A Comparison of the Dynamic Shear Plastic Deformation Behavior and Fracture Characteristic of Continuous and Pulsed Current Plasma Arc Welding (PAW) Weldments of 304L Stainless Steel

• Main Authors: Ming-Hsing Chiang, 江明信
• Other Authors: Woei-Shyan Lee
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/14384219721300198906

碩士 === 國立成功大學 === 機械工程學系碩博士班 === 90 === 　The dynamic shear plastic deformation behavior and fracture characteristics of continuous current (CC) and pulsed current (PC) plasma arc weldments of 304L stainless steel under six strain rates (900s-1, 1300s-1, 1900s-1, 2200s-1, 2600 s-1 and 3300s-1) are studied at room temperature (25℃) by means of torsional split-Hopkinson bar. Results indicate strain rate significantly influences 304L weldment mechanical properties. Increasing strain rate increases flow stress, work-hardening rate, strain rate sensitivity and temperature rise of 304L weldments. For all tested strain rate ranges, strain rate sensitivity increases as strain increases, but activation volume decreases. The shear stress, work-hardening rate, temperature rise and strain rate sensitivity of PC weldments are all higher than those of CC weldments in the same strain rate, but only activation volume is lower. OM shows cracking is through the fusion zone, partially melted zone and heat affected zone. Flowlines are clearly twisted at both sides of the crack. Fracture is due to shear band formation. 　SEM shows fracture surfaces consist of fusion zone dimples, heat affected zone dimples and smooth shallow dimples. Increasing strain rate increases density and depth of FZ and HAZ dimples, but smooth shallow dimples decrease. This tendency is more significant in PC weldments than in CC weldments. The Kobayashi & Dodd constitutive equation successfully describes the high-strain-rate shear plastic behavior of 304L weldments.