The use of electronic universal testing machine in metal, steel and aluminum foil materials

As we all know, during the tensile testing of metal materials,Electronic universal testing machineIt usually goes through four stages: the yield stage, the elastic stage, the strengthening stage, the necking and the fracture stage. Each stage has its inherent mechanical properties, and the following are the four stages.

1. Yield stage When the stress exceeds the elastic limit and reaches the zigzag curve, the test force no longer increases and sometimes decreases. This phenomenon shows that the sample deformation but continues to elongate when the tensile force it bears does not continue to increase or decrease slightly. It is called the yield point of the material. Its stress is called the yield point (yield stress), the force (yield force on Fsu) or the small force (yield force under FsL) regardless of the initial instantaneous effect (no matter where the load first drops), and the corresponding stresses are the upper and lower yield points. The small load displayed by the monitor (small load after the number of drops) is the yield load Fs. In engineering, only the yield point is to be lowered, and yield stress is an important indicator for measuring material strength.

2. Elastic stage In this stage, the tensile force and elongation of the tensile tester are proportional to each other, indicating that the stress and strain of the steel are linear, and they fully follow Hook's law. If the stress continues to increase to point C, the relationship between stress and strain is no longer a linear relationship, but the deformation is still elastic, that is, the deformation completely disappears after the tension is removed. It is an effective indicator to control the work of materials within the range of elastic deformation and has practical value in engineering.

3. Strengthening stage After the yield stage, the internal crystal structure of the sample material is adjusted due to plastic deformation, and its ability to resist deformation is enhanced. As the tension increases, the elongation deformation also increases, and the tensile curve continues to rise. This line segment is called the strengthening stage. As the amount of plastic deformation increases, the mechanical properties of the material change, that is, the deformation resistance of the material increases and the plasticity decreases. Unloading during the reinforcement phase, the elastic deformation will disappear and the plastic deformation will remain. When the tensile force increases and the tensile curve reaches the apex E, the test force at this time is the tensile force Fm. This can obtain the tensile strength of the material, which is also an important indicator of the strength performance of the material.

4. Necking and fracture stages For plastic materials, the deformation of the sample is basically uniform in all parts before bearing the tensile force Fm. After reaching Fm, the deformation is mainly concentrated in a local area of ​​the sample, where the cross-sectional area is sharply reduced. This phenomenon is the "necking" phenomenon. At this time, the tension decreases as it falls until the sample is pulled off, and its fracture shape is bowl-shaped. In the above four stages, it can be clearly seen on the electronic tensile tester-deformation (or stress-strain) curve, and the various mechanical performance parameters of the material can be calculated through the test curve. Test force-displacement curves, deformation-time curves, etc. can also be derived.http://www.hssdtest.com/