What is the large deformation gauge?

What is the large deformation gauge distance, before stretching, use a scoring machine or carving knife to mark a distance and measure the length. This is the original gauge. To ensure that the break point is within the marked distance, then carry out a tensile test, after pulling off, put the two sections together, and measure the distance between the two notches again with a ruler.

That is, the post-break gauge distance.

Original gauge distance: A gauge of a certain length selected on a specimen prior to the tensile test.

Post-break gauge distance: The length of the original gauge after the tensile test.

The elongation after break of the material can be calculated through the original gauge distance and the gauge distance after break, which is an important parameter in the performance of the material and is very important in the practical application of the material.

Extended Information: Tensile Test Performance Indicators:

Tensile tests determine a range of strength and plasticity indicators of a material. Strength generally refers to the ability of a material to resist elastic deformation, plastic deformation, and fracture under the action of external forces. When a material is subjected to tensile load, the phenomenon of obvious plastic deformation that continues to occur without increasing the load is called yielding.

The stress at which yield is generated, called the yield point or physical yield strength, is expressed in s (Pa).

There are many materials in engineering that do not have obvious yield points, and the stress value of the residual plastic deformation produced by the material is usually used as the yield strength, which is called the conditional yield limit or conditional yield strength, which is expressed by . The maximum value of stress that a material can reach before it breaks, called tensile strength or strength limit, is expressed in b (Pa).

Plasticity refers to the ability of metal materials to produce plastic deformation without damage under load, and the commonly used plastic indexes are elongation and section shrinkage. Elongation, also known as elongation, refers to the percentage of the ratio of the total elongation length to the original length of the material sample after it is broken by tensile load, which is expressed in δ.

Section shrinkage refers to the percentage of the ratio of the area of the section to the original section area of the material sample after being pulled off by tensile load, which is expressed.

Extensometer is a material that can be equipped with a composite tensile testing machine to measure elongation and deformation.

The deformation measured on the working gauge is more accurate than the deformation measured by the chuck, and the working gauge is measured locally directly, and the force is transformed into a line. The deformation measured by the chuck is the deformation between the specimen fixtures, and the specimen may slip out of the fixture after the test is stressed, or the force close to the grip mouth is not linear, so the measured data is not accurate enough. As shown in the figure below, l0 is the working gauge distance.

European standard instrument testing machine expert——

Steel bar belongs to plastic materials, under the action of external force will produce deformation (part of which is elastic deformation, part of which is plastic deformation), the elastic deformation of the steel bar after the break to return to its original state, and the plastic deformation is permanently maintained, so the original gauge distance of the steel bar must not be the same length after the break, and the gauge distance after the break must be greater than 5 times or even greater than the nominal diameter of the steel bar due to plastic deformation (will vary according to the material of the steel). The plastic deformation is larger than that of HPB (light round rebar), and the plastic deformation of HRB (ribbed rebar) is relatively smaller.

Generally speaking, the steel bar with a large elongation after fracture has a large section shrinkage and relatively low strength.

The original gauge is definitely different from the broken gauge spacing. After breaking, the steel bar is elongated! When measuring the elongation, the length of the elongation is divided by the original gauge length by the same original gauge length. Elongation is only a parameter and has nothing to do with strength, but elongation must meet the requirements of the specification.

It's not the same.

That's about 5 times.

will affect.

The elongation after break of the same metal material is 5d 10d (the short one is larger than the long one) is about twice that of the long one, and the other results (tensile strength, etc.) are almost unchanged.

The scope of use of gauge length is a section of length artificially marked in a tensile test of materials in order to determine some material properties.

l0=original gauge length f0=original specimen cross-sectional area l1=gauge length after fracture f1=cross-sectional area after fracture.

In order to ensure the consistency of the application effect of technical standards in different spaces, it is enough to meet the requirements of technical indicators in the text standards. However, because it needs to be passed in different spaces.

Hello landlord.

According to the previous tests done by others and the introduction of the first metal, the elongation after break of the same metal material is 5d 10d (the short one is larger than the long one) is about twice that of the long one, and the other results (tensile strength, etc.) are almost unchanged.

Why does the universal material machine table need to be raised by 10 mm?

The effect is not significant, but the elongation measured with a 10-day gauge specimen is lower than that measured with a 5-day gauge specimen.

Let the deformation length of the material from plastic deformation to necking be x, and the deformation length of the necking deformation region is l, and the deformation length l of the necking deformation region of the same material is certain, and the plastic deformation length without necking is linear.

Then the elongation of the 5D gauge specimen is (X+L-50) 50*100%, while the elongation of the 10D gauge specimen is (2x+L-100) 100*100%.

This is purely a personal opinion and has no basis. Hope it helps.

Applications:

The automatic extensometer has the characteristics of high accuracy and wide range measurement, and can be applied to tensile tests on metals and plastics. It is possible to measure all strains of the specimen from the elastic segment to the time of break. And it is easily connected to the electronic universal testing machine and the hydraulic testing machine.

The control automatic extensometer is connected to the microcomputer through an RS232 serial port, and under the control of the computer, it is easy to realize the setting and automatic adjustment of the gauge distance, as well as the automatic opening and clamping of the clamping arm. The output of the deformation measurement value is a TTL square-wave digital signal, which is directly connected to the controller of the testing machine, which collects and processes the data in real time.

Feature 1: The resolution can be reached;

2. The unique structural design of the automatic extensometer can track the entire tensile test process, that is, in the elastic deformation and plastic deformation stages, and even until the specimen breaks;

3. The knife edge of the clamping arm is hard, and there are two forms: straight line and arc, which can well meet the clamping needs of plate and bar samples;

4. The rotatable design of the cutter head can avoid damage to the specimen when it is broken;

5. The gauge distance of the automatic extensometer is in the range of 15mm-200mm, which can be automatically adjusted according to the software setting, and has a gauge limit safety protection device;

6. The clamping arm of the measuring part of the automatic extensometer can be automatically clamped or loosened according to the setting of the test, eliminating the operation of manual loading and unloading of the extensometer and the resulting error;

7. Very low measurement drag force;

8. The size of the clamping force can be adjusted manually;

9. Fully comply with ISO 9513, and the accuracy level is graded.

Technical parameters. Relative error of gauge pitch: ;

Resolution: or, take the greater value;

Indication error: when the deformation is in, <; When the deformation is greater than that, it <;

Clamping arm opening distance: 60mm;

Clamping knife edge form: one side straight line, one side arc;

Knife edge clamping force: manually adjustable;

Operating temperature: 10-35;

Specimen size. Maximum specimen thickness: 30mm

Maximum specimen width: 50mm

Maximum specimen diameter: 40mm

Selection: Gauge Pitch Adjustment Range:

100——15~100（mm）

200——15~200（mm）

Deformation Measurement Range:

080——0 ~ 80（mm）

100——0 ~ 100（mm）

The form of the bracket:

Universal currency: This type of extensometer bracket is mounted on the testing machine, and the bracket can be manually adjusted, and when the extensometer is required, the bracket is adjusted to rotate the extensometer to the test area; When the test does not require the use of an extensometer, the bracket is manually adjusted to unscrew the extensometer out of the test area.

e-mail:

At present, the domestic Shenzhen million test equipment.

It has independently developed and produced multi-specification automatic extensometers.

This thing is available abroad, but it is more expensive.