Patent Description:
In recent years, weight reduction of full vehicles arising from environmental problems has been advanced, in particular in the automotive industry, and analysis by computer aided engineering (hereinafter, referred to as "CAE (computer aided engineering) analysis") has become an indispensable technique for designing automotive bodies. This CAE analysis has been known to achieve improvement of stiffness and weight reduction by using an optimization technique, such as mathematical optimization, sheet thickness optimization, shape optimization, or topology optimization. For example, the optimization technique of the CAE analysis is often used in structural optimization of castings, such as engine blocks. Of those optimization techniques of the CAE analysis, topology optimization, in particular, has started to attract attention.

Topology optimization is a method of providing a design space of a certain size, fitting three-dimensional elements in the design space, and leaving a minimum necessary portion of the three-dimensional elements satisfying given conditions, to thereby obtain an optimum shape satisfying the conditions. Therefore, for topology optimization, a method of directly constraining the three- dimensional elements forming the design space and directly adding a load thereon is used. As a technique related to such topology optimization, a method for topology optimization of a component of a complex structural body is disclosed in <CIT>.

Further, <CIT> describes a design optimization system for complex product design.

Structural bodies of automobiles and the like are configured by using mainly thin sheets, and when a portion of an automotive body formed of such a thin sheet is optimized, it is difficult to cause that portion to be independent as a design space and to reflect a load and a constrained state in that design space. Thus, there has been a problem that it is difficult to apply an optimization technique to a part of a structural body. Further, there has also been a problem of how to reflect an optimized shape in a thin sheet structure appropriately even if the optimized shape is found with three-dimensional elements.

The technique disclosed in <CIT> relates to a method of using mathematical operations and to a physical system for analysis, and does not provide any means for solving the above mentioned problems. In recent years, development of a technique for solving the above mentioned problems has been desired.

The present invention has been made in order to solve the above mentioned problems, and aims to provide a technique that enables application of an optimization technique to a part of a structural body that receives external force and that contributes to optimization of the structural body.

To solve the above-described problem and achieve the object, a method for analysis of shape optimization according to the present invention is a computer-implemented method according to the appended method claims for optimizing a part of a structural body model including a movable portion, by using two-dimensional elements or three-dimensional elements, and the method includes: a design space setting step of setting, as a design space, a portion to be optimized in the movable portion; an optimization block model generating step of generating, in the set design space, an optimization block model that is formed of three-dimensional elements and is to be subjected to analysis processing of optimization; a connection processing step of connecting the generated optimization block model with the structural body model; a material property setting step of setting a material property for the optimization block model; an optimization analysis condition setting step of setting an optimization analysis condition for finding an optimum shape of the optimization block model; a multi-body dynamics analysis condition setting step of setting a multi-body dynamics analysis condition for performing multi-body dynamics analysis on the structural body model with which the optimization block model has been connected; and an optimum shape analyzing step of executing, based on the set optimization analysis condition and multi-body dynamics analysis condition, the multi-body dynamics analysis on the optimization block model and finding the optimum shape of the optimization block model.

Moreover, in the above-described invention, in the multi-body dynamics analysis condition setting step, a load or displacement that is obtained as a result of performing multi-body dynamics analysis on the structural body model beforehand is set.

Moreover, in the above-described invention, in the material property setting step, at a time a part where the optimization block model has been connected in the structural body model is formed of two-dimensional elements, a Young's modulus in the three-dimensional elements of the optimization block model is set lower than a Young's modulus in the two-dimensional elements.

Moreover, in the above-described method for analysis of shape optimization according to the present invention, the three-dimensional elements forming the optimization block model are each formed of a three-dimensional element that is a polyhedron having five to eight sides and that has at least one pair of sides parallel to each other.

Moreover, in the above-described invention, in the optimization block model generating step, the optimization block model, which is along a peripheral surface where the design space has been set in the structural body model, and in which the three-dimensional elements are subdivided in parallel with a surface having a maximum area of the design space, is generated.

Moreover, in the above-described invention, the optimization block model is generated by: setting nodes in a portion connected with the two-dimensional elements or three-dimensional elements forming the structural body model; using, as the three-dimensional elements forming the optimization block model, hexahedral three-dimensional elements; and stacking the three-dimensional elements along a surface including the nodes set in the connected portion.

Moreover, in the above-described invention, the optimization block model is formed of a plurality of block bodies formed of three-dimensional elements, and is formed by connecting the plurality of block bodies by using a rigid body element, a beam element, or a two-dimensional element.

Moreover, in the above-described method for analysis of shape optimization according to the present invention, discretization is performed with an optimization parameter in optimization calculation by numerical analysis.

Moreover, a device for analysis of shape optimization according to the present invention is a device for analysis of shape optimization for optimizing a part of a structural body model having a movable portion, by using two-dimensional elements or three-dimensional elements, and the device includes: a design space setting unit that sets, as a design space, a portion to be optimized in the movable portion; an optimization block model generating unit that generates, in the set design space, an optimization block model that is formed of three-dimensional elements and is subjected to analysis processing of optimization; a connection processing unit that connects the generated optimization block model with the structural body model; a material property setting unit that sets a material property for the optimization block model; an optimization analysis condition setting unit that sets an optimization analysis condition for finding an optimum shape of the optimization block model; a multi-body dynamics analysis condition setting unit that sets a multi-body dynamics analysis condition for performing multi-body dynamics analysis on the structural body model with which the optimization block model has been connected; and an optimum shape analyzing unit that executes, based on the set optimization analysis condition and multi-body dynamics analysis condition, the multi-body dynamics analysis on the optimization block model and finds the optimum shape of the optimization block model.

Moreover, in the above-described invention, the multi-body dynamics analysis condition setting unit sets a load or displacement that is obtained as a result of performing multi-body dynamics analysis on the structural body model beforehand.

Moreover, in the above-described invention, at a time a part where the optimization block model has been connected in the structural body model is formed of two-dimensional elements, the material property setting unit sets a Young's modulus in the three-dimensional elements of the optimization block model lower than a Young's modulus in the two-dimensional elements.

Moreover, in the above-described device for analysis of shape optimization according to the present invention, the three-dimensional elements forming the optimization block model are each formed of a three-dimensional element that is a polyhedron having five to eight sides and that has at least one pair of sides parallel to each other.

Moreover, in the above-described invention, the optimization block model generating unit generates the optimization block model, which is along a peripheral surface where the design space has been set in the structural body model, and in which the three-dimensional elements are subdivided in parallel with a surface having a maximum area of the design space.

Moreover, in the above-described invention, the optimization block model generating unit performs the generation by: setting nodes in a portion connected with the two-dimensional elements or three-dimensional elements forming the structural body model; using, as the three-dimensional elements forming the optimization block model, hexahedral three-dimensional elements; and stacking the three-dimensional elements along a surface including the nodes set in the connected portion.

Moreover, in the above-described invention, the optimization block model generating unit forms the optimization block model with a plurality of blocks formed of three-dimensional elements, and generates the optimization block model by connecting the plurality of blocks by using a rigid body element, a beam element, or a two-dimensional element.

Moreover, in the above-described invention, the optimum shape analyzing unit performs discretization with an optimization parameter in optimization calculation by numerical analysis.

Moreover, in the above-described invention, the optimum shape analyzing unit performs optimization calculation by topology optimization.

The present invention achieves an effect of enabling application of an optimization technique to a part of a structural body, which receives external force, achieving optimization of the structural body, such as an automotive body, and thereby realizing weight reduction of the structural body while improving stiffness and crash worthiness in a movable portion of the structural body.

Hereinafter, preferred embodiments of a method and a device for analysis of shape optimization according to the present invention will be described in detail, based on the drawings. The present invention is not limited by these embodiments.

A device for analysis of shape optimization <NUM> according to this first embodiment is a device in which a computer optimizes, according to an instruction of an operator, a portion of a structural body model having a movable part, by using two-dimensional elements and three-dimensional elements as appropriate. Specifically, the device for analysis of shape optimization <NUM> according to this first embodiment is a device that performs optimization calculation by numerical analysis of a shape of a part of a structural body model <NUM> (see <FIG>) formed by using two-dimensional elements, of which an example is illustrated in <FIG>, or two-dimensional elements and three-dimensional elements. This device for analysis of shape optimization <NUM> is, as illustrated in <FIG>, configured of a personal computer (PC), and has a display device <NUM>, an input device <NUM>, a memory storage <NUM>, a working data memory <NUM>, and an arithmetic processing unit <NUM>. Further, the display device <NUM>, the input device <NUM>, the memory storage <NUM>, and the working data memory <NUM> are connected to the arithmetic processing unit <NUM>. The display device <NUM>, the input device <NUM>, the memory storage <NUM>, and the working data memory <NUM> respectively perform functions according to commands of the arithmetic processing unit <NUM>.

The display device <NUM> is used in display of results of calculation and the like, and is configured of a liquid crystal monitor, or the like.

The input device <NUM> is used in instruction for display of a structural body model file, input of conditions by the operator, and the like, and is configured of a key board, a mouse, and the like.

In the memory storage <NUM>, various pieces of information, such as a file of the structural body model <NUM> exemplified in <FIG>, are stored. The structural body model <NUM> may be formed of only two-dimensional elements, or may be formed of a combination of two-dimensional elements and three-dimensional elements. For example, in an example of a door <NUM> of an automobile as illustrated in <FIG> as an example of the structural body model <NUM>, an outer part 14a forming the automobile's outer side of the door <NUM> is formed mainly of a steel sheet and thus the structural body model <NUM> is formed of two-dimensional elements. Further, if the structural body model <NUM> is a block body formed of a casting, such as an engine, for example, the structural body model <NUM> is formed of three-dimensional elements.

The working data memory <NUM> has, inside thereof, a data storage area 9a storing therein results of calculation, and a working area 9b for performing calculation processing.

The arithmetic processing unit <NUM> is configured of a central processing unit (CPU) of a computer, such as a personal computer (PC). Each unit of the arithmetic processing unit <NUM> described below is realized by the CPU of the PC executing a predetermined program. The arithmetic processing unit <NUM> includes: a design space setting unit <NUM> that sets, as a design space, a portion to be optimized in a movable portion; an optimization block model generating unit <NUM> that generates, in the set design space, an optimization block model <NUM> (see <FIG> and the like), which is formed of three-dimensional elements and is to be subjected to analysis processing of optimization; a connection processing unit <NUM> that connects the generated optimization block model <NUM> with the structural body model <NUM>; a material property setting unit <NUM> that sets a material property for the optimization block model <NUM>; an optimization analysis condition setting unit <NUM> that sets a condition (referred to as "optimization analysis condition") for finding an optimum shape for the optimization block model <NUM>; a multi-body dynamics analysis condition setting unit <NUM> that sets a condition (referred to as "multi-body dynamics analysis condition") for performing multi-body dynamics analysis on the structural body model <NUM> (see <FIG>) connected with the optimization block model <NUM>; and an optimum shape analyzing unit <NUM> that executes, based on the set optimization analysis condition and multi-body dynamics analysis condition, multi-body dynamics analysis on the optimization block model <NUM> and finds an optimum shape of the optimization block model <NUM>.

A configuration of each of the units of the arithmetic processing unit <NUM> will be described in detail. In the description, the structural body model <NUM>, which is formed of a door frame <NUM> (see <FIG>) and the door <NUM> (see <FIG> and <FIG>) at a front left side of an automotive body (not illustrated), will be exemplified. Further, the door <NUM> is also a movable portion of the structural body model <NUM>.

<FIG> is an explanatory diagram of the movable portion of the structural body model according to the first embodiment of the present invention. <FIG> illustrates a perspective view of the door <NUM>, which is an example of the movable portion of this structural body model <NUM> from the automobile's inner side. As illustrated in <FIG>, the door <NUM> has the outer part 14a, which is provided on the automobile's outer side and is sheet-like, and an inner part 14b, which is provided on the automobile's inner side. Further, the door <NUM> has: a reinforcement part (not illustrated), which is provided between the outer part 14a and inner part 14b and reinforces the door <NUM>; and a hinge portion 14d (see <FIG>), which is provided on a lateral surface of a front side of the automotive body and is for coupling the door <NUM> to the door frame <NUM>.

The door <NUM> is rotatably attached to the door frame <NUM> with the hinge portion 14d and pivots about the hinge portion 14d as illustrated by state A1 to state A4 of <FIG>. In this way, the door <NUM> is opened and closed. <FIG> is a diagram illustrating an operation of closing the door <NUM>. In <FIG>, the state A1 illustrates an open state of the door <NUM>. The state A2 and state A3 illustrate a process of the door <NUM> being brought from the open state into a closed state. The state A4 illustrates the closed state of the door <NUM>. If the door <NUM> is closed with great force, the outer part 14a may be deformed due to a centrifugal force, a reaction force upon the closure of the door <NUM>, or the like. Thus, in this example, investigation is made on optimizing a shape of the inner part 14b to minimize the deformation of the outer part 14a upon the closure of the door <NUM> while achieving weight reduction of the door <NUM>.

The design space setting unit <NUM> sets, as a design space <NUM>, a portion to be optimized, in a portion of the movable portion of the structural body model <NUM>. In this first embodiment, the design space setting unit <NUM> has set, as the design space <NUM>, a portion of the door <NUM> illustrated in <FIG>, other than the outer part 14a. <FIG> are diagrams illustrating a method for analysis of optimization of the door <NUM>, which is an example of the movable portion of the structural body model according to the first embodiment of the present invention. <FIG> is a diagram illustrating a process of setting a design space in a method for analysis of shape optimization according to the first embodiment of the present invention. <FIG> is a diagram illustrating a process of generating an optimization block model in the method for analysis of shape optimization according to the first embodiment of the present invention. <FIG> is a diagram illustrating a process of connecting the optimization block model in the method for analysis of shape optimization according to the first embodiment of the present invention. When the design space <NUM> is set in a part of the movable portion of the structural body model <NUM> by the design space setting unit <NUM>, as illustrated in <FIG>, the inner part 14b (<FIG>), which is a part of the structural body model <NUM> in that part, is deleted, and the deleted part becomes the design space <NUM>. <FIG> illustrates a state with only the outer part 14a.

The above described example corresponds to a case where the design space setting unit <NUM> sets the design space <NUM> by deleting a part of the structural body model <NUM>, but the device for analysis of shape optimization <NUM> may be configured to set the design space <NUM> beforehand upon generation of the structural body model <NUM>. If the design space <NUM> is set beforehand upon generation of the structural body model <NUM>, a generating unit itself that generates the structural body model <NUM> serves also as the design space setting unit <NUM>. That is, the design space setting unit <NUM> according to the present invention may have both of the above described function of setting a design space and function of generating a structural body model.

The optimization block model generating unit <NUM> generates the optimization block model <NUM> for performing analysis processing of optimization on the set design space <NUM>. Upon the generation, the optimization block model generating unit <NUM> may generate the optimization block model <NUM> in any shape of a size that fits in the set design space <NUM>. <FIG>, and <FIG> illustrate an example in which the optimization block model <NUM> has been generated in the design space <NUM>. <FIG> and <FIG> are explanatory diagrams illustrating elements inside the optimization block model according to the first embodiment of the present invention. <FIG> illustrates a state where the optimization block model <NUM> illustrated in <FIG> is viewed from a direction of a thick arrow in <FIG>. <FIG> is an enlarged view of inside of the optimization block model <NUM> illustrated in <FIG> at its front-back direction central portion.

Further, the optimization block model generating unit <NUM> forms the optimization block model <NUM> with three-dimensional elements. Upon the formation, the optimization block model generating unit <NUM> preferably forms the three-dimensional elements each with a three-dimensional element, which is a polyhedron having five sides or more and eight sides or less and which has at least one pair of sides parallel to each other. Reasons for this are as follows. If a part formed in the design space <NUM> is formed of a thin sheet like a part of an automotive body, an optimum shape of the optimization block model <NUM> is desirably calculated to be reflected in a structural body shape of the thin sheet, by executing calculation of optimization using the optimization block model <NUM>. In this respect, by forming the optimization block model <NUM> by using the three-dimensional elements, which are polyhedrons each having five sides or more and eight sides or less and which have at least one pair of sides parallel to each other, such a demand becomes easier to be satisfied. Further, accuracy of optimization is preferably increased by setting, as the three-dimensional elements of polyhedrons each having five sides or more forming the optimization block model <NUM>, three-dimensional elements of a uniform size. In this first embodiment, as illustrated in <FIG>, the whole optimization block model <NUM> is formed of hexahedral elements.

Further, the optimization block model generating unit <NUM> preferably generates the optimization block model <NUM>, along a peripheral surface where the design space <NUM> has been set in the structural body, and such that the three-dimensional elements are subdivided in parallel with a surface having the maximum area of the design space <NUM>. For example, as illustrated in <FIG>, if the inner part 14b in the door <NUM> is set as the design space <NUM>, as illustrated in <FIG>, a surface of this optimization block model <NUM> on the automobile's outer side has the maximum area. The optimization block model generating unit <NUM> generates the optimization block model <NUM> such that the surface on the automobile's outer side, which has this maximum area, becomes parallel to a lateral surface of the automotive body.

Reasons for generating the optimization block model <NUM> as described above are as follows. Since the inner part 14b is formed of a sheet, for example, a calculation result in which the three-dimensional elements of the optimization block model <NUM> remain in a two-dimensional shape is desirably obtained when calculation of optimization is executed by using the optimization block model <NUM>. By adopting the above described model configuration for the optimization block model <NUM>, possibility of this result of calculation remaining in a two-dimensional shape is increased and thus utility value for practical use is increased.

The connection processing unit <NUM> performs processing for connecting the generated optimization block model <NUM> with the structural body model <NUM> (outer part 14a and hinge portion 14d). In this processing for connecting the optimization block model <NUM> and structural body model <NUM> together, a rigid body element, a sheet element, or a beam element is used. In order to accurately transmit a load between the optimization block model <NUM> and outer part 14a, the connection processing unit <NUM> preferably performs connection processing such that the original connection between the part deleted as the design space <NUM> and the outer part 14a is reflected in a connected position between the optimization block model <NUM> and outer part 14a. <FIG> is an explanatory diagram illustrating a connected position of the optimization block model according to the first embodiment of the present invention. <FIG> illustrates, as an example of the connected position of the optimization block model <NUM>, a connected portion <NUM> between a surface of the outer part 14a on the automobile's inner side and the optimization block model <NUM> illustrated in <FIG> and the like. The connection processing unit <NUM> has connected the outer part 14a with the optimization block model <NUM> at the connected portion <NUM> illustrated in <FIG> with their surfaces. As a result, an optimum shape of the inner part 14b illustrated in <FIG> and the like and an optimum connection between the outer part 14a and inner part 14b are able to be analyzed. <FIG> is an explanatory diagram illustrating another example of a connected position of the optimization block model according to the first embodiment of the present invention. <FIG> illustrates, as another example of a connected position of the optimization block model <NUM>, a connected portion between the optimization block model <NUM> and hinge portion 14d. In this first embodiment, the hinge portion 14d is, as illustrated in <FIG>, formed of two-dimensional elements. The connection processing unit <NUM> has connected the optimization block model <NUM> and hinge portion 14d as illustrated in <FIG>.

The material property setting unit <NUM> sets, for the optimization block model <NUM>, material properties, such as a Young's modulus, a specific gravity, a yield strength, and a tensile strength. Three-dimensional elements are more difficult to be deformed than two-dimensional elements. Thus, if a model to be analyzed is formed by connecting three-dimensional elements and two-dimensional elements together, a part formed of the two-dimensional elements may be largely deformed, leading to a result of analysis different from the actual state. For example, if a connected part between the optimization block model <NUM> and structural body model <NUM> is formed of two-dimensional elements, when a load is applied to the optimization block model <NUM>, the position of the connected part is deformed more largely than the optimization block model <NUM>, contrary to the actual state. In order to solve such a problem, if the part where the optimization block model <NUM> is connected to in the structural body model <NUM> is formed of two-dimensional elements as described above, the material property setting unit <NUM> sets Young's modulus of the three-dimensional elements of the optimization block model <NUM> lower than (for example, to be equal to or less than a half of) a Young's modulus of the two-dimensional elements. As a result, analysis that has no bias in deformation and that is well-balanced is able to be performed.

The optimization analysis condition setting unit <NUM> sets an optimization analysis condition for finding an optimum shape of the optimization block model <NUM>. There are two types of the optimization analysis conditions set by this optimization analysis condition setting unit <NUM>, which are objective conditions and constraint conditions. The objective condition is a condition set according to an object of the structural body model <NUM>. Examples of this objective condition include, minimizing displacement, minimizing strain energy, minimizing generated stress, maximizing absorbed energy, and the like. The optimization analysis condition setting unit <NUM> sets only one objective condition for the optimization block model <NUM>. The constraint condition is a constraint imposed upon optimization analysis. Examples of the constraint condition include a material volume fraction, which is a volume ratio of a volume of the optimization block model <NUM> after optimization to a volume of the optimization block model <NUM> before the optimization, displacement of an arbitrary portion, a generated stress, and the like. The optimization analysis condition setting unit <NUM> is able to set a plurality of constraint conditions for the optimization block model <NUM>.

The multi-body dynamics analysis condition setting unit <NUM> sets a multi-body dynamics analysis condition for performing multi-body dynamics analysis on the structural body model <NUM> that has been connected with the optimization block model <NUM>. When a deformation of the outer part 14a in an operation of closing the door <NUM> is analyzed, for example, the multi-body dynamics analysis condition setting unit <NUM> rotatably sets the door <NUM> to the door frame <NUM> with the hinge portion 14d and sets a position of the door <NUM> at the start of analysis, a closing velocity of the door <NUM>, and the like. The multi-body dynamics analysis condition setting unit <NUM> may set a load, displacement, and the like obtained as a result of performing, beforehand, multi-body dynamics analysis on the structural body model <NUM>.

The optimum shape analyzing unit <NUM> finds an optimum shape of the optimization block model <NUM> by executing multi-body dynamics analysis based on the set multi-body dynamics analysis condition and executing optimization analysis based on the optimization analysis condition. <FIG> is an explanatory diagram illustrating the multi-body dynamics analysis condition according to the first embodiment of the present invention and is an explanatory diagram illustrating an operation of closing the door <NUM>. In <FIG>, a state B1 illustrates an open state of the door <NUM>. The state B2 and state B3 illustrate a process of the door <NUM> being brought from the open state into a closed state. The state B4 illustrates the closed state of the door <NUM>.

When the optimum shape analyzing unit <NUM> starts analysis, the door rotates about the hinge portion 14d (see the state B1 to state B3 illustrated in <FIG>), and the outer part 14a collides with the door frame <NUM> as the door <NUM> is closed (see the state B4 illustrated in <FIG>). When the door <NUM> starts rotation, a centrifugal force acts on the optimization block model <NUM>. When the door <NUM> is closed and the door frame <NUM> collides with the outer part 14a, a reaction force is generated, and the reaction force is transmitted to and acts on the optimization block model <NUM> from the outer part 14a via the connected portion <NUM> (see <FIG>). Further, when this happens, negative acceleration is instantaneously caused on the optimization block model <NUM>. Therefore, an inertia force according to mass acts on the optimization block model <NUM>. As described above, the above described three forces (centrifugal force, reaction force, inertia force) act on the optimization block model <NUM>.

The optimum shape analyzing unit <NUM> preferably performs discretization of an optimization parameter in optimization calculation by numerical analysis, that is, in optimization analysis. Preferably, a penalty coefficient in this discretization is equal to or greater than "<NUM>", or limitation is made to three to twenty times the size of the three-dimensional element that becomes a reference. By performing discretization of the optimization parameter, the optimization parameter is able to be reflected in the structural body shape of the thin sheet. The optimum shape analyzing unit <NUM> may perform optimization calculation by topology optimization, that is, topology optimization processing, or optimization processing by any other optimization calculation method. Therefore, as the optimum shape analyzing unit <NUM>, commercially available analysis software using finite elements, for example, may be used. By the optimum shape analyzing unit <NUM> executing optimization analysis processing, among the three-dimensional elements in the optimization block model <NUM>, three-dimensional elements, which have an optimum shape satisfying given analysis conditions, remain.

It should be noted that, as described above, analysis is able to be performed by load transmission similar to load transmission caused in the actual automotive body, which is a reaction force being generated when the door frame <NUM> collides with the outer part 14a and the reaction force being transmitted to the optimization block model <NUM> from the outer part 14a via the connected portion <NUM>.

This point will be described in detail with a comparative example.

<FIG> is an explanatory diagram of a model of a door alone, as a comparative example of the door, which is one example of the movable portion of the structural body model according to the first embodiment of the present invention. <FIG> illustrates, as the model of this comparative example, a door model <NUM> corresponding to a portion of the door <NUM> other than the outer part 14a (for example, an inner part 41b and a hinge portion 41c). <FIG> is an explanatory diagram illustrating a multi-body dynamics analysis condition of the comparative example. In this comparative example, multi-body dynamics analysis and optimization analysis were performed with respect to this door model <NUM>. Specifically, in the optimization analysis of the comparative example, a shape that minimizes displacement of an attachment surface was found, supposing that the outer part 14a is attached to the door model <NUM>. In the multi-body dynamics analysis of the comparative example, analysis was performed with respect to an operation corresponding to an operation of closing the door, which is instantly stopping the door model <NUM> after the door model <NUM> is caused to rotate about a shaft <NUM> of the hinge portion 41c illustrated in <FIG> at a predetermined velocity by a predetermined angle. In this operation, the comparative example is similar to the present invention in that a centrifugal force in the rotation and an inertia force upon the stop of the rotation act on the door model <NUM>, but since the door frame <NUM> is not used in the comparative example, the phenomenon of the outer part 14a colliding with the door frame <NUM> is not able to be considered. Further, since the comparative example does not have the outer part 14a, a property, such as stiffness, that the outer part 14a itself has, is not able to be considered.

As a result, between the case where the multi-body dynamics analysis was performed by setting the above described optimization block model <NUM> to the door frame <NUM> and the case of the above described comparative example (the case where the multi-body dynamics analysis is performed without setting the door model <NUM> to the door frame <NUM>), optimum shapes entirely different from each other were obtained. Such different shapes result in different improvements in their stiffness, for example. Therefore, the present invention has enabled an optimum shape, which is practically usable, to be found, not only by simply constraining the optimization block model <NUM> but also causing a load to be transmitted, through connecting of the optimization block model <NUM> to the structural body model <NUM>. This point will be described in detail in later described examples.

Next, a flow of a process upon actual execution of analysis by using the device for analysis of shape optimization <NUM> configured as described above will be described based on a flow chart illustrated in <FIG>. The process described below is realized by a computer executing, as appropriate, each of the above described processes of the respective functional units (the design space setting unit <NUM>, the optimization block model generating unit <NUM>, the connection processing unit <NUM>, the material property setting unit <NUM>, the optimization analysis condition setting unit <NUM>, the multi-body dynamics analysis condition setting unit <NUM>, and optimum shape analyzing unit <NUM>) of the arithmetic processing unit <NUM> by an operator instructing the computer via the input device <NUM>.

By the operator instructing, with the input device <NUM>, a file of the structural body model <NUM> to be read, the computer reads the structural body model <NUM> from the memory storage <NUM> and displays the structural body model <NUM> on the display device <NUM> (S1). Next, the operator sets, in the displayed structural body model <NUM>, the design space <NUM> to be subjected to optimization processing. Specifically, the operator specifies coordinates of a part to be the design space <NUM> in the structural body model <NUM> and instructs elements of that part to be deleted. By this instruction, the design space setting unit <NUM> of the computer performs a process of deleting the elements of the part to set the design space <NUM> (S3).

When the design space <NUM> has been set, the operator instructs the optimization block model generating unit <NUM> to generate the optimization block model <NUM> of a size that fits in the design space <NUM>. This instruction includes an instruction on which surface in the design space <NUM> the optimization block model <NUM> is to be generated based on. For example, if the optimization block model <NUM> illustrated in <FIG> is to be generated, when an instruction to generate the optimization block model <NUM> with reference to a surface in the front-back direction in the optimization block model <NUM> is given, the optimization block model generating unit <NUM> of the computer generates the optimization block model <NUM> that is meshed, by the optimization block model generating unit <NUM> of the computer pushing out the surface in the automobile's width direction (S5).

When the optimization block model <NUM> has been generated, the operator instructs the optimization block model <NUM> to be connected with the structural body model <NUM>. This instruction includes which element of a rigid body element, a sheet element, or a beam element is to be used as a connection element. Upon receipt of the instruction, the connection processing unit <NUM> of the computer performs a process of connecting the optimization block model <NUM> with the structural body model <NUM> (S7).

When the above described connecting process is completed, the operator sets material properties of the optimization block model <NUM> (S8). Upon this setting, the operator performs input operations on the input device <NUM> to input material properties, such as a Young's modulus, a specific gravity, a yield strength, and a tensile strength. The material property setting unit <NUM> of the computer sets the input material properties to the optimization block model <NUM> that has been connected with the structural body model <NUM> as described above.

Thereafter, the operator sets optimization analysis conditions (S9). Upon this setting, the operator inputs, as the optimization analysis conditions, as described above, an objective condition, such as minimizing the strain energy or maximizing the absorbed energy, and a constraint condition, such as a material volume fraction. Next, the operator inputs a multi-body dynamics analysis condition for performing multi-body dynamics analysis on the structural body model <NUM>, with which the optimization block model <NUM> has been connected, and based on the input multi-body dynamics analysis condition, the multi-body dynamics analysis condition setting unit <NUM> of the computer sets the multi-body dynamics analysis condition (S10).

Next, the optimum shape analyzing unit <NUM> of the computer executes calculation of the multi-body dynamics analysis and calculation of the optimization analysis, to execute optimum shape analysis (S11). Subsequently, the computer displays, on the display device <NUM>, a state where the necessary elements have remained in the optimization block model <NUM> by the optimization calculation and the like, as the result of the optimum shape analysis (S13).

The operator generates a shape model obtained by the optimization calculation or the like and checks stiffness by other structural analysis calculation based on the model.

As described above, according to this first embodiment, since the multi-body dynamics analysis is executed by setting the part to be optimized in the structural body model <NUM> as the design space <NUM>, generating the optimization block model <NUM> in the set design space <NUM>, and connecting the optimization block model <NUM> with the structural body model <NUM>, load transmission from the connected portion <NUM> with the structural body model <NUM> to the optimization block model <NUM> is appropriately achieved and the optimum shape of the optimization block model <NUM> is able to be accurately calculated. As a result, optimization of an automotive body structure, for example, is enabled, stiffness and crash worthiness are able to be improved, and weight reduction of a structural body, such as an automotive body, is able to be realized, while maintaining stiffness and crash worthiness of a movable portion exemplified by a door of the automotive body.

In the above description, a hexahedron as illustrated in <FIG> has been exemplified as a three-dimensional element forming the optimization block model <NUM>, and it has been described that the optimization block model <NUM> is preferably formed of three-dimensional elements, as other three-dimensional elements, each of which is a polyhedron having five or more sides and eight or less sides and each of which has at least one pair of sides parallel to each other. However, the present invention does not exclude a case where a tetrahedron as illustrated in <FIG> is used as a three-dimensional element forming the optimization block model <NUM>. <FIG> are explanatory diagrams illustrating appearance of inside of another mode of the optimization block model of the door, as an example of the movable portion of the structural body model according to the first embodiment of the present invention. <FIG> is a diagram illustrating an example of the other mode of the optimization block model according to the first embodiment of the present invention. <FIG> is an enlarged view illustrating enlarged appearance of inside of the optimization block model illustrated in <FIG> at its front-back direction central portion. If a tetrahedral element is used as a three-dimensional element forming the optimization block model <NUM> as illustrated in <FIG>, model generation is possible by generating only an external form of the design space <NUM> and automatically filling in the inside thereof. However, since the shape of the three-dimensional element becomes a shape having a sharp point at a part where tips of three sides formed of triangles, there is a problem that the optimization block model <NUM> is difficult to be reflected in the structural body of the thin sheet.

<FIG> illustrates enlarged appearance of inside of the optimization block model <NUM> illustrated in <FIG> at its front-back direction central portion. The optimization block model <NUM> illustrated in <FIG> has been generated, as illustrated in <FIG>, such that the element size gradually becomes larger from the surface to the inside. The optimization block model <NUM> may be generated, such that the inside element size is made finer according to the surface element size and the optimization block model <NUM> as a whole has a uniform element size. In this case, accurate analysis becomes possible.

According to the above description, the inner part 14b has been set as the design space <NUM>, but the method of setting the design space <NUM> is not limited thereto. <FIG> are explanatory diagrams illustrating another mode of a design space of a door, as an example of the movable portion of the structural body model according to the first embodiment of the present invention. <FIG> is a diagram illustrating an example of a portion of this movable portion, other than the design space. <FIG> is a diagram illustrating another example of a portion of this movable portion, other than the design space. <FIG> is a diagram illustrating another mode of the optimization block model according to the first embodiment of the present invention. <FIG> is a diagram illustrating another mode of a connected body of the structural body model and the optimization block model according to the first embodiment of the present invention. For example, the design space <NUM> may be set in a portion other than the outer part 14a illustrated in <FIG> and the inner part 14b illustrated in <FIG>. In that case, as compared with the case of <FIG>, only a portion other than the inner part 14b is generated as the optimization block model <NUM> (see <FIG>). A component (corresponding to the door <NUM>) which is obtained by connecting the outer part 14a, the inner part 14b, and the optimization block model <NUM> is illustrated in <FIG>. In this case, when optimum shape analysis similar to that in the above described case where the portion other than the outer part 14a is set as the design space <NUM> is executed (see <FIG>), a shape that has been optimized remains inside the inner part 14b. By doing that, how the inner part 14b is to be reinforced is able to known. Further, if the design space <NUM> is set in the portion other than the outer part 14a and inner part 14b as described above, as compared to the above described case where the portion other than the outer part 14a is set as the design space <NUM>, accurate analysis becomes possible by changing the optimization analysis conditions. For example, since there is the inner part 14b, the material volume fraction of the portion other than the inner part 14b may be decreased.

In the above described example, although an example in which optimization is performed on the door <NUM> (front door) at the front left of the automotive body has been described, the present invention is applicable to other movable portions. Examples of the other movable portions include, a rear door, a back door, and a trunk.

This second embodiment relates to another mode of the optimization block model generating unit <NUM>, and generation of an optimization block model is performed by setting a node in a connected portion with the two-dimensional elements or three-dimensional elements forming the structural body model <NUM>, using hexahedral three-dimensional elements as three-dimensional elements forming the optimization block model <NUM>, and stacking the three-dimensional elements along a surface including the node set in the connected portion. Hereinafter, specific description will be made with reference to the drawings.

<FIG> illustrates a state where the design space <NUM> has been set in a part of a space surrounded by the outer part 14a and the inner part 14b. In this example, what is not parallel with a reference axis surface exists at a connected position between the structural body model <NUM> formed of the two-dimensional elements as illustrated in <FIG> and the three-dimensional elements of the optimization block model <NUM> illustrated in later described <FIG>. This second embodiment is to be applied to such a case.

In this second embodiment, the optimization block model generating unit <NUM> also has an optimization block model generating function described below, in addition to the above described optimization block model generating function according to the first embodiment. Specifically, the optimization block model generating unit <NUM> generates, as illustrated in <FIG>, a reference surface <NUM> that becomes a reference for generating the optimization block model <NUM>, with a sheet element, by connecting with straight lines nodes present at a part where the structural body model <NUM> has been deleted, on a surface in the design space <NUM> at an inner part 14b side thereof. When the reference surface <NUM> has been generated, the optimization block model generating unit <NUM> generates the optimization block model <NUM> by pushing out the reference surface <NUM> in the automobile's width direction to be integrated by node sharing.

A state where the optimization block model <NUM> according to the second embodiment has been generated is illustrated in <FIG> and <FIG>. <FIG> illustrates a state of a mesh of the generated optimization block model <NUM>. <FIG> illustrates the connected portion <NUM> in the optimization block model <NUM>. As described above, the optimization block model generating unit <NUM> generates the reference surface <NUM> (see <FIG>) and generates the optimization block model <NUM> by using this reference surface <NUM>. Thereby, there is an effect that a slanted part of the connected portion <NUM> between the optimization block model <NUM> and the structural body model <NUM> becomes smoothly straight-lined. Accordingly, a connected state between the optimization block model <NUM> and the structural body model <NUM> becomes smooth, and as a result, an effect of load transmission between the optimization block model <NUM> and the structural body model <NUM> becoming accurate is achieved.

As a comparative example with respect to this second embodiment, an example in which the optimization block model <NUM> has been generated, similarly to the first embodiment, without generating the reference surface <NUM> beforehand, is illustrated in <FIG> is a diagram illustrating a state of a mesh of the optimization block model <NUM> generated in the comparative example. <FIG> illustrates the connected portion <NUM> in the optimization block model <NUM> according to the comparative example. In the comparative example illustrated in <FIG>, as compared with the optimization block model <NUM> according to this second embodiment illustrated in <FIG>, steps <NUM> are found to be formed in the slanted part, and the connected portion <NUM> of the comparative example is found to be not smooth.

According to this second embodiment, even if the optimization block model <NUM> is shaped to have a slope, a connected state between the optimization block model <NUM> and the structural body model <NUM> becomes smooth, and as a result, load transmission between the optimization block model <NUM> and the structural body model <NUM> becomes accurate.

In the above described first and second embodiments, as the process of generating the optimization block model <NUM> by the optimization block model generating unit <NUM>, the example in which the optimization block model <NUM> has been generated with a single body has been described, but in this third embodiment, the optimization block model generating unit <NUM> may form the optimization block model <NUM> with a plurality of blocks formed of three-dimensional elements and generate the optimization block model <NUM> by connecting these plurality of blocks by using a rigid body element, a beam element, or a two-dimensional element. Hereinafter, a process of generating the optimization block model <NUM> according to the third embodiment will be described specifically.

<FIG> to <FIG> are explanatory diagrams of a method of generating an optimization block model according to this third embodiment. <FIG> is a diagram illustrating a state where an upper portion of the optimization block model according to the third embodiment of the present invention has been generated. <FIG> is a diagram illustrating a state where a lower portion of the optimization block model according to the third embodiment of the present invention has been generated. <FIG> is a diagram illustrating a state where the optimization block model according to the third embodiment of the present invention has been connected with a structural body model. The optimization block model generating unit <NUM> also has an optimization block model generating function according to this third embodiment, in addition to the above described optimization block model generating functions according to the first and second embodiments. In this third embodiment, the optimization block model generating unit <NUM> uses the method of generating the reference surface <NUM> described in the second embodiment and generates the optimization block model <NUM> with a plurality of blocks.

Specifically, the optimization block model generating unit <NUM> generates a plurality of independent reference surfaces 33a and 33b first in the design space <NUM> illustrated in <FIG> (see <FIG>). Next, the optimization block model generating unit <NUM> pushes out the upper and triangular reference surface 33a illustrated in <FIG> in the automobile's width direction to generate an upper block 27a as illustrated in <FIG>, which is a triangular prism portion. Subsequently, the optimization block model generating unit <NUM> pushes out the reference surface 33b (see <FIG>) below the triangular prism, in the automobile's width direction, to generate a lower block 27b as illustrated in <FIG>. Thereafter, the optimization block model generating unit <NUM> sequentially connects, with the connected portion <NUM>, the generated blocks together, as well as the optimization block model <NUM> and the structural body model <NUM> (automotive body) together, the optimization block model <NUM> being a connected body of these upper block 27a and lower block 27b (see <FIG>).

As described above, in this third embodiment, by generating the optimization block model <NUM> through division into a plurality of blocks, the optimization block model <NUM> is able to be generated, not only in the design space <NUM> formed of a block of a simple shape, such as a cuboid, but also in the design space <NUM>, which is not of a simple shape, for example, the design space <NUM> formed of a block of a complex shape or a block including a slope.

Further, by generating the optimization block model <NUM> through division into a plurality of blocks, the optimization block model <NUM> is able to be formed with a smooth surface. Thereby, the connection between the optimization block model <NUM> and the structural body model <NUM> is able to be made smooth and as a result, load transmission between the optimization block model <NUM> and the structural body model <NUM> is able to be achieved accurately.

In the above described third embodiment, any of the upper block 27a and lower block 27b may be generated first, and the order of the connection between these blocks (the upper block 27a and the lower block 27b) and the connection between the upper block 27a or lower block 27b with the automotive body is not particularly limited in the present invention and any of these connections may be performed first.

Further, in this third embodiment, since optimization basically targets a space where nodes are shared, connection of blocks is preferably performed such that the connected area is equal to or less than <NUM>%.

Claim 1:
A computer-implemented method for optimizing a portion of a structural body model including a movable portion of an automotive body, the movable portion relating to a part including a steel sheet, whereby the optimizing realizes weight reduction of a structural body while improving stiffness or crash worthiness, by
using three-dimensional elements, the method comprising:
a design space setting step of setting, as a design space, the portion to be optimized in the movable portion;
an optimization block model generating step of generating, in the set design space, an optimization block model in the portion, the optimization block model
being formed of three-dimensional elements and to be subjected to optimization analysis processing;
a connection processing step of connecting the generated optimization block model with the structural body model so that a load is transmitted through the connecting;
a material property setting step of setting a material property for the optimization block model;
an optimization analysis condition setting step of setting an optimization analysis condition for finding an optimum shape of the optimization block model, the optimization analysis condition comprising
an objective condition including one of minimizing displacement, minimizing strain energy, minimizing generated stress, or maximizing absorbed energy, and
a constraint condition including at least one of a material volume fraction, displacement of an arbitrary portion, a generated stress;
a multi-body dynamics analysis condition setting step of setting a multi-body dynamics analysis condition for performing multi-body dynamics analysis on the structural body model with which the optimization block model has been connected; and
an optimum shape analyzing step of executing, based on the set optimization analysis condition and multi-body dynamics analysis condition, the multi-body dynamics analysis on the optimization block model and thereby finding the optimum shape of the optimization block model in the portion.