Tensile testing machine is a mechanical force testing machine, used to test the mechanical properties of materials such as static load, tension, compression, bending, shearing and peeling. It is suitable for testing various physical and mechanical properties of plastic sheets, pipes, profiles, plastic films, rubber, wires and cables, etc. It is an indispensable testing equipment for physical performance testing, teaching research, quality control, etc. As an important part of the instrument, Kejian tensile machine fixture requires different fixtures for different materials.
Features of Fixtures
We know that the test force that the fixture can withstand when clamping the sample (or product) and applying force to the sample is a very important indicator of the fixture. It determines the size of the fixture structure and the labor intensity of fixture operation. The sample material is divided into metal and non-metal, and the shape is divided into size. The material composition is diverse, and the test force that the sample can withstand can be as small as tens of millimeters of cattle (such as spandex yarn for textiles) as large as tens of tons (such as ordinary steel, etc.). The test force of large electronic testing machine is 600KN, grade 0.5 machine), the sample size is as small as that of gold wire with a diameter of φ0.006mm, PVC pipe with a diameter of 1m, etc. Therefore, it is necessary to select and design different fixtures according to different test forces and sample shapes and sizes.
Fixture Material Requirements
①For general metal and non-metal samples, the jaws of the fixture are in direct contact with the sample. Generally, alloy structural steel, alloy high-carbon steel (or low-carbon alloy steel) and cold-worked die steel are selected, and appropriate heat treatment processes (quenching and tempering, Carburizing and quenching, etc.) increase its strength and wear resistance.). Sometimes special steel is inlaid at the jaws, or gold steel sand is sprayed on the surface of the jaws.
②. For some jigs with small test force, the surface in contact with the sample is made of sticky soft rubber, etc. (For example, the clamping surface of plastic film, fiber wire and other samples).
(3) The fixture body is generally made of medium carbon steel and alloy structural steel, and its mechanical properties are increased by appropriate heat treatment process. Sometimes aluminum alloys, special metals and non-ferrous metals are used to reduce weight. Sometimes cast structures (cast steel, cast aluminum, etc.)
Fixture structure requirements
(1) Fixture design is mainly based on material test standards and sample types and materials (especially finished and semi-finished products). The above test standards refer to ISO, ASTM, DIN, GB, BS, JIS standards, etc. As well as enterprise standards, industry standards, etc. These standards generally have strict regulations on sample preparation and test methods. We can design different fixtures according to different samples and test methods. For the fixtures used for special samples (finished and semi-finished products), the fixtures are mainly designed according to the type and material of the sample.
(2) The clamp itself has no fixed structure (for example, the metal wire can be clamped by winding or two flat plates, and the metal sheet sample can be clamped by wedge or double clamps), which is obviously different from the host. There are great differences between domestic and foreign hosts, foreign and domestic fixtures are also very different, and there are also great differences between different companies. This mainly depends on the overall level of the company and the accumulated experience of designers. Foreign fixtures, such as INSTRON, MTS, ZWICK, etc. Generally, the workmanship is fine, the availability is high, but the price is high, they are in the market; and our fixtures, because they involve a wide range of industries and have a large domestic market share, can replace some foreign fixtures to a certain extent and are in the middle market. However, for some fixtures of new materials and special materials, there is still a certain gap between domestic and foreign levels.
(3) The clamp itself is a locking mechanism. The mechanical locking structure we know is: thread (I. e. screw, nut), inclined plane, eccentric wheel, lever, etc. The fixture is a combination of these structures.
The fixture structure used in the testing machine has no fixed pattern, which varies greatly according to different samples and test forces. (The sample with large test force generally adopts inclined clamping structure. With the increase of test force, the clamping force increases, and the shoulder sample adopts suspension structure, etc.), If the fixture is divided by structure, it can be divided。
Wedge Fixture (Tilt Locking Principle Fixture)
Fixture of Double-sided (Single-sided or Double-sided Top Wire Principle Fixture)
Winding Fixture (Fixture Where The Sample Is Locked By Winding)
Eccentric Fixture (Eccentric Locking Principle Fixture)
90 Degree Stripping Fixture (Refers To The Fixture Suitable For Vertical Stripping Of Two Samples)
The structure of these fixture has its own advantages and disadvantages. For example, the initial clamping force of wedge fixture is small and increases with the test force. The clamping force increases accordingly。
Contact Person: Miss. Silivia Zhang