Research And System Development Of Quality Grade Assessment Method For Welded Joints Based On EN 15085 Standard

With the development of welding technology,Chinese enterprises must master and apply advanced technical standards to compete with other international advanced companies.At present,there is still a big gap between the welding standards of my country’s rail vehicles and vehicle components and international advanced standards.In addition,research on how to use international standards for fatigue design and quality assessment of welded products has become an important topic.The fatigue strength design of welded products is the basis of quality grade assessment.In the design of welded products,the welded joint is relatively complicated,and the stress state of the joint cannot be confirmed using traditional fatigue strength assessment methods.It is difficult to assess the quality grade.And there is no application software on the market for evaluating the quality grade of welded structures.Based on the above problems,this paper studies the EN 15085 standard,using the quality grade assessment requirements in the standard as a framework,focusing on the research of method of obtaining the stress factor through the structural stress method,and solving the problems of stress state confirmation and quality level evaluation of welded joints.According to this method,a set of visual quality assessment system for welded joints has been developed,which provides an effective tool for achieving efficient and accurate quality assessment of welded joints.The specific research contents of this paper are as follows:(1)Research on calculation method of stress factor based on structural stress method.In this paper,the structural stress method with grid-insensitive characteristics is first studied,and based on the linear fatigue damage accumulation theory and the principle of fatigue damage equivalence,the method of obtaining the stress factor by the structural stress method is studied,and the stress factor calculated using fatigue life is derived Methods.(2)Research on quality grade evaluation process.According to the EN 15085 design requirements,part of the stress level,quality level,inspection level reference standards and design requirements,combined with the static strength design method,fatigue life calculation method and quality level evaluation method of the welded joint in the engineering practice,the quality rating evaluation process of the welded joint is designed.(3)Development and design of quality grade evaluation system.Based on the quality level evaluation process,using C++ language and OSG graphics library as development tools,the functional modules in the quality level evaluation system are designed to make the system meet the needs of quality level evaluation in actual engineering.(4)Visual display function research and design.Using OSG scene graph technology and three-dimensional rendering technology,the visual grid model of the welded structure is reconstructed based on the finite element model data,and the evaluation result data is drawn on the model’s weld unit in the form of a color cloud.(5)Study the application of software systems in engineering examples.Taking a railway freight car body as an example,the quality grade of the weld joint of the car body is evaluated to verify the effectiveness and practicability of the research method and the developed system in engineering problems.The quality grade evaluation system for welded joints developed in this paper can meet the quality evaluation requirements of large-scale rail welding products in actual projects.The system has a visualization function and can display the fatigue distribution of welds through the result cloud diagram,which greatly improves the design effectiveness of welding products.The development of this system provides an effective tool for fatigue design and quality grade evaluation of welding products.