混凝土单轴拉伸疲劳试验中Paris公式参数的确定

针对以往确定Paris公式中的参数C,m值,需要求得很多的参数,或经过复杂的试验得出试验数据进行分析,提出通过对抗压强度进行反演分析,得到原始裂纹及孔隙总面积,根据断裂力学中圆裂纹的应力强度因子表达式,把应力强度因子转化为试件所受应力,利用素混凝土单轴拉伸疲劳试验数据,求得C,m值.分析表明:参数值随应力水平的变化较大;m值变化即使在同一个数量级内,也会导致C值在多个数量级内的变化;最大应力水平为0.7时,解出的参数值比较可靠.

Determining the Values of Two Constants in Paris Equation via Uniaxial Tensile Fatigue Tests of Concrete

To determine the values of two constants C and m in Paris equation,generally a lot of parameters are to be determined or the data resulting from complex tests are to be analyzed.A new way is proposed to solve the tedious problem by the inversion of compressive strength of concrete so as to obtain the total area of initial cracks and pores.Then,the stress intensity factor is converted into the stress the specimens are undergoing according to the expression of stress intensity factor of circular crack in fracture mechanics.In such a way the values of C and m are given by the data resulting from the uniaxial tensile fatigue tests of plain concrete.The analysis shows that the values of relevant parameters change greatly with the stress level,and the value of C changes in several orders of magnitude even though the value of m changes in the same order of magnitude. It's found that the values of relevant parameters are comparatively reliable if the max stress level is equal to 0.7.