Four-stage Tensile Test of Small Diameter Seamless Steel Tube


(1) Elastic stage: The deformation of the sample is completely elastic in this stage. When all loads are written, the original length of the sample will be restored. At this stage, the elastic modulus of the material can be determined.


(2) Yield stage: the elongation of the specimen increases suddenly, while the load readings on the universal testing machine fluctuate in a very small range (the zigzag line in the figure). If the light microwave motion of load readings is omitted, the stage can be represented by the horizontal line segment in the figure. If the sample is polished, the surface of the sample will see about 45 degrees of fringes in the axial direction, which is called slip line.


(3) Strengthening stage: The specimen continues to stretch after yielding stage, because the material strengthens continuously during plastic deformation, so the resistance in the sample increases continuously.


(4) During necking and fracture stages, the sample elongates to a certain extent and the load reading decreases gradually.