A finite element simulation method and system for fatigue damage evolution of mortise and tenon joints

Abstract

The present invention discloses a finite element simulation method and system for fatigue damage evolution of mortise and tenon joints. Under high-cycle fatigue conditions, the tenon is pulled out of the mortise due to changes in the friction coefficient and fit relationship. The simulation model considers the process in which the friction coefficient and fit between the tenon and the tenon change with fatigue damage evolution. The fatigue performance (friction coefficient, fit, life) in the simulation model is affected by the load amplitude. An implicit dynamic analysis step is used to establish a finite element simulation model. The friction coefficient in the contact attribute is modified to a function value that changes with the loading time. The fit amplitude in the contact attribute is modified to a function value that changes with the loading time. The fatigue working condition of the mortise and tenon joint is numerically simulated in an implicit dynamic analysis step, and the simulation includes a complete fatigue working condition process. The state of the mortise and tenon joint under any number of loading times is thereby obtained. While improving computational efficiency, the present invention simulates the fatigue damage evolution and life prediction of the mortise and tenon joint from a dynamic perspective.

Description

Technical Field

[0001] The present invention relates to the field of fatigue simulation analysis of wooden furniture and wooden building structures, and in particular to a finite element simulation method and system for fatigue damage evolution and life prediction of mortise and tenon joints. Background Art

[0002] Low-load, high-cycle fatigue conditions are the primary cause of reduced furniture structural strength. Furniture durability is paramount in its design and evaluation. However, testing the fatigue mechanical properties of furniture structures is both expensive and time-consuming. Furniture structural testing cycles are long, requiring multiple repetitions, and material loss increases costs. Consequently, traditional testing methods for furniture structural fatigue mechanical properties are both expensive and time-consuming.

[0003] However, existing fatigue performance prediction methods mostly calculate the fatigue mechanical properties of components based on the material's fatigue life. While fatigue performance experiments are generally more universally applicable, in reality, the same material can exhibit different fatigue mechanical properties under different structural conditions. Furthermore, the numerous factors that influence material fatigue performance make conventional simulations difficult to accurately reflect actual application scenarios. For furniture structures, fatigue is primarily manifested in loosening of joints and a reduction in joint strength due to long-term use. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a finite element simulation method for fatigue damage evolution of mortise and tenon joints, which improves computational efficiency while simulating the fatigue damage evolution and life prediction of mortise and tenon joints from a dynamic perspective.

[0005] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A finite element simulation method for fatigue damage evolution in mortise and tenon joints is proposed. Under high-cycle fatigue conditions, the tenon is pulled out of the mortise due to changes in the friction coefficient and fit relationship. The simulation model considers the changes in the friction coefficient and fit between the tenon and the mortise as fatigue damage evolves. The finite element simulation model is established using an implicit dynamic analysis step. By modifying the Edit Keywords, the friction coefficient in the contact properties is modified to a function value that varies with the loading time (number of times). By setting the Amplitude, the fit amplitude in the contact properties is modified to a function value that varies with the loading time (number of times). The fatigue condition of the mortise and tenon joint is numerically simulated using a dynamic analysis step, and the simulation includes the complete fatigue condition process. The state of the mortise and tenon joint under any number of loading times is thus obtained. The method specifically includes the following steps:

[0007] Step S1, using implicit dynamics analysis step to establish a finite element simulation model.

[0008] Step S2, establishing a time friction coefficient model of the elliptical tenon of wooden furniture according to the time and friction coefficient of the elliptical tenon of wooden furniture.

[0009] Step S3, establishing a time interference fit model of the elliptical tenon of wooden furniture according to the time and interference fit of the elliptical tenon of wooden furniture.

[0010] In step S4, the tenon and mortise components are created in the finite element simulation model and assembled. Two implicit dynamics analysis steps are created, which are respectively recorded as the first implicit dynamics analysis step and the second implicit dynamics analysis step.

[0011] Step S5: Set two contact properties, including normal and tangential behavior. Set the normal behavior to hard contact and the tangential behavior to "penalty." Set the two pairs of arc contact surfaces, one between the width of the tenon and the length of the mortise, and the other between the shoulder of the tenon and the corresponding surface of the mortise, to "surface-to-surface contact," for a total of three pairs of contact surfaces.

[0012] Step S6: Change the contact properties of the two pairs of arc contact surfaces in the width direction of the tenon and the length direction of the mortise in the second implicit dynamics analysis step. Create a first equally spaced amplitude and input the time friction coefficient model of the elliptical tenon of wooden furniture into the first equally spaced amplitude.

[0013] In step S7, the two pairs of arc contact surfaces in the width direction of the tenon and the length direction of the mortise in the first implicit dynamics analysis step are set to an interference fit. A second equally spaced amplitude is created, and the time interference fit model for the elliptical tenon of wooden furniture is input into this second equally spaced amplitude.

[0014] In step S8, set a reference point outside the other end of the tenon component and establish a coupling constraint between this reference point and the tenon end face. Create boundary conditions to set the lower end of the mortise component to a fully fixed constraint. Apply a displacement constraint boundary condition to the reference point of the tenon component. Set the mesh type of the tenon and mortise components to C3D8R and the mesh control to the front advancing method with a hexagonal sweep to complete the creation of the finite element simulation model.

[0015] Step S9, simulating the fatigue performance, friction coefficient and matching relationship of the mortise and tenon joint at any time according to the created finite element simulation model, and completing the fatigue damage evolution of the mortise and tenon joint.

[0016] Preferred: The fatigue failure model during damage evolution is as follows:

[0017]

[0018] Where t represents the loading time, f represents the loading frequency, β1 represents the time friction coefficient constant, β2 represents the time interference fit constant, α1 represents the time friction coefficient index, α2 represents the time interference fit index, E represents the material elastic modulus, F y represents the load amplitude, and θ represents the rotation angle of the component after the force is applied.

[0019] Optimum: Time friction coefficient model is:

[0020]

[0021] Where μ represents the friction coefficient, t represents the loading time, f represents the loading frequency, β1 represents the time friction coefficient constant, and α1 represents the time friction coefficient exponent.

[0022] Optimum: Time interference fit model is:

[0023]

[0024] Among them, d represents the interference fit, t represents the loading time, f represents the loading frequency, β2 represents the time interference fit constant, and α2 represents the time interference fit index.

[0025] Preferably, the tenon component and the mortise component created in step S4 are both 3D deformable bodies. The tenon component and the mortise component are assembled, and the tenon of the tenon component is assembled into the mortise of the mortise component.

[0026] Preferably, in step S4, a material including density and mechanical elasticity is created, and the type of mechanical elasticity is orthogonal anisotropy. The material is assigned to the tenon component and the mortise component, and material directions are assigned to them respectively.

[0027] Preferably, the tenon size of the tenon component is consistent with the mortise size of the mortise component.

[0028] Another object of the present invention is to provide a finite element simulation system for fatigue damage evolution of mortise and tenon joints, which is used to implement the finite element simulation method for fatigue damage evolution of mortise and tenon joints, including a time friction coefficient model unit, a time interference fit model unit, and a finite element simulation model unit, wherein:

[0029] The time friction coefficient model unit is used to store the time friction coefficient model of the elliptical tenon of wooden furniture.

[0030] The time interference fit model unit is used to store the time interference fit model of the elliptical tenon of wooden furniture.

[0031] The finite element simulation model unit is used to establish a finite element simulation model using an implicit dynamics analysis step. A tenon component and a mortise component are created in the finite element simulation model and assembled. Two implicit dynamics analysis steps are created, recorded as the first implicit dynamics analysis step and the second implicit dynamics analysis step. Two contact properties, including normal behavior and tangential behavior, are set, with the normal behavior set to hard contact and the tangential behavior set to a "penalty" property. Two pairs of circular arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component, as well as the tenon shoulder surface of the tenon component and the corresponding surface of the mortise component, are set to "surface-to-surface contact" contact surfaces, for a total of three pairs of contact surfaces. The contact properties of the two pairs of circular arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component are changed in the second implicit dynamics analysis step. A first equally spaced amplitude is created, and the time friction coefficient model of the elliptical tenon of wooden furniture is input into the first equally spaced amplitude. The fit relationship of the two pairs of circular arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component in the first implicit dynamics analysis step is set to an interference fit. Create a second equally spaced amplitude and input the time interference fit model of the elliptical tenon of wooden furniture into the second equally spaced amplitude. Set a reference point at the outer position of the other end of the tenon component and establish a coupling constraint with the end face of the tenon. Create boundary conditions and set the lower end of the mortise component to a completely fixed constraint. Apply displacement constraint boundary conditions to the reference point of the tenon component. Set the mesh type of the tenon and mortise components to C3D8R, and set the mesh control to the frontier advancing method of hexagonal sweep to complete the creation of the finite element simulation model. Based on the created finite element simulation model, simulate the fatigue performance, friction coefficient and fit relationship of the mortise and tenon joint at any time to complete the fatigue damage evolution of the mortise and tenon joint.

[0032] Another object of the present invention is to provide a computer system, characterized by comprising a memory and a processor, wherein the memory is used to store computer programs / instructions, and the processor is used to execute the computer programs / instructions to implement the finite element simulation method for fatigue damage evolution of joints.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. Based on the actual fatigue mechanical properties of wooden elliptical tenon furniture, the fatigue performance evolution and failure process of the tenon joint are described and simulated from the perspectives of friction coefficient, interference fit and fatigue life, rather than just fatigue life, which is more in line with actual working conditions.

[0035] 2. The fatigue condition of the elliptical tenon of wooden furniture is numerically simulated in the form of dynamic analysis steps. The simulation includes the complete fatigue condition process, and the analysis process is efficient and accurate.

[0036] 3. The model can be established using the graphical user interface of general finite element software (such as ABAQUS), without the need to use other functions such as subroutines or secondary development, making it easier to master. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a finite element numerical simulation embodiment model of an embodiment of the present invention;

[0038] Figure 2 The loading times-friction coefficient function curve of the embodiment of the present invention;

[0039] Figure 3 The loading times-matching amount function curve of the embodiment of the present invention;

[0040] Figure 4 This is a structural force analysis diagram of an embodiment of the present invention;

[0041] Figure 5 This is the model failure simulation result of the embodiment of the present invention;

[0042] Figure 6 This is a flow chart of a finite element numerical simulation method for fatigue performance evolution of an elliptical tenon of wooden furniture according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] The present invention is further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention made by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0044] A finite element simulation method for fatigue damage evolution of mortise and tenon joints is proposed. (1) Under high-cycle fatigue conditions, the tenon is pulled out of the mortise due to changes in the friction coefficient and fit relationship. The simulation model considers the process in which the friction coefficient and fit between the tenon and the mortise change with the evolution of fatigue damage. The finite element simulation model is established using an implicit dynamics analysis step. (2) The finite element model should contain at least one pair of tenon and mortise components. (3) The tenon and mortise components are 3D deformable bodies. (4) The material properties of the tenon and mortise components in the finite element model of wooden furniture elliptical tenon are elastic-plastic materials, and the elastic type is orthotropic. (5) The finite element model of wooden furniture elliptical tenon has two pairs of contact surfaces in the width direction of the tenon component and the length direction of the mortise component. (6) By modifying the edit keyword (Edit The keyword content in the Keywords) module is used to modify the friction coefficient in the contact properties to a function value that changes with the loading time (number of times); (7) By setting the amplitude (Amplitude), the matching amount in the contact properties is modified to a function value that changes with the loading time (number of times); (8) Completely fixed constraints are applied to both ends of the mortise and tenon component, and fatigue load is applied to the mortise and tenon component. The load direction should be parallel to the normal of the contact surface between the tenon and the mortise component, and the stress ratio of the fatigue load amplitude is R = -1; (9) Through the time friction coefficient model of the elliptical tenon of wooden furniture and the time interference fit model of the elliptical tenon of wooden furniture, the fatigue performance, friction coefficient and matching relationship of the node at any time are simulated, such as Figure 5 As shown in the figure, it is implemented based on ABAQUS finite element software. Specifically, it simulates the complete process of fatigue performance evolution and failure of an elliptical tenon of wooden furniture with an applied load amplitude of 200N and a fatigue life of 100,000 times. The specific steps include:

[0045] Step S1, using implicit dynamics analysis step to establish a finite element simulation model.

[0046] Step S2, establishing a time friction coefficient model of the elliptical tenon of wooden furniture according to the time and friction coefficient of the elliptical tenon of wooden furniture.

[0047] like Figure 2 As shown in the figure, the loading times-friction coefficient model of the elliptical tenon of wooden furniture is:

[0048]

[0049] in:

[0050] N = t × f;

[0051] Then the time friction coefficient model is:

[0052]

[0053] Wherein, μ represents the friction coefficient, N represents the number of loadings, t represents the loading time, f represents the loading frequency, β1 represents the time friction coefficient constant, α1 represents the time friction coefficient exponent, α1<0, β1>0.

[0054] Step S3, establishing a time interference fit model of the elliptical tenon of wooden furniture according to the time and interference fit of the elliptical tenon of wooden furniture.

[0055] like Figure 3 As shown in the figure, the loading times-interference fit model of the elliptical tenon of wooden furniture is:

[0056]

[0057] in:

[0058] N = t × f;

[0059] Then the time interference fit model is:

[0060]

[0061] Where d represents the interference fit, N represents the number of loadings, t represents the loading time, f represents the loading frequency, β2 represents the time interference fit constant, α2 represents the time interference fit index, α2 < 0, β2 > 0.

[0062] In step S4, the tenon and mortise components are created in the finite element simulation model and assembled. Two implicit dynamics analysis steps are created, which are respectively recorded as the first implicit dynamics analysis step and the second implicit dynamics analysis step.

[0063] Specifically, such as Figure 1 As shown, a tenon component and a mortise component are created, both the tenon and the mortise components are 3D deformable bodies (Deformable); the tenon size of the tenon component is consistent with the mortise size of the mortise component.

[0064] Assemble the tenon component and the mortise component, and fit the tenon of the tenon component into the mortise of the mortise component.

[0065] In step S4, a material containing density and mechanical elasticity is created, where the mechanical elasticity type is orthogonal anisotropic. The material is assigned to the tenon and mortise components, and the material direction is assigned to each component.

[0066] Create a material that contains density and mechanical elasticity. The mechanical elasticity type is orthotropic. Assign the material to the tenon part and the mortise part, and assign the material direction to them respectively.

[0067] Create two implicit dynamics analysis steps, labeled the first implicit dynamics analysis step and the second implicit dynamics analysis step. Set the time of the first implicit dynamics analysis step to 1 second and the time of the second implicit dynamics analysis step to greater than 100,000 seconds. Set geometric nonlinearity (Nlgeom) to on for both analysis steps. Set the frequency of field output and history output for the first implicit dynamics analysis step to every n increments, with n set to 1. Set the frequency of field output and history output for the second implicit dynamics analysis step to evenly spaced time intervals, with the interval value set to twice the analysis step time.

[0068] Step S5: Set two contact properties, including normal and tangential behavior. Set the normal behavior to hard contact and the tangential behavior to "penalty." Set the two pairs of arc contact surfaces, one between the width of the tenon and the length of the mortise, and the other between the shoulder of the tenon and the corresponding surface of the mortise, to "surface-to-surface contact," for a total of three pairs of contact surfaces.

[0069] Set two contact properties containing normal behavior and tangential behavior. The normal behavior is set to hard contact (Hardcontact), and the tangential behavior is set to the "Penalty" attribute. Among them, set the friction coefficient in the "Penalty" attribute of one contact property to 0.3, and the other to 1.

[0070] Two pairs of arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component, as well as the tenon shoulder surface and the corresponding surface of the mortise component, are set as "surface-to-surface contact" contact surfaces, for a total of three pairs of contact surfaces. A contact property with a friction coefficient of 0.3 is assigned to the three pairs of contact surfaces.

[0071] Step S6: Change the contact properties of the two pairs of arc contact surfaces in the width direction of the tenon and the length direction of the mortise in the second implicit dynamics analysis step. Create a first equally spaced amplitude and input the time friction coefficient model of the elliptical tenon of wooden furniture into the first equally spaced amplitude.

[0072] Specifically, the contact properties of the two pairs of arc contact surfaces in the width direction of the tenon and the length direction of the mortise are changed to the contact properties with a friction coefficient of 1 in the second implicit dynamics analysis step; the first equal-spaced amplitude is created, and the time friction coefficient model of the elliptical tenon of wooden furniture (such as Figure 2The time friction coefficient model of the elliptical tenon of wooden furniture is named "Change of friction coefficient"; the keywords of the model are modified, and "AMPLITUDE=Change of friction coefficient" is added after the "*Change Friction, interaction=XXX (contact surface name)" keyword of the two pairs of arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component in the second implicit dynamics analysis step.

[0073] In step S7, the two pairs of arc contact surfaces in the width direction of the tenon and the length direction of the mortise in the first implicit dynamics analysis step are set to an interference fit. A second equally spaced amplitude is created, and the time interference fit model for the elliptical tenon of wooden furniture is input into this second equally spaced amplitude.

[0074] Specifically, the fitting relationship of the two pairs of arc contact surfaces in the width direction of the tenon part and the length direction of the mortise part in the first implicit dynamics analysis step is set to interference fit, the fitting amount (Magnitude at start of step) is set to -0.06, and the amplitude is set to increase uniformly from 0 to 1; create a second equally spaced amplitude, input the time interference fit model of the elliptical tenon of wooden furniture into the second equally spaced amplitude, and name the time interference fit model of the elliptical tenon of wooden furniture as "Change of interference fit"; modify the amplitude of the fitting relationship of the second implicit dynamics analysis step to the amplitude of "Change of interference fit".

[0075] In step S8, set a reference point outside the other end of the tenon component and establish a coupling constraint between this reference point and the tenon end face. Create boundary conditions to set the lower end of the mortise component to a fully fixed constraint. Apply a displacement constraint boundary condition to the reference point of the tenon component. Set the mesh type of the tenon and mortise components to C3D8R and the mesh control to the front advancing method with a hexagonal sweep to complete the creation of the finite element simulation model.

[0076] Specifically, set a reference point on the outside of the other end of the tenon component and establish a coupling constraint between this reference point and the tenon end face. Create a boundary condition to set the lower end of the mortise component to a fully fixed constraint.

[0077] Create a tabular amplitude, set a fatigue load amplitude of 20 loads every 60 seconds, each load lasting 1 second, and a stress ratio of R = -1, and name it "Fatigue load"; apply a displacement constraint boundary condition to the reference point of the tenon component, set its three displacements and three rotational degrees of freedom to 0 in analysis step 1, set its displacement in the loading direction to 1.5 in analysis step 2, and set the degrees of freedom in the other five directions to 0, and set the amplitude of this analysis step to the "Fatigue load" amplitude.

[0078] Set the mesh type of the tenon and mortise to C3D8R, set the mesh control to Hex sweep advancing front, and set the mesh size to 5. Change the mesh size to 3 at the tenon and mortise.

[0079] Through the above steps, a finite element simulation model can be established to reflect the fatigue performance evolution and failure effects of the elliptical tenon of wooden furniture from a dynamic perspective.

[0080] Step S9, simulating the fatigue performance, friction coefficient and matching relationship of the mortise and tenon joint at any time according to the created finite element simulation model, and completing the fatigue damage evolution of the mortise and tenon joint.

[0081] The method for establishing the fatigue failure model during the damage evolution process is as follows:

[0082] Step S91: The formula for the pull-out force on the wooden furniture elliptical tenon in the horizontal direction is:

[0083]

[0084] Where, F x Indicates the horizontal pull-out force, F y represents the load amplitude, and θ represents the rotation angle of the component after the force is applied.

[0085] Step S92, the pull-out resistance model of the elliptical tenon of wooden furniture is:

[0086] F b =μ×d×E;

[0087] Where, F b represents the pull-out resistance of the node, μ represents the friction coefficient, d represents the interference fit, and E represents the elastic modulus of the material.

[0088] Step S93: During the damage evolution process, when the pull-out resistance of the wooden furniture elliptical tenon is less than or equal to the pull-out force it receives in the horizontal direction, the tenon is pulled out from the mortise, that is:

[0089] F b≤F x ;

[0090] The fatigue failure model is as follows:

[0091]

[0092] Where t represents the loading time, f represents the loading frequency, β1 represents the time friction coefficient constant, β2 represents the time interference fit constant, α1 represents the time friction coefficient index, α2 represents the time interference fit index, E represents the material elastic modulus, F y represents the load amplitude, and θ represents the rotation angle of the component after the force is applied.

[0093] Another object of the present invention is to provide a finite element simulation system for fatigue damage evolution of mortise and tenon joints, which is used to implement the finite element simulation method for fatigue damage evolution of mortise and tenon joints, including a time friction coefficient model unit, a time interference fit model unit, and a finite element simulation model unit, wherein:

[0094] The time friction coefficient model unit is used to store the time friction coefficient model of the elliptical tenon of wooden furniture.

[0095] The time interference fit model unit is used to store the time interference fit model of the elliptical tenon of wooden furniture.

[0096] The finite element simulation model unit is used to establish a finite element simulation model using an implicit dynamics analysis step. A tenon component and a mortise component are created in the finite element simulation model and assembled. Two implicit dynamics analysis steps are created, recorded as the first implicit dynamics analysis step and the second implicit dynamics analysis step. Two contact properties, including normal behavior and tangential behavior, are set, with the normal behavior set to hard contact and the tangential behavior set to a "penalty" property. Two pairs of circular arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component, as well as the tenon shoulder surface of the tenon component and the corresponding surface of the mortise component, are set to "surface-to-surface contact" contact surfaces, for a total of three pairs of contact surfaces. The contact properties of the two pairs of circular arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component are changed in the second implicit dynamics analysis step. A first equally spaced amplitude is created, and the time friction coefficient model of the elliptical tenon of wooden furniture is input into the first equally spaced amplitude. The fit relationship of the two pairs of circular arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component in the first implicit dynamics analysis step is set to an interference fit. Create a second equally spaced amplitude and input the time interference fit model of the elliptical tenon of wooden furniture into the second equally spaced amplitude. Set a reference point at the outer position of the other end of the tenon component and establish a coupling constraint with the end face of the tenon. Create boundary conditions and set the lower end of the mortise component to a completely fixed constraint. Apply displacement constraint boundary conditions to the reference point of the tenon component. Set the mesh type of the tenon and mortise components to C3D8R, and set the mesh control to the frontier advancing method of hexagonal sweep to complete the creation of the finite element simulation model. Based on the created finite element simulation model, simulate the fatigue performance, friction coefficient and fit relationship of the mortise and tenon joint at any time to complete the fatigue damage evolution of the mortise and tenon joint.

[0097] Another object of the present invention is to provide a computer system, characterized by comprising a memory and a processor, wherein the memory is used to store computer programs / instructions, and the processor is used to execute the computer programs / instructions to implement the finite element simulation method for fatigue damage evolution of joints.

[0098] When the model of this embodiment reaches 100,000 loadings, due to the reduction of friction coefficient and interference fit, the tenon component gradually separates from the mortise component under the action of load. The numerical simulation effect of the model is as follows: Figure 4 shown.

[0099] Using an implicit dynamics analysis step to establish a finite element simulation model differs from traditional table-based analysis methods for fatigue life analysis based on SN curves (such as the Fatigue module in Ansys Workbench and the Fe-safe module in ABAQUS). This is based on universal static and dynamic simulation modules. Therefore, the simulation can include the entire development process of the model's fatigue damage evolution. In addition, all settings and adjustments of the static and dynamic analysis modules are retained, allowing users to adjust, modify, and perform secondary development on the model as needed. Model establishment can be completed using the graphical user interface of universal finite element software (such as ABAQUS), eliminating the need for subroutines or other functions such as secondary development, making it easier to master.

[0100] Based on the fatigue mechanical properties of mortise and tenon joints, this method can intuitively reflect the fatigue performance evolution of mortise and tenon joints at a dynamic level, including the attenuation of friction coefficient and interference fit, and the failure of structural mechanical properties. While improving computational efficiency, it also simulates the fatigue damage evolution and lifespan prediction of mortise and tenon joints from a dynamic perspective.

[0101] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A finite element simulation method for fatigue damage evolution of mortise and tenon joints, characterized in that: The following steps are involved: Step S1, using implicit dynamics analysis step to establish a finite element simulation model; Step S2, establishing a time friction coefficient model of the wooden furniture elliptical tenon according to the time and friction coefficient of the wooden furniture elliptical tenon; Step S3, establishing a time interference fit model for the elliptical tenon of wooden furniture according to the time and interference fit of the elliptical tenon of wooden furniture; Step S4: Create a tenon component and a mortise component in the finite element simulation model and assemble them; create two implicit dynamics analysis steps, which are respectively recorded as the first implicit dynamics analysis step and the second implicit dynamics analysis step; Step S5: Set two contact properties, including normal and tangential behavior. The normal behavior is set to hard contact, and the tangential behavior is set to "penalty"; two pairs of arc contact surfaces in the width direction of the tenon and the length direction of the mortise, and the corresponding surfaces of the tenon shoulder and the mortise are set as "surface-to-surface contact" contact surfaces, for a total of three pairs of contact surfaces. Step S6: Change the contact properties of the two pairs of arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component in the second implicit dynamics analysis step; create a first equally spaced amplitude, and input the time friction coefficient model of the elliptical tenon of wooden furniture into the first equally spaced amplitude; Step S7: Setting the fitting relationship of the two pairs of arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component in the first implicit dynamics analysis step to an interference fit; creating a second equally spaced amplitude, and inputting the time interference fit model of the elliptical tenon of wooden furniture into the second equally spaced amplitude; Step S8: Set a reference point at the outer side of the other end of the tenon component and establish a coupling constraint between the reference point and the tenon end face; create boundary conditions to set the lower end of the mortise component as a completely fixed constraint; apply a displacement constraint boundary condition load for the fatigue condition to the reference point of the tenon component; set the mesh type of the tenon and mortise components to C3D8R, and set the mesh control to the front advancing method with a hexagonal sweep, completing the creation of the finite element simulation model; Step S9, simulating the fatigue performance, friction coefficient and matching relationship of the mortise and tenon joint at any time according to the created finite element simulation model, and completing the fatigue damage evolution of the mortise and tenon joint.

2. The finite element simulation method for fatigue damage evolution of mortise and tenon joints according to claim 1, characterized in that: The fatigue failure model during the damage evolution process is as follows: Where t represents the loading time, f represents the loading frequency, β1 represents the time friction coefficient constant, β2 represents the time interference fit constant, α1 represents the time friction coefficient index, α2 represents the time interference fit index, E represents the material elastic modulus, Fy represents the load amplitude, and θ represents the rotation angle generated by the component after the force is applied.

3. The finite element simulation method for fatigue damage evolution of mortise and tenon joints according to claim 2, characterized in that: The time friction coefficient model is: Where μ represents the friction coefficient, t represents the loading time, f represents the loading frequency, β1 represents the time friction coefficient constant, and α1 represents the time friction coefficient exponent.

4. The finite element simulation method for fatigue damage evolution of mortise and tenon joints according to claim 3, characterized in that: The time interference fit model is: Among them, d represents the interference fit, t represents the loading time, f represents the loading frequency, β2 represents the time interference fit constant, and α2 represents the time interference fit index.

5. The finite element simulation method for fatigue damage evolution of mortise and tenon joints according to claim 4, characterized in that: The tenon component and the mortise component created in step S4 are both 3D deformable bodies; the tenon component and the mortise component are assembled, and the tenon of the tenon component is assembled into the mortise of the mortise component.

6. The finite element simulation method for fatigue damage evolution of mortise and tenon joints according to claim 5, characterized in that: In step S4, a material including density and mechanical elasticity is created, and the type of mechanical elasticity is orthogonal anisotropy; the material is assigned to the tenon component and the mortise component, and the material direction is assigned to each component.

7. The finite element simulation method for fatigue damage evolution of mortise and tenon joints according to claim 6, characterized in that: The tenon size of the tenon component and the mortise size of the mortise component are consistent.

8. A finite element simulation system for fatigue damage evolution of mortise and tenon joints, characterized by: A finite element simulation method for fatigue damage evolution of a mortise and tenon joint according to any one of claims 1 to 6, comprising a time friction coefficient model unit, a time interference fit model unit, and a finite element simulation model unit, wherein: The time friction coefficient model unit is used to store the time friction coefficient model of the elliptical tenon of wooden furniture; The time interference fit model unit is used to store the time interference fit model of the elliptical tenon of wooden furniture; The finite element simulation model unit is used to establish a finite element simulation model using an implicit dynamics analysis step; create a tenon component and a mortise component in the finite element simulation model and assemble them; create two implicit dynamics analysis steps, which are respectively recorded as the first implicit dynamics analysis step and the second implicit dynamics analysis step; set two contact properties including normal behavior and tangential behavior, the normal behavior is set to hard contact, and the tangential behavior is set to a "penalty" property; set two pairs of arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component, and the tenon shoulder surface of the tenon component and the corresponding surface of the mortise component as "surface contact" contact surfaces, for a total of three pairs of contact surfaces; change the contact properties of the two pairs of arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component in the second implicit dynamics analysis step; create a first equally spaced amplitude, and input the time friction coefficient model of the elliptical tenon of wooden furniture into the first equally spaced amplitude. In the spacing amplitude, the fitting relationship of the two pairs of arc contact surfaces in the width direction of the tenon component and the length direction of the mortise component in the first implicit dynamics analysis step is set to interference fit; a second equally spaced amplitude is created, and the time interference fit model of the elliptical tenon of wooden furniture is input into the second equally spaced amplitude; a reference point is set at the outer position of the other end of the tenon component, and a coupling constraint is established between the reference point and the tenon end face; boundary conditions are created, and the lower end of the mortise component is set as a completely fixed constraint; a displacement constraint boundary condition is applied to the reference point of the tenon component; the mesh type of the tenon component and the mortise component is set to C3D8R, and the mesh control is set to the frontier advancing method of hexagonal sweeping to complete the creation of the finite element simulation model; the fatigue performance, friction coefficient and fitting relationship of the mortise joint node at any time are simulated according to the created finite element simulation model, and the fatigue damage evolution of the mortise joint node is completed.

9. A computer system, characterized in that: It comprises a memory and a processor, the memory is used to store computer programs / instructions; the processor is used to execute the computer programs / instructions to implement the finite element simulation method for fatigue damage evolution of a joint node according to any one of claims 1-7.

Images