Hierarchical approach to 'atomistic' 3-D MOSFET simulation

We present a hierarchical approach to the 'atomistic' simulation of aggressively scaled sub-0.1-μm MOSFETs. These devices are so small that their characteristics depend on the precise location of dopant atoms within them, not just on their average density. A full-scale three-dimensional drift-diffusion atomistic simulation approach is first described and used to verify more economical, but restricted, options. To reduce processor time and memory requirements at high drain voltage, we have developed a self-consistent option based on a solution of the current continuity equation restricted to a thin slab of the channel. This is coupled to the solution of the Poisson equation in the whole simulation domain in the Gummel iteration cycles. The accuracy of this approach is investigated in comparison to the full self-consistent solution. At low drain voltage, a single solution of the nonlinear Poisson equation is sufficient to extract the current with satisfactory accuracy. In this case, the current is calculated by solving the current continuity equation in a drift approximation only, also in a thin slab containing the MOSFET channel. The regions of applicability for the different components of this hierarchical approach are illustrated in example simulations covering the random dopant-induced threshold voltage fluctuations, threshold voltage lowering, threshold voltage asymmetry, and drain current fluctuations

Mechanical and Wear Properties of SiC/Graphite Reinforced Al359 Alloy-based Metal Matrix Composite

Al359 alloy was reinforced with Silicon Carbide and Silicon Carbide/Graphite particles using stir casting process. Thereafter their mechanical and wear properties were investigated. It was found that the hardness of the Al359-Silicon Carbide composite is better than Al359-Silicon Carbide-Graphite composite. The Silicon Carbide/Graphite reinforced composite exhibits a superior ultimate tensile strength against Silicon Carbide reinforced composite. The wear test was conducted at different loading, sliding velocities and sliding distances conditions. Results showed that the wear resistance of Al359 alloy increased with the reinforcement of Silicon Carbide/Graphite material for higher loading, sliding velocities and sliding distance conditions. SEM images of the worn surface of the pin were examined to study their wear mechanism.Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 330-338, DOI: http://dx.doi.org/10.14429/dsj.65.867

Effect of Ply Orientation on Strength and Failure Mode of Pin Jointed Unidirectional Glass-epoxy Nanoclay Laminates

In the present work the effect of the different ply orientations and nano filler on the bearing strength and failure mode of the pin joints is investigated both experimentally and numerically. Glass-epoxy composite laminates were prepared with [0°/45°/90°], [0°/45°/0°] and [0°/90°/0°] ply orientations. Nanoclay filler with 1, 2, 3, 4 and 5wt% were added in the epoxy for the said orientations to prepare the pin joints. Results show that the strength of the pin joints is drastically dependent on both ply orientations and nanofiller wt%. The joint geometry i.e., the distance from the free edge of specimen to the diameter of the hole (E/D) ratio and width of the specimen to the diameter of the holes (W/D) ratio were also investigated which effected the failure mode of the joints. Tsai-Wu failure theory along with the characteristics curve method was used for the prediction of failure modes numerically

Efficiency and Stiffness of the Single Lap Bolt Joints in Glass Epoxy Composites

The present work deals with the investigations on the joint efficiency and the joint stiffness of the single lap bolt joint made of two dimensional woven glass fibre reinforced composite materials. The effect of joint geometry, bolt pretension and washer has been determined on the bolt joint performance. To estimate the effect of geometric parameters; the edge-to-hole diameter (e/d) and width-to-hole diameter (w/d) ratios are varied from 3 to 4 and 3 to 5, respectively. To study the worst loading conditions; the bolt pre-tension is set to zero, whereas 5 Nm torque is applied to investigate the joint in fully clamped conditions. Two different sizes of washer i.e., the outer diameter of 12 mm and 16 mm have been studied to estimate the effect of the washer on failure load, joint stiffness, and joint efficiency. Progressive damage analysis has been performed on the single lap bolt joint. Characteristic curve method along with Tsai-Wu failure criteria has been used for the prediction of the failure loads and failure modes. The joint stiffness and the failure load of the joint are increased with the increase of w/d ratios. However, the joint efficiency was negatively influenced by w/d ratio

Effect of Metallic Inserts on the Strength of Pin Joints Prepared from Glass Fiber Reinforced Composites

The present study deals with the failure analysis of pin joints by varying different geometric parameters i.e., edge distance to hole diameter (E/D) ratio and width to hole diameter (W/D) ratio. Pin joints were prepared from the glass fiber reinforced laminates incorporating the metal inserts. A range of 2 to 5 and 3 to 6 was considered for E/D and W/D ratios, respectively. The stress around the hole was redistributed by incorporating the metal inserts in the hole to increase the load carrying capacity. To predict the failure loads and failure modes numerically, progressive damage analysis along with Hashin failure criteria was used in the pin joints. Strength of the pin joints increased in the range of 65 per cent to 92 per cent with metal insert due to the redistribution of the stresses around the hole. Progressive damage analysis gave a good correlation with experimental findings. Thereafter, the strength of the joint was predicted by varying the thickness of the metal inserts