Abstract
Pig aorta samples were tested uniaxially and equi- biaxially at deformation rates from 10 to 200 %/s. Under uniaxial and biaxial testing, loading forces were reduced up to 20% when the deformation rate was increased from 10 to 200 %/s, which is the opp- osite to the behaviour seen in other biological tissues. A rate-dependent isotropic hyperelastic constitutive equation, derived from the Mooney-Rivlin model, was fitted to the experimental results (e.g. aorta specimens) using an inverse finite element technique. In the proposed model, one of the material par- ameters is a linear function of the deformation rate. The inverse relationship between stiffness and defo- rmation rate raises doubts on the hypothesized rel- ationship between intramural stress, arterial injury, and restenosis.
Highlights
The knowledge of the viscoelastic properties is important to predict the biomechanical behaviour of soft tissues
Under uniaxial and biaxial testing, loading forces were reduced up to 20% when the deformation rate was increased from 10 to 200 %/s, which is the opposite to the behaviour seen in other biological tissues
Material parameter estimation is fundamental for posterior simulation of soft tissue at boundary conditions not selected in the experimental protocol
Summary
The knowledge of the viscoelastic properties is important to predict the biomechanical behaviour of soft tissues To model their viscoelastic behaviour, first one performs appropriate mechanical tests to characterize deformation-rate effects, and one selects a constitutive equation capable of representing those effects. Most biological tissues stiffen with increasing deformation rate [4,7,9,11,12,13, 17] This time-dependent behavior has been described by viscoelastic constitutive models [6,22,23,24,25,26]. Deformation rate effects of arteries, in particular thoracic aorta, were not included in previous studies
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