JP2008250410A - Method for analyzing strength of fastened structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for facilitating strength analysis of a fastened structure in a short time through simple structure. <P>SOLUTION: In the method for analyzing the strength of a fastened structure obtained by fastening a male thread member 1 to a female thread member 2, springs acting in the radial, circumferential and vertical directions of a node at a screw thread contact portion between the male thread member 1 and the female thread member 2 are assumed, and spring constants kr, kθ and kn equivalent to a stress received by the contact portion are determined and defined for the respective assumed springs, whereby calculation necessary for strength analysis is performed while substituting the stress received by the contact portion by the springs. Since the analysis of the springs can be linearly treated, repeated calculations due to the conventional nonlinear analysis is not required, and the calculation necessary for strength analysis can be facilitated in a short time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fastening structure strength analysis method, and more particularly to a method of analyzing the strength of a fastening structure formed by fastening a male screw member and a female screw member.

  For example, in a fastening structure in which a male screw member such as a bolt is fastened to a female screw member such as a nut, in order to analyze the strength from the stress, strain, deformation, etc., based on the conventional finite element method (FEM) Programmed FEM analysis software is generally used (see, for example, Patent Document 1). In the analysis by the finite element method, a fastening structure is modeled and a mesh divided into multiple elements by nodes is hypothesized, an equation is created for each mesh, and the equation as a whole is assembled and calculated. ing.

  When analyzing the strength of the fastening structure using such a finite element method, as shown in FIG. 16, the vicinity of the thread where the stress-concentrated male screw member 1 and female screw member 2 contact each other is particularly detailed. It is divided into meshes. Conventionally, generally, when analyzing the strength of the fastening structure using FEM analysis software, the contact of the thread members of the screw member 1 and the female screw member 2 is defined for each node of the mesh. It was necessary to calculate the stress generated in the part for each node. Further, in the strength analysis of the fastening structure by the finite element method, as shown in FIG. 17, the stress generated during fastening does not increase in proportion to the passage of time, and the change in stress is calculated as linear. Therefore, it was treated as non-linear, divided into sections that could be treated as linear, approximated as linear, and the calculation was repeated for each section that was divided and analyzed.

JP 2006-53822 A

  As described above, in the conventional technology, when analyzing the strength of the fastening structure using the FEM analysis software, the contact between the thread members of the screw member and the female screw member is repeatedly defined for each node of the mesh. Furthermore, since it is necessary to calculate the stress generated at the contact portion for each node, there is a problem that the processing for analysis is complicated and time-consuming, and the analysis takes time.

  Further, in the strength analysis of the fastening structure by the conventional finite element method, as shown in FIG. 17, since it is necessary to repeatedly perform the calculation in order to treat it as non-linear, there is a problem that the analysis takes time. there were.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a method capable of easily analyzing the strength of a fastening structure in a short time with a simple configuration.

  In order to solve the above-described problem, the present invention is a method for analyzing the strength of a fastening structure formed by fastening a male screw member and a female screw member, and a stress that is applied to a contact portion between the male screw member and the female screw member. It is characterized in that the calculation necessary for the strength analysis is performed instead of a spring equivalent to.

  According to the present invention, by replacing with a spring equivalent to the stress received by the contact portion of the male screw member and the female screw member, it is not necessary to repeat the calculation to treat it as non-linear as in the prior art, and as a linear Since it can be handled, the time required for the calculation required for the strength analysis can be shortened, and the analysis can be easily performed.

(Aspect of the Invention)
In the following, the invention that is claimed to be claimable in the present application (hereinafter referred to as “claimable invention”. The claimable invention is at least the “present invention” to the invention described in the claims. Some aspects of the present invention, including subordinate concept inventions of the present invention, superordinate concepts of the present invention, or inventions of different concepts) will be illustrated and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is for the purpose of facilitating the understanding of the claimable invention, and is not intended to limit the combinations of the constituent elements constituting the claimable invention to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. In addition, an aspect in which constituent elements are deleted from the aspect of each item can be an aspect of the claimable invention. In each of the following items, item (1) corresponds to claim 1 and item (2) corresponds to claim 2.

(1) A method for analyzing the strength of a fastening structure formed by fastening a male screw member and a female screw member,
A strength analysis method for a fastening structure, wherein a calculation necessary for strength analysis is performed by replacing a spring equivalent to a stress received by a contact portion of a male screw member and a female screw member.

  In the invention described in item (1), the spring is replaced with a spring equivalent to the stress received by the contact portion between the male screw member and the female screw member. Since spring analysis can be handled as linear, there is no need to repeat calculations to handle them as non-linear as in the prior art, and calculations required for strength analysis can be easily performed in a short time. it can.

  (2) Define springs that act in the radial, circumferential, and vertical directions of the nodes at the contact portion of the male screw member and female screw member, and perform calculations necessary for strength analysis based on the spring constant of each spring The strength analysis method for a fastening structure according to item (1), wherein:

  In the invention described in item (2), in the invention described in item (1), each of the springs acting in the radial direction, circumferential direction, and vertical direction of the node at the contact portion between the male screw member and the female screw member is virtually assumed. A spring constant equivalent to the stress experienced by the virtual contacted part of the spring is obtained. In order to define a spring with a spring constant equivalent to the stress received by the contact part of the male screw member and the female screw member, the stress received by the contact part of the male screw member and the female screw member can be easily grasped, It is possible to analyze the strength of a fastening structure formed by fastening the.

An embodiment of the present invention will be described in detail with reference to FIGS. In the drawings, the same reference numerals denote the same or corresponding parts.
The present invention is generally a method for analyzing the strength of a fastening structure formed by fastening a male screw member 1 and a female screw member 2, and is a method of analyzing the nodes at the contact points of the threads of the male screw member 1 and the female screw member 2. The stress acting on the contact part is defined by obtaining spring constants kr, kθ, kn equivalent to the stresses of the contact parts of the hypothetical springs acting in the radial, circumferential and vertical directions. Is replaced with the spring to perform calculations necessary for strength analysis.

  FIG. 1 is a block diagram showing an overall embodiment of a procedure according to the method of the present invention. In analyzing the strength of a fastening structure formed by fastening the male screw member 1 and the female screw member 2, as a preparation, as shown in FIGS. 3 and 8, a mesh (calculation model) of the bolt 1 which is a screw member is used. As shown in FIG. 2, a mesh (calculation model) of the jig 2 on which the female screw for fastening the bolt 1 is formed as shown in FIG. 2 is created, and the threads of the bolt 1 and the jig 2 are brought into contact with each other. Define (S1 in FIG. 1). In addition, although the thread of the bolt 1 and the jig 2 is actually formed in a spiral shape, the mesh in the embodiment shown in FIG. 8 and the like is simplified to a mesh having a plurality of annular shapes. It has become. Such simplification is a common practice in analysis by the finite element method.

  Next, a calculation for applying an axial force F to the mesh of the bolt 1 as shown in FIG. 4 (S2 in FIG. 1) is performed, and a radial frictional force Fr along the contact surface of the thread as shown in FIG. And a slip amount (displacement amount) δr are obtained (S3 in FIG. 1), and calculation is performed to give torque T to the mesh of the bolt 1 as shown in FIG. 6 (S2 in FIG. 1), as shown in FIG. Thus, the circumferential frictional force Fθ and the slip amount (displacement amount) δθ along the contact surface of the screw thread between the bolt 1 and the jig 2 are obtained (S3 in FIG. 1). These radial friction force Fr and slip amount δr, and circumferential friction force Fθ and slip amount δθ can be obtained by calculation based on the principle of virtual work using numerical analysis of FEM analysis software. it can.

  Subsequently, a radial constant kr is obtained from the ratio of the radial friction force Fr and the slip amount δr (kr = Fr / δr), and the circumferential constant kθ is calculated from the ratio of the circumferential friction force Fθ and the slip amount δθ. (Kθ = Fθ / δθ) and a constant kn in a direction perpendicular to the thread is obtained as described later (S4 in FIG. 1). In addition, although the process of S1-S4 in FIG. 1 is the same as the process of the analysis using the FEM analysis software by the finite element method in the prior art, in the prior art, the definition of contact and the stress generated in the contact site While the calculation had to be repeated at every node, it differs in that it was only performed once in preparation for carrying out the present invention.

Next, as shown in FIGS. 9 to 12, the three nodes in the radial direction of the contact surface, the circumferential direction, and the vertical direction at the nodes between the contact portions of the male screw 1 of the bolt 1 and the female screw of the jig 2. A spring that is supposed to act on each of these is defined (S5 in FIG. 1). The previously calculated kr as the constant is applied to the radial spring, and the previously calculated kθ is applied to the circumferential spring as the constant. Further, the constant kn of the spring imaginary in the direction perpendicular to the contact surface is considered to be a sufficiently large value, for example, 10 ¹⁰ , because the contact surfaces of the threads of the male screw and the female screw are not separated from each other. [N / m] and the like are set (S6 in FIG. 1). The three-direction springs defined for each of these nodes are, for example, as shown in FIG. 13, a declaration of the spring definition, the name of the spring to be defined, the coordinate system of the spring to be defined, the direction in which the spring force acts, And the spring constant are automatically or manually input into a spring analysis program in general-purpose FEM analysis software (for example, trade name ABAQUS).

  Next, the bolt 1 and jig 2 defined in the previous step (S1 in FIG. 1) are used so that the FEM analysis software program does not actually perform the analysis by the finite element method in the same manner as in the past. 1 is deleted (S7 in FIG. 1).

  After that, the strength is analyzed by performing calculation under various conditions (for example, fastening, twisting, bending, etc. in addition to the tension shown in FIG. 14) for which stress is actually evaluated (S8 in FIG. 1). This strength analysis can be evaluated based on stress, strain, deformation, and the like obtained by simulating the various conditions described above.

  In the present invention, since the radial and circumferential constants obtained at S4 in FIG. 1 are used as spring constants that are virtually defined, the stress experienced by the contact portion of the thread of the male screw member 1 and female screw member 2 It is possible to perform a linear calculation by replacing with a spring equivalent to. Therefore, since it is not necessary to perform iterative calculation as in the conventional non-linear calculation, the number of calculations can be reduced. Therefore, as shown in comparison with FIG. 15, the present invention is capable of performing linear calculation. Therefore, compared with the conventional nonlinear calculation, the time required for the analysis can be shortened to, for example, about two thirds.

It is the block diagram shown in order to demonstrate one whole Embodiment of the method of this invention. It is a perspective view of the mesh (calculation model) of the jig | tool with which the volt | bolt and internal thread which are created as preparation for performing an intensity | strength analysis were formed. It is a perspective view of the mesh (calculation model) of the volt | bolt shown in FIG. It is the perspective view typically shown in order to demonstrate the calculation which gives the axial force F to the mesh of the bolt fastened by the jig | tool. FIG. 5 is a perspective view schematically showing a radial frictional force Fr and a slip amount (displacement amount) δr along a contact surface of a thread obtained by the calculation shown in FIG. 4. It is the perspective view typically shown in order to demonstrate the calculation which gives the torque T to the mesh of the bolt fastened by the jig | tool. FIG. 7 is a perspective view schematically showing a circumferential frictional force Fθ and a slip amount (displacement amount) δθ along a contact surface of a thread obtained by the calculation shown in FIG. 6. It is a partial expansion perspective view of the mesh created by simplifying the bolt. It is a fragmentary sectional perspective view for demonstrating the spring defined virtually by this invention. It is a perspective view for demonstrating the spring defined for each node in the contact surface of a male screw and a female screw by this invention. It is a partial expanded sectional view of FIG. FIG. 12 is a further partial enlarged cross-sectional view of FIG. 11. It is explanatory drawing which shows one Embodiment of the program which inputs the definition of the spring by this invention. It is a perspective view for demonstrating the state which applies tensile force to a volt | bolt and performs strength analysis. It is explanatory drawing shown in order to compare the time concerning the nonlinear calculation performed with the prior art, and the linear calculation by this invention. It is the fragmentary sectional perspective view shown in order to demonstrate the prior art. It is explanatory drawing which showed the state which partitions off nonlinearity by the prior art, and performs the iterative calculation.

Explanation of symbols

1: Bolt (male thread member) 2: Jig (female thread member), kr: Spring constant in the radial direction, kθ: Spring constant in the circumferential direction, kn: Spring constant in the direction perpendicular to the thread

Claims (2)

A method of analyzing the strength of a fastening structure formed by fastening a male screw member and a female screw member,
A strength analysis method for a fastening structure, wherein a calculation necessary for strength analysis is performed by replacing a spring equivalent to a stress received by a contact portion of a male screw member and a female screw member. The springs acting in the radial direction, the circumferential direction, and the vertical direction at the contact portion between the male screw member and the female screw member are defined, and calculations necessary for strength analysis are performed based on the spring constant of each spring. The strength analysis method of the fastening structure according to claim 1.