| The stainless steel vehicle body is a cylindrical integral load-bearing structure,and a large number of plate beam structures are used on the vehicle body.The main welding form of these plate beam structures is spot welding.During the operation of the vehicle,the welding joints on the vehicle body bear complex vehicle body loads,and the welding joints and their connecting structure are prone to fatigue damage.In order to ensure the safe and stable operation of the vehicle body during service,evaluating the fatigue performance of vehicle body structure and welding joints is very important.This paper takes a stainless steel spot welding vehicle as the research object,calculates and analyzes the strength and stiffness of the spot welding vehicle,analyzes the influence of different spot welding modeling methods on the vehicle body modal,and evaluates and analyzes the fatigue performance of the vehicle body structure and welding joints..The specific research content is as follows:(1)The research analyzes the influence of spot welding modeling method on structural modal.First,the influence of the spot welding modeling method on the mode of the hat beam is analyzed.Single rigid beam element,multi-rigid beam element,umbrella element and CWELD element are used to simulate the welding joint structure,and the hat beam model is calculated by Nastran software.The comparison and analysis of the calculated modal frequency and the test results show that the calculated results are in good agreement with the test results when CWELD elements are used to simulate the solder joints.Based on the above analysis,elastic beam elements and CWELD elements are used to simulate the welding points of the vehicle body.The calculated modal analysis results of the vehicle body show that the first-order mode of the vehicle body using CWELD unit is increased by 0.21 Hz,which is closer to reality.It is recommended to use CWELD unit to simulate the welding joint structure in large-scale spot welding structure.(2)Based on the established finite element model of the spot welded vehicle body,the load and restraint are applied according to the BS EN12663-2010 standard,and the strength and deformation of the vehicle body under 13 main load conditions are analyzed using Ansys soft calculation.The analysis is based on the TB1335-1996 standard.The rigidity of the vehicle body is calculated,and the calculation results show that the strength and rigidity of the vehicle body meet the design requirements.(3)Based on the BS EN12663-2010 standard,three fatigue load conditions of longitudinal,vertical and transverse are established.The Ansys software is used to calculate the vehicle body stress under the fatigue load,and the weld seam where the vehicle body stress is larger is selected.According to the IIW-2008 standard,the fatigue life of the welds at the key positions of the vehicle body is evaluated.The calculation results show that the fatigue cumulative damage ratio of the vehicle body welds is less than 1,and the fatigue life of the vehicle body welds meets the design requirements.(4)Based on the BS EN 15085-3:2007 standard,the static strength of the spot welded vehicle body under three overload conditions is evaluated.Based on the BS EN12663-2010 standard,the welding joint shear force of the vehicle body under three fatigue load conditions is calculated and analyzed,and the fatigue performance of the welding joint is analyzed based on the shear force variation range.The calculation results show that the static strength and fatigue strength of the solder joints meet the design requirements.The results show that when modeling spot welding finite element,the simulation accuracy of using the CWELD model is high,and the calculated structural modal frequency is more accurate.The fatigue cumulative damage ratio of the key welds of the vehicle body is less than 1.The fatigue life of the welded seam of the vehicle body meets the design requirements;the shearing force of the welded joints is less than the allowable value,and the static strength and fatigue strength of the welded joints meet the design requirements. |
