Applied Mechanics and Materials Vols. 110-116

Abstract: We report reactivity of silicon doped single walled carbon nanotube (Si-CNT) towards the small atmospheric gas molecules O₂, CO₂, SO₂ and NO₂ using density functional theory based on the numerical basis set method. The reactivity of these molecules is explained on the basis of electronic properties such as binding energy, charge density, charge transfer and density of states. The large change in binding energy and formation of sigma (σ) bonds between silicon and oxygen atoms shows the strong chemisorption of the molecules on Si-CNT. Further, the density of states analysis clearly illustrate the reduction in the band gap and creation of extra state near the Fermi level, which acts as a catalytic center for adsorption of the molecules. The Mulliken population analysis indicates the charge transfer from Si-CNT to the molecules due to their more electronegativity.

Abstract: There are approximately 45,000 Intermediate Level Nuclear Waste (ILW) containers currently stored in the UK at Sellafield and elsewhere. These stainless steels containers should last up to 150 years of surface storage. In this study the general structural integrity of 500L ILW containers were investigated. The associated degradation issue under ambient conditions known as atmospheric-induced stress corrosion cracking (AISCC) has been studied. Preliminary investigation included profiling of residual stress distribution in parent and weld specimens, atmospheric exposure testing under various salts. So far residual stress profile shows high degree of complexity. No cracks have been observed until this moment in time.

Abstract: Simple mathematical model that describes the lateral vibration of elastically coupled cracked cantilever beams carrying rigid disk at their tips is derived. The derived model is used to study the effect of elastic coupling, crack depth and location on the dynamic characteristics of the system. The cracked beam is presented as two beams connected with torsional spring at the crack location. Model verification is carried out using three dimensional finite element analysis using ANSYS program, the verification results showed good agreement with that obtained from the proposed model. The study reveals that the first system natural frequency is affected by the crack and the elastic coupling.

Abstract: Various designated precipitation hardening and cold working have been employed to improve mechanical properties of aluminum–magnesium–silicon alloys. The aim of this study is to study how both high strength and excellent ductility could be achieved. Two main processes are competing to each other when the cold working is combined with precipitation hardening. They are dislocation annihilation during age treatment which improves ductility; and dislocation pinning by precipitates which increases strength of materials. In this paper, the mechanical properties of cold rolled AA6061 sheets in pre-aging, single and double aging conditions were compared. The different sequences of precipitation hardening and cold working were employed to achieve both high strength and excellent ductility. The results show that the amount of initial cold rolling and pre-aging may have negligible effect on the strength and hardness but significant effect on the ductility of alloy.

Abstract: The formation method of the intersecting hole nozzle, each hole is formed by the converging of two or more child holes, is proposed, for the purpose of accelerating the fuel-air mixing process of direct injection internal combustion engines. In order to examine the macro characteristics of intersecting hole nozzles, three single-orifice intersecting hole nozzles, with the intersecting point of the axes of child holes locating inside, outside, and right at the exit surface, were manufactured. And high speed photography was employed to visualize, thus to quantify the angle and penetration of, the spray from these intersecting hole nozzles in a vessel under ambient room temperature and pressure of 0.1 to 2.0 MPa. The experimental results showed that the spray from intersecting hole nozzles were fan-shaped, which were beneficial for prompting the fuel-air mixing. Particularly, when the intersecting points of the axes of child holes locate right at the exit surface, the longest spray penetration was obtained, and the spray front angle is slightly smaller than side angle. While the intersecting points of the axes of child holes locate inside or outside the exit surface, the spray penetration is shorter, and the spray front angles are extremely larger than side angles under pressure of 0.1 to 2.0 MPa. With the rising of ambient pressure, the differences between front angle and side angle of all the three intersecting hole nozzles become smaller in different degrees.

Abstract: In this paper the free vibration analysis of a fiber reinforced mindlin plate is presented.energy method based on the ritz method is used to obtain natural frequencies of the plate. Displacement fields of the plate are postulated by trigonometric series function. depending on the arrangement and orientation of the fibers, mindlin plate is assumed to be orthotropic or monoclinic.this analysis is useful to study the mechanical behavior of an angle ply lamina and effect of fiber orientation on the frequency response of the plate.the analysis can be extended for the laminates where the analytical solutions are not available. Finally the results are compared with those reported in the literature.

Abstract: This paper discusses the combustion characteristics of CNG under lean and stochiometric conditions in a direct injection engine. The experiments were carried out on a dedicated CNG-Direct Injection engine with 14:1 compression ratio. Combustion characteristics of CNG have been investigated on various injection timings. Injection timing of the fuel injection timing had significant effects on the engine performance, combustion and emissions. The effects became more significant when injection timing was retarded. Injection timing was set after the closing of intake valve and experiments are conducted at 0% and 50% load conditions. Lean stratified operation experiences faster combustion compared to that of stochiometric. In lean stratified operation, there were fast burn rates at the initial stage and slower burning at the later stage. Whereas in stochiometric conditions there is a slightly slower burn at the initial stage and a moderately faster burn at the later stage. The faster initial combustion in lean stratified operation might be due to rapid burn of the initial mixture due to higher turbulence, while a slower burn in the later stage due to diffusion. In contrary to that in stochiometric operations the initial burn is slightly slower, due to moderately strong turbulence and a faster burn due to moderately proceeding mixture. Thus the main effect of fuel injection timing can be explained by the fuel air mixing and the turbulence produced.

Abstract: This paper describes the study of high-speed liquid jets injected in air from an orifice. The main focus is to study the effect of different liquid properties on the characteristics of the high-speed liquid jets injected in ambient air. The high-speed liquid jets are generated by the impact of a projectile, which known as impact acceleration method, launched in a horizontal single-stage power gun (HSSPG). The conical nozzle of 30° angle with the orifice diameter of 0.7 mm was used to generate the jets. The characteristics of high-speed jets were visualized by the high-speed digital video camera with shadowgraph optical arrangement. From the shadowgraph images, the jet formation, atomization, vaporization and shock waves were obviously observed. The maximum averaged velocity of water, alcohol, n-hexane, chloroform and glycerin jets is estimated to be 1,669.03 m/s, 1,548.59 m/s, 1,420.44 m/s, 1,204.46 m/s and 1,496.97 m/s, respectively. That effect on the maximum penetration distance of the water jet is longer than that of all jets. Surface tension and latent heat are the significant physical property for jet formation, while density, kinematics viscosity and heat capacity are not.

Abstract: In this paper, Cubic Interpolated Pseudo Particle Method is proposed to investigate the dynamic behavior of fluid motion in shear lid-driven cavity. The CIP scheme is individually performed to observe the behavior of the fluid motion at varying Reynolds numbers of 100, 400 and 1000. Comparison of the achieved results with the experimental results approves the capability of CIP to establish the sophistication of fluid structure in the system. Although the achieved trajectory had slightly difference but it was almost following the same pattern published in the literatures. The most advantage of this method is that it aims to accelerate processing time as well as higher exponent of accuracy.

Abstract: The noise of interior plastic parts has been one of the major driving factors in the design of automotive interior assemblies. This phenomenon is one of the major contributors to the perceived quality in a vehicle. The noise is caused by interior plastic parts and other parts as a result of permanent deformation. Traditionally, noise issues have been identified and rectified through extensive hardware testing. However, to reduce the product development cycle and minimize the number of costly hardware builds, hardware testing must rely on engineering analysis and upfront simulation in the design cycle. In this paper, an analytical study to reduce permanent deformation in a cockpit module is presented. The analytical investigation utilizes a novel and practical methodology, which is implemented through the software tools, ABAQUS and iSight, for the identification and minimization of permanent deformation. Here, the emphasis is on evaluating the software for issues relating to the prediction of permanent deformation. The analytical results are compared with the experimental findings for two types of deformation location and the qualitative correlation is found to be very good. In this study, we also develop a methodology to design the guide and mount location of cockpit module for minimizing the permanent deformation. Nonlinear finite element analysis has been implemented and integrated with sensitivity-analysis techniques to minimize the permanent deformation at the areas of interest. Finally, we find the optimal guide and mount locations that reduce the permanent deformation.