高、低周复合疲劳及其试验技术

文中介绍了一种简单易行的复合疲劳试验机,在此试验机上进行了高、低周复合疲劳试验。结果表明,随着次循环的频率和载荷幅增大,铝合金(LY12—CZ)试件的裂纹萌生寿命显著下降。然而,当次循环频率很低时,寿命也下降,这似乎属于“变形损伤”,因缺口附近的应变出现“棘轮”现象。复合疲劳的损伤模型尚有待研究。

OPTIMUM DESIGN FOR PROFILE CONTOUR OF TURBINE DISK

A combined optimization method for searching the minimum disk weight and the best disk profile contour is provided which uses the random-walk method and the random-try method alternately. The whole disk profile contour can be linearized by linear segments,and thus the disk can be treated as a series of trapezoid-section ringlets. A subroutine for automatical generation of calculation sections is deveon loped. Taking the disk weight as objective function,the geometric parameters and the axial thickness of the ringlets as design variables, and the five stress criteria as constrains, we applied the combined optimization method to a practical disk and obtained a feasible point within 5-7 minutes on an IBM-PC. After one hour calculation the disk weight has been reduced 12.22%. It is proved that this method increases convergence rate obviously.