The effect of vibratory stress on the welding microstructure and residual stress distribution

Previous studies have suggested that weld microstructure may be modified by the presence of static stresses. In this investigation, vibratory stress was applied to mild steel specimens while they were being welded to observe its effect on the residual stress, microstructure and hardness of the material. Residual stresses were found to decrease in response to vibration whether it was applied during welding or after welding. It was found that the applied stress influenced the grain growth process in the weld. As a result of the treatment the hardness of the material was found to be increased by 25 per cent

Genetic variation in eggshell crystal size and orientation is large and these traits are correlated with shell thickness and are associated with eggshell matrix protein markers

The size and orientation of calcium carbonate crystals influence the structure and strength of the eggshells of chickens. In this study, estimates of heritability were found to be high (0.6) for crystal size and moderate (0.3) for crystal orientation. There was a strong positive correlation (0.65) for crystal size and orientation with the thickness of the shell and, in particular, with the thickness of the mammillary layer. Correlations with shell breaking strength were positive but with a high standard error. This was contrary to expectations, as in man-made materials smaller crystals would be stronger. We believe the results of this study support the hypothesis that the structural organization of shell, and in particular the mammillary layer, is influenced by crystal size and orientation, especially during the initial phase of calcification. Genetic associations for crystal measurements were observed between haplotype blocks or individual markers for a number of eggshell matrix proteins. Ovalbumin and ovotransferrin (LTF) markers for example were associated with crystal size, while ovocleidin-116 and ovocalyxin-32 (RARRES1) markers were associated with crystal orientation. The location of these proteins in the eggshell is consistent with different phases of the shell-formation process. In conclusion, the variability of crystal size, and to a lesser extent orientation, appears to have a large genetic component, and the formation of calcite crystals are intimately related to the ultrastructure of the eggshell. Moreover, this study also provides evidence that proteins in the shell influence the variability of crystal traits and, in turn, the shell’s thickness profile. The crystal measurements and/or the associated genetic markers may therefore prove to be useful in selection programs to improve eggshell quality

Microstructure of a liquid complex (dusty) plasma under shear

The microstructure of a strongly coupled liquid undergoing a shear flow was studied experimentally. The liquid was a shear melted two-dimensional plasma crystal, i.e., a single-layer suspension of micrometer-size particles in a rf discharge plasma. Trajectories of particles were measured using video microscopy. The resulting microstructure was anisotropic, with compressional and extensional axes at around $\pm 45^{\circ}$ to the flow direction. Corresponding ellipticity of the pair correlation function $g({\bf r})$ or static structure factor $S(\bf{k})$ gives the (normalized) shear rate of the flow.Comment: 5 pages, 6 figure

Residual stress relaxation and microstructure in ZnO thin films

Stability under normal environmental conditions over a long period of time is crucial for sustainable thin-film device performance. Pure ZnO films with thicknesses in the 140 - 450 nm range were deposited on amorphous glass microscope slides and (100)-oriented single crystal silicon wafers by radio frequency magnetron sputtering. The depositions were performed at a starting temperature of 200 oC. ZnO films had a columnar microstructure strongly textured along the direction. XRD peak-shift analysis revealed that the films were under residual, compressive, in-plane stress of -5.46 GPa for the glass substrate and -6.69 GPa for the Si substrate. These residual stresses could be completely relaxed by thermal annealing in air. When left under normal environmental condition over an extended period of time the films failed under buckling leading to extensive cracking of the films. The XRD and SEM results indicated different mechanisms of stress relaxation that were favored in the ZnO thin films depending on the energy provided. Although thermal annealing eliminated residual stresses, serious micro-structural damage upon annealing was observed. Thermal annealing also led to preferential growth of some ZnO crystals in the films. This kind of behavior is believed to be indicative of stress-induced directional diffusion of ZnO. It appears that for the extended stability of the films, the stresses have to be eliminated during deposition