Leverhulme Visiting Professorship

The underlying objective of this project was to systematically investigate and characterise the rate-dependency of the mechanical behaviour of heart valves. This investigation was tackled at two levels: (i) Design of valid experiments that enabled proper examination of the rate-effects in the mechanical behaviour of semilunar (aortic and pulmonary) heart valves; and (ii) Lay the foundations of developing continuum-based models for capturing this rate-dependency as well as other complex mechanical attributes of the valves including anisotropy and the dispersion of fibres. To this end, we invited and hosted Prof. Gerhard A. Holzapfel form the Institute of Biomechanics, Graz University of Technology (Austria). During his visit we designed and carried out experiments which uncovered and documented the effects of rate of deformation on the mechanical behaviour of the valves, and worked on developing a new class of continuum-based models which incorporate the rate of deformation as an explicit variable. The findings of this work were published via three journal papers as follows:

1- A transverse isotropic constitutive model for the aortic valve tissue incorporating rate-dependency and fibre dispersion: application to biaxial deformation. In: Journal of the Mechanical Behavior of Biomedical Materials. 85, 80-93.

2- Rate-dependency of the mechanical behaviour of semilunar heart valves under biaxial deformation. In: Acta Biomaterialia. 88, 120-130.

3- Rate-dependent mechanical behaviour of semilunar valves under biaxial deformation: from quasi-static to physiological loading rates. In: Journal of the Mechanical Behavior of Biomedical Materials. 104, 103645.

1- The mechanical behaviour of the semilunar heart valves is rate-dependent, typically becoming stiffer with increase in the rate of deformation.

2- Extensive set of stress-stretch experimental data under biaxial deformation over a 10,000-fold range of rate, from quasi-static to physiological rates.

3- Development of a new class of continuum-based models for application to the rate-dependent mechanical behaviour of heart valves with the rate of deformation as an explicit variable.