Method for calculating shearing load of bolt

Abstract

To provide an easy method for calculating a shearing load of a bolt.SOLUTION: There is provided a method for calculating a shearing load of a bolt that fastens a plurality of members, the method including: identifying a bending direction of a shank of the bolt on the basis of a contour diagram indicating tensile compressive stress on a cross section intersecting an axial direction of the shank; calculating the shearing stress in a first direction at a plurality of points on an outer periphery of the cross section on the basis of a contour diagram indicating shearing stress in the first direction on the cross section; calculating the shearing stress in a second direction intersecting the first direction at the plurality of points on the basis of a contour diagram indicating the shearing stress in the second direction on the cross section; and calculating the shearing stress of the bolt on the basis of a total value of a size of components in the bending direction of the respective shearing stress in the first direction at the plurality of points, and a size of components in the bending direction of the respective shearing stress in the second direction of at the plurality of points.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for calculating the shear load of a bolt. [Background technology]

[0002] Bolts are sometimes used to fasten a plurality of members together (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-90862 A Summary of the Invention [Problem to be solved by the invention]

[0004] When designing such bolts, it is preferable to take into account the shear load acting on the bolt, but the calculation of such shear load is complicated.

[0005] Therefore, an object of the present invention is to provide a method for calculating the shear load of a bolt using a simple technique. [Means for solving the problem]

[0006] The above object can be achieved by a method for calculating the shear load of a bolt that fastens multiple components, the method including: identifying the bending direction of the shank of the bolt based on a contour diagram showing the tensile compressive stress in a cross section that intersects the axial direction of the shank of the bolt; calculating the shear stress in the first direction at each of multiple points on the outer periphery of the cross section based on a contour diagram showing the shear stress in the first direction at the cross section; calculating the shear stress in the second direction at each of the multiple points based on a contour diagram showing the shear stress in a second direction intersecting the first direction at the cross section; and calculating the shear load of the bolt based on the sum of the magnitude of the component in the bending direction of the shear stress in the first direction at the multiple points and the magnitude of the component in the bending direction of the shear stress in the second direction at the multiple points. Effect of the Invention

[0007] According to the present invention, it is possible to provide a method for calculating the shear load of a bolt using a simple technique. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory diagram of a bolt. [Diagram 2] FIG. 2 is a flowchart illustrating a method for calculating the shear load of a bolt. [Diagram 3] FIG. 3A is an example of a contour diagram showing tensile and compressive stress in a cross section, FIG. 3B is an example of a contour diagram showing X-direction shear stress in a cross section, and FIG. 3C is an example of a contour diagram showing Y-direction shear stress in a cross section. [Figure 4] FIG. 4A is a graph showing the X-direction shear stress and the Y-direction shear stress acting at an arbitrary point on the circumference of a cross section, and FIG. 4B is a graph showing the magnitude of the X-direction shear stress σX and the magnitude of the Y-direction shear stress σY. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 1 is an explanatory diagram of a bolt 10. In this embodiment, the bolt 10 fastens an engine body 100 to a flange portion 110 of an exhaust manifold. The bolt 10 is a stud bolt. One end of the bolt 10 is embedded in the engine body 100. The flange portion 110 is sandwiched between the engine body 100 and a nut 20 that is screwed onto a shaft portion 12 of the bolt 10.

[0010] The exhaust manifold is connected to the exhaust pipe. Therefore, the flange portion 110 of the exhaust manifold receives an external force from the exhaust pipe and is displaced. This displacement is caused by the mass of the exhaust manifold, the mass of the exhaust pipe, resonance of the exhaust pipe, and the like. The vibratory force of the resonance is the vibration of the engine body 100. Due to the displacement thus caused, a load is applied to the bolt 10 via the pipe portion and flange portion 110 of the exhaust manifold. FIG. 1 shows a cross section 12a of the shaft portion 12 of the bolt 10 with which the flange portion 110 comes into contact. The cross section 12a is perpendicular to the axial direction of the shaft portion 12. A CAE (Computer Aided Engineering) analysis using three-dimensional CAD data of the bolt 10 used for such an application is used to calculate the shear load acting on the cross section 12a from the flange portion 110.

[0011] FIG. 2 is a flow chart illustrating a method for calculating the shear load of the bolt 10. First, the bending direction D, which is the direction of the bending stress acting on the shaft portion 12 of the bolt 10, is specified (step S1). Specifically, the bending direction D is specified based on the contour diagram showing the tensile and compressive stresses at the cross section 12a described above. FIG. 3A is an example of a contour diagram showing the tensile and compressive stresses at the cross section 12a. A contour diagram is a stress distribution diagram using a finite element method by CAE analysis. In the example of FIG. 3A, a darker hatched area indicates a higher tensile stress, and a lighter hatched area indicates a higher compressive stress. In an actual contour diagram, the display color changes from a cool color to a warm color as the tensile stress increases and as the compressive stress decreases. However, in this specification, the diagram is simply shown with hatching as in FIG. 3A. In FIG. 3A, the direction of the area with the highest compressive stress from the central axis C is the bending direction D. The bending direction D is specified by, for example, an angle α around the Y axis in a clockwise direction.

[0012] Next, the shear stress in the X direction (hereinafter referred to as the X-direction shear stress) σX is calculated (step S2). Specifically, based on a contour diagram showing the X-direction shear stress σX on the cross section 12a, the X-direction shear stress σX at positions on the outer periphery of the cross section 12a at every 1° from θ=0° to 359° is calculated by CAE analysis. FIG. 3B is an example of a contour diagram showing the X-direction shear stress σX on the cross section 12a. In the example of FIG. 3B, the darker hatched areas indicate higher shear stress in the tensile direction, and the lighter hatched areas indicate higher shear stress in the compressive direction. The X-direction shear stress at any point on the outer periphery of the cross section 12a is calculated as σX. θ The component of this X-direction shear stress in the bending direction D is σX θ It can be expressed as sin α. The X direction is an example of the first direction.

[0013] Similarly, the shear stress in the Y direction (hereinafter referred to as Y-direction shear stress) σY is calculated (step S3). Specifically, based on a contour diagram showing the Y-direction shear stress σY at the cross section 12a, the Y-direction shear stress σY at positions on the outer periphery of the cross section 12a at intervals of 1° from θ=0° to 359° is calculated by CAE analysis. FIG. 3C is an example of a contour diagram showing the Y-direction shear stress σY at the cross section 12a. Similarly, in the example of FIG. 3C, the darker hatched areas indicate higher shear stress in the tensile direction, and the lighter hatched areas indicate higher shear stress in the compressive direction. The X-direction shear stress at any point on the outer periphery of the cross section 12a is calculated as σY θ The component of this X-direction shear stress in the bending direction D is σY θ cos α. The Y direction is an example of the second direction.

[0014] Fig. 4A is a graph showing X-direction shear stress σX and Y-direction shear stress σY acting on an arbitrary point on the outer periphery of cross-section 12a. In Fig. 4A, the horizontal axis represents the clockwise angle θ with respect to the Y-axis in Figs. 3A to 3C. The vertical axis represents stress. Here, the positive side of the vertical axis represents compressive shear stress, and the negative side represents tensile shear stress.

[0015] Next, the magnitude |σX| of the X-direction shear stress σX and the magnitude |σY| of the Y-direction shear stress σY are calculated (step S4). Fig. 4B is a graph showing the magnitude |σX| of the X-direction shear stress σX and the magnitude |σY| of the Y-direction shear stress σY.

[0016] Next, the shear load P acting on the shaft portion 12 is calculated based on the magnitude |σX| of the X-direction shear stress σX and the magnitude |σY| of the Y-direction shear stress σY (step S5). Specifically, the sum of the components of the magnitude |σX| of the X-direction shear stress σX in the bending direction D and the sum of the components of the magnitude |σY| of the Y-direction shear stress σY in the bending direction D is calculated as the shear load P. The shear load P is expressed by the following formula (1). TIFF2025027314000002.tif2195

[0017] In this way, the shear load P can be easily calculated. Using the calculated shear load P, the optimal size and shape of the bolt 10 can be designed and the optimal material can be selected. For example, when the exhaust pipe attached to the exhaust manifold is changed and the vibration of the flange portion 110 changes, the shear load P before and after the change can be compared. Furthermore, the flange portion 110 is fixed to the engine body 100 by such a plurality of bolts 10, and the shared load borne by the bolts 10 can be predicted, allowing for appropriate design. In addition, in the process of calculating the shear load P, the tensile load acting on the bolt 10 can also be calculated from the contour diagram of FIG. 3A, and can also be used to calculate the free safety factor for the fastening axial force of the bolt 10.

[0018] In the above embodiment, the shear stress was calculated every 1°, but is not limited to 1°. In addition to points on the outer periphery of the cross section 12a, the shear load P may be calculated using the magnitude of the component of the bending direction D of the shear stress at multiple arbitrary points on the same circumference centered on the central axis C within the cross section 12a. In the above embodiment, the bolt 10 is a stud bolt, but is not limited to this and may be a bolt with a head. Although the engine body 100 and the flange portion 110 of the exhaust manifold are used as examples of members to be fastened, this is not limiting.

[0019] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0020] 10 Volts 12 Shaft 12a cross section 100 Engine body 110 Flange part

Claims

[Claim 1] A method for calculating a shear load of a bolt that fastens multiple members, comprising the steps of: Identifying the bending direction of the shank of the bolt based on a contour diagram showing tensile and compressive stresses in a cross section intersecting the axial direction of the shank of the bolt; Calculating shear stresses in the first direction at a plurality of points on an outer periphery of the cross section based on a contour diagram showing the shear stresses in the first direction at the cross section; Calculating shear stresses in the second direction at each of the plurality of points based on a contour diagram showing shear stresses in a second direction intersecting the first direction in the cross section; Calculating a shear load of the bolt based on a sum of a magnitude of a component in the bending direction of each of the shear stresses in the first direction at the plurality of points and a magnitude of a component in the bending direction of each of the shear stresses in the second direction at the plurality of points. How to calculate the shear load of a bolt.

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