Which indexes are most important in tensile testing
I. The respective definitions of tensile strength and elongation at break
1, tensile strength refers to the maximum uniform plastic deformation of the material stress. In the tensile test, the tensile strength of the sample until the maximum tensile stress to fracture is the tensile strength.
2, elongation at break is expressed as a percentage (%), usually referring to the ratio of the displacement of the sample at the time of fracture to the original length.
Second, the difference between the elongation at break and the tensile rate
The tensile process of the material usually needs to go through a plastic deformation stage, which occurs after the yield point, and fracture occurs after reaching the breaking point. Therefore, elongation at break usually refers to the elongation of the entire process, and elongation is usually just the percentage of elongation at the stage where plastic deformation occurs.
3. Precautions for testing tensile strength and elongation at break
1, the sample length of the tensile test: the longer the length, the greater the probability of weak rings, the lower the strength. Because the strength is not uniform along the length of the fiber, the fiber always breaks at its weakest point. The longer the sample, the greater the probability of the thinnest weak knot, the greater the likelihood of failure, and the strength will decrease
2, the number of samples for tensile test: the more the number of roots, the lower the strength of a single fiber. Because the greater the number of fibers in the bundle, the lower the average single fiber strength calculated from the strength of the bundle, and the average strength is lower than a single measurement.
3, tensile testing tensile speed: the greater the speed, the greater the strength, the greater the initial modulus. Under normal conditions, with the increase of tensile speed, the breaking strength, initial modulus and yield stress increase, and the elongation at break is not regular.