JP2002342694A - Method and device for structural analysis of elastic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an analyzing technique capable of precisely simulating the behavior of an elastic material when external force is applied to the elastic material being an analyzing object. SOLUTION: In order to simulate the behavior of the elastic material to the external force when the external force is applied to the elastic material, this method for structural analysis of the elastic material has a step for differentiating stress σ, which is generated at the elastic material at a prescribed time(t) when the external force is applied to the elastic material, by distortion ε; a step for obtaining a reference stress value σ0 corresponding to the static deformation of the elastic material; a step for obtaining a difference stress Δσ (t) by integrating a variable f (ε) concerning the compression rigidity of the elastic material by a prescribed time increment; and a step for obtaining a stress value σ(T) at an analyzing time T by adding a value obtained by accumulating the difference stress Δσ (t) since the time of starting loading of the external force until a prescribed analyzing time T to the reference stress value σ0 .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for analyzing the structure of an elastic material, and more particularly to a technique for accurately simulating the behavior characteristics of the elastic material when an external force is applied to the elastic material.

[0002]

2. Description of the Related Art Conventionally, when the behavior of an elastic material when an external force is applied to the elastic material is analyzed by simulation using the finite element method, the elastic material is divided into finite elements and shown in FIG. As described above, an equivalent circuit composed of an external force acting, a spring element (compression stiffness element), and a damping element is configured as a dynamic model for each finite element, and a so-called Foigt model shown in FIG. Analysis work. In this model, a stress σ (t) generated in an elastic material is calculated by using a spring constant K for a spring element and a constant C for a damping coefficient. By the way, regarding the handling of the spring element Kε (t) in the above equation of motion, in the conventional analysis technique, as shown in FIG. 19, a region corresponding to a static load acting on the elastic material (“static in FIG. From the ratio of stress and strain at the boundary value of the area shown as “deflection amount”, the spring constant K is approximated as a linear function.
There has been known a method of simply setting and applying this to the above equation of motion for operation. However, the relationship between stress and strain in the elastic material actually changes nonlinearly as shown in FIG. 19, and furthermore, the load and unloading repeatedly act on the elastic material. When it is necessary to consider the dynamic stiffness in the above, the fluctuation range of “stress-strain” differs greatly from the static deflection area, so the analysis using the dynamic stiffness There is a problem that it cannot be performed well. As shown in FIG. 19, the fluctuation of the “stress-strain” of the elastic material is largely different between the static bending region and the other regions, and the difference directly affects the compression rigidity error of the elastic material. Results. In particular, when vibration acts on the elastic material, a large error occurs between the simulation value and the experimental value (actually measured value) as shown in FIG. There is a problem that the resonance characteristics of the material cannot be correctly analyzed.

On the other hand, regarding the handling of the spring element Kε (t), as shown in FIG. 21, a dynamic rigid region in the elastic material (a region shown on the right side of “static deflection” in FIG. 19). There is also known an analysis method in which the spring constant K is approximately and simply set as a linear function from the ratio of stress and strain in the above, and is applied to the above equation of motion for operation. According to this method, when vibration in which load and unloading are repeatedly input acts on the elastic material, it is possible to relatively accurately simulate the vibration transmission characteristics of the elastic material. However, the "stress-strain" of elastic materials
Is significantly different between the region corresponding to the static deflection and the region corresponding to the dynamic stiffness. Therefore, according to this method, as shown in FIG. As a result, a large error occurs between the simulation value and the experimental value (actually measured value).

[0004] The above problem relates to, for example, a structural analysis of a vehicle seat, in which the behavior of the vehicle seat with respect to the weight of an occupant and the vibration of the vehicle is analyzed by simulation to verify the riding comfort. This leads to a problem that the deformation or vibration characteristics of the seat cannot be simulated well. In particular, since the weight of the occupant is input to the elastic material via the atypical occupant's body line such as the back or buttocks, the operation of the simple setting of the spring constant K as described above requires such an atypical form. The problem that deformation of the vehicle seat due to the weight of the occupant cannot be simulated well tends to occur.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an analysis method capable of more accurately simulating the behavior of an elastic material to be analyzed when an external force is applied to the elastic material. It aims to provide technology.

[0006]

Means for Solving the Problems In order to achieve the above objects, the inventions described in the respective claims are constituted. According to the first aspect of the present invention, when an external force is applied to the elastic material to be analyzed, the relative stress and strain of the elastic material at a predetermined unit time are simulated to simulate the behavior of the elastic material with respect to the external force. A stress value at the analysis time T is calculated based on the amount of change. Therefore, the stress in the elastic material is calculated while reflecting the relationship between the momentary stress and the strain due to the external force, and the behavior of the elastic material with respect to the external force can be more accurately simulated. Regarding “every predetermined unit time”, the stress σ (T) can be calculated more accurately as the interval of the unit time, that is, the step size at the time of analysis is shortened. More preferably, the unit time interval (step width) is appropriately set. Here, the relative change amount of stress and strain generated in the elastic material every predetermined unit time is obtained by actually measuring the stress and strain generated in the elastic material when an external force is applied to the elastic material every predetermined sampling time. It is also possible to calculate the relative change between the two at each predetermined unit time based on the actual measurement value, or to approximately calculate the value of stress and strain at each predetermined unit time based on the actual measurement value, The relative change between the two may be determined based on the calculated value.

According to the second aspect of the present invention, the variable f (ε) relating to the compression stiffness of the elastic material is used as the relative change between the stress and the strain of the elastic material every predetermined unit time. And the differential stress Δ obtained from the variable f (ε)
By accumulating σ (t) from the start of external force loading to the desired analysis time T and adding this to the reference stress value σ0, the stress value σ ( T) will be calculated.

According to the third aspect of the present invention, the criteria for obtaining the stress and strain of the elastic material differ according to the type of external force that acts. That is, when a static compressive force is applied to the elastic material, the stress and the strain per unit time are determined based on the measurement data on the stress and the strain of the elastic material when the static compressive force is applied to the elastic material. Is required. Further, when a vibration acts on the elastic material, the stress and the strain per unit time are obtained based on the measurement data on the stress and the strain when the compressive load applied to the elastic material is removed. Note that “static compression” refers to a state in which a compressive load acts on the elastic material in a static state, such as applying a placing load to the elastic material.

According to the fourth aspect of the present invention, the structural analysis is performed on a vehicle seat having at least a foamable base material. Specifically, the vehicle seat to be analyzed has a structure in which a spring is covered with a skin material together with a foamable base material in many cases, but the present invention can be suitably applied to any case. Especially for vehicle seats, an atypical load generated by the occupant applying weight to the seat through the atypical shaped back or buttocks acts, and further, internal vibration of the engine or the like in the vehicle or Since external vibration transmitted from the outside of the running vehicle to the vehicle acts, it is possible to perform precise structural analysis that considers both external forces by calculating stress while considering the change in compression rigidity every moment. This is particularly effective when quantitatively simulating the riding comfort of an occupant in a vehicle seat. In addition, as a material of the foamable base material, for example, it is preferable that a material such as urethane or rubber, or a material obtained by appropriately combining these materials is used as a main component.

According to the invention described in claim 5, the present invention can be suitably applied to the field of structural analysis using a so-called finite element method. Specifically, by outputting the stress value σ (T) calculated for each finite element in total,
A use form such as accurately simulating the behavior of the elastic material is possible.

In the invention according to claim 6, when an external force is applied to the elastic material to be analyzed, the elastic material is determined based on a relative change amount of stress and strain per predetermined unit time for the elastic material. The stress value at the analysis time T is calculated.
Time width Δt and analysis time T for setting unit time
Is input via the input unit. The time width Δt has such a relationship that a more detailed analysis can be performed as the time width Δt is finely divided, but the calculation requires much time. Therefore, it is preferable to set appropriately while considering the balance between the accuracy of analysis and the processing time. According to the present invention, the stress in the elastic material is calculated while reflecting the relationship between the momentary stress and the strain caused by the external force, and the behavior of the elastic material with respect to the external force is more accurately simulated. .

According to the seventh aspect of the present invention, in the calculation unit of the structural analysis apparatus, the variable f (ε) relating to the compression stiffness of the elastic material is used as the relative change between the stress and the strain of the elastic material per unit time. Is calculated, and the stress value σ (T) reflecting the change of the compression stiffness of the elastic material every moment is calculated.

According to the eighth aspect of the present invention, different reference data for obtaining the stress and strain of the elastic material are stored in the data storage section of the analyzer according to the type of the external force acting. Then, when a static compressive force acts on the elastic material, the arithmetic unit performs, for each unit time, based on the measurement data regarding the stress and strain of the elastic material when the static compressive force is applied to the elastic material. Find the stress and strain of Further, when vibration is applied to the elastic material, the calculation unit calculates the stress and strain per unit time based on the measurement data on the stress and strain when the compressive load applied to the elastic material is removed. Ask.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a configuration of an elastic material structure analyzing apparatus 100 according to an embodiment of the present invention.
Is shown in The structural analysis device 100 includes an input unit 110,
The operation unit 120, the output unit 130, and the program memory 1
40 and a data memory 150. Input unit 11
Reference numeral 0 denotes a keyboard / scanner / mouse or the like, the arithmetic unit 120 includes a CPU or the like, and the output unit includes a CRT / printer or the like. A FEM (finite element method) main program 141 and a stress calculation program 143 are stored in the program memory 140, and a first stress calculation subroutine 145 and a second stress calculation subroutine 147 are stored in the stress calculation program 143. Have been. The data memory 150 includes an input data memory 151 and an actual measurement data memory 1.
53, and the actual measurement data memory 153 stores static compression test data 155, unloading test data, and dynamic compression test data 159.

In the present embodiment, the above-described structural analysis device 1
00 is the seat cushion 2 of the vehicle seat shown in FIG.
An example used for simulation analysis for ride comfort prediction at 00 is shown. As shown in FIG. 2, the seat cushion 200 includes finite elements E1, E2, E3.
n (x and n are both integers and x <n). The structural analysis work described below is performed for each of the divided finite elements, and the simulation analysis results for the entire seat cushion 200 are shown by integrating and outputting the calculated analysis results for each of the finite elements. become. Since the outline of the finite element method itself and the method itself for integrating the analysis results for each finite element are well known in the field of structural analysis of materials using the finite element method, detailed descriptions thereof are omitted for convenience. .

Structural analysis apparatus 100 according to the present embodiment
In (see FIG. 1), as preparatory work for carrying out the analysis simulation, the actual measurement data of the static compression test data 155, the unloading test data 157, and the dynamic compression test data 159 are measured, and the structure analysis device 100 measured data memory 15 set in data memory 150
3 is stored. First, details of the measurement of the actually measured data will be described in detail below.

As shown in FIG. 3, a static compression test is performed using the sample 201. The sample 201 is made of the same material as the vehicle seat 200 to be analyzed. In the static compression test, a static compression load is applied to the sample 201, and the strain ε of the sample 201 with respect to the static compression load is determined. Here, “static compression” refers to a state in which a compressive load is applied to the elastic material in a static state, such as placing a load on the elastic material and applying the load by its own weight. FIG. 4 shows the static compression test data 155 obtained as a result of the static compression test. In FIG. 4, the vertical axis indicates the stress σ (ε) generated in the sample 201, and the horizontal axis indicates the strain ε generated in the sample 201. The static compression test data 155 thus obtained is stored in an actual measurement data memory 153 (see FIG. 1) after being appropriately subjected to processing such as A / D conversion.

Further, in the present embodiment, the ultimate strain value obtained by the static compressive load acting on the sample 201 (the final deformation amount of the sample 201 subjected to the static compressive load)
, A stress value corresponding to the strain value is specified, and this stress value is included in the static compression test data 155 as “reference stress value σ0”.

Next, as shown in FIG. 5, a sample 201 made of the same material as the vehicle seat 200 to be analyzed is used.
Is subjected to an unloading test. In this test, the elastic recovery characteristic of the sample 201 to which the compressive load has been applied when the compressive load is removed is measured. That is, the elastic recovery performance when the sample 201 is unloaded is measured, and the test reflects the deformation characteristics of the sample 201 due to the vibration acting on the sample 201. In the present embodiment, the stress at the time of loading and the stress at the time of unloading are measured in the range of 10% to 70% of the thickness of the sample 201 for each 10% of the strain. FIG. 6 shows unloading test data 157 obtained as a result of the unloading test. In FIG. 6, the vertical axis indicates stress σ (ε), and the horizontal axis indicates the amount of strain with respect to the thickness of the sample 201 as a percentage. According to this, it is understood that the stress σ (ε) with respect to the strain is different between when the load is applied and when the load is unloaded, and a so-called hysteresis curve is drawn. The unloading test data 157 obtained in this manner is
After processing such as / D conversion, the actual measurement data memory 153
(See FIG. 1).

Next, as shown in FIG. 7, a dynamic compression test is performed using the sample 201. For the dynamic compression test, sample 2
Sample 2 when a predetermined compression load is applied to 01
This is a test for reflecting the damping characteristics in No. 01. For the sample 201, a material equivalent to the vehicle seat 200 to be analyzed is used. In this test, a dynamic compressive load is applied to the sample 201. Here, the term "dynamic compression load" refers to a form in which a compression load is applied to an elastic material at a predetermined speed, and forms a pair with the above-mentioned static compression load. In the present embodiment, a compressive load is applied at a speed of 1 m per second. Then, a value obtained by dividing an increase in stress during dynamic compression with respect to stress during static compression by a strain rate due to compression is calculated as a damping coefficient C. This is sample 2
01 is based on the fact that the damping characteristic is determined by the relative relationship between the strain rate due to compression and the increase in compression stiffness. FIG. 8 shows the result of the dynamic compression test in comparison with the result of the static compression. The vertical axis of the graph indicates stress σ (ε), and the horizontal axis indicates strain ε. The dynamic compression test data 159 thus obtained is stored in the actual measurement data memory 153 as described above.
(See FIG. 1).

FIG. 9 shows a flowchart of an analysis procedure in the FEM main program 141 as an example of a structural analysis step executed in the structural analysis apparatus 100. When the FEM main program 141 starts, first, initialization is performed (step S101), and then data Δt and T are input (step S10).
3). Δt is a parameter representing a step width (time width) for setting a unit time when analyzing the stress of the vehicle seat. T is a parameter representing the analysis time when trying to calculate stress at a predetermined analysis time. These values are input from the input unit 110 shown in FIG. 1 and stored in the input data memory 151 in the data memory 150.

Next, the actual measurement data is called (step S10).
5) is performed. Here, the above-mentioned static compression test data 155, unloading test data 157, and dynamic compression test data 1
59 are respectively called from the data memory 150.

In the present embodiment, two different types of stress calculation procedures are prepared according to the positive / negative determination of the strain increment Δε generated in the sample 201 (steps S107 and S10).
9, S115). In step S107, the distortion increment Δ
When it is determined that ε is positive, it is determined that the external force acting on the sample 201 is a static compressive load (in this case, the compression direction of the sample 201 is defined as positive strain). In step S109, a first stress calculation subroutine corresponding to the static compressive load is executed (step S109). If it is determined in step S107 that the strain increment Δε is negative, the sample 201 is determined to be in a form in which the sample 201 receives a stress in the anti-compression direction (unloading direction) due to an external force, that is, in a form in which vibration acts as an external force, and step S115 , A second stress calculation subroutine corresponding to vibration (an operation mode in which load and unloading are repeated) is executed.

FIG. 10 shows a first stress calculation subroutine 1
A flowchart of the analysis procedure at 45 is shown. When the first stress calculation subroutine 145 starts, the static compression test data 155 is called up (step S20).
1). The static compression test data 155 corresponds to the “stress-strain” relationship due to static compression on the sample 201. Similarly, the dynamic compression test data 159 is called (step S203). This dynamic compression test data 15
9 corresponds to the attenuation characteristic for the sample 201.

In step S205, stress σ and strain ε at time t are specified. Both the stress σ and the strain ε are specified from the static compression test data 155. Then, using the specified stress σ and strain ε,
In step S207, the compression rigidity f (ε) is calculated. The compression stiffness f (ε) is a value obtained by differentiating the stress value σ at the time t with the strain value ε, and is calculated using Expression 3 shown in FIG.

Next, in step S209, a differential stress Δσ (t) is calculated. The differential stress Δσ (t) is obtained by integrating f (ε) with respect to a predetermined time increment Δt, and is calculated using Expression 2 shown in FIG. Then, in step S211, the stress value σ (t) of the sample 201 at the time t is calculated. The stress value σ (t) is calculated using Expression 1 shown in FIG. The stress value σ (t) is calculated by adding a value obtained by summing the differential stress Δσ (t) with respect to elapsed time, a reference stress value σ0, and a value obtained by multiplying a differential value of strain by a damping coefficient C. Is done. Here, the differential stress Δσ (t) is calculated as shown in FIG.
The reference stress value σ0 is specified when measuring the static compression test data 155, and the damping coefficient C is specified based on the dynamic compression test data 159. . As described above, when the stress value σ (t) of the sample 201 at the predetermined time t is calculated, the first stress calculation subroutine 145 ends, and the process returns to the FEM main program 141 shown in FIG.

FIG. 11 shows a second stress calculation subroutine 1
A flowchart of the analysis procedure at 47 is shown. When the second stress calculation subroutine 147 starts, the unloading test data 157 is called up (step S30).
1). The unloading test data 157 corresponds to a “stress-strain” relationship based on vibration (repetition of load and unloading) acting on the sample 201. Similarly, the dynamic compression test data 159 is called (step S303). The dynamic compression test data 159 corresponds to the damping characteristic for the sample 201, and is equivalent to that in the first stress calculation subroutine 147.

In step S305, stress σ and strain ε at time t are specified. Both the stress σ and the strain ε are specified from the unloading test data 157. Then, using the specified stress σ and strain ε, the compression stiffness f (ε) is calculated in step S307.
The compression stiffness f (ε) is a variable obtained by differentiating the stress value σ at the time t with the strain value ε, and is calculated using Expression 3 shown in FIG.

Next, in step S309, a differential stress Δσ (t) is calculated. The differential stress Δσ (t) is obtained by integrating f (ε) with respect to a predetermined time increment Δt, and is calculated using Expression 2 shown in FIG. Then, in step S311, the stress value σ (t) of the sample 201 at the time t is calculated. The stress value σ (t) is calculated using Expression 1 shown in FIG. The differential stress Δσ when calculating the stress value σ (t)
The meaning of (t), the reference stress value σ0, and the damping coefficient C are the same as in the case of the above-described first stress calculation subroutine 145, and thus detailed description is omitted. As described above, when the stress value σ (t) of the sample 201 at the predetermined time t is calculated, the second stress calculation subroutine 147 ends, and FIG.
Return to the FEM main program 141 shown in FIG.

As shown in FIG. 9, when the first stress calculation subroutine 145 is completed, the FEM main program 1
At 41, it is determined whether t <T (step S11).
1) It is determined whether or not the analysis time T corresponding to the stress value σ (T) as the calculation target has been reached. If it is determined that the analysis time T has not yet been reached, the time interval, that is, a value obtained by adding Δt, which is the analysis time width, to t is set as a new time t, and the process returns to step S107.

Similarly, as shown in FIG. 9, when the second stress calculation subroutine 147 ends, the FEM main program 141 determines whether t <T (step S117), and the target stress value σ It is determined whether or not the stress (t) has been calculated for each unit time until the analysis time T corresponding to (T). If it is determined that the analysis time T has not yet been reached, a value obtained by adding Δt, which is a time step, to t is set as a new time t, and the process returns to step S115. Since the process does not return to step S107, the setting is such that when the second stress calculation subroutine 147 is started, the second stress calculation subroutine 147 is always used in the subsequent analysis work. In other words, when vibration is applied to the sample 201 on which the static compression load is applied, the data used for the stress calculation is switched from the static compression test data 155 to the unloading test data 157, and the subsequent stress is applied. In the calculation, the unloading test data 157 is used.

When it is determined “No” in the above steps S111 to S117, that is, when it is determined that the analysis time T has been reached, the stress value σ (σ) calculated in the first or second stress calculation subroutine 145,147. t)
Is output from the output unit 130 (see FIG. 1) as the target calculated value σ (T) (step S121). In this embodiment, the stress values σ1 (T) to σx calculated for each finite element over the elements E1 to Ex to En shown in FIG.
(T) to σn (T), the seat cushion 20
The result is output from the output unit 130 as the analysis result for the entirety. Thus, the FEM program 141 ends.

FIG. 13 shows the timing of switching between the static compression test data and the unloading test data. That is, when a vibration is applied to a sample to which a static compressive load has been applied, a strain in a negative direction (or a stress in a negative direction) due to the vibration acts to trigger an unloading test. The stress σ (ε) and the strain ε are obtained based on the data.
Further, when a load is applied again in the case of periodic vibration or the like, the stress σ (ε) and the strain ε are continuously obtained based on the unloading test data 157.

FIG. 14 shows the characteristics of the compression rigidity when the vibration acts. That is, the compression stiffness f (ε) calculated based on the stress σ (ε) and the strain ε obtained based on the unloading test data 157 is obtained. FIG.
In FIG. 4, the vertical axis indicates the compression rigidity f (ε), and the horizontal axis indicates the strain ε.

As shown in FIG. 15, with respect to the seat cushion 200 to be analyzed in the present embodiment, the weight of the occupant sitting on the vehicle seat is adjusted according to the body type (buttock or waist). Acting from above, the vibration of the vehicle and the like acts from below seat cushion 200. Even in such a case, an accurate analysis result could be obtained in the structural analysis according to the present embodiment. As one specific verification work of the analysis result, as shown in FIG. 16, the analysis result according to the present embodiment was compared with the actually measured value for the displacement acceleration (vibration acceleration) of the seat cushion. As understood from FIG. 16, the analysis result and the measured value are almost the same,
It is shown that a good simulation has been performed.

[0036]

According to the present invention, there is provided an analysis technique capable of more accurately simulating the behavior of an elastic material to be analyzed when an external force is applied to the elastic material. Was.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall structure of a structural analysis device according to the present embodiment.

FIG. 2 is a diagram showing a configuration of a seat cushion of a vehicle seat to be analyzed.

FIG. 3 is a diagram showing an aspect of a static compression test.

FIG. 4 is a graph showing static compression test data obtained as a result of a static compression test.

FIG. 5 is a diagram showing an aspect of an unloading test.

FIG. 6 is a graph showing unloading test data obtained as a result of the unloading test.

FIG. 7 is a diagram showing an aspect of a dynamic compression test.

FIG. 8 is a graph showing dynamic compression test data obtained as a result of the dynamic compression test.

FIG. 9 is a flowchart showing an FEM analysis procedure in the structural analysis apparatus.

FIG. 10 is a flowchart showing an analysis procedure in a first stress calculation subroutine.

FIG. 11 is a flowchart showing an analysis procedure in a second stress calculation subroutine.

FIG. 12 shows theoretical formulas for calculating a compression rigidity f (ε), a differential stress Δσ (t), and a stress value σ (t) at a predetermined time t.

FIG. 13 is a graph showing the timing of switching between static compression test data and unloading test data.

FIG. 14 is a graph showing characteristics of compression stiffness when vibration is applied.

FIG. 15 is a diagram showing a state in which the weight of the occupant acts on the seat cushion to be analyzed from above according to the body shape, and vibration acts from below.

FIG. 16 is a graph showing a comparison between an analysis result according to the present embodiment and an actually measured value of a displacement acceleration (vibration acceleration) of a seat cushion.

FIG. 17 is a diagram showing an equivalent model in a structural analysis of a conventional elastic material.

FIG. 18 shows a stress calculation formula used for a structural analysis of a conventional elastic material.

FIG. 19 is a graph showing a state where a stress-strain curve and a compression stiffness in a conventional structural analysis are processed by a constant with respect to a static compression load.

FIG. 20 is a graph showing an error in vibration characteristics when the compression stiffness is determined by a static compression load.

FIG. 21 is a graph showing a stress-strain curve in a conventional structural analysis and a state in which compression stiffness is processed by a constant in dynamic stiffness.

FIG. 22 shows a case where compression stiffness is determined by dynamic stiffness.
FIG. 9 is a diagram illustrating an error relating to deformation characteristics.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 Structural analysis device 110 Input unit 120 Operation unit 130 Output unit 140 Program memory 141 FEM main program 143 Stress calculation program 145 First stress calculation subroutine 147 Second stress calculation subroutine 150 Data memory 151 Input data memory 153 Actual measurement data memory 155 Static compression test data 157 Unloading test data 159 Dynamic compression test data 200 Seat cushion 201 Sample

Claims (8)

[Claims] 1. A method for simulating a behavior of an elastic material with respect to an external force when an external force is applied to the elastic material, based on a relative change amount of stress and strain generated in the elastic material every predetermined unit time. Calculating the stress σ (T) generated in the elastic material at a predetermined analysis time T. 2. The method for analyzing a structure of an elastic material according to claim 1, wherein the calculation of the stress σ (T) is performed when a predetermined external time is applied to the elastic material. By differentiating the generated stress σ with the strain ε generated in the elastic material at the predetermined time,
A first step of obtaining a variable f (ε) relating to the compression stiffness of the elastic material at the predetermined time; and a reference stress value σ0 corresponding to a static deformation amount of the elastic material.
And a variable f (ε) relating to the compression stiffness of the elastic material is integrated over a predetermined time increment to obtain a differential stress Δσ
(T), and adding a value obtained by accumulating the differential stress Δσ (t) from the start of the external force load to a predetermined analysis time T to the reference stress value σ0, thereby obtaining the analysis time T Stress value at
A fourth step of obtaining (T). 3. The method for analyzing the structure of an elastic material according to claim 1, wherein the first measurement data relating to the stress and strain of the elastic material when a static compressive force is applied to the elastic material; Further comprising preparing second measurement data relating to stress and strain of the elastic material when unloading the compressive load applied to the elastic material; The strain is determined based on the first measurement data for the static compressive force acting on the elastic material, and is determined based on the second measurement data for the vibration acting on the elastic material. A structural analysis method for an elastic material, characterized by being obtained by: 4. A method for analyzing the structure of an elastic material according to claim 1, wherein the elastic material to be analyzed is a vehicle seat having at least a foamable base material. Analysis method of elastic material. 5. The method for analyzing the structure of an elastic material according to claim 1, wherein the calculation of the stress value σ (T) at the predetermined analysis time T is performed using a finite element of the elastic material. A structural analysis method for an elastic material, wherein the method is performed every time. 6. An input unit, a calculation unit, and an output unit, wherein the input unit is supplied with a time width Δt and an analysis time T for setting a unit time in structural analysis of the elastic material. The unit is configured to input an external force based on a relative change amount of stress and strain generated in the elastic material per unit time set based on the input time width Δt when an external force is applied to the elastic material. The stress σ (T) generated in the elastic material at the calculated analysis time T is calculated. The calculated stress σ (T) is output to the output unit, whereby the behavior of the elastic material with respect to an external force is calculated. An apparatus for analyzing the structure of an elastic material, wherein a simulation is performed. 7. An apparatus for analyzing the structure of an elastic material according to claim 6, wherein said calculating section calculates a stress σ generated in said elastic material in a predetermined time when an external force is applied to said elastic material. By differentiating the strain ε generated in the elastic material at the predetermined time,
By calculating a variable f (ε) relating to the compression stiffness of the elastic material at the predetermined time and integrating the variable f (ε) relating to the compression stiffness of the elastic material by a predetermined time increment, the differential stress Δσ
(T) is calculated, and a reference stress value σ0 corresponding to a static deformation amount of the elastic material is calculated.
By adding a value obtained by accumulating the differential stress Δσ (t) from the start of the external force load to the predetermined analysis time T to the reference stress value σ0, the stress value σ (T) at the analysis time T is calculated. A structural analysis device for an elastic material, wherein the structural analysis is performed. 8. An apparatus for analyzing the structure of an elastic material according to claim 6, wherein the first measurement data relating to stress and strain of the elastic material when a static compressive force is applied to the elastic material; A data storage unit configured to hold second measurement data relating to stress and strain of the elastic material when the compression load applied to the elastic material is released; For the stress and strain generated in the elastic material, the static compression force acting on the elastic material is determined based on the first measurement data, and the vibration acting on the elastic material is determined based on the first measurement data. An apparatus for analyzing the structure of an elastic material, wherein the apparatus is obtained based on the measurement data of 2.