Selection method of electronic tensile testing machine fixture
Jiangsu Zhongyi Tools and Riggings Co., Ltd. , https://www.zy-rigging.com
Electronic Tensile Testing Machine Fixtures:
When it comes to electronic tensile testing machines, the fixture is an essential component that is often overlooked. Many people are curious about what a fixture actually is and how it functions. In this article, we’ll explore the different types of fixtures, their purposes, and why they’re so important in material testing.
Fixtures are designed based on the specific test method being used. Common types include tensile clamps, compression clamps, bending fixtures, peel fixtures, shear fixtures, and more. Among these, tensile clamps are by far the most commonly used, making up around 80% of all fixtures. These components play a crucial role in ensuring accurate and reliable test results.
One of the key factors in fixture design is the test force they can handle. This determines the size, strength, and durability of the fixture. Materials tested range from very small samples like gold wires (as thin as 0.006mm) to large structures such as PVC pipes with a diameter of up to 1 meter. The force applied during testing can vary widely, from just a few centimeters of tension (like for textiles) to several tons, especially for metals like steel.
To accommodate these differences, fixtures must be tailored to both the material and the test requirements. For example, metal samples often require high-strength materials like alloy steels or cold work die steels, which are heat-treated to improve wear resistance. In some cases, special coatings or surface treatments, such as gold sand blasting, are used to enhance grip without damaging the sample.
For low-force applications, such as testing plastic films or fiber yarns, soft rubber surfaces may be used to prevent damage. The body of the fixture itself is usually made from medium carbon steel or alloy structural steel, with heat treatment to increase mechanical properties. In some cases, lightweight materials like aluminum alloys are used to reduce overall weight, while cast structures (such as cast iron or aluminum) are employed when needed.
The structure of the fixture is also highly variable. It depends on the shape, size, and material of the specimen, as well as the relevant test standards—such as ISO, ASTM, DIN, GB, and others. Some fixtures are designed specifically for finished or semi-finished products, requiring custom designs to match the exact dimensions and properties of the sample.
There are various types of locking mechanisms used in fixtures, including threaded, wedge-shaped, eccentric, lever, and bolt-based systems. Each has its own advantages and limitations. For instance, wedge clamps provide increasing clamping force as the test force increases, while screw-type clamps offer strong initial grip but may loosen under high stress.
Looking at the current trends, the development of testing equipment is shifting from testing raw samples to evaluating finished or semi-finished products. This requires more specialized fixtures that can adapt to real-world conditions. Additionally, there's a growing demand for automated and efficient clamping systems, moving away from traditional mechanical methods toward pneumatic or hydraulic solutions.
Fully automatic fixtures are now available that can measure the sample, clamp it, perform the test, and generate a report—all in one go. These are ideal for mass production environments where speed and consistency are key. However, they come at a higher cost and are typically used for repetitive testing of similar samples.
Environmental testing is also driving the need for specialized fixtures. High-temperature and low-temperature tests require fixtures that can withstand extreme conditions while maintaining accuracy. These are more complex to design and often have strict size and performance constraints due to limited machine stroke in environmental chambers.
Moreover, the trend toward multi-functional fixtures is increasing. Instead of using separate tools for tension and compression, modern fixtures are designed to handle multiple test types in a single setup. This improves efficiency, especially when testing finished products that require both stretching and compressing.
In emerging industries, new demands are shaping the future of fixtures. For example, medical and aerospace sectors require compact, non-magnetic, and corrosion-resistant fixtures. These innovations reflect the evolving needs of science and technology, pushing the boundaries of what testing equipment can achieve.
In summary, fixtures are more than just accessories—they are critical components that ensure the accuracy and reliability of material testing. As technology advances, so too do the designs and capabilities of these essential tools.