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The stress–strain relationship of biological soft tissues affected by Marfan's syndrome is believed to be nonconvex. More specifically, Haughton and Merodio recently proposed a strain energy density leading to localized strain-softening, in order to model the unusual mechanical behavior of these isotropic, incompressible tissues. Here we investigate how this choice of strain energy affects the results of some instabilities studies, such as those concerned with the compression of infinite and semi-infinite solids, slabs, and cylinders, or with the bending of blocks, and draw comparisons with known results established previously for the case of a classical neo-Hookean solid. We find that the localized strain-softening effect leads to early instability only when instability occurs at severe compression ratios for neo-Hookean solids, as is the case for bulk, surface, and bending instabilities.

The main aim of this paper is to propose a new boundary element algorithm for describing thermomechanical interactions in anisotropic soft tissues. The governing equations are studied based on the dual-phase lag bioheat transfer and Biot’s theory. Due to the advantages of convolution quadrature boundary element method (CQBEM), such as low CPU usage, low memory usage and suitability for treatment of soft tissues that have complex shapes, it is a versatile and powerful method for modeling of bioheat distribution in anisotropic soft tissues and the related deformation. The resulting linear systems for bioheat and mechanical equations are solved by Transpose-free quasi-minimal residual (TFQMR) solver with a dual-threshold incomplete LU factorization technique (ILUT) preconditioner that reduces the iterations number and total CPU time. Numerical results demonstrate the validity, efficiency and accuracy of the proposed algorithm and technique.

The Sphagnum capsule can disperse spores at an extraordinarily high velocity and acceleration during drying. Briefly, the pressure rise induced by the decrease in the environmental humidity inside the spore chamber causes crack growth between the lid and the capsule wall. At a critical condition, the lid of the capsule suddenly fractures, and the top spores are propelled by the high pressure. Motivated by this phenomenon, we develop a similar mechanics model to study the drying-induced pressure rise and the fracture mechanism of the Sphagnum capsule in this paper. We investigate the drying-induced pressure rise and obtain the deformation configuration for various stiffness ratios of different parts. We also establish a fracture mechanics model and calculate the energy release rate to study the lid separation during the ejection of spores. We find that the energy release rate increases with crack growth when the crack is short, maximizes at an intermediate central crack angle of around $150^{\circ }$, and gradually decreases with further increase in the central crack depending on the loading type. Such a nonmonotonic relationship between the energy release rate and the crack length can be readily used to explain the spontaneously fast unsteady crack growth and the following potential crack arrest reported in the literature. The results and the modeling method obtained in this paper can be used to explain similar fracture-related spore launching of plants and design bioinspired structures to realize the drying-induced fast movement.