The concept of torque: The torsionally deformed rod is often called a torsion axis, and the internal force on the cross section of the torsion axis is called torque (MT)

Find torque using cross-section method

The rules for positive and negative torque: Determined by the right-hand screw rule, if the torque vector is consistent with the normal line outside the section, the torque is positive; otherwise, it is negative.

Torque diagram

Experimental observations

Assumption: Since the wall is very thin, it can be assumed that the shear stress is uniformly distributed along the wall thickness

in conclusion

pure shear

Shear Stress Twin Equivalence Theorem

Shear Hooke's Law

condition

Stiffness check

Section size design

Maximum external load calculation

Observe phenomena

plane hypothesis

Qualitative conclusion

deformation relationship

physical relationship

static relationship

General formula for torsional shear stress

Strength condition

Strength condition application