fracture mechanics

I’ll present this below without the answer, in case you want to enjoy a little brain teaser. It is a solid and experimental mechanics problem that, while not terribly practical, I found very interesting:

A part fractures cleanly in two by brittle fracture (no plasticity) under the action of residual and applied stresses. You only have the broken part in front of you, no prior information.

 What were the original residual stresses on the fracture plane?

Dear Colleague,

this is to inform you that the research unit MUSAM "Multi-scale Analysis of Materials" (http://musam.imtlucca.it) at the IMT Institute for Advanced Studies Lucca (Italy) has opened 1 Post-doctoral Fellow position (1 year but renewable for a maximum of 3 years in total) on Computational mechanics applied to solar energy materials, related to the ERC Starting Grant CA2PVM

(http://musam.imtlucca.it/CA2PVM.html) and under my supervision.

In armchair graphene sheets, crack propagates perpendicular to the applied strain, whereas crack propagation in zigzag sheets occurs at an angle to the straining direction. This occurs due to different bond structure along armchair and zigzag directions as shown in Fig. 1. Videos 1 and 2 show the fracture of armchair and zigzag sheets, respectively.

Fig. 1: Armchair and zigzag directions of graohene

The Department of Civil and Environmental Engineering at the National University of Singapore (NUS) is recruiting 2 post-doctorate research fellows to pursue research on ice-structure interaction in the Keppel-NUS Corporate Laboratory. As part of the S$75 million collaboration between Keppel Corporation and NUS, the team comprising of Prof. Andrew Palmer, Dr. Bai Wei, and Dr. Pang Sze Dai, seeks to develop solutions for offshore rigs to meet the challenges of harsh arctic environments in oil and gas exploration and production.

I have updated my notes on the Griffith paper.  I added more description on the experimental determination of surface tension of solids.  Griiffith himself determined the surface tension of glass by an experimental setup.  Udin et al (1949) described a setup based on the same principle.  This setup is now known as the zero creep experiment.

The class started today.  I'll be teaching fracture mechanics this semester.  I'll be mostly using the class notes I wrote in 2010, but will post updated ones. 

In today's class I covered "Trouble with linear elastic theory of strength."  I have just posted updated notes of the lecture.  The new notes begin with the follwoing paragraphs.

Applications are invited for few open positions in the area of
multiscale simulation of fatigue and fracture of advanced alloys and
nano-material based composites. Primary focus of this research is investigation
of fatigue and fracture behavior of nanomaterials and to develope various
constitutive models for continuum, based on large scale atomistic simulations.
Research effort will include development of analysis and design methods toward
improving material/structural behaviour using computer simulation. Interested
candidates should have preferably MTech/ME degree in
mechanical/civil/aerospace/material engineering discipline with good knowledge