Conditions of necking down in steel-sample tension

In the tension testing of metal samples on account of deformation strengthening, the load increases, reaches a maximum, and then decreases with necking down in the sample. This work tested steels St. 3sp, St. 3kp, and steel 45 in the hot-rolled and aged (10 percent preliminary deformation, tempering at 250°C for 1 hr) states. Samples were tested in the temperature range from -100 to 300°C at a deformation rate of 8.5×10-4 sec-1. The deformation at which the yield stress reaches the numerical value of the deformation strengthening coefficient may either be determined graphically or else calculated analytically from the known strengthening parameter.