Shear From Torsion !link! ★ Direct Link

Materials like cast iron or glass are weaker in tension than in shear. When twisted, they tend to crack at a 45-degree angle. This is because the maximum tensile stress in a twisted shaft occurs at that specific diagonal. Real-World Applications

Stress increases linearly as you move outward. The highest stress always occurs at the outer edge (the "skin") of the object. shear from torsion