Abstract:
The understanding of strain rate-dependent mechanical properties of the skin is important
for accurate prediction of its biomechanics under different loading conditions. This
study investigated the effect of strain rate, i.e., 0.025/s (low), 0.5/s (medium), and 1.25/s
(high), ranging in the physiological loading rate of connective tissue, on the stressrelaxation
response of the porcine dermis. Results show that in the initial phase of the
relaxation, the value of stress relaxation (extent of relaxation) was found higher for high
strain rate. However, the equilibrium stress was found strain rate independent. A
Mooney–Rivlin-based five-term quasi-linear viscoelastic (QLV) model was proposed to
determine the effect of strain rate on the stress-relaxation behavior of the porcine dermis.
The value of relaxation modulus G1 and G2 were found higher for the high strain rate,
whereas the reverse trend was observed for G3, G4, and G5. Moreover, the value of time
constants s1,s2,s3 s4, and s5 were found higher for low strain rate. Statistical analysis
shows no significant difference in the values of G5, s4, and s5 among the three strain
rates. The proposed model was found capable to fit the stress-relaxation response of skin
with great accuracy, e.g., root-mean-squared-error (RMSE) value equal to
0.01560.00012 MPa. Moreover, this hyper-viscoelastic model can be utilized: to quantify
the effects of age and diseases on the skin; to simulate the stresses on sutures during
large wound closure and impact loading.
