Strength of Materials | Beam Stress Deflection
Mechanics and Machine Design, Equations and Calculators

Springs of rubber bonded to metal are made in a wide variety of configurations. The rubber is usually in shear and, because of the high internal damping, such springs are used for limiting vibrations.

Two-block shear spring - load P

Symbols used:
A = Area rectangular plate, (mm², in²)
P = Loading Force, (N, lbs)
E = Young’s modulus, (N/mm², lbs/in²)
H = Rubber thickness, (mm, in)
G = Shear modulus

Stress equation

Shear stress τ = P / 2A
Deflection y = Ph / 2AG
where G = shear modulus.

Modulus and strength of rubber
G = 0.3 to 1.2MPa
E = 0.9 to 3.6 MPa
Allowable shear stress = 0.2 to 0.4 MPa
Deflection limited to 10% to 20% of free height.