S.E. Civil 2019 Pattern- Mechanics of Structures Practical's 6. Torsion test on Mild steel using digital torsion Testing machine. In torsion testing the circular bar is placed in the machine such a way that its longitudinal axis coincides with the axis of the grips and so that it remains straight during the test. Then rotate one grip at a reasonable constant speed until the test piece breaks, here the shearing stresses will develop in any cross section of the bar whose value increases linearly from zero at the center to a maximum at the outer periphery. Please watch video for more details-