Finite element drop analysis optimization method and device based on numerical calculation and medium

Abstract

The invention relates to a finite element drop analysis optimization method and device based on numerical calculation and a medium, and provides a finite element drop analysis optimization method based on numerical calculation aiming at the actual problem which cannot be completely solved by the existing mode, and the method comprises the following steps: converting a drop height into an equivalent initial speed; generating a collision coordinate system according to the falling direction, and further generating a floor model based on the formed collision coordinate system; calculating the effective duration by measuring the time when the reactive force of the surface nodes of the floor model is reduced to 0 or reaches a set threshold value; a product three-dimensional model and the falling height are input into a set finite element analysis model, the falling process of a product is simulated, and a falling dynamic result and a maximum stress nephogram are obtained. By simplifying and optimizing the finite element model and the calculation process, an enterprise can carry out virtual drop test in the research and development stage, time waste and blind production caused by traditional physical test are avoided, and the accuracy and efficiency of product design are improved.

Description

Technical Field

[0001] This application belongs to the field of product drop analysis, and particularly relates to an optimization method, device, and medium for finite element drop analysis based on numerical calculation. Background Art

[0002] In modern manufacturing, the drop test of products is an important means to verify their durability, reliability, and ability to withstand external force impacts during transportation or use. Currently, many enterprises still rely on traditional physical experiment methods when conducting product research and development and testing. This physical drop test can provide certain reliability verification for products, but it has some significant drawbacks. Especially during the product research and development process, the limitations of physical testing often lead to an extended research and development cycle and insufficient test results. Adequate digital verification is usually not carried out in the initial stage of product design, resulting in modifications and adjustments only when problems occur during the product trial production stage. This traditional method not only prolongs the product development cycle, increases production costs, but also often has design defects that cannot be predicted and solved in a timely manner.

[0003] Finite element analysis (FEA), as a powerful numerical calculation method, has been widely used in aspects such as product structure analysis and mechanical property verification. By simulating the stress state, deformation conditions, and possible failures of an object during the drop process, finite element analysis can predict in advance the performance of a product during an actual drop. When existing finite element analysis methods are applied to drop analysis, there are many operational difficulties, especially for enterprises with relatively weak engineering and technical capabilities, these difficulties are more significant. The common method is to use a mature finite element analysis tool to finely divide the drop scenario and simulate the dynamic behavior of the product during the drop process to achieve the purpose of verifying the product's reliability. Although this method can theoretically provide relatively accurate simulation results, its application faces two core problems, which affect the implementation effect of enterprises in actual research and development.

[0004] Therefore, how to perform drop analysis efficiently and accurately and be able to reasonably estimate the simulation calculation time has become the core problem faced by enterprises. The operational complexity of traditional finite element analysis tools and the uncertainty of calculation time make it difficult for enterprises to fully utilize digital technology for drop testing, thereby affecting the speed and quality of product development. Summary of the Invention

[0005] In view of the limitations of existing physical tests and digital drop analysis tools, which have not been able to fully solve the actual problems faced by enterprises, the present invention proposes a finite element drop analysis optimization method, device and medium based on numerical calculation. By simplifying and optimizing the finite element model and calculation process, enterprises can conduct virtual drop tests during the R & D stage, avoid the time waste and blind production caused by traditional physical tests, and improve the accuracy and efficiency of product design.

[0006] The present invention provides a finite element drop analysis optimization method based on numerical calculation, including the following steps: S1, converting the drop height into an equivalent initial velocity; the purpose of this step is to simplify the calculation process and shorten the calculation time; S2, based on the result of S1 and the situation of the product contacting the ground, generating a collision coordinate system according to the drop direction, and then generating a floor model based on the formed collision coordinate system; S3, calculating the effective duration by measuring the time when the reaction force of the surface nodes of the floor model is reduced to 0 or reaches a set threshold; the effective duration refers to the time from when the product contacts the floor model to the rebound; and then obtaining a set finite element analysis model; S4, inputting the three-dimensional model of the product and the drop height into the set finite element analysis model, simulating the drop process of the product, and obtaining the drop dynamic result and the maximum stress nephogram.

[0007] Further, the formula for converting the drop height into an equivalent initial velocity is:

[0008] where: v is the velocity of the object when it contacts the ground (unit: m / s), g is the acceleration due to gravity (taking ), and h is the drop height of the model (unit: m).

[0009] In traditional drop analysis simulations, the product freely falls from rest, and engineers need to set the initial height of the object and the gravitational force to simulate its drop process. Each drop simulation requires step-by-step calculation of data such as displacement, velocity, and acceleration at each moment, which is time-consuming and computationally complex. In this application, by converting the drop height into an equivalent initial velocity, computational resources can be saved. Specifically, directly converting the given drop height h into the initial velocity v can skip the long free-fall simulation starting from zero velocity and directly perform impact analysis at the initial velocity. This not only simplifies the calculation steps but also effectively prevents the situation where a large amount of computational time is wasted due to the linear movement of the finite element model in dynamic calculations. Moreover, the calculation starting from the form of contact is beneficial for predicting the collision time of the model during dropping, that is, the time interval from when the model contacts the floor model to when it completely rebounds and leaves the floor model for the first time. By predicting the collision time, the calculation time can be further shortened, the calculation efficiency can be improved, and the situation where the drop time is difficult to estimate and repeated debugging is required can be avoided.

[0010] Furthermore, the specific process of S2 includes: S2.1, By analyzing all the nodes of the product's 3D model in the global coordinate system, determine the limit position point along the dropping direction, and set this limit position point as the collision point; the global coordinate system refers to the original coordinate system when drawing the product's 3D model; S2.2, Set the collision point as the origin of the collision coordinate system, set the dropping direction as a new axis of the collision coordinate system, and use the determined new axis as the normal vector of the plane where the other two new axes are located, and then determine the directions of the other two new axes; S2.3, Calculate the size of the floor model in the collision coordinate system according to the collision coordinate system to form the floor model; S2.4, Construct a rotation coordinate system at the geometric center of gravity point of the product 3D model, and adjust the dropping angle of the product model through the rotation coordinate system to establish an association between the rotated floor model and the collision coordinate system, ensuring that its contact surface precisely adapts to the collision conditions of the product.

[0011] When most enterprises conduct finite element drop analysis, usually only the 3D model of the product is provided, without including the floor model related to the product drop process. The role of the floor model is not only to serve as a "hard" contact surface. It determines the rebound, deformation, and transmission of collision forces of the product after dropping. Therefore, accurately simulating the contact and collision between the floor model and the product is the key to achieving accurate drop analysis.

[0012] The core of this collision coordinate system lies in precisely positioning the collision point and establishing a new reference system that meets the requirements of drop analysis through redefining the coordinate axes.

[0013] Furthermore, the specific process of step S2.3 is: S2.3.1. Determine the thickness of the floor model according to the set value of the dropping direction; S2.3.2. Determine the length and width of the floor model based on the calculation results in the X and Y axis directions of the collision coordinate system: Detect the coordinate values of all nodes of the product model in the X-axis direction of the global coordinate system, and determine the maximum span of the product model in the global X-axis direction by the difference between the obtained maximum value and minimum value; with the collision coordinate point as the center, extend integer multiples of the maximum span in the positive and negative directions of the X-axis of the collision coordinate system respectively to form the length of the floor model; Detect the coordinate values of all nodes of the product model in the Y-axis direction of the global coordinate system, and determine the maximum span of the product model in the global Y-axis direction by the difference between the obtained maximum value and minimum value; with the collision coordinate point as the center, extend integer multiples of the maximum span in the positive and negative directions of the Y-axis of the collision coordinate system respectively to form the length of the floor model.

[0014] Furthermore, the specific process of constructing the rotation coordinate system in S2.4 includes: The input values of the rotation matrix are the rotation angles around the X, Y, and Z axes of the global coordinate system 、 、 ; The rotation matrix can be expressed as:

[0015] Among them, the rotation matrices around the X, Y, and Z axes are respectively:

[0016] In the formula, R is the rotation matrix, is the rotation matrix around the X axis, is the rotation matrix around the Y axis, is the rotation matrix around the Z axis.

[0017] Through the product of the above matrices, the initial plane of the floor model can be rotationally transformed to match the specified dropping angle. The rotated floor model is associated with the collision coordinate system to ensure that its contact surface precisely adapts to the collision conditions of the product while maintaining the flexibility of dynamic adjustment. This method effectively reduces the complexity of manually adjusting the angle, improves the operation efficiency and the accuracy of the analysis results. Through reverse thinking, changing the generation direction of the floor model can change the dropping direction and achieve the same angle change effect.

[0018] Furthermore, the calculation formula for the effective duration is:

[0019] In the formula, is the normal reaction force of the i-th contact node on the surface of the floor model at time t; N represents the total number of contact nodes on the surface of the floor model; is the set reaction force threshold; is the duration of contact between the model and the floor model, that is, the time from when the model contacts the ground until the bounce is completed.

[0020] In the drop analysis, accurately estimating the time from when the model contacts the floor model until the bounce is a key step, because this time period determines the effective calculation duration of the solution process. Therefore, by predicting and controlling the time from the model's drop to the bounce, the calculation efficiency can be significantly improved and the ineffective calculations can be reduced.

[0021] In the finite element model, the nodes on the surface of the floor model will contact the model and exert reaction forces. According to the principles of physics, when the model contacts the floor model and starts to bounce, the reaction force will gradually decrease. By monitoring the reaction forces of each node on the surface of the floor model in real time, the contact state between the model and the floor model and the bounce process can be inferred.

[0022] When the reaction force gradually decreases to near zero, it indicates that the contact between the model and the floor model is gradually ending, that is, the bounce process is basically completed. To determine the effective calculation duration, a threshold can be set. When the reaction forces of all nodes on the surface of the floor model are less than this threshold, the system will judge that the model has completed contact and started to bounce, and then terminate the solution process.

[0023] Furthermore, calculating the effective duration includes the following steps: S3.1, Extract reaction force data: Monitor the reaction forces of all nodes on the surface of the floor model in real time, and obtain the reaction force values of the nodes at each time step; S3.2, Judge the zero value state of the reaction force: Set a threshold. When the reaction force values of all nodes on the surface of the floor model are lower than this threshold, it is considered that the model has completed contact with the floor model.

[0024] S3.3, Judge the contact end time: When the reaction forces of all nodes are close to zero, calculate the contact end time between the model and the floor model, which marks the start of the bounce.

[0025] S3.4, Breakpoint command control: Through the calculated contact end time, when the state of the product bouncing off the ground appears in the solution process, a stop command is issued to stop the solution process and eliminate the remaining ineffective calculation time.

[0026] Furthermore, the specific process of step S4 is as follows: S4.1. Obtain relative displacement data based on the node displacement data of the product model recorded during the solution process of the finite element analysis model, where the node displacement data describes the motion state of each node in time steps. S4.2. Calculate the absolute position of the nodes by adding the relative displacement data to the original coordinates, and then reconstruct the instantaneous geometric state of the product model, that is, the geometric states at different time frames. S4.3. Connect the geometric states at different time frames in sequence according to the time order to form a complete dynamic sequence. S4.4. Adjust the mapping of the time axis to be consistent with the simulation time step. S4.5. Obtain the drop dynamic result of the product model from a fixed perspective. S4.6. Traverse the stress values of the product model, obtain the time frame corresponding to the maximum stress as the key frame, extract the stress distribution data corresponding to the key frame to generate the maximum stress nephogram, and this nephogram visually presents the stress distribution state on the surface and inside of the model in the form of a color gradient.

[0027] In the post-processing stage of the finite element drop analysis, how to visually display the drop state of the model is the core content of the entire analysis process. The display effect directly affects the interpretation of the results and the efficiency of subsequent design optimization. In order to restore the dynamic behavior of the model as accurately as possible and highlight the key stress states, this application combines two methods: drop animation and maximum stress nephogram. Through the organic combination of dynamic and static displays, it comprehensively presents the response state of the model during the drop process. The implementation of this technical solution involves multiple key links such as data extraction, algorithm processing, and visualization rendering, covering the entire process from physical simulation results to visual output.

[0028] An optimized device for finite element drop analysis based on numerical calculation, comprising: A drop conversion module for converting the drop height into an equivalent initial velocity. A drop direction adjustment module connected to the conversion module. Based on the result of the drop conversion module and the situation of the product contacting the ground, generate a collision coordinate system according to the drop direction, and then generate a floor model based on the formed collision coordinate system. A drop time identification module connected to the drop direction adjustment module. Based on the result of the drop direction adjustment module, calculate the effective duration by measuring the time when the reaction force of the nodes on the surface of the floor model reduces to 0 or reaches a set threshold; where the effective duration refers to the time from when the product contacts the floor model to the bounce; form a set finite element analysis model. A drop solution module connected to the drop time identification module, used to simulate the drop process of the product by inputting the three-dimensional model of the product and the drop height into the set finite element analysis model, and obtain the drop dynamic result and the maximum stress nephogram.

[0029] A computer-readable medium includes a memory and one or more processors. Executable code is stored in the memory. When the one or more processors execute the executable code, it is used to implement the finite element drop analysis optimization method based on numerical calculation described above.

[0030] Beneficial effects: This application is a finite element drop analysis optimization method, device, and medium based on numerical calculation. The drop height is converted into an equivalent initial velocity, effectively shortening the model calculation time. The collision coordinate system and the floor model are automatically generated, improving the calculation accuracy of the effective duration, significantly improving the calculation efficiency, reducing ineffective calculations. By simplifying and optimizing the finite element model and calculation process, enterprises can conduct virtual drop tests during the R & D stage, avoiding the time waste and blind production caused by traditional physical tests, and improving the accuracy and efficiency of product design. Description of the Drawings

[0031] Figure 1 It is a three-dimensional structure schematic diagram of a dropped product with a collision coordinate system; Figure 2 It is a structure schematic diagram of the generation of the collision coordinate system and the floor model; Figure 3 It is a structure schematic diagram before the adjustment of the rotation coordinate system; Figure 4 It is a structure schematic diagram of adjusting the drop angle of the product through the rotation coordinate system; Figure 5 It is the maximum stress nephogram of the application example; Figure 6 It is the flowchart of Embodiment 1. Detailed Embodiments

[0032] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] Embodiment 1 A finite element drop analysis optimization method based on numerical calculation, the flowchart is as Figure 6 shown, and includes the following steps: S1. Convert the drop height into an equivalent initial velocity; the purpose of this step is to simplify the calculation process and shorten the calculation time; the formula for converting the drop height into an equivalent initial velocity is:

[0034] Where: v is the velocity of the object when it contacts the ground (unit: m / s), g is the acceleration due to gravity (take ), h is the drop height of the model (unit: m).

[0035] S2. Based on the result of S1 and the contact situation between the product and the ground, generate a collision coordinate system according to the drop direction, and then generate a floor model based on the formed collision coordinate system; the specific process includes: S2.1. By analyzing all nodes of the three-dimensional model of the product in the global coordinate system, judge the limit position point along the drop direction, and set this limit position point as the collision point; When the drop direction is an axis in the global coordinate system (for example, the -Z axis direction), it is necessary to retrieve the coordinate values of this axis (for example, the -Z axis direction) of all nodes in the global coordinate system, and select the point with the largest absolute value of the coordinate value of this axis (for example, the -Z axis direction) as the collision point, that is .

[0036] S2.2. Set the collision point as the origin of the collision coordinate system, set the drop direction as a new axis of the collision coordinate system, and use the determined new axis as the normal vector of the plane where the other two new axes are located to determine the directions of the other two new axes; this collision point represents the part of the model that first contacts the impact surface in the drop direction and is the core basis for defining the new coordinate system. After the collision point is determined, a new collision coordinate system is generated. The origin of the collision coordinate system is the position of the above-mentioned collision point, and the direction of the new axis of the collision coordinate system (for example, the -Z axis of the collision coordinate system) is the same as the drop direction, that is, pointing to the axis of the global coordinate system (for example, the -Z axis direction). The X-Y plane of the new collision coordinate system is perpendicular to the -Z axis direction here and is defined by the normal vector of this plane at the collision point. In this way, the three coordinate axes (X, Y, Z) of the collision coordinate system are re-determined based on the collision point and the drop direction.

[0037] S2.3. Calculate the size of the floor model in the collision coordinate system according to the collision coordinate system to form the floor model; the specific process is: S2.3.1. Determine the thickness of the floor model according to the set value of the drop direction; S2.3.2. Determine the length and width of the floor model through the calculation results in the X and Y axis directions of the collision coordinate system: Detect the coordinate values of all nodes of the product model in the X-axis direction of the global coordinate system, and determine the maximum span of the product model in the global X-axis direction by the difference between the obtained maximum value and minimum value; with the collision coordinate point as the center, extend integer multiples of the maximum span in the positive and negative directions of the X-axis of the collision coordinate system respectively to form the length of the floor model; Detect the coordinate values of all nodes of the product model in the Y-axis direction of the global coordinate system, and determine the maximum span of the product model in the global Y-axis direction by the difference between the obtained maximum value and minimum value; with the collision coordinate point as the center, extend integer multiples of the maximum span in the positive and negative directions of the Y-axis of the collision coordinate system respectively to form the length of the floor model.

[0038] When the dropping axis is the -Z axis, the specific algorithm model and formula introduction examples are as follows: 1. Let the node set of the three-dimensional model be , and the global coordinate of node be ( x i ,y i , z i ); 2. The dropping direction is the -Z axis of the global coordinate system. Retrieve all nodes with negative values in the Z-axis direction of the global coordinate system. Then the -Z axis coordinate of the collision point P based on the global coordinate system is , and the corresponding node coordinates are ([[]] x p ,y p , z p ); 3. The origin of the collision coordinate system is O = ( x p ,y p , z p ).

[0039] 4. The new -Z axis direction of the collision coordinate system is the dropping direction (here it is the global -Z direction according to the example). The new X-Y plane is defined by the origin O and its plane normal vector as: In the global coordinate system, it is shown as n XY = (0, 0, -1).

[0040] At this stage, the core task of the algorithm is to automatically generate the collision coordinate system according to the model dropping direction to achieve accurate switching of the coordinate system. By traversing the node data of the model, the system can quickly determine the collision point and its corresponding spatial position, and redefine the coordinate axes based on this. This process simplifies the generation logic of the floor model and lays an accurate mathematical and geometric foundation for subsequent dropping analysis.

[0041] The process of generating a floor model based on the collision coordinate system aims to achieve an accurate fit between the floor model and the product model, while ensuring that the dimensions of the floor model can effectively cover the requirements of the drop simulation. The thickness of the floor model is determined by the set value in the drop direction (i.e., the -Z axis direction of the collision coordinate system in the above example), and the length and width of the floor model are determined by the calculation results in the X and Y axis directions of the collision coordinate system. To further enhance the generality and adaptability of the floor model, corresponding algorithms need to be designed to automatically calculate and generate the dimensions of the floor model in the collision coordinate system.

[0042] To determine the length of the floor model in the X axis direction of the collision coordinate system, it is necessary to retrieve the coordinate values of all nodes of the product model in the X axis direction of the global coordinate system and separately take out the maximum value X max and the minimum value X min . By calculating the difference between the two, the maximum span of the model in the global X axis direction can be obtained:

[0043] This span represents the coverage range of the model in the global X axis direction.

[0044] The length of the floor model in the X axis direction of the collision coordinate system adopts a symmetric structure centered on the collision coordinate point. It extends n times (n is an input value and can be adjusted) of the maximum span of the global X axis in both the positive and negative directions:

[0045] In this way, the total length of the floor model in the X axis direction is , which can basically cover the drop range of the model and its potential impact range.

[0046] Similarly, the calculation method for the length of the floor model in the Y axis direction of the collision coordinate system is the same. First, retrieve the maximum value of all nodes of the model in the Y axis direction of the global coordinate system Y max and the minimum value Y min , and calculate the maximum span in the global Y axis direction:

[0047] Then generate the length of the floor model with a symmetric structure in the Y axis direction of the collision coordinate system:

[0048] The total dimensions of the floor model in the collision coordinate system are determined as: Length in the X axis direction:

[0049] Length in the Y axis direction:

[0050] Thickness in the Z-axis direction: fixed value or scenario-adjustable value.

[0051] The size expansion multiple of the floor model (such as n times in the X and Y axis directions) can be adjusted according to the actual application scenario to better meet the requirements of complex drop tests.

[0052] S2.4. Construct a rotation coordinate system, and adjust the drop angle of the product model through the rotation coordinate system so that the rotated floor model is associated with the collision coordinate system to ensure that its contact surface precisely adapts to the collision conditions of the product. The specific process includes: The input values of the rotation matrix are the rotation angles around the X, Y, and Z axes of the global coordinate system 、 、 , and the rotation matrix can be expressed as:

[0053] Among them, the rotation matrices around the X, Y, and Z axes are respectively:

[0054] In the formula, R is the rotation matrix, is the rotation matrix around the X axis, is the rotation matrix around the Y axis, is the rotation matrix around the Z axis.

[0055] Through the product of the above matrices, the initial plane of the floor model can be rotationally transformed to match the specified drop angle. The rotated floor model is associated with the collision coordinate system to ensure that its contact surface precisely adapts to the collision conditions of the product while maintaining the flexibility of dynamic adjustment. This method effectively reduces the complexity of manually adjusting the angle, improves the operation efficiency and the accuracy of the analysis results. Through reverse thinking, changing the generation direction of the floor model can change the drop direction and achieve the same angle change effect.

[0056] S3. Calculate the effective duration by measuring the time when the normal reaction force of the surface nodes of the floor model is reduced to 0 or reaches the set threshold; the effective duration refers to the time from when the product contacts the floor model to when it rebounds; and then obtain the set finite element analysis model; The calculation formula for the effective duration is:

[0057] is the normal reaction force of the i th contact node on the surface of the floor model at time t; NRepresents the total number of contact nodes on the surface of the floor model; Is the set reaction force threshold; Is the duration of contact between the model and the floor model, that is, the time from when the model touches the ground until the bounce is completed.

[0058] Specifically includes the following steps: S3.1, Extract reaction force data: Monitor the reaction forces of all nodes on the surface of the floor model in real time, and obtain the reaction force values of the nodes at each time step; S3.2, Judge the zero value state of the reaction force: Set a threshold. When the reaction force values of all nodes on the surface of the floor model are lower than this threshold, it is considered that the model has completed contact with the floor model.

[0059] S3.3, Judge the contact end time: When the reaction forces of all nodes are close to zero, calculate the contact end time between the model and the floor model, marking the start of the bounce.

[0060] S3.4, Breakpoint command control: Through the calculated contact end time, when the state of the product bouncing off the ground appears during the solution process, issue a stop command to stop the solution process and eliminate the remaining invalid calculation time.

[0061] S4, By inputting the product 3D model and the drop height into the set finite element analysis model, simulate the drop process of the product to obtain the drop dynamic results and the maximum stress nephogram. The specific process is as follows: S4.1, Based on the node displacement data of the product model recorded during the solution process of the finite element analysis model, obtain the relative displacement data, where the node displacement data describes the motion state of each node in time steps; S4.2, Calculate the absolute position of the node by adding the relative displacement data to the original coordinates, and then reconstruct the instantaneous geometric state of the product model, that is, the geometric state at different time frames; S4.3, Connect the geometric states at different time frames in sequence according to the time order to form a complete dynamic sequence; S4.4, Adjust the mapping of the time axis to be consistent with the simulation time step; S4.5, Obtain the drop dynamic results of the product model from a fixed perspective; S4.6, Traverse the stress values of the product model, obtain the time frame corresponding to the maximum stress as the key frame, and extract the stress distribution data corresponding to the key frame to generate the maximum stress nephogram, which visually presents the stress distribution state on the surface and inside of the model in the form of a color gradient.

[0062] The generation of the drop animation is based on the node displacement data recorded during the solution process. These data are stored in the result file and describe the motion state of each node in time steps. To generate the animation, these displacement data need to be extracted, processed, and reconstructed. Specifically, the extracted displacement data exist in the form of relative displacements, so the initial coordinates of the nodes need to be added back to calculate the absolute positions, thereby reconstructing the instantaneous geometric state of the model. This processing process relies on numerical calculation methods to ensure the accuracy of the displacement data. During the animation generation stage, the geometric states of different time frames are connected in sequence to form a complete dynamic sequence. To synchronize the physical time with the animation time, the mapping of the time axis needs to be consistent with the simulation time steps. To improve the display effect, a fixed viewing angle can be used to show the motion effect of the model.

[0063] The generation of the maximum stress contour plot aims to show the extreme stress state of the model during the drop process by locking the key time frames. During the simulation, the distribution data of the equivalent stress are recorded in the result file of each time step. By retrieving these time steps one by one, the time point when the model is under the maximum stress and its corresponding stress distribution can be found. After locking the key time frames, the corresponding stress distribution data are extracted and a contour plot is generated. The contour plot visually presents the stress distribution state on the surface and inside of the model in the form of a color gradient.

[0064] Embodiment 2 An optimized device for finite element drop analysis based on numerical calculation, comprising: A drop conversion module for converting the drop height into an equivalent initial velocity; A drop direction adjustment module connected to the conversion module. Based on the result of the drop conversion module and the situation of the product contacting the ground, a collision coordinate system is generated according to the drop direction, and then a floor model is generated based on the formed collision coordinate system; A drop time identification module connected to the drop direction adjustment module. Based on the result of the drop direction adjustment module, the effective duration is calculated by measuring the time when the reaction force of the nodes on the surface of the floor model is reduced to 0 or reaches a set threshold; where the effective duration refers to the time from when the product contacts the floor model to the bounce; and a set finite element analysis model is formed; A drop solution module connected to the drop time identification module for simulating the drop process of the product by inputting the three-dimensional model of the product and the drop height into the set finite element analysis model to obtain the drop dynamic results and the maximum stress contour plot.

[0065] Embodiment 3 A computer-readable medium includes a memory and one or more processors. Executable code is stored in the memory. When the one or more processors execute the executable code, it is used to implement the optimized method for finite element drop analysis based on numerical calculation described in Embodiment 1.

[0066] Application Example The global coordinate system is the reference coordinate system for the model drawing stage and can be directly read from the model file. The drop height is 1.3 m, and the product material is stainless steel.

[0067] As Figure 1 and Figure 2 shown, the model diagram has a collision coordinate system. The collision coordinate system is generated autonomously. The collision point is the extreme far point of the model in the drop direction. One axis is generated along the axis referring to the drop direction, and the other two axes can be generated arbitrarily (here it is defaulted to refer to the axes of the global coordinate system). According to the collision coordinate system, a floor model display diagram is generated, and the floor model in the drop direction is generated autonomously by inputting the thickness and aspect ratio "n" of the floor model.

[0068] The origin of the rotation coordinate system is the geometric center of gravity of the model. The three axes refer to the respective axes of the global coordinate system, and the corresponding floor model is generated by inputting the rotation angles around the X, Y, and Z axes respectively. Through reverse thinking, the drop direction is changed by changing the generation direction of the floor model.

[0069] The rotation coordinate system is used to adjust the drop angle of the model. For example, rotating counterclockwise by 45° around the X axis (the X' axis in the figure) of the rotation coordinate system can change from Figure 3 the drop angle to Figure 4 the drop angle. Figure 3 and Figure 4 The coordinate systems in

[0070] As Figure 5 shown is the stress nephogram corresponding to the key frame of the maximum drop stress. The legend colors on the left side from red to green to blue to gray represent the stress values from large to small, and its unit is MPa.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still modify the specific implementation manners of the present invention or make equivalent substitutions. Any modification or equivalent substitution without departing from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A finite element drop analysis optimization method based on numerical calculation, characterized in that, It includes the following steps: S1. Convert the drop height into an equivalent initial velocity; S2. Based on the result of S1 and the situation of the product contacting the ground, generate a collision coordinate system according to the drop direction, and then generate a floor model based on the formed collision coordinate system; S3. Calculate the effective duration by measuring the time when the reaction force of the surface nodes of the floor model is reduced to 0 or reaches a set threshold; where the effective duration refers to the time from when the product contacts the floor model to the rebound; and then obtain the set finite element analysis model; S4. Input the three-dimensional model of the product and the drop height into the set finite element analysis model, simulate the drop process of the product, and obtain the drop dynamic result and the maximum stress nephogram.

2. The finite element drop analysis optimization method based on numerical calculation according to claim 1, characterized in that The specific process of S2 includes: S2.

1. By analyzing all nodes of the three-dimensional model of the product in the global coordinate system, determine the limit position point along the drop direction, and set this limit position point as the collision point; S2.

2. Set the collision point as the origin of the collision coordinate system, set the drop direction as a new axis of the collision coordinate system, and use the determined new axis as the normal vector of the plane where the other two new axes are located, and then determine the directions of the other two new axes in the collision coordinate system; S2.

3. Calculate the size of the floor model in the collision coordinate system according to the collision coordinate system to form the floor model; S2.

4. Construct a rotation coordinate system, and adjust the drop angle of the product model through the rotation coordinate system so that the rotated floor model is associated with the collision coordinate system.

3. The finite element drop analysis optimization method based on numerical calculation according to claim 2, wherein The specific process of step S2.3 is: S2.3.

1. Determine the thickness of the floor model according to the set value of the drop direction; S2.3.

2. Determine the length and width of the floor model through the calculation results in the X and Y axis directions of the collision coordinate system: Detect the coordinate values of all nodes of the product model in the X-axis direction of the global coordinate system, and determine the maximum span of the product model in the global X-axis direction through the difference between the obtained maximum value and minimum value; with the collision coordinate point as the center, extend integer multiples of the maximum span in the positive and negative directions of the X-axis of the collision coordinate system respectively to form the length of the floor model; Detect the coordinate values of all nodes of the product model in the Y-axis direction of the global coordinate system, and determine the maximum span of the product model in the global Y-axis direction through the difference between the obtained maximum value and minimum value; with the collision coordinate point as the center, extend integer multiples of the maximum span in the positive and negative directions of the Y-axis of the collision coordinate system respectively to form the length of the floor model.

4. The finite element drop analysis optimization method based on numerical calculation according to claim 2, wherein The specific process of constructing the rotation coordinate system in S2.4 includes: The input values of the rotation matrix are the rotation angles about the X, Y, and Z axes of the global coordinate system 、 、 ; The rotation matrix can be expressed as: Among them, the rotation matrices around the X, Y, and Z axes are respectively: wherein, R is a rotation matrix, is the rotation matrix about the X-axis, is the rotation matrix about the Y-axis, is the rotation matrix about the Z-axis.

5. The finite element drop analysis optimization method based on numerical calculation according to claim 2, characterized in that The calculation formula for the effective duration in step S3 is: wherein, is the normal reaction force of the i th contact node on the surface of the floor model at time t ; N Represents the total number of contact nodes on the surface of the floor model; Is the set reaction force threshold; Is the duration of contact between the product model and the floor model, that is, the time from when the product model starts to contact the floor model until the bounce is completed.

6. The finite element drop analysis optimization method based on numerical calculation according to claim 2, wherein The method for calculating the effective duration includes the following steps: S3.

1. Extract the reaction force data: Monitor the reaction forces of all surface nodes of the floor model in real time, and obtain the reaction force values of the nodes at each time step; S3.

2. Judge the zero value state of the reaction force: Set a threshold, and when the reaction force values of all surface nodes of the floor model are lower than this threshold, the contact between the product model and the floor model is completed; S3.

3. Determine the contact end time: When the reaction forces of all nodes are close to zero, calculate the contact end time between the calculation model and the floor model, which marks the start of the rebound. S3.

4. Breakpoint command control: Based on the calculated contact end time, when the product rebounds and detaches from the ground during the solution process, issue a stop command to stop the solution process and eliminate the remaining invalid calculation time.

7. The finite element drop analysis optimization method based on numerical calculation according to claim 2, characterized in that The specific process of step S4 is as follows: S4.

1. Based on the node displacement data of the product model recorded during the solution process of the finite element analysis model, obtain the relative displacement data, where the node displacement data describes the motion state of each node in time steps. S4.

2. Calculate the absolute position of the nodes by adding the relative displacement data to the original coordinates, and then reconstruct the instantaneous geometric state of the product model, that is, the geometric state at different time frames. S4.

3. Connect the geometric states at different time frames in sequence according to the time order to form a complete dynamic sequence. S4.

4. Adjust the mapping of the time axis to be consistent with the simulation time step. S4.

5. Obtain the drop dynamic result of the product model from a fixed perspective. S4.

6. Traverse the stress values of the product model, obtain the time frame corresponding to the maximum stress as the key frame, and extract the stress distribution data corresponding to the key frame to generate the maximum stress nephogram.

8. A finite element drop analysis optimization device based on numerical calculation, characterized in that Including: A drop conversion module for converting the drop height into an equivalent initial velocity. A drop direction adjustment module connected to the conversion module. Based on the result of the drop conversion module and the contact situation between the product and the ground, generate a collision coordinate system according to the drop direction, and then generate a floor model based on the formed collision coordinate system. A drop time identification module connected to the drop direction adjustment module. Based on the result of the drop direction adjustment module, calculate the effective duration by measuring the time when the reaction force of the surface nodes of the floor model decreases to 0 or reaches a set threshold; the effective duration refers to the time from when the product contacts the floor model to the rebound; form a set finite element analysis model. A drop solution module connected to the drop time identification module for simulating the drop process of the product by inputting the three-dimensional model of the product and the drop height into the set finite element analysis model to obtain the drop dynamic result and the maximum stress nephogram.

9. A computer-readable medium includes a memory and one or more processors. The memory stores executable code. When the one or more processors execute the executable code, it is used to implement the finite element drop analysis optimization method based on numerical calculation according to any one of claims 1 to 7.

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