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1 3D solid modeling of gears Compared to its sophisticated analysis functions, ANSYS's solid modeling capabilities are relatively poor, but ANSYS software provides interfaces to other CAD software (such as Pro/E, UG, AutoCAD, MDT). Models created in other CAD software can be imported into ANSYS through a certain file format. Pro/E is a set of mechanical automation software from design to production. It is a parametric, feature-based solid modeling system with a single database function, which can quickly realize 3D solid modeling. Therefore, the software is used to perform 3D solid modeling work. The gear parameters analyzed are as follows: gear speed n=303.1r/min, transmission power P=10.406kW, gear tooth number z=35, modulus m=3.5, pressure angle=20, tip height coefficient ha=1, head clearance Coefficient C=0.25, tooth width B=130mm.
When calculating the root stress and tooth deformation by finite element analysis, if all the teeth are selected as the research object, the number of divided units is large, the computer calculation is large, and the time is long, but the influence on the accuracy of the calculation results is affected. It is very small. Therefore, a single tooth model is selected here as the research object. When the gear teeth are loaded, the gear body cannot be absolutely rigid, and the tooth tooth is also deformed. It is generally considered that when the depth from the tooth root reaches 1.5 times the modulus, the boundary width of a single gear is greater than 6 times the modulus. Unaffected, the actual displacement at that location can be regarded as zero, so the boundary width of a single tooth is set to 6 times the modulus, so only the gear body close to the root portion is selected as the research object. In the Pro/E software, the three-dimensional model of the built gear is shown in Fig. 1, and the single tooth model used in the analysis is shown in Fig. 2.
2 Finite Element Modeling and Analysis of Gears 2.1 Finite Element Modeling of Gears The gear tooth model built in Pro/E is saved as. Igs format, set the material properties after importing ANSYS. The material of the gear is isotropic material, material density=7800kg/m3, elastic modulus E=2.06e5MPa, Poisson's ratio=0.3. Since SOLID95 is a 20-node hexahedral element with intermediate nodes, the adaptability to the shape of the member is better. Well, the calculation accuracy is high. Now the SOLID95 unit is used to mesh the surface of the gear teeth with coarse and partial subdivision, and then the surface with the mesh is stretched into a body with a mesh. The number of units is 51744. The resulting single-tooth finite element model is shown.
2.2 Determining the Constraint Condition and the applied load gear are coupled to the shaft by a key, and the gear is rotated together with the shaft by external input torque. When the constraint is applied, it can be considered that the moment of the gear is fixed, and the static analysis is applied to the gear, so the boundary between the two sides of the tooth is symmetrically constrained, and the bottom of the tooth is fixed by the fixed end.
The force of the gear during the meshing process varies along the contact line. The traditional gear design theory is similar to seeing the force acting on the indexing circle and acting on one point. In fact, the gear teeth are in the process of transmission. It is subjected to the distribution line load, and the loading of the teeth, from the safety point of view, applies a normal load on the top of the addendum circle. According to the theoretical calculation results, a pressure of 68.23 MPa was applied to a facet of 0.9 mm from the top of the tooth.
2.3 Gear finite element calculation results and analysis After the constraints and loads are applied to the gear teeth, the powerful solution function of ANSYS software can be used to solve the stress and strain of each node and reflect it on the solid model through different colors. The calculated results can be seen from the stress map and the strain map. For the deformation of the gear teeth, it can be seen that the gear teeth are obviously bent and deformed, and the maximum deformation displacement generated by the gear teeth is about 0.01781 mm. It is the stress magnitude of the teeth and the joints of the gear teeth and the maximum and minimum stress values ​​of the gear teeth. The minimum stress is 0.053863MPa, the maximum stress is 58.536MPa, and the maximum root stress is 33.267MPa. It can be seen from the equivalent stress distribution diagram that the stress at the top of the tooth is the largest, which is due to the contact stress generated by the load on the top of the tooth; It can be seen that the nodes near the tooth root transition curve on both sides of the gear teeth have obvious stress concentration.
3 Conclusions The 3D solid model of involute cylindrical gears was established by using 3D CAD. The finite element analysis of the gear teeth was carried out by using the large-scale general analysis software ANSYS. The deformation map and stress cloud diagram of the gear teeth were obtained. It can be seen that A large contact stress is generated at the applied load, and the nodes near the root-to-root transition curve have a significant stress concentration phenomenon, which easily causes the gear to break during the meshing process. In view of the severe stress on the root of the tooth, the root force can be relieved by increasing the radius of the root transition.
The finite element method can be used to analyze the deformation and stress of various parameter gears under various working conditions, which reflects the shortcomings of the parts in the design. This not only provides a reference for optimizing gear construction, tooth profile and profile, but also provides the basis for optimizing gear materials and processes for innovative design of gear structures, materials and processes.
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