what is torsion

Torsion is the twisting of an object due to an applied torque). It is a type of deformation caused by a moment acting about the objects longitudinal axis. Torsion is expressed in either the pascal (Pa), an SI unit for newtons per square meter, or in pounds per square inch, while torque is expressed in newton-meters (Nm) or foot-pounds (ft-lbs) ). The highest shear stress occurs on the surface of the object, where the radius is maximum, and high stresses at the surface may be compounded by stress concentrations such as rough spots). Shaft surfaces for use in high torsion are polished to a fine surface finish to reduce the maximum stress in the shaft and increase their service life). Testicular torsion is a medical condition that occurs when a testicle rotates, twisting the spermatic cord that brings blood to the scrotum, causing sudden and often severe pain and swelling.