The ability of a material to resist deformation or failure under the action of external forces is known as its mechanical properties. These include strength, plasticity, elasticity, brittleness, fracture toughness, and hardness. Enterprises typically conduct mechanical property tests, as well as physical and chemical tests.
Common mechanical property tests performed on samples include tensile, compression, bending, shear, torsion, impact, fatigue, creep, stress-rupture, stress relaxation, wear, and hardness tests.
Tensile Test
Also known as a tension test, this is typically performed using a universal testing machine or a dedicated tensile testing machine. The process involves slowly applying a load to both ends of the specimen, subjecting its gauge section to axial tension and causing it to elongate along the axis until fracture occurs. Tensile testing allows for the determination of properties such as tensile strength and plasticity. Tensile specimens must comply with relevant national or industry standards specific to the material being tested. The results are typically represented by a stress-strain curve.
The tensile curve consists of four stages: 1. Stage O-a-b (Elastic deformation): Point 'a' corresponds to the proportional limit load ($P_p$); point 'b' corresponds to the elastic limit load ($P_e$, the maximum resistance without permanent deformation). In the O-a section, elongation ($\Delta L$) is directly proportional to the load ($P$), forming a linear segment; the a-b section involves negligible plastic deformation (0.001–0.005%). 2. Stage b-c-d (Yield deformation): Point 'c' is the yield point ($P_s$), and the c-d section forms a wave-like "platform." 3. Stage d-B (Uniform plastic deformation): Point 'B' corresponds to the ultimate tensile load ($P_b$, the maximum load the material can withstand). 4. Stage B-K (Localized deformation/necking): Point 'K' is the fracture point, corresponding to the fracture load ($P_k$).
Compression Test
In contrast to the tensile test, this test measures properties such as compressive strength, relative shortening, and the rate of cross-sectional area increase under static compressive force. A fundamental requirement for compression specimens is that the two bearing end faces must be parallel to each other. Universal testing machines or compression testing machines are typically used for this test. Bending Test
Primarily used to determine the ultimate bending strength, modulus of elasticity, and maximum deflection of materials or structural components. It can be categorized into simply supported beam bending tests and pure bending tests.
Shear Test
Primarily used to determine a material's shear resistance; it is commonly employed to evaluate the quality of wire stock intended for rivets. Shear tests are classified into single-shear and double-shear tests and are conducted using a universal testing machine.
Impact Test
Determines the toughness or brittleness of a specimen by measuring the difference in energy before and after a pendulum strikes it. Characteristics include high impact force, short duration of action, and rapid change.
Hardness Test
A rapid and economical mechanical testing method; it is one of the most widely used techniques for determining material mechanical properties and is the only test that does not compromise the mechanical integrity of the specimen. Other tests conducted during product inspection include torsion, fatigue, creep, relaxation, and stress-rupture tests.