Numerical Simulation Of Tube-Plate Structure Welding Deformation Based On Sysweld

Fixed tube-plate heat exchangers have been widely used in the pressure vessel,oil,chemical,heating and ventilation and other industries.The huge amount of welds on heat exchanger will lead to large welding deformation in heat exchanger produces if it is not the controlled properly.The welding deformation and welding residual stress will deteriorate the tube plate of the stress state,resulting in lax,and even pipe being pull out and other serious consequences.So the prediction and control of the welding deformation of the heat exchanger has a great engineering application value.In this paper,a rotary welding equipment is designed and assembled.On this basis,an automatic welding test experiment platform is built for the tube plate heat exchanger automatic welding.The thermocouple thermometer is used to measure the temperature of the designated point near the welding,and the thermal cycling curves of these points are obtained.The stress near the weld is measured by blind-hole method.Using the Sysweld software,the local model of heat transfer structure is established,and the heat source model is put forward.The results of the local model simulation show that the residual stress is centrally symmetrical.The tangential residual stress in the vicinity of the weld is the tensile stress,and with the distance from weld increasing,the tensile stress reduces and then changes to the compressive stress.The radial stress is the tensile stress,and it decreases gradually with the distance from the weld increasing,and the stress at the edge decreases to 0.The residual plastic strain is mainly distributed in the weld and heat affected zone,so the size of the WME is determined according to the boundary of the heat affected zone.In order to improve the computational efficiency,according to the actual situation of the heat exchanger,a method is proposed to reduce the size of the local model.The equivalent convective heat transfer coefficient is calculated and corrected by the principle of equal heat dissipation,and the convective heat transfer coefficient is determined which value is 440W/(m2· K).The value of elastic restraint is determined by narrowing the range gradually.Based on the comprehensive analysis of different influencing factors,A formula of elastic restraint is put forward.Three main influencing factors which are axial temperature force,tensile stiffness and bending rigidity are considered in the formula.The formula is verified.The influence of different welding sequence on the welding deformation of heat exchanger is studied by using the "local-global " mapping finite element method.Through the comparison of the overall deformation under the five welding orders,it is found that the deformation under the order of symmetrical distribution is smallest.The feasibility of the method of reducing the size of the local model is verified by comparing the overall deformation of the tube plate heat exchanger under different local models.