JP2002318180A - Uniaxial bidirectional tensile tester and sample central part measuring device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new uniaxial bidirectional tensile tester capable of observing the variations of the width and the thickness of the center of a sample with the center of the sample set stationary and of executing stable measurement with a measuring instrument fixed as well and provide a sample central part measuring device using the uniaxial bidirectional tensile tester. SOLUTION: This tensile tester is used for carrying out a tensile test by holding both ends of the sample 10 with chucks 5 and 7, and is so structured that both the chucks 5 and 7 are moved in opposite directions at the same speed, and the variations of the width and the thickness of the stationary center of the sample are observed and measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tensile tester for a sample, and more particularly, to a uniaxial biaxial tensile tester and a sample central portion measuring device using the uniaxial biaxial tensile tester.

[0002]

2. Description of the Related Art Conventionally, a tensile tester generally used is provided with one sample gripper on one moving crosshead, and an immovable sample gripper on the other, so that these sample grippers can be moved between the crossheads. And the sample was pulled in one direction by the movement of the crosshead.

[0003]

Generally, when the relationship between stress and strain of a material is determined by a tensile test, the width and thickness of a sample are measured in advance, and these values are used in the calculation. However, for a material having a large distortion such as rubber or plastic, the width and the thickness decrease as the distortion increases. In this case, the relationship between the obtained stress and strain is
It can be said that this is an apparent stress-strain relationship. In order to determine the true stress-strain relationship, it is necessary to always observe changes in the width and thickness at the center of the sample during the tensile test and determine these values. With a conventional tensile tester, it is possible to observe the changes in the width and thickness at the center of the sample and aim at the center of the sample while moving the measuring instrument at half the tensile speed, and perform these measurements. However, there has been a problem that the measuring device receives vibrations due to movement, and when the measuring device is large, there is a problem that it cannot be moved.

[0004] In view of the above problems, the present invention makes it possible to observe changes in the width and thickness of the center of a sample in a state where the center of the sample is stationary, and to perform stable measurement with the measuring equipment fixed. An object of the present invention is to provide a novel uniaxial biaxial tensile tester and a sample center measuring device using the uniaxial biaxial tensile tester.

[0005]

SUMMARY OF THE INVENTION A uniaxial bidirectional tensile tester according to the present invention is a tensile tester for performing a tensile test by gripping both ends of a sample with grippers, wherein both grippers are moved in opposite directions at the same speed. To be moved. This allows
The center of the sample can be left stationary.

Further, a pair of drive screw shafts each having a right-hand thread portion and a left-hand thread portion having the same pitch with respect to the intermediate position are provided in parallel, and a crosshead having a gripper for grasping a sample is provided. One of the crossheads is screwed to the right-hand thread of a pair of parallel drive screw shafts, and the other crosshead is screwed to the left-hand thread, so that both drive screw shafts rotate in the same direction. Both grippers are moved in opposite directions at the same speed.

Further, a pair of parallel driving screw shafts having different screw directions from the right-hand screw and the left-hand screw are provided, and a crosshead having a gripper for gripping a sample is provided, and one of the crossheads is driven by a right-hand screw. Screw the other crosshead onto the left-hand drive screw shaft, rotate both drive screw shafts in the same direction, and move both grippers in opposite directions at the same speed. It is like that.

A pair of parallel drive screw shafts having the same screw direction as the right-hand screw or the left-hand screw are provided, and a crosshead having a gripper for gripping a sample is provided, and one crosshead is connected to one drive screw. Screw the other crosshead to the other drive screw shaft, rotate both drive screw shafts in opposite directions, and move both grippers at the same speed in opposite directions. It is.

Further, in the uniaxial bi-directional tensile tester according to the third or fourth aspect, the guide is guided at a position apart from a screwing position of each crosshead with a driving screw shaft. In the sample central portion measuring apparatus of the present invention, the uniaxial bidirectional tensile tester according to any one of claims 1 to 5 is used to observe and measure changes in the width and thickness of the stationary center of the sample. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The uniaxial bidirectional tensile tester of the present invention will be described in detail with reference to an embodiment shown in the drawings. FIG. 1 shows a general-purpose embodiment of the uniaxial bidirectional tensile tester of the present invention,
In the figure, reference numerals 1 and 1 denote a pair of parallel drive screw shafts, each of which comprises a right screw portion 2 and a left screw portion 3 having the same pitch at an intermediate position. An upper crosshead, that is, one crosshead 4 is screwed into the right-hand threaded portions 2, 2 of the pair of parallel drive screw shafts 1, 1. An upper or one gripper 5 for gripping is provided via a load cell 9. On the other hand, a pair of parallel driving screw shafts 1,
A lower crosshead, that is, the other crosshead 6, is screwed into the left-hand threaded portion 3, 3, and the other crosshead 6 is attached to the lower, that is, the other gripper 7 that grips the lower end, that is, the other end of the sample 10. Is fixedly provided. The pair of drive screw shafts 1 and 1 are rotated in the normal and reverse directions in the same direction so that the two grippers 5 and 7 are separated and approach each other.

FIG. 2 shows another embodiment of the uniaxial bidirectional tensile tester of the present invention. In the drawing, reference numerals 11 and 11 denote driving screw shafts of right-handed screw and left-handed screw having different screw directions at the same pitch, and one cross provided with one gripping tool 15 on one driving screw shaft 11 via a load cell 19. The head 14 is screwed, and the other drive screw shaft 11 is screwed with the other crosshead 16 having the other grip 17. Drive screw shaft 1 of each of these crossheads
Guides 18 and 18
It is made to guide to. By rotating the drive screw shafts 11, 11 having different screw directions in the same direction, the two grippers 15, 17 are separated from and approach to each other.

FIG. 3 shows still another embodiment of the uniaxial tensile tester of the present invention. In the drawing, reference numerals 21 and 21 denote driving screw shafts of right-handed screw or left-handed screw having the same pitch and the same screw direction.
, One crosshead 24 having one grip 25 is screwed into the other, and the other drive screw shaft 21 is screwed into another crosshead 26 having the other grip 27. . The position of the crosshead which is separate from the screwing position with the drive screw shafts 21 and 21 is defined by the guide 2.
8, 28. The drive screw shafts 21 and 21 having different screw directions are rotated forward and backward in opposite directions, so that the grippers 25 and 27 are separated and approach each other.

In each of the tensile testers of the embodiments shown in FIGS. 1 to 3, the both ends of the sample 10 are gripped between the two grippers, and both drive screw shafts are rotated so that the two grippers are separated from each other in opposite directions. Then, the respective crossheads operate to separate from each other, the tensile test of the sample 10 is performed, and the load cell measures the load. At this time, the two grippers move away from each other in the opposite directions at the same speed and the same size. As a result, the sample 10
Is in a stationary state, and a tensile test can be performed in this state.

FIG. 4 shows an embodiment of an apparatus for measuring a central portion of a sample using a uniaxial bidirectional tensile tester according to the present invention. FIG.
FIG. 1 shows an apparatus using the uniaxial bidirectional tensile tester shown in FIG. 1, but this tensile tester may be the tensile tester shown in FIG. 2 or FIG. In the uniaxial bidirectional tensile tester of the present invention, since the sample 10 is pulled in both directions, the center position of the sample 10 is at the rest position. Therefore, in the present invention, the external shape measuring device 30 is provided so as to face the center position of the sample 10 in the stationary state. The external shape measuring device 30 may be a non-contact type measuring device such as a laser type measuring device or an optical measuring device, or may be a contact type linear gauge or an ultrasonic measuring device.
Then, as shown in the figure, the load is measured by the load cell 9, the width or thickness of the center of the sample is measured by the outer shape measuring device, the elongation is measured by moving the crosshead, and these measured values are input to a computer and calculated. True stress,
The distortion relationship can be measured in real time.

The true stress-strain relationship is obtained as follows. First, the true distortion can be calculated with the following assumptions. Incompressibility D (t) × W (t) × L (t) = D (0) × W (0) × L (0): Unit volume does not change. Next, since the tension is uniaxial, the change in width is equal to the change in thickness. D (t) / D (0) = W (t) / W (0) From this relationship, the true distortion is L (t) / L (0)-1.0 = {W (0) / W (t)} × ｛W (0) / W (t)｝ −
Expressed as 1.0. Similarly, the true stress is F (t) / ｛W (t) × D (t)｝ = F (t) / ｛W (t) × W (t) × D (0) / W
(0)｝ Since the thickness is measured before deformation and the width is measured during deformation, a true stress true strain relationship can be obtained. The symbols shown in the above formula are as follows. F (t): Load D (0): Thickness before deformation W (0): Width before deformation L (0): Length before deformation D (t): Thickness during deformation W ( t): Width during deformation L (t): Length during deformation

FIG. 5 shows a conventional stress-strain relationship.
In other words, the thickness and width of the sample are measured before the test, and the values are used when calculating the stress F (t) / {W (0) × D (0)}. Also, the distortion L (t) / L (0) −1.0 at this time is the change in length L (t).
Is divided by the initial length L (0). FIG. 6 shows that the width decreases as the sample is pulled. Since this is not taken into account in FIG. 5, it can be said that this is an apparent stress-strain relationship. FIG. 7 shows the relationship between stress and strain based on the width measured in real time based on the results of FIG. 5 and FIG. 6 (true stress-strain relationship).
Compared to FIG. 5 showing the apparent stress-strain relationship, it can be seen that the rise of the true stress is slower and rises linearly.

[0017]

According to the uniaxial bidirectional tensile tester of the present invention,
According to the structure as shown in claims 1 to 4, both grippers are moved in opposite directions at the same speed, so that the center of the sample under test is kept stationary, and the width of the center of the sample and It has the effect of observing and measuring changes in thickness. Also, the measurement device can be stably measured in a fixed state.

The sample central portion measuring apparatus of the present invention, which observes and measures changes in the width and thickness of a stationary center using the uniaxial bidirectional tensile tester of the present invention, can measure measured values in real time. By inputting the values into a computer and calculating the values, the true stress-strain relationship can be measured in real time.

[Brief description of the drawings]

FIG. 1 is a front view of one embodiment of a uniaxial bidirectional tensile tester of the present invention.

FIG. 2 is a front view of another embodiment.

FIG. 3 is a front view of still another embodiment.

FIG. 4 is an explanatory front view of a sample central portion measuring apparatus using the uniaxial bidirectional tensile tester of the present invention.

FIG. 5 is a diagram showing a stress-strain relationship obtained by testing natural rubber with a conventional tensile tester.

FIG. 6 is a diagram showing a relationship between width and strain during a tensile test.

FIG. 7 is a diagram showing a relationship between true stress and true strain.

[Explanation of symbols]

 1,11,21 drive screw shaft 2 right screw part 3 left screw part 4,14,24 one crosshead 5,15,25 one gripper 6,16,26 other crosshead 7,17,27 other Grasping tool 9,19,29 Load cell 10 Sample 18,28 Guide 30 Profile measuring instrument

Claims (6)

[Claims] 1. A uniaxial bidirectional tensile tester for gripping both ends of a sample with grippers and performing a tensile test, wherein both grippers are moved in opposite directions at the same speed. 2. A crosshead having a pair of drive screw shafts each having a right-hand thread portion and a left-hand thread portion having the same pitch at an intermediate position and being provided in parallel, and each having a gripper for grasping a sample is provided. One of the crossheads is screwed to the right-hand thread of a pair of parallel drive screw shafts, and the other crosshead is screwed to the left-hand thread, so that both drive screw shafts rotate in the same direction. The uniaxial bidirectional tensile tester according to claim 1. 3. A pair of parallel drive screw shafts having screw directions different from those of a right-hand screw and a left-hand screw are provided, and a crosshead having a gripper for gripping a sample is provided, and one of the crossheads is driven by a right-hand screw. 2. The uniaxial bidirectional tensile tester according to claim 1, wherein the screw shaft is screwed, the other crosshead is screwed to a left-handed drive screw shaft, and both drive screw shafts are rotated in the same direction. 4. A pair of parallel driving screw shafts having the same screw direction as a right-handed screw or a left-handed screw are provided, and a crosshead having a gripper for gripping a sample is provided, and one crosshead is connected to one driving screw. 2. The uniaxial bidirectional tensile tester according to claim 1, wherein the uniaxial biaxial tensile tester is screwed to the shaft, the other crosshead is screwed to the other drive screw shaft, and both drive screw shafts are rotated in opposite directions. 5. The uniaxial bidirectional tensile tester according to claim 3, wherein the guide guides a position of the crosshead apart from the screwing position with the drive screw shaft. 6. A sample center portion measuring apparatus for observing and measuring changes in the width and thickness of a stationary center of a sample using the uniaxial bidirectional tensile tester according to claim 1.