Simulation method and simulation APP for rapidly evaluating fatigue of main shaft of tubular unit and simulation APP development method

Abstract

The invention relates to the technical field of water-turbine generator set design, and discloses a simulation method, a simulation APP and a simulation APP development method.During simulation, firstly, a main shaft part library is called, main shaft basic parts are selected from the main shaft part library, and part attribute parameter values are given to the main shaft basic parts; then leading the basic parts of the main shaft into a finite element analysis model to form a three-dimensional model of the main shaft, adding the load and constraint of the model by using a main shaft load module, assigning a main shaft material and dividing a structured grid, and finally obtaining the bending stress and the torsion stress of a dangerous section of the model; then, a main shaft fatigue strength module is used for calculating the fatigue strength safety coefficient of the main shaft three-dimensional model under the conditions of the symmetric cyclic stress load, the asymmetric cyclic stress load and the bending-torsion combined load based on the fatigue strength mathematical model; and finally, outputting a fatigue strength safety coefficient calculation result in a chart form. The main shaft fatigue strength safety data can be quickly obtained, the labor cost is reduced, and the efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hydro-turbine generator set design, and in particular to a simulation method, a simulation APP and a simulation APP development method for quickly evaluating the fatigue of a main shaft of a tubular unit. Background Art

[0002] In a tubular turbine, the main shaft is the main component for transmitting loads, and its fatigue life directly determines the service life of the generator set. The main shaft of a tubular unit adopts a horizontal structure layout, which has the characteristics of a single structure and fixed load and constraint positions. During normal operation, it is subjected to loads such as gravity in the vertical direction, and the bending stress it bears is a symmetrical cyclic stress; it is subjected to loads such as water thrust in the axial direction of the main shaft, and the axial force it bears is an asymmetrical cyclic stress; it is subjected to loads such as torque in the circumferential direction of the main shaft, and the torsional shear stress it bears is an asymmetrical cyclic stress. The stress conditions of the main shaft of a tubular unit are complex, and fatigue analysis is cumbersome and difficult.

[0003] At present, the main shaft stress is calculated mainly through the finite element method, and then the fatigue safety factor is obtained through the fatigue formula calculation method. In the finite element simulation process, the first step is to establish a three-dimensional model for the main shaft that needs to be subjected to stress and fatigue analysis; the second step is to add the load and boundary conditions one by one; the third step is to extract the bending stress of the key and dangerous positions; the fourth step is to obtain the stress concentration factor, surface quality factor, size factor and other related parameters of the dangerous area according to the calculation results and processing technology; the fifth step is to calculate the fatigue safety factor through the fatigue strength calculation formula under symmetrical cyclic loads; the sixth step is to compare the fatigue safety factor of each dangerous area with the specified safety factor, and finally determine whether the fatigue requirements are met. Therefore, the existing fatigue analysis method of the main shaft of the cross-flow unit has problems such as being cumbersome, mechanical, and the result output is not intuitive. Summary of the invention

[0004] In order to solve the problems and shortcomings existing in the above-mentioned prior art, the present invention specifically proposes a simulation method, a simulation APP and a simulation APP development method for quickly evaluating the fatigue of the main shaft of a cross-flow unit. The present invention only needs to complete the creation of the geometric model and the input of the load to quickly obtain the main shaft fatigue strength safety data, which greatly reduces the labor cost and also improves the fatigue simulation efficiency.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0006] First, the present invention discloses a simulation method for quickly evaluating the fatigue of a main shaft of a tubular unit. The simulation method mainly includes the following steps:

[0007] The first step is to start the simulation APP, then call the spindle parts library in the APP, select the corresponding spindle basic parts from the parts library, and then assign specific attribute parameter values ​​to each spindle basic part. The structural form of the spindle basic parts is as follows Figure 1 As shown in (a)-1(d), the main shaft basic parts can be quickly assembled into a three-dimensional model of a cross-flow unit main shaft of any size and shape.

[0008] In the present invention, the spindle basic part attribute parameter values ​​include part size, part dangerous area and geometric features of the part dangerous area, load boundary and constraint boundary.

[0009] The critical area of ​​the spindle base part is usually the chamfer transition area. Furthermore, the subsequent fatigue calculation requires the geometric parameters of the critical area of ​​the base part, such as the radius of the section, the size of the chamfer, the radius of the through hole, the stress concentration factor of the critical area, etc.

[0010] In the second step, the assigned spindle basic parts are imported into the finite element analysis model to form a three-dimensional spindle model. Figure 2 As shown; then use the spindle load module in the simulation app to add the load and constraints of the spindle 3D model, specify the spindle material, and divide the model structured grid, as shown Figure 3 As shown; the spindle load module is embedded with the calculation formulas for the bending stress and torsional stress of the dangerous section of the spindle three-dimensional model. According to the added load size, constraint form and spindle material, the bending stress and torsional stress of the dangerous section of the spindle three-dimensional model can be calculated.

[0011] In the present invention, the dangerous section is in the dangerous area. Usually, there are many chamfered positions on a unit main shaft, corresponding to multiple dangerous areas, and each dangerous area has a most dangerous section, which is generally at the connection between the chamfer and the cylindrical surface of the shaft.

[0012] In the third step, the spindle fatigue strength module in the simulation software is used to calculate the fatigue strength safety factor of the spindle three-dimensional model under symmetrical cyclic stress load, asymmetrical cyclic stress load and bending-torsion combined load conditions based on the bending stress and torsional stress of the dangerous section of the spindle three-dimensional model calculated in the second step.

[0013] In the present invention, the fatigue strength mathematical model includes a symmetrical cyclic stress load fatigue strength mathematical model, an asymmetrical cyclic stress load fatigue strength mathematical model and a bending-torsion combined load fatigue strength mathematical model; wherein, the symmetrical cyclic stress load fatigue strength mathematical model is embedded with a fatigue strength safety factor calculation formula of symmetrical cyclic stress, the asymmetrical cyclic stress load fatigue strength mathematical model is embedded with a fatigue strength safety factor calculation formula of asymmetrical cyclic stress, and the bending-torsion combined load fatigue strength mathematical model is embedded with a bending-torsion combined load fatigue strength safety factor calculation formula. Moreover, it is worth mentioning that the main shaft fatigue strength module also has a built-in fatigue strength mathematical model parameter table, including stress concentration factor, size factor and other parameters related to the formula calculation. When calculating the fatigue strength safety factor of the main shaft three-dimensional model, the model parameter table is called according to the geometric characteristics of the key and dangerous sections, and the relevant calculation parameters are automatically read for the fatigue strength coefficient calculation of the model.

[0014] Specifically, the main calculation formulas involved in the fatigue strength mathematical model are as follows:

[0015] (1) Calculation formula for fatigue strength safety factor of symmetrical cyclic stress:

[0016]

[0017] (2) Calculation formula for fatigue strength safety factor of asymmetric cyclic stress

[0018]

[0019] (3) Calculation formula for bending-torsion combined fatigue safety factor:

[0020]

[0021] Among them, n σ and n τ The fatigue strength safety factors of symmetrical cyclic stress and asymmetrical cyclic stress are respectively; σ and ε τ is the size factor; β is the surface quality factor; σ -1 and τ -1 is the fatigue limit; K σ and K τ is the stress concentration factor; σ max is the maximum stress; τ a is the mean torsional stress; τ m is the torsional stress amplitude; is the asymmetric sensitivity factor; n f is the specified value of fatigue strength coefficient; n στ is the combined fatigue factor of bending and torsional fatigue.

[0022] Step 4. Finally, the fatigue strength safety factor calculation results of the main shaft three-dimensional model and the fatigue strength safety factor specified value are plotted in the same chart and output, such as Figure 4 The horizontal axis of the chart is the danger zone or the key focus area, and the vertical axis is the calculated fatigue strength safety factor. The calculated value of the fatigue strength safety factor of the main shaft three-dimensional model in the chart is compared with the specified value to determine whether the fatigue strength and performance of the current main shaft three-dimensional model meet the requirements.

[0023] The present invention can intuitively and quickly analyze and compare the fatigue condition of the main shaft structure of the current unit through the drawn chart, judge whether the structural design is reasonable, and thus provide guidance for the design of the main shaft of the tubular generator unit.

[0024] Based on the same inventive concept, the present invention also discloses a simulation APP for quickly evaluating the fatigue of the main shaft of a tubular unit. The APP is used to implement the above simulation method, including:

[0025] The spindle parts library is configured to define the attribute parameter values ​​of the spindle basic parts constituting the spindle of the unit based on the basic structural form of the spindle of the unit;

[0026] The spindle load module is configured to add the load and constraint of the model, specify the spindle material and divide the structured mesh based on the spindle three-dimensional model to obtain the bending stress and torsional stress of the dangerous section of the spindle three-dimensional model;

[0027] The spindle fatigue module is configured to calculate the fatigue strength safety factor of the spindle three-dimensional model under symmetrical cyclic stress load, asymmetrical cyclic stress load and bending-torsion combined load conditions based on the bending stress and torsional stress of the dangerous section of the spindle three-dimensional model using a fatigue strength mathematical model; and output the calculation results of the fatigue strength safety factor of the spindle three-dimensional model in the form of a chart.

[0028] Furthermore, the present invention discloses a method for developing a simulation APP for quickly evaluating the fatigue of a main shaft of a tubular unit. The method is used to develop the above simulation APP. The method is based on the secondary development tool of COMSOL Multiphysics software, namely COMSOL Compiler TM On the secondary development tool, a spindle parts library, a spindle load module, and a spindle fatigue module are created. Finally, the above modules are compiled through COMSOL Compiler. TM Compiled into a simulation APP for rapid assessment of the fatigue of the main shaft of the tubular unit, it becomes an independently running application. The operation interface of the simulation APP is as follows Figure 5As shown in the figure, the spindle basic parts in the spindle parts library are called to quickly assemble the spindle three-dimensional model, and then the spindle load module is called to add corresponding loads and constraints to the spindle three-dimensional model, specify the spindle material and divide the structured grid, and then calculate the bending stress and torsional stress of the dangerous section; finally, click to call the spindle fatigue module, and calculate the fatigue strength safety factor of the spindle three-dimensional model through the built-in model parameter table and fatigue strength mathematical model, and then output and display the calculation results in the form of charts.

[0029] Preferably, the simulation APP development method specifically includes the following steps:

[0030] Step A, parametric modeling is used to establish spindle basic parts, attribute parameters are assigned to each spindle basic part, the spindle basic parts are compiled into a built-in parts library of COMSOL Multiphysics software, and a spindle parts library is created thereby;

[0031] Step B, writing the load and constraint of the three-dimensional model of the main shaft, the main shaft material, the grid structure division, and the bending stress and torsional stress calculation formula of the dangerous section into the calculation program of COMSOL Multiphysics software, thereby creating a main shaft load module;

[0032] Step C, writing the fatigue strength safety factor calculation formula corresponding to the symmetrical cyclic stress load, the fatigue strength safety factor calculation formula corresponding to the asymmetrical cyclic stress load, and the fatigue strength safety factor calculation formula corresponding to the bending-torsion combined load into the program of COMSOL Multiphysics software, thereby creating a spindle fatigue module;

[0033] Step D: Integrate the spindle parts library, spindle load module, and spindle fatigue module into COMSOL Compiler TM The program is developed on a developer and finally compiled into an independently running simulation APP for quickly evaluating the fatigue of the main shaft of a tubular unit.

[0034] Beneficial effects of the present invention:

[0035] 1. The present invention combines a plurality of basic parts into a tubular unit spindle parts library, and directly calls the parts in the parts library to combine a tubular unit spindle of any shape and any size, thereby completing the spindle modeling, and then performs simulation calculations in finite element simulation software based on the constructed model. The present invention uses a parts combination method to complete the three-dimensional modeling of the spindle, avoiding the modeling process from two-dimensional drawings to three-dimensional models, and can achieve the size control of the spindle model by changing the size parameters of the basic parts, and can achieve spindle modeling of different structures by calling different basic parts. Therefore, not only rapid modeling is achieved, but also the requirements of accurate modeling are met.

[0036] 2. The simulation APP development method used in the present invention predefines the load and constraint boundaries and maps them one by one with the load parameters. The grid uses a predefined default structured grid division scheme to ensure the accuracy and uniqueness of the calculation. The simulation modeling work of the present invention is highly integrated and interrelated, which optimizes the simulation modeling operation to the greatest extent.

[0037] 3. The present invention embeds the fatigue safety factor related formula of the main shaft of the cross-flow unit into the simulation model by means of embedded variables, and extracts the data required for fatigue analysis for formula calculation by means of predefined data output, thereby avoiding manual formula calculation and effectively simplifying the work.

[0038] 4. The present invention embeds relevant parameters into the model through secondary development, and automatically reads relevant parameters of the dangerous section through a method of predefining geometric features of the dangerous section, which greatly simplifies the fatigue analysis process.

[0039] 5. The present invention directly displays the fatigue safety factor of each dangerous section of the main shaft in the form of a chart, and the result is more intuitive, readable and visible.

[0040] 6. The simulation APP developed by the present invention greatly simplifies the fatigue analysis process of the main shaft of the cross-flow unit. It only needs to complete the creation of the geometric model and the input of the load to quickly obtain the main shaft fatigue safety data, which greatly reduces the labor cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The foregoing and following detailed description of the present invention will become more apparent when read in conjunction with the following drawings, in which:

[0042] Figure 1 (a)-1(d) are schematic diagrams of the basic parts of the spindle of the present invention;

[0043] Figure 2 It is a three-dimensional model of the main shaft after the tubular unit of the present invention is assembled;

[0044] Figure 3 It is a schematic diagram of the structured grid division of the three-dimensional model of the combined main shaft of the tubular unit of the present invention;

[0045] Figure 4 The calculation results of fatigue strength safety factor of each dangerous area of ​​the main shaft of the tubular unit of the present invention are shown in the table;

[0046] Figure 5 This is a diagram of the operation interface of the simulation APP of the present invention;

[0047] Figure 6 (a)-6(c) are schematic diagrams of fatigue analysis using a simulation APP in Example 1 of the present invention;

[0048] Figure 7 (a)-7(c) is a schematic diagram of fatigue analysis using a simulation APP in Example 2 of the present invention. DETAILED DESCRIPTION

[0049] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions for achieving the purpose of the present invention will be further described below through several specific embodiments. It should be noted that the technical solutions claimed for protection in the present invention include but are not limited to the following embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

[0050] Example 1

[0051] The embodiment of the present invention discloses a simulation method for quickly evaluating the fatigue of the main shaft of a tubular unit, and the method is implemented based on the simulation APP proposed by the present invention. Taking the domestic XX tubular unit as an example, first, the main shaft parts library in the APP is called, and four main shaft basic parts are selected and combined according to the main shaft drawing in the main shaft parts library to form a main shaft combination, and the main shaft three-dimensional model is obtained by setting the basic part size parameters, such as Figure 6 (a); then, call the spindle load module and input the spindle load, constraint and other parameters of the unit, such as Figure 6 (b) As shown; Finally, call the spindle fatigue module, click Calculate in the module, and obtain the fatigue strength safety factor curve of the spindle 3D model, as shown in Figure 6 (c) as shown.

[0052] Example 2

[0053] The embodiment of the present invention discloses a simulation method for quickly evaluating the fatigue of the main shaft of a tubular unit, and the method is implemented based on the simulation APP proposed by the present invention. Taking the domestic XXX tubular unit as an example, first, the main shaft parts library in the APP is called, four basic parts are selected according to the main shaft drawing to form a main shaft combination, and a three-dimensional main shaft model is obtained by setting the basic part size parameters, such as Figure 7 (a); then, call the spindle load module, and input the load, constraint, spindle material and other parameters of the unit spindle in the module, as shown in Figure 7 (b) As shown; Finally, call the spindle fatigue module, click Calculate in the fatigue module, and obtain the fatigue strength safety factor curve of the spindle three-dimensional model, as shown in Figure 7 (c) as shown.

[0054] In combination with the above-mentioned Implementation Case 1 and Implementation Case 2, it can be seen that the simulation APP developed by the present invention is feasible. The simulation APP meets the requirements of simply, quickly, accurately and efficiently evaluating the fatigue performance of the main shaft of the cross-flow unit and is practical.

[0055] The above description is only a preferred embodiment of the present invention and does not constitute any form of hindrance to the present invention. Any simple modification or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A simulation method for quickly evaluating the fatigue of a main shaft of a tubular unit, characterized in that: The method comprises the following steps: The first step is to call the spindle parts library, select the spindle basic parts from the parts library and assign the spindle basic parts attribute parameter values; In the second step, the spindle basic parts are imported into the finite element analysis model to form a three-dimensional spindle model. Then, the spindle load module is used to add the load and constraints of the three-dimensional spindle model, specify the spindle material and divide the structured grid. Finally, the bending stress and torsional stress of the dangerous section of the three-dimensional spindle model are obtained. The third step is to use the spindle fatigue strength module, based on the bending stress and torsional stress of the dangerous section of the spindle 3D model, and use the fatigue strength mathematical model to calculate the fatigue strength safety factor of the spindle 3D model under symmetrical cyclic stress load, asymmetrical cyclic stress load and bending-torsion combined load conditions; The fourth step is to output the calculation results of the fatigue strength safety factor of the main shaft three-dimensional model in the form of a chart.

2. A simulation method for rapidly evaluating fatigue of a main shaft of a tubular unit according to claim 1, characterized in that: The spindle basic part attribute parameter values ​​include part size, part dangerous area, geometric features of the part dangerous area, load boundary and constraint boundary.

3. A simulation method for rapidly evaluating fatigue of a main shaft of a tubular unit according to claim 1, characterized in that: The fatigue strength mathematical model includes a symmetrical cyclic stress load fatigue strength mathematical model, an asymmetrical cyclic stress load fatigue strength mathematical model and a bending-torsion combined load fatigue strength mathematical model.

4. A simulation method for rapidly evaluating fatigue of a main shaft of a tubular unit according to claim 1, characterized in that: The spindle fatigue strength module is embedded with a fatigue strength mathematical model parameter table.

5. A simulation APP for quickly evaluating the fatigue of the main shaft of a tubular unit, the APP is used to implement the simulation method described in any one of claims 1 to 4, characterized in that: Included integrated in the developer: The spindle parts library is configured to define the attribute parameter values ​​of the spindle basic parts constituting the spindle of the unit based on the basic structural form of the spindle of the unit; The spindle load module is configured to add the load and constraint of the model, specify the spindle material and divide the structured mesh based on the spindle three-dimensional model to obtain the bending stress and torsional stress of the dangerous section of the spindle three-dimensional model; The spindle fatigue module is configured to calculate the fatigue strength safety factor of the spindle three-dimensional model under symmetrical cyclic stress load, asymmetrical cyclic stress load and bending-torsion combined load conditions based on the bending stress and torsional stress of the dangerous section of the spindle three-dimensional model using a fatigue strength mathematical model; and output the calculation results of the fatigue strength safety factor of the spindle three-dimensional model in the form of a chart.

6. A method for developing a simulation APP for quickly evaluating the fatigue of a main shaft of a tubular unit, the method being used to develop the simulation APP described in claim 5, characterized in that: Based on the secondary development tool of COMSOL Multiphysics software, a spindle parts library, a spindle load module and a spindle fatigue module are created. Finally, the above modules are compiled through COMSOL Compiler TM Compiled into a simulation APP for rapid assessment of shaft fatigue of tubular units.

7. The method for developing a simulation APP for rapidly evaluating the fatigue of a main shaft of a tubular unit according to claim 6 is characterized in that: The method The following steps are involved: The first step is to establish the spindle basic parts through parametric modeling, assign attribute parameters to each spindle basic part, compile the spindle basic parts into the built-in parts library of COMSOL Multiphysics software, and thus create a spindle parts library; The second step is to write the load and constraint of the three-dimensional model of the main shaft, the main shaft material, the grid structure division, and the calculation formulas of the bending stress and torsional stress of the dangerous section into the calculation program of the COMSOL Multiphysics software, and thus create a main shaft load module; The third step is to write the fatigue strength safety factor calculation formula corresponding to the symmetrical cyclic stress load, the fatigue strength safety factor calculation formula corresponding to the asymmetrical cyclic stress load, and the fatigue strength safety factor calculation formula corresponding to the bending-torsion combined load into the COMSOL Multiphysics software program, thereby creating a spindle fatigue module; The fourth step is to integrate the spindle parts library, spindle load module and spindle fatigue module into COMSOL Compiler TM The program is developed on a developer and finally compiled into a simulation APP for quickly evaluating the fatigue of the main shaft of a tubular unit.

Images