Safety Assessment Of Joint Performance And Porosity Defects Of Laser Welding Of Pure Titanium Plates

Laser welding is widely used in the welding of titanium alloy structural parts due to its small welding heat input,large aspect ratio,and high weld strength.However,the weld bead of laser welding solidifies quickly and sometimes produces pore defects.Although the welding standards strictly limit the size and number of pores,pore defects can easily lead to premature failure of the welded plate.For this reason,this article takes the TA2 pure titanium plate laser welding joint as the research object,and studies the differences in the microstructure,tensile,fracture and other mechanical properties of different areas of the pure titanium plate welded joint.Based on the traditional fracture criterion,The SINTAP-FAD failure assessment method was introduced to conduct a more accurate structural safety assessment of laser welded joints containing pores.The research results have important theoretical significance and application value for the safety assessment of pure titanium laser welded joints in engineering.First,the macro and micro morphology observation,the division of the welding area and the mechanical performance test of the welded joint of the laser-welded pure titanium plate were carried out.Study the microstructure changes in the width direction of the weld through metallographic observation,divide the weld zone,heat-affected zone and base metal zone through the hardness test and combined with the characteristics of the structure,and obtain it through the tensile test and the Charpy i MPact test The tensile yield strength and i MPact toughness of each area of the weld,combined with microstructure observation and fracture morphology,analyzed the difference in fracture characteristics of each area of the weld,completed the analysis of the performance of the laser welded joint,and provided material parameters and boundaries for subsequent research condition.Secondly,the pore defects of the weld cross-section were tested and observed,and reasonable pore defect distribution characteristics were selected according to the laser welding process standards of titanium and titanium alloys.Based on the above test results,a finite element simulation model containing pore defects was established to study the distribution of pore defects in detail.The characteristics include the influence of the number of pores,pore size and pore distribution position on the stress and strain field of welded joints,analyze the local stress concentration phenomenon in welded joints under different pore defect distribution characteristics,and further explore the influence of pore defects on the subsequent fracture failure process of joints.Finally,through the introduction of the SINTAP-FAD structural integrity assessment method and the concept of failure assessment chart,the safety assessment of the behavior of pore defects causing instability and cracking of the weld is carried out,and the distribution characteristics of pore defects including the number of pores,the size of pores and the distribution of pores are discussed.The influence of the position on the safety of welded joints under different working loads,and the critical failure load under different pore characteristics are calculated,and the sensitivity of the pore distribution position to weld cracking is studied.The research work provides an effective evaluation method for the instability and cracking of welded joints.