How to use damage mechanics

The background of continuum damage mechanics is first presented in the framework of thermodynamics with some examples of constitutive equations for ductile damage, creep damage and fatigue damage. After the general scheme of structural calculations for macro-crack initiation, through non-coupled or coupled strain damage equations, some examples of “simple applications” are given: fracture limits of metal forming, surface initial damage in fatigue, creep fatigue interaction, and bifurcation of cracks.     

Fracture mechanics analysis of pressurized cracked shallow shells

The prediction of the behaviour of pressurized cracked thin shells to static or fatigue fracture requires a definition of a crack parameter more general than the stress intensity factors, in order to take into account the local three-dimensional effects of the pressure which causes a local bulging in the cracked area.It is shown that the generalized strain energy release rate derived from an overall energetic balance is a parameter particularly suitable for this problem.Its expression for a non-linear elastic structure is derived and two experimental tests carried out on plates and shells cracked under pressure are described. This proof being obtained, this concept is used in an investigation of sub-structure of a cracked shell in order to estimate this effect of local bulging and to build-up a series of reference results.     

Anatomo-clinical conference: bronchiolo-alveolar cancer and confusion

Rapid membrane recycling in nerve terminals is required to maintain rapid synaptic transmission. Following the fusion of synaptic vesicles with synaptic plasma membranes, recycling can occur via clathrin-coated vesicles (CCVs) [1-3]. The fate of these vesicles is uncertain: they could simply uncoat and acquire other proteins from the cytosol to regenerate synaptic vesicles or they may fuse with endosomal structures from which synaptic vesicles could then bud. We have purified both CCVs and synaptic vesicles from rat brain, and measured the ability of these vesicle fractions to take up the excitatory neurotransmitter glutamic acid. We found that the normalized levels of glutamate uptake by the two types of vesicle were very similar. For each vesicle fraction, uptake required ATP and Cl- and could be fully inhibited by the specific vacuolar proton pump (v-ATPase) inhibitor concanamycin. We suggest that this ability to refill vesicles with neurotransmitter at the earliest intermediate on the recycling pathway - the CCV - may allow uncoated vesicles to immediately enter the releasable pool without sacrificing the quantal nature of neurotransmitter release.     

Replica Management in the European DataGrid Project

Within the European DataGrid project, Work Package 2 has designed and implemented a set of integrated replica management services for use by data intensive scientific applications. These services, based on the web services model, enable movement and replication of data at high speed from one geographical site to another, management of distributed replicated data, optimization of access to data, and the provision of a metadata management tool. In this paper we describe the architecture and implementation of these services and evaluate their performance under demanding Grid conditions.This work was partially funded by the European Commission program IST- 2000-25182 through the European DataGrid Project.     

Earth Observation Satellite Management

The daily management of an earth observation satellite is a challenging combinatorial optimization problem. This problem can be roughly stated as follows: given (1) a set of candidate images for the next day, each one associated with a weight reflecting its importance, (2) a set of imperative constraints expressing physical limitations (no overlapping images, sufficient transition times, bounded instantaneous data flow and recording capacity), select a subset of candidates which meets all the constraints and maximizes the sum of the weights of the selected candidates. It can be easily cast in variants of the CSP, ILP or SAT frameworks. As a benchmark, we propose to the CONSTRAINTS community a set of instances, which have been produced from a simulator of the order book of the future satellite SPOT5. The fact that only some of them have been optimally solved should make them very attractive.     

Recovery of mercury from dental amalgam waste

Dental amalgam waste contains metals such as mercury, silver and tin. Extraction of mercury by distillation was realized in a testing equipment filled with argon at ambient pressure. The influence of temperature and time on the recovery of mercury was investigated. The minimum temperature at which the distillation started was 360°C. For a fast and complete extraction a temperature of at least 500°C was needed.     

Influence of thermal and mechanical surface modifications induced by laser shock processing on the initiation of corrosion pits in 316L stainless steel

Pure mechanical and thermo-mechanical laser shock processing treatments have been carried out on an AISI 316L stainless steel. Surface properties, mostly mechanical and metallurgical modifications, were analysed at different scales: a local scale using the nano-indentation technique and AFM analysis, and a more macroscopic scale, using microhardness, optical microscopy and residual stress determinations. After a pure mechanical laser-peening treatment, a significant improvement in the pitting corrosion resistance (+0.1 V) was observed in 0.05 M NaCl. This improvement was attributed to the combined effects of compressive residual stresses and work-hardening, and, in turn, to a mechano-electrochemical phenomenon by which a modification of cathodic reactions occurs during electrochemical tests. For the surface treated by thermo-mechanical laser peening (combination of a surface ablation and shock waves), a tendency for decreasing resistance against pitting corrosion was shown, and attributed to the processing-specific surface texture (ablation craters), which made the material susceptible for the creation of occluded cells.

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