Nanoindentation-induced mechanical deformation in GaN thin films prepared by metal-organic chemical-vapour deposition was investigated using the Berkovich diamond tip in combination with the cross-sectional transmission electron microscopy (XTEM). By using focused ion beam milling to accurately position the cross-section of the indented region, the XTEM results demonstrate that the major plastic deformation was taking place through the propagation of dislocations. The present observations are in support of attributing the pop-ins that appeared in the load–displacement curves to the massive dislocation activities occurring underneath the indenter during the loading cycle. The absence of indentation-induced new phases might have been due to the stress relaxation via the substrate and is also consistent with the fact that no discontinuity was found upon unloading.
Quantitative analyses of human sagittal suture using length, length ratio, and DFT indicated that there is a progressive increase in the complexity of sagittal sutural waveform with age, especially in the early ages. These findings agree with the observations from animal experiments that sagittal sutural waveform is the result of intrinsic tissue response to extrinsic forces such as those generated by the temporalis.
With advancement of technology, package sizes and products are becoming smaller due to miniaturization. Separate light-emitting diode (LED) chips and control integrated circuits with through silicon via (TSV) structurescan be combined to achieve reduced size. LED chipswithFlip Chip structureare capable of higher optical efficiency and heat dissipation. Analysis of LED chip structure after heat-related destruction of the chip indicated that the chip suffered stress from heating and cooling. The material used for TSV structures is copper, sincethis provides good electrical conductivity and high thermal conductivity. However, the thermal expansion coefficient of copper is higher than for other materials and can result in thermal expansion coefficient mismatch. Hence, the use of this material is likely to cause stress concentration and thus cause damage. In this study, molybdenum and tungsten were tested as replacements for copper in TSV, and the modified TSV was subjected to simulation analysis.The results indicate that replacement of TSV materials can reduce thermal expansion coefficient mismatch and consequent stress fracture and that the performance of different materials can be simulated by Fatigue Analysis and Load.
The purposes of this paper are to weld dissimilar aluminum alloys joints, AA1050 and AA6061, and to find Young’s modulus on the welded zone along the thickness. Dissimilar aluminum alloys plates are friction stir welded in the butt configuration by using an adapted milling machine. Young’s modulus of components is found out by applied a reverse method and the out-of-plane displacement is measured by Electronic Speckle Pattern Interferometry. The out-of-plane displacement of the welded cantilever beam is subjected to a concentrated load. The results reveal that Young’s modulus in the welded zone is the deeper the smaller.
A method of numerical simulations is used to predict the profile of a 3-D aspherical microlens array. Based on the simulated results, the desired micro-optical lens profile is obtained through excimer laser ablation. The simulation method applied in the excimer laser ablation can significantly reduce the quantity of microablation experiments. The ablated microstructures with surface average roughness of RaϽ20 nm are successfully achieved for micro-optical components. The excimer laser ablation parameters include laser fluence, shot number, workstation scanning velocity, and repetition rate. Various profiles of microlens and microprism arrays with different dimensions can utilize numerical simulation and form desired geometries by laser ablation.
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