Method for converting total load into equivalent load of fine finite element model

Abstract

The invention belongs to the technical field of aviation structure simulation analysis, and particularly relates to a method for converting a total load into an equivalent load of a fine finite element model, which comprises the following steps of: 1, setting a load conversion mode, and selecting a GFEM model; the load conversion modes comprise the following four modes: a, updating an RBE3 load principal point set; the load mode b is mapped to the nearest unit node; the load mode c is that the load is redistributed to the station node; the load mode d is that the load is converted under a local coordinate system; according to the method, four load conversion modes are provided on the basis of the characteristics in the structural design iteration process, the total load on the global finite element model can be quickly and accurately converted to the fine finite element model, most work requirements can be met, and the calculation efficiency is improved. And the working efficiency of converting the total load into the equivalent load of the fine finite element model can be greatly improved, and the accuracy of the load in the structural design iteration process is ensured.

Description

Technical Field

[0001] This invention belongs to the field of aerospace structural simulation and analysis technology, specifically relating to a method for converting overall load into equivalent load of a refined finite element model. Background Technology

[0002] Currently, in aerospace structural simulation analysis, when iterating structural strength simulation, a global finite element model (GFEM) is usually created first and verified using engineering methods. Later, a fine finite element model (GFEM) is created for detailed verification or local detail verification. However, the load remains basically unchanged throughout the entire iteration process. In order to ensure the consistency of the load during the iterative design process, the load on the GFEM model can be directly transferred to the nodes of the DFEM model.

[0003] However, ensuring that the load remains almost unchanged during the structural iteration process is a very labor-intensive process, especially for large civil aircraft, whose models are large and have many load conditions, requiring a lot of time to handle.

[0004] In response to the above situation, this invention proposes a method for converting the overall load into an equivalent load of a refined finite element model. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides a method for converting overall load into equivalent load in a refined finite element model. Based on the characteristics of the structural design iteration process, and according to different loading requirements, four load conversion methods are provided. This method can quickly and accurately convert the overall load on the global finite element model to the refined finite element model, meeting most work needs and greatly improving the efficiency of converting overall load into equivalent load in the refined finite element model, while ensuring the accuracy of the load during the structural design iteration process.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for converting a total load into an equivalent load in a refined finite element model, comprising the following steps: Step 1: Set the load transformation mode and select the GFEM model; The load conversion methods include the following four: Loading method a, updating the RBE3 load principal point set: By using the RBE3 element loading method, the load transformation is completed by updating the RBE3 load principal points to the fine model. Load mode b, mapped to the nearest element node: Search for the nearest element based on the loading position, then create an RBE3 element, ensuring that the center point of the RBE3 element is the loading point and the main point of the RBE3 element is the nearest element node, thus achieving load transformation: Load mode c, load redistribution to station nodes: redistributes station loads from the global finite element model to the station nodes of the detailed model. Load mode d, load transformation in local coordinate system: When a load created in the local coordinate system is connected to the station node of the global finite element model through an RBE3 element, the load is transformed to the station node of the refined finite element model. Step 2: Update the model and export the calculations.

[0007] As a preferred technical solution of the method for converting the overall load into the equivalent load of a refined finite element model according to the present invention, the load conversion method a includes the following steps: a1, retrieves the master node and slave node of each loaded RBE3 unit on GFEM; a2, Based on the master node of each RBE3 unit, find the skin node that is closest to each master node in the fine model; a3, Keep the RBE3 loading unit's slave node position unchanged, and update the RBE3 loading unit's master node to the found fine model skin node; a4, complete the load transformation, export the model and save it.

[0008] As a preferred technical solution of the method for converting the overall load into the equivalent load of a refined finite element model according to the present invention, load conversion method b includes the following steps: b1, obtain and record the spatial coordinates of the loading point on the GFEM; b2, for the spatial coordinates of each loading point on the GFEM, find the nearest shell element on the DFEM; b3, retrieve the found shell element node, create RBE3 element, the coordinates of the center node of RBE3 element are consistent with the coordinates of the loading point on GFEM; b4, the created RBE3 element can apply each GFEM load to the corresponding DFEM RBE3 element; b5, complete the load transformation, export the model and save it.

[0009] As a preferred technical solution of the method for converting the overall load into the equivalent load of a refined finite element model according to the present invention, the load conversion method c includes the following steps: c1, Select or define the spanwise coordinate system of GFEM; c2, obtain and record the spatial coordinates of all concentrated loads on the GFEM; c3, sort all loads along the X direction of the spanwise coordinate system, distinguish the loads by the X coordinate in the spanwise coordinate system, and obtain the loads on each station surface; c4, obtain the coordinates of all load loading points at each station, and convert the station load to the station center according to the force translation principle to obtain the resultant force and resultant moment of each station surface; c5, Based on the spatial location of each GFEM station, obtain the skin nodes on the corresponding DFEM station: c6, convert the resultant force and resultant moment on the GFEM station surface to the corresponding DFEM station skin node through the multi-point arrangement method; c7, complete the load transformation, export the model and save it.

[0010] As a preferred technical solution of the method for converting the overall load into the equivalent load of a refined finite element model according to the present invention, the load conversion method d includes the following steps: d1, obtain the master node and slave node of each loaded RBE3 unit on GFEM; d2, Determine the corresponding station face based on the master node of each RBE3 unit; d3, obtain the corresponding DFEM station skin node on the station surface; d4, obtains the load components in the global coordinate system; d5, convert each load (resultant force and resultant moment) at the center point of RBE3 to the corresponding DFEM station skin node (concentrated force) through the multi-point arrangement method; d6, complete the load transformation, export the model and save it.

[0011] Compared with the prior art, the beneficial effects of the present invention are: Based on the characteristics of the structural design iteration process, this invention provides the following four load conversion methods according to different loading requirements: a. For loading via RBE3 elements, load conversion is achieved by updating the RBE3 load master point to the fine model; b. Load conversion is achieved by searching for the nearest element based on the loading position and then creating an RBE3 element, ensuring that the center point of the RBE3 element is the loading point and the RBE3 master point is the nearest element node; c. The station load on the global finite element model is redistributed to the station nodes of the fine model; d. For loads created in the local coordinate system, when connected to the station nodes of the global finite element model via RBE3 elements, load conversion to the station nodes of the fine finite element model is supported. The above technical solution can quickly and accurately convert the overall load on the global finite element model to the fine finite element model, which can meet most work needs and greatly improve the efficiency of converting the overall load to the equivalent load of the fine finite element model, and ensure the accuracy of the load during the structural design iteration process. Attached Figure Description

[0012] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is an architectural design diagram of the present invention; Figure 2 This is a flowchart of the main point update loading of RBE3 unit in this invention; Figure 3 This is a flowchart illustrating the load mapping to the nearest cell node according to the present invention. Figure 4 This is a flowchart illustrating the structural load redistribution to the station nodes according to the present invention. Figure 5 This is a flowchart of load transformation in the local coordinate system of the present invention. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0014] Please see Figure 1-5 The present invention provides the following technical solution: a method for converting a total load into an equivalent load in a refined finite element model, comprising the following steps: Step 1: Set the load transformation mode and select the GFEM model.

[0015] The load conversion methods include the following four: Loading method a (update RBE3 load principal point set): The load conversion is completed by updating the RBE3 load principal points to the fine model through the RBE3 element loading method.

[0016] This method is mainly used in application scenarios where the overall load in the global finite element model is applied through RBE3, and the principal points of the RBE3 elements need to be updated to the fine finite element model.

[0017] Reference Figure 2 As shown, load transformation method a (updating the RBE3 load principal point set) specifically includes the following steps: a1, retrieves the master node and slave node of each loaded RBE3 unit on GFEM; a2, Based on the master node of each RBE3 unit, find the skin node that is closest to each master node in the fine model; a3, Keep the RBE3 loading unit's slave node position unchanged, and update the RBE3 loading unit's master node to the found fine model skin node; a4, complete the load transformation, export the model and save it.

[0018] Load mode b (mapped to nearest element node): Search for the nearest element based on the loading position, and then create an RBE3 element. Ensure that the center point of the RBE3 element is the loading point and the main point of the RBE3 element is the nearest element node to achieve load conversion.

[0019] This method mainly involves preparing the input information for the model that needs to be updated based on the underlying data, and filling in the corresponding Excel table according to the format required by the program, so that it can be used for subsequent model updates.

[0020] Reference Figure 3 As shown, load conversion method b (mapping to the nearest element node) specifically includes the following steps: b1, obtain and record the spatial coordinates of the loading point on the GFEM; b2, for the spatial coordinates of each loading point on the GFEM, find the nearest shell element on the DFEM; b3, retrieve the found shell element node, create RBE3 element, the coordinates of the center node of RBE3 element are consistent with the coordinates of the loading point on GFEM; b4, the created RBE3 element can apply each GFEM load to the corresponding DFEM RBE3 element; b5, complete the load transformation, export the model and save it.

[0021] Load mode c (load redistribution to station nodes) redistributes the station loads on the global finite element model to the station nodes of the detailed model.

[0022] This method is mainly based on the characteristics of the global finite element model. It identifies each station surface and the load on the station surface, merges the station loads to the station center, and then identifies the skin station nodes corresponding to the fine model. Through the multi-point arrangement method, the merged forces and moments are distributed to the skin nodes, thereby realizing the conversion of the global model station load to the fine model station (the multi-point arrangement method satisfies the static equivalence principle and the unchanged force transmission path. The static equivalence principle ensures that the total load and the total pressure center remain unchanged, while the unchanged force transmission path is mainly reflected in ensuring the actual transmission of load).

[0023] Reference Figure 4 As shown, load conversion method c (load redistribution to station nodes) specifically includes the following steps: c1, Select or define the spanwise coordinate system of GFEM; c2, obtain and record the spatial coordinates of all concentrated loads on the GFEM; c3, sort all loads along the X direction of the spanwise coordinate system, distinguish the loads by the X coordinate in the spanwise coordinate system, and obtain the loads on each station surface; c4, obtain the coordinates of all load loading points at each station, and convert the station load to the station center according to the force translation principle to obtain the resultant force and resultant moment of each station surface; c5, Based on the spatial location of each GFEM station, obtain the skin nodes on the corresponding DFEM station: c6, convert the resultant force and resultant moment on the GFEM station surface to the corresponding DFEM station skin node through the multi-point arrangement method; c7, complete the load transformation, export the model and save it. Load mode d (load transformation in local coordinate system): When a load created in the local coordinate system is connected to the station node of the global finite element model through an RBE3 element, the load is transformed to the station node of the fine finite element model.

[0024] This method is mainly for situations where loads in the global model are applied to the station nodes through RBE3 elements, and the loads are applied in the local coordinate system. In this case, the loads in the local coordinate system are first transformed to the global coordinate system through coordinate transformation. Then, the station nodes of the fine model are obtained based on the global model station locations. Finally, the loads are transformed to the fine model through the multi-point arrangement method.

[0025] Reference Figure 5 As shown, load transformation method d (load transformation in local coordinate system) specifically includes the following steps: d1, obtain the master node and slave node of each loaded RBE3 unit on GFEM; d2, Determine the corresponding station face based on the master node of each RBE3 unit; d3, obtain the corresponding DFEM station skin node on the station surface; d4, obtains the load components in the global coordinate system; d5, convert each load (resultant force and resultant moment) at the center point of RBE3 to the corresponding DFEM station skin node (concentrated force) through the multi-point arrangement method; d6. Complete the load transformation, export the model and save it. Step 2: Update the model and export the calculations.

[0026] In this implementation scheme: Based on the characteristics of the structural design iteration process, the present invention provides four load conversion methods according to different loading requirements, which can quickly and accurately convert the overall load on the global finite element model to the fine finite element model, meet most work needs, greatly improve the efficiency of converting the overall load to the equivalent load of the fine finite element model, and ensure the accuracy of the load in the structural design iteration process.

[0027] Furthermore, this invention currently only supports the conversion of concentrated loads.

[0028] In addition, all content not described in detail in this embodiment falls within the scope of existing technology and common knowledge.

[0029] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for converting a total load into an equivalent load in a refined finite element model, characterized by the following steps: Step 1: Set the load transformation mode and select the GFEM model; The load conversion methods include the following four: Loading method a, updating the RBE3 load principal point set: By using the RBE3 element loading method, the load transformation is completed by updating the RBE3 load principal points to the fine model. Load mode b, mapped to the nearest element node: Search for the nearest element based on the loading position, then create an RBE3 element, ensuring that the center point of the RBE3 element is the loading point and the main point of the RBE3 element is the nearest element node, thus achieving load transformation: Load mode c, load redistribution to station nodes: redistributes station loads from the global finite element model to the station nodes of the detailed model. Load mode d, load transformation in local coordinate system: When a load created in the local coordinate system is connected to the station node of the global finite element model through an RBE3 element, the load is transformed to the station node of the refined finite element model. Step 2: Update the model and export the calculations.

2. The method for converting a total load into an equivalent load in a refined finite element model according to claim 1, characterized in that: Load conversion method a includes the following steps: a1, retrieves the master node and slave node of each loaded RBE3 unit on GFEM; a2, Based on the master node of each RBE3 unit, find the skin node that is closest to each master node in the fine model; a3, Keep the RBE3 loading unit's slave node position unchanged, and update the RBE3 loading unit's master node to the found fine model skin node; a4, complete the load transformation, export the model and save it.

3. The method for converting a total load into an equivalent load in a refined finite element model according to claim 1, characterized in that: Load conversion method b includes the following steps: b1, obtain and record the spatial coordinates of the loading point on the GFEM; b2, for the spatial coordinates of each loading point on the GFEM, find the nearest shell element on the DFEM; b3, retrieve the found shell element node, create RBE3 element, the coordinates of the center node of RBE3 element are consistent with the coordinates of the loading point on GFEM; b4, the created RBE3 element can apply each GFEM load to the corresponding DFEM RBE3 element; b5, complete the load transformation, export the model and save it.

4. The method for converting a total load into an equivalent load in a refined finite element model according to claim 1, characterized in that: Load conversion method c includes the following steps: c1, Select or define the spanwise coordinate system of GFEM; c2, obtain and record the spatial coordinates of all concentrated loads on the GFEM; c3, sort all loads along the X direction of the spanwise coordinate system, distinguish the loads by the X coordinate in the spanwise coordinate system, and obtain the loads on each station surface; c4, obtain the coordinates of all load loading points at each station, and convert the station load to the station center according to the force translation principle to obtain the resultant force and resultant moment of each station surface; c5, Based on the spatial location of each GFEM station, obtain the skin nodes on the corresponding DFEM station: c6, convert the resultant force and resultant moment on the GFEM station surface to the corresponding DFEM station skin node through the multi-point arrangement method; c7, complete the load transformation, export the model and save it.

5. The method for converting a total load into an equivalent load in a refined finite element model according to claim 1, characterized in that: Load conversion method d includes the following steps: d1, obtain the master node and slave node of each loaded RBE3 unit on GFEM; d2, Determine the corresponding station face based on the master node of each RBE3 unit; d3, obtain the corresponding DFEM station skin node on the station surface; d4, obtains the load components in the global coordinate system; d5, convert each load (resultant force and resultant moment) at the center point of RBE3 to the corresponding DFEM station skin node (concentrated force) through the multi-point arrangement method; d6, complete the load transformation, export the model and save it.

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