軽合金の2段重複繰返応力試験

Abstract

Fatigue under working stress is a rather complicated problem, but it is very important in practical cases. Study on the fatigue under multiple repeated stress is one of the approaches to the problem.In this paper are reported the experimental results of multiple repeated stress fatigue test which the authors made recently.Specimens made of two Al-alloys have been tested by Ono's rotating bending fatigue testing machine. Summary of the results is as follows:(1) In the case where Al-alloy 52 S is used as the material, and the primary stress is chosen to be 10kg/mm2, which is the fatigue strength at N=107, Σn/N is larger than unity.(2) In the case where Al-alloy is used, and the primary stress is 12kg/mm2, Σn/N is nearly equal to unity.(3) In the case where Al-alloy 17S is used, and the primary and the secondary stresses are 24 and 18kg/mm2 respectively, Σn/N is smaller than unity, and when the primary and the secondary stresses are 18 and 24kg/mm2 respectively, Σn/N is larger than unity, and sometimes n2/N2 is larger than unity.In this case, nine specimens are used under the same condition, and Levy's method is used to represent the experimental results. It is compared with other conventional methods and the authors consider that the Levy's method is very useful.(4) Levy's method, however, has an application limit, which is not made clear in Levy's original paper. The authors pointed out this limit.