# Shaft torsional stress and twist
# Scope: Uniform solid circular shaft elastic twist.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

torque = 10 N*m in 0..20
diameter = 15 mm in 10..30
length = 300 mm in 100..1000
shearModulus = 79 GPa

polar := pi*diameter^4/32 [mm^4]
stress := torque*diameter/(2*polar) [MPa]
twist := torque*length/(shearModulus*polar) [rad]

radius := diameter/2 [mm]
center := length/2 [mm]
twistAt(x: mm) := twist*x/length [rad]
part shaft "Shaft": cylinder radius, length at center, 0 mm, 0 mm rot 0 deg, 90 deg, 0 deg

check twist budget: twist <= 1 deg

scenario alternative: torque = 8 N*m