SiPESC-based welding birth and death unit definition method

Abstract

The invention discloses a welding birth and death unit defining method based on SiPESC. The method needs to be implemented under the condition that a finite element model of the welding process is established. The method comprises the following steps that a unit set containing units needing to be killed or activated in a certain analysis step is established; first, a weld unit is killed in a removal analysis step; in the subsequent welding analysis step, the weld units are activated step by step in sequence. According to the method provided by the invention, during welding numerical simulation, the change of the structure at the welding seam in the welding process can be accurately simulated, and the dynamic heat input in the welding process and the moving effect of a welding heat source can be accurately described, so that the heat conduction, stress distribution and deformation conditions in the welding process can be effectively captured; and an engineer is helped to better evaluate stress concentration and deformation at the welding seam.

Description

Technical Field

[0001] The present invention relates to the technical field of welding simulation, and particularly to a method for defining welding birth and death elements based on SiPESC. Background Art

[0002] In welding simulation analysis, the use of birth and death element technology is mainly to cope with the complex dynamic changes and physical phenomena during the welding process. Welding materials need to be gradually added to the base material, and the traditional finite element method cannot simulate this process, while the birth and death element technology can accurately reflect the generation of materials by dynamically activating new elements.

[0003] In addition, the melting and solidification processes caused by the welding heat source, the changes in the heat affected zone, and the phase transformation of materials at high temperatures also need to be dynamically simulated. The birth and death element technology can handle these changes by activating and deactivating elements. The thermal stress, residual stress, and deformation caused by the temperature gradient during the welding process, as well as the possible cracks and welding defects, can also be effectively captured by the birth and death elements.

[0004] As is well known, the difficulty of welding birth and death element technology lies in how to accurately define the "birth" and "death" states of elements during the simulation process, so as to dynamically "activate" or "kill" specific elements. In view of the above problems, we propose a new method for defining welding birth and death elements. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for defining welding birth and death elements based on SiPESC, so as to be able to "activate" or "kill" specific elements in an orderly manner in real time according to the welding trajectory during welding simulation, dynamically simulate the generation and disappearance of materials, and thus more accurately reflect the changes in the structure at the weld during the welding process.

[0006] To solve the above technical problems, the present invention provides a method for defining welding birth and death elements based on SiPESC, including the following steps: S1. Establish a finite element model of the welding process; Establish a geometric model for welding analysis; Define the material properties of each component; Perform finite element mesh division on the model to meet the requirements of welding simulation; Define the boundary conditions and initial conditions of the welding process such as convective heat transfer and thermal radiation; Define the solution conditions for the analysis type, analysis duration, increment step size, and convergence residual; S2. Establish an element set Establish an element set that includes the elements to be "killed" or "activated" in the analysis step, which can be all the elements in a certain area or specific individual elements; There are the following two definition methods for the definition of the unit set in the input file: S2-1 If the unit numbers in the set are consecutive, the unit set format is as follows: *Elset, Elset = unit set name, Generate Starting unit number, ending unit number, unit number increment S2-2. If the unit numbers in the set are non-consecutive, the representation method is: list all the units in the set in sequence (the unit numbers in each data line shall not exceed 16), and the unit set format is as follows: *Elset, Elset = unit set name Unit number 1, unit number 2,...

[0007] S3. In the removal setting, select the unit set to be killed; It is defined by the keyword *Model Change, and the type is selected as remove. The specific format is as follows: *Model Change, remove Name of the unit set to be killed; In numerical calculation, the following processing will be performed on the units in the killed state: assign a quantity to the stiffness of the unit; Set the unit loads (such as pressure, temperature) to zero; Set the properties such as the mass and damping of the unit to zero; In post-processing display, the units in the killed state will not be displayed.

[0008] S4. In the activation setting, select the unit set to be activated; Based on the definition method of welding birth and death units of SiPESC, it is characterized in that in the input file of step S4, it is defined by the keyword *Model Change, and the type is selected as add. The specific format is as follows: *Model Change, add Name of the unit set to be activated.

[0009] In numerical calculation, the property parameters of the units in the activated state are restored.

[0010] Compared with the prior art, the beneficial effects achieved by the method of the present invention are: during welding numerical simulation, it can accurately simulate the structural changes at the weld during the welding process, accurately describe the dynamic heat input during the welding process and the moving effect of the welding heat source, effectively capture the heat conduction, stress distribution and deformation during welding, and help the operator better evaluate the stress concentration and deformation at the weld. Description of the Drawings

[0011] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation to the present invention. In the accompanying drawings: Figure 1 is a schematic diagram of the weld area of the method of the present invention.

[0012] Figure 2 is the rendering of the weld unit killing effect of the method of the present invention.

[0013] Figure 3 is a schematic diagram of the step-by-step activation of the weld unit of the method of the present invention. Detailed Description of the Invention

[0014] The technical solution of the present invention will be further described in detail below in conjunction with the preferred embodiments and their accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0015] This embodiment is for flat welding, and the weld is as Figure 1 shown.

[0016] In the preparatory work, a finite element model of the welding process has been established. That is, a geometric model of the welded flat plate is established; the material properties of the flat plate are defined; a reasonable finite element mesh is divided for the flat plate model to meet the requirements of welding simulation; boundary conditions such as convective heat transfer and thermal radiation are defined on the surface of the flat plate; the initial temperature of the flat plate is defined; and solution conditions such as analysis type, analysis duration, increment step size, and convergence residual are defined.

[0017] First, a unit set is established, and the set contains the units that need to be "killed" or "activated" in each analysis step. There are usually the following two definition methods for the definition of the unit set in the input file: After the unit set is established, the birth and death units are set. First, the weld units are killed in the removal analysis step. In the removal settings, select the set of weld units to be killed. The effect of killing the weld units is as Figure 2 shown. In numerical calculations, a small value is assigned to the element stiffness of these units, and the damping, heat capacity coefficient, and loads (such as pressure and temperature) of the units are set to zero. In the subsequent welding analysis steps, the weld units are gradually activated in sequence. In numerical calculations, the property parameters of the units in the activated state will be restored.

[0018] Thus, specific units can be "activated" or "killed" in real time and in an orderly manner according to the welding trajectory in the welding numerical simulation. Figure 3 shows the weld units being gradually activated, dynamically simulating the filling of the solder.

[0019] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "left", "right", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention.

[0020] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for defining welding birth and death elements based on SiPESC, characterized in that, The method includes the following steps: S1. Establish a finite element model of the welding process; Establish a geometric model for welding analysis; Define the material properties of each component; Perform a finite element mesh division on the model that meets the requirements of welding simulation; Define the boundary conditions and initial conditions of the welding process such as convective heat transfer and thermal radiation; Define the solution conditions for the analysis type, analysis duration, increment step size, and convergence residual; S2. Establish an element set Establish an element set that contains the elements to be "killed" or "activated" in the analysis step. It can be all the elements in a certain area or specific individual elements; S3. In the removal setting, select the element set to be killed; S4. In the activation setting, select the element set to be activated; In numerical calculation, restore the property parameters of the elements in the activated state.

2. The method for defining welding birth and death elements based on SiPESC according to claim 1, wherein In step S2, there are the following two definition methods for the definition of the element set in the input file: S2-1 If the element numbers in the set are continuous, the element set format is as follows: *Elset, Elset = element set name, Generate Starting element number, ending element number, element number increment S2-2. If the element numbers in the set are discontinuous, the representation method is: list all the elements in the set in sequence, and the element set format is as follows: *Elset, Elset = element set name Element number 1, element number 2,...

3. A method for defining welding birth and death elements based on SiPESC according to claim 1, characterized in that, Step S3 is defined in the input file through the keyword *Model Change, and the type is selected as remove. The specific format is as follows: *Model Change, remove Name of the element set to be killed; In numerical calculation, the following processing will be performed on the elements in the killed state: assign a quantity to the stiffness of the element; Set the element load to zero; Set the mass and damping properties of the element to zero; In the post-processing display, the elements in the killed state will not be displayed.

4. A method for defining welding birth and death elements based on SiPESC according to claim 1, characterized in that, In step S4 input file, it is defined through the keyword *Model Change, and the type is selected as add. The specific format is as follows: *Model Change, add Name of the element set to be activated.

5. The method for defining welding birth and death elements based on SiPESC according to claim 2, characterized in that, In step S2, list all the elements in the set in sequence, and the number of element numbers in each data row shall not exceed 16.

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