Development Of A Method For Obtaining Mechanical Property Of Welded Joints By Combining Indentation Test With Surface Strain Measurement

The critical factor to structural integrity evaluation and life prediction of welded structures is to accurately grasp structure material mechanical properties.In order to facilitate the acquisition of mechanical properties of materials in local area of welded structures,a method of obtaining mechanical properties of materials based on a combination of indentation test and surface strain measurement was proposed and developed by using a combination of theoretical research,finite element simulation and experimental analysis in this thesis.And,the method was used to test the inhomogeneous material mechanical properties in local area of dissimilar metal welded joints at the safety end of nuclear power primary circuit.The main research contents and results are as follows:Based on the analysis of the traditional method of obtaining material mechanical properties by indentation test,the strain variation on the surface of the tested sample during the indentation test was explored,and the basic method of using the indentation test in combination with surface strain measurement to characterize the mechanical properties parameters of the welded joints materials was determined.The ball indentation test and surface strain measurement process were simulated by using finite element software in this thesis,and the suitable test parameters were determined through analysis.The influence of the elastic modulus,yield strength and strain hardening exponent on the variation of surface strain was discussed,which laid the foundation for the development of a method to obtain the mechanical property parameters of materials based on the indentation test and surface strain measurement.The ball indentation test was performed on 316L austenitic stainless steel and the surface strain change was measured.The surface strain-indentation depth curve was used to calculate its plastic mechanical property parameters,and the traditional tensile test results were compared to verify the applicability and accuracy of the method.And,the influencing factors such as indenter offset distance and strain gauge size on the test results were analyzed by using a combination of numerical simulation and experiment.The inhomogeneous mechanical properties of the material in the local area of the dissimilar metal welded joint at safety end of nuclear power primary circuit were tested by using a combination of indentation test and surface strain measurement.On the basis of the analysis of its structure,the distribution of inhomogeneous mechanical properties in the based metal area was obtained by using its surface strain-indentation depth curves.