二軸疲労試験装置の小型化に向けた十字型試験片の最適設計

抄録

This study presents the design of miniature cruciform specimens for load reduction in a biaxial fatigue testing machine. For safety and reliability of materials and components in structures, it is necessary to acquire material strength data. Material strength data in the case of receiving a cyclic load is generally obtained by fatigue test under a uniaxial stress condition, such as a tension-compression or a rotational bending test. Therefore, by testing the multiaxial stress state in accordance with the load condition of the actual structures, it is necessary to know the strength properties, so-called deformation and fracture behaviors, in the multiaxial stress state. One of the fatigue tests under multiaxial stress is a biaxial fatigue-testing machine using a cruciform specimen. In the biaxial test, the external dimensions of the conventional cruciform specimen are relatively large about 200 mm, the load of several tens of kilonewtons was required for the yield of the gauge part. In such a large test piece, when cut out from the thin material or the actual components, there is a limit to the size of the test specimen dimensions. Furthermore, large loads cause a specimen and testing machine to become large. This study aimed at analyzing for a miniature sized cruciform specimen in order to capable of small sized biaxial fatigue test. In this paper, focusing on the shape design of the miniature cruciform specimen by topology optimization is discussed. The shape obtained as a result of topology optimization is a complex shape composed of curved surfaces, it is difficult to manufacture the specimen by cutting out from the thin material or the actual components. Therefore, after replacing it with a relatively simple shape, the effect of shape dimensions on the load was examined using the finite element analysis.