JP3165156U - Extensometer - Google Patents

Abstract

Provided is an extensometer that can measure two types of distances between marked lines by using one extensometer without replacing parts in order to correspond to two types of distances between marked lines. Among a pair of upper and lower arms 1 and 26 having knife edges 7 and 8 in contact with a marked line of a test piece S, the upper arm 26 is a movable arm 3 to which the knife edge is fixed. And the measurement arm 2 fastened to the detection unit, and by changing the fastening position of the movable arm 3 with respect to the measurement arm 2, it is possible to cope with two types of distance L between the marked lines. [Selection] Figure 1

Description

  The present invention relates to a contact-type extensometer for mounting on a test piece and measuring its elongation when performing a tensile test of the test piece with a material testing machine.

  There are non-contact type and contact type extensometers for measuring the elongation of a test piece in a material testing machine. In a contact extensometer, the knife edges provided at the tips of a pair of upper and lower arms are brought into contact with the upper and lower marked lines of the test piece, respectively, and the amount of opening and closing of both arms driven by the displacement of the marked line is measured. A test piece extensometer is known (see Patent Document 1).

  Conventionally, as a contact type extensometer, a differential transformer type displacement gauge or a strain gauge is used as a sensing member, and its structure and measurement principle are basically the standards above and below the test piece. By transmitting the displacement between the fixtures in contact with the wire and each of the fixtures to a differential transformer type displacement meter, or transmitting it to a strain generating member to which a strain gauge is attached and bending it. The elongation between the upper and lower marked lines of the test piece is measured (see Patent Document 2).

  In the tensile test, measurement of strain: ε (= ΔL: sample change length / L: distance between marked lines) and the like requires setting of the distance between marked lines (L), which is the sample standard length before loading. The distance between marked lines is defined by ISO and JIS. Conventionally, in the domestic plastic tensile test, L = 50 mm recommended by JISK7113 has been set. However, in recent years, L = 75mm is newly added, and it is necessary to support two types of distances between marked lines.

  In order to cope with the distance between two types of marked lines, either one dedicated extensometer is prepared, or the “main body” that takes out the elongation signal, and the “arm” that uses the knife edge to contact the specimen A part of the “part” is separated and replaced with an arm part having a different length according to the distance between the marked lines, so that one main body supports two types of distances between the marked lines.

  FIG. 4 shows an outline of a conventional extensometer. FIG. 4A shows a configuration diagram (side view) in the case where the distance between marked lines L = 50 mm, and FIG. 4B shows the distance between marked lines L = 75 mm. In the conventional strain gauge extensometer, when the distance L between the marked lines is 50 mm, as shown in FIG. 4A, one end of the upper arm 12 and the lower arm 11 is connected to the horizontal spring 15 and the vertical via the auxiliary arm 14. The upper knife edge 17 and the lower knife edge 18 are attached to the other ends of the upper and lower arms. The horizontal spring 15 and the vertical spring 16 are disposed so as to be orthogonal to each other, and a strain gauge 30 is attached near the center of the vertical spring 16, and an output signal thereof is sent to a measuring device (not shown). The sensor portion of the extensometer composed of the horizontal spring 15, the vertical spring 16, the strain gauge 30, and the like is covered with a case 29.

  The extensometer is attached to the test body S by pressing both knife edges against the test body S by the restraints 31 and 32. At this time, the distance between the upper knife edge 17 and the lower knife edge 18 is adjusted to be a predetermined distance L between the marked lines. When a tensile load is applied to the specimen S and elongation occurs between the marked lines, the distance between the upper and lower knife edges opens following the elongation between the marked lines, and the longitudinal spring 16 that is the sensing part is bent. It will be. Along with this, distortion corresponding to the deflection of the vertical spring 16 (that is, the opening amount of the upper and lower arms) is generated in the strain gauge 30 adhered to the vertical spring 16, and the change in resistance value of the strain gauge 30 is built in the measuring device. The elongation of the specimen S is measured by detecting with a bridge circuit.

  Next, when the distance L between the marked lines is 75 mm, the bolt 24 and the upper knife edge 17 of FIG. 4A are removed as shown in FIG. The distance between the marked lines is changed to L = 75 mm by fixing to the arm 12, and the elongation is measured.

JP 2003-240690 A JP-A-6-201309

  In the conventional arm exchange system, it is necessary to prepare an exchange arm, and in order to obtain accuracy and reproducibility in testing, the body side to which the exchange arm is attached has a structure with a contact surface, and both parts are attached. The fastening operation must be performed in a state of being pressed with good reproducibility, and there is a troublesome replacement operation. From such a background, there has been a demand for an extensometer that can handle the measurement of two types of distances between marked lines with one extensometer without replacing parts.

  A pair of upper and lower arms having a knife edge in contact with the mark of the test piece at the tip, a restraining tool for fixing the pair of arms to the test piece, and a signal corresponding to a change in the distance between the pair of arms In the extensometer provided with a detecting unit that outputs the upper arm, the upper arm is separated into a movable arm to which the knife edge is fixed and a measuring arm fastened to the detecting unit, and the movable arm has a plurality of limitations in the tensile direction. It is structured to be detachable from the measuring arm at the position.

  Each of the movable arm and the measuring arm is provided with a fixing surface for fixing the movable arm and the measuring arm perpendicular to the pulling direction. The movable arm is provided with an opening, and the measuring arm has a protrusion. It is provided and has a structure that regulates a shift in the left-right direction when the protrusion fits into the opening.

  By separating the upper arm into a movable arm and a measuring arm, and selecting the fastening position of both the arms, it is possible to cope with a plurality of distances between the marked lines.

  With the configuration described above, an extensometer that has no replacement parts and can accurately handle tensile tests at a plurality of distances between marked lines can be obtained.

It is a schematic block diagram of the extensometer in the Example of this invention. It is explanatory drawing of the movable arm in the Example of this invention. It is explanatory drawing of the measurement arm in the Example of this invention. It is a schematic block diagram of the conventional extensometer.

  FIG. 1 shows a schematic configuration of an extensometer in an embodiment of the present invention. FIG. 1A shows a configuration diagram (side view) when the distance between marked lines L = 50 mm, and FIG. 1B shows the distance between marked lines L = 75 mm. The strain gauge type extensometer of the present embodiment has an upper arm portion 26 including a measuring arm 2, a movable arm 3 and an auxiliary arm 4, as shown in FIG. One end of the lower arm 1 is connected by a horizontal spring 5 and a vertical spring 6, and an upper knife edge 7 and a lower knife edge 8 are attached to the upper arm portion 26 and the other end of the lower arm 1, respectively. The horizontal spring 5 and the vertical spring 6 are disposed so as to be orthogonal to each other, and a strain gauge 10 is attached near the center of the vertical spring 6, and an output signal thereof is sent to a measuring device (not shown). In this case, the measurement arm 2 and the movable arm 3 are fixed to the orthogonal plane at the upper part of both arms by the bolts 20 and 21 and the plate 27.

  The extensometer is attached to the test body S by pressing both knife edges against the test body S by the restraints 9 and 19. At this time, the distance between the upper knife edge 7 and the lower knife edge 8 is adjusted to be a predetermined distance (L) between the marked lines. When a tensile load is applied to the specimen S and elongation occurs between the marked lines, the distance between the upper and lower knife edges opens following the elongation between the marked lines, and the longitudinal spring 6 that is the sensing part is bent. It will be. Along with this, strain corresponding to the deflection of the vertical spring 6 (that is, the opening amount of the upper and lower arms) is generated in the strain gauge 10 adhered to the vertical spring 6, and the change in the resistance value of the strain gauge 10 is built in the measuring device. The elongation of the specimen S is measured by detecting with a bridge circuit.

  Next, when the distance L between the marked lines is 75 mm, as shown in FIG. 1B, the measurement arm 2 and the movable arm 3 are fixed to the orthogonal plane below the two arms by bolts 20 and 21 and the plate 27. Accordingly, the distance between the marked lines is changed to L = 75 mm, and the elongation is measured. The sensor portion of the extensometer composed of the horizontal spring 5, the vertical spring 6, the strain gauge 10, and the like is covered with a case 28.

  FIG. 2 is an explanatory diagram of the movable arm 3 in the embodiment of the present invention. FIG. 2A shows a front view, and FIG. 2B shows a side view. In this embodiment, when the mounting position of the measuring arm 2 and the movable arm 3 is changed due to the change in the distance between the marked lines, the J plane and the L plane which are the mounting surfaces of the measuring arm 2 or the movable arm 3 in order to maintain the test accuracy. The geometrical accuracy such as the perpendicularity between the K-plane and the L-plane and the flatness of the contact surface needs to match the test accuracy. In addition, the movable arm 3 has a rectangular opening 35, and the protruding portion 36 of the measurement arm 2 shown in FIG. 3 is fitted, so that the shift in the left-right direction is restricted when the attachment position is changed due to the change in the distance between the marked lines.

  FIG. 3 is an explanatory diagram of the measurement arm 2 in the embodiment of the present invention. 3A shows a front view, and FIG. 3B shows a side view. In this embodiment, when the mounting position of the measuring arm 2 and the movable arm 3 is changed due to the change in the distance between the marked lines, the D surface and the F surface which are the mounting surfaces of the measuring arm 2 or the movable arm 3 in order to maintain the test accuracy. The geometrical accuracy such as the perpendicularity between the E surface and the F surface and the flatness of the contact surface needs to match the test accuracy. Further, the measurement arm 2 includes the protruding portion 36 and is fitted into the rectangular opening 35 of the movable arm 3 as described above, and restricts the shift in the left-right direction when changing the attachment position accompanying the change in the distance between the marked lines.

  As shown in FIGS. 1A and 1B, the measuring arm 2 and the movable arm 3 with respect to the two types of distances between the marked lines are fastened with bolts 20 by applying a surface perpendicular to the tensile direction. Therefore, the movable arm 3 does not shift with respect to the opening of the arm due to the enlargement between the upper and lower marked lines during the test. If the measurement arm 2 and the movable arm 3 are fixed by a combination of a screw hole and a through hole from the side with a plane parallel to the tensile direction, the screw is displaced in the through hole. A slip occurs between the measurement arm 2 and the movable arm 3 and causes deterioration in test accuracy.

  The detection method of the extensometer of the present embodiment is a strain gauge method, but other than the strain gauge method, for example, a differential transformer type displacement meter may be used as long as it is a contact type extensometer.

1, 11 Lower arm 2 Measuring arm 3 Movable arm 4, 14 Auxiliary arm 5, 15 Horizontal spring 6, 16 Vertical spring 7, 17 Upper knife edge 8, 18 Lower knife edge 9, 19 Constraint tool 10, 30 Strain gauge 12 Upper Arm 13 Exchange arm 20, 21, 24, 25 Bolt 26 Upper arm 27 Plate 28, 29 Case 31, 32 Restraint 35 Opening 36 Projection S Specimen L Distance between marked lines

Claims (3)

  A pair of upper and lower arms having a knife edge in contact with the mark of the test piece at the tip, a restraining tool for fixing the pair of arms to the test piece, and a signal corresponding to a change in the distance between the pair of arms In the extensometer provided with a detecting unit that outputs the upper arm, the upper arm is separated into a movable arm to which the knife edge is fixed and a measuring arm fastened to the detecting unit, and the movable arm has a plurality of limitations in the tensile direction. An extensometer characterized by having a structure that is detachable from the measuring arm at a position.   The extensometer according to claim 1, wherein each of the movable arm and the measuring arm is provided with a fixing surface for fixing the movable arm and the measuring arm perpendicular to the tensile direction.   The movable arm is provided with an opening, the measurement arm is provided with a protrusion, and the protrusion is fitted into the opening to restrict a lateral shift. Item 3. Extensometer according to item 1 or 2.

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