As the core equipment for testing the mechanical properties of materials, the measurement accuracy of the universal testing machine depends not only on the host sensor, but also on the performance of the fixture. As a key component connecting the testing machine and the specimen, the fixture directly determines the accuracy of force transmission and the stability of the testing process, and is the "first line of defense" to ensure the reliability of test data.

From the perspective of functional adaptation, fixtures can be divided into tension, compression, bending, shear and other types, and each type needs to match specific test standards and sample characteristics. In the stretching fixture, the flat jaw fixture is suitable for flat specimens such as metal sheets and plastic films, and avoids specimen slippage by increasing the contact area; The wedge-shaped fixture relies on the principle of inclined self-locking, which can stably clamp irregular shaped specimens such as round bars and wires, especially suitable for high-strength material testing. Compression fixtures often use rigid flat plate structures, with some equipped with spherical pair designs, which can automatically adjust the sample's neutrality and reduce testing errors caused by uneven force distribution.

Material and craftsmanship are the core guarantees of fixture performance. High quality fixture bodies are mostly made of 40CrNiMoA alloy structural steel, which can reach a hardness of HRC30-35 after quenching and tempering treatment, ensuring sufficient rigidity and avoiding brittle fracture. The treatment of the clamping surface is particularly critical, as coarse anti slip patterns are suitable for metal specimens, while rubber coatings can prevent surface damage when clamping non-metallic specimens. The parallelism of the clamping surface of high-precision fixtures should be controlled within 0.02mm/m to ensure uniform transmission of force values.

When selecting, it is necessary to comprehensively consider the sample material, test type, and standard requirements. For high-temperature testing, high-temperature resistant alloy fixtures should be selected and equipped with cooling systems; The dynamic fatigue test requires the fixture to have good shock absorption performance. In addition, the adjustment range of the opening degree of the fixture should match the size of the sample, and the quick mold changing structure can greatly improve the efficiency of multi batch testing.

As a precise gripper for force testing, the performance of the fixture directly affects the credibility of the test results. Valuing the rational selection and regular calibration of fixtures is essential to fully utilize the testing capabilities of universal testing machines and provide reliable data support for material research and quality control.