JP4522786B2 - Analysis method for fastened structures - Google Patents

Description

  The present invention models a structure in which an object to be tightened and a female screw member are fastened by a fastening member, and analyzes the force or deformation of each part when an external force is applied to the model of the structure. The present invention relates to a structure analysis method.

  A method for analyzing forces such as stress, surface pressure, axial force, etc., and deformation of each part when an external force is applied to a structure in which the object to be fastened and the female screw member are fastened by the fastening member Is realized by a computer in which various FEM analysis software using a finite element method (FEM) method has been installed.

  For example, as shown in FIG. 2, a structure 400 in which an object to be tightened 200 and a female screw member 300 are fastened by a bolt 100 is modeled, and material characteristics and the like of each element of the structure 400 are defined. Then, the force F1 is applied from outside. Thereby, the stress and deformation of each part of the structure 400 are calculated and displayed on the screen of the display.

  Here, there are Patent Documents 1 and 2 listed below as documents indicating the general technical level related to the present invention.

  In Patent Document 1, a virtual triangular pyramid-shaped contact element is formed between two objects, and a load such as heat or a load is applied to deform the contact element. Accordingly, a technique is described in which stress and deformation generated by contact between both objects are calculated.

Further, Patent Document 2 allows two objects to overlap each other, gives a load such as heat or load, obtains the distance between each node of the two objects, and according to the distance between nodes (overlap amount). A technique for calculating stress and deformation generated by contact between both objects is described.
JP-A-4-2200242 JP-A-9-145493

  However, if the structure 400 shown in FIG. 2 is given a calculation with an upward force F1 in the figure, for example, the bolt 100 is subjected to a load larger than the actual load applied to the bolt, such as the full load F1. In some cases, the results were different from the stresses and deformations generated in the structure.

The inventor considered the cause,
1) The initial tightening axial force generated when the bolt 100 is fastened is not taken into consideration.

2) No contact is defined between the object to be tightened 200 and the female screw member 300.

  I concluded that this is the cause.

  Here, Patent Documents 1 and 2 are techniques related to contact analysis between two general objects, and are specific phenomena that occur when an object to be tightened and a female screw member are fastened by a fastening member, that is, The initial tightening axial force is not considered.

  Moreover, when analyzing the fastened structure, it is required to perform high-accuracy analysis using existing software without extensive software modification or development of new software.

  The present invention has been made in view of such a situation, and when analyzing the force and deformation of each part of the fastened structure, the simulation result is highly accurate so that the simulation result accurately matches the behavior of the actual structure. It is an object of the present invention to make it possible to perform analysis easily and to perform analysis easily and in a short time using existing software.

The first invention is
The structure (40) in which the object to be tightened (20) and the female screw member (30) are fastened by the fastening member (10) is modeled, and each part when an external force is applied to the model (400) of this structure A method of analyzing a fastened structure that analyzes the force or deformation of
When modeling the fastening member (10), a beam (150) connected to the threaded portion (310) of the female screw member model (300), which is generated when the fastening member (10) is fastened. Forming a beam (150) which is displaced according to the tightening axial force;
Defining a coefficient of thermal expansion to impart a temperature load to the beam (150) of the fastening member model (100);
A temperature load corresponding to the initial fastening axial force is applied to the beam (150) of the fastening member model (100), and the beam is displaced according to the initial fastening axial force. An external force is applied to the structure model (400) to simulate the force or deformation of each part.

The second invention is the first invention,
At a position (C) where the initial tightening axial force is transmitted between the fastening member (10) and the female screw member (30), the screw part (310) and the point (142) of the female screw member model (300) are placed. A common bar (140) is formed, and the beam (150) in the first invention is connected to the bar (140).

The third invention is the first invention or the second invention,
A bar (160) that does not share the point (162) with the screw part (310) of the female screw member model (300) is formed at a position (D) corresponding to the lower neck tip of the fastening member (10). (160) is characterized in that the beam (150) in the first invention or the second invention is connected.

The fourth invention is
It is characterized by simulating after defining that the model (200) of the object to be tightened and the model (300) of the female screw member are in contact as separate volumes.

  The present invention will be described with reference to the drawings.

  First, the actual structure 40 shown in FIG. 1A is modeled as shown in FIG.

  FIG. 1B shows a modeled structure 400. The bolt model 100 is a beam connected to the threaded portion 310 of the female screw member 300, and the initial tightening that occurs when the bolt 100 is fastened. It is created by forming a beam 150 that is displaced according to the axial force. More specifically, a bar 140 sharing the point 142 with the screw portion 310 of the model of the female screw member 300 is formed at a position C where the initial tightening axial force is transmitted between the bolt 100 and the female screw member 300. By connecting the beam 150 to the bar 140, a model of the bolt 100 is created (second invention). More specifically, a bar 160 that does not share the point 162 with the screw part 310 of the model of the female screw member 300 is formed at a position D corresponding to the lower neck end of the bolt 100, and the beam 150 is connected to the bar 160. As a result, a model of the bolt 100 is created (third invention). In this way, the bolt 100 is created by a wire frame model, and is a simple structure model composed of lines, curves such as beams and bars, and points (nodes), and considers the “surface” of the structure. Compared to solid models, models can be created in a short time, easily and without skill, and the calculation load is small and calculation is performed in a short time without requiring memory capacity. Analysis efficiency.

  The coefficient of thermal expansion is defined for the beam 150 of the model of the bolt 100 in order to give a temperature load. The functions of defining the coefficient of thermal expansion and defining the temperature (setting the temperature) as the material properties of each element of the model are prepared as menus of existing software and can be used.

  In general, when a temperature load is applied to a structure, distortion (deformation) corresponding to the coefficient of thermal expansion and temperature occurs, and if the structure is an elastic body, an elastic force (Young's modulus) is applied when an external force is applied. ) And a distortion (deformation) corresponding to the rigidity determined by the shape occurs. The temperature load and the force load are the same in that the elements of the structure model are distorted.

  The initial tightening axial force is originally an axial force generated according to the actual tightening torque of the bolt 10 and is not a temperature load. However, in the analysis process, if it is handled as a temperature load, the operation is easier than when it is handled as a force load, and the distortion can be accurately reproduced. In other words, in order to give a force load, it is necessary to specify the part of the model where the force is applied and the direction of the force. To give a temperature load, the temperature of the entire model (after defining the coefficient of thermal expansion) All you need to do is give As a result, only the element having the coefficient of thermal expansion defined as the material property (only the beam 150 of the bolt 100) thermally expands, and the distortion of each part caused thereby is accurately reproduced.

  Further, it is defined that the model 200 of the object to be tightened and the model 300 of the female screw member are in contact as separate volumes. This “contact” menu is also provided in the existing software (fourth invention).

  Next, as shown in FIG. 1C, a temperature load corresponding to the initial tightening axial force is applied to the beam of the bolt model 100. Here, the coefficient of thermal expansion is defined for the beam 150 of the bolt 100, for example. If temperature is given to the entire model 400 of the structure, only the beam 150 of the bolt 100 whose coefficient of thermal expansion is defined as a material characteristic is thermally expanded, and distortion of each part due to the initial tightening axial force can be accurately reproduced.

  Next, as shown in FIG. 1 (d), an external force is applied to the structure model 400, and resistance (stress, surface pressure, etc.) or deformation (distortion) of each part of the structure model 400 is Simulate as resistance to external force of bolt. As a procedure of the analysis process, a temperature load (FIG. 1C) and an external force (FIG. 1D) may be applied simultaneously.

  FIG. 3 is a perspective view showing an actual test structure 40 used for comparison with the analysis result by the simulation of the embodiment.

  As shown in FIG. 3, a test structure 40 is formed by fastening an object to be tightened 20 and a female screw member 30 with a bolt 10 (fastening member).

  The bolt 10 is fastened through a washer 10a.

  In the following description, the actual structure 40, the bolt 10 constituting the structure 40, the object 20 to be tightened, and the female screw member 30, the structure 400 of the analysis model, the model of this structure (the model of the structure) ) In order to distinguish the bolt (model) 100, the object to be tightened (model) 200, and the female screw member (model) 300 constituting the 400, different reference numerals are used for description.

  FIG. 1 is a diagram showing the flow of analysis in this embodiment. FIG. 1 shows the fastened structure in a cross-sectional view.

  The analysis of the present embodiment can be performed using a computer in which existing FEM analysis software is installed. As the FEM analysis software, “MECANICA” (registered trademark), “ANSYS” (registered trademark), or the like can be used. In addition, the structure of an analysis apparatus can use general purpose things, such as a commercially available computer main body and the display connected to it, an input device (a mouse | mouth, a keyboard, etc.), a printer. Since the configuration is general, the illustration of the device configuration is omitted.

  First, the actual structure 40 shown in FIG. 1A is modeled as shown in FIG.

  FIG. 1B shows a modeled structure 400. The bolt model 100 is a beam connected to the threaded portion 310 of the female screw member 300, and the initial tightening that occurs when the bolt 100 is fastened. It is created by forming a beam 150 that is displaced according to the axial force. More specifically, a bar 140 sharing the point 142 with the screw portion 310 of the model of the female screw member 300 is formed at a position C where the initial tightening axial force is transmitted between the bolt 100 and the female screw member 300. By connecting the beam 150 to the bar 140, a model of the bolt 100 is created. More specifically, a bar 160 that does not share the point 162 with the screw part 310 of the model of the female screw member 300 is formed at a position D corresponding to the lower neck end of the bolt 100, and the beam 150 is connected to the bar 160. As a result, a model of the bolt 100 is created. In this way, the bolt 100 is created by a wire frame model, and is a simple structure model composed of lines, curves such as beams and bars, and points (nodes), and considers the “surface” of the structure. Compared to solid models, models can be created in a short time, easily and without skill, and the calculation load is small and calculation is performed in a short time without requiring memory capacity. Analysis efficiency.

  The coefficient of thermal expansion is defined for the beam 150 of the model of the bolt 100 in order to give a temperature load. The functions of defining the coefficient of thermal expansion and defining the temperature (setting the temperature) as the material properties of each element of the model are prepared as menus of existing software and can be used.

  In general, when a temperature load is applied to a structure, distortion (deformation) corresponding to the coefficient of thermal expansion and temperature occurs, and if the structure is an elastic body, an elastic force (Young's modulus) is applied when an external force is applied. ) And a distortion (deformation) corresponding to the rigidity determined by the shape occurs. The temperature load and the force load are the same in that the elements of the structure model are distorted.

  The initial tightening axial force is originally an axial force generated according to the actual tightening torque of the bolt 10 and is not a temperature load. However, in the analysis process, if it is handled as a temperature load, the operation is easier than when it is handled as a force load, and the distortion can be accurately reproduced. In other words, in order to apply a force load, it is necessary to specify the element to which the force is applied and the direction of the force, but in order to apply a temperature load, the temperature is applied to the entire model (after defining the coefficient of thermal expansion). All you have to do is As a result, only the element having the coefficient of thermal expansion defined as the material property (only the beam 150 of the bolt 100) thermally expands, and the distortion of each part caused thereby is accurately reproduced.

  Further, it is defined that the model 200 of the object to be tightened and the model 300 of the female screw member are in contact as separate volumes. This “contact” menu is also provided in the existing software.

  Next, as shown in FIG. 1C, a temperature load corresponding to the initial tightening axial force is applied to the beam of the bolt model 100. Here, the coefficient of thermal expansion is defined for the beam 150 of the bolt 100, for example. If temperature is given to the entire model 400 of the structure, only the beam 150 of the bolt 100 whose coefficient of thermal expansion is defined as a material characteristic is thermally expanded, and distortion of each part due to the initial tightening axial force can be accurately reproduced.

  Next, as shown in FIG. 1D, an external force is applied to the structure model 400 to simulate the force (stress, surface pressure, etc.) or deformation (distortion) of each part of the structure model 400. To do. As a procedure of the analysis process, a temperature load (FIG. 1C) and an external force (FIG. 1D) may be applied simultaneously.

  Hereinafter, the analysis procedure will be described in more detail.

(Creation of bolt 100 model)
4A and 4B show an actual bolt 10 and a bolt model 100 in comparison.

  As shown in FIG. 4A, the bolt 10 includes a bolt head 11 and a shaft portion 12 having a neck length L, and the shaft portion 12 has an effective diameter and an effective diameter of length a. It consists of the part 15, the process diameter part 16 which has a process diameter, and the screw part 16 in which the screw thread was formed.

  A stress (strain) gauge 13 is attached to a position away from the distance b from the position where the machining diameter starts. A position separated from the attachment position B of the stress gauge 13 by a distance c is a position C at which the initial tightening axial force is transmitted between the bolt 100 and the female screw member 300.

  In this embodiment, the model of the washer 10a is included in creating the bolt model 100.

  As shown in FIG. 4B, an arc-shaped bar 110 described later is formed at a position A corresponding to the bolt head 11 and the washer 10a. Below the arc-shaped bar 110 in the figure, a bolt head 11 and a beam 120, which will be described later, corresponding to the length L under the neck of the washer 10a are formed. The point 125 at the position where the machining diameter starts, the point 130 at the stress gauge attachment site B, the point 141 at the position C where the initial tightening axial force is transmitted between the bolt 100 and the female screw member 300, and the neck The point 161 at the position D corresponding to the tip is connected. An arc-shaped bar 140 described later is formed at a position C where the initial tightening axial force is transmitted between the bolt 100 and the female screw member 300. An arc-shaped bar 160 described later is formed at a position D corresponding to the tip under the neck. A beam 150 to be described later is formed as a point connecting a point 142 that connects the arc-shaped bars 140 and a point 162 that connects the arc-shaped bars 160 to each other.

  In making the model, the bolt diameter, neck length L, effective diameter, machining diameter, effective diameter portion length a, stress gauge attachment position b, washer 10a diameter, screw pitch, initial tightening axial force, etc. Data is prepared, and a bolt model 100 is created based on the data.

(1) Creation of bolt head and washer The model 100 of the bolt 10 (including the model of the washer 10a) is selected on the screen by selecting the “model creation” menu on the screen of the display connected to the computer body. It is created by performing the following processing.

  5A is a perspective view showing the positional relationship between the model of the bolt head 11 and the washer 10a and the model 200 of the member to be fastened, and FIG. 5B is a plan view of the model of the bolt head 11 and the washer 10a. It is shown in the figure.

  As shown in FIG. 5, an arc-shaped bar 110 corresponding to the washer 10a is formed along the circumferential direction of the bolt hole 210 of the model 200 to be tightened. The arc-shaped bar 110 is formed at a position corresponding to the diameter of the washer 10a. The arc-shaped bars 110 are connected to each other via points 111 corresponding to the respective positions on the outer periphery of the washer 10a.

  A point 112 corresponding to the hole center position of the bolt hole 210, a point 113 corresponding to the position of the effective diameter of the bolt 10, and a point 111 corresponding to the outer peripheral position of the washer 10a are arranged in the radial direction of the bolt hole 210. They are connected by radially extending radial bars 114. The points 111 and 113 are set to be points that share nodes with the model 200 of the object to be tightened.

(2) Calculation of the position C of the arc-shaped bar 140 (position C where the initial tightening axial force is transmitted between the bolt 100 and the female screw member 300) Next, the position C where the arc-shaped bar 140 is formed is calculated. Ask.

  FIG. 6A shows a positional relationship between the female screw member model 300 and the arc-shaped bar 140 in a perspective view, and FIG. 6B shows the same relationship in a cross-sectional view.

Here, when the bolt 10 is fastened, the female screw member 30 receives a load only at most three ridges from the beginning of the threaded portion of the female screw member 30. Therefore, at the position of 1.5 pitches in the center of the three mountains, as a reaction force of the initial tightening axial force,
d = (screw pitch) × 1.5
The position C corresponding to the distance d from the beginning of the screw portion 310 on the female screw member model 300 is set as a position where the arc-shaped bar 140 is formed.

  In order to receive the reaction force of the initial tightening axial force on the female screw member 300 side, the arc-shaped bar 140 is set to be a point sharing a node with the screw portion 310 on the model 300 side of the female screw member. The arc-shaped bar 140 is formed along the circumferential direction of the screw hole 320 of the female screw member model 300, and the arc-shaped bars 140 are formed on the screw portion 310 inside the screw hole 320 of the female screw member model 300. Thus, they are connected via points 142 corresponding to the respective positions on the inner periphery of the screw hole. This point 142 is also a node constituting the female screw member model 300 (solid model).

(3) Creation of Beam 120 Corresponding to Neck Length of Bolt 100 FIG. 7A shows the beam 120 corresponding to the neck length L of the bolt 10, the object 200 to be tightened, and the female screw member 300. The positional relationship is shown in a perspective view, and FIG. 7B is a side view of the beam 120.

  As shown in FIG. 7, the beam 120 is formed to a length corresponding to the neck length L of the bolt 10, and the beam 120 has a point 112 at the position A of the bolt head and a position where the machining diameter starts. The point 125, the point 130 at the stress gauge attachment site B, the point 141 at the position C where the initial tightening axial force is transmitted between the bolt 100 and the female screw member 300, and the position D corresponding to the tip under the neck The point 161 is formed as connected.

(4) Determination of the position of the beam 150 that gives a temperature load FIG. 8A is a perspective view showing the positional relationship among the screw hole 320 of the female screw member 300, the beam 120, the arc-shaped bar 140, and the arc-shaped bar 160. FIG. 8B shows the positional relationship among the beam 120, the arc-shaped bar 140, and the arc-shaped bar 160 in a perspective view. FIG. 8C shows the arc-shaped bar 160 in a plan view.

  An already created arc-shaped bar 140 is copied, and an arc-shaped bar 160 is formed at the tip position (neck tip position) D of the beam 120. The arc-shaped bars 160 are connected by a point 162.

  Next, a radial bar 163 extending radially in the radial direction of the screw hole 320 from the point 161 at the lower neck position D of the beam 120 is formed and connected to the point 162 that connects the arc-shaped bars 160 to each other.

  Here, it is important that, as described above, the point 142 of the arc-shaped bar 140 is created so as to share the point with the female screw member model 300 in order to receive the reaction force of the initial tightening axial force. As described later, the point 162 of the arc-shaped bar 160 is created so as not to share the point with the female screw member model 300 in order to extend the beam 150 according to the temperature load as described later. For this reason, it is necessary to create a model (solid model) of the female screw member model 300 first, cut the mesh, and then create this beam.

(5) Creation of Beam 150 that Gives Temperature Load Next, as shown in FIG. 9, a point 142 that connects the arc-shaped bars 140 and a point 162 that connects the arc-shaped bars 160 are connected by the beam 150. To do. Since the point 162 is not shared with the point on the female screw member 300 side, when a temperature load is applied to the beam 150, the beam 150 is largely restrained according to the temperature load without being constrained by the female screw member 300 ( Will grow).

  The bolt model 100 is created as described above.

(Definition of material properties)
Next, a menu for defining “material properties” is selected on the display, and a process for defining material properties for each element of the bolt model 100 is executed.

  As indicated by an arrow in FIG. 10A, an arc-shaped bar 110 (radial bar 114) corresponding to the bolt head 11 is designated on the screen, and an arc-shaped bar corresponding to the bolt tip (screw portion 16). Bar 140 and arc-shaped bar 160 (radial bar 163) are designated on the screen, and the designated elements are set to be rigid bodies. For example, as shown in FIG. 10B, the Young's modulus and density are set to very large values in order to treat them as rigid bodies.

  Next, the material properties of each part of the beam 120 are defined.

  For example, as shown in FIG. 11, the material (“iron”), Young's modulus, and density of each part of the beam 120 are set.

  Next, the material properties of the beam 150 to be subjected to a temperature load are defined.

  That is, a beam 150 that gives a temperature load is designated on the screen as shown by an arrow in FIG. 12A, and the temperature expansion coefficient of the designated beam 150 is set as shown in FIG. 12B. On the other hand, since the beam 150 is not distorted by a load due to force, it is treated as a rigid body, and Young's modulus and density are set to very large values.

(Definition of contact)
Next, it is defined that the model 200 of the object to be tightened and the model 300 of the female screw member are in contact as separate volumes.

  That is, as shown by an arrow in FIG. 13, a contact surface 250 between the object 200 to be tightened and the female screw member 300 is designated on the screen, and both models 200 and 300 are in contact as separate volumes on the contact surface 250. Define what you are doing. When creating the structure model 400, it is not necessary to create a gap between the object to be tightened 200 and the female screw member 300.

  14A shows the contact surface 250 in a perspective view, and FIG. 14B shows the contact surface 250 in an enlarged plan view.

  FIG. 14 (b) shows the contact surface 250 made without using extruded solids or symmetry. Ideally, the elements of the contact surface 250 are symmetrical using extrusion or rotation to create a solid. However, calculation may be difficult due to an increase in the number of elements and the contact area. Therefore, it is desirable to divide a small element to some extent even only in the contact surface 250 (solid surface).

(Grant temperature load)
Next, as shown in FIG. 1C, a temperature load corresponding to the initial tightening axial force is applied to the beam 150 of the bolt model 100. Here, as described above, for example, the coefficient of thermal expansion is defined in the beam 150 of the bolt 100 as one of the parameters of the temperature load. Therefore, if temperature is applied to the entire model 400 of the structure, only the beam 150 of the bolt 100 whose coefficient of thermal expansion is defined as a material characteristic is thermally expanded, and distortion corresponding to the initial tightening axial force is generated. Specifically, as shown in FIG. 15, a command for giving a temperature difference ΔT (for example, 1000 ° C.) with respect to the initial set temperature (for example, 0 ° C.) to the structure 400 on the display screen. Entered. When the temperature difference ΔT is input, the axial force F corresponding to the temperature difference ΔT is displayed on the screen.

  The target temperature (target temperature difference) ΔT corresponding to the initial tightening axial force (target axial force F) can be obtained by the following equation.

Target temperature ΔT = target axial force F × temporary temperature ΔT ′ / temporary axial force F ′ (1)
Therefore, first, an appropriate temporary temperature ΔT ′ is input to acquire the temporary axial force F ′ on the screen. Next, the obtained temporary axial force ΔF ′, temporary temperature ΔT ′, and target axial force F (known value) are input to the above equation (1) to calculate the target temperature T.
When the calculated target temperature T is given again as a command, the beam 150 of the bolt 100 thermally expands according to the initial fastening axial force F, and the portion fastened by the bolt 100 is deformed accordingly.

  16 shows a side view of the deformation of the bolt 100, FIG. 16 (a) shows a state before the initial fastening axial force F is applied, and FIG. 16 (b) shows the initial fastening axial force F. It is the state after giving.

As shown in FIG. 16, when the initial tightening axial force F is applied, the arc-shaped bar 110 corresponding to the bolt head 11 and the washer 10 a is displaced by λA in a direction slightly biting into the object 200 to be tightened. In addition, the beam 150 corresponding to the lower end of the bolt neck is greatly displaced (elongated) by λB. That is, the arc-shaped bar 140 is displaced in a direction in which the female screw member 300 is pressed against the object 200 to be tightened, and the arc-shaped bar 160 is displaced in the depth direction of the screw hole 320 of the female screw member 300. The elongation λb of the bolt 100 is
λb = λB-λA
λA: Displacement in the axial direction of the bolt neck base (mm)
λB: Displacement in the axial direction of the bolt neck tip (mm)
As required. The elongation amount λb of the bolt 100 is displayed on the screen of the display.

  The temperature load (target temperature ΔT) may be applied simultaneously with the following external force.

(Applying external force)
Next, as shown in FIG. 1D, an external force is applied to the structure model 400 to simulate the force (stress, surface pressure, etc.) or deformation (distortion) of each part of the structure 400 model. To do. The direction and magnitude of the external force can be set by an input means such as a mouse.

  FIG. 17A shows a result of applying an external force after applying an initial tightening axial force F. FIG. The result of applying the external force is displayed on the display screen. FIG. 17A shows the state of deformation and stress distribution of each part of the structure 400 by brightness difference (lightness / darkness).

  The simulation result shown in FIG. 17A coincided with the test result of the test structure 40. Further, when the stress (strain) at the point 130 corresponding to the stress gauge attachment site B in the bolt model 100 and the stress (strain) detected by the stress gauge 13 attached to the actual bolt 10 were compared, It was confirmed that both of them almost coincided and the stress applied to the actual bolt 10 was accurately simulated.

  FIG. 17B shows a simulation result when the bolt 100 ′ is made of a solid model as a comparative example. FIG. 17B shows the result of applying the external force after applying the initial tightening axial force F, similarly to FIG. 17A.

  Comparing FIG. 17A and FIG. 17B, it can be seen that the deformation state of each part of the structure 400 and the stress distribution of each part are substantially the same. In other words, it has been confirmed that the present embodiment in which the bolt is created by the wire frame model can perform a highly accurate simulation with less labor than the case of creating the bolt by the solid model.

  FIG. 18 shows a comparison between a bench test result of the test structure 40 and a simulation result (calculation result) of the structure model 400. The horizontal axis in FIG. 18 is the displacement (mm) of the bolt and the object to be tightened, and the vertical axis is the axial force F (t). L1 indicates the simulation result of the bolt 100, and L2 indicates the simulation result of the object 200 to be tightened. L3 indicates the bench test result of the bolt 10, and L4 indicates the bench test result of the object 20 to be tightened. As can be seen from FIG. 18, it was confirmed that the simulation result almost coincided with the bench test result.

  By the way, each part of the construction machine is fastened using fastening members such as bolts. Therefore, the present invention may be applied to determine whether or not the strength of each component at the fastening site of the construction machine is appropriate.

  FIG. 19A is a perspective view showing a fastening portion of the arm 40 (structure) of the construction machine, and FIG. 19B is a cross-sectional view thereof.

  As shown in FIG. 19, the bracket 20 (object to be tightened), the bracket 30 and the nut 30a (female screw member) are fastened by a bolt 10 and a washer 10a (fastening member). A bucket (not shown) is attached to the tip of the arm 40. When performing the “pressing operation” of pressing the bucket against the ground or a fixed object, it is predicted that high stress is generated in the bracket fastening bolt 10 and the fastening portion of the arm 40 is greatly displaced. Therefore, a structure (arm) model 400 is created in the same manner as in the above-described embodiment, and simulation is performed in which an external force corresponding to a pressing operation is applied to the arm 40 after applying an initial tightening axial force, and an actual construction machine From the simulation results, it was determined whether or not the size of the bolts 10 and the plate thicknesses of the brackets 20 and 30 used in the above were appropriate.

FIG. 20 shows a comparison between an experimental result of the arm 40 and a simulation result (calculation result) of the arm model 400. The horizontal axis in FIG. 20 is the bolt stress (N / mm ² ), and the vertical axis is the axial force F (N). L5 shows the simulation result of the bolt 100, and L6 shows the simulation result of the bracket 200. L7 shows the experimental result of the bolt 10, and L8 shows the experimental result of the bracket 20. As can be seen from FIG. 20, it was confirmed that the simulation results almost coincided with the experimental results.

  FIG. 21 shows, as a simulation result, the stress distribution of each part of the fastening portion of the arm 40 by the brightness difference.

  FIG. 22 shows the distribution of surface pressure on the fastening surface (contact surface) of the bracket 200 by the brightness difference. FIG. 22A shows the surface pressure distribution in a state where an initial tightening axial force is applied but no external force (the pressing force by the bucket) is applied, and FIG. 22B shows the external force applied. It is a surface pressure distribution in a state.

  By applying an external force as indicated by an arrow G in FIG. 22B, the surface pressure is reduced around the bolt hole 210A of the fastening surface 200A on one side (upper side in the figure) of the bracket 200 (lightness) It can be seen that the surface pressure is large (low brightness) on the fastening surface 200B on the opposite side (lower side in the figure). In FIG. 21, the corresponding part is indicated by an arrow G. It was confirmed from the simulation results that the deformation (part indicated by the arrow G) in which the bracket 300 is separated occurs in the fastening surface 200A on one side of the bracket 200 by performing the pressing operation of the bucket in this way. For this reason, from the simulation results, it was possible to accurately obtain an appropriate size of the bolt 10 and an appropriate thickness of the brackets 20 and 30 so that such deformation does not occur.

  In the embodiment, the beam 150 for applying a temperature load is a beam connecting the arc-shaped bar 140 and the arc-shaped bar 160. However, this is an example, and the model of the tip of the bolt has the configuration shown in FIG. It may be a model.

  That is, FIGS. 23A and 23B are perspective views showing a model of a bolt tip before and after thermal expansion. The model shown in FIG. 23 is the same as the model of the above-described embodiment (FIG. 9) in that the arc-shaped bar 140 and the beam 150 that gives a temperature load are used, but the beam 150 is the point of the arc-shaped bar 140. 142 and the point 161 at the tip of the beam 120 are connected, and the arc-shaped bar 160 (see FIG. 9) corresponding to the bolt neck lower tip D is omitted.

  FIGS. 24A and 24B show the state of the structure 400 before the temperature load is applied and the state of the structure 400 after the temperature load is applied, respectively, similarly to FIGS. 1B and 1C. Is shown in a sectional view. As can be seen from FIGS. 24 (a) and 24 (b), even when the bolt tip model having the configuration shown in FIG. 23 is used, the bolt tip is the same as in FIGS. 1 (b) and 1 (c). It was confirmed that the phenomenon of stretching according to the tightening axial force was faithfully reproduced, and the force and deformation of each part of the structure 400 could be accurately simulated.

  In the present invention, not only the structure fastened by the fastening member but also the structure press-fitted by the press-fitting member can be subjected to the same accurate analysis by performing the same process as described above.

FIGS. 1A, 1 </ b> B, 1 </ b> C, and 1 </ b> D are diagrams illustrating a model creation procedure and an analysis procedure using the model according to the embodiment. FIG. 2 is a diagram used for explaining the prior art, and shows a state in which a force is applied to a model of a structure. FIG. 3 is a perspective view showing a test structure used for comparison with the analysis result by the simulation of the embodiment. FIGS. 4A and 4B are diagrams showing a comparison between an actual bolt and a bolt model. FIG. 5A is a perspective view showing the positional relationship between the bolt head and washer model and the model of the fastened member, and FIG. 5B is a plan view showing the bolt head and washer model. . 6A is a perspective view showing the positional relationship between the female screw member model and the arc-shaped bar, and FIG. 6B is a cross-sectional view showing the same relationship. FIG. 7A is a perspective view showing a positional relationship between a beam corresponding to the length under the bolt neck, an object to be tightened, and a female screw member, and FIG. 7B is a side view of the beam. . FIG. 8A is a perspective view showing a positional relationship among a screw hole of the female screw member, a beam corresponding to the bolt neck, an arc-shaped bar below the bolt neck, and an arc-shaped bar below the bolt neck. FIG. 8B is a perspective view showing the positional relationship among a beam corresponding to the bolt neck, an arc-shaped bar below the bolt neck, and an arc-shaped bar below the bolt neck. c) is a plan view showing an arc-shaped bar below the bolt neck. FIG. 9 is a view showing a state in which a point connecting the arc-shaped bars below the bolt neck and a point connecting the arc-shaped bars below the bolt neck are connected by a beam to which a temperature load is applied. It is. FIG. 10A shows an arc-shaped bar (radial bar) corresponding to the bolt head, an arc-shaped bar below the neck corresponding to the bolt tip (screw portion), and a circle below the neck. An arc-shaped bar (radial bar) is specified, and these specified elements are set as rigid bodies. FIG. 10 (b) shows that Young's modulus and density are very high for handling as a rigid body. It is a figure which shows being set to a big value. FIG. 11 is a diagram illustrating that the material (“iron”), Young's modulus, and density of each part of the beam corresponding to the bolt neck are set. FIG. 12A is a diagram illustrating a state in which a beam that applies a temperature load is designated, and FIG. 12B is a diagram illustrating that a temperature expansion coefficient is defined for the designated beam. FIG. 13 is a diagram for explaining that the contact surface between the object to be tightened and the female screw member is designated, and it is defined that both models are in contact as separate volumes on the contact surface. FIG. 14A is a perspective view showing a contact surface, and FIG. 14B is an enlarged plan view showing the contact surface. FIG. 15 is a diagram for explaining how a temperature difference with respect to the currently set temperature is given as a command to the structure on the display screen. FIG. 16A is a diagram illustrating a state before the initial tightening axial force is applied, and FIG. 16B is a diagram illustrating a state after the initial tightening axial force is applied. FIG. 17A is a diagram showing a result of applying an external force after giving an initial tightening axial force, and FIG. 17A shows a state of deformation and stress distribution of each part of the structure with a lightness difference (light / dark). FIG. 17B is a diagram showing a simulation result when a bolt is created with a solid model as a comparative example. FIG. 18 is a graph showing a comparison between the bench test result of the test structure and the simulation result (calculation result) of the model of the structure. FIG. 19A is a perspective view showing a fastening portion of an arm (structure) of a construction machine, and FIG. 19B is a cross-sectional view thereof. FIG. 20 is a graph showing a comparison between the experimental result of the arm and the simulation result (calculation result) of the arm model. FIG. 21 is a diagram showing, as a simulation result, the stress distribution of each part of the fastening portion of the arm with a brightness difference. FIG. 22 is a diagram showing the distribution of surface pressure of the fastening surface (contact surface) of the bracket in terms of brightness difference, and FIG. 22 (a) is a diagram showing the surface pressure distribution when an initial tightening axial force is given, FIG. 22B is a diagram showing a surface pressure distribution when an external force is further applied. 23A and 23B are perspective views showing a model of a bolt tip before and after thermal expansion. 24 (a) and 24 (b) are diagrams for explaining changes when a temperature load is applied to the model of the bolt tip shown in FIG. 23. FIG. FIG. 23B is a cross-sectional view showing the state of the structure after applying a temperature load.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fastening member (bolt, washer) 20 Object to be tightened 30 Female screw member 40 Structure 100 Model of fastening member (bolt washer) 200 Model of object to be tightened 300 Model of female screw member 400 Model of structure 150 Temperature load Beam to give 250 contact surface

Claims (4)

The structure (40) in which the object to be tightened (20) and the female screw member (30) are fastened by the fastening member (10) is modeled, and each part when an external force is applied to the model (400) of this structure A method of analyzing a fastened structure that analyzes the force or deformation of
When modeling the fastening member (10), the beam (150) is connected to the threaded portion (310) of the female screw member model (300), and is an initial stage generated when the fastening member (10) is fastened. Forming a beam (150) which is displaced according to the tightening axial force;
Defining a coefficient of thermal expansion to impart a temperature load to the beam (150) of the fastening member model (100);
A temperature load corresponding to the initial fastening axial force is applied to the beam (150) of the fastening member model (100), and the beam is displaced according to the initial fastening axial force. An external force is applied to the structure model (400) to simulate the force or deformation of each part of the structure model (400). At a position (C) where the initial tightening axial force is transmitted between the fastening member (10) and the female screw member (30), the screw part (310) and the point (142) of the female screw member model (300) are placed. 2. A method of analyzing a fastened structure according to claim 1, wherein a shared bar (140) is formed, and the beam (150) according to claim 1 is connected to the bar (140). . A bar (160) that does not share the point (162) with the screw part (310) of the female screw member model (300) is formed at a position (D) corresponding to the lower neck tip of the fastening member (10). The beam (150) according to claim 1 or 2 is coupled to (160). The method for analyzing a fastened structure according to claim 1 or 2. The fastening method according to claim 1, wherein the fastening target model (200) and the female screw member model (300) are defined as contacting each other as separate volumes and then simulated. Method of analyzing the structure.

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