What should I do if the grip of the tensile testing machine slips? Rally machine manufacturers solve it for you

Tensile, compressive, bending and shearing tests of various plastics, rubbers, and metal materials, and can also be used for compression tests of non-metallic materials such as plastics, concrete, and cement. Adding simple accessories can complete tape chains, wire ropes, and welding electrodes. , various performance tests of tiles and components. What should I do if the grip of the tensile testing machine slips? The tensile testing machine manufacturer will solve it for you. The general human factor causes the tensile testing machine to slip and the human factor that causes the tensile testing machine to slip is caused by the operator’s failure to operate the test according to the correct method during the test. There are mainly two factors: The specimen gripping length is short and the jaws of the grips are improperly selected. 1. The correct way to use the clamp of the electronic universal testing machine is to use an external force to push the jaws on the clamping surface when the clamping length of the specimen is the same as the length of the tooth surface of the clamp. The initial friction force, and then load the sample through the movement of the beam of the testing machine. When the friction force pulls the jaw (wedge-shaped mouth), due to the action of the inclined plane, the greater the axial tension, the greater the clamping force generated. The electronic universal testing machine clamp Specifically, the wedge-shaped opening with two inclined surfaces is designed to receive uniform compressive stress according to the above-mentioned clamping method. However, some operators did not operate in accordance with the use requirements of the testing machine, the sample clamping length was short, or the sample processing was too short, resulting in uneven force on the inclined surface of the wedge-shaped mouth, and the local stress of the wedge-shaped mouth far exceeded The yield strength of the material, so that the wedge-shaped mouth produces plastic deformation, serious eversion, and causes the wedge-shaped mouth slope to collapse or wear. In this case, the clamp continues to be used, reducing the angle of the wedge-shaped mouth, which deteriorates the stress state of the clamp body and causes slippage. 2. Improper selection of the jaws of the tensile testing machine fixture, indicating that the tensile testing machine jaws have a variety of different specifications and clamping surfaces, and different jaws are used for different samples. Some operators use large-sized jaws during the test. Clamping small cross-section samples, or using flat chucks to clamp large samples, makes the contact between the clamp and the sample not close, and the friction coefficient is significantly reduced. decrease. When the force of the sample gradually increases to a large static friction force, the sample will slip, resulting in false yielding from the surface.

Second, the equipment causes the tensile testing machine to slip The main equipment reasons are that the iron oxide scale falls into the slope of the wedge block when the tensile machine is pulling the sample, which causes slippage. During the drawing process of the metal sample, metal oxide scale is produced, and the iron oxide scale will fall into the inclined surface where the wedge-shaped block and the fixture are combined, so that the flatness of the inclined surface is destroyed and the surface roughness is seriously reduced, which makes the wedge-shaped mouth (wedge-shaped block). ) The movement is inflexible, and when the pulling force is continuously increased, the wedge-shaped block slides along the dovetail slope to produce crawling (jumping). This is how the sound of horns and horns that often occurs during the tensile loading process is produced. This is commonly referred to as slippage. The maintenance knowledge of tensile testing machine fixtures is also very important in our use process, because tensile testing machine fixtures are vulnerable parts, so we should pay attention to such matters before use! Let me popularize the maintenance of tensile testing machine fixtures and other related knowledge. , which can greatly reduce the loss of the fixture. Tensile testing machine fixture product real shot pictures Tensile testing machine fixture maintenance common sense: Before use, check whether the tensile testing machine fixture is firm and capable of clamping work; if the clamping surface is worn, damaged or stained, the clamping surface should be replaced in time; the fixture is under test. After clearing the excess material, it will be prompted so as not to affect the next test; the fixture is stored and properly coated with glycerin to prevent rust; regularly check whether the fixture is damaged; regularly check whether the pressure gauge accurately records the air pressure and oil pressure of the clamping device; the use process Check whether the specimen is properly mounted and clamped. Improper clamping is likely to damage the grips; do not use more clamping force than required.

As long as it can provide a reliable, non-slip fixation; the specimen in the fixture should always be attached to the load cell; preheat the load cell for at least 15 minutes; once the specimen is in place, do not change the balance or Beam position control point; use the load protection function to protect the sample from damage, if the load of the sample is less than the range, please consider using a smaller load cell; the design of the tensile testing machine fixture is mainly based on the test standard of the material and the sample (specifically refers to the shape and material of finished and semi-finished products). These standards generally have strict regulations on sample preparation and test methods, suggesting that we can design different fixtures according to different samples and test methods. For the fixtures used for special samples (finished products and semi-finished products), the fixtures are mainly designed according to the shape and material of the sample. The fixture itself has no fixed structure (for example, the wire can be wound, or two flat plates, and the thin metal plate sample can be wedge-shaped. It can also be clamped), which is obviously different from the host.

Post time: Jul-11-2022
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