JPH0531549Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Purpose of the Invention] (Field of Industrial Application) The present invention relates to a specimen fracture detection device used for tensile fracture testing of metal materials whose surfaces are insulated.

(Prior Art) One of the testing methods for metal materials is a tensile rupture test.

In this tensile rupture test, both ends of the test piece are gripped by the chucks of a material testing machine, and a tensile force is applied between these chucks to measure and record the tensile force that causes the test piece to break. This is often carried out using a test piece fracture detection device that uses electric current. That is, a plurality of contacts are attached to the test piece at a predetermined distance, and a current is passed through the test piece, and when the current breaks due to the test piece breaking, the breakage of the test piece is caused by passing through these contacts. I'm trying to detect it.

The conventional test piece fracture detection device described above can be used without any problems when the test piece is a bare metal material, but when an insulating film such as an oxide film is formed on the surface of the test piece, Since the contact and the conductive portion of the test piece are insulated by the insulating coating, it is not possible to detect breakage of the test piece due to current.

(Problem to be solved by the invention) In such a case, the insulation coating on the surface of the test piece to which the contact is attached must be peeled off in advance, which is time-consuming, and when the insulation coating is peeled off, the test piece There was a problem in that it damaged the material and caused an error in the tensile rupture test values.

[Structure of the idea]

(Means for Solving the Problems) The test piece breakage detection device of the present invention was made to eliminate the above-mentioned drawbacks in the background art. Contactors are attached to the test piece at predetermined intervals, and a high voltage sufficient to destroy the insulation coating of the test piece is applied to these contacts, and the breakdown of the insulation coating is applied to the test piece. The present invention is characterized by comprising a power source and an electric circuit that flow a low current, and a rupture detector that produces an output when the current becomes zero due to rupture of the test piece.

(Function) According to the test piece breakage detection device of the present invention configured as described above, the insulating coating of the test piece is first broken by the high voltage from the electric circuit, and the contactor and the test piece are connected through these breaking points. Electricity can be passed between the pieces. With this energization, the voltage between the contacts drops to a low voltage, keeping the circuit in a safe state. Therefore, a break in the test piece can be detected by detecting this disconnection of the test piece current using a break detector.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

In the figure, a test piece 2 having an insulating film 1 such as an oxide film on the surface of a metal material is held between chucks 3 and 4 of a material testing machine via an insulator (not shown) if necessary.

Contacts 5 and 6 are attached to this test piece at a predetermined distance. These contacts 5 and 6 are connected to the secondary side of the leakage transformer 9 via lead wires 7 and 8, and on the other hand, there is a point in the middle of the lead wire 8 where the secondary current becomes zero. A break detector 10 is inserted which generates an output signal. A power source 11 is connected to the primary side of the leakage transformer 9.

In the test piece rupture detection device of the present invention configured as described above, the voltage of the power source 11 is transferred to the leakage transformer 9.
Immediately after the start of the test, the secondary side of the leakage transformer 9 does not become a closed loop due to the insulating coating 1 interposed between the contacts 5, 6 and the test piece 2, and no secondary current flows; The rupture detector 10 is interlocked by a circuit (not shown) so that no signal is output, and as a characteristic of the leakage transformer 9, its secondary side voltage becomes high, and this high voltage causes the contacts 5,
The insulating coating 1 interposed between the test piece 6 and the test piece 2 is broken and conductive.

At the same time, the leakage magnetic flux increases, the secondary side drops to a low voltage, the circuit is kept in a safe state, and the interlock of the rupture detector 10 is released.

In this state, the material testing machine is operated in the same manner as before to apply a tensile force between the chucks 3 and 4 to break the test piece.

When the test piece 2 breaks, the secondary circuit of the leakage transformer, which had previously formed a closed loop, becomes open and the secondary current becomes zero, so a break detection signal is output from the break detector 10, which detects the break in the test piece. inform.

In the above explanation, an example has been described in which a leaky transformer is used as an electric circuit for generating high voltage and limiting current, but the present invention is not limited to this. For example, a DC power source may be used as a power source,
A resistance circuit with a high voltage drop resistance is used in place of the leakage transformer 9, and a high voltage acts on the insulation coating until the insulation coating breaks down, and after the insulation coating breaks down, the current flowing through the test piece 2 is a low value. It may be kept at .

[Effect of idea]

As mentioned above, in the test piece breakage detection device of the present invention, even if the test piece is a conductive material with an insulating coating on its surface, the insulating coating will be destroyed by the high voltage generated when the power is turned on. , through which the test piece can be energized.

Therefore, the process of peeling off the insulation coating can be omitted, improving test efficiency, and avoiding the possibility of damaging the test piece and disrupting the tensile strength of the test piece when the insulation coating is peeled off. .

[Brief explanation of the drawing]

The figure is a circuit diagram showing an embodiment of the test piece fracture detection device of the present invention. 1... Insulating coating, 2... Test piece, 3, 4... Chack, 5, 6... Contact, 7, 8... Lead wire, 9... Leakage transformer, 10... Fracture detector,
11...Power supply.

Claims (1)

[Claims for Utility Model Registration] 1. Contacts attached at predetermined intervals to a conductive test piece having an insulating coating attached between the chucks of a material testing machine;
a power source and an electric circuit that apply a high voltage sufficient to break down the insulating coating of the test piece and flow a low current to the test piece after the insulating film is broken; the current becomes zero due to the breakage of the test piece; A test piece breakage detection device comprising: a breakage detector that produces an output when: 2. The test piece breakage detection device according to claim 1, wherein the electric circuit comprises a leakage transformer. 3. The test piece breakage detection device according to claim 1, wherein the electric circuit comprises a resistance circuit.