Abstract
In the present paper, consideration has been carried out of the relationship between the defect detectability of NDT and the repair rate of welds and the reliability of inspected welds.
In order to get a certain high quality level of welds, critical level for repair Acr should be set smaller than the critical allowable defect size acr. That is, acr/Acr is the factor of safety to defect detectability of NDT.
The more setting smaller of critical level for repair or deteriorating the accuracy of defect measuring by NDT, the more repair rate of welds γ increases. Increasing of γ does not always realize increasing of the reliability of welds R. In the case of deteriorating of accuracy of measuring the defect, k decreases even if γ increases.
The reliability of welds increasess according to increasing repair rate in the case of increasing sampling ratio or in the case of inspecting with emphasis on higher defective joints even if sampling-ratio is equal to the case of random sampling.
Based on the above consideration, the decision method is discussed of the rational inspection method for assuring a certain reliability of welds and also minimizing the total cost of inspection.
