JPH0629718Y2 - Material testing machine - Google Patents

Description

Detailed Description of the Invention A. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material testing machine provided with a grip with an eccentricity removing mechanism adapted to remove an eccentric initial load of a test piece, which occurs when the test piece is screwed and gripped.

B. 2. Description of the Related Art FIG. 4 shows a conventional screw type grip, which is a grip body 1
The test piece 2 is screwed on and locked by the lock nut 3. The other end of the test piece 2 is also similarly gripped.

C. However, when gripping the upper and lower ends of the test piece 2 with a pair of screw-type grips, the test piece 2 tilts due to the accuracy of the thread and the parallelism between the upper and lower grips. Eccentric load may work. For example, if a fatigue test is performed with this eccentric load working, the test piece 2 will buckle before fatigue failure, and the fatigue test that took a long time will be completely wasted, and the test must be restarted from the beginning. There wasn't. This tendency was remarkable especially under the test conditions in which the strain amount was large (for example, 1%) and the strain rate was fast.

A technical problem of the present invention is to correct the inclination of the test piece while removing the eccentric initial load while fixing the both ends with screws.

D. Means for Solving the Problem A grip with an eccentricity removing mechanism according to claim 1 will be described with reference to the embodiment of FIG. 1. The grip has an internal thread 11a with which a male thread 12a of a test piece 12 is screwed. Body 11
A nut 13 screwed to the male screw 12a of the test piece 12 screwed to the grip body 11, and the nut 13
A gap S is formed between the bottom surface of the grip and the upper surface of the grip body 11, and the gap S is adjusted to correct the inclination θ of the test piece 12.

The grip of claim 2 will be described with reference to the embodiment shown in FIGS. 2 and 3. As the correcting means 14, the electrostrictive element 24 interposed between the bottom surface of the nut 23 and the top surface of the grip body 11 will be described. Is used to detect the inclination θ of the test piece 12, and the electrostrictive element 24 so that the detected inclination θ is corrected based on the signal from the inclination detection unit 15.
And a control means 30 for driving the.

E. In the invention of claim 1, the inclination θ of the test piece 12 is corrected by adjusting the distance S between the nut 13 and the upper surface of the grip body 11 by the correction means 14. For example, four strain gauges 15 are attached to the peripheral surface of the test piece 12, and the jack bolts 14 adjust so that the outputs of the strain gauges 15 are equal.
This removes the eccentric load.

According to the invention of claim 2, the electrostrictive element 24 is driven by the control circuit 30 so that the inclination is not detected by the detecting means 15 (so that θ = 0), whereby the inclination of the test piece 12 is increased. Is corrected to remove the eccentric load.

It should be noted that, in the above D and E for explaining the configuration of the present invention, the drawings of the embodiments are used to make the present invention easy to understand, but the present invention is not limited to the embodiments.

F. Embodiment-First Embodiment-FIG. 1 shows a first embodiment.

A female screw 11a is engraved on the grip body 11, and a male screw 12a of the test piece 12 is screwed into the female screw 11a. The nut 13 is provided with four jack bolts 14 at equal intervals in the circumferential direction. The nut 13 is attached to the test piece 12 so that a space S is formed between the bottom surface of the nut 13 and the upper surface of the grip body 11. It is screwed. 4 jack bolts 14
The interval S is adjusted by screwing the screw in and out to correct the inclination θ of the test piece 12.

Strain gauges 15 _-1 to 15 _-4 are evenly spaced on the peripheral surface of the test piece 12.
Is provided and outputs a signal corresponding to the eccentric load acting on the test piece 12. Therefore, the inclination of the test piece 12 can be corrected by screwing and screwing the jack bolts 14 so that the signals from the strain gauges 15 are equal to each other and adjusting the interval S.

-Second Embodiment- A second embodiment will be described with reference to FIGS. 2 and 3.

In this embodiment, the distance S between the nut and the grip body is adjusted by an electrostrictive element instead of the jack bolt.
The same parts as those in the figure will be described with the same reference numerals.

Four electrostrictive elements 24 are provided at equal intervals on a predetermined radius centered on the screw hole around the female screw 11a formed in the grip body 11. The electrostrictive element 24 is driven by the control circuit 30 shown in FIG. 3 to expand and contract in the axial direction of the test piece 12, and adjusts the distance S between the bottom surface of the nut 23 and the upper surface of the grip body 11. The nut 23 is not provided with the jack bolt 14.

In FIG. 3, the outputs of the four strain gauges 15 _-1 to 15 _-4 are input to the adder 32 through the amplifiers 31 _{-1 to} 31 _-4 and added respectively. The output of the adder 32 is the divider 3
It is input to 3 and divided by 4 to obtain the average value. The output of the divider 33 is input to the non-inverting input terminal of the deviation unit 34 _-1 to 34 _-4, the deviation between the output and the divider 33 of the amplifier 31 _-1 to 31 _-4 DOO To be Each deviation device 34 _-1 ~ 3
4 Output _-4 is input to the control terminal of the power source 35 _-1 to 35 _-4, the power supply 35 _-1 to 35 _-4, is input to the power supply voltage + V being applied to the control terminal and the signal The voltage is adjusted according to the above and applied to each electrostrictive element 24 _{-1 to} 24 _-4 .
As a result, each electrostrictive element 24 _{-1 to} 24 _-4 expands and contracts according to the applied voltage, and each electrostrictive element 24 _-1 is output in a state where the outputs of the strain gauges 15 _-1 to 15 _-4 are equal. The expansion / contraction amount of up to 24 _-4 is maintained, and the inclination θ of the test piece 12 is automatically corrected by this.

In the above embodiments, the number of jack bolts 14 and electrostrictive elements 24 is not limited to four. Further, the jack bolt 14 in the first embodiment may be replaced with the electrostrictive element 24. Further, in the structure in which the bottom surface of the nut 23 is in direct contact with the electrostrictive element 24, a shearing force acts on the electrostrictive element 24. It is desirable not to act. Furthermore, the above-described eccentricity removing mechanism may be attached to the upper and lower grips, or only one of them may be attached.

Further, the present invention can be applied not only to the fatigue testing machine but also to a simple compression / tensile testing machine.

G. Effect of the Invention According to the present invention, since the inclination of the test piece can be corrected by the jack bolt or the electrostrictive element and the eccentric load can be removed, for example, the test piece is prevented from undesirably buckling during the fatigue test. In addition, highly reliable test results can be obtained in simple compression and tensile tests.

[Brief description of drawings]

FIG. 1 is for explaining the first embodiment, (a) is a layout of jack bolts, and (b) is a longitudinal sectional view. 2 and 3 illustrate the second embodiment,
2 (a) and 2 (b) are a layout view of the electrostrictive element, a vertical sectional view, and FIG. 3 is a control circuit for driving the electrostrictive element. FIG. 4 is a vertical sectional view for explaining a conventional example. 11: Grasping tool body, 11a: Female screw 12: Test piece, 12a: Male screw 13, 23: Nut 14: Jack bolt, 15: Strain gauge 24: Electrostrictive element, 30: Control circuit

Claims (2)

[Scope of utility model registration request] 1. A grip body having a female screw engraved therein, into which a male screw of a test piece is screwed, a nut screwed to the male screw of the test piece screwed to the grip body, and a nut of the nut. A material testing machine having a grip with an eccentricity removing mechanism, comprising: a clearance between a bottom surface and an upper surface of the grip body, and a correction means for adjusting the clearance to correct the inclination of the test piece. 2. A grip body in which a female screw to which a male screw of a test piece is screwed is engraved, a nut screwed to the male screw of the test piece screwed to the grip body, and a nut of this nut. An electrostrictive element interposed between the bottom surface and the top surface of the grip body, a tilt detecting means for detecting the tilt of the test piece, and a signal from the tilt detecting means, the detected tilt is A material testing machine having a grip with an eccentricity removing mechanism, comprising a control means for driving an electrostrictive element so as to be corrected.