JP2016020879A - Material testing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material testing machine capable of accurately detecting a bending test force by keeping constant a contact force of a probe tip end to a specimen during testing at a deflection measurement of the specimen by a contact type displacement meter.SOLUTION: A probe support mechanism includes: a first pulley 51 disposed on a rotation shaft 53 in a state where a wire 56, one end of which is connected to a support shaft part 48 of a probe 41, is wound therearound; a second pulley 52 that is disposed on the same rotation shaft 53 as the first pulley 51 and has a diameter smaller than that of the first pulley 51; and a weight 55 that is connected to one end of a wire 57 wound around the second pulley 52. The rotation shaft 53 is rotatably disposed on a strut 54 vertically provided on a support base 24. Gravity applied to the weight 55 is a force with which the probe 41 abuts on a specimen 10 through the first pulley 51 and the second pulley 52. The force is constant, regardless of a position of the probe 41 in a vertical direction, which can be easily subtracted from a measured test force.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a material testing machine that performs a bending test by applying a test force to a test piece supported by a pair of fulcrums.

  In a material testing machine that performs such a bending test, a load is applied to the test piece by pushing a punch into the test piece that is supported by a pair of fulcrums. In general, the fulcrum supporting the test piece is fixed to the table, and the punch is disposed on the cross head that moves up and down with respect to the table by driving a load mechanism. And it is the structure which gives a load to a test piece by raising / lowering a crosshead in the state which has arrange | positioned the test piece on the table via the fulcrum (for example, refer patent document 1).

  In such a material testing machine, the test force applied to the test piece is detected by a load cell interposed between the crosshead and the punch. In addition, for measuring the deflection generated in the test piece when the punch is pushed into the test piece, for example, a contact type displacement meter that detects the displacement by bringing the tip of the probe (probe) into contact with the center of the test piece is used. It is used. FIG. 5 is a schematic view for explaining deflection measurement by a conventional contact displacement meter 140.

  Conventionally, the contact-type displacement meter 140 includes a probe 141 that abuts the tip of the test piece 10 on the opposite side of the surface opposite to the contact surface of the punch 21, and receives the pressing force of the punch 21. By detecting the displacement of the probe 141 accompanying the deformation of the piece 10, the deflection of the test piece 10 can be measured.

JP 2012-251901 A

  As shown in FIG. 5, the probe 141 is provided with a spring 149 that elastically biases the tip of the probe 141 against the test piece 10. The spring 149 stores repulsive energy when the pressing force by the punch 21 is applied to the test piece 10 and is compressed. That is, the reaction force against the pressing force is changed to increase in the test. In order to accurately obtain the bending test force, it is necessary to subtract the reaction force by the spring 149 from the detected value of the load cell 14, and this reaction force changes with the displacement of the test piece 10 during the test. For this reason, it is necessary to calculate the reaction force by the spring 149 included in the detection value of the load cell 14 in accordance with the deflection of the central portion of the test piece 10 and subtract it from the detection value of the load cell 14.

  This invention has been made to solve the above problems, and when measuring the deflection of the test piece with a contact displacement meter, the contact force to the test piece at the tip of the probe under test is made constant, An object is to provide a material testing machine capable of accurately detecting a bending test force.

  The invention described in claim 1 is a material testing machine that performs a bending test by applying a test force to a test piece supported by a pair of fulcrums, and is disposed on a cross head that is moved up and down by a load mechanism. A punch, a load detector for detecting a test force applied to the test piece, and a telescopic arrangement in the direction of the load axis, and opposed to the punch and the test piece. The probe has a probe whose tip is in contact with the surface opposite to the surface with which the punch abuts, a displacement meter for measuring the deflection of the test piece, and a weight for the tip of the probe in the displacement meter. And a probe support mechanism for contacting the test piece with a predetermined force.

  The invention according to claim 2 is the invention according to claim 1, wherein the probe support mechanism includes a first pulley on which a wire connected to a support shaft portion of the probe is wound, and the first pulley. A second pulley having a diameter different from that of the first pulley, and a weight connected to a wire wound around the second pulley;

  The invention according to claim 3 is the invention according to claim 1 or 2, wherein the weight is detachably disposed.

  According to the first to third aspects of the present invention, since the tip of the probe abuts on the test piece with a predetermined force using a weight, a contact displacement meter having a spring on a conventional probe is used. Unlike the case of measuring the deflection, it is not necessary to consider the error due to the reaction force of the spring that fluctuates during the test in the detection value of the load detector, and it becomes possible to detect a more accurate test force.

  According to the second aspect of the present invention, the probe support mechanism has the first pulley and the second pulley having different diameters with the same rotation axis, and therefore the force when the tip of the probe comes into contact with the test piece. (Contact force) can be adjusted by a lever ratio which is a ratio of a radius of the first pulley and the second pulley.

  According to the invention of claim 3, by making the weight detachable, the force (contact force) when the tip of the probe contacts the test piece can be easily changed by changing the weight of the weight. Can be adjusted.

1 is a schematic diagram of a material testing machine according to the present invention. 3 is a schematic side sectional view of a displacement meter 40. FIG. It is a schematic diagram explaining the positional relationship of the punch 21 and the probe 41 when starting a test. It is a schematic diagram for demonstrating a probe support mechanism. It is a schematic diagram explaining the deflection measurement by the conventional contact-type displacement meter 140. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a material testing machine according to the present invention.

  This material testing machine includes a table 16, a pair of support posts 19 erected on the floor, and a pair of screw rods erected so as to be able to rotate vertically on the table 16 inside each support column 19. 11, a crosshead 13 movable along the screw rods 11, and a load mechanism 30 for moving the crosshead 13 to apply a test force to the test piece 10. FIG. 1 shows a state in which the left column 19 of the pair of columns 19 is removed.

  The cross head 13 is connected to the pair of screw rods 11 via nuts (not shown). The lower end portion of each screw rod 11 is connected to the load mechanism 30, and power from a motor as a power source (not shown) in the load mechanism 30 is transmitted to the pair of screw rods 11. . As the pair of screw rods 11 rotate in synchronization, the cross head 13 moves up and down along the pair of screw rods 11.

  The crosshead 13 is provided with a load cell 14 that is a load detector for detecting a test force applied to the test piece 10 and a punch 21 that contacts the surface of the test piece 10. On the other hand, a support base 24 on which a displacement meter 40 described later is disposed is fixed to the table 16. A pair of fulcrum 22 is disposed on the support base 24 so that the distance between the fulcrums 22 (distance between fulcrums) can be changed, and the pair of fulcrums 22 supports the test piece 10 from the back surface. When performing a bending test, a test force (bending load) is applied to the test piece 10 by lowering the crosshead 13 while the test piece 10 is supported by the pair of fulcrums 22. At this time, the test force acting on the test piece 10 is detected by the load cell 14 and input to the control unit 23. Further, the deflection of the test piece 10 is measured by the displacement meter 40.

  The control unit 23 is configured by a computer including a CPU and a sequencer. As shown in FIG. 1, a display unit 25 having a touch panel, a load cell 14, and a load mechanism 30 are connected to the control unit 23. And the control part 23 takes in the test force data from the load cell 14, and the data from the displacement meter 40, and performs a data process. The test force (bending load) with respect to the test piece 10 and the deflection in the test piece 10 are obtained by such processing such as calculation in the control unit 23.

  FIG. 2 is a schematic side sectional view for explaining the displacement detector 45 of the displacement meter 40.

  The displacement meter 40 is attached to a test jig for a bending test and measures the deflection of the central portion of the test piece 10 by a contact method. As shown in FIG. 2, the displacement meter 40 includes a probe 41 that penetrates the upper surface of the housing 42 and can be expanded and contracted in the load axis direction, and a displacement detector 45 provided in the housing 42. The The probe 41 includes a distal end portion 47 and a support shaft portion 48. The displacement detector 45 detects the displacement of the probe 41 by a linear scale including a scale 44 fixed to the housing 42 and a detection head 43 connected to the lower end of the support shaft 48 of the probe 41. In addition, as a displacement detection means of the probe 41 which comprises the displacement detection part 45, you may employ | adopt other systems, such as a differential transformer type, for example.

  In the material testing machine shown in FIG. 1, the displacement meter 40 is mounted on the support 24, but the height of the support 24 is increased and the displacement detector 45 of the displacement meter 40 is placed in the support 24. It may be arranged. In this case, the support base 24 also serves as the casing 42 of the displacement meter 40 described above.

  FIG. 3 is a schematic diagram for explaining the positional relationship between the punch 21 and the probe 41 when the test is started.

  When starting a three-point bending test in which the punch 21 is pressed against the test piece 10 supported by the pair of fulcrums 22 with a predetermined test force, the cross head 13 is lowered to move the punch 21 to the position indicated by the phantom line in FIG. And brought into contact with the test piece 10. On the other hand, the probe 41 is moved to a height indicated by an imaginary line in FIG. 3, and the tip portion 47 of the probe 41 is brought into contact with the test piece 10 at a position opposite to the contact position of the punch 21. Thereafter, a bending test is performed in which the cross head 13 is lowered and the punch 21 is pushed into the test piece 10.

  Next, a probe support mechanism that is a characteristic part of the present invention will be described. FIG. 4 is a schematic diagram for explaining the probe support mechanism. FIG. 4 shows a state in which the vicinity of the displacement meter 40 of FIG. 1 is viewed from the side.

  The probe support mechanism includes a first pulley 51 disposed on the rotation shaft 53 in a state in which a wire 56 having one end connected to the support shaft portion 48 of the probe 41 is wound, and the same rotation shaft as the first pulley 51. 53, a second pulley 52 having a diameter smaller than that of the first pulley 51, and a weight 55 connected to one end of a wire 57 wound around the second pulley 52. The rotary shaft 53 is rotatably disposed on a support column 54 erected on the support base 24. Since the first pulley 51 and the second pulley 52 are fixed to the rotary shaft 53, the first pulley 51 and The second pulley 52 can rotate integrally with the support shaft 54 together with the rotation shaft 53.

  The wire 56 and the support shaft portion 48 of the probe 41 are connected to each other via a connecting member 58 fixed to a predetermined height position of the support shaft portion 48. The other end of the wire 56 not connected to the spindle 48 of the probe 41 is fixed at a predetermined position on the outer peripheral surface of the first pulley 51. That is, the probe 41 is suspended from the first pulley 51 by the wire 56. Further, the weight 55 and the wire 57 are connected via an S-shaped hook 59, and the weight 55 is detachable from the wire 57. The other end of the wire 57 not connected to the weight 55 is fixed at a predetermined position on the outer peripheral surface of the second pulley 52. That is, the weight 55 is suspended from the second pulley 52 by the wire 57.

  When starting the three-point bending test in which the punch 21 is pressed against the test piece 10 supported by the pair of fulcrums 22 with a predetermined test force, the cross head 13 is lowered to bring the punch 21 into contact with the test piece 10 and the probe The tip portion 47 of 41 is brought into contact with the test piece 10 at a position facing the contact position of the punch 21. At this time, the distal end portion 47 of the probe 41 abuts on the test piece 10 with a predetermined force utilizing the weight of the weight 55 transmitted via the first pulley 51 and the second pulley 52. Note that the height of the probe 41 is adjusted by attaching or detaching or fixing the weight 55. For example, when it is desired to place the probe 41 at a position that does not contact the test piece 10, the weight 55 may be removed from the wire 56, and the S-shaped hook 59 may be hooked at a predetermined position of the column 54. The weight 55 may be prevented from descending below, for example, by placing a table below.

  In this embodiment, the first pulley 51 and the second pulley 52 having different diameters are wheel shafts that move on the same axis. Then, the weight 55 is suspended from the second pulley 52 having a small diameter among the two pulleys, so that the support shaft is changed according to the lever ratio that is the ratio between the radius of the first pulley 51 and the radius of the second pulley 52. The distance and force for lifting the portion 48 upward is adjusted. For example, when the ratio of the radius of the first pulley 51 to the radius of the second pulley 52 is 2: 1, the force (contact force) when the tip portion 47 of the probe 41 contacts the test piece 10 is the weight of the weight 55. However, the distance by which the support shaft portion 48 is lifted upward is twice the amount of movement of the weight 55. In other words, the work of moving the probe 41 up and down can be performed efficiently, while the force acting on the test piece 10 by the weight 55 can be reduced.

  The magnitude of the force acting on the test piece 10 from the tip 47 of the probe 41 by the force that lifts the probe 41 upward is such that the weight 55 that can be attached to and detached from the wire 57 is different from the weight 55 that has a different weight. It is easily adjusted by changing to Further, the fact that the weight 55 is detachable is effective in that the force for lifting the probe 51 upward can be easily changed even when the diameters of the first pulley 51 and the second pulley 52 are the same.

  When the tip portion 47 of the probe 41 is brought into contact with the test piece 10 with a predetermined force adjusted by the ratio of the radius of the first pulley 51 and the radius of the second pulley 52 and the weight of the weight 55, Reset the test force detected by the load cell 14 to zero, and start the test.

  When the test is started, the test piece 10 is pressed by the punch 21. Then, as the central portion of the test piece 10 to which the bending test force is applied bends downward, the probe 41 whose tip 47 is in contact with the back surface of the test piece 10 moves downward. At this time, the rotating shaft 53 rotates (rotates counterclockwise in FIG. 4) in conjunction with the movement of the probe 41. On the other hand, the force which acts on the test piece 10 from the front-end | tip part 47 of the probe 41 by the force which lifts the probe 41 upwards in the meantime is constant. A value detected by the detection head 43 and the scale 44 connected to the lower end of the spindle portion 48 of the probe 41 is transmitted to the control unit 23, and the displacement of the probe 41 is calculated as a deflection amount.

  In this embodiment, the force acting on the test piece 10 from the distal end portion 47 of the probe 41 by the force that lifts the probe 41 upward using the weight 55 is a constant force after the test is started. Act on. This force can be handled as a value that does not need to be considered by resetting the detection value of the load cell 14 at the start of the test to zero. In the conventional displacement meter 140 shown in FIG. 5, the variation in the reaction force during the test that the reaction force of the spring 149 increases as the punch 21 is pushed impairs the accuracy of the detected value of the test force by the load cell 14. However, in the material testing machine of the present invention, the provision of the above-described probe support mechanism makes it possible to detect a test force that is not affected by fluctuations in reaction force during the test. That is, a more accurate test force detection value can be obtained.

  In this embodiment, the weights of the wire 56 and the wire 57 are negligibly small compared to the weights of the probe 41 and the weight 55. Therefore, the load fluctuation caused by the wire itself that varies with the rotation of the first pulley 51 and the second pulley 52 can be ignored.

  In the material testing machine according to the present invention, since the test force can be accurately detected by the conventional displacement meter 140, it is possible to calculate a more accurate bending strength. Furthermore, the bending elastic modulus calculated using the load-deflection curve obtained in the bending test by this material testing machine can be calculated as a more accurate value. For this reason, it becomes possible to evaluate the bending characteristic of material more correctly.

  Further, in the material testing machine including the conventional contact displacement meter 140 shown in FIG. 5, the test piece 10 is supported by the pair of fulcrums 22 while being slightly pushed by the punch 21, and the punch 21. Is placed at the test position in a state where the probe 141 is pushed by the spring 149 from the opposite side. This is because it is difficult to perfectly align the tip position of the probe 141 and the tip position of the pair of fulcrums 22 so that the tip of the probe 141 is slightly closer to the test piece 10 than the pair of fulcrums 22. This is because the tip position of the probe 141 is adjusted. For this reason, conventionally, when the test piece 10 is supported by the pair of fulcrums 22 in a state where the punch 21 is separated from the test piece 10, the support of the test piece 10 becomes unstable (the test piece 10 is moved by the probe 141. The problem of rising) also occurred.

  In the material testing machine of this invention, since the weight 55 is detachable from the wire 57, the weight 55 is removed from the wire 57 when the test piece 10 is supported by the pair of fulcrums 22. The probe 41 can be placed at a position where it does not contact the test piece 10. Thus, when the test piece 10 is supported by the pair of fulcrums 22 in a state where the punch 21 is separated from the test piece 10, a position where the probe 41 does not become an obstacle to the arrangement of the test piece 10 can be arranged. The piece 10 is not lifted by the contact of the probe 41, and the position of the test piece 10 can be prevented from being shifted.

  In the above-described embodiment, the probe support mechanism having the first pulley 51 and the second pulley 52 having different diameters has been described as an example. However, the weight of the weight 55 is set upward via the single pulley. You may comprise the probe support mechanism used as the force moved to. In other words, the predetermined force using the weight in the probe support mechanism of the present invention is to make the downward force according to the gravity of the weight 55 an upward predetermined force by a fixed pulley or other elements in addition to the wheel shaft. It is included and is not limited to the embodiment.

DESCRIPTION OF SYMBOLS 10 Test piece 11 Screw head 13 Cross head 14 Load cell 16 Table 19 Support column 21 Punch 22 Support point 23 Control part 24 Support stand 25 Display part 30 Load mechanism 40 Displacement meter 41 Probe 42 Housing | casing 43 Detection head 44 Scale 45 Displacement detection part 47 Tip Portion 48 Support shaft 51 First pulley 52 Second pulley 53 Rotating shaft 54 Post 55 Weight 56 Wire 57 Wire 59 S-shaped hook

Claims (3)

In a material testing machine that performs a bending test by applying a test force to a test piece supported by a pair of fulcrums,
A punch disposed on the crosshead that is raised and lowered by the load mechanism;
A load detector disposed on the crosshead for detecting a test force applied to the test piece;
The probe has a probe that expands and contracts in the direction of the load axis, is opposed to the punch and the test piece, and has a probe whose tip is in contact with the surface opposite to the surface with which the punch abuts. A displacement meter to be measured;
A probe support mechanism for bringing the tip of the probe in the displacement meter into contact with a test piece with a predetermined force using a weight;
A material testing machine characterized by comprising: The material testing machine according to claim 1,
The probe support mechanism is
A first pulley on which a wire connected to the spindle portion of the probe is wound;
A second pulley disposed on the same axis as the first pulley and having a diameter different from that of the first pulley;
A weight connected to a wire wound around the second pulley;
Having a material testing machine. The material testing machine according to claim 1 or 2,
The weight is a material testing machine that is detachably disposed.

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