A ringshaped seal made from a viscoelastic material is used

A ring-shaped seal, made from a viscoelastic material, is used to seal a joint between two rigid pipes. When incorporated in the joint, the seal is held at a fixed compressive strain of 0.2. Assuming that the seal can be treated as a Maxwell model, determine the time before the seal begins to leak under an internal fluid pressure of 0.3 MPa. It can be assumed that the relaxation time tau_0 of the material is 300 days and the short-term (instantaneous) modulus of the material is 3 MPa.

Solution

Use formula for maxwell solid: S(t) =S(0) exp(-t/T0)

given S(t) =0.3

S(0)= Modulus*strain =3MPa*0.2 =0.6MPa

0.3 =0.6*exp(-t/T) where T =300 days

-0.693 = t/300

t= 208 days approx/