Measuring and testing – Hardness – By penetrator or indentor
Reexamination Certificate
1999-03-26
2001-08-28
Raevis, Robert (Department: 2856)
Measuring and testing
Hardness
By penetrator or indentor
Reexamination Certificate
active
06279388
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for calibrating a hardness tester, a method for calibrating the apparatus and a hardness tester and an apparatus for evaluating a dynamic characteristic of a specimen.
2. Description of Related Art
Generally, hardness evaluation, that is, a hardness test for a specimen by a hardness tester is carried out by measuring a force applied to the specimen and a deformed amount of the specimen with applying the force.
With the hardness test for a specimen, static characteristic evaluation, that is, a static test, and dynamic characteristic evaluation, that is, a dynamic test are included. With the static characteristic evaluation, a force is applied to a specimen, then a deformation thereof is ended, thereafter a deformed amount of the specimen is measured. Then, the relation between the force and the deformed amount of the specimen is evaluated.
On the other hand, with the dynamic characteristic evaluation, when a specimen is deforming gradually by output forces, that is, applied forces from the hardness tester, it is evaluated that the relation between the forces applied to the specimen at each point and deformed amounts of the specimen at each point.
However, according to a conventional hardness tester, it is not possible to carry out the dynamic test but to carry out only the static test.
Next, a calibration for the hardness tester will be explained. As shown in
FIG. 20
, a force meter
202
and a dial master gage
203
are incorporated in series in a hardness tester
1
. When a test force is applied, the test force is measured by the force meter
202
, a displacement is measured by the dial master gage
203
, and an indicated value on a displacement gage
4
which is incorporated in the hardness tester
1
is read.
The operation is repeated for several times by changing the test forces. The indicated values on the dial master gage
203
and the displacement gage
4
with each test force are filled in a measurement data chart
205
, so that the hardness tester is calibrated based on the values filled in the measurement data chart
205
.
The calibration above-described is the static test. Therefore, there is a problem that for carrying out the dynamic test, it is required to carry out the static test for several times by changing the test forces.
SUMMARY OF THE INVENTION
The present invention was developed in view of the above-described problems. Therefore, an object of the present invention is to provide a method for calibrating an apparatus for calibrating a hardness tester, which can prevent causing error with a dynamic test, which occurs by hysteresis of the force(load) measuring member and repeating with the dynamic test. An another object of the present invention is to provide an apparatus for calibrating a hardness tester, which can statically and dynamically evaluate test forces and deformed amounts of a specimen according to the applied test forces, which are required to calibrate the hardness tester. A further object of the present invention is to provide an apparatus for evaluating a dynamic characteristic of a specimen, which can evaluate a dynamic characteristic of a specimen.
In order to accomplish the above-described objects, in one aspect of the present invention, a method for calibrating an apparatus for calibrating a hardness tester, the method comprises the steps of: setting a plurality of calibration points between a rated force point at which a rated force of a force(load) measuring member is applied and a zero point at which no-load is applied, for measuring outputs (mV/V) from the force measuring member according to test forces(N) applied to the force measuring member; and calculating a relation between the test forces(N) and the outputs(mV/V) as an approximation based on the test forces(N) and the outputs(mV/V) according to the test forces(N) at the calibration points.
The calibration points can be set between the rated force point and the zero point to have same intervals each other.
For the hardness tester, the Rockwell hardness tester, the Vickers hardness tester, the Brinell hardness tester or the like can be applied, however, another tester which can apply a desired force to a force(load) transmitting portion can be applied.
For the force measuring member, a load cell can be usually employed, however, another member which can measure the force applied thereto can be employed.
At the rated force point, for example, when the rating of the force measuring member is 2 kN, the test force of 2 kN is applied to the force measuring member.
According to the calibrating method of the invention, the apparatus for calibrating a hardness tester is installed in the commercial hardness tester, so that it is possible to calibrate the apparatus in the same way as that of the ordinary hardness test.
Further, in addition to the rated force point and the zero point, because it can be set a number of calibration points between them, it can be possible to prevent causing error with a dynamic test, which occurs by hysteresis of the force measuring member and by repeating with the dynamic test.
In accordance with another aspect of the present invention, an apparatus for calibrating a hardness tester, which installed in a hardness tester, the apparatus comprises: a bottom frame to be mounted to the hardness tester; a force(load) measuring member disposed on an inner surface of the bottom frame; a force(load) transmitting portion which is movable up and down; a distance measuring member incorporated in the force transmitting portion to be contacted with the force measuring member from above; and a dummy indenter disposed to project in an upper end portion of the force transmitting portion to be inserted into a mounting hole for an indenter of the hardness tester. The force transmitting portion can be supported by a supporting means.
The bottom frame can have, for example, a U-like shape in cross-section and be mounted to a mounting portion for an anvil of the hardness tester. The hardness tester can be the one above-described. For the force measuring member, a load cell can be usually employed, however, another member which can continuously measure the forces applied thereto can be employed. The distance measuring member can be, for example, a laser displacement meter which continuously measures a distance between a fixed point of the laser displacement meter and a point of the force transmitting portion. Deformed amounts of the force measuring member can be measured as the distance. For the supporting means, for example, a plurality of pillars mounted to the bottom frame can be applied. However, it is not limited to them, for example, an air bearing which supports a position of an axis by applying air at a constant pressure between the axis and a cylinder, or the like can be applied. With the air bearing, a friction drag which the axis received can be extremely small.
According to the apparatus of the invention, because it is possible to continuous measure the forces and deformed amounts of the force measuring member according to the applied test forces, it is possible to evaluate the dynamic characteristic of the force measuring member. Further, it is possible to easily install the apparatus to the mounting portion for the anvil of the tester, and the dummy indenter is inserted into the mounting hole for an indenter of the tester at the time, it is also possible to certainly mount the apparatus to the tester.
The apparatus can further comprise a preload member to press the force measuring member through the force transmitting portion. The preload member can, for example, comprise a clamping screw, a plate-like member, axes or the like. The clamping screw can be connected to the force transmitting portion through the plate-like member, so that when the clamping screw is clamped, it can be possible to apply a predefined force to the force measuring member through the force transmitting portion.
According to the apparatus, because the force measuring member can be pressed by the
Koshimizu Fumihiko
Tsujii Masaharu
Akashi Corporation
Oliff & Berridge PLC.
Raevis Robert
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