JPH0742120Y2 - Material testing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a material testing machine such as a Vickers hardness testing machine or a micro Vickers hardness testing machine in which the load start time is shortened.

[Prior Art] In a material testing machine of this type, for example, a Vickers hardness testing machine, an operator has conventionally manually applied a predetermined load to a sample to form an indentation. A hardness tester that applies a load of 1 has been proposed. In this type of testing machine, a current is applied to an electromagnetic drive unit having a magnet and a coil unit to lower an indenter toward a test piece. At this time, the current is gradually increased, for example, it is configured to increase in proportion to time, and the current value when the indenter contacts the sample surface is used as a reference to calculate the increase in current from that value. The applied load is controlled.

[Problems to be Solved by the Invention] However, in the above tester, there is a problem that it takes a considerably long time to bring the indenter, which is separated from the sample at the start of the test, to the load start position where it comes into contact with the sample surface. there were.

For example, in an ultra-micro hardness tester that performs a test with a small load of about 500 mg or less, assuming that the initial interval between the indenter and the sample is, for example, about 12 μm, it took about 3 minutes until the load at which the indenter abuts the sample is started. .

This type of hardness tester is often used as a daily routine inspection at a production site or the like, and the time loss until the start of the load becomes a large loss. For example, 3 before the load starts
If a test of 100 points (n = 100) is performed with a tester that requires minutes, a loss of 5 hours will occur. If this 3 minutes can be shortened to, for example, 1 minute, a 100-point test will shorten the time by 200 minutes.

[Means for Solving Problems] In order to solve the above problems, the present invention employs the following configuration.

That is, the material testing machine according to the present invention comprises an indenter pushed into the sample surface and a load mechanism for electromagnetically driving the indenter in response to a signal from the controller to apply a test load to the indenter in contact with the sample surface. And a displacement detector for inputting an electric signal according to the displacement amount of the indenter to the control unit, and this control unit uses the same sample for the first test in which the indenter is the surface of the sample. It is characterized in that the position where the indenter is brought into contact with the sample is memorized, and in the second and subsequent tests, a signal for promptly bringing the indenter closer to the sample is output to just before the stored contact position.

[Operation and Effect] In the same test, the position (zero point) where the indenter contacts the sample surface is stored in the first test, and the second and subsequent tests are performed in the first test. Since the indenter is quickly brought close to the sample just before the stored load start position, the loss time in the test is small.

[Examples] Examples described in the drawings will be described below.

The material testing machine 1 is an ultra-micro hardness meter and includes an indenter 2 and a load mechanism 3 that drives the indenter. The load mechanism 3 comprises a coil portion 3a and a permanent magnet 3b, and the indenter 2 is attached to the coil portion 3a. A substantially L-shaped displacement detection bar 5 is attached to the indenter 2, and the tip of the displacement detection bar is the iron core 7a of the differential transformer type displacement detector 7. A coil part wound around a cylindrical bobbin is provided outside the iron core 7a.
7b is provided.

The load mechanism (indenter drive unit) three coil units 3a are connected to the control unit 9 so that the indenter 2 can be moved up and down by controlling the direction of the current. A load detection unit 11 is interposed between the coil unit 3a and the control unit 9, and the load current supplied to the coil unit 3a is measured. Further, the coil section 7b of the differential transformer type displacement detector 7 is also connected to the control section 9, and a voltage corresponding to the displacement amount of the displacement detection bar 5 that moves together with the indenter 2 is input to the control circuit 9. .

A sample table 13 is provided below the indenter.
Fifteen are placed on this.

The control unit 9 of the material testing machine 1 stores the position where the indenter 2 comes into contact with the sample 15, that is, the load start position (zero point) in the test performed in advance, and the indenter 2 just before the zero point in the next test. Has a function of quickly approaching the sample. FIG. 2 shows the structure of the indenter approach speed control mechanism in the control unit 9. The output from the CPU 20 is the latch 21,
It is transmitted to the coil portion 3a of the load mechanism 3 via the D / A 22 and the current amplifier circuit 23 to drive the indenter 2. On the other hand, the voltage extracted from the terminals of the load coil unit 3a is V / F 25, counter 26
It is designed to be input to the CPU 20 via.

When conducting a test using this material testing machine 1, the sample 15 is first mounted on the sample table 13. At this time, the indenter 2 and the sample
It is usually necessary to set the interval between 15 and 10 to 12 μm in order to prevent damage to the indenter due to an erroneous operation or the like.

When the test is started in this state, a load current is passed from the control unit 9 to the load mechanism 3. This load current (DC current)
Is controlled by the control unit 9 so that the load itself detected by the load detection unit 11 continues to increase at a constant rate.

On the other hand, the displacement detector 7 monitors the amount of movement of the indenter 2, and the displacement information of the indenter is sent to the controller 9. Indenter 2 is sample 15
It smoothly descends until it comes into contact with, but from the moment it comes into contact with the sample 15, the descending speed drops rapidly, and the displacement approaches zero. If a load is further applied from here, the indenter bites into the sample and the displacement increases. The descending speed until the indenter 2 touches the sample 15 needs to be a slow speed in order to prevent the indenter from bouncing or biting into the sample at the moment when the indenter touches the sample. Therefore, it is necessary to increase the load current slowly.

FIG. 3 (a) is a graph showing changes with time of the load current Li and the displacement output D in the first test,
The indenter 2 and the sample 15 contact each other at the point A. At this time, the displacement value is Do and the load current value is Lio. From here, the load current value Lif corresponding to the preset load value is further applied, and the displacement amount Df at that time is measured.

The displacement Do at the measurement start point in this first test is CP
Input to U20, but here for the second test Do
From the above, a predetermined minute displacement amount d (for example, 1 μm) is subtracted to obtain Do ′ (Do ′ = D−d). Then, from the second test, as shown in FIG.
A load current is passed at a high speed up to this Do 'point, and the test is controlled from the Do' point to the same condition as the first test. D
The time to reach o'is B, and in the illustrated example, A in the second test is shortened to about 1/3 of that in the first test, but the speed to reach point B is further increased. By making it faster, the time required for the test can be further shortened.

Although the indenter 2 is moved in the above example, the sample 15 may be moved to the indenter side instead of the indenter 2, and the entire load mechanism may be lowered.

[Brief description of drawings]

DESCRIPTION OF THE INVENTION FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG.
The figure is a block diagram showing the configuration of the indenter approach speed control mechanism in the control section, and FIGS. 3 (a) and 3 (b) are graphs showing changes in displacement and load current with time. 1 ... Material tester, 2 ... Indenter, 3 ... Load mechanism, 5 ... Displacement detection bar, 7 ... Displacement detector, 9 ... Control section, 15 ... Sample

Claims (1)

[Scope of utility model registration request] 1. An indenter pushed into a sample surface, a load mechanism that electromagnetically drives the indenter by a signal from a control unit, and applies a test load to the indenter abutting the sample surface, and a displacement amount of the indenter. And a displacement detector for inputting an electrical signal corresponding to the control unit to the control unit, which controls the position of the same sample in which the indenter is in contact with the sample surface in the first test. A material testing machine characterized by storing and outputting a signal for promptly bringing the indenter closer to the sample just before the stored contact position in the second and subsequent tests.