Problem #$1.$ In a stress relaxation test, an $8-$mm long segment of cardiac tissue was stretched

instantaneously to stress the tissue to $180$MPa. After $2$ minutes, the stress measured in the tissue had

decreased to $165$MPa. Assume the material response can be characterized by a Maxwell model.

a$.$ Calculate the relaxation time of the material.

b$.$ If the initial stress was reached by extending the cardiac tissue by $2\mathrm{.}3mm,$ what is the

viscosity of the dashpot in the model?

c$.$ Calculate the relaxation modulus of the material after $3$ minutes and $15$ seconds, given the

same conditions as above.

Comprehension:

What is Frank$-$Starling Stretch Response?

The Maxwell model was used to

characterize stress$-$relaxation. Explain what

the spring and dashpot elements represent

mechanically, and what constituents of the

cardiac tissue they each model.

Draw the deformation vs time plot for this

model.

Stretch

Control

Control