JP2004132849A - Structural analysis method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable accurate structural analysis of the behavior of a structural body such as a carton box and enhance the accuracy of the structural analysis of the carton box. <P>SOLUTION: When structural analysis of any carton box formed of an anisotropic material is conducted, material test is conducted using the carton box 1 and at the same time numerical analysis is conducted by modeling the material test of the carton box 1. Material test results and numerical analysis results of the carton box 1 are compared and optimized to identify a material characteristic value of carton material. Based on the material characteristic value of the carton material after the identification, structural analysis of the behavior of the carton box 1 is conducted. Since an optimally identified material characteristic value of a carton material can be used, the behavior of the carton box 1 can be accurately analyzed. As a highly accurate material characteristic value is used for structural analysis, the accuracy of the structural analysis can be enhanced. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a structure analysis method suitable for application to a drop impact test analysis process of a cardboard box or the like that protects an electric product inside a package in shipping, transporting and distributing electric products and the like.
[0002]
Specifically, when performing a structural analysis of an arbitrary structure created using an anisotropic member such as a cardboard material, a material test using the structure is performed, and a material test of the structure is modeled. When performing a numerical analysis and comparing and optimizing the material test results and numerical analysis results of this structure to identify the material characteristic values of the anisotropic member, the geometric characteristics of the structure and its material characteristics And the material characteristic value of the anisotropic member can be identified in a mode in which the above is added. In addition, the behavior of the structure can be accurately analyzed, and the accuracy of the structure analysis can be improved.
[0003]
[Prior art]
2. Description of the Related Art Conventionally, many structural analysis methods for analyzing the behavior of a structure including a housing and a plate, such as deformation, have been known. In this structural analysis method, the analysis process differs between a case where the amount of deformation of the structure is large and a case where the amount of deformation is small. This is because when the deformation amount of the structure increases, the relationship between the strain, which is the dimensionless deformation amount, and the stress, which is the load per unit area, is not linear.
[0004]
In this type of structural analysis method, a linear structure analysis method in an elastic region where the relationship between strain and stress is small and deformation is small, and a nonlinear structure analysis method in a plastic region where the relationship between strain and stress is large and deformation is large And divided into Among these structural analysis methods, several analysis methods such as a finite element method, a boundary element method, and a difference method are known, and a combination of these analysis methods is used to analyze the behavior of a structure in a linear region or a nonlinear region. Is performed.
[0005]
Patent Document 1 discloses a “nonlinear structure analysis method”. According to this nonlinear structural analysis method, a material test using a part of the structure is combined with a numerical analysis that models the material test. Thereby, the material constant is identified and the behavior of the structure in the nonlinear region is subjected to the structural analysis.
[0006]
According to this structural analysis method, for example, when manufacturing a case such as a storage battery, the structure of the case is analyzed in advance by the finite element method, and behavior during operation, rigidity, and the like are evaluated. In the finite element method, first, the appearance of a case is set, and the entire case is divided into plane elements on a plate such as a triangle or a quadrangle to obtain a continuum of these plane elements. In the finite element method, an analysis is performed by setting the thickness dimension for each planar element, setting the material according to the boundary conditions such as the load acting on the structure, the longitudinal elastic modulus, the Poisson's ratio, and the like. . This makes it possible to obtain a deformed shape and a deformation amount associated with the analysis of the structure.
[0007]
In order to perform such a structural analysis, material characteristic values such as a longitudinal elastic modulus and a Poisson's ratio of a material constituting the structure are required. These material property values are important and indispensable for analyzing these behaviors and phenomena by numerical calculation, especially in recent years because the need to analyze the behavior of structures has increased and structural analysis has been performed in many cases. It has become. However, since these material characteristic values are greatly influenced by material components, test conditions, manufacturing time, and the like, it is difficult to present them as general values.
[0008]
Patent Document 2 discloses a “stress-strain relationship simulation method”. According to this simulation method, the stress-strain relationship of an arbitrary material is approximated by a composite hardening model, and the back stress is defined by a back stress function having the plastic strain of the material as a variable and the plastic strain coefficient. I do. By using the back stress as a variable, the yield curve of the material is defined as a yield function. By using this yield function, the stress-strain relationship of the material is continuously and numerically analyzed so as to express the Bauschinger effect of the material.
[0009]
[Patent Document 1]
JP-A-09-152392
[Patent Document 2]
JP-A-2000-275154
[0010]
[Problems to be solved by the invention]
By the way, when trying to analyze the structure of a cardboard box using an anisotropic member such as a cardboard member using the conventional structure analysis method, there are the following problems.
[0011]
{Circle around (1)} Even if the nonlinear structural analysis method disclosed in Patent Document 1 is directly applied to a cardboard box using an anisotropic member such as a cardboard member, accurate and accurate structural analysis cannot be performed. In Patent Literature 1, a part of a metal case (structure) to be subjected to nonlinear structural analysis is extracted as a test piece, and a material constant obtained from the test piece is identified. By the way, even if a test piece is made by cutting out a cardboard member and a material test of this cardboard test piece, the material characteristic value of the anisotropic member in the cardboard box cannot be obtained, so the structural analysis in the cardboard box can be performed accurately and accurately. It is difficult to do well.
[0012]
{Circle around (2)} Patent Document 2 deals with isotropic hardening members with respect to materials, so even if the stress-strain relationship simulation method is applied, a great effort is required to obtain material characteristic values of anisotropic members such as cardboard members. Spends time.
[0013]
In view of the above, the present invention has been made to solve such a conventional problem, and enables to accurately analyze the behavior of a structure such as a cardboard material and improve the accuracy of the structure analysis of the structure. It is an object of the present invention to provide a structural analysis method.
[0014]
[Means for Solving the Problems]
The above-described problem is a method of performing a structural analysis of an arbitrary structure created using an anisotropic member, and performing a material test using the structure and modeling the material test of the structure. Perform a numerical analysis, compare and optimize the material test results and the numerical analysis results of the structure to identify the material property values of the anisotropic member, and based on the material property values of the anisotropic member identified here, The problem is solved by a structural analysis method characterized by performing a structural analysis of behavior in a body.
[0015]
According to the structural analysis method of the present invention, when structural analysis is performed on an arbitrary structure created using an anisotropic member, the geometric characteristics of the structure and the material characteristics thereof are added. In this manner, the material characteristic value of the anisotropic member can be identified. For example, as in the case of metal, hardening due to rolling, bending, or the like can be considered, and a material characteristic value with higher accuracy than a generally known material characteristic value can be obtained.
[0016]
Therefore, since the material characteristic value optimally identified with respect to the anisotropic member can be used, it is possible to accurately analyze the behavior in an arbitrary structure created using the anisotropic member. In addition, since a highly accurate material characteristic value can be used for the structural analysis, the accuracy of the structural analysis can be improved.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of a structural analysis method according to the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing a structural example of a cardboard box 1 as an embodiment to which a structural analysis method according to the present invention is applied.
[0018]
In this embodiment, when a structural analysis is performed on an arbitrary structure formed using an anisotropic member such as a cardboard material, a material test using the structure is performed, and a material test of the structure is performed as a model. In order to identify the material characteristic values of the anisotropic member by comparing and optimizing the material test results and numerical analysis results of this structure and performing numerical analysis, the geometrical characteristics of the structure and its material characteristics The material characteristic value of the anisotropic member can be identified in a mode in which the characteristic characteristics are added. In addition, the behavior of the structure can be accurately analyzed, and the accuracy of the structure analysis can be improved.
[0019]
The structural analysis method according to the present invention is a method for structurally analyzing an arbitrary structure created using an anisotropic member. This method is suitable for shipping, transporting, and selling electric products and the like, and applied to a drop impact test analysis process for a cardboard box or the like that protects electronic devices inside a package.
[0020]
The cardboard box 1 for packing electrical products shown in FIG. 1 is an example of a structure, and is a material test sample created using a cardboard member as an example of an anisotropic member. An anisotropic member refers to a member whose physical properties differ depending on the direction. Examples of the anisotropic member include a cardboard member that is a type of paperboard for packaging, a printed wiring board for mounting electronic components, and the like. The printed wiring board is obtained by curing an insulating resin such as a glass fiber woven epoxy resin or a prepreg and forming a wiring pattern of copper foil on both surfaces and / or an intermediate layer.
[0021]
Printed wiring boards are mentioned as anisotropic members because of the recent computerization of equipment, printed wiring boards typified by glass epoxy boards and the like are increasing. In addition, the longitudinal elastic coefficients are different even in the vertical and horizontal directions in the plane from the wiring direction of the wiring pattern or the wiring pattern, and it is difficult to present a general value. This is because it is expected that the need for performing structural analysis on the structure including these will increase.
[0022]
In this example, for the sake of simplicity, the case of the cardboard box 1 will be described with respect to the anisotropic member. The cardboard member is obtained by laminating cardboard on one or both sides of corrugated paper. For example, the corrugated cardboard member has a total thickness of about 3 mm, and has a structure in which corrugated paper called a core is sandwiched between 0.26 mm thick paper on both sides. The corrugated cardboard member has irreversibility that a corrugated cardboard member in a certain original state is changed to another state by applying a force to the corrugated cardboard member, and does not return to the original state even if the force is removed. In this example, the cardboard box 1 used for the linear structure analysis has a rectangular parallelepiped shape, and a space for accommodating electric appliances and the like is formed therein.
[0023]
Here, the length of the cardboard box 1 is L, its width is W, and its height is H. As for the size of the cardboard box 1 as a material test sample, the length L is about 483 mm, the width W is about 383 mm, and the height H is about 283 mm. The cardboard box 1 shown in FIG. 1 has a box body 1f, and an opening 1e for taking in and out articles is provided above the box body 1f. The box body 1f has lids 1a, 1b, 1c, 1d for closing the opening 1e. FIG. 1 shows a state where the lids 1a, 1b, 1c and 1d are opened with respect to the opening 1e of the box body 1f.
[0024]
FIG. 2 is a perspective view showing a configuration example of the cushioning members 2a to 2h when packing the electric product. The cushioning members 2a to 2h shown in FIG. 2 are put into a cardboard box 1 and packed together with electric appliances. The electrical product in the figure has, for example, a rectangular parallelepiped 4 indicated by a two-dot chain line. The cushioning members 2a to 2h are attached to each of the eight corners of the electric product to protect the electric product from an external impact on the cardboard box 1. A thermoformed product such as Styrofoam JQ251 (EPS-40) manufactured by Mitsubishi Chemical Corporation is used for the cushioning members 2a to 2h.
[0025]
As shown in FIG. 2, each of the cushioning members 2a to 2h has a length a of about 80 mm, a width b of about 80 mm, and a height c of about 80 mm. The corners are rounded and formed. Inside each of the cushioning members 2a to 2h, cutouts 3a to 3h of about 40 mm × 40 mm × 40 mm are provided to support the corners of the electric product and to fix it inside the cardboard box 1. In FIG. 2, the notch 3d is not shown.
[0026]
FIG. 3 is an image diagram showing a configuration example of the cardboard box 1 during a material test. At the time of the material test of the cardboard box 1 shown in FIG. 3, a frequency analyzer 70 is used. The frequency analyzer 70 has an acceleration pickup 72 and a hammer 73 for performing a vibration experiment. The vibration test means that the material test sample is vibrated by the hammer 73 and the vibration transmitted from the vibration point is measured by the acceleration pickup 72.
[0027]
In this example, the acceleration pickup 72 is attached to and fixed to a central portion of an arbitrary surface of the cardboard box 1 as a measurement point, and an output cable 72 a extending from the pickup 72 is connected to the analyzer main body 71. The hammer 73 is used when the cardboard box 1 is vibrated (stressed). In this example, a total of 54 points were set as hammer excitation points, nine points for each of the six surfaces constituting the cardboard box 1. Hammer excitation points are indicated by crosses in the figure.
[0028]
The hammer 73 is provided with, for example, an acceleration pickup (not shown) therein. When acceleration is applied to the hammer 73, the acceleration is converted into a voltage and output. The output voltage is 0 V when no acceleration is applied. The acceleration pickup of the hammer 73 is connected to the analyzer main body 71 through a signal cable 73a. This voltage turns on a trigger switch provided in the analyzer main body 71.
[0029]
For example, when the trigger switch is set to 1.0 V as the rising threshold voltage on the frequency analyzer side, acceleration is applied to the hammer 73, and the moment when the voltage transits from a low voltage to a high voltage with a voltage of 1.0 V as a boundary (only once). )), The acquisition of both input and output data is started. The capture time at this time is set in advance to, for example, 300 mmsec, at which data can be captured until the vibration is attenuated and disappears.
[0030]
The acceleration pickup inside the hammer detects a hammer strike and outputs a measurement timing signal to the frequency analyzer 70. The frequency analysis device 70 receives the measurement timing signal from the hammer 73 to detect the arrival time from the time when the cardboard box 1 is vibrated by the hammer 73 to the time when the acceleration pickup 72 measures the vibration. The excitation force applied to the box 1 and its response are measured.
[0031]
In this example, for a total of 54 hammer excitation points set on the cardboard box 1, the frequency transfer function G (jω) from each location to the measurement point is calculated. ω is an angular frequency caused by hammer excitation. G (jω) is obtained based on the output vibration waveform / input vibration waveform. For example, the time history waveform of the measured vibration is converted into a frequency domain, and the frequency is analyzed to clarify the frequency component. This is for obtaining the resonance frequency f0 and the vibration mode of the cardboard box 1.
[0032]
The cardboard box 1 'shown in FIG. 4 has a three-dimensional shape on a simulation when no vibration is given. This is a model of the actual cardboard box 1. This is for the purpose of identifying the material characteristic value of the cardboard member and performing a numerical structure analysis. The lines formed vertically and horizontally are structural analysis lines for analyzing the behavior of the cardboard box 1 ′.
[0033]
FIG. 5 is a perspective view showing an example of a three-dimensional shape of the cardboard box 1 ′ after deformation in simulation. The cardboard box 1 'shown in FIG. 5 has a three-dimensional shape on a simulation when deformed by the vibration mode. In this case, a shock is applied to the cardboard box 1 ′ in the simulation and the behavior thereof is analyzed, so that a structural analysis can be performed assuming a case where a shock is applied to the actual cardboard box 1. In this example, the structural analysis line of the cardboard box 1 'shown in FIG. 5 is swelled on the upper surface and hangs down below the structural analysis line of the cardboard box 1' shown in FIG.
[0034]
FIG. 6 is a perspective view showing a protection example of the rectangular parallelepiped 4 housed in the cardboard box 1. The rectangular parallelepiped 4 shown in FIG. 6 simulates an electric appliance, and is represented by a rigid body in numerical analysis. The size of the rectangular parallelepiped 4 was about 400 mm in length l, about 300 mm in width w, about 200 mm in height h, and 7 kg in weight. The rectangular parallelepiped 4 was divided into eight by a square pillar three-dimensional element. The cushioning members 2a to 2h are arranged at eight corners of the product in the cardboard box 1 so as to fix the product.
[0035]
7A and 7B are perspective views showing an example of the actual appearance of the cardboard box 1 and an example of the appearance of the simulation. The cardboard box 1 shown in FIG. 7A is in a state where the rectangular parallelepiped 4 is inserted and the lid portions 1a and 1c are closed. The lid portions 1b, 1d, etc. are folded in advance inside the opening of the cardboard box 1, and the lid portions 1a, 1c, etc. are closed from above. FIG. 7B shows this state as an example of the appearance of the cardboard box 1 ′ in the simulation. According to the cardboard box 1 'in the simulation shown in FIG. 7B, the appearance is divided by quadrilateral plate elements. This is because, at the time of drop analysis, the impact excitation point is specified by detecting specific position coordinates of a plate element divided into quadrilaterals.
[0036]
FIG. 8 is a graph showing an example of a structural analysis result of the actual cardboard box 1. FIG. 9 is a graph showing an example of a structural analysis result of the cardboard box 1 'on the simulation. In each case, the vertical axis is the gravitational acceleration [G] generated in the rectangular parallelepiped 4, and the horizontal axis is the time [sec] applied to the rectangular parallelepiped 4. A curve I shown in FIG. 8 is a gravitational acceleration change curve generated in the rectangular parallelepiped 4 obtained from an experiment in which the actual cardboard box 1 is freely dropped. As shown in FIG. 8, the maximum gravitational acceleration generated in the rectangular parallelepiped 4 in the actual cardboard box 1 is a maximum G = 51.3G.
[0037]
A curve II shown in FIG. 9 is a gravitational acceleration change curve generated in the rectangular parallelepiped 4 as a result of performing a numerical analysis by applying the cardboard box 1 ′ using the material characteristic values of the identified cardboard members. As shown in FIG. 9, the maximum gravitational acceleration generated in the rectangular parallelepiped 4 in the cardboard box on the simulation was G = 50.7 G at the maximum. The error between the two is about 1.2%.
[0038]
FIG. 10 is a flowchart showing a structural analysis example as an embodiment according to the present invention. FIG. 11 is a flowchart showing an example of a process for identifying the material characteristic value of the cardboard member.
[0039]
In this embodiment, a case is described in which a structural analysis of a cardboard box 1 for packing an electric product made by using a cardboard member is performed, and a material test using the cardboard box 1 is performed, and a material of the cardboard box 1 is used. By modeling the test and performing a numerical analysis, comparing and optimizing the material test results and the numerical analysis results of the cardboard box 1, the material characteristic values of the cardboard member were identified, and the cardboard member identified here was identified. It is assumed that the behavior of the cardboard box 1 is structurally analyzed based on the material characteristic values. The numerical analysis assumes a case where a numerical analysis system is constructed and processed on a computer such as a computer.
[0040]
Under these structural analysis conditions, a cardboard box 1 is prepared as a material test sample in step A1 of the flowchart shown in FIG. In this example, as shown in FIG. 1, the cardboard box 1 is formed using a cardboard member having a total thickness of about 3 mm, which is an example of an anisotropic member. As for the size of the cardboard box 1 as a material test sample, the length L is about 483 mm, the width W is about 383 mm, and the height H is about 283 mm.
[0041]
Next, the process proceeds to step A2 to execute a material test using the cardboard box 1. For example, a vibration test of the cardboard box 1 as an example of a material test is performed. Of course, the cardboard box 1 is in a state where the opening 1e of the box body 1f is closed by the lids 1a, 1b, 1c, 1d. In this vibration test, the vibration mode and the resonance frequency are measured using the frequency analyzer 70 shown in FIG. In this example, as shown in FIG. 3, an acceleration pickup 72 is attached and fixed to the center of an arbitrary surface of the cardboard box 1 as a measurement point in the vibration test. An output cable 72a from the acceleration pickup 72 and a signal cable 73a reaching the hammer 73 are connected to the frequency analyzer 70.
[0042]
In this vibration experiment, the material test sample is vibrated by the hammer 73, and the vibration transmitted from the vibration point by the acceleration pickup 72 is measured. In this example, a total of 54 points were set as hammer excitation points, nine points for each of the six surfaces constituting the cardboard box 1. With respect to a total of 54 hammer excitation points set in the cardboard box 1, transfer functions from each location to the measurement point are calculated. This is for obtaining the resonance frequency and the vibration mode of the cardboard box 1. The resonance frequency and the vibration mode constitute measurement values during a material test of the actual cardboard box 1.
[0043]
For example, when the hammer 73 is hit at a preset hammer excitation point, the acceleration pickup inside the hammer 73 detects the hit and generates a voltage, and a measurement timing signal based on this voltage is output to the frequency analyzer 70. The frequency analyzer 70 receives the measurement timing signal from the hammer 73 and detects the arrival time from the time when the cardboard box 1 is vibrated by the hammer 73 to the time when the acceleration pickup 72 measures the vibration. Further, the vibration applied to the cardboard box 1 is measured. Measurement values such as arrival time and frequency are obtained for these 54 hammer excitation points in total.
[0044]
Then, the process proceeds to step A3 to identify the material characteristic value of the cardboard member. At this time, the material test of the cardboard box 1 is modeled and numerically analyzed. At the time of this numerical analysis, a linear structure analysis taking into account the geometric rigidity and material rigidity of the cardboard box 1 is applied.
[0045]
In the process of identifying the material characteristic value of the cardboard member, for example, the process shifts to a flowchart (subroutine) shown in FIG. 11 to identify the material characteristic value through seven steps of Step B2 to Step B8. This is because the material test result and the numerical analysis result of the cardboard box 1 are compared and optimized to identify the material characteristic value of the cardboard member. In this example, a closed loop from the creation of the input data in step B2 to the updating of the material property values in step B8 is constructed, and the repetitive calculation is performed by the optimization algorithm in step B7. As a result, material characteristic values such as a modulus of longitudinal elasticity and a Poisson's ratio are identified.
[0046]
For this purpose, first, in step B1 of the subroutine, the computer is started to initialize the numerical analysis system. The numerical analysis system is application software built on a computer.
[0047]
In this system initialization, initialization is performed to identify the material characteristic value of the cardboard member. For example, the history of the resonance frequency and the vibration mode, which are the measured values obtained in the material test in step A2 described above, the selection of the optimization method, the longitudinal elastic modulus of the cardboard member, the initial value of the Poisson's ratio and the constraints, etc. Was recorded in a file on the computer.
[0048]
Then, the process proceeds to step B2 to create input data necessary for the process of identifying the material characteristic value of the cardboard member. This input data is used to simulate (simulate) a vibration experiment of the cardboard box 1 on a computer, and the geometrical shape data of the cardboard box 1 which is a material test sample this time and the material characteristics of the cardboard member are used. It is composed of values. As the material property values used in the first calculation, an appropriate value of the longitudinal elastic modulus and the Poisson's ratio, which are initially set in step B1, are given as initial values. In the second and subsequent iterations, the optimized material property values are used.
[0049]
Then, in step B3, a linear structure analysis (eigenvalue analysis) of the cardboard box 1 is performed on the computer. In this linear structure analysis, calculation is performed in consideration of the anisotropic material characteristics of the cardboard member. For example, in this linear structure analysis, a vibration experiment of the cardboard box 1 is simulated, and behavior analysis in the linear region is performed. By performing this behavior analysis, a numerical analysis result value in a vibration experiment of the cardboard box 1 in the simulation can be obtained. This numerical analysis result value includes the resonance frequency and the vibration mode in the vibration experiment of the cardboard box 1 in the simulation. The resonance frequency is obtained from the transfer function, and the vibration mode is obtained as a three-dimensional numerical analysis value as shown in FIGS.
[0050]
Thereafter, the numerical analysis result value obtained by the previous simulation is output to a temporary storage memory or the like in step B4. This numerical analysis result value is output as a resonance frequency and a vibration mode which constitute the actual measurement result value of the cardboard box 1 during the material test. This is for identifying the resonance frequency and the vibration mode obtained from the actual vibration test of the cardboard box 1.
[0051]
Then, in order to identify a measurement result value obtained from an actual vibration test of the cardboard box 1 as a numerical analysis result value, the process proceeds to step B5 to calculate an evaluation function. In the calculation of this evaluation function, the material test result of the cardboard box 1 and the numerical analysis result are compared. For example, the resonance frequency value of the numerical analysis result value obtained in step B4 is compared with the resonance frequency value of the measurement result value obtained in the material test in step A2.
[0052]
This is for identifying the material characteristic value of the cardboard member as input data so that the numerical analysis result value approaches the measurement result value. Specifically, a deviation between the resonance frequency value of the numerical analysis result value and the resonance frequency value of the measurement result value at the time of the material test is obtained and used as an evaluation function.
[0053]
Then, in order to identify the material characteristic value of the cardboard member, the process proceeds to step B6, and the convergence determination of the evaluation function is executed. In this process, it is determined whether or not the value of the evaluation function obtained in step B5 is within an allowable range. For example, when the value of the evaluation function is not within the allowable range and the value of the evaluation function has not converged, the process proceeds to step B7.
[0054]
In step B7, the material characteristic value of the cardboard member is optimized. At this time, a non-linear programming method in mathematical programming is selected as a result of the convergence determination in step B6, and an optimization program based on this non-linear programming method is applied. Then, the process proceeds to step B8 to update the material property value of the cardboard member. In this way, it is possible to significantly reduce the time and labor required for identifying the material characteristic values.
[0055]
Thereafter, the process returns to step B2. The identification operation from the creation of the input data in step B2 to the update of the material property values in step B8 is repeated until the value of the evaluation function converges. In other words, in the material characteristic value identification processing in this example, the input data generation in step B2 is performed through the convergence determination processing in step B6, the material characteristic value optimization processing in step B7, and the material characteristic value update processing in step B8. The calculation is repeatedly performed to the processing.
[0056]
If the value of the evaluation function converges and falls within the allowable range in step B6 described above, the process proceeds to step B9. In step B9, the identification processing result is output to a database or the like. For example, the material property values of the identified corrugated cardboard members are stored in a computer file, and the material property value optimization loop ends.
[0057]
Then, the process returns to step A3 of the flowchart shown in FIG. Thereafter, the process proceeds to step A4, where input data necessary for the structural analysis of the cardboard box 1 is created. The input data necessary for this structural analysis is created by reading the material characteristic values of the previously identified cardboard member from the file.
[0058]
Then, the behavior of the cardboard box 1 is structurally analyzed in step A5 based on the material property values of the identified cardboard members. In this example, a rectangular parallelepiped 4 simulating the electric product shown in FIG. 6 and eight cushioning members were put in the cardboard box 1 shown in FIG. 7A, and a drop analysis was performed.
[0059]
Each of the cushioning members 2 a to 2 h is arranged so as to be attached to each of the eight corners of the rectangular parallelepiped 4 in the cardboard box 1 to fix the rectangular parallelepiped 4. Of course, the cardboard box 1 in the simulation uses the material property values of the identified cardboard members. The purpose of this drop analysis is to grasp the maximum gravitational acceleration (maximum G) generated in the rectangular parallelepiped 4 (simulated electric product) packed in the cardboard box 1. Specifically, an experiment was conducted in which the rectangular parallelepiped 4 was packed in the cardboard box 1 and the cardboard box 1 was freely dropped on a concrete floor in a horizontal state from a height of 60 cm.
[0060]
According to the output of the structural analysis result in step A6, the maximum gravitational acceleration generated in the rectangular parallelepiped 4 obtained from the experiment based on the actual free fall was G = 51.3G as shown in FIG. On the other hand, as a result of performing a numerical analysis using the cardboard box 1 using the material characteristic values of the identified cardboard members, the maximum gravitational acceleration generated in the rectangular parallelepiped 4 was, as shown in FIG. 7G. A structural analysis result having an error of about 1.2% between the two could be output. This is because the reliability of the material property value of the identified cardboard member is high.
[0061]
The structural analysis results such as the maximum G in these experiments and the maximum G in the numerical analysis are stored in a database or the like as structural analysis result data. Based on the result of the structural analysis, the behavior of the cardboard box 1 having an arbitrary size in the linear region is simulated, and when an impact force is applied to any part of the cardboard box 1, the impact force is applied to any part of the rectangular parallelepiped 4. This is to simulate whether to concentrate.
[0062]
As described above, according to the structural analysis method as an embodiment of the present invention, when performing a structural analysis of a cardboard box 1 for packing an electric product created using a cardboard member, the geometrical analysis of the cardboard box 1 is performed. The material characteristic value of the cardboard member can be identified in a mode in which the characteristic and the material characteristic are added.
[0063]
Therefore, since the material characteristic value optimally identified for the cardboard member can be used, the behavior in the cardboard box 1 can be accurately analyzed. In addition, since a highly accurate material characteristic value can be used for the structural analysis of the cardboard box 1, the accuracy of the structural analysis of the cardboard box 1 can be improved.
[0064]
In addition, the identification processing of the material characteristic value of the anisotropic member according to the structural analysis method according to the present invention can also consider hardening such as rolling or bending like a metal, and is based on a generally known material characteristic value. It is also possible to obtain highly accurate material characteristic values. In addition, according to the method for identifying material property values of anisotropic members, the optimization program used for nonlinear programming is applied for numerical analysis, so that the time and effort required to identify material property values are reduced. Significant reduction can be achieved.
[0065]
In this example, the case of the cardboard box 1 using an anisotropic member for the structure has been described. However, the present invention is not limited to this. The present invention can also be applied to substrate structure analysis.
[0066]
【The invention's effect】
As described above, according to the structural analysis method of the present invention, when performing a structural analysis of an arbitrary structure created using an anisotropic member, a material test using this structure is performed, The material test of the structure is modeled and subjected to numerical analysis, and the material test result and the numerical analysis result of the structure are compared and optimized to identify the material characteristic value of the anisotropic member.
[0067]
With this configuration, the material property value of the anisotropic member can be identified in a mode in which the geometric property of the structure and the material property thereof are added. Therefore, since the material characteristic value optimally identified with respect to the anisotropic member can be used, it is possible to accurately analyze the behavior in an arbitrary structure created using the anisotropic member. In addition, since a highly accurate material characteristic value can be used for the structural analysis, the accuracy of the structural analysis can be improved.
[0068]
INDUSTRIAL APPLICABILITY The present invention is extremely suitable to be applied to a drop impact test analysis process of a cardboard box or the like for protecting an electric product in a package in shipping, transporting and distributing the electric product.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a structural example of a cardboard box 1 as an embodiment to which a structural analysis method according to the present invention is applied.
FIG. 2 is a perspective view showing a configuration example of cushioning members 2a to 2h when packing an electric product.
FIG. 3 is an image diagram showing a configuration example of a cardboard box 1 during a material test.
FIG. 4 is a perspective view showing an example of a three-dimensional shape of a cardboard box 1 ′ before deformation in a simulation.
FIG. 5 is a perspective view showing an example of a three-dimensional shape of a cardboard box 1 ′ after deformation in simulation.
6 is a perspective view showing an example of protection of the rectangular parallelepiped 4 housed in the cardboard box 1. FIG.
FIGS. 7A and 7B are perspective views showing an example of an actual appearance of the cardboard box 1 and an example of an appearance of a simulation thereof.
FIG. 8 is a graph showing an example of a structural analysis result of an actual cardboard box 1;
FIG. 9 is a graph showing an example of a structural analysis result of the cardboard box 1 ′ on the simulation.
FIG. 10 is a flowchart showing a structural analysis example of the cardboard box 1 as an embodiment according to the present invention.
FIG. 11 is a flowchart illustrating an example of a process of identifying a material characteristic value of the cardboard member.
[Explanation of symbols]
1, 1 ': cardboard box (structure), 2a to 2h: buffer member, 3a to 3h: cutout, 4: rectangular parallelepiped (electric product), 70: frequency analyzer , 71: Analytical device main body, 72: Acceleration pickup, 73: Hammer

Claims (5)

A method for performing a structural analysis of an arbitrary structure created using an anisotropic member,
Along with conducting a material test using the structure, the material test of the structure was modeled and numerically analyzed.
Identify the material property value of the anisotropic member by comparing and optimizing the material test results and numerical analysis results of the structure,
A structural analysis method characterized by performing a structural analysis of a behavior in the structural body based on a material characteristic value of the identified anisotropic member. In a material test using the structure,
The structural analysis method according to claim 1, wherein the vibration mode and the resonance frequency are measured by exciting the structure. When modeling and numerically analyzing the material test of the structure,
The structural analysis method according to claim 1, wherein a structural analysis in consideration of a geometric rigidity and a material rigidity of the structure is applied. When identifying the material property value of the anisotropic member,
Compare the material test results and numerical analysis results of the structure to determine convergence,
The structural analysis method according to claim 1, wherein an optimization program based on a non-linear programming is applied to a result of the convergence determination to update a material characteristic value of the anisotropic member. In the case where the identification process of the material property value of the anisotropic member is performed by a computer,
Starting the computer and initializing the numerical analysis system;
The history of the resonance frequency and the vibration mode, which are the measured values obtained in the material test, the selection of the optimization method, the longitudinal elastic modulus of the anisotropic member, the initial value of the Poisson's ratio and the constraints, The process of recording in the file,
A process of creating input data necessary for the identification process of the material property values of the anisotropic member,
A step of analyzing the structure of the structure on the computer;
A process of obtaining an evaluation function for identifying a numerical analysis result value obtained by a simulation in the computer and a measurement result value obtained from a vibration experiment of an actual structure as a numerical analysis result value,
A step of determining whether the value of the evaluation function is within an allowable range,
A step of optimizing the material property value of the determined anisotropic member,
2. The method according to claim 1, further comprising the step of updating the optimized material property value of the anisotropic member.

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