摘要
本文用４０Ｃｒ钢制成的光滑圆柱试样，在高频疲劳试验机上，首先测出ｒ＝０．１，σ＝４４０ＭＰａ下的断裂寿命Ｎｆ。然后在同一应力比和应力水平下，分别进行了寿命比ｎ／Ｎｆ＝０．４、０．６、０．８和０．９的疲劳试验。卸载后用电测法在万能试验机上测出不同损伤度下的Ｅ值，按公式Ｄ＝１－Ｅ／Ｅ计算损伤值Ｄ，再按幂指数Ｄ＝进行拟合。我们发现，实验值与拟台值吻合，说明高周疲劳损伤确按幂规律演变。根据这个规律，可以推算出临界损伤变量Ｄｃ＝０．１２２８。这值与普通钢的Ｄｃ值约为０．２２有很大差异。因此，可以作出结论：静拉测得的Ｄｃ值不能用于交变应力下的构件。
In this paper,usins the smooth cylindrical specimen made of 40Cr steel. Firstly,the fracture lifeNf was measured in the high-cycle fatigue testing machine under r = 0. 1,σ = 440MPa,Then,thefatigue tests were done respectively in the life ratio = 0. 4, 0. 6, 0. 8, 0. 9 under the same stressratio and same stress level. After unloading,the values E were measured in the different damagedegree by means of the strain gages in the universal testing machine. The damage variable D wascalculated according to the formula D =1 - ,and then imitated according to the power indexlaw, D = K. We find that the experimental values and imitated values are agreeable. It showsthat the damage of the high-cycle fatigue varies really accordins to the power index law. On thebasis of this law,the critical damage variable can be calculated,Dc= 0. 1228. This value is verydifferent from Dc about 0. 22 of the general steel. Therefore,we can conclude that Dc of the staticload is not applicable to that of the fluctuating load.
关键词
高周疲劳
损伤变量
损伤演变规律
疲劳
high-cycle fatigue
damage variable
damage evolutional law
fatigue cumulative damage
