为高温材料蠕变力学性能的测定提供了一条新思路。

关键词:蠕变;应力松弛;蠕变参数;有限元

Abstract:

The stress relaxation processes of prestressed cylindrical specimens were simulated by FEM. Assuming the creep of material obeys the Norton creep law: (is the creep strain rate, B is a material and temperature dependent constant, and σ is the applied stress), we proposed two approaches to determine the creep stress exponent using the stress relaxation method. The first method requires a single stress relaxation curve. The second requires extracting the initial stress relaxation rate by an extrapolation method, and multiple stress relaxation curves are needed to yield the creep stress exponent. The present work provides some new notions on the determination of creep properties of materials which usually serve at high temperature.

Key words:creep; stress relaxation; creep parameter; finite element