Four stages of tensile test for small diameter seamless steel tubes

There are four stages of tensile test for small diameter seamless steel tubes

(1) Elastic phase: the deformation of this stage of the sample is completely elastic, all write the load, the sample will restore its original length. The elastic modulus of the material can be determined in this stage.

(2) Yield stage: the elongation of the specimen increases abruptly, while the load reading on the universal testing machine fluctuates in a very small range (jagged lines in the figure). If the slight fluctuation of this load reading is omitted, this stage can be represented by a horizontal line segment on the drawing. If the sample is polished, the surface of the specimen will see a stripe about 45 ° in the direction of the axis, called the slip line.

(3) Strengthening stage: the sample after the yield phase, to make it continue to stretch, because the material in the plastic deformation process continues to strengthen, so the resistance in the sample growing.

(4) Necking stage and fracture stage, the sample elongated to a certain extent, the load reading but gradually reduced.