JP2016205824A - Materials testing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically position a wedge type gripper, taking into account any shifting of the direction of load on its gripping teeth when a test piece is held with the gripper.SOLUTION: A memory unit stores in advance the distance X between an upper crosshead 24 and a lower crosshead 26, which takes into account the vertical travel distances in a vertical direction along the load axis lines M of the holding teeth 41 owing to difference in sectional size of a test piece 10 in the separating direction of the holding teeth 41 for the length L of a test piece 10 for each type of holding tooth 41. Inputting of the length L and the diameter d (or the thickness t) of the test piece 10 by an operator makes possible ready acquisition of the distance X between the upper crosshead 24 and the lower crosshead 26.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a material testing machine that applies a load to a test piece held at both ends by a gripping tool.

  Such a material testing machine has loading means for applying a test load to the test piece by separating and contacting the opposing members each provided with grips for holding both ends of the test piece. And the automatic material testing machine which adjusts the distance between grips based on the length of a test piece is proposed (refer patent document 1).

  In addition, such a material testing machine includes a table, an upper cross head connected to the table via a column, a ram cylinder that moves the table and the upper cross head synchronously, and an elevator along the column. A structure comprising a possible lower crosshead, a pair of screw rods for raising and lowering the lower crosshead, and a force detection sensor for detecting a test force applied between the table or the upper crosshead and the lower crosshead Are known.

  When performing a tensile test in this material testing machine, the upper end of the ram cylinder is gripped by the upper gripping tool disposed on the upper crosshead and the lower gripping tool disposed on the lower crosshead. Since the upper crosshead is raised relative to the lower crosshead by driving, it is necessary to change the distance between the upper crosshead and the lower crosshead in accordance with the size of the test piece. That is, when performing a tensile test, it is necessary to raise and lower the lower crosshead so that the distance between the upper crosshead and the lower crosshead corresponds to the length of the test piece for the tensile test. For this reason, an automatic material testing machine has been proposed that adjusts the distance between the grips respectively disposed on the upper crosshead and the lower crosshead based on the length of the test piece (see Patent Document 2).

  In addition, a material test in which a wedge-type gripping tool that clamps and grips a test piece with a pair of gripping teeth by moving a pair of gripping teeth along an inclination is provided on the upper crosshead and the lower crosshead. In the machine (see Patent Document 3), when placing the test piece between the upper crosshead and the lower crosshead, first, the upper end of the test piece is gripped by the grip on the upper crosshead side. Thereafter, the lower crosshead is raised to a height corresponding to the length of the test piece, and the lower end of the test piece is held by the grip on the lower crosshead side.

JP 2002-365188 A JP-A-5-273101 JP 2003-232710 A

  When both ends of the test piece are gripped by a wedge-type gripping tool having a pair of gripping teeth as described in Patent Document 3, the cross-sectional size of the test piece in the direction in which the gripping teeth are perpendicular to the load axis Due to the difference, the position of the gripping tooth specimen in the load axis direction varies. For this reason, even if the lower crosshead is moved so that the distance between the upper crosshead and the lower crosshead is the optimal distance based on the length of the test piece, The gripping position may be different between the top and bottom of the specimen. If the grip amount and grip position are different between the top and bottom of the test piece in this way, an unintended compressive load is applied to the end of the test piece that is gripped by the gripping teeth, or a mark attached to the test piece. On the other hand, the test load is applied to the test piece in a state where the upper and lower grip positions are uneven, and the reliability of the test result is lowered. Therefore, in order for the gripping tooth to sandwich the test piece using the entire surface of the gripping tooth in the load axis direction and to make the gripping position of the test piece equal to the top and bottom of the test piece, the lower crosshead It is necessary to adjust the position. However, the position adjustment of the lower crosshead is complicated and takes time.

  The present invention has been made to solve the above-mentioned problems, and the gripping tool is automatically positioned in consideration of the movement of the gripping tooth in the load axis direction when the test piece is gripped by the wedge-type gripping tool. An object of the present invention is to provide a material testing machine capable of performing the above.

  The invention according to claim 1 is a wedge-type gripping tool having a pair of gripping teeth that come into contact with each other in a direction perpendicular to the load axis by slidingly contacting a pair of wedge surfaces formed symmetrically with respect to the load axis. And a load mechanism that applies a test load to a test piece gripped at both ends of the gripper by separating and supporting the opposing support members each having the gripper disposed along a load axis. In the material testing machine, when measuring the distance between the gripping tools, the cross-sectional size of the test piece in the direction of separation of the gripping teeth, and gripping the test piece by bringing the gripping teeth close to each other Storage means for storing the relationship between the movement amount of the jaw teeth in the load axis direction, the movement amount of the jaw teeth corresponding to the cross-sectional size stored in the storage means, and the test A movement adjusting means for adjusting the movement of the support member so that the measured value of the measuring means matches the optimum distance between the grips at the start of the test derived based on the length of It is characterized by.

  The invention according to claim 2 is a photoelectric sensor according to claim 1, wherein the measuring means is a photoelectric sensor that is disposed on one of the support members and measures a distance between the support members. .

  According to a third aspect of the present invention, in the material testing machine according to the first aspect, the measuring means is a means for calculating a distance between the support members from a driving amount of the gripping tool.

  According to the first to third aspects of the invention, the cross-sectional size of the test piece in the direction of separation of the gripping tooth and the load axis direction of the gripping tooth when the gripping tooth is held close to each other to grip the test piece The relationship between the amount of movement is stored in the storage means in advance, and based on the amount of movement of the gripping tooth corresponding to the cross-sectional size stored in the storage means and the length of the test piece, between the gripping tools at the start of the test. Since the optimum distance is derived and the movement of the support member on which the grip is placed is adjusted so that the measured value of the distance between the grips by the measuring means becomes the optimum distance, the test piece is measured with a wedge-type grip. The gripper can be positioned automatically in consideration of the movement of the gripping tooth in the load axis direction when gripping the handle. As a result, the amount and position of gripping by the gripping teeth at both ends of the test piece can be made equal, and the reliability of the test result can be improved.

  According to the invention described in claim 3, since the measuring means is means for calculating the distance between the support members from the driving amount of the gripping tool, a sensor for measuring the distance between the gripping tools is provided. The distance between grips can be measured.

1 is a schematic diagram of a material testing machine according to the present invention. It is AA sectional drawing of FIG. It is a block diagram which shows the main control systems of the material testing machine which concerns on this invention. It is explanatory drawing of the chuck structure in the upper holding tool 31 and the lower holding tool 32. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a material testing machine according to the present invention, and FIG. 2 is a cross-sectional view taken along line AA of FIG. FIG. 3 is a block diagram showing a main control system.

  This material testing machine includes a table 21, an upper cross head 24 connected to the table 21 via a pair of support columns 22, a ram cylinder 25 that moves the table 21 and the upper cross head 24 up and down synchronously, and a pair And a pair of screw rods 23 screwed to nuts (not shown) provided at both ends of the lower cross head 26. The lower cross head 26 is configured to be lifted and lowered by a rotation drive mechanism 27 (see FIG. 3) that rotates a nut by an electric motor or a hydraulic motor (not shown). The operation of the rotation drive mechanism 27 is controlled by the control unit 35. The pair of screw rods 23 are erected on the base through the table 21.

  An upper grip 31 is disposed on the upper cross head 24, and a lower grip 32 is disposed on the lower cross head 26. When performing the tensile test, both ends of the test piece 10 are held by the upper grip 31 and the lower grip 32 in order to place the test piece 10 in the test space between the upper cross head 24 and the lower cross head 26. The gripping operation of the test piece 10 by the upper gripper 31 and the lower gripper 32 is driven and controlled by a chuck drive mechanism 29 (see FIG. 3) that supplies hydraulic pressure or pneumatic pressure to a fluid pressure cylinder 49 described later. The chuck drive mechanism 29 is controlled by the control unit 35.

  When the test piece 10 is disposed between the upper crosshead 24 and the lower crosshead 26 on the lower surface facing the test space of the upper crosshead 24, the distance between the upper crosshead 24 and the lower crosshead 26 is set. A distance sensor 39 for measurement is provided. The distance sensor 39 is a photoelectric sensor having a light projecting unit and a light receiving unit. The light receiving unit receives the laser light emitted from the light projecting unit and reflected from the upper end surface of the lower cross head 26, whereby the upper cross The distance between the head 24 and the lower cross head 26 is measured. The measured value of the distance sensor 39 is transmitted to the control unit 35 and displayed on the display unit 36 as necessary. In this material testing machine, the distance sensor 39 is disposed on the upper cross head 24, but may be disposed on the lower cross head 26.

  In addition, the distance between the upper cross head 24 and the lower cross head 26 is not only measured by the distance sensor 39, but may be other methods that can be measured with a desired accuracy. For example, the distance between the upper cross head 24 and the lower cross head 26 may be measured using a linear scale or the like.

  Further, the lower crosshead 26 is driven up and down by the rotation drive mechanism 27. If a sensor for detecting the initial position is provided so that the absolute position of the lower crosshead 26 can be stored, the rotation drive mechanism The amount of movement of the lower crosshead 26 can be calculated from the drive amount of 27, and the distance between the lower crosshead 26 and the upper crosshead 24 can be calculated, and the calculated value is measured by the distance sensor 39 described above. It may be used instead of. That is, the measuring means for measuring the distance between the gripping tools in this specification is a concept including all of them. As described above, the measuring means of the present invention may directly measure the distance between the lower cross head 26 and the upper cross head 24 (the distance between the gripping tools) like the distance sensor 39. Thus, the distance between the lower cross head 26 and the upper cross head 24 (distance between the grippers) may be measured indirectly. When measuring the distance between the grippers by calculation, it is not necessary to separately provide the distance sensor 39 in the lower cross head 26 or the upper cross head 24. Even in difficult circumstances, it is possible to easily obtain the distance between the grippers.

  The ram cylinder 25 has a configuration in which the ram 25b extends by supplying pressure oil to the cylinder chamber 25a. As the ram 25b extends, the table 21, the pair of struts 22, and the upper cross head 24 rise together in an integrated manner. As the table 21 and the upper cross head 24 rise, the upper cross head 24 and the lower cross head 26 are separated from each other, and the tensile load is applied to the test piece 10 held at both ends by the upper grip 31 and the lower grip 32. Is granted. The operation of the ram cylinder 25 is driven and controlled by a hydraulic source 38 that supplies pressure oil to the ram cylinder 25. The hydraulic power source 38 is controlled by the control unit 35.

  The test force at this time is measured by the pressure sensor 33. This measured value is transmitted to the control unit 35 and displayed on the display unit 36 as necessary. Further, the movement amount of the table 21 and the upper cross head 24 at this time is detected by the stroke detector 34. This detected value is transmitted to the control unit 35 and displayed on the display unit 36 as necessary.

  The control unit 35 includes a computer and peripheral devices, and includes a calculation unit 51, a movement adjustment unit 52, and a storage unit 53 as functional configurations. The calculation unit 51 calculates the displacement amount of the test piece 10 and the control amount of the apparatus based on the inputs from the pressure sensor 33 and the stroke detector 34 during the test. The storage unit 53 stores in advance a relationship between a cross-sectional size of a gripping tooth 41 to be described later in the test piece 10 and a moving amount of the gripping tooth 41 in the load axis M direction. The movement adjustment unit 52 is configured such that the measured value of the distance sensor 39 of the test piece 10 has the cross-sectional size of the gripping tooth 41 in the test piece 10 stored in the storage unit 53 and the load tooth M in the load axis M direction. Positioning is performed by adjusting the movement of the lower crosshead 26 before starting the test so that the optimum distance between the grips derived from the relationship with the amount of movement is obtained.

  FIG. 4 is an explanatory diagram of the chuck structure in the upper grip 31 and the lower grip 32.

  In the upper cross head 24 and the lower cross head 26, a space opened toward a test space in which the test piece 10 is disposed is provided, and an upper grip 31 and a lower grip 32 are disposed in the space. ing. Each of the upper gripper 31 and the lower gripper 32 is disposed in a state where the gripping surfaces for gripping the test piece 10 are opposed to each other, and are separated from each other in a direction perpendicular to the load axis M (left-right direction in FIG. 4). It has a gripping tooth 41 and a pair of gripping tooth holders 42 for holding each gripping tooth 41. The gripping tooth holder 42 is slidably contacted with the wedge surface 44 symmetrically with respect to the load axis M formed in the space in the upper crosshead 24 and the lower crosshead 26 on the surface opposite to the holding surface of the gripping teeth 41. An inclined surface 45 is provided. The end of the gripping tooth holder 42 opposite to the opening facing the test space of the upper cross head 24 and the lower cross head 26 is in contact with the holder pressing member 43.

  The holder pushing member 43 is connected to the fluid pressure cylinder 49. The fluid pressure cylinder 49 is supplied with hydraulic pressure or pneumatic pressure by the action of the chuck drive mechanism 29 (see FIG. 3), and moves the holder pressing member 43. The gripping tooth holder 42 is moved along the wedge surface 44 by operating the fluid pressure cylinder 49 against the holder pressing member 43 to apply a pressing force. As a result, the distance between the pair of gripping teeth 41 is close, and a gripping force is applied to the test piece 10. Such a chuck structure of the upper gripper 31 and the lower gripper 32 is called a wedge type. Note that the gripping teeth 41 can be attached to and detached from the gripping tooth holder 42 and can be replaced according to the type of the test piece 10.

  A procedure for attaching the test piece 10 when performing a tensile test in the material testing machine having the above-described configuration will be described.

  When performing a tensile test using a material testing machine, the distance between the upper gripping tool 31 and the lower gripping tool 32 needs to be set to a size corresponding to the size of the test piece 10 on which the tensile test is performed. In this material testing machine, the upper gripper 31 and the lower gripper 32 are built in the upper crosshead 24 and the lower crosshead 26, which are support members for supporting them, respectively. From the distance X to the lower crosshead 26, the optimum distance between the upper gripper 31 and the lower gripper 32 is also uniquely determined. In order to properly perform the tensile test, it is desirable that the grip amount and the grip position at both ends of the test piece 10 by the grip teeth 41 in the upper grip 31 and the lower grip 32 are equal. For this reason, in the storage unit 53 of the control unit 35 of this material testing machine, the test piece in the separation direction of the gripping teeth 41 is previously set to the length L (mm) of the test piece 10 for each type of the gripping teeth 41. The distance between the upper crosshead 24 and the lower crosshead 26 corresponding to the optimum distance between the grippers of the present invention in consideration of the amount of vertical movement of the gripping teeth 41 along the load axis M due to the difference in the cross-sectional size of 10 X is stored.

  The operator inputs the length L (mm) of the test piece 10 and the cross-sectional size of the test piece 10 to the control unit 35 via the operation unit 37. The cross-sectional size of the test piece 10 is the diameter d (mm) of the test piece 10 when the shape of the test piece 10 is a round bar, and the thickness t of the test piece 10 when the shape of the test piece 10 is a flat plate. (Mm). Thereby, the distance X between the upper cross head 24 and the lower cross head 26 corresponding to the length L and the diameter d or the thickness t of the test piece 10 is called from the storage unit 53 of the control unit 35.

  Before starting the test, the ram 25b of the ram cylinder 25 is lowered to the lowest end. When the test piece 10 is arranged in the test space, the fluid on the upper gripper 31 side in a state where the upper cross head 24 and the lower cross head 26 are spaced apart by a distance larger than the length L of the test piece 10. The pressure cylinder 49 is operated so that the upper end of the test piece 10 is sandwiched between the pair of gripping teeth 41 and the upper gripping tool 31 grips the test piece 10. Then, the operator operates the lift switch of the lower cross head 26 in the operation unit 37 to raise the lower cross head 26 connected to the screw rod 23. At this time, the distance between the upper crosshead 24 and the lower crosshead 26 is detected by a distance sensor 39 provided in the upper crosshead 24. If the distance measurement value detected by the distance sensor 39 is the distance X between the upper crosshead 24 and the lower crosshead 26 that has been called, the control unit 35 controls the lower crosshead 26. The rotation driving mechanism 27 of the provided nut is stopped, and the movement of the lower cross head 26 is stopped. Thereafter, the fluid pressure cylinder 49 on the lower gripper 32 side is operated to apply a pressing force to the holder pressing member 43 of the lower gripper 32 to move the pair of gripping tooth holders 42 upward. The pair of gripping teeth 41 sandwich the lower end of the test piece 10 so that the lower gripping tool 32 holds the test piece 10. As a result, the gripping of both ends of the test piece 10 by the upper gripping tool 31 and the lower gripping tool 32 is completed, and the test strip 10 is arranged in the test space.

  The distance X between the upper cross head 24 and the lower cross head 26 corresponding to the optimum distance between the grippers in the present invention will be described in more detail.

  The distance X between the upper crosshead 24 and the lower crosshead 26 is not only the length L of the test piece 10 but also a pair of gripping teeth 41 close to each other along the wedge surface 44 in order to grip the test piece 10. The amount of movement in the direction of the load axis M when moving in the direction is taken into consideration. As the diameter d (or thickness t) of the test piece 10 changes, the distance a (mm) between the end of the gripping teeth 41 and the end face of the lower crosshead 26 also changes. The cross-sectional size of the test piece 10 in the separation direction and the amount of movement of the gripping teeth 41 in the load axis M direction when the gripping teeth 41 are brought close to each other to grip the test piece 10 are, for example, the end of the gripping teeth 41 This can be understood as a change in the distance a from the end surface of the lower crosshead 26.

  Therefore, in this material testing machine, the relationship between the diameter d (or thickness t) of the test piece 10 and the distance a between the end portion of the gripping teeth 41 and the end surface of the lower crosshead 26 for each type of the gripping teeth 41. Is experimentally determined in advance and stored in the storage unit 53. Since the inclination angle of the wedge surface 44 with which the gripping tooth holder 42 is in sliding contact is a known value in design, the jaw teeth obtained from the inclination angle of the wedge surface 44 and the diameter d (or thickness t) of the test piece 10. The distance a can be calculated from the amount of movement of 41 in the direction of separation. Therefore, the relationship between the diameter d (or thickness t) of the test piece 10 and the distance a may be obtained by simulation.

  The length of the gripping teeth 41 in the load axis M direction is a length determined for each type, and the size of the gripping teeth 41 attached to and detached from the gripping tooth holder 42 is stored in the storage unit 53 for each type. Yes. The length L and the diameter d (or thickness t) of the test piece 10 are given by an operator input, and the distance a is obtained from the diameter d (or thickness t) of the test piece 10. In order to properly perform the tensile test, it is preferable that both ends of the test piece 10 are gripped by using the entire surface of the upper grip 31 and the lower grip 32 in the load axis M direction of the grip teeth 41. Therefore, for example, when the tip of the test piece 10 is protruded from the gripping teeth 41 by b (mm), if the gripping teeth 41 of the upper gripping tool 31 and the lower gripping tool 32 are held with a narrow pressure, the upper crosshead The distance X between 24 and the lower crosshead 26 is the amount of protrusion b × 2 from the gripping teeth 41 at both ends of the test piece 10, the length of the gripping teeth 41 in the load axis M direction, and the distance a × 2. Is subtracted from the length L of the test piece 10. Therefore, the relationship between the diameter d (or thickness t) of the test piece 10 in the direction of separation of the gripping teeth 41 and the amount of movement of the gripping teeth 41 in the load axis M direction is expressed by the relationship between the upper crosshead 24 and the lower crosshead 26. It can be stored in the storage unit 53 as a function for obtaining the distance X between them.

  Thereby, in this material testing machine, when the operator inputs the length L and diameter d (or thickness t) of the test piece 10 via the operation unit 37, the gripping teeth 41 grip the test piece 10. The optimum distance X between the upper cross head 24 and the lower cross head 26 in consideration of the amount of movement of the gripping teeth 41 in the load axis M direction can be easily obtained.

  In this material testing machine, as described above, the distance between the support members that support the grip at the start of the test (between the upper crosshead 24 and the lower crosshead 26) can be automatically set to the optimum distance. Since this optimum distance takes into account the amount of movement of the gripping teeth 41 in the load axis M direction when the test piece 10 is sandwiched between the gripping teeth 41, the amount of gripping by the gripping teeth 41 at the lower end of the test piece 10 Can be made equal, and the upper and lower gripping positions of the test piece 10 can be made equal. Thereby, the reliability of a test result can be improved.

  In the above-described embodiment, the ram cylinder 25 as a single-acting cylinder is used as the fluid pressure cylinder that moves the table 21 and the upper cross head 24 in synchronization, but other types such as an air cylinder and a hydraulic cylinder are used. A fluid pressure cylinder may be used.

  In the above-described embodiment, the lower cross head 26 is lifted and lowered by the nut having the rotation mechanism, but other lifting mechanisms such as rotating the screw rod 23 by the motor to raise and lower the lower cross head 26 are used. May be.

  Further, in the above-described embodiment, the case where the wedge-type grips are disposed in the upper cross head 24 and the lower cross head 26 has been described. However, the both ends of the test piece are gripped by the wedge-type grips. Therefore, the present invention can also be applied to a material testing machine that employs different loading means from this embodiment.

DESCRIPTION OF SYMBOLS 10 Test piece 21 Table 22 Support | pillar 23 Screw rod 24 Upper cross head 25 Ram cylinder 26 Lower cross head 27 Rotation drive mechanism 29 Chuck drive mechanism 31 Upper grip 32 Lower grip 33 Pressure sensor 34 Stroke detector 35 Control section 36 Display section 37 Operation section 38 Hydraulic source 39 Distance sensor 41 Claw tooth 42 Claw tooth holder 43 Holder pushing member 44 Wedge surface 45 Inclined surface 49 Fluid pressure cylinder 51 Calculation unit 52 Movement adjustment unit 53 Storage unit

Claims (3)

A wedge-shaped gripping tool having a pair of gripping teeth that come in contact with each other in a direction perpendicular to the load axis by slidingly contacting a pair of wedge surfaces formed symmetrically with respect to the load axis, and the gripping tool are respectively disposed. In a material testing machine comprising: a load mechanism that applies a test load to a test piece gripped at both ends by the gripping tool by causing the support members facing each other to be separated from each other along a load axis.
A measuring means for measuring a distance between the grippers;
Storage means for storing the relationship between the cross-sectional size of the test piece in the direction in which the gripping teeth are separated and the amount of movement of the gripping tooth in the load axis direction when the gripping teeth are brought close to each other to grip the test piece When,
The measuring means is set to the optimum distance between the gripping tools at the start of the test, which is derived based on the movement amount of the gripping teeth corresponding to the cross-sectional size stored in the storage means and the length of the test piece. Movement adjusting means for adjusting the movement of the support member so that the measured values of
A material testing machine comprising: The material testing machine according to claim 1,
The material testing machine is a photoelectric sensor that is disposed on any one of the support members and that measures the distance between the support members. The material testing machine according to claim 1,
The material testing machine, wherein the measuring means is means for calculating a distance between the support members from a driving amount of the gripping tool.

Images