Various mechanical performance criteria of metal materials are determined through different mechanical tests. The properties displayed by metals under the action of force, which are related to elasticity and non-elasticity as well as related to stress-strain, all belong to the mechanical properties of metals. In the process of developing and improving new materials, improving material quality, designing and using metal parts, mechanical properties are the most important performance indicators and indispensable inspection items in the performance inspection of metal plastic processing products.

Mechanical property tests generally include tensile test, shear test, compression test, bending test, impact test, hardness test, stress relaxation test, and fatigue test. Among them, stress relaxation test and fatigue test do not fall under the routine mechanical property inspections of materials.

The tensile test is a test conducted on a tensile testing machine using a static tensile force to stretch the specimen axially. It measures the force and the corresponding elongation (generally up to the point of fracture), and determines its corresponding mechanical properties. The tensile test is the most fundamental and classic test method in mechanical property tests. The tensile test is mostly carried out at room temperature, except for the tensile performance tests for steels used at high temperatures, which need to be conducted at high temperatures.

The impact test is a dynamic mechanical test. A sample of a certain shape is subjected to tension, torsion or bending to cause it to break rapidly, and the work of breaking it, denoted as Ak, is measured. This is called impact energy. Generally, the impact test is used to test the toughness of materials, so it is also called the impact toughness test. The commonly used test method is the bending impact test. The bending impact test can be divided into beam-type and crossbeam-type. The samples are classified by the shape of the notch into three types: V-shaped, U-shaped and keyhole-shaped. The crossbeam-type impact test can be conducted at different temperatures and is the most widely used type of impact test method.

Bending test In engineering and construction, many components and parts operate under bending loads, such as the crossbeams of bridge cranes, the axles of trains, and cable trays, etc. It is necessary to evaluate the bending performance of the materials of these parts or components. Therefore, the bending mechanical properties are also a commonly used metal property test method in production.

The shear test measures the resistance performance of materials under shear force, and is one of the basic test methods for material mechanical properties. It is mainly used to test parts and materials subjected to shear loads, such as rivets on boilers and bridges, and pins on machines. The shear test is conducted on a universal testing machine, with the sample placed on the shear fixture. There are two loading forms: single shear and double shear. The sample is cut under the action of shear load P.

The compression test is a method for determining the stress-strain relationship of materials under static pressure. For brittle materials, the stress-strain relationship under pressure does not follow Hooke's law. The force per unit area at the point of crushing is the compressive strength. When a pipe ring is compressed, the bending strength of the pipe ring is calculated based on the size of the pipe ring and the load at the time of its crushing.

The hardness test is a method in which the indenter is pressed into the surface of the material under a specified test force, and the hardness is evaluated by the depth of the indentation or the area of the indentation. According to the shape of the indenter, hardness tests include Brinell hardness test, Rockwell hardness test, Vickers hardness test, and Shore hardness test, etc. The hardness test method is simple and easy to perform. In some cases, it can even be regarded as a non-destructive inspection. When the sample size is very small, it can to some extent represent other mechanical property tests and provide valuable reference data.

Stress relaxation refers to the process of measuring the relationship between stress and time on a sample as it remains at a constant initial deformation or displacement at a specified temperature. Stress relaxation tests are divided into tensile stress relaxation tests and bending stress relaxation tests. The former is used for the inspection of rod and wire products, while the latter is used for the inspection of pipe products, such as heat-treated reinforcing bars for prestressed concrete and steel wire ropes, etc.

The fatigue test is a method for testing the fatigue strength, fatigue limit or fatigue life of a metal sample by subjecting it to a constant load amplitude of a certain type of cyclic stress under specific conditions. The fatigue test is conducted on a specialized fatigue testing machine. Depending on the different ways the sample is subjected to force, fatigue tests can be classified as bending fatigue tests, axial (tensile or compressive) fatigue tests, torsional fatigue tests, and composite fatigue tests. Among these, axial fatigue tests are the most commonly used. Fatigue tests are used for the performance research and inspection of materials such as aerospace materials, bearing materials, marine vessel materials, and petrochemical materials.