Gear bending stress calculation method based on finite element software

Abstract

The invention belongs to the field of technical simulation, relates to a gear bending stress calculation method based on finite element software, and aims to find out structural design weak points and provide a basis for optimal design of a structure and improvement of product reliability. The method comprises the following steps: 1) determining the working load of the gear; 2) for the gear in the step 1), establishing a three-dimensional assembly entity model for gear contact analysis by using three-dimensional modeling software; 3) for the three-dimensional solid model of the gear in the step 2), establishing a two-dimensional assembly solid model of gear contact analysis by using three-dimensional modeling software; (4) according to the gear two-dimensional assembly entity model in the step (3), finite element software with a gear bending stress analysis function is imported, a finite element model is established, and boundary conditions are applied; and 5) according to the finite element model in the step 4), calculating and displaying a calculation result, and checking whether the gear meets the strength design requirement or not. The method is suitable for gear transmission system design.

Description

Technical Field

[0001] The invention belongs to the field of technical simulation and relates to a method for calculating gear bending stress in a gear design process. Background Art

[0002] When the gear transmission is subjected to various alternating loads during operation, if the bending strength of the gear is insufficient, the tooth surface will suffer pitting, spalling, plastic deformation and other damages. Simulation analysis is an important part of gear design. It can timely discover the weak links in the design at the early stage of product design, thereby providing data support for the optimization design of the structure, improving product reliability, and shortening the product development cycle. Therefore, it is necessary to simulate the gear to obtain the distribution of stress and bending stress at the root of the gear teeth, so as to provide a theoretical basis for the structural optimization and reliability analysis of the gear.

[0003] At present, the calculation methods for gear stress in China are mainly calculated through theoretical formulas, experiments and simulations. Traditional gear strength analysis is based on empirical formulas. The design theory is not perfect, many factors are ignored, and the calculation results have large deviations. Its limitations and uncertainties are becoming increasingly prominent. The bending stress of the gear can also be obtained by general test methods, but it can only be carried out after the product design is completed. It cannot predict the weak links of the structure in advance, and the test cost is high and the cycle is long. The finite element simulation method has been used to obtain the stress of the gear in engineering, but there is still a lack of a complete set of gear meshing analysis processes. The steps from simulation modeling, meshing to load application are not standardized and comprehensive enough. Summary of the invention

[0004] The technical problem to be solved by the present invention is to propose a gear bending stress calculation method based on finite element software to find out the weak points of structural design and provide a basis for optimizing the design of the structure and improving product reliability.

[0005] The technical solution of the present invention is

[0006] A method for calculating gear bending stress based on finite element software, comprising:

[0007] 1) Determine the gear working load;

[0008] 2) For the gear in step 1), a three-dimensional assembly solid model for gear contact analysis is established using three-dimensional modeling software;

[0009] 3) For the gear 3D solid model in step 2), a 2D assembly solid model for gear contact analysis is established using 3D modeling software;

[0010] 4) According to the gear two-dimensional assembly solid model in step 3), the finite element software with gear bending stress analysis is imported to establish a finite element model and apply boundary conditions;

[0011] 5) According to the finite element model in step 4), solve and display the calculation results to check whether the gear meets the strength design requirements.

[0012] The step 2) establishes a three-dimensional assembly solid model of the gear, establishes the gear side clearance according to the actual situation of the drawing, assembles the driving gear and the driven gear together, and the model has no interference and no free state, ensuring that the model meets the requirements of the drawing.

[0013] The step 3) establishes a two-dimensional gear assembly solid model, simplifies the model, and removes the middle gear shaft.

[0014] In the step 4), a finite element model is established, local mesh refinement is performed on the tooth surfaces that are meshing with each other and about to enter the meshing area, and coarse mesh division is performed on other positions.

[0015] In the step 4), a finite element model is established, a contact pair is defined, and the contact edges of the driving gear and the driven gear and the contact edges about to enter the meshing area are selected as the contact edges and the target edges respectively; the contact type is selected as friction contact, and the friction coefficient is defined.

[0016] In step 4), boundary conditions are applied. The degree of rotation applied by the driving gear is the number of gear tooth angles rotated by the gear. The larger the angle, the more gear teeth are rotated, and the closer the gear meshing is to stability. The first load step of the load is 0°, and the second load step is the degree of rotation required to be applied. The driven gear is applied with a counter-torque load, and the load size is the gear working load calculated in step 1), and the direction is the same as the angular load of the driving gear.

[0017] The step 5) solves and displays the calculation results, stress, deformation, gear stress change curve over time, and extracts the maximum stress in the stable state after the gear meshes according to the stress curve.

[0018] The step 1) of determining the gear working load comprises:

[0019] Analyze the working state of the gears and determine the transmission power and speed of the driving gear and the driven gear. For the three pairs of meshing gears, it is necessary to determine the power output of each output gear and calculate the output gear torque as the gear working load. The gear torque calculation formula is as follows:

[0020] T=9549*P / n

[0021] T——output gear torque N·m;

[0022] P——output power, kW;

[0023] n——output gear operating speed, r / min.

[0024] The beneficial effects of the present application are: by adopting the gear bending stress calculation of the above process, a structural simulation model consistent with the engineering design is established, and by adopting the gear two-dimensional plane stress dynamic simulation calculation, the bending stress, deformation and stress change curves of the gear are obtained, which more intuitively reflects the design weaknesses of the gear and optimizes and improves them, thereby effectively avoiding damage caused by gear design defects during testing or working processes.

[0025] This technical solution has been applied to a large number of gear design analyses and has been fully verified through experiments. It is technically feasible and has reliable results, effectively avoiding damage caused by gear design defects during testing or working processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a three-dimensional model for gear contact calculation of the present invention.

[0027] Figure 2 It is a schematic diagram of a two-dimensional model for gear contact calculation of the present invention. DETAILED DESCRIPTION

[0028] The present application is further described in detail below in conjunction with the accompanying drawings of the embodiments.

[0029] like Figure 1 , 2 As shown, the present invention provides a method for dynamic calculation of two-dimensional plane stress of gears based on finite element software with gear bending stress analysis, and uses numerical simulation method to simulate the bending stress of newly designed gears to find out the weak points of structural design, and provide a basis for optimizing the design of the structure and improving product reliability. To solve this technical problem, the technical solution provided by the present invention is:

[0030] 1) Analyze the working condition of the gear and determine the limit torque load.

[0031] 2) According to the two-dimensional gear drawing, establish a gear solid model in the three-dimensional modeling software, and establish the gear side clearance according to the actual situation in the drawing. Assemble the driving gear and the driven gear together, and the model has no interference and no free state; simplify the three-dimensional model, remove the middle shaft, and establish a two-dimensional model.

[0032] 3) Import the gear 2D model from step 2) into the finite element software, establish two mass points at the center of the driving gear and the driven gear, define the mass of the mass points, and set the state to rigid; define the material of the components, set the contact parameters, divide the mesh, and generate the finite element model. The material parameters include: density, elastic modulus, Poisson's ratio, and the yield limit and shear modulus need to be defined for elastic-plastic analysis.

[0033] 4) Define the load step of the finite element model in step 3) as 2, the number of sub-steps as 200, and enable large deformation; constrain the displacement of the center position of each gear in the X and Y directions to 0; apply a rotation angle to the driving gear mass point, and apply a counter-torque load to the driven gear mass point. The counter-torque load is equal to the limit torque load in magnitude and opposite in direction.

[0034] 5) Solve and display the calculation results, and extract the maximum stress in the stable state after gear meshing.

[0035] 6) Based on the strength calculation results of step 5), the gear root stress is checked according to the gear bending strength verification standard.

[0036] Furthermore, the working state of step 1) includes the transmission power and speed of the driving gear and the driven gear. For three pairs of meshing gears, it is necessary to determine the power output of each output gear and calculate the torque. The torque calculation formula is as follows:

[0037] T=9549*P / n

[0038] T——output gear torque N·m;

[0039] P——output power, kW;

[0040] n——output gear operating speed, r / min.

[0041] Furthermore, in the step 2), the two-dimensional model is established as a sheet body, and the "extract geometric features" command is used in the three-dimensional modeling software to establish a two-dimensional model for gear meshing calculation.

[0042] In the step 3) meshing, local meshing is performed on the tooth surfaces that are meshing with each other and about to enter the meshing area, and rough meshing is performed on other positions.

[0043] In step 3) contact parameter setting, the contact edge of the driving gear and the driven gear and the contact edge about to enter the meshing area are selected as the contact edge and the target edge respectively. The contact type is selected as friction contact, and the friction coefficient is defined.

[0044] In step 4), the degree of rotation applied by the driving gear is the degree of rotation of the gear through n gear tooth angles. The larger the angle, the more gear teeth are rotated, and the closer the gear meshing is to stability. The first load step of the load is 0°, and the second load step is the degree of rotation required to be applied.

[0045] In step 4), the driven gear is subjected to a counter torque load, the load magnitude of which is the torque load calculated in step 1), and the direction of which is the same as the angular load of the driving gear.

[0046] The calculation results of step 5) include stress, deformation, and gear stress variation curves over time.

[0047] In the step 5), the gear contact is calculated, and the stress calculation results are checked. When the calculation results are unreasonable or the calculation does not converge, the process returns to the steps 2), 3) and 4), the calculation model, contact and boundary strips are checked, and the simulation calculation is repeated.

[0048] The finite element software with gear bending stress analysis is specifically Workbench software.

[0049] Under the condition of obtaining the same calculation result accuracy, this method has a smaller calculation model, higher mesh accuracy and higher calculation efficiency than the three-dimensional analysis method; this method obtains more accurate stress results than three-dimensional analysis, avoids uneven stress distribution caused by inaccurate three-dimensional model, and reduces calculation repetitions caused by inaccurate geometric model.

Claims

1. A method for calculating gear bending stress based on finite element software, characterized in that: include: 1) Determine the gear working load; 2) For the gear in step 1), a three-dimensional assembly solid model for gear contact analysis is established using three-dimensional modeling software; 3) For the gear 3D solid model in step 2), a 2D assembly solid model for gear contact analysis is established using 3D modeling software; 4) According to the gear two-dimensional assembly solid model in step 3), the finite element software with gear bending stress analysis is imported to establish a finite element model and apply boundary conditions; 5) According to the finite element model in step 4), solve and display the calculation results to check whether the gear meets the strength design requirements.

2. A method for calculating gear bending stress based on finite element software as claimed in claim 1, characterized in that: The step 2) establishes a three-dimensional assembly solid model of the gear, establishes the gear side clearance according to the actual situation of the drawing, assembles the driving gear and the driven gear together, and the model has no interference and no free state, ensuring that the model meets the requirements of the drawing.

3. A method for calculating gear bending stress based on finite element software as claimed in claim 1, characterized in that: The step 3) establishes a two-dimensional gear assembly solid model, simplifies the model, and removes the middle gear shaft.

4. A method for calculating gear bending stress based on finite element software as claimed in claim 1, characterized in that: In the step 4), a finite element model is established, local mesh refinement is performed on the tooth surfaces that are meshing with each other and about to enter the meshing area, and coarse mesh division is performed on other positions.

5. A method for calculating gear bending stress based on finite element software as claimed in claim 4, characterized in that: In the step 4), a finite element model is established, a contact pair is defined, and the contact edges of the driving gear and the driven gear and the contact edges about to enter the meshing area are selected as the contact edges and the target edges respectively; the contact type is selected as friction contact, and the friction coefficient is defined.

6. A method for calculating gear bending stress based on finite element software as claimed in claim 1, characterized in that: In step 4), boundary conditions are applied. The degree of rotation applied by the driving gear is the number of gear tooth angles rotated by the gear. The larger the angle, the more gear teeth are rotated, and the closer the gear meshing is to stability. The first load step of the load is 0°, and the second load step is the degree of rotation required to be applied. The driven gear is applied with a counter-torque load, and the load size is the gear working load calculated in step 1), and the direction is the same as the angular load of the driving gear.

7. The method for calculating gear bending stress based on finite element software according to claim 1, characterized in that: The step 5) solves and displays the calculation results, stress, deformation, gear stress change curve over time, and extracts the maximum stress in the stable state after the gear meshes according to the stress curve.

8. The method for calculating gear bending stress based on finite element software according to claim 1, characterized in that: The step 1) of determining the gear working load comprises: Analyze the working state of the gears and determine the transmission power and speed of the driving gear and the driven gear. For the three pairs of meshing gears, it is necessary to determine the power output of each output gear and calculate the output gear torque as the gear working load. The gear torque calculation formula is as follows: T=9549*P / n T——output gear torque N·m; P——output power, kW; n——output gear operating speed, r / min.

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