DEVELOPMENT OF NONDESTRUCTIVE QUALITY ASSESSMENT CRITERION OF 7075-T6AL-ZN-MG ALLOY COMPONENTS USING FRACTURE-MECHANICS TECHNIQUES

A quality assessment procedure based on a-fracture mechanics approach is analytically developed for the non-destructive evaluation of compon ents made of 7075-T6 grade Al-Zn-Mg alloy. The maximum allowable defec t sizes for both static and cyclic loads are computed. For different s tress levels and shapes of the defects, the initially existing allowab le defect sizes versus number of operating cycles curves are presented : The tolerable defect sizes, in most of the cases, are found to be we ll below the detectable limit of the most sensitive non-destructive te sting techniques. Hence knowledge of the maximum allowable operating c ycles of the components for non-destructively detectable minimum defec ts is essential. A practical example of the assessment of welded alumi nium alloy bridge components is cited. These assessments are very help ful in the realistic prediction of the safe life of the components as well as their best utilization in service.