Effects of Strain Rate and Temperature on the Dynamic Shear Deformation and Fracture Behaviour of 316L Stainless Steel

• Main Authors: Zong-YunLi, 李宗運
• Other Authors: Woei-Shyan Lee
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/35621818012829003456

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 98 === The dynamic shear deformation behaviour and fracture characteristics of 316L stainless steel are investigated by using a split-Hopkinson torsional bar system. Shear deformation is conducted at temperatures of -150℃, 25℃ and 300℃ under strain rates ranging from 1×103s-1 to 3×103s-1, respectively.The experimental results indicate that the shear flow response is found to be sensitive to the strain, strain rate and temperature. The flow stress, fracture strain, work hardening rate, yielding strength, work hardening coefficient, strain rate sensitivity all increase with the increasing strain rate for a fixed temperature, but decrease with the increasing temperature under a constant strain rate. The inverse tendency is observed for activation energy. The observed high strain rate shear deformation behaviour of 316L stainless steel can be described using the Kobayashi and Dodd constitutive equation. From the SEM observations, it is found that the fracture surfaces are characterized by a dimple-like structure, which is indicative of a ductile failure mode. The morphology and the density of these dimples are influenced greatly by strain rate and temperature conditions. Optical microscopy observations reveal that grain of the fracture surfaces are twisted into band-like features. The microhardness of these shear bands increases with the strain rate, but decreases with the temperature as a result of different work hardening effects.