Research On Weld Stress Analysis Method Bsaed On CAE

Welding has been widely used in many fields such as railway vehicles,construction machinery,and aerospace industry due to its good connectivity and convenient manufacturing and processing.However,the welded structure is prone to fatigue fracture at the welded joint under the action of alternating loads during use because of welding defects in the process of manufacturing such as root incomplete penetration and weld toe undercut.When evaluating the strength of welded structures engineeringly,node coupling is often used to simulate the positions of weld seams,without considering the impact of initial weld defects on the stresses at the welds.Research on the existing domestic and foreign welding structure fatigue strength analysis methods and related standards,analyze and study the differences between different methods and related standards and the scope of application.The calculation process of the nodal force method to calculate the structural stress is deeply studied.This method has the advantages of insensitive grid,simple theory,and convenient calculation,and the mesh insensitivity of the nodal force is explained from a mechanical point of view.The detailed calculation process based on shell element is given.For the problem of the mismatch between the degrees of freedom of the three-dimensional solid element and the shell element,the derivation process of transforming the three-degree-of-freedom node force of the three-dimensional solid element node into the six-degree-of-freedom node force of the shell element node is given.The three-dimensional solid element-based structural stress calculations have verified the feasibility of this method.Establishing the local coordinate system along the weld is one of the difficulties in calculating the structural stress by the nodal force method.A program written in FORTRAN is proposed in this paper to calculate structural stress.In the program,a local coordinate system of the spatial straight and curved welds is established.The nodal force information in the global coordinate system is transformed into the local coordinate system transform by using a coordinate transformation matrix to realize the calculation of structural stress Three common finite element models of butt joints,T-joints and lap joints are established,and the influence of element type and mesh size on the structural stress of different joint types is studied.On this basis,the initial weld defects such as incomplete penetration at the root and the influence of external loads on the structural stress are studied,and a finite element model based on the finite element model that does not contain weld defects,calculates and considers the structural stress of weld defects.Finally,the strength of a certain type of subway bogie frame is analyzed,and the calculation results show that its static strength and fatigue strength meet the requirements of rel evant standards.At the same time,the feasibility of the above calculation method is verified.