Welding Strength Analysis Of Spacecraft Spherical High-pressure Cylinder

Nowadays,with high specific strength,corrosion resistance and excellent high and low temperature performance,the TC4 titanium alloy is more and more widely used in aerospace field.TC4 high-pressure cylinder is welded into a complete storage sphere with two half-spherical shell through the way of butt welding.As the high-pressure gas stored in the spherical gas cylinder,the weld quality is related to the safe usage of high-pressure cylinder and the whole spacecraft.Spacecraft spherical high-pressure cylinders periodically run into and out of the earth's shadow,while the pressure of the high-pressure cylinder will periodically change.With the effect of cyclic loading,the welded joint are prone to fatigue fracture.So prediction of residual stress measurement of the TC4 high-pressure cylinder welding joint and fatigue analysis are of great significance.In this paper,ANSYS software is used for spacecraft high-pressure cylinders for welding numerical simulation based on the experiment of welding process in reference[71].The welding temperature field,stress field change process with time,and the distribution of welding residual stress are obtained by using APDL language and live-death technology to achieve the welding heat loading and moving.Then the experimental results were compared with the simulation results to verify the numerical simulation method to simulate is credible.After welding residual stress field obtained,ANSYS is used to simulate the quenching process.Finally,the fatigue life and the coefficient of safety are obtained by using the ANSYS fe-safe to analyze the fatigue of high pressure cylinder.As the temperature field shows,the model is symmetrical,but the temperature of the surface of spherical shell node distribution and the change trend are not symmetrical.During the welding,after passed the end effect,the welding temperature field presents the characteristics of the quasi steady state distribution.The type "M" transverse residual stress distribution appeared on both sides of weld after the welding line cooled.Quenching aging treatment can effectively reduce the welding residual stress,and the ability to make the welding residual stress distribution in homogeneous.The shortest of fatigue life located in the high pressure cylinder gas mouth,while the weld fatigue safety coefficient is low which means the fatigue failure probability is bigger.Residual stress on the safety is not always bad for using the titanium alloy spherical high-pressure cylinders safely,appropriate residual stress can increase the bearing capacity.Therefore,the reasonable welding and heat treatment process of TC4 titanium alloy spherical bearing capacity has a significant effect of high pressure gas cylinders.