Processing And Numerical Simulation Of Pure Titanium Shell Workpiece For Cardiac Pacemaker

Titanium and titanium alloys have a broad application prospect in the field of active medical devices for their excellent biocompatibility,admirable corrosion resistance,good stamping and welding performance.Cardiac pacemaker is an important part of active medical devices and its shell workpiece made from titanium and titanium alloys.However,the research and application of cardiac pacemaker shell is rare and the import rate reaches to 98%.That mainly because the processing of shell is complex,low precision of domestic equipment,high cost of the research and related technology has long been blocked abroad and other reasons.The only domestic product is single chamber pacemaker made by Shanxi Qinming medical.Other enterprises or individuals have also been studied in this field,but there is no breakthrough.In this paper,the finite element simulation software DEFORM was used to simulate the stamping process of the pure titanium(TA 1)sheet.The state variables of the shell workpiece were analyzed,the stamping parameters were optimized.Then the mold and the shell of cardiac pacemaker were fabricated according the simulation results.After that,the shell workpiece were welded by laser welding technology,the quality of the weld joint were examined by means of visual inspection,metallographic examination and color inspection.Finally,the shell surface was sandblasted and the related blasting process was also explored.The main conclusions are as follows:(1)Different process parameters have an important influence on the forming of TA1 sheet:low strain rate is conducive to TA1 sheet forming;the friction coefficient between the sheet and the punch should be as large as possible while the friction coefficient between the sheet and die,blank holder should be smaller when then the quality of shell’s surface is ensured;Larger convex and concave mold single-sided clearance and radius of fillet is better.(2)The equivalent stress and strain value of the rounded corner in the shell of concave workpiece are much larger than those of the other deformation zones.The rule of increase and decrease of the thickness is opposite in the shell’s concave upward and concave down zones.The follow rate of the linear part of the outline of the shell workpiece is about 1.7 times faster than curved part,and the metal’s flow rate of the outer edge portion of the bottom deformation region to the geometric center portion gradually decreases from 50 mm/s to 0 mm/s.The amount of spring back from the flange deformation area to the bottom deformation zone of the shell is gradually decreased.(3)The degree of deformation is related to the angle between the straight edge and the arc edge of the outline of the shell:the smaller the angle between the straight edge and the arc edge is,the more severe the deformation is.In addition,it is found that the flange radius deformation zone is the most serious deformation area,while the bottom deformation area is not deformed,and the deformation degree of the concave radius deformation zone and the sidewall deformation zone is moderate.(4)In the laser welding experiment,the reasonable parameters of laser welding through several parameters adjustment and weld quality inspection are as below:welding power is 410～430 W and the linear speed is 45～60 mm/s.(5)The better sandblasting effect of the surface can be obtained by sandblasting the shell under the pressure of 0.15 MPa using white corundum with particle size of 30 or under the pressure of 0.25 MPa using white corundum with particle size of 60.