热疲劳-蠕变寿命的能量损伤理论

ENERGY DAMAGE THEORY OF THERMO-FATIGUE AND CREEP LIFE

本文对发动机热部件在高温下工作寿命大大降低的问题 ,提出一种温度对材料应变能损伤的原理 ,这个理论在估算部件热疲劳 /蠕变交互寿命时 ,包括了弹性能、塑性能和蠕变能量的损伤总合 ;并且在整个过程中 ,随着温度和时间的不断变化 ,对各种物性参数进行修正 ,从而更好的逼近真实状态。文中用著名的“应变范围划分法 (SPR)”和“应变能范围划分法 (SEP)”的实验结果与本法的计算数值对比 ,甚为满意。本方法的特点是物理概念清楚 ,运算方便 ,适应性强 ,对一般高温结构强度的寿命估算 ,具有广泛的应用价值。

A new life prediction method of temperature and load damage for high temperature components of engine is presented.In consideration of the interaction between thermo fatigue and creep,the new method includes the damage summation of elastic energy,plastic energy and creep energy of material.The precise finite element method of thermal elastic plastic creep conditions is used to solve the correlation of maltiple physical parameters of material (stress,strain,Young ′s modulus,thermal expansive coefficient,yield limit,plastic hardering exponent,creep hardering exponent,etc,) with temperature effect.In the new method the correction can be made according to the changes of temperature and time,so that it expands the applicable area of general damage mechanics.This paper makes reference to the experimental results of famous“Strain Range Partitioning (SRP)”and“Strain Energy Partitioning (SEP)”methods.The calculated results by the presented method locate between the experimental results of SRP and SEP methods.The new method has the advantages in clearness of physical concept,convenience of calculation and wide range for application.It is satifactory for engineering practice in life prediction of high temperature components.