JP4980015B2 - Air pool simulation method and simulation program - Google Patents

Description

  The present invention relates to an air pool simulation method and a simulation program for simulating an air pool generated in a workpiece when a dipping process is performed.

  In general, in the work dipping process in electrodeposition coating or plating, it is important not to cause air pockets (air pockets) in the work in order to form a uniform coating film or plating film. This air pocket is a recess that can be formed when a workpiece having a complicated shape is immersed, for example, if it is a vehicle body such as an automobile, air remains in a space such as a recess such as the inner surface of the hood, the inner surface of the roof, or the lower surface of the floor. If this air pocket is generated, poor coating and poor plating will occur.

  In view of this, a method has been proposed in which a state in which a workpiece is immersed is simulated using a computer to predict the occurrence of air pockets. In computer simulation of air pockets, a workpiece is modeled with data of multiple elements such as meshes and nodes, and the feature points of elements (for example, centroid points, vertices) Geometric techniques are known in which the positions of the inner center point, outer center point, and perpendicular point) are determined by comparing the positions in the direction of gravity.

  For example, Patent Document 1 discloses that each surface of a workpiece is divided into an arbitrary number of triangular polygons (triangular elements) based on the vertex coordinate data, and the state change between air and liquid in the immersion bath for each triangular polygon. A method for determining whether or not the surface portion can be an air pocket when the workpiece is simulated and immersed in the immersion bath in the posture of the tank entrance angle is disclosed.

  By the way, in the geometric method of modeling a workpiece with data of multiple elements, the workpiece is modeled as a thin plate element, and the edge of the workpiece or the edge of the hole is used as a free edge, and the element is in contact with this free edge. Is initially set as a liquid attribute, and an initial condition for determining the attribute of another element is known (for example, see Japanese Patent Application No. 2006-19413 by the present applicant).

This is focused on the fact that the edge of the workpiece, the edge of the hole, etc. always touch the liquid when immersed, and the element that contacts the free edge is initially set to the liquid attribute, and this initial set element and By repeating the process of determining the attribute of each element from the positional relationship with other elements, it is possible to finally determine the attributes of all the elements and determine the presence or absence of an air pocket.
JP 2000-51750 A

  However, this geometric method with the initial condition of the element in contact with the free edge is a method applied to a member that can be simulated without considering the plate thickness. Therefore, it is difficult to apply to a member whose plate thickness cannot be ignored. That is, when modeling with a plurality of surface elements in consideration of the thickness of the workpiece, the surface elements are continuous on all surfaces, and free edges are eliminated. For this reason, if an initial condition based on a free edge is applied to a model that takes into account the workpiece thickness, simulation cannot be executed normally.

  For example, as shown in FIG. 15, when a solid part 100 having a depression on the bottom surface is modeled by a plurality of surface meshes, a model SDM in which the surface meshes are continuous on all surfaces is obtained as shown in FIG. Since there is no free edge in this model SDM, if an initial condition based on a free edge is set, the model SDM ends abnormally at the time of initial condition setting, and an appropriate simulation result cannot be obtained.

  The present invention has been made in view of the above circumstances, and an air pool simulation method capable of obtaining an accurate simulation result by a method similar to the geometric method using a thin plate element even for a member whose plate thickness cannot be ignored. And it aims at providing a simulation program.

In order to achieve the above object, according to the first method for simulating a puddle according to the present invention, a computer models a work to be dipped with data of a plurality of elements, and the attribute of each element is determined based on the positional relationship in the gravity direction. In an air pool simulation method in which a computer determines whether the gas is a liquid or a liquid and simulates an air pool, the surface shape of the workpiece is divided into a plurality of surface elements, and the plurality of surface elements are all of the workpiece. A model building step for building a continuous analysis model on the surface, and a new element having a discontinuous part where the elements are not connected to the surface element at the highest height in the direction opposite to gravity in the above analysis model bonded, and the initial element setting step for setting this new element as the initial element of the attributes of a liquid, including the initial element And the direction opposite position of gravity in the analytical model of any surface elements sex has been determined, a direction opposite to the gravity of the analytical model of the other surface element adjacent to any surface element this attribute has been determined And a determination step of determining the attribute of each surface element.
According to the second method for simulating air accumulation according to the present invention, a computer models a work to be dipped with data of a plurality of elements, and the attribute of each element is gas or liquid based on the positional relationship in the gravity direction. In the air pool simulation method in which the computer determines whether or not the air pool is simulated, the surface shape of the workpiece is divided into a plurality of surface elements, and an analysis model in which the plurality of surface elements are continuous on the entire surface of the workpiece is obtained. A model construction step to construct, an initial element setting step for selecting an element whose normal direction of the surface element is not less than a set angle with respect to the direction of gravity from the analysis model, and setting as an initial element of the liquid attribute; and the initial The position in the direction opposite to gravity in the above analysis model of any surface element whose attribute including the element is fixed, and this attribute Comparing the gravity of the analytical model of the other surface element adjacent to any surface element determined to have the opposite direction of the position, characterized in that it comprises a determination step of determining attributes of each surface element.
In the third simulation method of the air pool according to the present invention, a computer models a work to be dipped with data of a plurality of elements, and the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity. In the air pool simulation method in which the computer determines whether or not the air pool is simulated, the surface shape of the workpiece is divided into a plurality of surface elements, and an analysis model in which the plurality of surface elements are continuous on the entire surface of the workpiece is obtained. Model building step to be constructed, and an element in which no other surface element exists in at least one line-of-sight direction within the range of the solid angle after setting the solid angle in the direction opposite to the gravity direction around the representative point of the surface element An initial element setting step for selecting and setting as an initial element of the liquid attribute;
The position of an arbitrary surface element having an attribute including the initial element in the direction opposite to gravity in the analysis model in the analysis model, and the analysis model of another surface element adjacent to the arbitrary surface element having the attribute determined And a step of determining the attribute of each surface element by comparing gravity with a position in the opposite direction.

The first air pool simulation program according to the present invention models a workpiece to be dipped with data of a plurality of elements, and determines whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity. A computer-executable air pool simulation program for deciding and simulating air pools. In this simulation model, the surface shape of the workpiece is divided into a plurality of surface elements, and the plurality of surface elements are continuous on the entire surface of the workpiece. And a new element having a discontinuous part where the elements are not connected to the surface element at the highest height in the direction opposite to the gravity in the analysis model . an initial element setting step for setting an element as the initial element of the attributes of a liquid, has finalized attributes including the initial element Compares the opposite direction to the position of gravity in the analytical model of any surface element, the gravity of the analytical model of the other surface element adjacent to any surface element this attribute has been determined the position in the opposite direction The computer executes a determination step of determining the attribute of each surface element.
The second air pool simulation program according to the present invention models a workpiece to be dipped with data of a plurality of elements, and determines whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity. A computer-executable air pool simulation program for deciding and simulating air pools. In this simulation model, the surface shape of the workpiece is divided into a plurality of surface elements, and the plurality of surface elements are continuous on the entire surface of the workpiece. A model construction step for constructing, an element for which the normal direction of the surface element is equal to or greater than a set angle with respect to the direction of gravity from the analysis model, and an initial element setting step for setting as an initial element of the liquid attribute; A position in the direction opposite to gravity in the above analysis model of an arbitrary surface element whose attributes including the initial element are determined; The computer executes a determination step of comparing the position of the other surface element adjacent to an arbitrary surface element with the determined attribute in the direction opposite to gravity in the analysis model and determining the attribute of each surface element. It is characterized by doing.
The third air pool simulation program according to the present invention models a workpiece to be dipped with data of a plurality of elements, and determines whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity. A computer-executable air pool simulation program for deciding and simulating air pools. In this simulation model, the surface shape of the workpiece is divided into a plurality of surface elements, and the plurality of surface elements are continuous on the entire surface of the workpiece. A model construction step for constructing a solid angle and setting a solid angle in a direction opposite to the gravity direction with the representative point of the surface element as a center, and no other surface element exists in at least one line-of-sight direction within the range of the solid angle Select the element and set the initial element setting step to set as the initial element of the liquid attribute, and the attribute including the initial element is confirmed The position of any surface element in the direction opposite to gravity in the analysis model and the position in the direction opposite to gravity in the analysis model of another surface element adjacent to any surface element for which this attribute is determined The computer executes a determination step of comparing and determining an attribute of each surface element.

  According to the present invention, a method similar to the geometric method using thin plate elements can be applied to a member whose plate thickness cannot be ignored, and a simple and accurate simulation result can be obtained.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 7 relate to a first embodiment of the present invention, FIG. 1 is a basic configuration diagram of a simulation apparatus, FIG. 2 is a schematic explanatory diagram of a painting line of a vehicle body, and FIG. 3 is a mesh setting for a free edge. FIG. 4 is an explanatory diagram showing conditions for selecting an initial mesh, FIG. 5 is a flowchart of an air pocket simulation program, FIG. 6 is an explanatory diagram showing a simulation result, and FIG. 7 is an explanatory diagram showing a simulation result in consideration of the plate thickness. FIG.

  As shown in FIG. 1, the simulation apparatus 1 according to the present embodiment creates an air pocket (air pocket) generated in a work when an immersion process such as electrodeposition coating or plating is performed on a work such as a body shell of an automobile. To simulate. The air pocket simulation apparatus 1 is configured using a single computer such as a microcomputer or a personal computer, or a plurality of computers connected to each other via a network.

  Below, the example which comprises the simulation apparatus 1 with a single computer for convenience is demonstrated. The simulation apparatus 1 includes an arithmetic device 10, an input device 11 such as a keyboard and a mouse, a display device 12 such as a CRT and a liquid crystal display, an external storage device 13 such as a magnetic disk and an optical disk, and the like.

  The arithmetic device 10 includes an internal memory such as a CPU, a ROM and a RAM, an input / output interface, and the like, and includes a simulation program stored in an internal ROM, an external storage device 13 and an external storage medium, or a network (not shown) A simulation program loaded from the outside via the communication device is executed by the CPU, and the workpiece (object) to be analyzed instructed via the input device 11 is immersed in the immersion bath in a pseudo manner, and the object is obtained by the immersion. Simulates the air pockets that occur.

  For example, as an application example of the simulation according to the present invention, there is a simulation in which the distribution of the electrodeposition liquid and air during the electrodeposition coating of the vehicle body is numerically analyzed to predict the occurrence of air pockets in the object to be coated. Here, the painting line of the vehicle body will be briefly described with reference to FIG.

  As shown in FIG. 2, a vehicle body body 20 of an automobile configured by joining a plurality of vehicle body panels to each other by welding or the like is transported in a substantially horizontal direction on a painting line while being mounted on a hanger of a transport device 21. The In the painting line, as a pretreatment for electrodeposition coating, the body panel is subjected to treatments such as degreasing, water washing, surface adjustment, film formation, water washing and the like.

  After these processes, the vehicle body 20 descends toward the electrodeposition tank 22 and moves substantially horizontally while being immersed in the electrodeposition liquid 23. In this state, paint is deposited on the vehicle body panel by applying a voltage to the vehicle body 20 and electrodes (not shown) in the electrodeposition tank 22. Thereafter, the vehicle body 20 is pulled up from the electrodeposition tank 22 by the transfer device 21, and the electrodeposition liquid 23 adhering to the vehicle body panel without being electrodeposited is removed by washing.

  The function of the simulation program executed in the arithmetic device 10 can be expressed by the model construction unit 10a, the initial mesh setting unit 10b, the air pocket determination unit 10c, and the post processing unit 10d. The arithmetic unit 10 simulates the generation of air pockets using a geometric technique based on an analysis model obtained by modeling the shape of an object with data of a plurality of elements, and outputs and displays the simulation result on the display unit 12. The display device 12 may display not only the simulation result but also the simulation process.

  The air pocket simulation according to the present invention uses a surface model constructed by dividing the surface shape of an object into a plurality of surface elements, and the thickness of the object is determined using a simple method similar to the analysis model using thin plate elements. It is possible to accurately simulate the generation of air pockets even for members that cannot be ignored. Hereinafter, the air pocket simulation in the present embodiment will be described.

  The model construction unit 10a divides the shape data of the object into a plurality of surface elements, and constructs an analysis model in which the plurality of surface elements are continuous on the entire surface of the object. As a method for constructing the analysis model, a method using a mesh that represents a surface shape of an object divided into a plurality of predetermined shapes, a method of arranging a plurality of nodes (nodes) on the surface of the object, or the like is used. be able to. In the following, an example of constructing an analysis model by using a surface model that expresses the surface shape of an object with a triangular mesh and arranging the mesh data of this surface model in a three-dimensional space will be explained. The process is the same when using nodes.

  Note that the shape of the mesh as the surface element of the analysis model is not limited to a triangular shape, and may be a rectangular or polygonal shape. Each mesh includes, for example, data such as a mesh number for identifying itself, coordinate values of nodes (nodes) of the mesh with respect to a predetermined reference point (coordinate values on the XYZ coordinate axes in the three-dimensional space), mesh attributes, and the like. Is granted. Hereinafter, for the sake of convenience, it is assumed that the direction of the Z axis in the XYZ orthogonal coordinate system is opposite to the direction of gravity.

  The external storage device 13 stores various data necessary for the air pocket simulation process. For example, the external storage device 13 has a database composed of attribute record groups to which individual identification numbers (record numbers) are assigned for each object, and each attribute record includes a mesh number and a node point. Coordinate values, attribute data, and the like are described in association with each other.

  The initial mesh setting unit 10b sets the initial mesh of the liquid attribute by equivalently setting the dipping condition of the free edge. This initial mesh is used as an initial condition for separating / determining the attributes of all meshes of the analysis model into liquid and gas. It is a determined element.

  Further, the free edge means an edge portion of the workpiece, that is, an edge portion of the workpiece or an edge portion of a hole formed in the workpiece, and is a portion that contacts the liquid unconditionally during immersion. In other words, a free edge is an edge (side) belonging to only a single element (mesh) that is not shared by a plurality of elements, and is a discontinuous portion in which elements are not connected to each other, It has an immersion condition that it is always immersed in a liquid.

  However, in a member in which the plate thickness cannot be ignored, for example, a solid part having a dent on the bottom surface (see FIG. 15 described above), all the surface meshes are a continuous model, and there is no free edge. Therefore, in the initial mesh setting unit 10b, the free edge immersion conditions are equivalently set for the analysis model in which all the surface meshes are continuous, and the mesh having the free edge immersion conditions is set as the initial mesh. Similar to the analysis model using only thin plate elements, it is possible to set initial conditions based on free edges, and to execute simulations normally.

  The free edge immersion conditions can be set by creating a new mesh with free edges separately from the existing mesh that makes up the analysis model, and joining this new mesh to a predetermined mesh in the analysis model. And an initial mesh that becomes a free edge can be obtained. Although this initial mesh may be set at only one location, it is desirable to set it at a plurality of locations as appropriate according to the shape of the workpiece.

  In this case, without adding a new mesh to the analysis model, select the mesh that is the initial condition in advance while watching the monitor screen, or separate the mesh attribute that is the initial condition in advance into the liquid, thereby analyzing the model. A predetermined mesh among the existing meshes that constitute the above may be set as the initial mesh.

  Furthermore, by deleting a predetermined mesh from existing meshes constituting the analysis model, a portion where the mesh becomes discontinuous is forcibly created, and the mesh adjacent to the deleted mesh is defined as a free edge. The initial mesh may be set as follows.

  An adjacent mesh is a mesh that shares nodes or sides with a mesh to be determined.

  A newly generated mesh or a mesh to be selected, separated, or deleted can be set at any position as long as it is a part that reliably contacts the immersion liquid, such as the outer surface of the workpiece. In general, it is desirable to set the initial mesh at a position where the height in the Z direction (the direction opposite to gravity) is as high as possible.

  For example, with respect to the analysis model SDM of a solid part having a depression on the bottom surface shown in FIG. 16, a new mesh MF is applied to the edge having the highest height in the Z direction (opposite to gravity) as shown in FIG. Join and reconstruct as analytical model SDM ′. In the analysis model SDM ′, the added mesh MF is a mesh having a free edge opened to the space, and the attribute is set to liquid with the mesh MF as an initial mesh.

  On the other hand, when the initial mesh is set from the existing meshes of the analysis model, the applicable range is limited to relatively simple objects, but the relationship between the normal direction of each mesh surface and the direction of gravity is determined. By checking, a mesh that can be set as the initial mesh can be selected.

  For example, an analysis model SDM2 as shown in FIG. 4 will be described as an example. With respect to each mesh constituting the analysis model SDM2, a normal line extending from a representative point (for example, a center of gravity) on each mesh surface, Then, it is checked whether or not the angle formed by the line extending in the direction of gravity from the representative point is equal to or larger than the set angle. For example, if the set angle is 90 ° and the condition that the angle between the normal line of a certain mesh and the direction of gravity is 90 ° or more is satisfied, the mesh is a mesh outside the object, and air remains on the surface. Therefore, it is determined that the mesh is in contact with the immersion liquid without fail, and the mesh is selected as a mesh having equivalent free edge immersion conditions. Then, the selected mesh is set as an initial mesh, and the attribute is set to liquid.

  The air pocket determination unit 10c sets, for each mesh forming the analysis model, either a gas attribute corresponding to an air pocket location or a liquid attribute corresponding to an immersion location such as an electrodeposition liquid. . As for the attribute of this mesh, all the meshes are initially set to the gas attribute (before immersion), and then the mesh attribute becomes liquid or gas by comparing the height in the Z direction with the adjacent mesh including the initial mesh. It is determined whether the air pocket remains (that is, whether or not it becomes an air pocket), and when it is determined to be liquid, the attribute of the mesh is changed to liquid and the attribute data is rewritten.

  The determination of the air pocket basically assumes that the specific gravity of the immersion liquid is larger than the specific gravity of the air. That is, when the attribute of a certain mesh is determined, the determination target mesh and the comparison target mesh are compared in height in the Z direction (the direction opposite to gravity). Then, if the comparison target mesh is higher than the determination target mesh and has a liquid attribute, it is determined that the immersion liquid penetrates the relatively low determination target mesh by pushing the air and is filled with the immersion liquid. Thus, the attribute data of the determination target mesh is liquid. On the other hand, when the attribute of the relatively high comparison target mesh is gas, the attribute data of the determination target mesh is not changed, and the comparison is changed and the determination is repeated. Then, this determination is repeated to separate and determine the attributes of all the meshes as liquid and gas, and the gas-liquid boundary line of the air pocket indicated by the presence of the mesh whose attribute is determined as gas is derived. A plurality of gas-liquid boundary lines may be derived.

  The post processing unit 10d performs a visualization process for enabling easy understanding of the simulation result and data output of the simulation result. In the visualization process of simulation results, the mesh determined as the liquid attribute, the mesh determined as the gas attribute, and the boundary line (gas-liquid boundary line) are classified according to hue, shading, etc. And express the size explicitly.

  The air pocket simulation process executed by the CPU of the arithmetic unit 10 will be described below with reference to the flowchart of FIG.

  In the simulation program of FIG. 5, first, in step S1 corresponding to the model construction step of the present invention, the surface shape of the object is modeled with data of a plurality of surface elements, and an analysis model for numerical calculation is constructed. This analysis model is constructed by, for example, a model obtained by dividing the surface shape of a workpiece with a plurality of triangular meshes.

  Next, the process proceeds to step S2, the gravity direction in the analysis model is set, and in step S3, the analysis model is temporarily used as a simulation of the state in which the object before being immersed in the electrodeposition liquid is filled with air. After setting all of the meshes to the gas attribute, the initial mesh is set to the analysis model. The initial mesh becomes a free edge by adding a new mesh to the analysis model (see FIG. 3), selecting a predetermined mesh from the analysis model mesh (see FIG. 4), or separating or deleting it. Set the mesh. In step S4, the attribute of the initial mesh is changed from gas to liquid as an initial condition for separating the attributes of all meshes into liquid and gas. The above steps S3 and S4 correspond to the initial element setting step of the present invention.

  Next, it progresses to step S5 and the air pocket determination calculation process equivalent to the determination step of this invention is implemented. This air pocket determination calculation process is a process for determining the occurrence of an air pocket by determining the respective attributes by comparing the height of each mesh in the direction opposite to the gravity, and a conventional method can be used. The comparison of the height of each mesh is, for example, the position in the Z direction (direction opposite to gravity) such as the center of gravity, inner center, outer center, and centroid of each mesh, and each vertex of each mesh Is performed by comparing feature points such as the highest vertex (the vertex having the highest position in the Z direction).

  For example, when comparing the positions of the centroid points, the heights of the centroid points in the Z direction of the meshes to be judged and the adjacent meshes are compared, and the centroid points of the adjacent meshes are Is higher, if the attribute of the adjacent mesh is liquid, the attribute of the determination target mesh is determined to be liquid. On the other hand, when the barycentric point of the adjacent mesh is lower than the barycentric point of the determination target mesh, the attribute of the determination target mesh is not changed, and the comparison is changed and the determination is repeated. This determination is performed for all meshes including the initial mesh, the boundary between the mesh having the liquid attribute and the mesh having the gas attribute is detected as a gas-liquid boundary line, and the gas-liquid boundary line is corrected as necessary. I do.

  In addition, the process which corrects a gas-liquid boundary line gives the same attribute to the several boundary line which belongs to one air pocket, for example, and when the height of each boundary line differs, it changes to one horizontal line. Modify it so that it is closer.

  Then, it progresses to step S6, a post process is performed, and a main routine is complete | finished. In this post-processing, a visualization process is performed so that the simulation result can be easily grasped and output to the display device 12, and the simulation result data is output to a file as necessary.

  The simulation result displayed on the display device 12 by the post processing is exemplified in FIG. The example of FIG. 6 shows a simulation result for the model of FIG. 3 in which an initial mesh is newly generated and added to the analysis model, and it can be seen that the dent is correctly recognized as an air pocket on the bottom surface.

  Further, as shown in FIG. 7A, the above simulation program can be applied to the member 101 in which the projecting portion 102 whose bottom surface is opened is T-coupled, and considering the plate thickness. Accurate simulation results can be obtained.

  For example, when an analysis model is constructed with only thin plate elements without considering the plate thickness for the member 101, an analysis model SFM1 as shown in FIG. 7B is obtained. In this analysis model SFM1, the end of the member becomes a free edge, and the simulation can be executed without any problem in processing, but the air pocket generated inside the protrusion 102 cannot be grasped, and the simulation result indicates that there is no air pocket. It causes misjudgment.

  On the other hand, when the analysis model considering the plate thickness is constructed with the surface elements, an analysis model SFM2 as shown in FIG. 7C is obtained, and all the surface meshes continuously have no free edges. By joining the mesh MF2 to an existing mesh and adding it, an initial mesh that becomes a free edge can be set. As a result, the simulation can be executed by the same method as the analysis model SFM1 in FIG. 7B, and it is correctly recognized that an air pocket is generated inside the protrusion 102 as shown in FIG. 7C. Simulation results can be obtained.

  As described above, according to the first embodiment, even when a member whose thickness is not negligible is simulated with a model in which all surface elements are continuous, it is complicated by intentionally setting an initial element that becomes a free edge. A method similar to the geometric method using only thin plate elements can be used without using a three-dimensional model. Thereby, it is possible to shorten the calculation time of the simulation and reduce the load on the computer, and it is possible to obtain an accurate simulation result while being simple.

  Next, a second embodiment of the present invention will be described. FIG. 8 is a flowchart of an air pocket simulation program according to the second embodiment of the present invention.

  As described above, when setting an initial mesh in an analysis model constructed with surface elements, it is desirable to set the initial mesh at a high position in the analysis model. Therefore, in the second embodiment, an edge of a mesh located at a high position when the work is viewed from the horizontal and vertical directions with respect to the liquid surface is extracted, and an initial mesh is set based on the extracted edge.

  A second form of simulation program having this edge extraction processing is shown in the flowchart of FIG. In this simulation program, first, in steps S11 and S12, similarly to steps S1 and S2 in the simulation program of the first embodiment (see FIG. 5), an analysis model for numerical calculation is constructed and the direction of gravity is set. . Next, in step S13, the analysis model simulating the workpiece is viewed from the horizontal and upward directions, and a surface mesh that can be seen from these directions is extracted.

  Next, the process proceeds to step S14, and the edge detection angle of the mesh is set as the normal intersecting angle with the adjacent mesh. Further, in step S15, a mesh whose normal crossing angle is larger than a specified value is extracted from the surface mesh seen from the horizontal and upward directions, and the edge of this mesh is detected as a processing target edge at a high position. To do.

  In step S16 following step S15, it is checked whether or not there is a mesh whose representative point (centroid point, inner center point, vertical point, etc.) is higher than the detected edge. If there is no mesh higher than the detected edge, the process proceeds from step S16 to step S18. If there is a mesh higher than the detected edge, the mesh is extracted in step S17, and the edge of the extracted mesh is processed. Advances to step S18.

  Step S18 and subsequent steps are the same as in the first embodiment, and an initial mesh is set in step S18. This initial mesh setting is based on the detected high-position edge, and a new mesh that becomes a free edge is joined to this edge, or the detected edge mesh itself is used as the initial mesh, or the detected edge The initial mesh is set by performing a process such as deleting the mesh that touches.

  Steps S19, S20, and S21 are the same as steps S4, S5, and S6 of the first embodiment, and after changing the attribute of the initial mesh from gas to liquid as an initial condition, air pocket determination calculation processing is performed and post processing is performed. To display the simulation results.

  Also in the second embodiment, as in the first embodiment, by setting the initial element that is intentionally a free edge, even for a member having a plate thickness, only a thin plate element is used without using a complicated three-dimensional model. By applying a technique similar to the geometric technique according to, simulation can be executed normally, and a simple and accurate simulation result can be obtained.

  Next, a third embodiment of the present invention will be described. FIGS. 9 and 10 relate to a third embodiment of the present invention, FIG. 9 is an explanatory diagram showing setting of a solid angle, and FIG. 10 is a flowchart of an initial setting program.

  The third form develops a method of selecting a mesh that can be set as an initial mesh from the existing meshes described in FIG. 4 of the first form for an analysis model in which all surface meshes are continuous, The scope of application will be further expanded.

  That is, in the third mode, a solid angle ψg is set for each mesh constituting the analysis model, and whether or not another mesh exists in the line-of-sight direction within the range of the solid angle ψg of the mesh to be determined. To determine whether or not the initial mesh can be set. As shown in FIG. 9, the solid angle ψg has a vertex in the direction opposite to the gravity direction with respect to a certain mesh (for example, the center of gravity, inner center, outer center, etc.) as the center. If a hemisphere is assumed as the direction, this is the angle that the hemisphere makes.

  When a certain mesh is determined as a determination target and another direction is viewed within the range of the solid angle ψg from the representative point of the determination target mesh, if there is another mesh in any direction, the determination target mesh Means that it is surrounded by other meshes (walls), which means that there is a high possibility that air stays and air pockets are generated. Conversely, when there is no other mesh in at least one direction, it means that the liquid enters from the direction without the mesh and the determination target mesh is immersed in the liquid. Therefore, when another direction is seen within the range of the solid angle ψg from the representative point of the determination target mesh, if there is no other mesh in only one direction, the determination target mesh can be set as the initial mesh. it can.

  Whether there is another mesh when viewed in the line-of-sight direction within the range of the solid angle ψg from the determination target mesh, for example, examines the inner product of the line-of-sight vector from the determination target mesh and the normal vector of the other mesh. And so on.

  Specifically, the initial mesh is set according to the initial setting program shown in FIG. This initial setting program corresponds to steps S3 and S4 in the simulation program of the first embodiment described above (see FIG. 5).

  When the analysis model is constructed (step S1 in FIG. 5) and the gravity direction is set (step S2 in FIG. 5) in the entire simulation program, the initial setting program is started, and the analysis model is configured in the first step S31. A certain surface mesh is selected as a determination target mesh from the surface meshes to be determined.

  Next, the process proceeds to step S32, and the other direction is viewed within the solid angle ψg around the representative point of the determination target mesh. Specifically, it looks up from the horizontal direction and from below the horizontal with the representative point of the determination target mesh as the center. In step S33, it is checked whether or not there is a direction in which no other mesh exists at the point looked up. If there is also one direction in which no other mesh exists within the solid angle ψg, step S34 is performed. The determination target mesh is set to the initial submerged mesh. Here, the initial submerged mesh is an initial mesh set in the liquid attribute as an initial condition.

  On the other hand, if any other mesh exists in any direction within the range of the solid angle ψg, the process proceeds from step S33 to step S35, and the determination target mesh is set as the initial liquid outside mesh. Here, the initial submerged mesh is a mesh set as a gas attribute as an initial condition.

  After the initial conditions are set in step S34 or step S35, the process proceeds to step S36, and it is checked whether or not the initial settings have been performed for all the surface meshes of the analysis model. If the initial settings for all surface meshes have not been completed, the process returns to step S31 to select the next determination target mesh and repeat the above processing to complete the initial settings for all surface meshes. In this case, this program is terminated and the process proceeds to the air pocket determination calculation process (step S5 in FIG. 5) of the simulation program.

  In the third mode, as in the above-mentioned modes, a simulation is normally performed by applying a method similar to the geometric method using only thin plate elements without using a complicated three-dimensional model for a member having a plate thickness. In addition, the initial conditions can be set from the elements constituting the existing model, and a simple method can be achieved.

  Next, a fourth embodiment of the present invention will be described. 11 to 14 relate to a fourth embodiment of the present invention, FIG. 11 is an explanatory diagram showing the setting of a surface vector, FIG. 12 is an explanatory diagram showing the definition of a solid angle, and FIG. FIG. 14 is a flowchart of the initial setting program.

  The process of determining an initial mesh using the solid angle ψg described in the third embodiment takes a relatively long processing time because the determination process is performed by looking up all directions within the range of the solid angle ψg. Therefore, in the fourth embodiment, the processing time is shortened by narrowing down the solid angle ψg in the third embodiment.

  First, as a pre-processing for narrowing down the solid angle ψg, when generating a surface mesh, the mesh node is set so that the direction of the normal vector (surface vector) determined from the vector of each mesh node faces the outside of the object. Arrange the layout. As shown in FIG. 11, normally, a surface mesh is generated with the direction of the surface vector Vf of each mesh msh as the front surface (object external side) and the opposite direction as the back surface (object internal side).

  Using this surface vector Vf, the solid angle ψ in the fourth embodiment is obtained by using a representative point of the mesh (for example, the center of gravity, inner center, outer center as shown in FIG. 12). Etc.) is defined as an angle in a range in which the solid angle ψg of the hemisphere having the direction opposite to the direction of gravity G as the apex direction and the solid angle ψs of the hemisphere having the direction of the surface vector Vf as the apex direction overlap. .

  As in the third mode, when a certain mesh is used as a determination target and another direction is viewed in the line-of-sight direction within the solid angle ψ from the representative point of the determination target mesh, If there is, it means that the mesh to be determined is surrounded by another mesh (wall), which means that there is a high possibility that air will stay.

  On the other hand, when the other direction is viewed from the determination target mesh within the range of the solid angle ψ, if there is no other mesh in only one direction (at least in one direction), the liquid infiltrates from the direction without the mesh. This means that the determination target mesh is immersed in the liquid, and the determination target mesh can be set as the initial mesh.

  In this case, in order to further increase the speed, it is desirable to narrow down meshes to be determined as initial meshes. Hereinafter, an example in which the determination target mesh is narrowed down according to the direction of the surface vector will be described. Specifically, as shown in FIG. 13, the determination target meshes are narrowed down by examining the magnitude of the angle θ formed by the direction of the surface vector Vf and the direction of gravity G, and the angle θ is set to a set angle (for example, , 90 °), only meshes satisfying the above condition are extracted and determined.

  That is, as shown in FIG. 13 (a), when the surface side of the mesh faces upward from the vertical, the angle θ is 90 ° or more, and as shown in FIG. 13 (b), the surface side of the mesh is vertical. When facing downward, the angle θ is less than 90 °. However, the mesh of θ <90 ° has a possibility that air stays and forms an air pocket. exclude.

  The initial setting program in the fourth mode is shown in FIG. In this program, in a first step S41, a certain surface mesh is selected as a determination target mesh from the surface meshes constituting the analysis model. In step S42, an angle θ between the surface vector direction of the determination target mesh and the gravity direction is calculated. In step S43, it is checked whether the angle θ is 90 ° or more.

  In step S43, if θ <90 °, the selected mesh is excluded from the determination target, the process returns to step S41, and the next determination target mesh is selected. If θ ≧ 90 °, the process proceeds from step S43 to step S44, where a solid angle ψg of a hemisphere having the representative point of the determination target mesh as the center and the direction opposite to the gravity direction as the apex direction, and the surface vector direction of the determination target mesh The angle in the range where the solid angle ψs of the hemisphere overlapping with the vertex direction is calculated as the solid angle ψ.

  Next, the process proceeds to step S45, where the other direction is looked up within the range of the solid angle ψ from the representative point of the determination target mesh. In step S46, it is determined whether there is a direction where no other mesh exists. Investigate. As a result, if the direction in which no other mesh exists within the range of the solid angle ψg is also one direction, the determination target mesh is set as the initial submerged mesh in step S47, and which direction is within the range of the solid angle ψ. If another mesh exists even when looking up, the determination target mesh is set as the initial liquid outside mesh in step S48.

  After the initial conditions are set in step S47 or step S48, the process proceeds to step S49, and it is checked whether or not the initial settings have been performed for all the surface meshes of the analysis model. If the initial settings for all surface meshes have not been completed, the process returns to step S41 to select another determination target mesh and repeat the above processing to complete the initial settings for all surface meshes. In this case, this program is terminated and the process proceeds to the air pocket determination calculation process (step S5 in FIG. 5) of the simulation program.

  In the fourth embodiment, the processing speed of the determination process can be improved by using the solid angle ψ obtained by narrowing down the solid angle ψg of the hemisphere centered on the representative point of the mesh as compared with the third embodiment. Further, prior to performing this determination process, it is possible to expect further improvement in processing speed by excluding meshes that may form air pockets in advance.

The basic block diagram of the simulation apparatus according to the first embodiment of the present invention. Same as above, schematic illustration of car body painting line Same as above, explanatory diagram showing setting of mesh to be free edge Same as above, explanatory diagram showing initial mesh selection conditions Same as above, air pocket simulation program flowchart Same as above, explanatory diagram showing simulation results Same as above, explanatory diagram showing simulation results considering plate thickness A flowchart of an air pocket simulation program according to the second embodiment of the present invention. Explanatory drawing which shows the setting of a solid angle according to 3rd Embodiment of this invention. Same as above, flowchart of initial setting program Explanatory drawing which shows the setting of a surface vector concerning 4th Embodiment of this invention. Same as above, explanatory diagram showing definition of solid angle Same as above, explanatory diagram showing angle created by surface vector and gravity vector Same as above, flowchart of initial setting program Explanatory drawing showing a solid part with a dent on the bottom Explanatory drawing showing an example of modeling the solid part of FIG. 7 with a surface mesh

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Simulation apparatus 10 Arithmetic apparatus 10a Model construction part 10b Initial mesh setting part 10c Air pocket determination part

Claims (8)

A computer that models the work to be dipped with data of multiple elements, and the computer determines whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity, and simulates air accumulation In the pool simulation method,
A model construction step of dividing the surface shape of the workpiece by a plurality of surface elements, and constructing an analysis model in which the plurality of surface elements are continuous on the entire surface of the workpiece;
A new element having a discontinuous part where the elements are not connected to each other is joined to the surface element having the highest height in the direction opposite to gravity in the above analysis model , and this new element is the initial element of the liquid attribute. an initial element setting step for setting as,
And the direction opposite position of gravity in the analytical model of any surface element attributes including the initial element has been determined, the analysis model other surface element adjacent to any surface element this attribute has been determined A determination step of comparing the position of the surface element in the opposite direction with gravity and determining the attribute of each surface element. A computer that models the work to be dipped with data of multiple elements, and the computer determines whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity, and simulates air accumulation In the pool simulation method,
A model construction step of dividing the surface shape of the workpiece by a plurality of surface elements, and constructing an analysis model in which the plurality of surface elements are continuous on the entire surface of the workpiece;
An initial element setting step of selecting an element whose normal direction of the surface element is equal to or greater than a set angle with respect to the gravitational direction from the analysis model,
The position of an arbitrary surface element having an attribute including the initial element in the direction opposite to gravity in the analysis model in the analysis model, and the analysis model of another surface element adjacent to the arbitrary surface element having the attribute determined A determination step for comparing the position of the surface element in the opposite direction and determining the attribute of each surface element;
A method for simulating an air pocket, comprising: A computer that models the work to be dipped with data of multiple elements, and the computer determines whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity, and simulates air accumulation In the pool simulation method,
A model construction step of dividing the surface shape of the workpiece by a plurality of surface elements, and constructing an analysis model in which the plurality of surface elements are continuous on the entire surface of the workpiece;
After setting the solid angle in the direction opposite to the gravity direction with the representative point of the surface element as the center, the element having no other surface element in the direction of at least one line of sight within the range of the solid angle is selected, and the liquid attribute An initial element setting step to set as an initial element of
The position of an arbitrary surface element having an attribute including the initial element in the direction opposite to gravity in the analysis model in the analysis model, and the analysis model of another surface element adjacent to the arbitrary surface element having the attribute determined A determination step for comparing the position of the surface element in the opposite direction and determining the attribute of each surface element;
A method of simulating an air pocket, comprising: After extracting an element whose normal direction of the surface element is equal to or larger than a set angle with respect to the direction of gravity, an element in which no other surface element exists in at least one line-of-sight direction within the range of the solid angle from the extracted elements 4. The method of simulating an air pocket according to claim 3 , wherein the initial element is selected. A computer that simulates air accumulation by modeling the work to be dipped with multiple element data and determining whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity. In the simulation program for air pockets,
A model construction step of dividing the surface shape of the workpiece by a plurality of surface elements, and constructing an analysis model in which the plurality of surface elements are continuous on the entire surface of the workpiece;
A new element having a discontinuous part where the elements are not connected to each other is joined to the surface element having the highest height in the direction opposite to gravity in the above analysis model , and this new element is the initial element of the liquid attribute. an initial element setting step for setting as,
And the direction opposite position of gravity in the analytical model of any surface element attributes including the initial element has been determined, the analysis model other surface element adjacent to any surface element this attribute has been determined And a determination step of determining the attribute of each surface element by comparing the position in the opposite direction with gravity in the above-mentioned computer . A computer that simulates air accumulation by modeling the work to be dipped with multiple element data and determining whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity. In the simulation program for air pockets,
A model construction step of dividing the surface shape of the workpiece by a plurality of surface elements, and constructing an analysis model in which the plurality of surface elements are continuous on the entire surface of the workpiece;
An initial element setting step of selecting an element whose normal direction of the surface element is equal to or greater than a set angle with respect to the direction of gravity from the analysis model, and setting as an initial element of a liquid attribute;
The position of an arbitrary surface element having an attribute including the initial element in the direction opposite to gravity in the analysis model in the analysis model, and the analysis model of another surface element adjacent to the arbitrary surface element having the attribute determined A determination step for comparing the position of the surface element in the opposite direction and determining the attribute of each surface element;
The computer executes the above, and a simulation program for air pockets. A computer that simulates air accumulation by modeling the work to be dipped with multiple element data and determining whether the attribute of each element is gas or liquid based on the positional relationship in the direction of gravity. In the simulation program for air pockets,
A model construction step of dividing the surface shape of the workpiece by a plurality of surface elements, and constructing an analysis model in which the plurality of surface elements are continuous on the entire surface of the workpiece;
After setting the solid angle in the direction opposite to the gravity direction with the representative point of the surface element as the center, the element having no other surface element in the direction of at least one line of sight within the range of the solid angle is selected, and the liquid attribute An initial element setting step to set as an initial element of
The position of an arbitrary surface element having an attribute including the initial element in the direction opposite to gravity in the analysis model in the analysis model, and the analysis model of another surface element adjacent to the arbitrary surface element having the attribute determined A determination step for comparing the position of the surface element in the opposite direction and determining the attribute of each surface element;
The computer executes the above, and a simulation program for air pockets. After extracting an element whose normal direction of the surface element is equal to or larger than a set angle with respect to the direction of gravity, an element in which no other surface element exists in at least one line-of-sight direction within the range of the solid angle from the extracted elements The air retention simulation program according to claim 7 , wherein: is selected and set as the initial element.

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