JPH08233713A - Method for indentation hardness testing - Google Patents

Abstract

PURPOSE: To obtain a stabilized measurement of hardness by measuring the depth of indentation of an indenter for a predetermined time after a set load is reached before plastic deformation is finished thereby preventing the measurement error. CONSTITUTION: Upon receiving a load current from a CPU 15, an electromagnetic force generation means 4 generates an electromagnetic force for pushing an indenter 2 into a sample 1 and displacement of the indenter 2 is detected by means of a displacement detector 3. The detection signal and a load current are read out in the form of voltage values and converted into frequency signals 8, 9 which are then counted 10, 11 to feed a load/displacement data to the CPU 15 where the data is processed and delivered to a CRT 19. In this regard, several load values are preset as measuring points and when a set load is reached, increment of load current to the means 4 is interrupted and the set load is sustained for a predetermined time. Subsequently, the indentation depth of the indenter 2 is measured for a predetermined time after the set load is reached before the plastic deformation is finished. The measurement is carried out for each set load and the hardness of sample is determined based on two sets of load and indentation depth.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test method in which a test load is applied to an indenter and the hardness of the sample is determined from the depth of indentation of the indenter into the sample surface at that time. Regarding suitable test methods.

[0002]

2. Description of the Related Art A conventional indentation hardness test method is to set a zero point at a point where an indenter and a sample surface are in contact with each other, load the indenter up to a preset load, and after holding for a certain time, indent the indenter pressed on the sample surface. The depth is measured, and the sample hardness is calculated from the load and the indentation depth. Further, as shown in FIG. 3, from the load-pushing depth diagram obtained by obtaining the load and the pushing depth when the indenter is pushed into the sample, two sets of load and pushing depth (P1 And D1, P2 and D2) are also available to calculate the hardness of the sample.

[0003]

Among the above-mentioned conventional methods, the former method has a problem that a measurement error is likely to occur due to the influence of the tip shape of the indenter and the surface roughness of the sample. Also,
In the latter, since the indentation depth is dynamically measured under load, there is a problem in that the data easily fluctuates and only the indentation hardness can be obtained.

Therefore, an object of the present invention is to provide an indentation hardness test method capable of preventing a measurement error due to the surface roughness of a sample or the like and measuring a stable static hardness.

[0005]

In order to solve the above problems, the present invention adopts the following configuration.

That is, the indentation hardness test method according to the present invention is a method for indentation hardness test of an indenter which is pushed into the sample surface by the test load while continuously and gradually increasing the test load applied to the indenter. When the preset test load is reached, the increase of the test load is stopped for a fixed time until the plastic deformation is almost completed, the set load is maintained, and the indenter indentation depth is measured at the time when this fixed time elapses. The above process is continuously performed twice or more, and the hardness of the sample is calculated from two sets of load and indentation depth data.

After the indenter contacts the surface of the sample, the load is increased until it reaches a preset test load. After the preset test load is reached, the load increase is stopped for a period of time during which the plastic deformation almost stops. Is held, and the indentation depth at which the indenter is pressed into the sample is measured during this period. This step is continuously performed twice or more, and the hardness of the sample is obtained from the load and indentation depth data of two sets. Since the increase in load is stopped and the indentation depth is measured, stable measured values are obtained, and static hardness can be measured.

[0008]

FIG. 1 is a block diagram showing the configuration of an indentation hardness tester for carrying out the test method of the present invention, in which an indenter 2 is formed by electromagnetic force generating means constituting load means.
Is pushed into the sample 1, and the displacement amount of the indenter 2 is detected by the differential transformer type displacement detector 3. That is,
A load signal is output from the CPU 15, a load current is supplied to the electromagnetic force generating means 4 via the D / A converter 6 and the current amplifier 5, and the indenter 2 is moved to the sample 1 by the driving force of the electromagnetic force generating means 4.
Push into. The load current supplied to the electromagnetic force generating means 4 and the displacement signal from the displacement detector 3 are read out as voltage values, converted into frequency signals by the V / F converters 8 and 9, respectively, and are coefficientd by the counters 10 and 11. The load / displacement data is input to the control unit composed of the CPU 15, RAM 16, and ROM 17. The load / displacement data input to the CPU 15 is stored in the PAM 17, and also processed and output to the CRT 19 via the I / O 18 to store the relationship between the load and the indenter pushing depth.

In the test method according to the present invention, in the indentation hardness tester configured as described above, several load values as measurement points are set in advance for load control after the test is started. When the load value reaches the set load, the increase of the load current to the electromagnetic force generating means 4 is stopped and the set load value is held for a certain period of time. A certain time (for example, 10 to 1) from the time when the set load is reached until the plastic deformation is almost completed.
Measure the indentation depth of the indenter at 5 seconds). The indentation depth is measured as described above for each set load value, and the hardness of the sample is calculated from the two sets of load and indentation depth data.

FIG. 2 is a diagram showing the load-indentation depth characteristics obtained by the test method according to the present invention. The load increase is stopped for a certain period of time at the set loads P1, P2, Pmax, and the plasticity is increased. It shows that the indentation depth is measured after the deformation is almost completed.

Since the test method according to the present invention measures the indentation depth by stopping the increase of the load as described above, a stable measurement value can be obtained. Also, since the hardness is calculated from the two sets of load and indentation depth obtained by measuring the indentation depth while the plastic deformation is almost completed while holding the set value for a certain period of time, the static hardness of the sample should be calculated. You can Since the indenter is not measured at the time when the indenter contacts the sample surface, the detection of such contact point becomes unnecessary, and the measurement error due to the influence of the indenter tip shape, sample surface roughness, etc. does not occur.

[0012]

As is apparent from the above description, according to the indentation hardness test method of the present invention, a stable measurement value can be obtained without causing a measurement error due to the detection of the contact point between the indenter and the sample. It became possible to determine the static hardness of the sample.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an indentation hardness tester for carrying out the test method of the present invention.

FIG. 2 is a diagram showing load-indentation depth characteristics obtained by carrying out the test method of the present invention.

FIG. 3 is a diagram showing a load-indentation depth characteristic according to a conventional method.

[Explanation of symbols]

1 ... Sample 2 ... Indenter
3 ... Displacement detector 4 ... Electromagnetic force generating means 15 ... CPU

Claims (1)

[Claims] 1. In an indentation hardness test method for an indenter in which a test load applied to an indenter is continuously and gradually increased while the test load is pushed into the sample surface, when a preset test load is reached, The process of stopping the increase of the test load for a certain period of time until the plastic deformation is almost completed, maintaining the set test load, and measuring the indentation depth of the indenter at the time when this certain period of time elapses twice or more consecutively. The indentation hardness test method is characterized in that the hardness of the sample is calculated from two sets of load and indentation depth data.