G030061 単軸クリープ試験片へのスリット導入と変形一様性([G03006]材料力学部門一般セッション(6):高温・環境)

Abstract

Specific numerical analyses have been required at designing modern high temperature machines and structures. Since analytical results usually depend on a constitutive equation of creep, it is necessary to derive a high-precision equation. Creep properties on deformation can be normally obtained using constant load creep machines, but constant stress creep tests are more suitable to acquire high-precision creep data. In order to keep the true stress constant, an applied load or the lever ratio should be changed during the test duration. Conventional uniaxial creep specimens have ridges attached on both sides of gauge length to measure deformation outside an electric furnace. For ductile materials, however, even if the constant stress creep testing machine are used, these ridges constrain area reduction around them, and unequal-uniform deformation breaks the constant volume condition in the gauge portion during deformation. Authors have proposed introducing slits into the ridge to release the circumferential constraint by the extensometer ridges. In this study, taking into account a realistic analytic condition, the authors carried out elastic creep Finite Element (FE) analyses to investigate an optimum depth of the slit. Subsequently, a series of constant stress creep tests using SUS304 steel are conducted to examine the effect of introducing slits on the performance of uniform deformation. The analytical and the experimental results show that the introduction of these slits into the ridges would improve uniform deformation effectively.