Research On Measuring Welding Residual Stress Of Plate Of Moderate Thickness Using Blind-hole Method

The welding residual stress exists in welding structure inevitably, and influences themechanical property of structure. Therefore, accurate measurement of residual stress is veryimportant. Since 1930 residual stress testing technology has been engaged in research. As yet,the blind-hole method is the most extensive application in the engineering, but it still existsome lacks, just as the reasonable choice of cutting measure and space among holes, plasticdeformation in drilling boundary and the aperture, in order to improve their precision andaccuracy, we still need to do lots of work.In this paper, through analysis accessional stress by cutting force and cutting heatcaused and plastic deformation in drilling boundary, the blind hole measuring residual stresshas been studied and improved, as follows:(1) Through controlling the drilling measure to reduce the effect of cutting force and heat,that is more than once to widening hole and increasing depth more than once; according to thetest standards, hole depth is from 1.2 times the aperture, to ensure that all the depth directionown better release strain. By measuring in prefabricated residual stress piece, strain reliefparameters A and B are verified by tension test, comparing two methods with theprefabricated stress, to judge the feasibility of improving.(2) To eliminate the affect of the plastic deformation, Strain relief parameters A and Bwas modified. By a large force tension experiments, the relationship between strain reliefparameters and stress, energy parameter S was obtained, the variation formula of strain releasefactors with energy parameter S was obtained.(3) Application of the finite element method, a 3-D finite element model was made tosimulate and analyzed, acquiring the strain relief parameters and plastic modifying formula.FEA compared to experimental results to determine the feasibility of finite element method.The results show: improved blind hole measuring method could reduce the error bycutting force and heat, and improve the measurement accuracy; Modified strain reliefparameters A and B under plastic formation greatly reduced measure error. The results ofFEM analysis can also achieve the same purpose, the method is feasible.