Complex metal structure strength analysis method

Abstract

The invention belongs to the field of structural strength analysis, and particularly relates to a complex metal structural strength analysis method which comprises the following steps: simulating a material elastic-plastic behavior of a complex metal structure through a nonlinear finite element method; checking a nonlinear finite element calculation result and ensuring that the maximum equivalent plastic strain in the result exceeds the ultimate plastic strain of the metal material; drawing a change curve of the equivalent plastic strain along with the structural load according to a nonlinear finite element analysis result; the failure load of the structure is determined through the ultimate plastic strain of the material; and the safety margin of the complex metal structure is accurately given through the relation between the working load and the failure load of the structure. According to the method, the residual bearing capacity after the metal material enters plasticity is considered, and the precision of a traditional linear strength calculation method of a complex metal structure can be improved; meanwhile, the accurate safety margin of the complex metal structure is calculated through the load relation, and engineers can conveniently and visually analyze and judge the residual strength of the structure.

Description

Technical Field

[0001] The present application belongs to the field of structural strength analysis, and in particular relates to a method for analyzing the strength of complex metal structures. Background Art

[0002] In engineering, for complex metal structures such as concentrated load-transmitting joints (see the figure below), detailed finite element models are usually required for strength analysis. In detailed strength analysis, the equivalent stress in the stress concentration area (usually located in the R area of ​​the joint) in the finite element analysis results is mainly used as the strength judgment index (should be less than the ultimate tensile stress of the material), but this method is mainly applicable to linear elastic analysis and is too conservative, with a large error with the test results. In order to further explore the bearing capacity of the joint and reduce the weight of the structure, engineers have currently adopted a nonlinear detailed strength calculation method: that is, the elastoplastic properties of the metal material are considered in the finite element model for nonlinear calculation, and the equivalent plastic strain in the finite element analysis results is used as the strength judgment index (should be less than the ultimate plastic strain of the material). However, since the equivalent plastic strain changes nonlinearly with the increase of load, this method cannot give an accurate safety margin for the structure, which brings inconvenience to engineering applications. Summary of the invention

[0003] In order to solve the above problems, the present application provides a complex metal structure strength analysis method, including:

[0004] The first step is to establish a three-dimensional detailed finite element model of the metal structure, in which the elastic and plastic properties of the metal material are defined simultaneously;

[0005] The second step is to apply a gradually increasing load to the finite element model and perform nonlinear finite element analysis until the maximum equivalent plastic strain in the nonlinear finite element analysis results exceeds the material limit plastic strain;

[0006] The third step is to draw the curve of equivalent plastic strain changing with structural load based on the nonlinear finite element analysis results;

[0007] The fourth step is to determine the failure load [F] of the structure through the ultimate plastic strain of the material;

[0008] The fifth step is to calculate the failure load [F] and working load F of the structure. w Calculate the safety margin MS of the structure.

[0009] Preferably, the elongation of the material is taken as the limiting plastic strain of the material in the second step.

[0010] Preferably, the corresponding ultimate plastic strain in the material plastic property curve is used as the ultimate plastic strain of the material in the second step.

[0011] Preferably, the third step specifically includes: extracting the maximum equivalent plastic strain and the corresponding structural load of the corresponding highest stress area under each level of load in the finite element analysis results, and fitting the maximum equivalent plastic strain and the corresponding structural load to obtain a curve or expression of the change of the equivalent plastic strain with the structural load.

[0012] Preferably, the fourth step specifically includes: based on the curve or expression of the change of equivalent plastic strain with structural load, calculating the load corresponding to the ultimate plastic strain of the metal material, and using the corresponding load as the failure load [F] of the structure.

[0013] Preferably, the calculation formula of the safety margin MS is:

[0014]

[0015] Preferably, the metal structure comprises a typical metal joint structure.

[0016] Preferably, the highest stress area is the connection area between the joint and the base plate of a typical metal joint structure.

[0017] The advantages of this application include: BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A three-dimensional detailed finite element model of a typical complex metal structure according to the present invention;

[0019] Figure 2 The plastic strain-stress curve of the typical metal material used in the present invention;

[0020] Figure 3 is the variation history of the maximum equivalent plastic strain with load level in the simulation results;

[0021] Figure 4 The curve of equivalent plastic strain changing with structural load and the method for determining the structural failure load are drawn based on the nonlinear simulation results. DETAILED DESCRIPTION

[0022] In order to make the technical solution and advantages of the present application clearer, the technical solution of the present application will be further described in detail in detail and in detail in conjunction with the accompanying drawings. It can be understood that the specific embodiments described here are only partial embodiments of the present application, which are only used to explain the present application, not to limit the present application. It should be noted that, for the convenience of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design. In the absence of conflict, the embodiments in the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0023] The present invention is further described in detail below with reference to the accompanying drawings. Figure 1-Figure 4 .

[0024] Specifically, the complex metal structure strength analysis method of the present invention comprises the following steps:

[0025] The first step is to establish a three-dimensional detailed finite element model of a complex metal structure, such as the finite element model of the joint structure established in this example. Figure 1 As shown in the figure, the elastic and plastic properties of metal materials are defined in the model at the same time. The plastic strain-stress curve of the metal material used in this example is as follows: Figure 2 As shown, the corresponding limit plastic strain is 0.068; and the nonlinear finite element calculation is performed using the step-by-step load application method;

[0026] The second step is to check whether the maximum equivalent plastic strain in the nonlinear simulation results has exceeded the corresponding limit plastic strain in the material plastic performance curve. If not, return to the first step and increase the load applied to the structure and calculate until it exceeds. In this example, the maximum equivalent plastic strain in the simulation results changes with the load level as shown in the following figure: Figure 3 As shown in the figure, the maximum equivalent plastic strain corresponding to the 100% load level is 0.131, which exceeds the ultimate plastic strain of the metal material of 0.068;

[0027] The third step is to draw the curve of equivalent plastic strain changing with structural load according to the nonlinear simulation results. Specifically, the maximum equivalent plastic strain and the corresponding structural load in the high stress area of ​​the structure in the corresponding calculation results under each load level are extracted from the finite element analysis results, and the curve or expression of equivalent plastic strain changing with structural load is obtained by fitting. Figure 4 As shown;

[0028] The fourth step is to determine the failure load of the structure through the ultimate plastic strain of the material and the curve obtained in the previous step. Specifically, in the equivalent plastic strain-structural load variation curve (see Figure 4 ) or the load corresponding to the ultimate plastic strain of the metal material (for example, the ultimate plastic strain in this example is 0.068) calculated in the expression is used as the failure load [F] of the structure, for example, 116.0KN in this example;

[0029] Step 5: According to the structural failure load [F] and the working load F w Calculate the safety margin MS of the structure as shown below:

[0030]

[0031] If the working load of the joint structure in this example is 97.2KN, the corresponding safety margin is

[0032]

[0033] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A complex metal structure strength analysis method, characterized in that: include: The first step is to establish a three-dimensional detailed finite element model of the metal structure, in which the elastic and plastic properties of the metal material are defined simultaneously; The second step is to apply a gradually increasing load to the finite element model and perform nonlinear finite element analysis until the maximum equivalent plastic strain in the nonlinear finite element analysis results exceeds the material limit plastic strain; The third step is to draw the curve of equivalent plastic strain changing with structural load based on the nonlinear finite element analysis results; The fourth step is to determine the failure load [F] of the structure through the ultimate plastic strain of the material; The fifth step is to calculate the failure load [F] and working load F of the structure. w Calculate the safety margin MS of the structure.

2. The complex metal structure strength analysis method according to claim 1, characterized in that: The elongation of the material is taken as the material limit plastic strain in the second step.

3. The complex metal structure strength analysis method according to claim 1, characterized in that: The corresponding limit plastic strain in the material plastic performance curve is used as the material limit plastic strain in the second step.

4. The complex metal structure strength analysis method according to claim 1, characterized in that: The third step specifically includes: extracting the maximum equivalent plastic strain and the corresponding structural load of the highest stress area corresponding to each level of load in the finite element analysis results, and fitting the maximum equivalent plastic strain and the corresponding structural load to obtain a curve or expression of the change of equivalent plastic strain with structural load.

5. The complex metal structure strength analysis method according to claim 1, characterized in that: The fourth step specifically includes: based on the curve or expression of the change of equivalent plastic strain with structural load, calculating the load corresponding to the ultimate plastic strain of the metal material, and using the corresponding load as the failure load [F] of the structure.

6. The complex metal structure strength analysis method according to claim 1, characterized in that: The calculation formula of safety margin MS is:

7. The complex metal structure strength analysis method according to claim 1, characterized in that: The metal structure includes a typical metal joint structure.

8. The complex metal structure strength analysis method according to claim 7, characterized in that: The highest stress area is the connection area between the joint and the base plate of a typical metal joint structure.

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