A study on measurement of welding residual stresses using ESPI system

초록

The size and shape of welding residual stress depends on the way of construction or manufacturing method and this residual stress causes the deterioration of fatigue life. The measurement methods of residual stress are classified into two types, i.e. destructive and non-destructive methods. Each method has its own drawbacks. The former has a drawback to destruct the specimens and the second method has a main drawback of inaccuracy of the measurement result. Therefore, in this paper, Electronic speckle pattern interferometry(ESPI) system is applied; which is nondestructive and non-contact equipment which can measure the relatively accurate strain on large field. After the measurement, the effect of residual stress on fatigue life can be performed immediately. In this study, the stresses are superposed step by step on the area of specimen with residual stresses. Then strain is measured by ESPI system until the applying stress reaches the elasto-plastic boundary value. Finally, the residual stress can be determined by subtraction of applying stress from the superposed stress value. The measured results of residual stresses distribution were compared and verified with those of other methods.