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Dislocation structures inside the cleared dislocation channels in rapid-cooled and tensile-deformed aluminum single crystals were investigated by using transmission electron microscope (TEM). The present study especially focused on the dislocation structures at their early formation stage. In their very beginning stage, arrays of prismatic dislocation loops of the primary slip system were essentially formed elongating along ½ 1 2 1 direction and each prismatic loop stacked to ½ 1 0 1. With the progress of plastic deformation, the number of the prismatic loops composing the array increased and produced tangled structures with dislocations of the primary coplanar slip system. The tangled structures may act as strong obstacles against the following primary dislocations and become a triggering factor for the creation of the cell structure.

A theoretical model for progressive solidification is described. It reproduces the experimental finding, from centrifugal wave tank testing with viscous scaling, that a layer of liquefied sand solidifies progressively from the base up while severe fluid-wave loading is imposed over a prolonged period of time. The solidification process reestablishes a grain-supported framework in the transitory fluid-like soil and is accompanied by the marked densification and gradual dissipation of excess pore pressures in a zone immediately below the upward-advancing solidification front. The continued disturbances to liquefied soil in the form of wave loading are an effective means for loosening the interlocking of solid particles, and permit rearrangement into a state of remarkably dense compaction due to contractancy. These aspects of soil behaviour are accentuated through comparison with consolidation in quiescent conditions following liquefaction. Furthermore, the proposed rigorous treatment of solidification as a moving-boundary problem provides a basis for reappraisal of an expression that was presented by Florin & Ivanov regarding the velocity of the solidification front.

The plasma nitriding of tool steel under atmospheric-pressure was performed using a dielectric barrier discharge method, resulting in the formation of a uniform nitrided layer. In this study, the tribology properties of the nitrided layer generated by atmospheric-pressure plasma nitriding were investigated. The results showed that the surface hardness of the tool steel nitrided by the atmospheric-pressure plasma method were increased by more than twofold compared with that of the core material. The surface hardness and the thickness of the nitrided layer were uniform, with values of 1300 HV and 30 m, respectively. In addition, the wear rate of the sample nitrided by the atmospheric-pressure plasma method was decreased by more than 25 times compared with that of the untreated sample. Only the emission of the N 2 second positive system and Ar were detected by the optical emission spectroscopic observation of the generated plasma. For this reason, we consider that the nitriding of this research caused by the dissociation of nonexcited N 2 , NH 3 , NH 2 , and NH etc. on the sample like a gas nitriding.

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The propagation of lique®ed zones in sand beds under¯uidwave loading is theoretically analysed in the present study. The completely lique®ed state of sand is modelled as an inviscid¯uid of a particular density, and the underlying sub-lique®ed soil is modelled as a poro-elastoplastic material obeying a simple law of cyclic plasticity. It is shown that the proposed theoretical model is capable of consistently predicting the progressive nature of liquefaction as observed in centrifuge wave tank tests on loose deposits of ®ne-grained sand. The theoretical model can also predict the ®nal depth of the liquefaction front under a given wave loading.Dans cette e Âtude, nous analysons de manie Áre the Âorique la propagation des zones lique ®e Âes dans ses bancs de sable sous chargement onde-¯uide. L'e Âtat comple Átement lique ®e  du sable est mis en maquette sous forme de¯uide parfait d'une densite  particulie Áre et le sol sous-jacent sous-lique ®e  est mis en maquette sous forme de mate Âriau poro-e Âlastiplastique obe Âissant a Á une simple loi de plasticite  cyclique. Nous montrons que le mode Ále the Âorique propose  est capable de pre Âdire de manie Áre cohe Ârente la nature progressive de la lique Âfaction telle qu'elle est observe Âe dans des essais a Á ondes centrifuges dans des bacs, sur des de Âpo Ãts meubles de sable a Á grains ®ns. Le mode Ále the Âorique peut e Âgalement pre Âdire la profondeur ®nale du front de lique Âfaction sous charge d'onde donne Âe.

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