Recently I received a message from the Cambridge University Press regarding a coming text on biomechanics entitled Introductory Biomechanics, From Cells to Organisms. by C. Ross Ethier and Craig A. Simmonds. I ordered an exam copy, went through, and found it very interesting. It covers cellular biomechanics, hemodynamics, circulatory system, ocular biomechanics, muscles and movement, and skeletal biomechanics. Each section has a significant number of problems. I examined closely the part on cellular biomechanics which is one of the main areas of my research and teaching interests, and enjoyed reading it. The cellular mechanics is presented in its interrelation to cell structure and biology (there are nice images of cells and their components to use for teaching). The main techniques of probing the cell, such as micropipette aspiration, AFM, optical tweezers, and magnetic cytometry, are considered. Models of the cytoskeleton (tensergity, foams) are also introduced. The math is limited to linear equations, one-dimensional or axisymmetric problems, but it seems appropriate for the introductory level. In addition, some results of computational (finite element) modeling are also included. I certainly expect that this textbook will be quite useful in my teaching. The web site http://www.cambridge.org/us/catalogue/catalogue.asp?isbn=9780521841122 has more details on the book.

As another celebration of March Journal Club of Mechanics of Flexible Electronics, this paper has just been submitted.

Abstract 

In one design of flexible electronics, thin-film islands of a stiff material are fabricated on a polymeric substrate, and functional materials are grown on these islands. When the substrate is stretched, the deformation is mainly accommodated by the substrate, and the islands and functional materials experience relatively small strains. Experiments have shown that, however, for a given amount of stretch, the islands exceeding a certain size may delaminate from the substrate. We calculate the energy release rate using a combination of finite element method and complex variable method. Our results show that the energy release rate diminishes as the island size or substrate stiffness decreases. Consequently, the critical island size is large when the substrate is compliant. We also obtain an analytical expression for the energy release rate of debonding islands from a very compliant substrate.

A typical two phase microstructure consists of a topologically continuous `matrix' phase in which islands of `precipitate' phase are embedded. Usually, the matrix phase is also the majority phase in terms of volume fraction. However, sometimes this relationship between the volume fraction and topology is reversed, and this reversal is known as phase inversion. Such a phase inversion can be driven by an elastic moduli mismatch in two-phase solid systems. In this paper (submitted to Philosophical magazine), we show phase inversion, and the effect of the elastic moduli mismatch and elastic anisotropy on such inversion.

During solid-solid phase transformations elastic stresses arise due to a difference in lattice parameters between the constituent phases. These stresses have a strong influence on the resultant microstructure and its evolution; more specifically, if there be externally applied stresses, the interaction between the applied and the transformation stresses can lead to rafting.

From an engineering point of view, prediction of fatigue crack nucleation in automotive rubber parts is an essential prerequisite for the design of new components. We have derived a new predictor for fatigue crack nucleation in rubber. It is motivated by microscopic mechanisms induced by fatigue and developed in the framework of Configurational Mechanics. As the occurrence of macroscopic fatigue cracks is the consequence of the growth of pre-existing microscopic defects, the energy release rate of these flaws need to be quantified. It is shown that this microstructural evolution is governed by the smallest eigenvalue of the configurational (Eshelby) stress tensor. Indeed, this quantity appears to be a relevant multiaxial fatigue predictor under proportional loading conditions. Then, its generalization to non-proportional multiaxial fatigue problems is derived. Results show that the present predictor, which covers the previously published predictors, is capable to unify multiaxial fatigue data.

With the increasing use of shape memory alloys in recent years, it is important to investigate the effect of cracks. Theoretically, the stress field near the crack tip is unbounded. Hence, a stress-induced transformation occurs, and the martensite phase is expected to appear in the neighborhood of the crack tip, from the very first loading step. In that case, the crack tip region is not governed by the far field stress, but rather by the crack tip stress field. This behavior implies transformation toughening or softening.

This paper shows that the stress field in the classical theory of continuum mechanics
may be taken to be a covector-valued differential two-form. The balance laws and other funda-
mental laws of continuum mechanics may be neatly rewritten in terms of this geometric stress. A

Springer - in an attempt to get customers I suppose - are offering free access to the journal Computational Mechanics, but only for March 2007.

You can access all articles in Computational Mechanics back to vol 1/1, e.g. the first article

E. Reissner
Some aspects of the variational principles problem in elasticity
Volume 1, Issue - 1, First Page - 3, Last Page - 9
DOI - 10.1007/BF00298634
Link - http://www.springerlink.com/content/t52w761088542m68


To get the free access (for the rest of March) go to
http://scientific-direct.net/c.asp?id=650015&c=7fbfc8d9b40ac978&l=31

Please joint me in congratulating Dr. Stelios Kyriakides’ (Editor of International Journal of Solids and Structures) for his election to the United States National Academy of Engineering.