EPE foam finite element simulation and experimental data benchmarking method

Abstract

The invention provides an EPE foam finite element simulation and experimental data benchmarking method which comprises the following steps: taking an EPE foam experimental sample, carrying out vertical free falling motion at a certain height, recording the falling height, leaving a circular ink trace on EPE foam after a steel ball falls, and recording the maximum diameter of the circular ink trace; ground, EPE foam and steel ball models which are the same as those of an experiment are established in finite element simulation, simulation is conducted at the same falling height, the whole falling animation of the EPE foam impacted by the steel ball and the deformation amount of deformation of the EPE foam are obtained, and the maximum circle diameter of contact between the EPE foam and the steel ball is recorded; experimental data is taken as a standard, and simulation data is changed to be close to real experimental data. Simulation data and experimental data are subjected to benchmarking, so that the finite element simulation reliability is improved, the packaging scheme failure risk is greatly reduced, and the cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of packaging material simulation, and particularly relates to a method for comparing finite element simulation and experimental data of EPE foam. Background Art

[0002] As a powerful engineering analysis tool, finite element simulation has been widely used in many fields, such as popular fields like aerospace, electronics industry, and civil engineering. Its function can simulate the working conditions, predict possible problems and improve them in advance to reduce risks and costs. However, its application in the packaging field is less due to reasons such as unstable packaging material parameters and less literature. As a common packaging material, EPE foam is often used for cushioning packaging, but its application in finite element simulation is less and data is difficult to collect. And the simulation of EPE packaging is necessary, as it can predict the feasibility of packaging design in advance and reduce a lot of unnecessary costs, etc. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for comparing finite element simulation and experimental data of EPE foam, aiming to solve the problem of the lack of utilization of finite element simulation technology for packaging materials in the prior art.

[0004] The present invention is realized as follows. A method for comparing finite element simulation and experimental data of EPE foam, the method includes the following steps:

[0005] Step S1: Take an EPE foam experimental sample, fix one side of the EPE foam on the experimental tabletop, take a solid steel ball with a fixed mass and a fixed diameter, wrap the surface of the steel ball with erasable ink, conduct a vertical free-fall motion at a certain height and record the drop height. After the steel ball drops, it will leave a circular ink mark on the EPE foam, and record the maximum diameter of the circular ink mark.

[0006] Step S2: Establish models of the ground, EPE foam, and steel ball in the finite element simulation that are the same as those in the experiment, simulate at the same drop height, obtain the entire drop animation of the steel ball hitting the EPE foam and the deformation amount of the EPE foam deformation, and record the maximum circular diameter of the contact between the EPE foam and the steel ball.

[0007] Step S3: Compare the maximum diameter of the ink mark obtained from the experiment with the maximum circular diameter of the contact between the EPE foam and the steel ball obtained from the simulation, and take the experimental data as the standard to make the simulation data approach the experimental real data by changing the simulation data.

[0008] A further technical solution of the present invention is: Step S2 includes the following steps:

[0009] Step S21: Establish models of the ground, EPE foam, and steel ball that are the same as those in the experiment;

[0010] Step S22: Define material properties. The ground and the steel ball are made of structural steel, and the ground is a rigid body. The stress-strain curve of the EPE material is defined through a compression test.

[0011] Step S23: Perform mesh generation. The system default mesh generation is used.

[0012] Step S24: Perform contact settings. A bonded contact is set on one side of the ground and the EPE foam, and a frictionless contact is set between the steel ball and the EPE foam.

[0013] A further technical solution of the present invention is that step S2 further includes the following steps:

[0014] Step S25: Analysis settings. The impact velocity when the steel ball just touches the EPE is obtained by the free fall formula where g is the acceleration due to gravity and h is the drop height. The minimum set time needs to ensure that there is enough rebound time after the steel ball impacts the EPE foam.

[0015] Step S26: After the steel ball impacts the EPE foam, a drop animation will be generated, and the stress-strain information of all components will be generated. The maximum deformation point is found through the data generated by the LS-prepost software, and the maximum circular diameter of the EPE foam in contact with the steel ball after being impacted by the steel ball at the maximum deformation moment is measured using a tool.

[0016] A further technical solution of the present invention is that in step S3, the stress-strain curve in the elastic stage of the EPE is changed, and the stress-strain curve in the plastic stage remains unchanged. When the slope of the stress-strain curve in the elastic stage is increased or decreased, if the simulation result is more deviated from the experimental result, it means that this situation does not meet the requirements; if the simulation result is closer to the experimental result, the result of this situation is retained.

[0017] A further technical solution of the present invention is that in step S3, the stress-strain curve in the plastic stage of the EPE is changed, and the stress-strain curve in the elastic stage remains unchanged. When the slope of the stress-strain curve in the plastic stage is increased or decreased, if the simulation result is more deviated from the experimental result, it means that this situation does not meet the requirements; if the simulation result is closer to the experimental result, the result of this situation is retained.

[0018] A further technical solution of the present invention is that in step S3, when increasing the slope of the stress-strain curve in the elastic stage meets the requirements, then increase or decrease the stress-strain curve in the plastic stage to observe whether it is closer to the experimental result.

[0019] The beneficial effects of the present invention are: Comparing the simulation data with the experimental data improves the reliability of the finite element simulation, greatly reduces the risk of packaging plan failure, and reduces costs. Description of the Drawings

[0020] Figure 1 is the flowchart of the method of the present invention;

[0021] Figure 2 is the schematic diagram during the experimental operation of the present invention;

[0022] Figure 3 is the schematic diagram of the ink trace left on the EPE after the experimental operation of the present invention;

[0023] Figure 4 is the schematic diagram during the finite element simulation operation of the present invention;

[0024] Figure 5 is the schematic diagram of the contact between the steel ball and the EPE in the finite element simulation of the present invention. Specific embodiments

[0025] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0026] A method for benchmarking finite element simulation and experimental data of EPE foam provided by the present invention, the method comprising the following steps:

[0027] Step S1: Take an EPE foam experimental sample, fix one side of the EPE foam on the experimental tabletop, take a solid steel ball with a fixed mass and a fixed diameter, wrap the surface of the steel ball with erasable ink, perform a vertical free fall motion at a certain height and record the drop height. After the steel ball drops, a circular ink trace will be left on the EPE foam, and record the maximum diameter of the circular ink trace;

[0028] Step S2: Establish models of the ground, EPE foam and steel ball identical to the experiment in the finite element simulation, simulate at the same drop height, obtain the entire drop animation of the steel ball hitting the EPE foam and the deformation amount of the EPE foam deformation, and record the maximum circular diameter of the contact between the EPE foam and the steel ball;

[0029] Step S3: Compare the maximum diameter of the ink trace obtained from the experiment with the maximum circular diameter of the contact between the EPE foam and the steel ball obtained from the simulation, and take the experimental data as the standard to approximate the experimental real data by changing the simulation data.

[0030] Preferably, step S2 includes the following steps:

[0031] Step S21: Establish models of the ground, EPE foam and steel ball identical to the experiment;

[0032] Step S22: Define the material properties. The ground and the steel ball are made of structural steel, and the ground is a rigid body. The EPE material is defined by the stress-strain curve obtained from the compression test;

[0033] Step S23: Perform grid division, and the grid division adopts the system default division;

[0034] Step S24: Perform contact setting, set binding contact between the ground and one side of the EPE foam, and there is frictionless contact between the rigid ball and the EPE foam.

[0035] Preferably, the step S2 further comprises the following steps:

[0036] Step S25: Analysis setting, the impact velocity of the steel ball when it just touches the EPE, according to the free fall formula It is obtained that g is the acceleration of the earth, h is the drop height, and the minimum setting time needs to ensure that the steel ball has enough rebound time after hitting the EPE foam;

[0037] Step S26: After the steel ball hits the EPE foam, a falling animation will be generated, and stress and strain information of all components will be generated. The maximum deformation point is found through the data generated by the LS-prepost software, and the maximum circular diameter of the EPE foam in contact with the steel ball after being hit by the steel ball at the moment of maximum deformation is measured using a tool.

[0038] Preferably, in step S3, the stress-strain curve of the EPE elastic stage is changed, and the stress-strain curve of the plastic stage remains unchanged. When the slope of the stress-strain curve of the elastic stage is increased or decreased, if the simulation result deviates more from the experimental result, it means that the situation does not meet the requirements. If the simulation result is closer to the experimental result, the result of this situation is retained.

[0039] Preferably, in step S3, the EPE plastic stage stress-strain curve is changed, and the elastic stage stress-strain curve remains unchanged. When the slope of the plastic stage stress-strain curve is increased or decreased, if the simulation results deviate more from the experimental results, it means that the situation does not meet the requirements. If the simulation results are closer to the experimental results, the results of this situation are retained.

[0040] Preferably, in step S3, when the slope of the stress-strain curve in the elastic stage is increased to meet the requirement, the stress-strain curve in the plastic stage is increased or decreased to observe whether it is closer to the experimental result.

[0041] The present invention relates to a method for benchmarking EPE foam finite element simulation and experimental data, which uses a small steel ball with fixed mass and fixed diameter and stained with ink to obtain the EPE deformation in an actual falling manner, and then simulates this working condition through finite element simulation to obtain a virtual value to benchmark the two. Specifically, the simulation and experimental benchmarking of EPE materials with different densities will be carried out to form an EPE material library with different density materials, which will lay the foundation for direct use of finite element simulation in the future, reduce time cost, and improve simulation efficiency and accuracy.

[0042] The present invention is described below with reference to a specific embodiment.

[0043] I. Experimental operations:

[0044] (1) Take an EPE experimental sample with appropriate thickness, length, and width. The density of EPE is 25 Kg / m 3 ; Fix one side of the EPE to the experimental tabletop with glue, and use the other side as a buffer when the small steel ball drops.

[0045] (2) Take a solid small steel ball with a fixed mass and diameter. The small steel ball is covered with erasable ink and undergoes vertical free fall at a drop height of, for example, 760 mm.

[0046] (3) Since the small steel ball is covered with ink, after dropping, it will leave an ink mark on the EPE, and the mark is circular. At this time, record the maximum diameter of the circular ink mark, that is, the distance d in Figure 3 , which is the feedback value of the elastic or plastic deformation of the EPE after being impacted.

[0047] II. Simulation operations:

[0048] (1) Establish models of the ground, EPE, and small steel ball that are the same as those in the experiment.

[0049] (2) Define material properties. The ground and the small steel ball are made of structural steel, and the ground is a rigid body. The EPE material is defined by the stress-strain curve obtained through a compression test.

[0050] (3) Conduct mesh generation. Since the model is relatively simple and regular, the system default mesh generation can be used.

[0051] (4) Conduct contact settings. Set a bonded contact on one side of the ground and the EPE, and set a frictionless contact between the small steel ball and the EPE.

[0052] (5) Conduct analysis settings. The velocity when the small steel ball impacts the EPE is obtained from the drop height and can be substituted directly. The analysis settings mainly include two parts: The first part is the impact velocity when the small steel ball just contacts the EPE, which is obtained from the free fall formula , where g is the acceleration due to gravity of the earth, 9.8 m / s 2 , and h is the drop height. The second part is the solution time, which is an indefinite value, but the minimum set time needs to ensure that there is enough rebound time after the small steel ball impacts the EPE. Generally, 0.05 s is sufficient. Setting the time too long will significantly increase the operation time and reduce efficiency, while setting the time too short will result in insufficient rebound time and inaccurate results.

[0053] (6) After the solution, the entire drop animation of the small steel ball hitting the EPE and the deformation amount of the EPE deformation can be obtained. After the small ball hits the EPE, a drop animation will be generated, and information such as stress and strain of all components will also be generated. The maximum deformation point can be found through the data generated by the LS - prepost software. Using the Measure tool in Elementtools, the maximum circular diameter in contact with the small steel ball after the EPE is hit by the small steel ball at the maximum deformation moment can be measured, that is, the distance D in Figure 5 the attachment.

[0054] III. Result comparison:

[0055] (1) After obtaining the experimental data and simulation data, compare the two, that is, the maximum diameter of the ink trace remaining on the EPE obtained experimentally and the maximum circular diameter in contact with the small steel ball after the EPE is hit by the small steel ball obtained by simulation. Since the simulation result serves the real result, the experimental data is used as the standard, and the simulation data is changed to approach the experimental real data;

[0056] (2) The deformation process of the EPE mainly includes elastic deformation and plastic deformation. Without knowing the result, the control variable method needs to be used to change the stress - strain curve of the EPE so that the simulation result gradually approaches the real result.

[0057] Change the stress - strain curve in the elastic stage of the EPE, and the stress - strain curve in the plastic stage remains unchanged. When increasing or decreasing the slope of the stress - strain curve in the elastic stage, if the simulation result deviates more from the experimental result, it means that this situation does not meet the requirements. Whether it meets the requirements is judged by comparing the maximum circular diameter of the simulation with the diameter obtained experimentally. If the simulation result is closer to the experimental result, the result of this situation is retained; change the stress - strain curve in the plastic stage of the EPE, and the stress - strain curve in the elastic stage remains unchanged. When increasing or decreasing the slope of the stress - strain curve in the plastic stage, if the simulation result deviates more from the experimental result, it means that this situation does not meet the requirements. If the simulation result is closer to the experimental result, the result of this situation is retained; there may be multiple situations that meet the requirements in the previous cases, making the simulation result gradually approach the experimental result. Therefore, an additional layer of judgment is needed to screen out the unique result: for example, when increasing the slope of the stress - strain curve in the elastic stage meets the requirements, then increase or decrease the stress - strain curve in the plastic stage to see if it meets the requirements. Other situations are the same as this situation. Determine the unique direction by changing both the elastic stage and the plastic stage simultaneously. Gradually make the simulation result approach the real result by changing the stress - strain curve. Due to the possibility of errors, an error within 5% between the simulation result and the experimental result is allowed.

[0058] The above method determines that the density is 25 Kg / m 3After obtaining the EPE simulation stress-strain curve, the EPE simulation stress-strain curves of other common densities can be obtained by the same method to form an EPE simulation material parameter library. This is convenient for directly using the data in subsequent simulations, reducing the time cost, and improving the simulation efficiency and accuracy.

[0059] Combining the simulation results with the experimental results increases the reliability of the data and avoids unnecessary cost increases; obtaining the EPE true deformation feedback value through the ink adhesion effect and then comparing it with the simulation results, the method is feasible and has a high reliability. The direction of modifying the material stress-strain curve parameters is confirmed by the control variable method, and this method can be extended to the determination of other material stress-strain curve parameters. Through this invention, the simulation of EPE material parameters with different densities can be benchmarked against the experimental results, thereby forming a proprietary material parameter library for subsequent direct calls, which greatly improves the efficiency.

[0060] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for benchmarking EPE foam finite element simulation and experimental data, characterized in that: The method comprises the following steps: Step S1: Take a piece of EPE foam test sample, fix one side of the EPE foam on the experimental table, take a solid steel ball with a fixed mass and a fixed diameter, cover the surface of the steel ball with erasable ink, perform vertical free fall at a certain height and record the drop height. After the steel ball falls, it will leave a circular ink mark on the EPE foam, and record the maximum diameter of the circular ink mark; Step S2: Establish the same ground, EPE foam and steel ball models as those in the experiment in the finite element simulation, simulate at the same drop height, obtain the entire drop animation of the steel ball hitting the EPE foam and the deformation of the EPE foam, and record the maximum circular diameter of the EPE foam in contact with the steel ball; Step S3: Compare the maximum diameter of the ink trace obtained by the experiment with the maximum circular diameter of the contact between the EPE foam and the steel ball obtained by simulation, and take the experimental data as the standard to approach the actual experimental data by changing the simulation data.

2. The EPE foam finite element simulation and experimental data benchmarking method according to claim 1, characterized in that: Step S2 includes the following steps: Step S21: Establish the same ground, EPE foam and steel ball models as in the experiment; Step S22: define material properties, the ground and the steel ball are structural steel materials, the ground is a rigid body, and the EPE material is defined by the stress-strain curve obtained by the compression test; Step S23: Perform grid division, and the grid division adopts the system default division; Step S24: Perform contact setting, set binding contact between the ground and one side of the EPE foam, and there is frictionless contact between the rigid ball and the EPE foam.

3. The EPE foam finite element simulation and experimental data benchmarking method according to claim 2 is characterized in that: The step S2 further comprises the following steps: Step S25: Analysis setting, the impact velocity of the steel ball when it just touches the EPE, according to the free fall formula It is obtained that g is the acceleration of the earth, h is the drop height, and the minimum setting time needs to ensure that the steel ball has enough rebound time after hitting the EPE foam; Step S26: After the steel ball hits the EPE foam, a falling animation will be generated, and the stress and strain information of all components will be generated. The maximum deformation point is found through the data generated by the LS-prepost software, and the maximum circular diameter of the EPE foam in contact with the steel ball after being hit by the steel ball at the moment of maximum deformation is measured using a tool.

4. The EPE foam finite element simulation and experimental data benchmarking method according to claim 1, characterized in that: In step S3, the stress-strain curve of the EPE elastic stage is changed, and the stress-strain curve of the plastic stage remains unchanged. When the slope of the stress-strain curve of the elastic stage is increased or decreased, if the simulation result deviates more from the experimental result, it means that the situation does not meet the requirements. If the simulation result is closer to the experimental result, the result of this situation is retained.

5. The EPE foam finite element simulation and experimental data benchmarking method according to claim 1, characterized in that: In step S3, the stress-strain curve of the EPE plastic stage is changed, and the stress-strain curve of the elastic stage remains unchanged. When the slope of the stress-strain curve of the plastic stage is increased or decreased, if the simulation result deviates more from the experimental result, it means that the situation does not meet the requirements. If the simulation result is closer to the experimental result, the result of this situation is retained.

6. The EPE foam finite element simulation and experimental data benchmarking method according to claim 1, characterized in that: In step S3, when the slope of the stress-strain curve in the elastic stage is increased to meet the requirements, the stress-strain curve in the plastic stage is increased or decreased to observe whether it is closer to the experimental result.

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