DEVELOPMENT OF RESIDUAL STRESS DRIVEN STRESS CORROSION CRACK INITIATION AND GROWTH SPECIMENS

摘要

In this work, a new specimen to study crack initiationand growth is developed with residual stresses as thedriving force for cracking in thick walled pipe. Potentialbenefits are more representative crack initiation behaviorto plant operation because the sample undergoes stressrelaxation typical of an operating component.Additionally, the sample could be used to study effects ofsurface finish on crack initiation without concerns of loadpath effects typical of conventional samples. Specimenswere made by forcing a series of oversized tool steel ballsthrough 2” Schedule XX pipes with a push rod, effectivelyexpanding the pipe. Characterization by hardness,contour residual stress measurement, and electronmicroscopy was performed to determine whether samplescan be made with consistent properties. Experimentalresults show that the process can impart reproducibleaxial residual stresses and strains at the pipe innerdiameter.