Tapered thread loosening evaluation method, evaluation device, and program

Abstract

Provided are a tapered thread loosening evaluation method, an evaluation device, and a program for evaluating loosening of tapered threads in a connection structure using the tapered threads.　This tapered thread loosening evaluation method is for evaluating loosening in a connection structure in which a first columnar body having a first tapered female thread portion and a second columnar body having a second tapered female thread portion are connected with a joint body having a first tapered male thread portion and a second tapered male thread portion. The method causes a computer to execute: a step of specifying thread dimensions; a step of creating a drawing of a two-dimensional model of the connection structure on the basis of the specified thread dimensions; a step of giving boundary conditions; a step of performing an analysis on the basis of the two-dimensional model and the boundary conditions; and a step of evaluating frictional forces from the analysis result.

Description

Tapered screw loosening evaluation method, evaluation device, and program

[0001] This invention relates to a method, apparatus, and program for evaluating tapered screw loosening.

[0002] Patent Document 1 discloses a graphite electrode comprising a pole having a female threaded socket at its end and a male threaded nipple that can be fastened to the socket.

[0003] Japanese Patent Publication No. 2022-142242

[0004] The present invention provides a tapered screw loosening evaluation method, evaluation apparatus, and program for evaluating the loosening of tapered screws in a connecting structure using tapered screws.

[0005] To solve the above problems, according to one embodiment, a tapered screw loosening evaluation method is provided for evaluating loosening in a connecting structure in which a first column having a first tapered female thread portion and a second column having a second tapered female thread portion are connected by a joint body having a first tapered male thread portion and a second tapered male thread portion, wherein the method causes a computer to perform the steps of: specifying screw dimensions; drawing a two-dimensional model of the connecting structure based on the specified screw dimensions; providing boundary conditions; performing an analysis based on the two-dimensional model and the boundary conditions; and evaluating frictional force from the results of the analysis.

[0006] According to the present invention, a tapered screw loosening evaluation method, evaluation apparatus, and program can be provided for evaluating the loosening of tapered screws in a connecting structure using tapered screws.

[0007] This is a hardware configuration diagram of the evaluation device. This is a side view of the assembled electrode. This is a side view of the disassembled electrode. This is an example of a schematic cross-sectional diagram illustrating the fitting state in the first column, the first joint, and the second column. This is a diagram illustrating various dimensions of the tapered screw. This is a flowchart illustrating an evaluation method for evaluating the loosening of the tapered screw in a connecting structure. This is an example of a parameter interface. This is an example of an interface for displaying a set mathematical formula. This is an example of a parameter interface with input values. This is a flowchart illustrating a two-dimensional model generation method. This is an example of the right half of a symmetrical two-dimensional axial model created in step S201. This is an example of a two-dimensional model created in step S202. This is an example of a two-dimensional model created in step S203. This is an example of a two-dimensional model created in step S204. This is an example of a two-dimensional model created in step S205. This is an example of a magnified view of the geometry of the second tapered male thread and the geometry of the second tapered female thread in the two-dimensional model created in step S205. This is an example of a two-dimensional model of a connecting structure using a tapered screw. This is a schematic diagram illustrating a two-dimensional model that reproduces the axial force generated in the first joint. This is a schematic diagram illustrating a two-dimensional model that reproduces the axial force generated in the first joint. This is a schematic diagram showing frictional force in a connecting structure using tapered threads. This is a schematic diagram showing frictional force in a connecting structure using tapered threads. This is a schematic diagram showing frictional force in a connecting structure using tapered threads. This is an example of a graph showing test results and simulation results for loosening evaluation of a connecting structure. This is an example of a graph showing test results and simulation results for loosening evaluation of a connecting structure.

[0008] Various exemplary embodiments will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals.

[0009] <Evaluation Device> First, an example of the configuration of the evaluation device 10 will be explained using Figure 1. Figure 1 is a hardware configuration diagram of the evaluation device 10. The evaluation device 10 has a CPU (Central Processing Unit) 1, a ROM (Read Only Memory) 2, and a RAM (Random Access Memory) 3. The CPU 1, ROM 2, and RAM 3 form what is known as a computer. The evaluation device 10 may also have an auxiliary storage device 4, a display device 5, an operating device 6, an I / F (Interface) device 7, and a drive device 8. Each piece of hardware in the evaluation device 10 is interconnected via bus B.

[0010] The CPU 1 (control unit) is a computing device that executes various programs installed in the auxiliary storage device 4.

[0011] ROM2 is non-volatile memory. ROM2 functions as a main memory device that stores various programs, data, etc., necessary for the CPU1 to execute the various programs installed on the auxiliary storage device 4. Specifically, ROM2 functions as a main memory device that stores boot programs such as the BIOS (Basic Input / Output System) and EFI (Extensible Firmware Interface).

[0012] RAM3 is a volatile memory such as DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access Memory). RAM3 functions as a main memory device that provides a working area that is expanded when various programs installed on the auxiliary storage device 4 are executed by the CPU 1.

[0013] The auxiliary storage device 4 is an auxiliary storage device that stores various programs and information used when various programs are executed.

[0014] Display device 5 is a display device that displays the internal state of the evaluation device 10, etc.

[0015] The operating device 6 is an input device that allows the operator of the evaluation device 10 to input various instructions to the evaluation device 10.

[0016] The I / F device 7 is a communication device that connects to a network and communicates with other devices.

[0017] The drive device 8 is a device for setting the storage medium 9. The storage medium 9 here includes media that record information optically, electrically, or magnetically, such as CD-ROMs, flexible disks, and magneto-optical disks. The storage medium 9 may also include semiconductor memory that records information electrically, such as EPROM (Erasable Programmable Read Only Memory) and flash memory.

[0018] The various programs to be installed on the auxiliary storage device 4 are installed, for example, when the distributed storage medium 9 is set in the drive device 8 and the various programs recorded on the storage medium 9 are read by the drive device 8. Alternatively, the various programs to be installed on the auxiliary storage device 4 may be installed by downloading them from the network via the I / F device 7.

[0019] The evaluation device 10 functions as a CAD (Computer-aided design) device when a program is executed. This allows the operator to input various information to the evaluation device 10 via the control device 6, etc., and the evaluation device 10 generates a two-dimensional model (2D CAD data) with multiple geometries based on the input information. Furthermore, the evaluation device 10 functions as a CAE (Computer-Aided Engineering) device when a program is executed. This allows the evaluation device 10 to evaluate the loosening of tapered screws in a connecting structure using tapered screws based on the created two-dimensional model.

[0020] <Electrodes> Next, the structure of the electrode 20, from which a two-dimensional model is generated by the evaluation device 10, will be explained using Figures 2 to 5. Figure 2 is a side view of the assembled electrode 20. Figure 3 is a side view of the disassembled electrode 20.

[0021] The electrode 20 shown in Figure 2 is a graphite electrode used, for example, in an electric furnace for steelmaking to melt iron scrap.

[0022] As shown in Figures 2 and 3, the electrode 20 has a first column 21, a first joint 22, a second column 23, a second joint 24, and a third column 25. That is, the electrode 20 has a connecting structure in which multiple column bodies (21, 23, 25) are connected by joint bodies (22, 24). Although the electrode 20 is described using a structure in which three column bodies (21, 23, 25) are connected as an example, it is not limited to this, and it may also be a structure in which two column bodies are connected, or a structure in which four or more column bodies are connected.

[0023] The first columnar body 21, the second columnar body 23, and the third columnar body 25 are cylindrical members and are formed from a solid composition mainly composed of graphite.

[0024] A frustoconical recess is formed on the end face (bottom face in Figures 2 and 3) of the first column 21. A first tapered female thread is formed on the inner circumferential surface of this recess. This first tapered female thread engages with one of the tapered male threads of the first joint body 22 (the tapered male thread formed on the upper frustoconical surface).

[0025] Furthermore, a frustoconical recess is formed on one end face of the second column 23 (the upper surface in Figures 2 and 3). A second tapered female thread is formed on the inner circumferential surface of this recess. This second tapered female thread engages with the other tapered male thread of the first joint body 22 (the tapered male thread formed on the lower frustoconical surface).

[0026] Similarly, a frustoconical recess is formed on the other end face of the second column 23 (the bottom face in Figures 2 and 3). A third tapered female thread is formed on the inner circumferential surface of this recess. This third tapered female thread engages with one of the tapered male threads of the second joint body 24 (the tapered male thread formed on the upper frustoconical surface).

[0027] Furthermore, a frustoconical recess is formed on the end face (upper surface in Figures 2 and 3) of the third column 25. A fourth tapered female thread is formed on the inner circumferential surface of this recess. This fourth tapered female thread engages with the other tapered male thread of the second joint body 24 (the tapered male thread formed on the lower frustoconical surface).

[0028] The first joint body 22 and the second joint body 24 are members having a shape in which two frustoconical shapes are joined together at their bases (the base with the larger radius), and are formed from a solid composition mainly composed of graphite.

[0029] One frustoconical side surface of the first joint body 22 has a tapered male thread (first tapered male thread) that engages with the first tapered female thread of the first column 21. The other frustoconical side surface of the first joint body 22 has a tapered male thread (second tapered male thread) that engages with the second tapered female thread of the second column 23.

[0030] The tapered male thread (first tapered male thread) on one end of the first joint body 22 and the tapered male thread (second tapered male thread) on the other end of the first joint body 22 are formed with the same tapered male thread dimensions. Also, the first tapered female thread of the first column 21 and the second tapered female thread of the second column 23 are formed with the same tapered female thread dimensions.

[0031] Similarly, one frustoconical side surface of the second joint body 24 has a tapered male thread (third tapered male thread) that engages with the third tapered female thread of the second column 23. Furthermore, the other frustoconical side surface of the second joint body 24 has a tapered male thread (fourth tapered male thread) that engages with the fourth tapered female thread of the third column 25.

[0032] One of the tapered screws (the third tapered screw) of the second joint body 24 and the other tapered screw (the fourth tapered screw) of the second joint body 24 are formed with the same dimensions of the tapered screw. Also, the third tapered screw of the second column body 23 and the fourth tapered screw of the third column body 25 are formed with the same dimensions of the tapered screw.

[0033] When the electrode 20 is shipped, as shown in FIG. 3, the electrode 20 is shipped in a state where the first column body 21, the second column body 23, and the third column body 25 are disassembled.

[0034] Here, when the electrode 20 is shipped, one of the tapered screws (the first tapered screw) of the first joint body 22 is tightly tightened to the first tapered screw of the first column body 21. That is, the electrode 20 is shipped in a state where the first joint body 22 is attached to the first column body 21.

[0035] Similarly, when the electrode 20 is shipped, one of the tapered screws (the third tapered screw) of the second joint body 24 is tightly tightened to the third tapered screw of the second column body 23. That is, the electrode 20 is shipped in a state where the second joint body 24 is attached to the second column body 23.

[0036] When the electrode 20 is used in an electric furnace for steelmaking, as shown in FIG. 2, the electrode 20 is connected with the first column body 21, the second column body 23, and the third column body 25. That is, the first column body 21 and the second column body 23 are connected by screwing the other tapered screw (the second tapered screw) of the first joint body 22 and the second tapered screw of the second column body 23. Also, the second column body 23 and the third column body 25 are connected by screwing the other tapered screw (the fourth tapered screw) of the second joint body 24 and the fourth tapered screw of the third column body 25.

[0037] FIG. 4 is an example of a schematic cross-sectional view for explaining the fitting state among the first column body 21, the first joint body 22, and the second column body 23.

[0038] In the state where the electrode 20 is assembled (see Fig. 2), as shown in Fig. 4, the first tapered screw of the first column body 21 and one tapered female screw of the first coupling body 22 are in a state of contacting on both sides of the thread. In contrast, the second tapered screw of the second column body 23 and the other tapered female screw of the first coupling body 22 are in a state of contacting only on one side of the thread.

[0039] Next, various dimensions of the tapered screw will be described using Fig. 5. Fig. 5 is a diagram for explaining various dimensions of the tapered screw.

[0040] "l ４ " is the length of the first coupling body 22. The length of one tapered female screw (the first tapered female screw) of the first coupling body 22 is "l １ / 2". "l ２ " is the length of the tapered screw of the first column body 21. "l ３ " is the effective length of the tapered screw. "l ４ " is the relief length of the tapered screw. "l ５ " is the relief length of the tapered screw.

[0041] "d １ " is the maximum diameter of the tapered female screw. "d ２ " is the effective diameter of the tapered female screw (the diameter obtained by subtracting half the thread height from the thread of the maximum diameter). "d ３ " is the inner diameter of the tapered screw. "d ４ " is the effective diameter of the tapered screw (the diameter obtained by subtracting half the thread height from the thread of the maximum diameter).

[0042] <Evaluation of loosening of tapered threads in a connecting structure using tapered threads> Next, an evaluation method for evaluating the loosening of tapered threads in a connecting structure using tapered threads (for example, a connecting structure in the first column 21, the first joint body 22, and the second column 23) will be explained using Figures 6 to 20B. Figure 6 is a flowchart illustrating the evaluation method for evaluating the loosening of tapered threads in a connecting structure. Here, the evaluation device 10 generates a two-dimensional model (2D CAD data) of a cross-sectional view cut along the central axis of the electrode 20 in the connecting structure in the first column 21, the first joint body 22, and the second column 23 (steps S101 to S104 described later). Then, the evaluation device 10 evaluates the loosening of tapered threads in the connecting structure using tapered threads based on the created two-dimensional model (steps S105 to S110 described later).

[0043] In step S101, the effective diameter of the male thread, the number of threads, the thread count, and the difference in effective diameter between the male and female threads are parameterized. The effective diameter of the male thread, the number of threads, the thread count, and the difference in effective diameter between the male and female threads are dimensions that define the shape of the screw, and in the following explanation, they will be collectively referred to as "screw dimensions." Note that the screw dimensions may include the taper angle. Here, the CPU 1 makes the evaluation device 10 function as a CAD device by executing a program installed in the auxiliary storage device 4, etc. By executing a program installed in the auxiliary storage device 4, etc., the CPU 1 parameterizes (variables) the information among the various pieces of information in the connection structure that will be specified as arbitrary values ​​in step S103, which will be described later. In one example, as shown in Figure 6, the "effective diameter of the male thread," "number of threads," "thread count," and "difference in effective diameter between the male and female threads" are parameterized.

[0044] Here, "effective diameter of the male thread" refers to the effective diameter d of the tapered male thread shown in Figure 5. ２ That is the case.

[0045] Furthermore, one tapered male thread (first tapered male thread) and the other tapered male thread (second tapered male thread) have the same shape, and the number of threads on the tapered male threads are also formed to be the same. Note that instead of "number of threads," the "length of the male thread" (as shown in Figure 5) is used. １) may be parameterized. In this case, the number of threads may be calculated from the length of the male thread based on pre-set information such as the screw pitch.

[0046] "Thread clearance" is the length from the end face to the start of thread cutting, and is the length of the relief l of the tapered male thread shown in Figure 5. ４ and the relief length l of the tapered female thread ５ That is the case.

[0047] The "difference in effective diameter between male and female threads" is the effective diameter d of the tapered male thread shown in Figure 5. ２ and the effective diameter d of the tapered female thread ４ The difference (d ４ -d ２ ) Alternatively, instead of parameterizing the "difference in effective diameter between the male and female threads," the "effective diameter of the female thread" may be used. In this case, the "difference in effective diameter between the male and female threads" may be calculated from the "effective diameter of the male thread" and the "effective diameter of the female thread."

[0048] Furthermore, CPU 1 generates an interface to be displayed on the display device 5. Figure 7 shows an example of a parameter interface. In the example shown in Figure 7, CPU 1 generates an interface for inputting values ​​for the effective diameter of the male screw (pd_pin), the number of threads (thread), etc.

[0049] In step S102, a formula is set up to automatically generate the drawing using the parameters from step S101. Here, the CPU 1 sets up a formula to calculate from the parameters of step S101 the information necessary to draw the connection structure of the first column 21, the first joint 22, and the second column 23, which was not parameterized in step S101.

[0050] Figure 8 shows an example of an interface for displaying the set mathematical formulas. The CPU 1 reads and sets mathematical formulas for calculating the amount of movement z in step S203 (described later), and mathematical formulas for calculating the amount of movement r in step S205 (described later) from the auxiliary storage device 4, etc.

[0051] In step S103, an arbitrary value is specified for the parameterized value (screw dimension) from step S101. Here, the CPU 1 displays an interface on the display device 5 for inputting the information parameterized in step S101 ("effective diameter of the male thread", "number of threads", "thread length", "difference in effective diameter between the male and female threads"), and accepts parameter input. The operator inputs the parameter values ​​by operating the control device 6, etc. Figure 9 is an example of a parameter interface with input values.

[0052] In step S104, a 2D tapered thread connection structure (two-dimensional model, 2D CAD data) is drawn according to the values ​​set in step S103. The process in step S104 will be explained using Figure 10. Figure 10 is a flowchart illustrating the method for generating the two-dimensional model.

[0053] In step S201, a vertically symmetrical male and female thread is created according to the value set in step S103. Figure 11 is an example of the right half of a horizontally symmetrical two-dimensional axially symmetric model created in step S201.

[0054] CPU 1 draws the geometry (shape) of the first column 21, the first joint body (joint body) 22, and the second column 23.

[0055] The first columnar body 21 has a first columnar body geometry 210 and a first tapered female thread geometry 211. The first tapered female thread geometry 211 is the geometry that includes the shape of the first tapered female thread. The first columnar body geometry 210 is the geometry of the portion of the first columnar body 21 other than the first tapered female thread geometry 211.

[0056] The first connector body 22 has a connector body geometry 220, a first tapered thread geometry 221, and a second tapered thread geometry 222. The first tapered thread geometry 221 is a geometry that includes the shape of the first tapered thread. The first tapered thread geometry 221 also includes a tapered line segment 221a parallel to the taper angle of the first tapered thread. The second tapered thread geometry 222 is a geometry that includes the shape of the second tapered thread. The second tapered thread geometry 222 also includes a tapered line segment 222b parallel to the taper angle of the second tapered thread. The connector body geometry 220 is the geometry of the portion of the first connector body 22 other than the first tapered thread geometry 221 and the second tapered thread geometry 222. The geometry 220 of the joint body includes a tapered line segment 220a that overlaps with the tapered line segment 221a, and a tapered line segment 220b that overlaps with the tapered line segment 222b.

[0057] The second columnar body 23 has a second columnar body geometry 230 and a second tapered female thread geometry 231. The second tapered female thread geometry 231 is the geometry that includes the shape of the second tapered female thread. The second columnar body geometry 230 is the geometry of the second columnar body 23 other than the second tapered female thread geometry 231.

[0058] Here, CPU 1 draws the geometry of the connector body 220, the geometry of the first tapered male thread portion 221, and the geometry of the second tapered male thread portion 222 based on the "effective diameter of the male thread", "number of threads", and "thread length" input in step S103.

[0059] Next, CPU 1 draws the geometry of the first tapered female thread portion 211 such that the shape of the first tapered male thread and the shape of the first tapered female thread of the geometry of the first tapered male thread portion 221 overlap, and then draws the geometry of the first column body portion 210.

[0060] Furthermore, CPU 1 draws the geometry of the second tapered female thread portion 231 such that the shape of the second tapered male thread and the shape of the second tapered female thread of the geometry of the second tapered male thread portion 222 overlap, and then draws the geometry of the second column body portion 230.

[0061] Here, the first tapered male thread of the first tapered male thread geometry 221 and the second tapered male thread of the second tapered male thread geometry 222 are drawn at the effective diameter of the male thread. On the other hand, the first tapered female thread of the first tapered female thread geometry 211 and the second tapered female thread of the second tapered female thread geometry 231 are not drawn at the effective diameter of the female thread, but are drawn at the effective diameter of the male thread. Furthermore, the first tapered male thread of the first tapered male thread geometry 221 and the first tapered female thread of the first tapered female thread geometry 211 are in contact on both sides of the thread. Also, the second tapered male thread of the second tapered male thread geometry 222 and the second tapered female thread of the second tapered female thread geometry 231 are in contact on both sides of the thread.

[0062] In step S202, the entire upper threaded portion and the lower female threaded portion are moved horizontally by the difference in effective diameter. Figure 12 is an example of a two-dimensional model created in step S202.

[0063] Here, CPU 1 moves the first tapered female thread geometry 211, the first tapered male thread geometry 221, and the second tapered female thread geometry 231 in the two-dimensional model radially outward horizontally (see white arrow) by the amount of the difference in effective diameter between the male and female threads. As a result, the first tapered female thread of the first tapered female thread geometry 211 and the second tapered female thread of the second tapered female thread geometry 231 are drawn at the position of the effective diameter of the female thread. In addition, the first tapered male thread of the first tapered female thread geometry 211 and the first tapered female thread of the first tapered female thread geometry 211 are in contact with each other on both sides of the thread.

[0064] In step S203, the main body of the male screw is moved vertically so that the line segment overlaps with the upper male screw. Figure 13 is an example of a two-dimensional model created in step S203.

[0065] Here, CPU 1 moves the connector body geometry 220 vertically (see white arrow) in the two-dimensional model so that the tapered line segment 220a (second tapered line segment) of the connector body geometry 220 overlaps with the tapered line segment 221a (first tapered line segment) of the first tapered male thread geometry 221. Specifically, CPU 1 calculates the vertical movement amount z based on the formula set in step S103 and the parameters entered in step S201. Then, CPU 1 moves vertically (see white arrow) in the two-dimensional model so that the tapered line segment 220a (second tapered line segment) of the connector body geometry 220 overlaps with the tapered line segment 221a (first tapered line segment) of the first tapered male thread geometry 221. The vertical displacement z is calculated as (d3 - d2) / tanθ, where θ is the taper angle, d2 is the effective diameter of the male thread, and d3 is the effective diameter of the female thread.

[0066] In step S204, the lower male thread portion is moved horizontally by the amount of the effective diameter difference. Figure 14 is an example of a two-dimensional model created in step S204.

[0067] Here, CPU 1 moves the second tapered male thread geometry 222 in the two-dimensional model by the amount of the effective diameter difference between the male and female threads (the amount of movement in step S202) in the radially inward horizontal direction (see the white arrow, in the opposite direction to the direction of movement in step S202). As a result, the tapered line segment 222b (third tapered line segment) of the second tapered male thread geometry 222 overlaps with the tapered line segment 220b (fourth tapered line segment) of the joint body geometry 220.

[0068] In step S205, the lower threaded portion of the female thread is moved along the taper so that the lower line segment of the female thread and the upper line segment of the male thread coincide. Figure 15 is an example of a two-dimensional model created in step S205. Figure 16 is an example of a magnified view of the second tapered male thread geometry 222 and the second tapered female thread geometry 231 of the two-dimensional model created in step S205.

[0069] Here, CPU 1 moves the second tapered female thread geometry 231 in the direction along the taper (see white arrow) so that the lower line segment 231c of the thread of the second tapered female thread geometry 231 overlaps with the upper line segment 222c of the thread of the second tapered male thread geometry 222 in the two-dimensional model. Specifically, CPU 1 calculates the amount of movement r in the direction along the taper based on the formula set in step S103 and the parameters entered in step S201. The amount of movement r in the direction along the taper is calculated as (d3-d2)sinθ / 2cos(30°-θ) in the horizontal direction and (d3-d2)cosθ・2cos(30°-θ) in the vertical direction, where θ is the taper angle, d2 is the effective diameter of the male thread, and d3 is the effective diameter of the female thread. Then, in the two-dimensional model, CPU 1 moves in a direction along the taper (see white arrow) so that the lower line segment 231c of the thread of the second tapered female thread geometry 231 overlaps with the upper line segment 222c of the thread of the second tapered male thread geometry 222. As a result, the second tapered male thread geometry 222 and the second tapered female thread geometry 231 are in contact with each other on one side of the thread.

[0070] Based on the above, the CPU 1 can generate the geometry of the connecting structure at the electrode 20. That is, the evaluation device 10 can generate a two-dimensional model having the geometry of the connecting structure at the electrode 20. This reduces the operator's working time.

[0071] In this way, by having the operator input parameterized information ("effective diameter of the male thread," "number of threads," "thread removal," and "difference in effective diameter between the male and female threads"), the evaluation device 10 generates a two-dimensional model based on the input parameters. The generated two-dimensional model can be used, for example, for analysis simulation of the electrode 20, or for evaluation of tapered thread loosening, as described later.

[0072] The parameterized information explained using "effective diameter of the male thread," "number of threads," "thread count," and "difference in effective diameter between the male and female threads" as examples is not limited to these. For example, the taper angle could also be parameterized.

[0073] Figure 17 is an example of a two-dimensional model (2D CAD data) of a connecting structure using tapered threads. Through the processing of steps S101 to S104, a two-dimensional model (2D CAD data) of a connecting structure using tapered threads (connecting structure in the first column 21, first joint body 22, and second column 23) is drawn as shown in Figure 17.

[0074] Let's return to Figure 6 and explain further. Next, before performing the stress analysis (S109) described later, we set the boundary conditions for the analysis. Specifically, setting the boundary conditions involves the processes from step S105 to step S107.

[0075] In step S105, a small distance offset (insertion amount) is set on the edge corresponding to the end face of the upper female thread (first column 21).

[0076] Figures 18A and 18B are schematic diagrams illustrating a two-dimensional model that reproduces the axial force generated in the first joint body 22. Figure 18A is an example of a schematic diagram of a two-dimensional model of the constructed connecting structure. Figure 18B is an example of a schematic diagram of a two-dimensional model of the connecting structure that reproduces the axial force generated in the first joint body 22.

[0077] Here, in the connection structure using tapered threads (the connection structure in the first column 21, the first joint body 22, and the second column 23), the first column 21 and the second column 23 are fastened together by the axial force (tensile stress) generated in the first joint body 22. In the two-dimensional model (2D CAD data) of the connection structure using tapered threads used in the simulation (stress analysis in step S108) described later, the axial force (tensile stress 35) generated in the first joint body 22 is reproduced by creating a biting portion in the end face portion 30.

[0078] The two-dimensional model of the connecting structure shown in Figure 18A has an end face portion 30 where the end face (bottom surface) 21T of the first column 21 and the end face (top surface) 23T of the second column 23 abut. In step S105, as shown in Figure 18B, the end face 21T of the first column 21 is offset by a predetermined small distance to the side of the second column 23 (the bottom side in the example of Figure 18B). In the example of Figure 18B, the offset amount (insertion amount) 31 is indicated by an arrow. Here, the small distance is, for example, 0.01 mm. The small distance is, for example, 10 times the length of the first joint body 22. －６ ~10 －５ It can be within the range of double.

[0079] Here, the lower end face 21T of the first column 21 is offset downwards, while the upper end face 23T of the second column 23 remains in its original position. Therefore, in the two-dimensional model, the first column 21 and the second column 23 interfere with each other at a small distance (offset amount 31). In Figure 18B, the overlapping hatching of the first column 21 (downward-sloping diagonal lines) and the hatching of the second column 23 (upward-sloping diagonal lines) shows the portion of interference between the end faces 21T and 23T.

[0080] As shown in Figure 17, the evaluation device 10 creates a two-dimensional model (2D CAD data) of a connecting structure (connecting structure in the first column 21, first joint body 22, and second column 23) using tapered threads, which was drawn by the processing of steps S101 to S104, in which the end face 21T of the first column 21 is offset by a small distance (offset amount 31) to the side of the second column 23 (the lower side in the example of Figure 18B).

[0081] In step S106, a complete constraint condition is set on the upper surface 21S of the upper female thread (first column 21). Here, as preparation for the simulation described later (stress analysis in step S108), a complete constraint condition is set on the upper surface 21S of the first column 21 in the two-dimensional model (2D CAD data) of the connecting structure. Thus, one end face 21T of the first column 21 (lower side) is the surface that abuts against the second column 23, and the upper surface 21S of the other side (upper side) is the surface on which a complete constraint condition is set in the simulation.

[0082] In step S107, a coefficient of friction is set for the edge (thread / end face) that is in contact with the surface.

[0083] Figures 19A to 19C are schematic diagrams illustrating frictional forces in a connecting structure using tapered threads. In Figures 19A to 19C, the normal force is indicated by a dashed arrow, and the magnitude of the frictional force is indicated by a solid arrow.

[0084] As shown in Figure 19A, at the contact point between the first column 21 and the first joint 22, frictional force is generated when the first tapered female thread portion of the first column 21 and the first tapered male thread portion of the first joint 22 are in contact on both sides of the threads.

[0085] As shown in Figure 19B, at the contact point between the second column 23 and the first joint 22, frictional force is generated because the second tapered female thread portion of the second column 23 and the second tapered male thread portion of the first joint 22 are in contact with each other on only one side of the thread.

[0086] As shown in Figure 19C, the contact area between the first column 21 and the second column 23 is in contact at the end faces, generating frictional force.

[0087] In step S107, the evaluation device 10 sets the coefficient of friction. Here, the first column 21, the first joint 22, and the second column 23 are all made of graphite. Therefore, the coefficients of friction of each part shown in Figures 19A to 19C are assumed to be equal. Here, the CPU 1 displays an interface for inputting the coefficient of friction in step S107 on the display device 5 and accepts the input of the coefficient of friction. The operator inputs the value of the coefficient of friction by operating the operating device 6, etc.

[0088] In step S108, a stress analysis is performed. Here, the evaluation device 10 performs a stress analysis based on the two-dimensional model of the connecting structure (2D CAD data) drawn in step S104, the offset amount 31 (minute distance) of the end face portion 30 set in step S105, the complete constraint conditions set in step S106, and the friction coefficient set in step S107.

[0089] Here, the evaluation device 10 calculates the frictional force for each element coordinate (see solid arrows) by stress analysis, as shown in Figures 19A to 19C.

[0090] In step S109, the frictional force of the contact edge is output and the sum of the frictional forces (absolute values) of each edge is calculated.

[0091] Here, the evaluation device 10 rotates the two-dimensional model around its central axis (the dashed line in Figure 17), and calculates the frictional force of each contact surface by integrating the frictional force for each element coordinate obtained in the stress analysis performed in step S108. Then, the evaluation device 10 calculates the sum of the absolute values ​​of the frictional forces of each contact surface calculated in step S108.

[0092] In step S110, the loosening of the tapered screw is evaluated based on the sum of the calculated frictional forces.

[0093] Figures 20A and 20B are examples of graphs showing test results and simulation results for evaluating loosening of the connecting structure.

[0094] Here, connecting structures (connecting structures in the first column 21, first joint 22, and second column 23) using tapered threads with modified parameters were created and designated as (1) to (5). In connecting structures (1) to (5), the first column 21 and the first joint 22 were fastened with the same torque. Furthermore, in connecting structures (1) to (5), the first joint 22 and the second column 23 were fastened with the same torque to create the connecting structures. Next, the connecting structures (1) to (5) were rotated in the loosening direction, and the amount of work required to loosen them was detected. Figure 20A is an example of a graph showing the amount of work required to loosen the connecting structures (1) to (5). Here, a larger value for the amount of work required to loosen indicates that the connecting structure is less likely to loosen.

[0095] Furthermore, steps S101 to S109 were performed using the parameters of the connecting structures (1) to (5) to calculate the sum of the frictional forces. Figure 20B is an example of a graph showing the sum of the frictional forces in the connecting structures (1) to (5). Here, when the connecting structures are assembled with the same torque, it is considered that the smaller the sum of the frictional forces, the tighter the connection will be.

[0096] As shown by comparing Figure 20A and Figure 20B, the smaller the sum of the frictional forces, the greater the amount of work required to loosen the connection, indicating that the connection structure is less likely to loosen. Conversely, the larger the sum of the frictional forces, the smaller the amount of work required to loosen the connection, indicating that the connection structure is more likely to loosen.

[0097] In this way, the evaluation device 10 evaluates how resistant the connecting structure is to loosening based on the sum of the frictional forces calculated in step S109. Specifically, the evaluation device 10 evaluates that the smaller the sum of the frictional forces, the less likely the connecting structure is to loosen, and the larger the sum of the frictional forces, the more likely the connecting structure is to loosen.

[0098] As described above, the evaluation device 10 allows for the creation of a two-dimensional model (2D CAD data) of the connecting structure while appropriately changing the screw dimensions, and the loosening (ease of loosening, difficulty of loosening) of the connecting structure can be evaluated. Furthermore, by using the two-dimensional model (2D CAD data), the evaluation device 10 allows for simulation with reduced computational costs for stress analysis (S108). In addition, since the loosening of the connecting structure can be evaluated by simulation using the evaluation device 10, costs can be reduced compared to actually creating the connecting structure and evaluating its loosening experimentally.

[0099] Aspects of the present disclosure are, for example, as follows: [1] A tapered screw loosening evaluation method for evaluating loosening in a connecting structure in which a first column having a first tapered female thread and a second column having a second tapered female thread are connected by a joint having a first tapered male thread and a second tapered male thread, the method comprising: causing a computer to perform the steps of: specifying screw dimensions; drawing a two-dimensional model of the connecting structure based on the specified screw dimensions; providing boundary conditions; performing an analysis based on the two-dimensional model and the boundary conditions; and evaluating frictional force from the results of the analysis. [2] The tapered screw loosening evaluation method according to [1], wherein the boundary conditions include an offset amount that offsets the end faces in contact with the first column and the second column towards the second column. [3] The tapered screw loosening evaluation method according to [2], wherein the boundary conditions include setting a complete constraint condition on the upper surface of the first column. [4] The tapered screw loosening evaluation method according to [2] or [3], wherein the boundary conditions include setting a coefficient of friction. [5] The tapered screw loosening evaluation method according to any one of [2] to [4], wherein the step of evaluating the friction force is evaluated based on the sum of the friction force at the contact portion between the first tapered female thread portion of the first column and the first tapered male thread portion of the joint body, the friction force at the contact portion between the second tapered female thread portion of the second column and the second tapered male thread portion of the joint body, and the friction force at the end faces where the first column and the second column contact. [6] The tapered screw loosening evaluation method according to [5], wherein the step of evaluating the friction force is evaluated as the less the sum of the friction forces is, the less likely the connecting structure is to loosen, and the more the sum of the friction forces is, the more likely the connecting structure is to loosen. [7] The tapered screw loosening evaluation method according to any one of [1] to [6], wherein the screw dimensions include the effective diameter of the male thread, the number of threads, the thread length, and the difference in effective diameter between the male and female threads. [8] The tapered screw loosening evaluation method according to [7], wherein the screw dimensions further include the taper angle.[9] An evaluation device for evaluating loosening in a connecting structure in which a first column having a first tapered female thread and a second column having a second tapered female thread are connected by a joint having a first tapered male thread and a second tapered male thread, comprising: an operating device and a control unit, wherein the control unit is configured to perform the steps of: specifying screw dimensions from the operating device; drawing a two-dimensional model of the connecting structure based on the specified screw dimensions; providing boundary conditions; performing an analysis based on the two-dimensional model and the boundary conditions; and evaluating frictional force from the results of the analysis.

[10] A program that causes a computer to perform a process to evaluate loosening in a connecting structure in which a first column having a first tapered female thread and a second column having a second tapered female thread are connected by a joint having a first tapered male thread and a second tapered male thread, the program causing the computer to perform the steps of: specifying the screw dimensions; drawing a two-dimensional model of the connecting structure based on the specified screw dimensions; providing boundary conditions; performing an analysis based on the two-dimensional model and the boundary conditions; and evaluating the frictional force from the results of the analysis.

[0100] It should be noted that the present invention is not limited to the configurations shown in the above embodiments, including combinations with other elements. These aspects can be modified without departing from the spirit of the present invention and can be appropriately determined according to their application.

[0101] Furthermore, this application claims priority based on Japanese Patent Application No. 2024-227966, filed on December 24, 2024, and the entire contents of these Japanese Patent Applications are incorporated herein by reference.

[0102] 1 CPU (Control Unit) 6 Operating Device 10 Evaluation Device 20 Electrode 21 First Column 21S Top Surface 21T End Face 22 First Connector (Connector) 23 Second Column 23T End Face 24 Second Connector 25 Third Column 30 End Face 31 Offset Amount 210 First Column Body Geometry 211 First Tapered Female Thread Geometry 220 Connector Body Geometry 221 First Tapered Male Thread Geometry 222 Second Tapered Male Thread Geometry 230 Second Column Body Geometry 231 Second Tapered Female Thread Geometry

Claims

1. A tapered screw loosening evaluation method for evaluating loosening in a connecting structure in which a first column having a first tapered female thread portion and a second column having a second tapered female thread portion are connected by a joint having a first tapered male thread portion and a second tapered male thread portion, the method comprising: causing a computer to perform the steps of: specifying the screw dimensions; drawing a two-dimensional model of the connecting structure based on the specified screw dimensions; providing boundary conditions; performing an analysis based on the two-dimensional model and the boundary conditions; and evaluating the frictional force from the results of the analysis.

2. The tapered screw loosening evaluation method according to claim 1, wherein the boundary condition includes an offset amount that offsets the end face of the first column to the side of the second column among the end faces of the two-dimensional model in which the first column and the second column abut.

3. The tapered screw loosening evaluation method according to claim 2, wherein the boundary condition includes setting a complete constraint condition on the upper surface of the first column.

4. The tapered screw loosening evaluation method according to claim 2 or 3, wherein the boundary condition includes setting a coefficient of friction.

5. The tapered screw loosening evaluation method according to any one of claims 2 to 4, wherein the step of evaluating the frictional force is to evaluate based on the sum of the frictional force at the contact portion between the first tapered female thread portion of the first column and the first tapered male thread portion of the joint body, the frictional force at the contact portion between the second tapered female thread portion of the second column and the second tapered male thread portion of the joint body, and the frictional force at the end faces where the first column and the second column are in contact.

6. The tapered screw loosening evaluation method according to claim 5, wherein the step of evaluating the frictional force is to evaluate that the smaller the sum of the frictional forces, the less likely the connecting structure is to loosen, and the larger the sum of the frictional forces, the more likely the connecting structure is to loosen.

7. The tapered screw loosening evaluation method according to any one of claims 1 to 6, wherein the screw dimensions include the effective diameter of the male screw, the number of threads, the thread length, and the difference in effective diameter between the male and female screws.

8. The tapered screw loosening evaluation method according to claim 7, wherein the screw dimensions further include a taper angle.

9. An evaluation device for evaluating loosening in a connecting structure in which a first column having a first tapered female thread and a second column having a second tapered female thread are connected by a joint having a first tapered male thread and a second tapered male thread, comprising: an operating device and a control unit, wherein the control unit is configured to perform the steps of: specifying screw dimensions from the operating device; drawing a two-dimensional model of the connecting structure based on the specified screw dimensions; providing boundary conditions; performing an analysis based on the two-dimensional model and the boundary conditions; and evaluating frictional force from the results of the analysis.

10. A program that causes a computer to perform a process to evaluate loosening in a connecting structure in which a first column having a first tapered female thread and a second column having a second tapered female thread are connected by a joint having a first tapered male thread and a second tapered male thread, the program causing the computer to perform the steps of: specifying the screw dimensions; drawing a two-dimensional model of the connecting structure based on the specified screw dimensions; providing boundary conditions; performing an analysis based on the two-dimensional model and the boundary conditions; and evaluating the frictional force from the results of the analysis.

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