Tests for the determination of a series of properties of a material under tensile loading are called tensile tests. Tensile testing is one of the basic methods to test the mechanical properties of materials, and is mainly used to test whether the material conforms to the prescribed standards and the performance of the materials.
Tensile test can be used to determine a series of strength index and plasticity index of the material. Strength usually refers to the ability of the material to resist the elastic deformation, plastic deformation and fracture under the external force. When the material is subjected to tensile load, the phenomenon that the plastic deformation continues to occur when the load does not increase is called yield. The stress produced by yielding, called the yield point or physical yield strength, is expressed in σs (kpa). There are many materials without obvious yielding points in engineering, usually the stress value of the residual plastic deformation of the material is 0.2% as yield strength, the condition yield limit or the condition yield strength, which is expressed in σ 0.2. The maximum stress value of the material before fracture, called tensile strength or strength limit, is indicated by σb (kpa).
Basic types of tensile testing
The type of tensile test will be changed according to different standards, material, force value and other factors to replace the stretching fixture
Peeling ,tearing,adhesion,pull-push force,,,etc
Benefits of tensile Testing
The material strength and plastic performance data obtained by tensile test have important application value and reference value for design and material selection, development of new materials, purchase and acceptance of materials, quality control of products, safety and evaluation of equipment, and some are directly based on the results of tensile test.
Assist in product design and improvement
Reduce material costs
Meet international standards and industry standards
Application of tensile testing
(not limited to the following):
1. Metal, nonmetal
3. medicine, food
4. Wood, copper, aluminum, plastic profiles
5. Wire and cable, paper, film
6. Rubber, textile, aerospace and other industries
Tensile Testing Standards
The criteria for each tensile test will vary depending on the material, area, use of the product, industry, etc.
There are a number of tensile testing standards developed by organizations such as ASTM, BSI, DIN, ISO and MIL.
Commonly used test standards include:
ASTM B913, ASTM D76, ASTM D1876, ASTM D3822, ASTM D412, ASTM D638, ASTM D828, ASTM E8
BS 5G 178, BS EN 1895
ISO 37, ISO 527, ISO 1924, ISO 13934
The tensile test process is divided into 4 phases:
1. The elastic stage (the stress-strain ratio column increases, the unloading load can restore the original state);
2. The yield stage (the increase of strain is greater than the stress, the plastic deformation begins to occur, the lower limit of stress is the yield point).
3. Enhancement stage (strain increase stress also increases, maximum value is limit tensile strength)
4. Necking stage (strain increase stress drop, resulting in "necking" fracture).