Permanent deformation of toe end after residual de

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The influence of the heel shape of the fastener on the permanent deformation value of the toe end after the residual deformation test

elastic strip type III fastener is used to connect 60kg/m rail and type III prestressed concrete sleeper without shoulder on heavy haul, fast, high-speed railways with standard gauge and lines with a curve radius of not less than 350m. With the development of our national economy and the continuous improvement of railway transportation speed, the requirements of railway fastener elasticity, vibration reduction effect and buckle pressure stability are also continuously improved. Therefore, the buckling pressure stability of elastic bar type III fastener when assembled in standard state is the key quality characteristic. After the residual deformation test, the permanent deformation value of the toe end of the elastic strip shall not be greater than 1 0mm is the key technical index (see Figure 1 for the installation form of elastic strip type III fastener and Figure 2 for the geometric dimension of elastic strip). Our company carried out technological trial production of elastic bar type III fasteners in 2001, which passed the acceptance of the expert group of the Ministry of Railways in the same year and began mass production

1. The processing technology of elastic strip type III fastener is: blanking, heating, bending, forming and heat treatment. According to the above production process, we have produced elastic strip type III fasteners. In the residual deformation test of finished products, sometimes the permanent deformation value of toe end is greater than 1 0mm. As this is a key technical index, its disqualification will directly affect the safety of train operation and bring hidden dangers to railway transportation, so it has attracted our great attention. Therefore, we have conducted in-depth analysis and Research on unqualified products. In the residual deformation test of type III fastener, the permanent deformation value of toe end is determined by the heat treatment quality and geometric dimension of the product. We have tested the hardness of unqualified products, and the hardness meets the design requirements (44 ~ 48 HRC). It can be seen that there is no problem in the heat treatment process. Therefore, the preliminary judgment is caused by the problem of its geometric size. 3. After the strengthening stage passed the yield stage, and we found that the products that failed the residual deformation test generally had heel end lateral bending (see Figure 3). Therefore, we analyze the influence of toe shape of elastic strip type III fastener on the permanent deformation value of residual deformation test

2. Establish three-dimensional solid models of different heel end shapes of elastic bar type III fasteners

in order to accurately analyze the influence of heel end shape of elastic bar type III fasteners on the permanent deformation value of toe end in residual deformation test, it is necessary to carry out structural analysis on it in Engineering mechanics. Before the structural analysis, the three-dimensional solid model of the product must be established. Due to the poor modeling function of some professional structural analysis software, we use pro/eng neer software platform to establish three-dimensional solid models. Pro/engineer software is a product launched by PTC (para metric Technology Corporation) in 1989. It is a cad/cae/cam software system for three-dimensional design, processing, analysis and drawing of products. The software is famous for its convenient use, parameterized feature modeling and full correlation of the system. At present, pro/engineer software has been widely used in China's electronics, home appliances, mold, welding and other industries. It is one of the software with the largest number of users of foreign cad/CAM software in China

The parameterization technology first proposed by pro/engineer software is called the third technological revolution in the history of CAD technology. With the characteristics of powerful parametric design and unified database management, he has realized the size drive of features, the bidirectional correlation drive between 3D entities and 2D engineering drawings, solid feature modeling, component assembly, NC machining and other functions, overcoming the shortage that 2D graphics cannot contain all the design information of products. In order to facilitate future analysis, we have established two models (see Figure 4 and figure 5), We call the qualified product (the hydraulic testing machine is a set of 3-position full-automatic unit, including steel pipe washing, pressure test, drift diameter, etc., which can complete the pressure test and drift diameter detection of oil pipes and casings with or without couplings, ribbed or non ribbed tail, and automatic sorting of unqualified steel pipes. The maximum experimental pressure of the oil-cooled electric drum is 100MPa, the pressure test pipe diameter range is 60.3 ~ 177.8 (238 ″ ~7 ″), and the coupling is 73 ~ 194.5, The length range of pressure test pipe is 6~12.7m See Figure 4) for clip-3; The unqualified product (see Figure 5) is clip-, and the difference between the two is the shape of the heel end (see Figure 6 and Figure 7)

3. Structural analysis of the product

due to the complex structure of the product, we conducted a structural analysis of the above model based on the ANSYS software platform. With the development of computer and calculation methods, complex engineering problems can be solved by discrete numerical calculation technology and computer. Numerical simulation technology is one of the important driving forces for the formation and development of poor performance of modern engineering. At present, the most widely used numerical simulation method in the engineering field is the finite element method. The finite element calculation results have become a reliable basis and effective means for the design and performance analysis of various industrial products. ANSYS software is a large general finite element software that integrates structure, heat transfer, fluid and electromagnetism. It is only willing to take some small equipment products for water test, acoustic and blasting analysis. Its developer ANSYS company is one of the most famous companies in the CAE industry in the world, and has been committed to the development and research of design and analysis software for a long time. Many international companies use ANSYS software as their design and analysis standard, which has a wide range of users all over the world. ANSYS software has become one of the most effective software in the field of computer-aided engineering and engineering numerical simulation

first, we import the 3D solid model established in pro/engineer environment into ANSYS software environment, and then establish boundary conditions for calculation. In the residual deformation test, because the product produced a small amount of plastic deformation, we used the von Mises yield criterion in the plastic theory:

that is, we used nonlinear elastoplastic static structural analysis. The analysis steps are: establishing a geometric model, defining material properties, element related properties, dividing grids, imposing constraints and loads, and finally solving. Through the analysis of the above steps, the following von Mises equivalent stress nephogram is obtained (see Fig. 8, FIG. 9, FIG. 10 and FIG. 11). Compared with the von Mises equivalent stress nephogram results, the clip-3 maximum stress distribution area is smaller, and the clip maximum stress distribution area is larger

clip-3 the maximum strain value is 0 002805mm, clip- the maximum strain value is 0 00347mm。 Then compare the results of von Mises plastic string cloud chart (see Figure 12 and figure 13). Through the above analysis, it is concluded that the plastic deformation of clip- is greater than clip-3, which makes the permanent deformation value of clip toe end unqualified after the residual deformation test

4. The permanent deformation values of clip-3 and clip residual deformation test toes are compared in the residual deformation test, as shown in the table below

it can be seen from the data in the table that the permanent deformation value of clip-3-1 residual deformation test toe end is greater than 1 0mm, the product is unqualified. The permanent deformation value of the toe of lip-3 residual deformation test is less than 1 0mm, the product is qualified

5. Conclusion

in the production process of elastic bar type III fastener, the product heel end is laterally bent due to production process problems, which makes the maximum stress distribution area and the maximum strain value larger during the use of elastic bar type III fastener, thus causing the permanent deformation value of toe end of residual deformation test of elastic bar type III fastener to be unqualified. Therefore, we have improved the production process accordingly, strictly controlled the shape of the heel end, ensured its lateral straightness and no lateral bending, and better solved the problem that the toe end permanent deformation value of the elastic bar type III fastener was unqualified in the residual deformation test, ensured its buckling performance, and eliminated the hidden danger of train operation

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