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[Keywords] valve design stress concentration local refinement method stress concentration is a common phenomenon in valve design. Through scientific calculation, mastering the data information of stress concentration is of great significance for optimizing valve product structure design. At the same time, stress concentration has a great influence on the service life of valve products. Under normal circumstances, the fatigue life of valve structure has strong sensitivity to stress concentration, and most of the previous calculation methods are in conventional statics. The results obtained in the analysis, the calculation results in this state have a large error in the fatigue prediction of valve products. Therefore, in order to obtain more accurate data, it is necessary to adopt a scientific stress concentration calculation method. Analyze this issue.
I. Stress Concentration Analysis Method (1) Local Refinement Method The local refinement method is a common method for stress concentration analysis. It has high accuracy in simulating structural stress concentration. The local refinement method refers to dividing the entire simulation area to form a plurality of mesh forms, and then performing key encryption for a unit or a region in which the stress gradient changes greatly. In actual operation, you can center a certain point in the grid and refine the surrounding area to encrypt the unit or area.
(B) Sub-model method In the application of the local refinement method, there will be a phenomenon that the mesh density in the mesh area of ​​some cells is not enough, but the mesh density of other parts is sufficient, in this case For areas where users are more concerned, it is difficult to ensure the accuracy of the stress concentration analysis results, and it is impossible to meet the needs of users. Here, sub-model technology needs to be applied. Sub-model technology mainly performs more detailed unit segmentation on cells in the obtained regions, thereby obtaining more accurate data. The sub-model technique needs to cut the stress concentration area, and the cutting boundary is the dividing boundary of the whole model area. The cutting boundary of the overall model can provide basis and reference for the determination of the sub-model boundary. The sub-model method is based on the St. Venan principle. If the load of the model is cut and distributed in different regions, the change of stress changes at the edge of the load application part, while the stress on other areas does not occur. big change. Therefore, when applying the sub-model technology, there should be a certain distance from the location of the stress concentration to ensure the accuracy of the results.
(3) Adaptive meshing The adaptive mesh method is mainly used to estimate the error according to the deformation and fluctuation caused by the stress variation in the region where the stress changes are significant, so as to automatically judge whether the distribution density of the grid is scientific. , to provide the necessary basis for grid distribution. If the result of the judgment indicates that the mesh density is insufficient, the program will automatically upgrade the mesh density to reduce the error. The grid is gradually refined in the process of constant adjustment, and the coupling of the grid distribution point and the object understanding is achieved, so that the error can be minimized through the solution process, and the accuracy of the result is ensured to the utmost.
Second, the valve design of the stress concentration method application example In the actual valve design work, the selection of the correct stress concentration analysis method can effectively promote the accuracy of stress concentration analysis. This paper takes a gate valve as an example to compare and analyze the application process and effect of three different stress concentration analysis methods.
(I) Model establishment According to the structural design of the gate valve in the design drawing, the analysis model is established by using the 3D solid software PRO/E, and the seamless connection between PRO/E and ANSYS is established at the same time, so as to realize the establishment of the finite element analysis model.
(II) Meshing of gate valve model In order to ensure the accuracy of the analysis results, it is necessary to carry out the necessary structural division of the simulation structure. Here, the second-order unit with intermediate nodes is used to realize the division of the model structure. The second-order unit includes a plurality of tetrahedral elements. These unit structures have strong fitting functions, can realize effective connection between different units in a complicated structure, and can also improve the accuracy of simulation results. In this study, based on the structural symmetry theory as the basic research basis, a comprehensive analysis of the gate valve model was carried out.
(III) Stress concentration analysis of gate valve According to the application requirements of the mesh refinement method, the grid valve is refined by the standard of 20 for the gate valve model, and the size of the rough model applied in the sub-model technology is also 20, the adaptive grid The smallest grid unit is 10, the largest iteration is set to 100, and the structural error is 5%. Three sets of stress effect data were obtained by three different meshing and analysis methods, namely 286, 271, and 273. It can be seen that the mesh refinement method is the best, but the other two methods are relatively cumbersome in terms of simulation and meshing, and there are also different degrees of error in the simulation results.
Third, the impact of stress concentration accuracy on valve design The analysis results of valve stress concentration have an important impact on the reliability of valve design. Stress concentration analysis results can provide detailed data basis for valve design and manufacturing, which can not only promote product design. Scientific, but also to ensure the best performance of the valve body and extend the service life of the valve. In the actual stress concentration analysis process, it is necessary to distinguish the characteristics of the stress concentration distribution according to the different use requirements of the valve, in order to ensure the reliability of the stress concentration analysis result, thereby promoting the scientific design of the valve.
IV. Conclusion Through the analysis of this paper, it can be seen that under the same conditions, the local refinement method can more fully simulate the actual situation of valve body stress concentration. At the same time, this method can also be used to simulate other problems with large gradient changes, and obtain better results. In the actual operation process, the operation of the local refinement method is very simple, and only the nodes and units with large gradient changes need to be encrypted to realize the simulation process. If the result of the encryption does not meet the desired requirements, the level of encryption can be increased until it is qualified. In summary, for the study of stress concentration in valve design, the application of local refinement method can achieve the desired effect.
Analysis of mechanical valve design
[Abstract] The stress concentration problem involved in valve design is an important factor affecting the design parameters of valve products. Therefore, the related research on stress concentration is increasing. Stress concentration refers to the sudden change of geometry and shape under the influence of external force conditions, which causes a significant increase in stress in the local range. It is prone to stress concentration, mostly at the sharp corners of the object. Location and other locations with rigid constraints. Stress concentration is also a common phenomenon in valve product design. How to scientifically calculate the stress concentration of the valve through scientific calculation, so as to obtain the ideal calculation result, apply it to the valve design, and improve the efficiency of valve design. It is an important issue currently facing. This article focuses on the issues related to stress concentration in valve design.