A part has been designed for kinematic function and its dime

A part has been designed for kinematic function and its dimensions cannot be changed. To minimize deflections under the same loading in all directions irrespective of stress levels, which of these materials would you choose: polyethylene polymer, silicon nitride ceramic, aluminium metal, titanium metal, stainless steel metal, carbon-fibre reinforced expoxy composite. Why?

Solution

The deflections for a material having fixed kinematic measurements and same loading is inversely proprotional to youngs modulus of the material. Hence out of the given materials the one having the highest value of youngs modulus is going to have minimum deflection.

Stainless Steel has highest modulus = 200 - 210 GPa

Titanium metal = 115 GPa

Aluminium = 70 GPa

Polyethylene polymer = 4 GPa

carbon-fibre reinforced expoxy composite = 120 GPa

silicon nitride ceramic = 170 GPa

Hence stainless steel is the best choice.