JP7260788B2 - Strength test method and strength test piece - Google Patents

Description

The present invention relates to a strength test method and a strength test piece.

Conventionally, a joint formed by overlapping two steel plates and spot-welding the overlapped portion is used as a test piece, and the test piece is clamped on a testing machine and pulled so that a shearing force acts on the spot-welded portion. There is a shear test method (Japanese Industrial Standards JIS Z3136: 1999) for determining the shear strength from the maximum tensile load until the test piece breaks.
There is also a tensile test method in which a test piece is clamped in a testing machine so that a tensile force acts on the spot welded portion and the tensile strength is obtained from the maximum tensile load until the test piece breaks.
In addition, there is a cross tension test method in which a test piece is clamped to a testing machine and pulled so that peeling force acts on the spot weld, and the cross tension force (peel strength) is obtained from the maximum tensile load until the test piece breaks. (Patent Document 1).

JP 2017-125698 A

However, each conventional strength test method evaluates the strength of a joint under a specific load condition, e.g., under a compound load condition where shear and tensile forces act simultaneously. The joint strength could not be properly evaluated.

An object of the present invention is to provide a strength test method and a strength test piece that can appropriately evaluate the strength of a joint under a complex load state in view of the problems of the background art described above.

The gist of the present invention is as follows.

(1) A strength test method according to an aspect of the present invention is a strength test method for evaluating the strength of a joint, comprising a rod-shaped first test piece and a rod-shaped second test piece overlapping the first test piece. , a joint portion for joining the first test piece and the second test piece, a preparation step of preparing a strength test piece, and one end portion in the longitudinal direction of the first test piece and the second test piece A gripping step of gripping with one chuck of the tensile tester and gripping the other end in the longitudinal direction of the first test piece and the second test piece with the other chuck of the tensile tester, and the first test piece and a pulling step of pulling the second test piece in the longitudinal direction, and in the pulling step, a tensile force that pulls the first test piece in one direction and a tensile force that pulls the first test piece in the other direction. The resultant force is different from the resultant force of the tensile force that pulls the second test piece to one side and the tensile force that pulls the second test piece to the other side.
(2) In (1) above, the joint may be a welded portion.
(3) In (2) above, the welded portion may be a spot welded portion.
(4) In any one of (1) to (3) above, perpendicular to the longitudinal direction of the first test piece and the second test piece in adjacent ranges up to equal distances from the joint on both sides in the longitudinal direction The cross-sectional area in the plane perpendicular to the longitudinal direction of the first test piece and the second test piece in other portions may be smaller than the cross-sectional area in the plane perpendicular to the longitudinal direction.
(5) In any one of the above (1) to (4), in the pulling step, the first test piece and the second test piece are peeled off. You can apply force.
(6) In any one of the above (1) to (5), in the preparation step, a spacer is sandwiched between the first test piece and the second test piece at a position different from the joint good.
(7) In any one of the above (1) to (6), the cross-sectional area in the plane perpendicular to the longitudinal direction at an intermediate position from one end of the first test piece to the joint is the first test It may be smaller than the cross-sectional area in a plane perpendicular to the longitudinal direction at an intermediate position from the other end of the piece to the joint.
(8) In any one of the above (1) to (7), the cross-sectional area in the plane perpendicular to the longitudinal direction at an intermediate position from one end of the second test piece to the joint is the second test It may be larger than the cross-sectional area in a plane perpendicular to the longitudinal direction at an intermediate position from the other end of the strip to the joint.
(9) In any one of (1) to (8) above, the tensile strength of the first test piece and the tensile strength of the second test piece may be different.
(10) A strength test piece according to one aspect of the present invention is a strength test piece for evaluating the strength of a joint, comprising a rod-shaped first test piece and a rod-shaped second test piece overlapping the first test piece. A piece and a joint for joining the first test piece and the second test piece, wherein the first test piece and the second test piece are longitudinally gripped by one chuck of a tensile tester It has one end in the direction and the other end in the longitudinal direction that is gripped by the other chuck of the tensile tester, a tensile force that pulls the first test piece to one side, and the first test piece to the other The resultant force of the tensile force that pulls the second test piece to one side is different from the resultant force of the tensile force that pulls the second test piece to one side and the tensile force that pulls the second test piece to the other side.
(11) In (10) above, the joint may be a weld.
(12) In (11) above, the welded portion may be a spot welded portion.
(13) In any one of the above (10) to (12), perpendicular to the longitudinal direction of the first test piece and the second test piece in the adjacent range from the joint to the same distance on both sides in the longitudinal direction The cross-sectional area in the plane perpendicular to the longitudinal direction of the first test piece and the second test piece in other portions may be smaller than the cross-sectional area in the plane perpendicular to the longitudinal direction.
(14) In any one of (10) to (13) above, the strength test piece includes a spacer between the first test piece and the second test piece at a position different from the joint. you can
(15) In any one of (10) to (14) above, the cross-sectional area in the plane perpendicular to the longitudinal direction at an intermediate position from one end of the first test piece to the joint is It may be smaller than the cross-sectional area in a plane perpendicular to the longitudinal direction at an intermediate position from the other end of the piece to the joint.
(16) In any one of (10) to (15) above, the cross-sectional area in the plane perpendicular to the longitudinal direction at an intermediate position from one end of the second test piece to the joint portion is the second test piece It may be larger than the cross-sectional area in a plane perpendicular to the longitudinal direction at an intermediate position from the other end of the strip to the joint.
(17) In any one of (10) to (16) above, the tensile strength of the first test piece and the tensile strength of the second test piece may be different.

The strength test method of the present invention can provide a strength test method and a strength test piece that can appropriately evaluate the strength of a joint under multiple load conditions.

It is a schematic diagram showing a model of a strength test method concerning a 1st embodiment. It is a perspective view which shows the strength test piece which concerns on 1st Embodiment. It is an explanatory view showing a strength test piece concerning a 1st embodiment. It is a perspective view which shows the strength test piece which concerns on 2nd Embodiment. It is explanatory drawing which shows the strength test piece which concerns on 2nd Embodiment. FIG. 11 is a perspective view showing a strength test piece according to a third embodiment; It is explanatory drawing which shows the strength test piece which concerns on 3rd Embodiment. It is a schematic diagram showing a model of a strength test method concerning a 3rd embodiment.

A strength test method common to the following embodiments is a strength test method for evaluating joint strength. A joint is a joint between two or more members, for example, a joint between structural members in a product such as a vehicle. The joint may be a weld or may be a spot weld. A strength test method is performed by a tensile tester (not shown) using a strength test piece that simulates a joint in a product.

The tensile tester has one chuck for gripping one end of the strength test piece and the other chuck for gripping the other end of the strength test piece. In the tensile tester, one end of the strength test piece is held by one chuck and the other end of the strength test piece is held by the other chuck. It is displaced. Then, the tensile tester pulls the strength test piece to apply tensile force to the strength test piece. Tensile testers typically measure the test load acting on the chuck until the strength test piece fails or breaks.
In the following, unless otherwise specified, the load (force) assumes that the force directed from the other end Q to the one end P (the right side in FIGS. 1 and 8) is positive (+), and the one end P to the other end A force directed toward Q (left side in FIGS. 1 and 8) is assumed to be negative (-).

(First embodiment)
A strength test method and a strength test piece according to the first embodiment will be described with reference to FIGS. 1 to 3. FIG.
FIG. 1 is a schematic diagram showing a model of a strength test method according to the first embodiment. FIG. 2 is a perspective view showing a strength test piece according to the first embodiment. FIG. 3 is an explanatory diagram showing a strength test piece according to the first embodiment. In FIG. 3, the upper center view is a front view of the strength test piece, the upper left view is a cross-sectional view of the rightward arrow in the upper center view, and the upper right view is the leftward arrow in the upper center view. It is a cross-sectional view, the middle central view is a front view of the first test piece, the middle left diagram is a cross-sectional view of the rightward arrow part in the middle central diagram, and the middle right diagram is the leftward arrow part in the middle central diagram. It is a cross-sectional view, the lower center view is a front view of the second test piece, the lower left view is a cross-sectional view of the right arrow part in the lower center view, and the lower right view is the left arrow view of the lower center view. It is a sectional view.

As shown as a model in FIG. 1, in the strength test method according to the first embodiment, one end portion P of a strength test piece 10 is held by one chuck Ca of a tensile tester, and the strength test piece 10 is held by the other chuck Cb. One chuck Ca and the other chuck Cb are displaced in a direction away from each other (left and right directions in FIG. 1) while gripping the other end Q of the two. When the chuck Ca on one side and the chuck Cb on the other side are displaced away from each other, a test load F acts on the one end P and the other end Q of the strength test piece 10 .

(strength test piece)
A strength test piece 10 is for evaluating the strength of a joint. As shown in FIGS. 2 and 3, the strength test piece 10 includes a rod-shaped first test piece 11, a rod-shaped second test piece 12 overlapping the first test piece 11, and the first test piece 11 and the second test piece. and a joint J10 that joins the piece 12 . In addition, the 1st test piece 11 and the 2nd test piece 12 may be plate-shaped, respectively.

The first test piece 11 is preferably made of the same material as the joint to be simulated, such as steel. As shown in FIG. 3, the first test piece 11 has one side 11a, the other side 11b, and a first welded portion J11 between the one side 11a and the other side 11b.

The second test piece 12 is preferably made of the same material as the joint to be simulated, for example steel. The second test piece 12 has one side 12a, the other side 12b, and a second welded portion J12 between the one side 12a and the other side 12b.

In addition, the first test piece 11 and the second test piece 12 are made of different materials (steel members with different mechanical properties such as tensile strength, steel and aluminum alloy, etc.) according to the joint to be simulated. different members, etc.).

The first test piece 11 and the second test piece 12 overlap each other over the longitudinal direction of the strength test piece 10 (the direction of the test load F). The first test piece 11 and the second test piece 12 have one end P in the longitudinal direction held by one chuck Ca of the tensile tester, and the other end Q in the longitudinal direction by the other chuck of the tensile tester. Grasped. The first test piece 11 and the second test piece 12 are joined together at one end P and the other end Q by a joining means C such as spot welding.

The joint J10 may be a mechanical joint in which the first test piece 11 and the second test piece 12 are mechanically joined by bolts, rivets, or the like, or may be a welded portion in which the first test piece 11 and the second test piece 12 are joined by welding. It may be a spot welded portion joined by The joint J10 is a portion where the first joint J11 of the first test piece 11 and the second joint J12 of the second test piece 12 are joined. By using the joint J10 as the welded portion, it is possible to conduct a strength test simulating the joint of the product when the joint is the welded portion. Further, by using the joint J10 as the spot-welded portion, it is possible to conduct a strength test simulating a joint of a product that is a spot-welded portion.

Regarding the tensile stiffness in the longitudinal direction of the first test piece 11, the tensile stiffness K1b on the other side 11b is greater than the tensile stiffness K1a on the one side 11a with the junction J10 as the boundary in the longitudinal direction.

Specifically, one side 11a of the first test piece 11 has a smaller cross-sectional area than the other side 11b in a plane perpendicular to the longitudinal direction.
More specifically, one side 11a of the first test piece 11 has the same plate thickness t11a along the longitudinal direction. Similarly, the other side 11b of the first test piece 11 has the same plate thickness t11b over the longitudinal direction. One side 11a of the first test piece 11 has a plate width B11a smaller than the plate width B11b of the other side 11b. A plate width B11a of one side 11a of the first test piece 11 is equal in the longitudinal direction. Similarly, the plate width B11b of the other side 11b of the first test piece 11 is equal in the longitudinal direction.

That is, the cross-sectional areas of the one side 11a of the first test piece 11 on the plane perpendicular to the longitudinal direction are equal in the longitudinal direction. Similarly, the cross-sectional area of the other side 11b of the first test piece 11 on the plane perpendicular to the longitudinal direction is equal in the longitudinal direction.
The tensile stiffness K1a of the one side 11a of the first test piece 11 is proportional to the length from the joint J10 to the one end P. Similarly, the tensile stiffness K1b of the other side 11b of the first test piece 11 is proportional to the length from the joint J10 to the other end Q.
Therefore, the tensile stiffness K1a of the one side 11a and the tensile stiffness K1b of the other side 11b of the first test piece 11 are variable by adjusting the length.

As shown in FIG. 3, a cross-sectional area A11a in a plane perpendicular to the longitudinal direction at an intermediate position from one end P of the first test piece 11 to the joint J10 is It is smaller than the cross-sectional area A11b in the plane perpendicular to the longitudinal direction at the intermediate position up to the portion J10.

On the other hand, the cross-sectional area A12a in the plane perpendicular to the longitudinal direction at the intermediate position from the one end P of the second test piece 12 to the joint J10 is larger than the cross-sectional area A12b in the plane perpendicular to the longitudinal direction at an intermediate position to . In addition, when the position of the one end P or the other end Q is unknown when the strength test piece 10 is viewed alone, instead of "one end P", "one end of the strength test piece 10" , and instead of the "other end Q", the "middle position" may be defined as the "othermost end of the strength test piece 10". In addition, when the strength test piece 10 is viewed alone, if the range of the joint J10 is unknown, instead of the “joint J10”, the “longitudinal center of the strength test piece 10” is used. " may be specified.

As a result, as shown in FIG. 1, the test load F is a tensile force F1a (=F×K1a/(K1a+K2a)) on one side 11a of the first test piece 11 according to the ratio of the tensile stiffness K1a and the tensile stiffness K2a. ) and the tensile force F2a (=F×K2a/(K1a+K2a)) on one side 12a of the second test piece 12 . Similarly, the test load F is applied to the tensile force F1b on the other side 11b of the first test piece 11 and the tensile force F2b on the other side 12b of the second test piece 12 according to the ratio of the tensile stiffness K1b and the tensile stiffness K2b. distributed. Therefore, the resultant force of the tensile force F1a and the tensile force F1b has a negative value (the leftward force has a positive value in FIG. 1), and the tensile force F2a has a positive value (the rightward force has a positive value in FIG. 1). and the resultant force of the tensile force F2b.

At the transition portion from the one side 11a of the first test piece 11 to the joint J10, the plate width B11a increases from the one end P toward the other end Q. Specifically, at the transition portion, the plate width B11a is continuously increased from the one end portion P toward the other end portion Q. As shown in FIG. As a result, stress concentration can be prevented, and the transition portion can be prevented from breaking before the joint J10.

Next, the second test piece 12 will be explained. Regarding the tensile stiffness in the longitudinal direction of the second test piece 12, the tensile stiffness K2b of the other side 12b is smaller than the tensile stiffness K2a of the one side 12a with the junction J10 as the boundary in the longitudinal direction.

Specifically, one side 12a of the second test piece 12 has a larger cross-sectional area in a plane perpendicular to the longitudinal direction than the other side 12b.

More specifically, one side 12a of the second test piece 12 has a uniform plate thickness t12a over the longitudinal direction. Similarly, the other side 12b of the second test piece 12 has the same plate thickness t12b over the longitudinal direction. One side 12a of the second test piece 12 has a plate width B12a larger than the plate width B12b of the other side 12b. A plate width B12a of one side 12a of the second test piece 12 is equal in the longitudinal direction. Similarly, the plate width B12b of the other side 12b of the second test piece 12 is equal in the longitudinal direction.

That is, the cross-sectional area of the one side 12a of the second test piece 12 on the plane perpendicular to the longitudinal direction is uniform over the longitudinal direction. Similarly, the cross-sectional area of the other side 12b of the second test piece 12 on a plane perpendicular to the longitudinal direction is the same throughout the longitudinal direction.

The tensile stiffness K2a of the one side 12a of the second test piece 12 is proportional to the length from the joint J10 to the one end P. Similarly, the tensile stiffness K2b of the other side 12b of the second test piece 12 is proportional to the length from the joint J10 to the other end Q.
Therefore, the tensile stiffness K2a of the one side 12a and the tensile stiffness K2b of the other side 12b of the second test piece 12 are variable by adjusting the length.

At the transition portion from the other side 12b of the second test piece 12 to the joint J10, the plate width B12b increases from the other end Q toward the one end P. Specifically, the plate width B12b is continuously increased from the other end portion Q toward the one end portion P at the transition portion. As a result, stress concentration can be prevented, and the transition portion can be prevented from breaking before the joint J10.

The tensile strength of the first test piece 11 and the tensile strength of the second test piece 12 may be different. As a result, the strength test piece 10 and strength test method can be simulated in line with the product joint.

The first test piece 11 and the second test piece 12 may have a shape symmetrical in the longitudinal direction (symmetrical shape in FIG. 3). As a result, the first test piece 11 and the second test piece 12 having the same shape are manufactured, one of them is reversed in the longitudinal direction, and the strength test piece 10 is manufactured after overlapping the two over each other in the longitudinal direction. Therefore, the manufacturing cost of the strength test piece 10 can be reduced.

As described above, according to the strength test piece 10 according to one embodiment, by adjusting the shapes of the first test piece 11 and the second test piece 12 constituting the strength test piece 10, the tensile force is applied to the joint J10. The strength test of the joint can be performed in a state where the shear force and the shear force are applied in combination. Therefore, it is possible to appropriately evaluate the strength of the joint under multiple load conditions.

The shapes of the first test piece 11 and the second test piece 12 may be adjusted as follows. For example, the respective cross-sectional areas of the first test piece 11 and the second test piece 12 may be adjusted by varying the plate thicknesses of the first test piece 11 and the second test piece 12 . As a result, for example, it is possible to simulate a combination of plate members that form a joint in an actual structural member of a vehicle, and it is possible to evaluate the joint more realistically.

(Strength test method)
The strength test method according to the first embodiment is performed as follows on the strength test piece 10 as described above. The strength test method according to the first embodiment will be described below together with the effect on the strength test piece 10 .
(1) First, a rod-shaped first test piece 11, a rod-shaped second test piece 12 overlapping the first test piece 11, a joint J10 that joins the first test piece 11 and the second test piece 12, Prepare a strength test piece 10 containing (preparation step).

(2) Next, one end P in the longitudinal direction of the first test piece 11 and the second test piece 12 is gripped by one chuck Ca of the tensile tester, and the longitudinal direction of the first test piece 11 and the second test piece 12 is measured. The other end Q in the direction is gripped by the other chuck Cb of the tensile tester (gripping step).

(3) Then, the first test piece 11 and the second test piece 12 are pulled in the longitudinal direction (pulling step).

In this tensile step, as shown in FIG. The resultant force of the tensile force F2a that pulls the second test piece 12 in one direction and the tensile force F2b that pulls the second test piece 12 in the other direction should be different. The relationship of these resultant forces can be represented by (F1a+F1b)≠(F2a+F2b). The tensile force F1a that pulls the first test piece 11 to one side is the tensile force that pulls the first joint portion J11 toward the one end portion P of the one side 11a of the first test piece 11 . The tensile force F1b pulling the first test piece 11 to the other side is the tensile force with which the other side 11b of the first test piece 11 pulls the first joint J11 toward the other end Q. The tensile force F2a that pulls the second test piece 12 to one side is the tensile force that pulls the second joint J12 toward the one end portion P of the one side 12a of the second test piece 12 . The tensile force F2b that pulls the second test piece 12 to the other side is the tensile force that pulls the second joined portion J12 toward the other end portion Q by the other side 12b of the second test piece 12 .

Here, the resultant force of the tensile force F1a that pulls the first test piece 11 to one side and the tensile force F1b that pulls the first test piece 11 to the other side is the tensile force F2a that pulls the second test piece 12 to one side. Different from the resultant force of the tensile force F2b that pulls the second test piece 12 to the other side means that considering the strain measurement error for calculating the tensile force, the shape error of the strength test piece 10, etc., substantially shall mean different by 1% or more.

For example, when the tensile force F1a, the tensile force F1b, the tensile force F2a, and the tensile force F2b are 50 kN, -200 kN, 250 kN, and -100 kN, respectively, the resultant force of the tensile force F1a and the tensile force F1b is -150 kN. Yes, and the resultant force of the tensile force F2a and the tensile force F2b is +150 kN. Therefore, the resultant force of the tensile force F1a and the tensile force F1b is different from the resultant force of the tensile force F2a and the tensile force F2b. That is, (F1a+F1b)≠(F2a+F2b).

In this way, when the first test piece 11 and the second test piece 12 are pulled in the longitudinal direction with the test load F, the one side 11a and the other side 11b of the first test piece 11 and the one side 12a and the second test piece 12 Since the magnitudes of the respective tensile stiffnesses K1a, K1b, K2a, and K2b on the other side 12b are different, the resultant force of the tensile forces acting on the first joined portion J11 of the joint J10 and the tensile force acting on the second joined portion J12 An imbalance occurs in the resultant force of

Then, in the first joint J11, the tensile force F1a that pulls the first test piece 11 to one side and the tensile force F1b that pulls the first test piece 11 to the other side are compared, and the tensile force F1b having a large scalar amount corresponds to A tensile force acting on the

In addition, at the second joint J12, the tensile force F2a that pulls the second test piece 12 to one side and the tensile force F2b that pulls the second test piece 12 to the other side are compared, and the tensile force F2a having a large scalar amount corresponds to A tensile force acting on the

At the same time, the joint J10, that is, between the first joint J11 and the second joint J12, has a tensile force F1a that pulls the first test piece 11 to one side and a tensile force F1a that pulls the first test piece 11 to the other. A shearing force τ corresponding to the resultant force (F1a+F1b) with the tensile force F1b that pulls on acts. Also, a shear force τ corresponding to the resultant force (F2a+F2b) of the tensile force F2a pulling the second test piece 12 to one side and the tensile force F2b pulling the second test piece 12 to the other side acts.
As described above, according to the strength test method according to the embodiment, the joint strength test can be performed in a state in which the joint J10 is subjected to combined tensile force and shear force. Therefore, it is possible to appropriately evaluate the strength of the joint under multiple load conditions.

The tensile forces F11a, F11b, F12a, and F12b of the one side 11a and the other side 11b of the first test piece 11 and the one side 12a and the other side 12b of the second test piece 12 constituting the strength test piece 10 are A gauge for measuring the strain in the material axial direction of each member is attached in a state where the test load F is not applied to the strength test piece 10, and the strain is measured when the test load F is applied to the strength test piece 10. It can be calculated by multiplying the strain obtained by multiplying the cross-sectional area of the surface perpendicular to the axial direction of the part where the gauge is attached and the elastic modulus (Young's modulus) of the member.

In particular, the tensile force F11a is obtained by attaching a gauge to the intermediate position from the one end P of the first test piece 11 to the joint J10, and measuring the strain at the intermediate position and the strain on the surface perpendicular to the longitudinal direction at the intermediate position. It is preferable to calculate using the cross-sectional area. Tensile force F11b is obtained by attaching a gauge to the intermediate position from the other end Q of the first test piece 11 to the joint J10, strain at the intermediate position, and cross section at the intermediate position perpendicular to the longitudinal direction. It is preferable to calculate using the area. Tensile force F12a is obtained by attaching a gauge to the intermediate position from one end P of the second test piece 12 to the joint J10, strain at the intermediate position, and cross-sectional area at the intermediate position perpendicular to the longitudinal direction should be calculated using The tensile force F12b is obtained by attaching a gauge to the intermediate position from the other end Q of the second test piece 12 to the joint J10, and measuring the strain at the intermediate position and the cross section at the intermediate position perpendicular to the longitudinal direction. It is preferable to calculate using the area.

In addition, for each of the one side 11a and the other side 11b of the first test piece 11 and the one side 12a and the other side 12b of the second test piece 12 constituting the strength test piece 10, strain in the material axial direction A gauge for measuring is attached, a relational expression between the strain and tensile force measured when a tensile force is applied to each unit is obtained, and a test load F is applied to the strength test piece 10. The tensile forces F11a, F11b, F12a, and F12b may be calculated from the strain measured at the time and the obtained relational expression.

(Second embodiment)
Next, a strength test method according to the second embodiment will be described. The strength test method according to the second embodiment differs from the strength test method according to the first embodiment mainly in the structure of the strength test piece. In the following, explanations of parts common to the first embodiment may be omitted.
FIG. 4 is a perspective view showing a strength test piece according to the second embodiment. FIG. 5 is an explanatory diagram showing a strength test piece according to the second embodiment. In FIG. 5, the upper center view is a front view of the strength test piece, the upper left view is a cross-sectional view of the rightward arrow in the upper center view, and the upper right view is the leftward arrow in the upper center view. It is a cross-sectional view, the middle central view is a front view of the first test piece, the middle left diagram is a cross-sectional view of the rightward arrow part in the middle central diagram, and the middle right diagram is the leftward arrow part in the middle central diagram. It is a cross-sectional view, the lower center view is a front view of the second test piece, the lower left view is a cross-sectional view of the right arrow part in the lower center view, and the lower right view is the left arrow view of the lower center view. It is a sectional view.

A strength test piece 20 according to the second embodiment is for evaluating the strength of a joint. As shown in FIGS. 4 and 5, the strength test piece 20 according to the second embodiment includes a rod-shaped first test piece 21, a rod-shaped second test piece 22 overlapping the first test piece 21, and a first test piece 22. and a joint J20 that joins the piece 21 and the second test piece 22 . In addition, the 1st test piece 21 and the 2nd test piece 22 may be plate-shaped, respectively.

Here, the cross-sectional areas A21a, A21b, A22a, and A22b of the first test piece 21 and the second test piece 22 in the adjacent range E up to the same distance from the joint J20 on both sides in the longitudinal direction are , smaller than the cross-sectional area of the first test piece 21 and the second test piece 22 in the plane perpendicular to the longitudinal direction of the other portion. As a result, the stress can be concentrated most in the portions adjacent to both sides of the joint J20 in the longitudinal direction, so that the joint J20 can be damaged or destroyed before other portions of the strength test piece 20 are damaged or destroyed. can be pulled until

Regarding the tensile stiffness in the longitudinal direction of the first test piece 21, the tensile stiffness K1b on the other side 21b is greater than the tensile stiffness K1a on the one side 21a with the junction J20 as the boundary in the longitudinal direction.

Specifically, one side 21a of the first test piece 21 is longer than the other side 21b in a longitudinal section having a smaller cross-sectional area on a plane perpendicular to the longitudinal direction.

More specifically, one side 21a of the first test piece 21 has the same plate thickness t21a over the longitudinal direction. Similarly, the other side 21b of the first test piece 21 has the same plate thickness t21b over the longitudinal direction. The plate width of one side 21a of the first test piece 21 is equal in a relatively short range from one end P to the other end Q, and then gradually decreases until the position of the first joint J21. The plate width B21a is uniform over a relatively long range. On the other hand, the plate width of the other side 21b of the first test piece 21 is uniform over a relatively long range from the other end Q toward the one end P, and then gradually decreases from there until the first welded portion J21. The plate width B21b is equal in a relatively short range up to the position of .

Regarding the tensile stiffness in the longitudinal direction of the second test piece 22, the tensile stiffness K2b of the other side 22b is smaller than the tensile stiffness K2a of the one side 22a with the junction J20 as the boundary in the longitudinal direction.

Specifically, one side 22a of the second test piece 22 is shorter than the other side 22b in a longitudinal section having a smaller cross-sectional area on a plane perpendicular to the longitudinal direction.

More specifically, one side 22a of the second test piece 22 has a uniform plate thickness t22a over the longitudinal direction. Similarly, the other side 22b of the second test piece 22 has a uniform plate thickness t22b over the longitudinal direction. The plate width of one side 22a of the second test piece 22 is equal in a relatively long range from one end P to the other end Q, and then gradually decreases until the position of the second welded portion J22. The plate width B22a is equal in a relatively short range. On the other hand, the plate width of the other side 22b of the second test piece 22 is equal in a relatively short range from the other end Q toward the one end P, and then gradually decreases from there until the second welded portion J22. The plate width B22b is equal in a relatively long range up to the position of .

The first test piece 21 and the second test piece 22 may have a shape symmetrical in the longitudinal direction (symmetrical shape in FIG. 5). As a result, the first test piece 21 and the second test piece 22 having the same shape are manufactured, one of them is reversed in the longitudinal direction, and the strength test piece 20 is manufactured after overlapping the two over each other in the longitudinal direction. Therefore, the manufacturing cost of the strength test piece 20 can be reduced.

As described above, according to the strength test piece 20 according to one embodiment, by adjusting the shapes of the first test piece 21 and the second test piece 22 constituting the strength test piece 20, the tensile force is applied to the joint J20. The strength test of the joint can be performed in a state where the shear force and the shear force are applied in combination. Furthermore, since the adjacent range E of the joint J20 is set as the next most fragile portion after the joint J20, it is possible to prevent damage or breakage of other portions of the strength test piece 20 than the joint J20. Therefore, it is possible to appropriately evaluate the strength of the joint under multiple load conditions.

(Third Embodiment)
Next, a strength test method according to the third embodiment will be described. The strength test method according to the third embodiment differs from the strength test methods according to the first and second embodiments mainly in the structure of the strength test piece. In the following, explanations of parts common to the first embodiment and the second embodiment may be omitted.
FIG. 6 is a perspective view showing a strength test piece according to the third embodiment. FIG. 7 is an explanatory diagram showing a strength test piece according to the third embodiment. FIG. 8 is a schematic diagram showing a model of a strength test method according to the third embodiment. In FIG. 7, the upper center view is a front view of the strength test piece, the upper left view is a cross-sectional view of the rightward arrow in the upper center view, and the upper right view is the leftward arrow in the upper center view. It is a cross-sectional view, the middle central view is a front view of the first test piece, the middle left diagram is a cross-sectional view of the rightward arrow part in the middle central diagram, and the middle right diagram is the leftward arrow part in the middle central diagram. It is a cross-sectional view, the lower center view is a front view of the second test piece, the lower left view is a cross-sectional view of the right arrow part in the lower center view, and the lower right view is the left arrow view of the lower center view. It is a sectional view.

A strength test piece 30 according to the third embodiment is for evaluating the strength of a joint. As shown in FIGS. 6 and 7, the strength test piece 30 according to the third embodiment includes a rod-shaped first test piece 31, a rod-shaped second test piece 32 overlapping the first test piece 31, and a first test piece 32. and a joint J30 that joins the piece 31 and the second test piece 32 . In addition, the 1st test piece 31 and the 2nd test piece 32 may be plate-shaped, respectively.

The strength test piece 30 according to the third embodiment further includes spacers 33 and 34 between the first test piece 31 and the second test piece 32 at positions different from the joint J30.
The spacers 33 and 34 have rigidity to such an extent that when the strength test piece 30 is subjected to the test load F, they are crushed in the plate thickness direction and are not greatly deformed. Spacers 33, 34 may be made of steel, for example.

The spacer 33 is sandwiched between the one side 31a of the first test piece 31 and the one side 32a of the second test piece 32, and the one side 31a of the first test piece 31 and the second test piece 32 are arranged. It is fixed so as to be integrated with one side 32 a of the piece 32 .

Similarly, the spacer 34 is sandwiched between the other side 31b of the first test piece 31 and the other side 32b of the second test piece 32, and the other side 31b of the first test piece 31 and the other side 31b of the second test piece 32 It is fixed so as to be integrated with the other side 32 b of the second test piece 32 .

As described above, in the joint portion J30, the first joint portion J31 and the second joint portion J32 are joined in a state of being in direct contact with each other. Spacers 33 and 34 are arranged between the first test piece 31 and the second test piece 32 . Then, as shown in FIG. 6, part of the first test piece 31 and the second test piece 32 is tilted with respect to the direction of the test load F from the junction J30 to the spacers 33 and 34 . That is, the directions of the respective forces F1a, F2a, F1b and F2b are inclined with respect to the direction of the test load F, as shown in FIG. Therefore, the resultant force (vector) of F1a and F1b has a component in the peeling direction (perpendicular to the direction of the test load F), and similarly, the resultant force of F2a and F2b has a peeling direction component. Therefore, the peeling force R (the force in the direction in which the first part to be joined J31 and the second part to be joined J32 are separated from each other) can be applied to the joining part J30. Further, the peeling force can be adjusted by varying the plate thickness of the spacers 33 and 34 and the position of the spacers 33 and 34 on the joint J30 side according to the peeling force to be simulated (reproduced). Either the spacer 33 or the spacer 34 may be provided according to the peeling force to be simulated (reproduced).

As described above, according to the strength test piece 30 according to one embodiment, by providing the spacers 33 and 34 between the first test piece 31 and the second test piece 32 constituting the strength test piece 30, the joint J30 In addition, the strength test of the joint can be performed under the condition that the tensile force, the shear force, and the peel force are applied in a composite manner. Therefore, it is possible to appropriately evaluate the strength of the joint under multiple load conditions.

(Other embodiments)
Although the strength test pieces 10, 20, and 30 according to one aspect of the present invention have been described in the above embodiments, the strength test pieces are not limited to these.
For example, the strength test piece 10 according to the first embodiment may include the spacers 33, 34 of the strength test piece 30 according to the third embodiment.
For example, in the strength test piece, the resultant force of the tensile force that pulls the first test piece to one side and the tensile force that pulls the first test piece to the other side is the tensile force that pulls the second test piece to one side and the second test piece. What is necessary is just to differ from the resultant force with the tensile force which pulls to the other. In other words, the strength test piece should just satisfy the relationship between the tensile forces F1a, F1b, F2a, and F2b (F1a+F1b)≠(F2a+F2b). That is, the relationship between the tensile stiffnesses K1a, K1b, K2a, and K2b should satisfy {K1a/(K1a+K2a)+K1b/(K1b+K2b)}≠{K2a/(K1a+K2a)+K2b/(K1b+K2b)}.

(effect)
According to one aspect of the present invention, a strength test method for evaluating the strength of a joint, comprising: a rod-shaped first test piece; a rod-shaped second test piece overlapping the first test piece; A preparation step for preparing a strength test piece including a joint portion that joins the 2 test pieces, and one end in the longitudinal direction of the first and second test pieces are gripped with one chuck of the tensile tester, A gripping step of gripping the other end in the longitudinal direction of the first test piece and the second test piece with the other chuck of the tensile tester, and a tensile step of pulling the first test piece and the second test piece in the longitudinal direction. In addition, in the tensile step, the resultant force of the tensile force that pulls the first test piece to one side and the tensile force that pulls the first test piece to the other side is the tensile force that pulls the second test piece to one side and the second test piece to the other side. It is different from the resultant force with the tensile force that pulls on. Thereby, both ends of the first test piece and the second test piece constituting the strength test piece are grasped and pulled by the tensile tester, so that tensile force and shear force are applied to the joint portion at the same time. Therefore, it is possible to provide a strength testing method capable of appropriately evaluating the strength of a joint under a complex load condition.
According to one aspect of the present invention, a strength test piece for evaluating the strength of a joint, comprising a rod-shaped first test piece, a rod-shaped second test piece overlapping the first test piece, and the first test piece and a joint that joins the second test piece, the first test piece and the second test piece have one end in the longitudinal direction gripped by one chuck of the tensile tester, and the tensile tester The resultant force of the tensile force that pulls the first test piece to one side and the tensile force that pulls the first test piece to the other side is the second test piece It is different from the resultant force of the tensile force pulling to one side and the tensile force pulling the second test piece to the other side. Thereby, both ends of the first test piece and the second test piece constituting the strength test piece are grasped and pulled by the tensile tester, so that tensile force and shear force are applied to the joint portion at the same time. Therefore, it is possible to provide a strength test piece that can appropriately evaluate the strength of a joint under multiple load conditions.

10, 20, 30 Strength test piece 11, 21, 31 First test piece 12, 22, 32 Second test piece 11a, 12a, 21a, 22a, 31a, 32a One side 11b, 12b, 21b, 22b, 31b, 32b Other side 33, 34 Spacers A11a, A11b, A12a, A12b Cross-sectional areas A21a, A21b, A22a, A22b Cross-sectional areas B11a, B11b, B12a, B12b Plate widths B21a, B21b, B22a, B22b Plate width C Coupling means Ca, Cb Chuck E Adjacent range F Test loads F1a, F1b, F2a, F2b Tensile forces J10, J20, J30 Joints J11, J21, J31 First joints J12, J22, J32 Second joints K1a, K1b, K2a, K2b Tensile rigidity P One end Q Other end R Peel force t11a, t11b, t21a, t21b, t22a, t22b Plate thickness τ Shear force

Claims (17)

A strength test method for evaluating the strength of a joint,
A rod-shaped first test piece;
A rod-shaped second test piece overlapping the first test piece;
A preparation step of preparing a strength test piece including a joint for joining the first test piece and the second test piece;
One end of the first test piece and the second test piece in the longitudinal direction is held by one chuck of a tensile tester, and the other end of the first test piece and the second test piece in the longitudinal direction is pulled. A gripping step of gripping with the other chuck of the testing machine;
A pulling step of pulling the first test piece and the second test piece in the longitudinal direction,
In the tensile step, the resultant force of the tensile force that pulls the first test piece to one side and the tensile force that pulls the first test piece to the other side is the tensile force that pulls the second test piece to one side and the second test piece. A strength test method characterized in that it is different from the resultant force of the tensile force that pulls the strip to the other. 2. The strength testing method according to claim 1, wherein the joint is a weld. 3. The strength testing method according to claim 2, wherein the welded portion is a spot welded portion. The cross-sectional area of the first test piece and the second test piece in the adjacent range from the joint to the same distance on both sides in the longitudinal direction, in the plane perpendicular to the longitudinal direction, is the same as the first test 4. The strength testing method according to any one of claims 1 to 3, wherein the cross-sectional areas of the piece and the second test piece in a plane perpendicular to the longitudinal direction are smaller than each other. 5. The method according to any one of claims 1 to 4, wherein in the pulling step, a peeling force for peeling the first test piece and the second test piece is applied to the first test piece and the second test piece. The strength test method according to any one of the items. 6. A spacer is sandwiched between the first test piece and the second test piece at a position different from the joint portion in the preparation step. The strength test method described in . The cross-sectional area in a plane perpendicular to the longitudinal direction at an intermediate position from one end of the first test piece to the joint is 7. The strength test method according to any one of claims 1 to 6, wherein the cross-sectional area is smaller than the cross-sectional area in a plane perpendicular to the direction. The cross-sectional area in a plane perpendicular to the longitudinal direction at an intermediate position from one end of the second test piece to the joint is 8. A strength test method according to any one of claims 1 to 7, wherein the cross-sectional area is greater than the cross-sectional area in a plane perpendicular to the direction. The strength testing method according to any one of claims 1 to 8, wherein the tensile strength of the first test piece and the tensile strength of the second test piece are different. A strength test piece for evaluating the strength of a joint,
A rod-shaped first test piece;
A rod-shaped second test piece overlapping the first test piece;
A joint portion that joins the first test piece and the second test piece,
The first test piece and the second test piece have one end in the longitudinal direction gripped by one chuck of the tensile tester, and the other end in the longitudinal direction gripped by the other chuck of the tensile tester has a part
The resultant force of the tensile force that pulls the first test piece to one side and the tensile force that pulls the first test piece to the other side is the tensile force that pulls the second test piece to one side and the tensile force that pulls the second test piece to the other side. A strength test piece characterized in that it is different from the resultant force with the tensile force. 11. The strength test piece of claim 10, wherein the joint is a weld. 12. The strength test strip of claim 11, wherein the welds are spot welds. The cross-sectional area of the first test piece and the second test piece in the adjacent range from the joint to the same distance on both sides in the longitudinal direction, in the plane perpendicular to the longitudinal direction, is the same as the first test 13. The strength test piece according to any one of claims 10 to 12, wherein the cross-sectional areas of the piece and the second test piece in a plane perpendicular to the longitudinal direction are smaller than each other. 14. The strength test piece according to any one of claims 10 to 13, wherein a spacer is provided between the first test piece and the second test piece at a position different from the joint. The strength test piece described in the section. The cross-sectional area in a plane perpendicular to the longitudinal direction at an intermediate position from one end of the first test piece to the joint is 15. A strength test piece according to any one of claims 10 to 14, characterized in that it has a smaller cross-sectional area in a plane perpendicular to the direction. The cross-sectional area in a plane perpendicular to the longitudinal direction at an intermediate position from one end of the second test piece to the joint is 16. A strength test piece according to any one of claims 10 to 15, characterized in that the cross-sectional area is greater than the cross-sectional area in the plane perpendicular to the direction. The strength test piece according to any one of claims 10 to 16, wherein the tensile strength of the first test piece and the tensile strength of the second test piece are different.

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