JP2006240448A - Method for arranging reinforcing member of panel structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for arranging a reinforcing member of a panel structure capable of eliminating dispersion of the panel structure after changing the structure, and reducing the number of calculation when compatibly materializing the tensile rigidity and the minimum weight. <P>SOLUTION: The method includes a step of obtaining the load distribution factor of a main member and a reinforcing member from the displacement in the working direction of the strain energy accumulated in a panel structure (2) and the load applied to the panel structure, a step of preparing an approximation formula of the load-displacement curve according to the load distribution factor of the main member (4) and the reinforcing member (12), and a step of performing the non-linear optimization to compatibly minimize the tensile rigidity and the weight of the panel structure based on the approximation formula and the standard of evaluation of the tensile rigidity of the panel structure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for arranging a reinforcing member for a panel structure, and more particularly, to a technique for achieving both the rigidity and weight optimization of the panel structure.

  This type of panel structure, for example, a truck door panel, is required to have high rigidity. Tension rigidity is recognized by the feeling of stickiness of the door panel, and a large feeling of stickiness is a factor that reduces the product quality. On the other hand, even if this tension rigidity can be ensured, if the weight of the door increases significantly, it will still be a factor in reducing the merchantability. Therefore, in order to satisfy the rigidity and weight minimization of a shell structure that is difficult to obtain a curvature like a door panel, it is effective to attach a reinforcing material (reinforcing member) to the outer panel (main member).

Here, in order to achieve both the above-mentioned tension rigidity and weight minimization, the present applicant has proposed a technique for optimizing the structure by a stepwise method of minimizing the weight after securing the tension rigidity. (For example, refer to Patent Document 1). According to this technique, since the tension stiffness after the structure change is secured in advance, it is not necessary to predictively evaluate the tension stiffness after the change from past accumulated data. That is, it is not necessary to judge the quality of the panel structure after the change based on the experience of a skilled engineer.
JP 2001-171349 A

  By the way, in the prior art, the tension stiffness in the initial stage of deformation of the panel structure is affected by the rigidity of the outer panel and the arrangement position of the reinforcing material, whereas the tension stiffness in the subsequent deformation region depends on both the outer panel and the reinforcing material. This is in consideration of the point affected by the rigidity of the steel. Then, by analysis such as finite element method (FEM), the tension rigidity is obtained in the initial stage of deformation, and in the deformation area after the initial stage of deformation, the load sharing is obtained from the strain energy of the outer panel and the reinforcing material to secure the tension rigidity, A member having a large load sharing and a small weight is increased (for example, an increase in plate thickness), and a member having a small load sharing and a large weight is decreased (for example, a decrease in plate thickness) to minimize the weight.

However, with this stepwise structure optimization method, there is a concern that the experience of a skilled engineer is still necessary in order to eliminate variations in the panel structure after the change. This is because the selection of the member for changing the plate thickness is still a factor that greatly depends on the experience of the engineer.
The problem of achieving both the above-described tension rigidity and weight minimization can be considered as a nonlinear structure optimization problem. This is because the tension stiffness of the panel structure is described by a load-displacement curve, and this load-displacement curve exhibits non-linear behavior. The nonlinear structure optimization may be performed by various estimation methods such as design sensitivity analysis and response surface method, but there is a problem that the number of calculations increases with these methods.

  The present invention has been made in view of such problems, and in order to achieve both rigidity and weight minimization, a panel that can eliminate variations in the panel structure after the structure change and reduce the number of calculations. It is an object of the present invention to provide a method for arranging a reinforcing material for a structure.

  In order to achieve the above object, a reinforcing material disposing method for a panel structure according to claim 1 is a panel structure having a main member and a reinforcing material, and a nonlinear FEM analysis from a load acting on the panel structure. Determining the strain energy stored in the panel structure based on the above, determining the ratio of the load sharing with respect to the load of the main member and the reinforcing material from the displacement of the strain energy and the acting direction of the load, and quantifying as a load sharing rate; Nonlinear structural optimization that balances the stiffness and weight minimization of the panel structure based on the process of creating an approximate expression of the load-displacement curve based on the load sharing ratio and the evaluation formula of the approximate expression and the tension stiffness of the panel structure And a step of performing the conversion.

In addition, the invention according to claim 2 is characterized in that the approximate expression of the load-displacement curve includes, in addition to the load sharing ratio, the plate thicknesses of the main member and the reinforcing material as parameters.
Further, the invention according to claim 3 is characterized in that the panel structure is a door panel of a truck, the main member is an outer panel, and the reinforcing material is a reinforcing material attached to the inner surface of the outer panel.

  Therefore, according to the reinforcing material disposing method of the panel structure of the present invention described in claim 1, the tension rigidity of the panel structure is predicted by an approximate expression using the load sharing ratio. Based on this, non-linear structural optimization is attempted. That is, as in the past, the relationship between the weight ratio of the main member and the reinforcing material and the plate thickness and the relationship between the load sharing ratio and the plate thickness are obtained, and the weight is minimized after securing the rigidity of the panel structure. Compared with the stepwise reinforcing material disposing method, the factors depending on the experience of the engineer are further reduced. As a result, the variation in the panel structure is reduced and the development time is shortened.

In addition, in order to secure the tension rigidity of the panel structure, the load sharing rate is calculated from the result of the non-linear FEM analysis only once instead of plotting the result of the non-linear FEM analysis multiple times to obtain the load-displacement curve. This makes it possible to derive an approximate expression using, so this also contributes to shortening the development time of the panel structure.
Furthermore, the number of calculations can be reduced compared with an estimation method based on nonlinear structure optimization such as design sensitivity analysis or response surface method.

According to the invention of claim 2, the parameter of the approximate expression includes the load sharing ratio of the main member and the reinforcing material, so that the tension rigidity for securing the rigidity of the panel structure is accurate and easy. In addition, by including the plate thicknesses of the main member and the reinforcing material, the plate thicknesses for optimizing the weight of the panel structure can be set accurately and easily.
Furthermore, according to the third aspect of the present invention, when applied to a panel structure that requires a high rigidity and a sufficient weight reduction, such as a truck door panel, the merchantability of the truck is further improved.

Hereinafter, the reinforcing material disposing method of the panel structure according to the present invention will be described with reference to the drawings.
First, an approximate expression of a load-displacement curve based on a load sharing ratio is obtained using a simple panel structure, and a structure optimization method using this approximate expression will be described.
As shown in FIG. 1, the panel structure includes a rectangular flat plate-shaped main member 4, and the ratio of the length of the short side to the long side (aspect ratio) is set to about 1: 2. Yes. Each end portion of the main member 4 is simply supported, and a reinforcing member (reinforcing member) 12 is attached along the longitudinal direction of the main member 4 at a substantially central position of the main member 4.

  When the load P acting on the panel structure is assumed to be a displacement u in the acting direction of the load P, the load-displacement curve is calculated based on nonlinear FEM analysis. In this calculation method, an incremental method is used in which the load at the application point (evaluation point) u is sequentially increased from 0 to P in increments of small increments and the respective increments of load (stress) and displacement (strain) at the evaluation point u are obtained. Is done. The load P, the displacement u, and the strain energy U stored in the panel structure are in the relationship of the following expression (1) from Castiriano's theorem.

First, it is assumed that there are a plurality of members including the main member 4 and the reinforcing material 12. Assuming that the strain energy U _i stored in a predetermined member i (= 1 to n, the same shall apply hereinafter), the following equation (2) is obtained. When this equation (2) is substituted into equation (1), The following formula (3) is obtained. The formula (3) P _i is defined as the load distribution member i of. Specifically, the strain energy U _i is expressed as the following equation (4) obtained by partial differentiation with respect to the displacement u.

Also, define the load distribution rate y _i of the member i as a percentage of the load distribution P _i with respect to the load P. The details are shown as the following equation (5).
y _i = P _i / P (5)
Here, assuming that the specific gravity γ _{i of the} member i, the plate thickness t _i , and the surface area A _i , the total weight W of the panel structure is represented by the following equation (6).

Next, when the plate thickness t _i is set as a design variable, and an upper limit t _iu and a lower limit t _il are respectively set, the following equation (7) is obtained.
t _il <t _i <t _iu (7)
Next, if the evaluation criterion P _c (u) of the tension stiffness at the evaluation point u is set, the condition for the tension stiffness P (u) of the evaluation point u to satisfy the evaluation criterion is expressed by the following equation (8). Note that this evaluation criterion P _c (u) corresponds to an evaluation criterion for tension stiffness determined from market performance or the like.
P (u) −P _c (u) ≧ 0 (8)
Here, if the subscript 0 is attached to the state before the structural change, and the subscript is not attached to the state after the structural change, the load sharing P _i0 before the structural change of the member i is expressed by the following equation (9), load distribution P _i after structural changes are shown respectively by the following equation (10).

By the way, the load sharing P _i after the structural change of the member i is described by the load sharing P _i0 before the structural change, the plate thicknesses t _i0 and t _i before and after the structural change of the member _i , and the parameter mi representing the member characteristics. Assume that you can. This assumes that the tension rigidity of the panel structure is proportional to the mi thickness of the plate thickness. This assumption is known in Patent Document 1 already described, and is specifically expressed by the following equation (11). Therefore, the following equation (12) is obtained from the above equations (10) and (11). The formula (12) is an approximate formula (prediction model) of a load-displacement curve using the load sharing ratio.
P _i = P _i0 (t _i / t _i0 ) ^mi = y _i0 P ₀ (t _i / t _i0 ) ^mi
= Y _i0 P ₀ Z _i ^mi (11)

Y _i0 is a load sharing ratio before the structure change, and Z _i is a thickness ratio before and after the structure change. That is, the load sharing ratio y _i0 is expressed by the following equation (5) to the following equation (13), and the plate thickness ratio Z _i is expressed by the following equation (14).
y _i0 = P _i0 / P ₀ (13)
Z _i = t _i / t _i0 (14)
The following equation (15) is obtained from the above equations (8) and (12). Here, in the equation (15), if the total number q of incremental steps when the above incremental method is applied, the inequality of the following equation (16) is obtained (j = 1 to q). That is, as in the equation (16), the prediction model P (u _j ) / P ₀ (u _j ) in the equation (12) and the evaluation criterion P _c (u _j ) determined from the market performance are given. If so, the optimum shape of the panel structure is automatically calculated.

  As described above, in the method for disposing the reinforcing member of the panel structure according to the present invention, the above equation (6) is an objective function, equations (7) and (14) are upper and lower limit constraints (constraints), It can be seen that equation (16) results in a problem of linear programming with inequality constraints. The structure optimization method can be applied to all panel structures having n members. Here, an example in which a truck door panel is used will be described.

  As shown in FIG. 2, the door panel 2 is configured in a state where the outer panel 4 and the inner panel 6 are bonded to each other. The outer half of the outer panel 4 is formed as a window frame 8 in the upper half, and the lower half is formed as a door panel lower part 10. The lower portion 10 of the door panel is added along the lower end of the side window, and the additional portion extends in a direction crossing the outer panel 4.

Further, a reinforcing material 12 is attached to the inner surface of the outer panel 4 in order to ensure the tension rigidity of the portion surrounded by the window frame 8 and the door panel lower part 10. For example, in this embodiment, the reinforcing material 12 is bonded to the outer panel 4. The reinforcing member 12 has a beam shape, and the structure thereof is formed into a cross-sectional hat shape, and the necessary rigidity of the reinforcing member 12 is ensured.
A load P that sequentially increases from 0 is applied to the outer panel 4 at a predetermined evaluation point u. At this time, since the window frame 8 has little influence on the tension rigidity, the outer panel 4 can be approximated by a rectangular flat plate model in which the aspect ratio is set to about 1: 2 (FIG. 1). The reinforcing member 12 is disposed at a substantially central position along the longitudinal direction of the outer panel 4 (arrangement plan of the lateral reinforcing member). Moreover, the said load P shall act on the approximate center position of the upper side part of the outer panel 4 divided by this reinforcing material 12, as FIG. 1 shows.

Next, a method for arranging the reinforcing member 12 on the door panel 2 configured as described above will be described. The reinforcing material arranging method according to the present invention can be applied to a vertical reinforcing material arrangement plan and a vertical and horizontal reinforcing material arrangement plan in addition to the horizontal reinforcing material arrangement plan.
Specifically, the approximate expression of the load-displacement curve based on the load sharing ratio in the door panel 2 is expressed as the following expression (17) when the above expression (12) is used.

In the formula (17), the subscript 1 indicates the outer panel 4, the subscript 2 indicates the reinforcing material 12, and the subscript 3 indicates all components (for example, the inner panel 6 and the adhesive) other than the outer panel 4 and the reinforcing material 12. ing.
In addition, the member characteristics and constraint conditions of each constituent member before the structure change will be described.

That is, as shown in Table 1, for the outer panel 4, the thickness t ₁₀ is 0.78 mm, the parameter m1 is 2.3 representing the member properties, the equation (7) and the lower limit constraints on the equation (14) Are 0.68 ≦ t ₁ ≦ 0.88 and 0.872 ≦ Z ₁ ≦ 1.13. For reinforcing material 12, the thickness t ₂₀ is the reference value t _S0, parameter m2 is 1.2, the upper limit constraints _{0.5t S0 ≦ t 2 ≦ 2t S0} , is 0.5 ≦ Z ₂ ≦ _2.

This parameter mi is set by the method of least squares from a load-displacement curve near the maximum load Pm. This maximum load Pm is the maximum value of the load assumed to be applied to the outer panel 4 in view of the practical use of the truck (refer to Vol.31, No. 1, etc. of the Automobile Technical Society Proceedings). In addition, about all the structural members (subscript 3) other than the outer panel 4 and the reinforcing material 12, there is almost no load sharing and a structural change is not performed. That is, the plate thickness t ₃₀ remains unchanged, and the plate thickness ratio Z ₃ = 1. Therefore, the parameter m3 may be an arbitrary value, and the weight ratio is not considered.

And the total weight W of the door panel 2 after the structure change which is a target function is set. Specifically, the total weight W is expressed by the following equation (18) from the above equations (6) and (14). Further, assuming that the weight of the outer panel 4 is 1, the weight of the reinforcing member 12 is 0.05. The specific gravity γ _i is represented by the following equation (19), and the surface area A _i is represented by the following equation (20) (i = 1 to 3).

W = γ ₁₀ t ₁₀ A ₁₀ Z ₁ + γ ₂₀ t ₂₀ A ₂₀ Z ₂ + γ ₃₀ t ₃₀ A ₃₀ (18)
γ _i = γ _i0 (19)
A _i = A _i0 (20)
Here, as shown in the following equation (21), when γ ₁₀ t ₁₀ A ₁₀ in the equation (18) is set to W ₁₀ , the relationship between the weights of the outer panel 4 and the reinforcing member 12 as shown in Table 1 (1: 0.05), the following formula (22) is obtained. For simplification of calculation, when W−γ ₃₀ t ₃₀ A ₃₀ is newly set as W in equation (18) and the above equations (21) and (22) are substituted into equation (18), It is shown as equation (23).

W ₁₀ = γ ₁₀ t ₁₀ A ₁₀ (21)
γ ₂₀ t ₂₀ A ₂₀ / W ₁₀ = 0.05 (22)
W / W ₁₀ = Z ₁ + 0.05Z ₂ (23)
Next, evaluation criteria and structural optimization will be described. First, the structure optimization in the embodiment is the sum of the load sharing rate of the outer panel 4, the load sharing rate of the reinforcing material 12, and the load sharing rates of all the constituent members other than the outer panel 4 and the reinforcing material 12. This is done under the assumption that it is 1. However, as shown in FIG. 3, between the predetermined evaluation points u ₁ and u ₂ , all the components other than the outer panel 4 and the reinforcing material 12 can be assumed to be small if the influence of the load sharing ratio is small. Therefore, the structure optimization is actually performed under the assumption that the sum of the load sharing rate of the outer panel 4 and the load sharing rate of the reinforcing member 12 is 1.

Subsequently, an approximate expression of a load-displacement curve based on the load sharing ratio of the above-described expression (17) is expressed as the following expression (24).
P (u) / P ₀ (u) = y ₁₀ Z ₁ ^2.3 + y ₂₀ Z ₂ ^1.2 + y ₃₀ (24)
As described above, the third term y ₃₀ on the right side of the equation (24) can be omitted because all the constituent members other than the outer panel 4 and the reinforcing member 12 have almost no load sharing. Therefore, the following equations (25) and (26) are obtained.

P (u) / P ₀ (u) ≈ (1−y ₂₀ ) Z ₁ ^2.3 + y ₂₀ Z ₂ ^1.2
= (1-y) Z ₁ ^2.3 + yZ ₂ ^1.2 (25)
y = y ₂₀ (26)
Therefore, from the equation (25), the above equation (16) is expressed as the following equation (27) (i = 1 to q).

P ₀ (u _i ) ((1−y (u _i )) Z ₁ ^2.3 + y (u _i ) Z ₂ ^1.2 ) −P _c (u _i ) ≧ 0 (27)
Then, a range above equation (27) to meet the outer panel 4 of the plate thickness ratio Z ₁ and the reinforcing member 12 of the plate thickness ratio Z ₂ in the above modification step u = u _i. More specifically, as shown in FIG. 4, to calculate the thickness ratio Z ₂ of the outer panel 4 of the plate thickness ratio Z ₁ and the reinforcing member 12 that satisfies the above equation (27) for each step by the incremental method Plot. When the reference values of the respective plate thickness ratios are Z _1c (= 0.851) and Z _2c (= 1.62), in this example, u ₁ = 2.21 mm and u ₂ = 6.69 mm are evaluated points. In this case, the region where Z ₁ is larger than the evaluation line 2 (the one-dot chain line in FIG. 4) based on u ₂ when 0 ≦ Z ₂ ≦ Z _2c satisfies the evaluation criteria such as market performance, and Z _2c ≦ Z ₂ The region where Z ₁ is larger than the evaluation line 1 (solid line in FIG. 4) based on u ₁ satisfies the evaluation criteria such as market performance. As the evaluation points u ₁ and u _{2, the} point having the smallest margin ((P ₀ (u) −P _c (u)) / P _c (u)) is selected from the small and large regions of the above deformations. The region where the deformation is small and the influence of the outer panel 4 is large is selected as the evaluation point u ₁ , and the region where the deformation is large and the influence of the reinforcing member 12 is large is selected as the evaluation point u ₂ .
Table 2 shows data necessary for structure optimization at each of these evaluation points u ₁ and u ₂ .

Accordingly, simultaneous inequalities of the following equations (28.1) and (28.2) are obtained from these Table 2 and the above equation (27). It should be noted that the equal signs in these equations (28.1) and (28.2) indicate the values of the evaluation line ₁ based on u ₁ and the evaluation line ₂ based on u ₂ , respectively.

(1−0.0459) Z ₁ ^2.3 + 0.0459Z ₂ ^1.2 ≧ 0.184 / 0.249 (28.1)
(1-0.220) Z ₁ ^2.3 + 0.220Z ₂ ^1.2 ≧ 0.931 / 0.999 (28.2)
The solution of these simultaneous inequalities is the following equation (29.1) when 0 ≦ Z ₂ ≦ Z _2c , and the following equation (29.2) when Z _2c ≦ Z ₂ .
Z ₁ ^2.3 + 0.282Z ₂ ^1.2 ≧ 1.19 (29.1)
Z ₁ ^2.3 +0.0481 Z ₂ ^1.2 ≧ 0.776 (29.2)
Therefore, the relationship between Z ₂ and W / W ₁₀ is as follows. When Z ₁ is eliminated from the equation (29) and the equation (23), the following equation (30.1) and Z are satisfied when 0 ≦ Z ₂ ≦ Z _2c : _{When 2c} ≦ Z ₂ , the following expression (30.2) is obtained.

W / W ₁₀ ≧ (1.19−0.282Z ₂ ^1.2 ) ^{1 / 2.3} + 0.05Z ₂ (30.1)
W / W ₁₀ ≧ (0.776−0.0481Z ₂ ^1.2 ) ^{1 / 2.3} + 0.05Z ₂ (30.2)
Then, the relationship between Z ₂ and the above formulas (30.1) and (30.2) is shown in FIG. 5, and the region where W / W ₁₀ is larger than these formulas is structurally changed. The latter weight ratio is satisfied. Further, Z _2c = 1.62 is the intersection of the equations (circles in FIG. 5), and W / W ₁₀ takes the smallest value. That is, when we describe Z _1c from FIGS. 4 and 5, W / W ₁₀ is, Z _1c = 0.851, it can be seen that the minimum value 0.932 at Z _2c = 1.62.

However, as described above, the upper and lower limit constraints of the outer panel 4 are 0.872 ≦ Z ₁ ≦ 1.13. Therefore, when Z _1c is set to Z _1c = 0.872 and a combination of Z _2c = 1.62 is selected, W / W ₁₀ becomes the minimum value 0.953 (marked with ● in FIG. 5). That is, while the weight ratio W ₀ / W ₁₀ before the structure change was 1.05, the weight ratio W / W ₁₀ after the structure change was 0.953, and the entire door panel 2 was calculated from the above equation (23). A weight reduction of about 9.2% is achieved in terms of weight ratio.

On the other hand, when the plate thickness ratio Z ₂ of the reinforcing member 12 is selected to be safer than Z _2c = 1.62, and the combination of Z _1c = 0.872 and Z ₂ = 2 is selected, W / W ₁₀ is the minimum. The value is 0.972 (♦ mark in FIG. 5). That is, while the weight ratio W ₀ / W ₁₀ before the structure change was 1.05, the weight ratio W / W ₁₀ after the structure change was 0.972, which is about 7 in terms of the weight ratio of the door panel 2 as a whole. 4% weight reduction is achieved.

As described above, the optimum shape of the door panel 2 can be calculated from the prediction model of the above equation (24) and the evaluation criteria as in the above equation (27).
Furthermore, with reference to FIG. 6, confirmation of the tension rigidity in the load-displacement curve accompanying the structural change of the Example mentioned above is confirmed. In addition, the load of the figure is described by the ratio with respect to the said maximum load Pm.

The load-displacement curve indicated by the alternate long and short dash line in the figure is the evaluation standard P _c / Pm, and the ● mark in the figure is the result of structural analysis by directly substituting the plate thickness after the structural change (P (Indicated in (FEM) / Pm).
On the other hand, the load-displacement curve indicated by the solid line in the figure shows a case where the combination of Z _1c = 0.872 and Z ₂ = 2 is selected among the cases where the above structural change is made, and the weight ratio of the door panel 2 is A load-displacement curve P (approximate) / Pm that achieves a weight reduction of about 7.4% and approximates an optimum value. The difference between P (approximate) / Pm and P (FEM) / Pm is about 1.8%, which is almost the same. That is, it is estimated that P (approximate) / Pm has sufficient prediction accuracy.

Furthermore, the load-displacement curve indicated by a broken line in the figure is a combination of Z _1c = 0.872 and Z ₂ = 1.62 among the cases where the above structural change is made, and the weight ratio of the door panel 2 is The optimum load-displacement curve P (optimum) / Pm that achieves a weight reduction of about 9.2%. This P (optimum) / Pm substantially overlaps the evaluation criterion P _c / Pm when the load is small, and also approaches the evaluation criterion P _c / Pm when the load is large. That is, it can be seen that the margin with respect to this evaluation criterion P _c / Pm is smaller than the other load-displacement curves, and that highly accurate structural optimization has been performed.

As described above, according to the reinforcing member arranging method of the door panel 2 of the present embodiment, first, a load-displacement curve is obtained from the load P acting on the door panel 2 by non-linear FEM analysis, and from this load-displacement curve. A step of obtaining the strain energy U _i stored in the door panel 2, and a step of _obtaining a ratio of the load sharing P _i0 to the load P ₀ of the outer panel 4 and the reinforcing material 12 from the strain energy U _i and the displacement u in the acting direction of the load P; Then, the ratio is quantified as the load sharing ratio y _i0 of the outer panel 4 and the reinforcing material 12 (procedure 1 above).

Next, a load-displacement curve based on the load sharing ratio y _i0 , that is, an approximate expression of tension stiffness P / P using the load sharing ratio y _{i0 of} the outer panel 4 and the reinforcing member 12 and the plate thickness ratio t _i / t _i0 as parameters. _The process of creating ₀ is performed (procedure 2 above).
Then, if an evaluation standard P _c for the tension stiffness of the door panel 2 is given to this approximate expression, an optimal shape is automatically calculated, and a non-linear structure optimization process that achieves both tension stiffness and weight minimization is performed ( The procedure 3).

  Therefore, as in the prior art, the relationship between the weight ratio of the outer panel 4 and the reinforcing material 12 and the plate thickness and the relationship between the load sharing ratio and the plate thickness are obtained, and the weight is minimized after securing the rigidity of the door panel 2. For example, the work of selecting the outer panel 4 and the reinforcing material 12 for changing the plate thickness based on the experience of a skilled engineer becomes unnecessary, as compared to the stepwise reinforcing material disposing method. There are even fewer factors that depend on As a result, the variation of the door panel 2 is reduced and the development time is shortened.

In addition, in order to secure the tension rigidity of the door panel 2, the load sharing rate y is not obtained from the result of the nonlinear FEM analysis only once, rather than by plotting the result of the nonlinear FEM analysis a plurality of times to obtain the load-displacement curve. _Since the approximate expression P / P _{0 of} the tension stiffness using _{i 0} can be derived, this point also contributes to shortening the development time of the door panel 2. Furthermore, the number of calculations can be reduced compared with an estimation method based on nonlinear structure optimization such as design sensitivity analysis or response surface method.

Furthermore, when the parameter of the approximate expression P / P ₀ of the tension stiffness includes the load sharing ratio y _i0 , the tension stiffness for ensuring the rigidity of the door panel 2 can be accurately and easily set, and the outer panel 4 and the respective plate thicknesses t _i of the reinforcing members 12 make it possible to accurately and easily set the respective plate thicknesses for optimizing the weight of the door panel 2.
In addition, the structure optimization method includes a plurality of plate thicknesses t _i of the outer panel 4 and the reinforcing member 12, plate thickness ratios Z _i before and after the structure change, and a plurality of differences such that the difference between the approximate expression and the evaluation standard is positive. Under the constraint of the linear form expressed by the equal sign or the inequality formula, the total weight W of the door panel 2 as the objective function is optimized, resulting in a linear programming problem. That is, it is possible to estimate much faster than an estimation method based on nonlinear structure optimization such as the design sensitivity analysis or response surface method.

When applied to a panel structure that requires a particularly high weight as well as high rigidity, such as the door panel 2, the merchantability of the truck is further improved.
The description of one embodiment of the present invention is finished above, but the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, an example in which the truck door panel 2 is used is shown. However, the present invention is not limited to this example. For example, a panel of a bus engine door, a passenger car trunk lid, an engine hood, or the like. It can also be applied to structures, and in this case as well, it is possible to eliminate variations in the panel structure after changing the structure and reduce the number of calculations in order to achieve both rigidity and weight minimization as described above. And has the effect.

It is a schematic diagram explaining the approximate expression of the load-displacement curve by the load sharing rate of this invention. It is a perspective view of the door panel of the truck used for the Example of this invention. It is a figure which shows the load-displacement curve before structure change, a load share rate, and evaluation criteria. It is a figure which shows the range of each plate | board thickness ratio of the outer panel of the said Example, and a reinforcing material. It is a figure explaining the weight ratio after the structure change in the structure optimization of the said Example. It is a load-displacement curve which shows the result of structure optimization in the said Example.

Explanation of symbols

2 Door panel (panel structure)
4 Outer panel (main member)
12 Reinforcement material (reinforcement member)

Claims (3)

In a panel structure having a main member and a reinforcing material,
The strain energy stored in the panel structure is obtained from the load acting on the panel structure based on a non-linear FEM analysis, and the load of the main member and the reinforcing material is determined from the displacement in the acting direction of the strain energy and the load. A step of determining a load sharing ratio with respect to and quantifying the load sharing ratio;
Creating an approximate expression of a load-displacement curve based on the load sharing rate;
And a non-linear structural optimization step that achieves both the rigidity and weight minimization of the panel structure based on the approximate expression and the evaluation criteria for the tension rigidity of the panel structure. A method of arranging a reinforcing material for a structure.   The approximate expression of the load-displacement curve includes the thickness of each of the main member and the reinforcing material as parameters in addition to the load sharing ratio. Installation method.   The panel according to claim 1, wherein the panel structure is a door panel of a truck, the main member is an outer panel, and the reinforcing material is a reinforcing material attached to an inner surface of the outer panel. A method of arranging a reinforcing material for a structure.

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