Failure analysis of two cold-working cutting tools. Case studies

The study examines the dramatic drop in the efficiency of a cutting tool. The specific tool is part of machine used for cutting envelopes of paper for medical products packaging. Two similar pieces, selected after breaking down in service, were examined in depth. Historical data was collected. The tool temperature range during operation and the material hardness were measured. The fracture surfaces as well as the surrounding areas were carefully inspected. Chemical analysis was performed in order to identify the tool and coating materials. Results showed that components were made of different steels: D2 and Vanadis 6. The coating material also differs. Samples were selected and prepared for optical and electron microscopy. The condition of the cutting edges and the heat-treated microstructure were considered. Thickness, quality and homogeneity of the coatings were also inspected. Both tools failed by fatigue mode under different conditions. The fracture mechanism and its principal causes are discussed. The reasons of failure for both cutting tools are examined and compared. Poor designs associated with improper handling have led to the components breakage. Appropriate recommendations are given in order to eliminate similar situations and to improve the cutting performance

Impaired recognition memory and emotional reactivity associated with loss of cortical integrity in rats after chronic exposure to aluminum

Although the neurotoxic effects of aluminum (Al) have been extensively investigated, with a particular emphasis on the contribution of this metal to several neurodegenerative conditions such as Alzheimer’s disease, there are few studies on behavioral impairments associated with Al exposure. This lack of data is even more provocative since recent researches have shown that Al induces significant cerebrovascular alterations in cortical architectures. We have investigated possible behavioral impairments of spatial recognition memory and emotional reactivity on rats that were chronically exposed to Al. Concurently, we have studied cytoarchitectural integrity of isocortex, hippocampus and entorhinal cortex, and striatopallidal structures on brain sections stained with the Bielchowsky silver stain method. Our results indicated spatial recognition memory deficits that were significantly represented on spontaneous alternation task performances, but less obvious on Morris water maze task performances of experimental animals, suggesting differences in the sensitivity of these two spatial memory paradigms. We also observed emotional reactivity patterns of modifications on male and female rats exposed to Al. This sexsegregated difference was not completely surprising since estrogens could have neuroprotective effects on adult female rats exposed to Al, although this specific hormonal modulation remains to be tested. These behavioral modifications were associated with massive cellular depletion in frontal isocortex, hippocampus and entorhinal cortex, but relatively spared striatopallidal structures. We concluded that Al primarily induces the structural alteration and functional isolation of the hippocampus, correlated with behavioral deficits on hippocampal-dependent tasks