Method for calculating the shear load of a 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 Art

[0002] Bolts may be used for fastening a plurality of members (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In designing such a bolt, it is preferable to consider the shear load acting on the bolt. However, calculating such a shear load has been complicated.

[0005] Therefore, an object of the present invention is to provide a method for calculating the shear load of a bolt that can be calculated by a simple method.

Means for Solving the Problems

[0006] The above objective can be achieved by a method for calculating the shear load of a bolt used to fasten multiple members, which involves: determining the bending direction of the shaft portion of the bolt based on a contour plot showing tensile and compressive stresses in a cross section intersecting the axial direction of the shaft portion of the bolt; calculating the shear stresses in the first direction at multiple points on the outer circumference of the cross section based on a contour plot showing the shear stresses in the first direction at the cross section; calculating the shear stresses in the second direction at multiple points based on a contour plot showing the shear stresses in the second direction intersecting the first direction at the cross section; and calculating the shear load of the bolt based on the sum of the magnitudes of the components in the bending direction of the shear stresses in the first direction at the multiple points and the magnitudes of the components in the bending direction of the shear stresses in the second direction at the multiple points. [Effects of the Invention]

[0007] According to the present invention, a method for calculating the shear load of a bolt that can be calculated using a simple method can be provided. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is an explanatory diagram of a bolt. [Figure 2] Figure 2 is a flowchart illustrating a method for calculating the shear load on a bolt. [Figure 3] Figure 3A is an example of a contour plot showing tensile and compressive stress in a cross-section, Figure 3B is an example of a contour plot showing shear stress in the X direction in a cross-section, and Figure 3C is an example of a contour plot showing shear stress in the Y direction in a cross-section. [Figure 4] Figure 4A is a graph showing the shear stress in the X direction and the shear stress in the Y direction acting at an arbitrary point on the outer circumference of the cross section, and Figure 4B is a graph showing the magnitude of the shear stress in the X direction σX and the shear stress in the Y direction σY. [Modes for carrying out the invention]

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

[0010] The exhaust manifold is connected to the exhaust pipe. Therefore, the flange portion 110 of the exhaust manifold is subjected to external forces from the exhaust pipe, causing displacement. This displacement is caused by the mass of the exhaust manifold, the mass of the exhaust pipe, and the resonance of the exhaust pipe. The excitation force for resonance is the vibration of the engine body 100. Due to the displacement generated in this way, a load is applied to the bolt 10 via the pipe portion and flange portion 110 of the exhaust manifold. Figure 1 shows the cross-section 12a of the shaft portion 12 of the bolt 10 in contact with the flange portion 110. The cross-section 12a is perpendicular to the axial direction of the shaft portion 12. The shear load acting from the flange portion 110 to the cross-section 12a is calculated by CAE (Computer Aided Engineering) analysis using 3D CAD data of the bolt 10 used in this application.

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

[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 the contour plot showing the X-direction shear stress σX at cross section 12a, the X-direction shear stress σX at every 1° from θ=0° to 359° on the outer circumference of cross section 12a is calculated by CAE analysis. Figure 3B is an example of a contour plot showing the X-direction shear stress σX at cross section 12a. In the example of Figure 3B, areas with darker hatching indicate high shear stress in the tensile direction, and areas with lighter hatching indicate high shear stress in the compressive direction. Note that the X-direction shear stress at any point on the outer circumference of cross section 12a is σX θ It can be expressed as follows. The component of this shear stress in the X direction in the bending direction D is σX θ It can be expressed as sinα. The X direction is one example of the first direction.

[0013] Similarly, the shear stress in the Y direction (hereinafter referred to as the Y-direction shear stress) σY is calculated (Step S3). Specifically, based on the contour plot showing the Y-direction shear stress σY at cross section 12a, the Y-direction shear stress σY at every 1° from θ=0° to 359° on the outer circumference of cross section 12a is calculated by CAE analysis. Figure 3C is an example of a contour plot showing the Y-direction shear stress σY at cross section 12a. Similarly in the example of Figure 3C, areas with darker hatching indicate high shear stress in the tensile direction, and areas with lighter hatching indicate high shear stress in the compressive direction. Note that the X-direction shear stress at any point on the outer circumference of cross section 12a is σY θ It can be expressed as follows. The component of this shear stress in the X direction in the bending direction D is σY θ It can be expressed as cosα. The Y direction is an example of a second direction.

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

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

[0016] Next, the shear load P acting on the shaft 12 is calculated based on the magnitude of the shear stress σX in the X direction |σX| and the magnitude of the shear stress σY in the Y direction |σY| (step S5). Specifically, the shear load P is calculated as the sum of the bending direction D component of the magnitude of the shear stress σX |σX| in the X direction and the sum of the bending direction D component of the magnitude of the shear stress σY |σY| in the Y direction. The shear load P is expressed by the following equation (1). TIFF0007859406000001.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. Also, although the flange portion 110 is fixed to the engine body 100 by such a plurality of bolts 10, the shared load borne by the bolts 10 can be predicted and an appropriate design can be made. Further, 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 it can also be used for calculating the free safety factor with respect to the fastening axial force of the bolt 10.

[0018] In the above embodiment, the shear stress was calculated every 1°, but it is not limited to 1°. In addition to the points on the outer periphery of the cross section 12a, the shear load P may be calculated using the magnitudes of the components in the bending direction D of the shear stress at a plurality of 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 it is not limited thereto, and a bolt having a head may be used. Although the engine body 100 and the flange portion 110 of the exhaust manifold are described as examples of the members to be fastened, it is not limited thereto.

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

Explanation of Signs

[0020] 10 Bolt 12 Shaft portion 12a Cross section 100 Engine body 110 Flange portion

Claims

[Claim 1] A method for calculating the shear load of a bolt used to fasten multiple members, Based on a contour plot showing the tensile and compressive stresses in a cross-section intersecting the axial direction of the bolt shaft, the bending direction of the shaft is determined. Based on the contour plot showing the shear stress in the first direction at the cross-section, the shear stress in the first direction at each of several points on the outer circumference of the cross-section is calculated. Based on the contour plot showing the shear stress in the second direction intersecting the first direction in the aforementioned cross-section, the shear stress in the second direction at each of the plurality of points is calculated. The shear load of the bolt is calculated based on the sum of the magnitude of the component in the bending direction of the shear stress in the first direction at each of the plurality of points, and the magnitude of the component in the bending direction of the shear stress in the second direction at each of the plurality of points. Method for calculating the shear load on a bolt.

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