JP3090757B2 - Method for analyzing three-dimensional structure of synthetic resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a finite element method using, for example, a honeycomb structure model as a structure model.
Regarding a three-dimensional structural analysis method for analyzing mechanical properties such as strain,
In particular, the present invention relates to a method for analyzing the three-dimensional structure of a synthetic resin foam capable of accurately analyzing mechanical properties of the synthetic resin foam during impact deformation.

[0002]

BACKGROUND OF THE INVENTION FIG. 19 shows the structural concept of a honeycomb structure model as described above. The honeycomb model 3 _e as the honeycomb structure model shown in the same figure has different mechanical characteristics in two directions (y-axis and z-axis directions) and a core direction (x-axis direction) of a hexagonal cylinder opening cross section. This is a so-called anisotropic structure model. Such a honeycomb model 3
_e is used when analyzing the behavior of the mechanical properties of a honeycomb structure by the finite element method, and a structure for the honeycomb structure is currently being developed. Honeycomb model _3e above
Is used in the processing in the middle of the calculation program of the finite element method. According to the finite element method, a target structure is divided into, for example, a plurality of three-dimensional finite elements, and the three-dimensional normal stress is applied to these finite elements by a predetermined calculation procedure of the finite element method. After calculating the strain (vertical and shear) at the integration point in each of the above finite elements as the calculation position for calculating the shear stress, the strain of each of the above finite elements is used to calculate the material model representing the honeycomb model 3 _e . For example, it is applied to a subroutine program. FIG. 20 shows an example of a subroutine program of the honeycomb model _3e .
Is shown in the flowchart of FIG. According to this, first, each volume strain ε _v is calculated from the strain for each direction component (S40). Since the honeycomb model 3 _e is anisotropic as described above, the coordinates are transformed from the global coordinate system to the local coordinate system (S 41). Then, as shown in FIG. 21, an initial elastic modulus E ₀ corresponding to the above-mentioned volume strain ε _v , which is preset for each direction component of each of the above-mentioned axes (x, y, z).
And the maximum modulus of elasticity E _max (E _0, none of the E _{ma x,} vertical and shear), for example are read from each memory (S50 _b). Here, when the honeycomb model 3 _e is compressed from the outside, the elasticity at that time is calculated by a proportional calculation between the initial elastic modulus E ₀ and the maximum elastic modulus E _max according to the logarithmic value of the volume strain ε _v . factor E (DF) is calculated (S60 _b). The initial elastic modulus E ₀ is set so that the stress σ obtained from the volume strain ε _v (logarithm) at that time always exceeds a maximum stress curve (FIG. 22) described later. The stress σ used is the value of the stress on the maximum stress curve. The elastic modulus E (DF) obtained in this way is used for calculating the stress at the time of unloading. Then, in the honeycomb model _3e , each of the directional components is set until the gap of the honeycomb is crushed by the compression (hereinafter, this state is referred to as consolidation), as shown in FIG. 22. The stress is calculated based on the maximum stress curve showing the relationship between the stress σ (perpendicular stress and shear stress in three directions) and the volumetric strain ε _v (logarithmic). The feature is that stress calculation is performed using the maximum elastic modulus E _max (S70 _b ). In this case, as the maximum stress curve, as shown in FIGS. 23 and 24 (enlarged scale of the stress scale in FIG. 23), the vertical stresses σ _yy , σ
_The same curve is used for _zz, and a linear curve having only a vertical stress σ _xx in the x-axis direction, which is the above-described cylinder core direction, different from the others is used. Thus, the anisotropic mechanical characteristics of the honeycomb model _3e are taken into account. Then, in the above subroutine, after the coordinate system is re-transformed from the above local coordinate system to the whole coordinate system (S71), the processing procedure is returned to the main routine of the above finite element method, and each direction component calculated in the subroutine is obtained. The stress σ is provided to the arithmetic processing after the main routine.

[0003]

The honeycomb model _3e and the synthetic resin foam are similar in structure.
In addition, since the honeycomb model _3e can also analyze the mechanical properties after compaction, it is possible to analyze the behavior of the foam itself after compaction, which occurs when the synthetic resin foam undergoes impact deformation due to collision with an object. Then, the present inventors examined whether or not the above honeycomb model 3 _e can be suitably applied as a model of a synthetic resin foam. However, the synthetic resin foam is so-called isotropic, in which the mechanical properties hardly change in each of the three-dimensional directions, whereas the honeycomb model 3 _e has the anisotropic mechanical properties as described above. I have. Therefore, the above honeycomb model 3 _e
The mechanical properties obtained by the finite element method using the synthetic resin foam material data differed from the actual behavior of the synthetic resin foam. Use for example, when compressing the prismatic synthetic resin foam downwards, the shape of the compressed synthetic resin foam is actually no irregularities on the side surfaces parallel to the compression direction, the honeycomb model 3 _e According to the calculation result, irregularities may occur on the side surface. On the other hand, in the finite element method, in practice, many nodes are set for the above structure in order to analyze the fine behavior of the shape of the structure to be calculated, and for each of these nodes, Various types of data are set. Therefore, even if a computer capable of performing calculations at high speed is used, even if a computer capable of performing calculations at high speed is used, an extremely long calculation time is required, and a reduction in the calculation time is demanded. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is based on a finite element method using a honeycomb structure model, and actually considers the mechanical characteristics of a synthetic resin foam during impact deformation. It is an object of the present invention to provide a method for analyzing a three-dimensional structure of a synthetic resin foam that can be analyzed with high accuracy.

[0004]

Means for Solving the Problems In order to achieve the above object, a first means employed by the present invention is to convert a synthetic resin foam which is shock-deformed by collision with an object into a plurality of three-dimensionally divided foams. And calculates the distortion of each finite element deformed by the collision for each three-dimensional directional component, applies the calculated distortion of each finite element to a honeycomb structure model, The stress in each direction component of each finite element is obtained from the calculated strain based on the relationship between the strain and the stress in each three-dimensional direction component set in advance in the structure model. In the three-dimensional structure analysis method for a synthetic resin foam, which analyzes the mechanical properties of the synthetic resin foam during deformation, the relationship between the strain and the stress for each of the three-dimensional directional components is the same for all the directional components. The relationship between the points And it is configured as a three-dimensional structural analysis method of the resin foam. The relationship between the strain and the stress for each of the three-dimensional components in the first means is changed to the same relationship for each of the three-dimensional components. The configuration may be such that the stress for each component is obtained directly from the calculated strain of each finite element based on the relationship between the strain and the stress for each direction component. However, “directly obtain” means, for example, a configuration in which the above-described stress is obtained without performing coordinate conversion between the global coordinate system and the local coordinate system. The second means adopted to achieve the above-mentioned object is to summarize a synthetic resin foam which is shock-deformed by collision with an object by using a three-dimensional finite element divided into a plurality of parts. And calculates the distortion of each finite element deformed by the collision for each three-dimensional directional component, applies the calculated distortion of each finite element to the honeycomb structure model, and applies the calculated distortion to the honeycomb structure model. The synthetic resin foam is obtained by obtaining a stress for each direction component of each finite element from the calculated strain based on a preset relationship between the strain and stress for each three-dimensional direction component. In the three-dimensional structural analysis method of a synthetic resin foam for analyzing the mechanical properties of the synthetic resin foam during deformation, the relationship between the strain and stress at the time of impact deformation for each of the three-dimensional components is determined by statically determining the synthetic resin foam. Strain obtained by transforming And it is configured as a three-dimensional structural analysis method of the synthetic resin foam according to the point calculated by multiplying the multiplying factor which is set in advance corresponding to the measured value when the impact deformation strain or stress in relation to the stress. The third means adopted to achieve the above object is that the gist of the invention is that a synthetic resin foam which is shock-deformed by collision with an object is divided into a plurality of three-dimensional finite element elements. Calculating the distortion of each finite element deformed by the collision for each three-dimensional directional component, applying the calculated distortion of each finite element to the honeycomb structure model, Calculating the stress in each direction component of each finite element from the calculated strain based on the relationship between the strain and stress in each three-dimensional direction component set in advance in the synthetic resin foaming process. In the three-dimensional structural analysis method for a synthetic resin foam for analyzing the mechanical properties of the synthetic resin foam during deformation, the relationship between the strain and the stress at the time of impact deformation for each of the three-dimensional directional components is determined by statically determining the synthetic resin foam. And deformation determined by dynamic deformation Is obtained by multiplying the strain or stress in the relationship with the multiplication factor set in advance corresponding to the actually measured value at the time of the shock deformation, and the relationship between the strain and the stress at the time of the shock deformation is the same for each of the directional components. In addition to the relationship, the stress of each finite element in each of the three-dimensional directions is calculated directly from the calculated strain of each finite element based on the relationship between the strain and the stress in each direction. The synthetic resin foam is configured as a three-dimensional structure analysis method. In each of the above-described configurations, the relationship between the strain and the stress in each of the three-dimensional directional components is determined based on data for each expansion ratio and / or each type of synthetic resin set in several steps of the synthetic resin foam. A configuration related to a point stored in advance as a table may be adopted.

[0005]

According to the first means of the present invention, the relationship between strain and stress for each direction component, which is the same for all three-dimensional direction components, is preset in the honeycomb structure model. Therefore, the above honeycomb structure model can be treated as a structure exhibiting isotropic mechanical characteristics. Therefore, it is possible to accurately analyze the mechanical properties of the synthetic resin foam exhibiting the isotropic mechanical properties at the time of impact deformation, in actuality. In the first means, in the case where the stress of each finite element in each of the three-dimensional directions is directly obtained from the calculated strain of each finite element without performing the coordinate transformation, In addition to the effects of the first means, it is possible to reduce the operation time required for the analysis operation. Further, according to the second means, it is possible to obtain a multiplication factor corresponding to an actually measured value at the time of actual impact deformation by an easy experimental method such as statically deforming the synthetic resin foam. Then, the relationship between the strain and stress at the time of impact deformation in each of the three-dimensional components is obtained by multiplying the relationship obtained by statically deforming by the above multiplication factor. The relationship between the strain and the stress for obtaining the above can be easily set. In addition, according to the third means, since the configuration includes all the essential parts of the first and second means, all the functions of the first and second means can be achieved. . Further, in the first to third means, it is possible to use data which is actually based on the expansion ratio and / or the type of the synthetic resin of the actual synthetic resin foam. The mechanical properties at the time of deformation can be analyzed in accordance with actual conditions.

[0006]

Embodiments of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments are merely examples embodying the present invention, and do not limit the technical scope of the present invention. Here, FIG. 1 is a block diagram showing a three-dimensional structural analysis apparatus according to one embodiment of the method of the present invention, and FIG. 2 is an energy shock absorbing material (hereinafter, referred to as a core material) of an automobile bumper used as a synthetic resin foam. FIG. 3 is a configuration diagram showing a weight drop test device for actually measuring mechanical properties of the core material, and FIG. 3 is a maximum stress curve set in a honeycomb model applied to the core material used in the calculation by the three-dimensional structure analysis device. FIG. 4 is a graph showing a maximum stress curve of vertical stress for each direction component and a maximum stress curve of shear stress in the maximum stress curve of the honeycomb model, and FIG. A graph showing a maximum stress curve of a metal isotropic elastoplastic model set for the reinforcing material of the bumper,
FIG. 6 is a flowchart showing a main routine of a general finite element method calculated by the three-dimensional structure analysis apparatus,
FIG. 7 is a flowchart showing a subroutine for the material model, and FIG. 8 is an element model of the bumper for an automobile and an element of a drop weight which are divided into elements for an impact test simulating a barrier test by the weight drop test apparatus. FIG. 9 is an explanatory diagram showing a model, FIG. 9 is an explanatory diagram showing each displacement state at the time of collision between the falling weight and the bumper analyzed by the element model of FIG. 8, and FIG. 10 is a calculation result and a measured value simulating a barrier test. Graph showing changes with time in displacement due to
FIG. 11 is a graph showing the change over time of the reaction force obtained by the impact test, FIG. 12 is a flowchart showing a honeycomb model subroutine as an example of the material model shown in FIG. 7, and FIG. Fig. 14 is an element division view of the pendulum and the vehicle body in an external view of the state of the element division simulating the endurance test using Fig. 14. FIG. 15 is a graph showing the change over time in the strain energy and kinetic energy of each member by the above-mentioned bending test, and FIG. 16 is a block-like synthetic resin foam using the above three-dimensional structural analyzer. FIG. 17 is an explanatory view showing a state of displacement at the time of deformation when the body is compressed. FIG. 17 is a graph showing a change with time of the displacement of the block-shaped synthetic resin foam by an impact test. FIG. 18 is a graph showing the time course of the reaction force obtained by the impact test of the block-shaped synthetic resin foam. However, the same symbols and terms are used for elements and terms common to the honeycomb model 3 _{e as} the background shown in FIGS. 19 to 24 and the graphs and flowcharts applied thereto, and detailed description thereof is given. Is omitted. Elements having the same function are denoted by the same reference numerals with different subscripts.

[0007] Three-dimensional structure analysis apparatus 1 according to the method of this embodiment
Is configured as, for example, a large-sized general-purpose computer capable of performing arithmetic operations according to the finite element method at high speed, and as shown in FIG. An input unit 5 for inputting node data for dividing into a plurality of finite elements, initial data of mechanical characteristics, material property data, and the like, and outputs an analysis result of mechanical characteristics by the finite element method calculated by the arithmetic unit 2 Output unit 6 composed of, for example, a CRT or a printer
When, the program memory 3. storing the material model program as a main routine and utilities program or subroutine programs according to the finite element method, and the mechanical properties relationship data memory 4 _a for storing the mechanical properties relationship data, such as maximum stress curve a data memory 4 more as a work memory 4 _b to rewrite updatable storing various data calculated for each of the nodes are primarily provided it with. A plurality of model programs corresponding to various materials are stored in the material model program of the program memory 3. In this embodiment, the metal isotropic elastoplastic model program 3 _a and the honeycomb model 3 are used.
Metal honeycomb structure model program 3 _b that expresses _e
Is used. In this embodiment, in particular for analyzing the dynamic characteristics at the time of impact deformation of the synthetic resin foam using the above metal honeycomb structure model program 3 _b, during execution of the material model subroutine in the finite element method, shown in FIG. 4 Thus, the same maximum stress curve (solid line) for the vertical stresses σ _xx , σ _yy , σ _zz for each direction component representing the relationship between strain and stress for each direction component of each axis of x, y, z Curve) was used. The maximum stress curve in the relationship between the shear stress σ _g and the volume strain ε _v at this time is indicated by a broken line curve.

As shown in FIG. 3, the maximum stress curves of the vertical stresses σ _xx , σ _yy , σ _zz and shear stress σ _g are shown for each expansion ratio of the synthetic resin foam and each type of the synthetic resin. The maximum stress curves (shown by broken lines in the figure) obtained by statically compressing the above synthetic resin foam and the maximum stress curves obtained by compressing it by impact (shown by dashed-dotted lines in the figure) The average power of each of the stresses σ _{xx to} σ _g or the volume strain ε _v is determined from the relationship between the static data indicated by the broken line and the dynamic data indicated by the alternate long and short dash line. Therefore, if the expansion ratio of the synthetic resin foam and the type of the synthetic resin are known, the multiplier is determined in advance as described above from the maximum stress curve relatively easily obtained by statically compressing the synthetic resin foam. By multiplying the maximum stress curve, the maximum stress curve at the time of impact compression as shown by the solid line in the figure can be easily calculated, and the maximum stress curve as the calculated value can be used when the material model subroutine is executed. Incidentally, the multiplication factor in the figure is about 1.5. The calculated respective maximum stress curve was is previously stored in the mechanical properties relationship data memory 4 _a of the data memory 4 as a data table for each type of the set expansion ratio and for each synthetic resin several steps. Accordingly, even when the expansion ratio of the synthetic resin foam or the type of the synthetic resin is different, data that is more practicable can be used when analyzing the mechanical properties of the synthetic resin foam during impact deformation. As the data table stored in the mechanical properties relationship data memory 4 _a, stores the multiplying factor corresponding to this and the maximum stress curve obtained by the static compression, these during execution of the subroutine Each of the maximum stress curves at the time of the impact compression may be obtained.

Subsequently, an example in which the above-mentioned synthetic resin foam is applied to a core material of a bumper for an automobile will be described below. FIG. 2 shows a weight drop test apparatus for demonstrating the mechanical characteristics of the bumper when the object collides with the automobile bumper upon impact deformation. In the figure, a bumper 10 is made of a core material 11 made of a synthetic resin foam on the front end side of a vehicle, a reinforcing material 12 made of high-strength steel, and a carbon steel connecting the vehicle body (not shown) and the reinforcing material 12. And the reinforcing material supporting portion 13. In the weight drop test device, an acceleration sensor for measuring the drop acceleration of the drop weight 14 that falls along the column toward the front end of the core material 11 is provided.
The reaction force of the bumper 10 is calculated from the acceleration detected by the acceleration sensor. Further, an optical pulse length measuring device for measuring the displacement of the falling weight 14 in the height direction (the distance indicated by A in the figure) is provided.
As soon as the falling weight 14 collides with the upper surface of the
Based on this, the upper surface displacement of the core material 11, that is, the amount of deformation of the bumper 10 to absorb the collision energy of the falling weight 14 can be known. And the reinforcing material 12
A reflection-type laser displacement meter for measuring the displacement amount of the lower surface of the device in real time is installed on a base just below the reinforcing member 12.
The signals output from the above-described sensors are stored in the transient recorder by a timing signal from a photoelectric switch provided at a position immediately before the falling weight 14 collides with the bumper 10. The timing of data input from each sensor is based on a clock signal from an external clock. A data signal stored in the transient recorder from each sensor is input to a computer via an A / D converter and an IC memory card as a buffer memory, and output data is graphed by the computer and a memory connected thereto. Or be memorized.
In the weight drop test apparatus, the height of the drop start is set in advance so that the drop speed of the drop 14 to the bumper 10 is set to a predetermined value corresponding to the wall collision (barrier) test. Also, the weight of the falling weight is set in advance corresponding to the weight of the vehicle.

The three-dimensional structural analysis apparatus 1 of the present embodiment uses the finite element method to determine the mechanical characteristics of the bumper 10 in the above-mentioned weight drop test apparatus at the time of impact deformation of the bumper 10 when the falling weight 14 collides with the bumper 10. This is a simulation analysis. In this case, as the material model program used in the material model subroutine of the calculation program of the finite element method, the metal isotropic elasto-plastic body model program _3a is used for the reinforcing member 12 and the reinforcing member support portion 13, and For the core material 11, a metal honeycomb structure model program _3b is used. Note that the metal isotropic elasto-plastic body model 3 _a, is the maximum stress curve using showing the stress-strain relationship as shown in FIG. 5, mechanical characteristics relationship data memory of the maximum stress curves the data memory 4 previously stored in 4 _a. FIG. 6 shows a general flowchart of a main program according to the finite element method for analyzing the mechanical characteristics of the bumper 10 at the time of impact deformation by the three-dimensional structure analysis apparatus 1. In the finite element method used in this embodiment, a so-called explicit method is used as the time integration method.
As a stress calculation method, a so-called updated Lagrange method is used. In the flow chart shown in the figure, after the finite element method program and required data are initialized, for example, the number of nodes for determining a three-dimensional element (finite element), the coordinates of the nodes, and the load on each element Data such as a vector is input. In this embodiment, the integration point that is the stress calculation point for each element is only one solid center point of each element. By the data input, the number of configured node P _i (i) and the bumper model 10 _e are represented by the coordinates
8 is shown in FIG. In FIG.
_e , reinforcement model _12e and reinforcement support model _13e
Is composed of a plurality of divided elements E _N (N is the total number of elements of the entire bumper model 10 _e ), and the falling weight model 14 _e is composed of a single element.

In this embodiment, a characteristic method is used particularly in the material model subroutine in the step indicated by S12 in the main routine of FIG. FIG. 7 shows a flowchart of the material model subroutine. Differs from the material model subroutine conventional material model subroutine (FIG. 20), the first, in step S70, x for the core material model 11 _e, y, normal stress for each direction component of z axes sigma _xx , Σ _yy , σ _zz are calculated based on the corresponding volume strains ε _v , as shown by the solid line in FIG. That is, the same maximum stress curve obtained by the static compression stored in advance in _a was used. Accordingly, mechanical properties of the honeycomb model 3 _e represented by the metal honeycomb structure model program 3 _b is x, y, all of the same properties for z each axially, i.e. treated as mechanical properties of isotropic. Thereby, the behavior according to the actual behavior of the core material 11 made of the synthetic resin foam having the originally isotropic mechanical characteristics can be expressed.
The maximum stress curve for the shear stress σ _g is indicated by a broken line. In addition, in order to make the behavior of the core material model 11 _e actually comply with the unloading, also in step S50, the same elastic modulus (including the shear elastic modulus) / strain relation data (including the shear elastic modulus) for each direction component. E shown in FIG.
₀ and E _max ) are used. Secondly, since the mechanical characteristics of the honeycomb model _3e are made isotropic, a step of performing coordinate conversion between the global coordinate system and the local coordinate system as in a conventional synthetic resin foam subroutine (FIG. 20). S41 and S71) are not required. By omitting these steps, the time required for analyzing the mechanical characteristics of the bumper 10 at the time of impact deformation could be shortened. That is, each of the above vertical stress and shear stress σ _{xx to} σ
_g is from volumetric strain epsilon _v computed in the step S40 on the basis of the maximum stress curve stored in the mechanical properties relationship data memory 4 _a, in the same coordinate system without coordinate transformation, is determined directly. In this subroutine, a multiplication factor corresponding to the type of synthetic resin and the expansion ratio is read for each stress obtained based on the maximum stress curve obtained by the static compression (S80). is multiplied by the multiplying factor to the calculated stress is corrected (S90) and so, but obtained by multiplying the maximum stress curve and the multiplying factors determined in advance by the static compression on the mechanical properties relationship data memory 4 _a The corrected maximum stress curve as a result of the impact compression is stored in advance, and the corrected maximum stress curve is directly used in step S70, whereby the processing in steps S80 and S90 can be shortened. .

[0012] Continuing returns to the main routine of FIG. 6 shows a displacement diagram of the bumper model 10 _e upon impact deformation obtained after a predetermined calculation step on the basis of the calculation program of the finite element method in FIG. In the figure, the bumper model 10 _e ′ at the time of impact deformation hardly changes from the actually observed displacement state, and in particular, the displacement state of the core material model 11 _e ′, which is a synthetic resin foam model, substantially follows the displacement state. Was something. The displacement state of the bumper model 10 _e ′ shown in FIG. 9 is obtained by inputting data corresponding to the barrier test as input data. The impact deformation of the core material model 11 _{e under} the conditions simulating the barrier test is performed. The change over time of the displacement and the change over time of the reaction force are shown in FIGS. 10 and 11, respectively. As is clear from these graphs, it can be seen that the calculation result by the method of the present embodiment is close to the actually measured value. Note that the three-dimensional structure analysis apparatus 1 can also analyze the mechanical characteristics of the bumper upon impact deformation imitating an actual pendulum test by receiving input data corresponding to the pendulum test. As an example, FIG. 13 shows an example of an element division diagram, and FIG. 14 shows a displacement diagram when a pendulum collides with a bumper. FIG. 15 shows an example of the change over time in the kinetic energy of the pendulum and the strain energy in each member of the pendulum and the bumper at that time. On the other hand, a columnar (block-shaped) synthetic resin foam
FIG. 16 shows the result of calculation using the apparatus of this embodiment when the data is compressed downward to slightly less than 0%. Results synthetic resin foam model 20 _e of original indicated by the two-dot chain line in the figure which is an impact compressed, synthetic resin foam model 20 shown by a solid line
Displace to _e '. Even when the actual synthetic resin foam is compressed in this way, for example, the surface formed by the y-axis and the z-axis or the surface formed by the z-axis and the x-axis has almost no irregularities, as shown in FIG. It has the characteristic that it is compressed and deformed only in the direction, and it has been proved that the analysis result by the apparatus of the present embodiment is very realistic. In this case, when the calculation is performed by treating the honeycomb model 3 _e as anisotropic as in the related art, a result occurs in which, for example, a plane formed by the y-axis and the z-axis indicated by V pops out or is depressed. FIGS. 17 and 18 show the change over time of the displacement and the change over time of the reaction force obtained by inputting data corresponding to the actual conditions of compressing the block-shaped synthetic resin foam into the apparatus of this embodiment. Show. As is clear from these graphs, the results of the dynamic operation performed by the apparatus of the present embodiment are close to the measured values, and have a certain relationship with the static data C. . In the above embodiment, the material model subroutine was executed without performing the coordinate transformation between the global coordinate system and the local coordinate system. However, the above honeycomb model 3 _e is treated as a model having isotropic mechanical characteristics. In the case where an analysis based on an actual rule is to be performed, coordinate conversion may be performed as in the related art. FIG. 12 shows a subroutine of the synthetic resin foam model (honeycomb model) in that case. However, also in this case, in the local coordinate system converted in the same manner as in the previous embodiment, the data of the same stress-strain relationship for each direction component (maximum stress curve shown in FIG. 4) is used for each volume strain ε _v . it may be obtained each of the corresponding stress (S70 _a). Further, the elastic modulus / strain relationship data (E ₀ , E _{max in} FIG. 21) read to calculate the elastic modulus (S60 _a ) used at the time of unloading.
For even it may be used similarly obtained values for each direction component (S50 _a). As described above, according to the method of each embodiment, the mechanical characteristic behavior of the synthetic resin foam at the time of impact deformation can be accurately obtained in accordance with the actual condition. For example, the present invention can be sufficiently used for designing a protective material for packing made of synthetic resin foam, a shock energy absorbing material such as protective equipment for sports competitions, and the like.

[0013]

The present invention is configured as described above. Thus, the honeycomb structure model can be applied to the finite element method as a structure model having isotropic mechanical characteristics. As a result, the mechanical characteristics of the synthetic resin foam at the time of impact deformation can be accurately analyzed by the finite element method using the above-mentioned honeycomb structure model in accordance with the actual condition. In addition to this, the coordinate transformation between the global coordinate system and the local coordinate system is performed as compared with the case where the honeycomb structure model is treated as a structure model having anisotropic mechanical characteristics. Since there is no need, the calculation time can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a three-dimensional structure analyzing apparatus according to an embodiment of the method of the present invention.

FIG. 2 is a configuration diagram showing a weight drop test apparatus for actually measuring mechanical properties of an energy shock absorbing material (core material) of an automobile bumper used as a synthetic resin foam.

FIG. 3 is an explanatory diagram for explaining a method for obtaining a maximum stress curve used in a calculation by the three-dimensional structure analysis apparatus and set in a honeycomb model applied to the core material.

FIG. 4 is a graph showing a maximum stress curve of a vertical stress in each direction component and a maximum stress curve of a shear stress among the maximum stress curves of the honeycomb model.

FIG. 5 is a graph showing a maximum stress curve of a metal isotropic elastoplastic model set for a reinforcing material of the bumper.

FIG. 6 is a flowchart showing a main routine of a general finite element method calculated by the three-dimensional structure analysis apparatus.

FIG. 7 is a flowchart showing a subroutine for the material model.

FIG. 8 is an explanatory view showing an element model of the vehicle bumper and an element model of a falling weight, which are divided into elements for an impact test simulating a barrier test by the weight drop test apparatus.

FIG. 9 is an explanatory view showing respective displacement states at the time of collision between the falling weight and the bumper analyzed by the element model of FIG. 8;

FIG. 10 is a graph showing a calculation result simulating a barrier test and a temporal change in displacement based on an actually measured value.

FIG. 11 is a graph showing the change over time of the reaction force obtained by the impact test.

FIG. 12 is a flowchart showing a subroutine of a honeycomb model as an example of the material model shown in FIG. 7;

FIG. 13 is an element division view of the pendulum test using the above three-dimensional structure analysis apparatus, which is an external view of an element division state of a pendulum and a vehicle body.

14 is a state explanatory view showing the displacement state of each element when the bumper of the vehicle body and the impingement ridge of the pendulum of FIG. 13 collide with each other.

FIG. 15 is a graph showing temporal changes in strain energy and kinetic energy of each member according to the pendulum test.

FIG. 16 is an explanatory diagram showing a displacement state when deformed when a block-shaped synthetic resin foam is compressed using the three-dimensional structure analysis apparatus.

FIG. 17 is a graph showing time-dependent changes in displacement of the block-shaped synthetic resin foam in an impact test.

FIG. 18 is a graph showing a change over time of a reaction force obtained by an impact test of the block-shaped synthetic resin foam.

FIG. 19 is a conceptual diagram showing a structural concept of a honeycomb model as an example of the background of the present invention.

FIG. 20 is a flowchart showing a conventional subroutine based on the honeycomb model of the background.

FIG. 21 is a graph showing the relationship between volume strain and elastic modulus used in the honeycomb model of the background.

FIG. 22 is a graph showing the relationship between volume strain and stress used in the honeycomb model of the background.

FIG. 23 illustrates a 3D model used for the honeycomb model of the background.
The graph which shows the maximum stress curve about the perpendicular stress for every direction component of a dimension, and the maximum stress curve about a shear stress.

FIG. 24 is an enlarged view of the stress scale of FIG. 23.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Three-dimensional structure analysis apparatus 2 ... Operation part _3b ... Metal honeycomb structure model program _3e ... Honeycomb model _4a ... Mechanical characteristic relation data memory 5 ... Input part 10 ... Bumper 11 ... Core material 12 ... Reinforcement material 13 ... stiffener supports 14 ... falling weight 20 _e ... synthetic resin foam model P _i ... node E _N ... elements

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01N 3/00-3/62 G01B 21/32 G06F 15/31

Claims (5)

(57) [Claims] 1. A synthetic resin foam which is shock-deformed by a collision with an object is composed of a plurality of three-dimensional finite elements divided into a plurality of parts, and the distortion of each finite element deformed by the collision is reduced by 3%.
Calculate for each direction component of the dimension, apply the calculated distortion of each finite element to the honeycomb structure model, and calculate the distortion for each of the three-dimensional direction components preset in the honeycomb structure model. A three-dimensional synthetic resin foam for analyzing mechanical properties of the synthetic resin foam during deformation by obtaining a stress for each direction component of each of the finite elements from the strain calculated based on the relationship with the stress. A three-dimensional structural analysis method for a synthetic resin foam, wherein the relationship between strain and stress in each of the three-dimensional components is the same for each of the three-dimensional components. 2. The method according to claim 1, wherein a stress in each of the three-dimensional components of each of the finite elements is directly obtained from the calculated distortion of each of the finite elements based on a relationship between the strain and the stress in each of the directional components. 3. The method for analyzing a three-dimensional structure of a synthetic resin foam according to item 1. 3. A synthetic resin foam which is shock-deformed by a collision with an object is composed of a plurality of three-dimensional finite elements divided into a plurality of three-dimensional finite elements.
Calculate for each direction component of the dimension, apply the calculated distortion of each finite element to the honeycomb structure model, and calculate the distortion for each of the three-dimensional direction components preset in the honeycomb structure model. A three-dimensional synthetic resin foam for analyzing mechanical properties of the synthetic resin foam during deformation by obtaining a stress for each direction component of each of the finite elements from the strain calculated based on the relationship with the stress. In the structural analysis method, the relationship between the strain and the stress at the time of impact deformation for each of the three-dimensional components is determined by the strain or stress in the relationship between the strain and the stress obtained by statically deforming the synthetic resin foam. Multiplied by a multiplication factor set in advance corresponding to the actually measured value at the time of the impact deformation to obtain a three-dimensional structure analysis method for a synthetic resin foam. 4. A synthetic resin foam which is shock-deformed by collision with an object is composed of a plurality of three-dimensional finite elements divided into a plurality of three-dimensional finite elements.
Calculate for each direction component of the dimension, apply the calculated distortion of each finite element to the honeycomb structure model, and calculate the distortion for each of the three-dimensional direction components preset in the honeycomb structure model. A three-dimensional synthetic resin foam for analyzing mechanical properties of the synthetic resin foam during deformation by obtaining a stress for each direction component of each of the finite elements from the strain calculated based on the relationship with the stress. In the structural analysis method, the relationship between the strain and the stress at the time of impact deformation for each of the three-dimensional components is determined by the strain or stress in the relationship between the strain and the stress obtained by statically deforming the synthetic resin foam. Is multiplied by a multiplication factor set in advance corresponding to the actually measured value at the time of the impact deformation, and the relationship between the strain and the stress at the time of the impact deformation is made the same for each of the directional components. 3D finite element Stress for each component, three-dimensional structural analysis method of synthetic resin foam, characterized in that directly obtained from the distortion of each finite element is said computed based on the relationship between strain and stress of each of the one direction component. 5. The relation between strain and stress for each three-dimensional directional component is stored in advance as a data table for each expansion ratio and / or each type of synthetic resin set in several stages of the synthetic resin foam. 5. The method for analyzing a three-dimensional structure of a synthetic resin foam according to claim 1, wherein the three-dimensional structure is stored.