Study On Obtaining Local Mechanical Properties Of Nuclear Power Welded Structure By Ball Indentation Test

Indentation technology,also known as depth-sensitive indentation technology,is a relatively advanced mechanical performance detection technology used in complex environments.It can detect different mechanrics at the micron level without affecting the service of key components.The performance parameters have very broad application prospects.This paper mainly aims at the current situation that the local mechanical properties of nuclear power welding joints are difficult to obtain.The combination of theoretical analysis,physical experiments and finite element inversion analysis is used to establish an appropriate mathematical model and apply the model to the safety end of nuclear power structures Testing of mechanical properties of welded joints.The main research contents of this paper are as follows:(1)To study the constitutive relationship of commonly used metal materials in nuclear power structures and the theoretical method of indentation experiment to calculate the mechanical property parameters of materials.First,the Oliver-Pharr method is used to calculate the elastic modulus and indentation hardness of the material through the load-depth curve,and secondly,the yield strength,tensile strength and hardening index of the material are calculated by the energy method and the self-similarity theory.(2)Having transformed the electronic universal testing machine into an indentation test platform,and debugged it,and studied the influence of different test factors on the indentation test results.Under the optimized test conditions,the indentation test can be accurately reflected true indentation response.The mechanical performance parameters of nuclear grade austenitic stainless steel 316L under different pre-deformation rates were obtained through the load-depth curve,and the indentation test results were verified using uniaxial tensile test.(3)Using ABAQUS for finite element inversion analysis,an indentation experiment model under elastoplastic material was established,and numerical simulations were carried out on the 2D and 3D ball indentation experiments under different spherical indenter radii.The numerical simulation was analyzed by comparison The obtained parameters and experimental data verified the validity of the results of the finite element model;the indentation morphology of the indentation simulation experiment under different mechanical parameters was analyzed,and the laws of different protrusion amounts and mechanical performance parameters were summarized.(4)Take the dissimilar metal welded joint of the pressure vessel safety end in the primary circuit of nuclear power as an example,based on its structural analysis,conduct uniform indentation experiments at different positions of the welded joint,and determine the range of heat affected zone of the welded joint through the load depth curve predicted various mechanical performance parameters at different locations.