Material mechanics test

Significance of tensile test

Any engineering material will deform when it is stressed. The deformation process can be divided into three basic stages: elastic deformation, plastic deformation and finally fracture. Elasticity refers to the nature of a solid material that changes its shape and size under external forces, but returns to its original state when the force is removed. Plasticity refers to the property that the shape and size of a solid material will change permanently when it is subjected to an external force exceeding a certain value. The fracture is the final result of the deformation of the solid material under external force, that is, the crack caused by the deformation of the solid material and the crack expands to a certain critical value.

Static tensile test is a relatively simple test of mechanical properties. It can clearly reflect the basic characteristics of elastic, elastoplastic and fracture three deformation stages after the material is stressed. The static tensile test is stable and reliable for the measurement of the tested mechanical properties, and the theoretical calculation is convenient. Therefore, various countries and international organizations have developed perfect tensile test method standards, and tensile test methods are listed as the most basic and important test items in mechanical properties tests.

The mechanical properties obtained from the tensile test include strength indexes such as specified non-proportional extension strength, yield strength, tensile strength, plastic indexes such as elongation after fracture and section shrinkage, mechanical constants such as elastic modulus and Poisson ratio, and parameters characterizing the deformation hardening law of the material. The testing of these mechanical property parameters provides a technical basis for material inspection, structural strength design, selection of engineering materials, plastic forming theory and processing technology. Therefore, static tensile test is one of the most widely used mechanical properties test methods in engineering.

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