金属非对称循环下的匀变速加载问题

Problem of the Uniform and Variable Speed of Loading About Metal Subjected to Asymmetrical Cycling Loads

由损伤力学理论可知,疲劳是由材料内部的损伤演化导致的,但其损伤演化的机理并不清楚。为此,我们将高分子物理中断裂的分子理论推广应用于金属的疲劳损伤,认为金属的断裂是一个松驰过程,宏观断裂是微观原子键断裂热活化的结果。以Q235钢为例,在CMT5105万能电子试验机上进行拉压非对称循环疲劳试验。从原子键离解的视角出发并结合试验数据,讨论并推算诸多因素影响下匀、变速加载时非对称循环疲劳损伤演化律的具体形式。再将速率作为重点考虑因素提出了新的疲劳损伤演化律,分别讨论了匀、变速情况下损伤演化律的基本形式,并对速率相关参数因子进行了修正。结果表明,新的疲劳损伤演化律形式简单、参数少、应用广泛且与试验结果贴合较好。

According to damage mechanics,fatigue is caused by the evolution of the damage inside the material,but the mec-hanism is not clear.Therefore,the molecular theory of fracture in polymer physics is extended to be applied to metal fatigue damage.It is found that fracture of metal is a relaxation process,and macro fracture is ascribed to a thermal activation of the microscopic atomic bond breaking.Taking Q235 steel as an example,the testing of the tension and compression of asymmetrical cycle is carried on the CMT5105 universal electronic testing machine.From the view of atomic bond dissociation and combined with the experimental data,the concrete form of asymmetrical cycle fatigue damage evolution under the constant and variable loading rates in multiple factors is discussed and deduced.Then a new fatigue damage evolution is proposed by taking the rate as the main consideration,the basic forms of damage evolution under the conditions of constant and variable rates are discussed respectively,and rate dependent parameter factors are modified.The results show that the new fatigue damage evolution is simple in form,few in parameters,wild in application,and is better fitted with the experimental results.