Effect of deformation rate on the mechanical properties of arteries

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

Biomechanical Evaluation of Ascending Aortic Aneurysms

“…Though some have used a cruciform specimen [18] or different types of clamping methods, care should be taken when comparing results obtained under different testing conditions, since geometry and boundary conditions may significantly alter the mechanical response observed in a biaxial test [32, 33]. …”

“…Square specimen shape is certainly the most common for biaxial testing of biological soft tissue, although some tests on cruciform specimen of pig arteries have also been reported [18]. …”

“…On the other hand, Delgadillo et al [18] reported instead a significant influence of deformation rate on the uniaxial (and biaxial) response of specimen obtained from pig thoracic aortas, with stiffness of arteries decreasing with increasing deformation rate.…”

“…Specimens for biaxial tests are obtained as square specimens aligned with longitudinal and circumferential directions having side length between 15 mm and 25 mm [ 3 , 8 , 9 , 12 , 13 ]. Square specimen shape is certainly the most common for biaxial testing of biological soft tissue, although some tests on cruciform specimen of pig arteries have also been reported [ 18 ].…”

Characterizing the mechanical properties of the aortic wall

“…Hysteresis loops may be used to estimate damping capacity, which is associated with the ratio of the dissipated energy to the stored energy [69] . An interesting study on strain-rate effect of mechanical properties by Delgadillo et al [70] revealed that at a stretch ratio of 1.5, the experienced load within the arterial wall is reduced by 20% when the strain rate is increased from 10 to 200 %/S. They suggested that: "this behavior might be a consequence of the faster fluidization and small re-solidification that occurs in the cell at higher deformation rates".…”