If you want to understand the three aspects of the tensile machine, you must learn

I. Extensometer Type of Tension Machine

The extensometer of the tensile machine is a sensor that senses the deformation of the test piece. The strain gauge type extensometer is currently a widely used type due to its simple principle and convenient installation. Extensometers can be divided into axial extensometers, lateral extensometers, and clip-type extensometers according to the measurement object. Radial extensometer: It is used to detect the radial contraction of standard test specimens. It is used in conjunction with the axial extensometer to determine Poisson's ratio μ. It converts radial deformation (or lateral deformation in a certain direction) into electricity, and then Measure, record, or control another device with a secondary meter.

Clip type extensometer: used to detect crack opening displacement. Clip type extensometer is one of the most commonly used instruments in fracture mechanics experiments, and it is mostly used in the determination of fracture toughness of materials. High precision, easy installation and simple operation. When the test piece breaks, the extensometer can automatically detach from the test piece, which is suitable for static and dynamic deformation measurement.

Axial extensometer: one of the instruments for measuring deformation of various metallic and non-metallic materials.

Various measurement methods of tensile machine

Deformation measurement

Measured by deformation measurement installation, it is used to measure the deformation of the sample during the experimental process.

There are two chucks on this installation. The material testing machine is connected with a photoelectric encoder installed on the top of the measurement installation through a series of biographical ideas. When the interval between the two chucks breaks, the shaft of the photoelectric encoder is twisted. , The photoelectric encoder will have a pulse signal output. Then, the signal is processed by the processor to obtain the deformation amount of the sample.

Measurement of beam displacement

The reason is basically the same as the deformation measurement, and the displacement of the beam is obtained by measuring the output pulse number of the photoelectric encoder.

Calculation of Tensile Machine Strength

Calculation formula:

1. Cross-sectional area of ​​dumbbell-shaped test piece = thickness () × parallel part width ();

2. Tensile machine strength TB (Kg / cm2) = breaking load / section area of ​​test piece;

3. Adhesive strength of tensile machine TF (Kg / c) = peeling load / test piece width;

4. Tear strength of tensile machine TS (Kg / cm2) = maximum load / thickness of test piece;

5. Tensile stress Mn (Kg / cm2) of the tensile machine = load / section area at a specific elongation (where n of Mn represents a specific elongation (%), for example, M300 represents an elongation of 300% Tensile stress).

6, elongation (%) = elongation / original length (gap distance) * 100%;

Sorting method of calculation formula test results:

Number of test results: 4 test strips are specified, but when insufficient, 3 or even 2 can be used. In this case, the number of test strips must be specified.

Test results: tensile strength and elongation: The tensile strength and elongation are arranged in order of the measured value. It is S1, S2, S3, and S4, and is calculated according to the following:

a. When there are 4 test pieces: TB or EB = 0.5S1 + 0.8S2 + 0.1 (S3 + S4)

b. 3 test pieces: TB or EB = 0.7S1 + 0.2S2 + 0.1S3

c. Two test pieces: TB or EB = 0.9S1 + 0.1S2

Stress resistance: The tensile stress is expressed by the average of the measured values.

Records: On the test result form, the following items must be recorded:

A. Tensile strength (Kg / cm2), elongation (%), tensile stress (Kg / cm2).

B. Capability (capacity) of the test machine.

C. Shape and number of test piece.

D. Test temperature

E. Other necessary matters.