JP2015108585A - Structural member evaluation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure member evaluation method capable of correctly reproducing flexure moment and axial force acting on an actual structural member, and evaluating correct intensity without deformation and frictional force due to input.SOLUTION: A strength arm 2 having a strength point offset to an axial line of an evaluation member 1 is attached to one or both ends of the evaluation member 1. In a state that the strength point is supported by a support point 3 such as a rolling bearing, test force such as tension or compression is applied to the strength point, thereby axial force of tension or compression is acted on the evaluation member 1 with flexure moment, simultaneously.

Description

  The present invention relates to a method for evaluating the strength of a structural member that receives bending and tensile / compressive forces.

  For example, automobiles are required to have a high-strength and lightweight vehicle body structure in order to achieve both collision performance and fuel consumption performance. For this purpose, it is necessary to reduce the weight of the structural member, to correctly evaluate the strength of the structural member, and to design an optimal structure. Optimal structural design requires a structural member evaluation method that can accurately reproduce the bending moment acting on an actual automobile in a collision or the like, and the axial force of tension / compression.

  As a method for evaluating the strength of the structural member, a bending test method as described in Patent Document 1 is common. As shown in FIG. 1, this method is a method in which a test piece is placed between support points and pressed. Thereby, a bending moment as shown as BMD (bending moment diagram) in FIG. 1 can be generated.

  However, this method can generate a bending moment in the test piece, but cannot simultaneously generate tensile and compressive axial forces. Further, when the applied pressure is increased, the support point and the pressurizing point are often deformed, and it is difficult to reproduce the actual input state of the automobile part. Furthermore, this method has a number of problems such that a sliding motion occurs at the support point and the pressurizing point during the test, and accuracy deterioration due to frictional force cannot be avoided.

Mechanical Engineering Handbook, 6th edition (edited by the Japan Society of Mechanical Engineers), 6th chapter, 13th chapter, material test, page 50

  Therefore, the object of the present invention is to solve the above-mentioned conventional problems, and to accurately reproduce the bending moment and axial force acting on the actual structural member, without the influence of deformation and friction of the input point and the support point. An object of the present invention is to provide a method for evaluating a structural member capable of accurate strength evaluation.

  The structural member evaluation method of the present invention made in order to solve the above-described problems is a force arm having a force point offset with respect to the axis of the evaluation member at the end of the evaluation member which is the structural member to be evaluated. , And a tensile or compressive test force is applied to the applied point while the applied point is supported by the supporting point, and a bending moment and an axial force are simultaneously applied to the evaluation member.

  The force arm can be attached only to one end of the evaluation member or to both ends. When attaching the attachment arm to both ends of the evaluation member, the attachment arm can be attached with an offset in the same direction or with an offset in the opposite direction. Further, the attachment arm can be attached by being offset non-parallel in a plane including the axis of the evaluation member, or can be attached by being offset in a direction away from the plane including the axis of the evaluation member. In addition, a rolling bearing can also be used for a support point.

  In the structural member evaluation method according to the present invention, an evaluation arm is attached to an end of the evaluation member with an application point offset with respect to its axis, and a tensile or compression test force is applied to the application point to bend the evaluation member. Moment and axial force can be applied simultaneously. Further, since there is no direct input to the evaluation part as in the prior art, there is no deformation due to input. In addition, since the test force is applied in a state where the applied force point is supported by a support point such as a rolling bearing, the influence of friction can be eliminated, and the strength of the structural member can be accurately evaluated. As a structural member, a member constituting a skeleton of an automobile is typical, but it goes without saying that the structural member can be applied to other general structural members.

  It should be noted that various bending moments can be applied to the evaluation member by changing the length and attachment method of the force arm. In addition, it is possible to apply a torsional moment simultaneously with bending by attaching the two force-applying arms so as to be offset in a direction away from the plane including the axis of the evaluation member.

It is explanatory drawing which shows the conventional bending test method. It is explanatory drawing and the bending moment figure which show the 1st Embodiment of this invention. It is explanatory drawing and the bending moment figure which show the 2nd Embodiment of this invention. It is explanatory drawing and bending moment figure which show the 3rd Embodiment of this invention. It is a perspective view which shows the 4th Embodiment of this invention. It is explanatory drawing of the cross-sectional position in the 4th Embodiment of this invention. It is a graph of the axial force in each cross-sectional position. It is a graph of X-moment in each cross-sectional position. It is a perspective view of an Example. It is explanatory drawing of the type 1 in an Example. It is explanatory drawing of the type 2 and type 3 in an Example. It is explanatory drawing of the cross-sectional position in an Example. It is a graph which shows the moment around each axis of X, Y, and Z in an example. It is a graph which shows the moment around each axis of X, Y, and Z in a case with twisting. 4 is a graph showing moments about X, Y, and Z axes in types 1, 2, and 3.

Embodiments of the present invention will be described below.
FIG. 2 shows a first embodiment of the present invention, in which 1 is an evaluation member, and an arm 2 is attached to both ends thereof. The evaluation member 1 may be the structural member itself to be evaluated, may be a part of the structural member to be evaluated which is to be evaluated, or may be a model of the structural member to be evaluated. Needless to say, according to the present invention, the entire structural member can be evaluated, but if the weak points of the structural member are known in advance, the entire structural member is not used and the same cross section as the weak point portion is used. It is also possible to evaluate the strength using a model having a shape as an evaluation member.

  The attachment arm 2 is firmly attached to the end of the evaluation member 1 by welding, rivets or the like so as not to rattle. It is desirable that the arm 2 has strength and rigidity that does not greatly deform due to the test force. In the first embodiment, the two force applying arms 2 are attached to both ends of the evaluation member 1 while being offset in the same direction within the same plane. A support point 3 is provided at the tip of the force arm 2, and the tensile force F is applied with the position of the support point 3 as the force point. In this embodiment, the axial force is the tensile force F, but it may be a compressive force.

  Assuming that the lengths of the two force applying arms 2 are L1 and L2, respectively, a bending moment as shown in the illustrated BMD is generated in the evaluation member 1. The bending moment at the left end of the evaluation member 1 is M1 = F × L1, and the bending moment at the right end of the evaluation member 2 is M2 = F × L2. Further, the axial force F acts over the entire length of the evaluation member 1.

  Since the bending moment and the axial force can be freely applied to the evaluation member 1 by changing the length of the force applying arm 2 and the axial force F in this way, the bending moment and the axial force that are applied to the actual structural member. Can be accurately reproduced. Further, since the axial force as the test force is input to the support point 3 and is not directly input to the evaluation member 1, the input point of the evaluation member 1 is not deformed as in the prior art. In addition, it is preferable to use a rolling bearing, for example, as a jig having a very small frictional resistance at the supporting point 3 because the influence of the frictional force can be ignored in practice. Therefore, accurate strength evaluation can be performed.

  FIG. 3 is a diagram showing a second embodiment of the present invention. In this embodiment, the attaching arm 2 is attached to only one end portion of the evaluation member 1, and a rolling bearing is directly attached to the other end portion of the evaluation member 1 as a support point 3. In this embodiment, a bending moment as shown by BMD in FIG. 3 can be applied to the evaluation member 1.

  FIG. 4 is a diagram showing a third embodiment of the present invention. In this embodiment, the two force applying arms 2 and 2 are attached to both ends of the evaluation member 1 while being offset in opposite directions. In this embodiment, as shown in the BMD of FIG. 4, it is possible to generate a bending moment that becomes zero in the middle and reverses the sign on both sides thereof.

  5 to 8 are diagrams showing a fourth embodiment of the present invention. The evaluation member 1 of this embodiment is a center pillar of an automobile. As shown in FIG. 6, the end on the ceiling side is rotatably supported, and the arm 2 is attached to the end on the floor surface side. This force arm 2 is a steel plate with ribs, and a rolling bearing is disposed as a support point 3 between the two ribs. This structure corresponds to the embodiment of FIG.

  In the fourth embodiment, an axial force is applied in the Z direction in FIG. 6 and the axial force and bending moment at each cross-sectional position numbered 48 to 53 in FIG. 6 are measured, and are shown in Table 7 and Table 8. . In these tables, the actual measurement values in the full vehicle test are also entered. The data in the method of the present invention almost coincided with the data in the full vehicle test, and it was confirmed that the strength evaluation similar to the full vehicle test can be performed in the method of the present invention.

  Next, a simple cylindrical member as shown in FIG. 9 is used as the evaluation member 1, and the attachment arm 2 is attached to the both ends of the evaluation member 1 in various directions via the plates 4. An axial force F was applied to the position, and the difference in the generated moments depending on how the attachment arm 2 was attached was confirmed.

  In this embodiment, as shown in FIG. 10, the experiment was performed by changing the length and direction of the two force applying arms 2. The case 1-1 and the case 1-2 are attached by offsetting them in a non-parallel manner within a plane including the axis of the evaluation member, although the lengths of the two force applying arms 2 are equal. Cases 1-3 and 1-4 are obtained by changing the lengths of the two force applying arms 2. Case 1-5 is offset in parallel within a plane including the axis of the evaluation member. Further, the case 2-1 and the case 2-3 are obtained by offsetting the two force applying arms 2 in a direction away from the plane including the axis of the evaluation member.

  Further, the type 2 shown in FIG. 11 is obtained by eliminating the one side arm 2 of FIG. 10, and the type 3 shown in FIG. 11 is the same as the type 1 in the length of the arm 2 but one side is placed in the opposite direction. It is offset.

  FIG. 12 shows the cross-sectional positions of the evaluation member 1, and the graph of FIG. 13 shows the results of measuring the moments around the X, Y, and Z axes at each cross-sectional position for each case. Since all the cases shown in FIG. 13 are obtained by offsetting the applied arm in the same plane including the axis of the evaluation member, no torsion has occurred, and the Y-moment and the Z-moment are naturally However, it is zero. The X-moment decreases naturally toward the right side in the case 1-3 and the case 1-4 in which the one side arm is shortened. However, in other cases, the data was duplicated, and there was no difference depending on the mounting direction of the force arm.

  FIG. 14 is a graph showing the results of measuring the moments about the X, Y, and Z axes for the standard type 1 and the cases 2-1 and 2-3 in which torsion occurs. In the case 2-1 and the case 2-3, the X-moment and the Z-moment change as the torsion occurs.

  FIG. 15 is a graph showing the measurement results for Type 1, Type 2, and Type 3 in the same manner. The contents are as described in the first, second, and third embodiments, and in the method of the present invention, it was confirmed that a theoretical moment was generated in the evaluation member.

1 Evaluation Member 2 Force Arm 3 Supporting Point 4 Plate

Claims (7)

  An attachment arm having an application point offset from the axis of the evaluation member is attached to the end of the evaluation member, which is the structural member to be evaluated, and the application point is pulled or compressed to the application point while the application point is supported by the support point. A method for evaluating a structural member, wherein a test force is applied and a bending moment and an axial force are simultaneously applied to the evaluation member.   The structural member evaluation method according to claim 1, wherein the attachment arm is attached only to one end of the evaluation member.   The structural member evaluation method according to claim 1, wherein the attachment arm is attached to both ends of the evaluation member while being offset in the same direction.   2. The structural member evaluation method according to claim 1, wherein the attachment arm is attached to both ends of the evaluation member while being offset in opposite directions.   The structural member evaluation method according to claim 3 or 4, wherein the attachment arm is attached by being offset non-parallelly in a plane including the axis of the evaluation member.   The structural member evaluation method according to claim 3 or 4, wherein the attachment arm is attached while being offset in a direction deviating from a plane including the axis of the evaluation member.   7. The structural member evaluation method according to claim 1, wherein a rolling bearing is used as the support point.