Question

What is the quasilinear viscoelastic (QLV) theory and why is it applicable to understand the material behaviour of tendons and ligaments?

Answer 1

Quasilinear viscoelasticity is a kind of model that incroporates non-linearity and time dependance in a single and simplified integral model. According to this model, J(creep compliance) depends on two factors- Time(t) and stress (σ):

J(t, σ) = J1(t) f(σ)

Creep compliane (J)= total load strain per unit stress

QLV is used to perform various experiments in order to differentiate between linear and non linear models and by these experiments it is known that the shape of the relaxation curve is same, irrespective of what the strain is. Now this particular model or theory is used mostly to study or describe biological tissues.The overall scenario is that when a particular viscoelastic material experiences constant strain, it tends to have an increase in strain which is time dependant, i.e., the strain remains for a particular time period.

Now coming to the biomechanics, the tissues of tendon, ligament etc are all the mechanical supporters of the body. These mechanical components tend to experience strain or stress almost everytime we try to do some work. QLV helps to describe the perfomance of these biological tissues by studying the time dependant elasticity.