Determination of an average quasi-linear viscoelastic model for the mechanical behavior of rat cervix

The objective of this study was to determine an average quasi-linear viscoelastic model for the mechanical behavior of rat cervix. The average model is applicable at defined displacement rates for virgin and pregnant tissues in the last trimester of pregnancy. After preconditioning, the displacement of 2 mm was applied to the distal halves of five pregnant rat's cervices and 1 mm to the five virgin samples circumferentially. Uniaxial tension tests were employed at the displacement rates of 0.01, 0.1 and 1 mm/s randomly and were held for 10 min while the tissues were relaxed. Tensile and load-relaxation curves were well described by a quasi-linear viscoelastic model. Two average quasi-linear viscoelastic models were fitted to all 30 curves obtained from experiments for virgin and pregnant tissues. The average quasi-linear viscoelastic model coefficients were extracted using the average model equations. Cervical tissue is strongly viscoelastic. Determination of an average viscoelastic model of rat cervix may lead to a more precise description of the mechanical behavior of the virgin and pregnant tissues in the assessment of cervical insufficiency.