Why the LCD universal material testing machine display shows that the yield strength is lower than i

Is the tensile strength accurate? If the tensile strength is not accurate, please re-verify the accuracy of the equipment, if the tensile strength is normal and the yield strength is not accurate, it is recommended to check the following points: 1. Whether the jaws (accessories that are in direct contact with the specimen when clamping the specimen) are damaged, resulting in the slippage of the specimen during the test, and the sawtooth in the curve is more obvious, which is easy to cause misjudgment.

Treatment: replace the jaws); 2. Whether the jaw splint (the accessories where the jaws are placed) can be well matched with the test bench is due to the influence or damage of iron filings and dust, which causes the clamping part to slip during the test, and the sawtooth in the curve is more obvious, which is easy to cause misjudgment. (Processing:.)

If there is no damage to the equipment, only the iron filings and dust, and the living surface is not seriously worn, clean up the dust and apply molybdenum disulfide grease. If the equipment has caused serious damage, the jaw splint can be replaced reliably, and the deformation of the test bench should be repaired. 3. The instrument yield judgment collection point is too sensitive (processing method:

Contact the manufacturer to correct the collection conditions).

Hello: The yield strength test is directly related to whether the yield of the material is obvious, as well as the load sensor and deformation measurement device of the key test equipment you use, as well as the point of the software. I'm sure your material yields not very obviously.

It can be because your universal material testing machine is not accurate, it is recommended to find a calibration measurement institute to calibrate it, if it is not accurate, find a manufacturer to solve it.

First, in the scope of application.

The electronic universal testing machine is widely used in various metals, non-metals and composite materials, such as wood, plastic profiles, wires and cables, paper, film, rubber, medicine, food packaging materials, fabrics, etc. At the same time, various test data processing software and test aids can be customized according to the domestic and international standards provided by users. The digital display electronic universal testing machine is suitable for users who only seek force value, tensile strength, compressive strength and other related data, such as the need to take more complex parameters, microcomputer control electronic universal testing machine is a better choice.

Second, in terms of performance.

The electronic universal testing machine does not use oil source, so it is cleaner and more convenient to use and maintain; Its test speed range can be adjusted, the test speed can reach 500mm, and the test stroke can be determined according to needs, which is more flexible; The force measurement accuracy is high, and some can even be achieved; Small size, light weight, large space, convenient to add corresponding devices to do various material mechanical tests, can achieve a multi-purpose machine.

The hydraulic universal testing machine is limited by the flow rate of the oil source, and the test speed is low. Manual hydraulic universal testing machine, the operation is relatively simple, cheap, but the control accuracy is low; The electro-hydraulic servo universal testing machine is not inferior to the performance of the portal digital display electronic universal testing machine, in addition to the low speed, the control accuracy is not inferior; The microcomputer-controlled electro-hydraulic servo universal testing machine using load sensor can also reach about the force accuracy, and it is more reliable, more stable and more cost-effective when doing large-tonnage material mechanical tests.

The electronic universal testing machine mainly uses the servo motor as the power source, and the lead screw and the wire mother as the executive components to realize the speed control of the moving beam of the testing machine. In terms of transmission control, there are two main forms, synchronous belt and reducer; In terms of force measurement, the electronic universal testing machine uses load sensors.

Third, in terms of structural characteristics.

The hydraulic universal testing machine mainly uses high-pressure hydraulic power as the power source, and adopts manual valve, servo valve or proportional valve as the control element for control. The ordinary hydraulic universal testing machine can only be manually loaded, which belongs to the open-loop control system, and is affected by the most advanced factors, and the load sensor generally adopts the hydraulic pressure sensor. The electro-hydraulic servo universal testing machine is controlled by servo valve or proportional valve as a control element, and some domestic manufacturers have also used high-precision load sensors to measure force.

Fourth, in terms of cost performance.

The following electronic universal testing machines are more advantageous. The hydraulic universal testing machine is mainly used for the tensile, compression, bending and other mechanical properties tests of metallic and non-metallic materials and parts, components and components. Hydraulic universal testing machine is an ideal test equipment for industrial and mining enterprises, building materials, quality inspection centers, water conservancy and hydropower, bridge engineering, scientific research institutes, and mechanical laboratories of colleges and universities.

Manually controlled hydraulic universal testing machine, suitable for finished product inspection and material index testing of industrial and mining enterprises; The electro-hydraulic servo universal testing machine is suitable for laboratories, scientific research institutions and colleges and universities with high requirements for steel and building materials testing.

Yield strength is the lowest stress value, the lower yield limit, when a material begins to undergo significant plastic deformation.

(1) Ordinary test items: (ordinary display value and calculated value).

Tensile stress Tensile strength.

Tear strength Elongation at break.

Constant Elongation Stress Constant stress elongation.

Constant stress force value Tear strength.

Force value at any point Elongation at any point.

Extraction force, adhesion and calculated value of the peak.

Pressure test Shear peel force test.

Flexure test: Pull-out force, puncture force test.

2) Special test items:

1.The elastic coefficient is the Young's modulus of elasticity.

Definition: The ratio of the normal stress component in the same phase to the normal strain. In order to determine the coefficient of stiffness of the material, the higher its value, the stronger the material.

2.Proportional limit: The load can maintain a proportional relationship with the elongation within a certain range, and its maximum stress is the proportional limit.

3.Elastic limit: The maximum stress that the material can withstand without permanent deformation.

4.Elastic deformation: After the load is removed, the deformation of the material disappears completely.

5.Permanent deformation: After the load is removed, the material remains deformed.

6.Yield point: When the material is stretched, the deformation increases faster and the stress does not change, which is the yield point.

The yield point is divided into upper and lower yield points, and the upper yield point is generally used as the yield point. Yield: The load is no longer proportional to the elongation when it exceeds the proportional limit, and the load will drop suddenly, and then over a period of time, it will rise and fall, and the elongation will change greatly, which is called yield.

7.Yield strength: When stretching, the load of a certain specified value when the permanent elongation rate reaches a specified value, divided by the area of the original section of the parallel part, the quotient obtained.

8.Spring k-value: The ratio of the force component in phase with the deformation to the deformation.

9.Effective elasticity and hysteresis loss: On the universal materials testing machine, when the sample is stretched to a certain elongation or stretched to a specified load at a certain speed, the percentage of the ratio of the work recovered when the sample shrinks and the work consumed during stretching is determined, which is the effective elasticity; Determine the percentage of the ratio of energy lost during elongation and contraction of the sample to the work consumed during elongation, which is the hysteresis loss.

Tensile strength of tensile testing machine:

The ratio of the ultimate tensile load to the cross-sectional area of the experimental material is the tensile strength.

Tensile testing machine yield strength:

Yield strength is only for materials that are elastic, and inelastic materials do not have yield strength.

In the tensile testing machine test, the difference between yield strength and tensile strength is as follows:

1. Tensile strength in tensile testing machine.

When the steel yields to a certain extent, due to the rearrangement of the internal grains, its ability to resist deformation is increased again, and although the deformation develops rapidly, it can only increase with the increase of stress until the stress reaches the maximum. After that, the ability of the steel to resist deformation is significantly reduced, and a large plastic deformation occurs at the weakest point, where the cross-section of the specimen shrinks rapidly, and the necking phenomenon occurs until fracture failure. The maximum stress value of the steel before it is tensile fractured is called the strength limit or tensile strength.

2. Yield strength in tensile testing machine.

When the stress exceeds the elastic limit, the deformation increases rapidly, and in addition to the elastic deformation, part of the plastic deformation is also generated. When the stress reaches point b, the plastic emergency increases dramatically, and a small platform of fluctuations appears in the curve, which is called yielding. The maximum and minimum stresses at this stage are called the upper and lower yield points, respectively.

Since the value of the lower yield point is relatively stable, it is used as an indicator of the resistance of the material, which is called the yield point or yield strength.

The tensile testing machine is also known as the universal material testing machine. Universal testing machine is used for various materials for the static load, tensile, compression, bending, shearing, tearing, peeling and other mechanical properties of the mechanical properties of the testing machine for mechanical afterburner testing machine, suitable for plastic plates, pipes, profiles, plastic film and rubber, wires and cables, steel, glass fiber and other materials of various physical and mechanical properties testing for material development, for physical property testing, teaching and research, quality control and other indispensable testing equipment, tensile machine fixture as an important part of the instrument, Different materials require different fixtures, which is also an important factor in whether the test can be carried out smoothly and the accuracy of the test results.

Tensile strength is the force divided by the cross-sectional area, and yield strength is the upper and lower yield forces divided by the cross-sectional area

The force value that is already in the range of the tensile length but is not broken is the yield strength, and the maximum force value of the tensile strength during the tensile process is called the tensile strength.

Look at the metal materials themselves, such as cast iron, gray iron is not yielded, and materials such as steel bars and cast steel are obviously yielded, and some materials are exceptions, such as alloy steel, aluminum alloy, etc., the yield of these high-strength stress materials is not obvious, and auxiliary tools are needed to connect to the testing machine to measure the yield strength.

It depends on the material itself, and the material will yield to it

Did the material you tested yield.

The yield strength is generally automatically determined by the testing machine according to the force value, and the computerized testing machine generally has this function. Use the checkbox to set whether or not to display.

European standard instrument testing machine expert——

No problem, as long as you use an extensometer.

Did the material you tested have significant yields.