Tensile strength and elongation at break testing.
Tensile strength and elongation at break are one of the important indicators to evaluate the mechanical properties of materials, which can reflect the resistance and deformation ability of materials under external force. This article will introduce in detail the testing methods, principles, influencing factors and significance of tensile strength and elongation at break in practical application.
1. Detection method.
1.Tensile strength testing.
Tensile strength refers to the maximum stress that a material can withstand when subjected to a tensile force, usually denoted by b. The detection method is to fix the specimen on the testing machine, stretch the specimen until it breaks, and record the maximum load fb and the original cross-sectional area so, which is calculated as: b=fb so.
2.Elongation at break detection.
Elongation at break refers to the ratio of the maximum deformation of a material to its original length when subjected to tensile forces, and is usually expressed by . The detection method is similar to the tensile strength, which is to fix the specimen on the testing machine, and record the original length lo and the maximum load fb after stretching to fracture, and the calculation formula is: =(lm-lo) lo. where lm is the length of the specimen after pull-off.
Second, the principle. 1.Tensile strength.
The magnitude of tensile strength depends on factors such as the internal structure of the material, its chemical composition, the state of heat treatment, and the shape of the specimen. When the material is subjected to tensile force, stress is generated internally, and when the stress exceeds the yield point of the material, the material will undergo yield deformation, and as the stress increases, the material will undergo plastic deformation until fracture.
2.Elongation at break.
The magnitude of the elongation at break is related to factors such as the elastic modulus of the material, the Poisson's ratio, and the original length of the specimen. When the material is subjected to tensile forces, it will deform in both the axial and transverse directions, where the axial deformation is the elongation, and the transverse deformation will cause the specimen width to decrease. When a material breaks down, its elongation reaches its maximum.
3. Influencing factors.
1.Tensile strength.
The factors affecting tensile strength mainly include the composition of the material, the microstructure, the heat treatment state, and the shape and size of the specimen. For example, carbon steel has an increase in tensile strength after quenching and tempering. In addition, the cross-sectional shape, surface roughness, and work hardening of the specimen also have an impact on tensile strength.
2.Elongation at break.
The factors affecting the elongation at break mainly include the elastic modulus of the material, the Poisson's ratio, the heat treatment state, and the original length of the sample. For example, low carbon steel has a different Poisson's ratio than medium carbon steel, so its elongation at break will also vary. In addition, the surface roughness, temperature, and strain rate of the specimen also have an impact on the elongation at break.
Fourth, practical application.
1.Quality control.
Through the detection of tensile strength and elongation at break, we can understand whether the mechanical properties of the material meet the requirements of product design, so as to play a guiding role in the quality control in the production process. For example, in the production process, the mechanical properties of the product can be improved by adjusting the process parameters, optimizing the material composition, etc.
2.R&D of new materials.
Through the detection of tensile strength and elongation at break, the mechanical properties of new materials can be understood, which provides experimental basis for the research and development of new materials. For example, in the research and development process of new materials, materials with excellent mechanical properties can be obtained by constantly adjusting the composition and preparation process of the materials.
In summary, the detection of tensile strength and elongation at break is of great significance for the research, production and application of materials. Through the understanding and mastery of tensile strength and elongation at break, it can provide strong support for the optimal design and safe use of materials.