Here's a puzzle for our readers.  The following image is of the surface of a failed joint followed by a picture of the joint (not the same one but a similar one) before joining.  What material is it? What caused the failure?  All manner of speculation is welcome.

Please see attachment for details of Computational Mechanics researcher openings at Industrial Research (www.irl.cri.nz), a Crown Research Institute in beautiful New Zealand.

The role involves the application of advanced modeling and simulation methods to research on solids and structures, with an emphasis on complex systems such as composites and meta-materials, or solids with multiple defects and discontinuities.

The position is research oriented but also provides opportunities to consult with industry on commercial projects.

Candidates with expertise in theory and computation of elastic wave propagation, the mechanical behavior of composites, structural dynamics, or acoustics are encouraged to apply.

The increasing use of fiber-reinforced composites accentuates the need for developing multi-axial fatigue failure models for these materials. In this article (attached), we proposed several multiaxial fatigue failure models for fiber-reinforced composites considering the contribution of mean and cyclic normal stress/strain and shear stress/strain at the plane of failure and examined their capability for predicting the fatigue life of the E-glass/epoxy composite materials.

Using the Griffith energy method for analysis of cavitation under hydrostatic tension we conclude that the critical tension tends to infinity when the cavity radius approaches zero (IJSS, 2006, doi: 10.1016/j.ijsolstr.2006.12.022). The conclusion is physically meaningless, of course. Moreover, if we assume that the failure process occurs at the edge of the cavity then the critical tension should be length-independent for small but finite cavities while the Griffith analysis always exhibits length-dependence. The main Griffith idea - introduction of the surface energy - is controversial because it sets up the characteristic length, say, surface energy over volume energy. By no means is this approach in peace with the length-independent classical continuum mechanics.

If you are interested by the computational aspects of fracture and failure of materials and structures,there is a dedicated conference for you : CFRAC 2007, which will be held in Nantes, France, 11-13 June 2007. It is an thematic conference of the European Community in Computational Methods in Applied Sciences (ECCOMAS). The for abstract is now closed. This conference wil involve a certian number