Applied Mechanics and Materials Vols. 446-447

Abstract: uminium metal matrix composites (AMMC) reinforced with SiC particulate are one of the familiar materials which are widely used in automobile, mining, etc. due to their superior properties such as high stiffness, low density, good corrosion resistance etc. this paper presents an effective approach for the optimization of process parameters during dry sliding wear test with multiple response characteristics based on Taguchis method with grey relational analysis. Taguchis L₉ orthogonal array has been used for experimentation. The process parameters such as weight fraction of reinforcement, precipitation temperature, load and disc speeds are optimized with multiple responses such as wear and coefficient of friction. Response tables, grey relational grade and ANOVA are used for the analysis and conclude that all the process parameters influence the wear performance of the composite at significant level but the level of influence differs significantly with respect to the size of the reinforcement particle in the composite. Precipitation temperature and disc speed have less influence for lower size particle whereas they become significant for higher size particle.

Abstract: In the present work, the influence of shoulder diameter, traverse speed, and rotational speed on the formability of friction stir welded sheets made between sheets of AA6061T6 and AA5052H32 Al alloys has been studied. In-Plane Plane-Strain formability tests are conducted for this purpose. It is understood from the results that the formability of welded sheets can be improved by optimizing the welding and tool parameters. A larger shoulder diameter, higher traverse speed, and lower rotational speed are favorable for improved formability, and strain hardening exponent of weld region. This is due to the fact that the heat input and subsequent microstructure evolved depends on the heat input, which depends on the welding parameters.

Abstract: Mixed phase TiO₂ thin films of rutile and anatase type crystal orientations were deposited on Si substrates by pulsed laser deposition (PLD) technique. When annealed at 800°C at 1 mbar oxygen pressure for 3 h, the deposited films transform into a single phase of rutile type. Structural and morphological studies of the as-deposited and annealed films were performed with X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), Raman spectroscopy, and atomic force microscopy (AFM). Photoluminescence (PL) spectroscopy was used for optical characterization of the annealed thin films.

Abstract: The present research paper aims in evaluating the strength of the welded AA6351 alloy plates of 6 mm thick by using friction stir welding technique at different rotational speeds The applied welding technique is capable of achieving the mechanical properties of the alloy close to that of the original alloy. In the present investigation, the speeds of the spindle were varied from 1100 rpm to 1500 rpm with a constant transverse speed of 20 mm/min. The tensile strength of the joints is determined by an universal testing machine. The results from the present investigation show that the values of the yield strength were very much closer to the values of the AA6351Alloy prior to welding. It has been found from the experiments that the strength of the joints increases with the increase in the rotational speed; however, the same is decreasing after achieving certain speed.

Abstract: Glass Fiber Reinforced Plastics composites have an increased application in recent days, due to its enhanced structural properties, Mechanical and thermal properties. Drilling of holes in GFRP becomes almost unavoidable in fabrication. The heterogeneous nature of this kind of materials makes complications during machining operation. However, drilling is a common machining practice for assembly of components. The quality of holes produced in the GFRP material is severely affected by surface roughness, Circularity, Delamination, etc. The objective of the study is to apply the full factorial design and Fuzzy logic model to achieve an improved hole quality considering the minimum Circularity error through proper selection of drilling parameters. The experimental investigation values are compared with predicted fuzzified values and found that they are in good correlation with each other.

Abstract: In recent years, natural fibers become an attraction to all people especially for researcher, scientist and engineer because natural fibers can be as substitute candidate for synthetic fibers. Due to their characteristics which are cheap, lightweight, less damage to processing equipment, renewable resources, and also good relative to mechanical properties, they are made to challenge the conventional fibers like glass and carbon. The purpose of this study is to investigate on mechanical properties of binderless boards from kenaf fiber. For hot pressing process, there are two required parameters need to be change. There were temperature and pressure that changed which for temperature were at 120 °C, 140 °C and 160 °C. For pressure, there were changed at 4 ton, 6 ton and 8 ton. Density, flexural and tensile test were conducted on the sample. Morphological analyses were done using Scanning Electron Microscope (SEM). From the result obtained, the maximum value of tensile stress was at specimen 8 ton at 140 °C which is 7.4 MPa and the flexural properties are 44.6 MPa. The changes of mechanical properties corresponding to the various temperatures and pressure during specimen preparation had been obtained.

Abstract: In this paper, the effect of holes on dynamic behavior and energy absorption of aluminum alloy AA7005 tubes in T6 is investigated numerically. True stress-plastic strain curves from the tensile test are used in the static simulation of AA7005 tubes. The deformed modes from the numerical simulation are compared between tube with and without holes under drop velocity of 7 m/s and 15 m/s. Energy absorption values and peak loads with and without holes are compared to develop the understanding on the effect of drop velocity on the crush behavior of tube.

Abstract: Conventional honeycomb structures show positive Poissons ratio under in-plane loading while Auxetic honeycombs show negative Poissons ratio. Accordion, Hybrid and Semi re-entrant honeycomb structures show zero Poissons ratio, i.e. they show zero or negligible deformation in lateral direction under longitudinal loadings. In this paper an FEA analysis of these three types of structures is made using commercial software ANSYS^R 14 using 8 node 281 shell elements. Cell wall thickness and cell angle is varied to analyze their effect on elastic modulus E_x and global strains along X direction under X-direction loadings. E_y is also analyzed to measure lateral stiffness and deformation behavior of structure for its potential application as flexures.

Abstract: Porous Copper (porous Cu) with varying porosities was prepared using sodium chloride (NaCl) particles as space holder through powder metallurgy route. Pre-alloyed copper that was used as a feedstock material were mixed with the varying proportion (0%, 20%, 40% and 60% of volume fraction) of laboratory grade NaCl prior to hot compaction. The green compacts were subjected to water leaching process in order to remove NaCl particles and consequently being sintered at 850°C. The resultant porous Cu were examined in terms of density, porosities, microstructures and dimensional changes. The effect of space holder on the occurrence of pores in sintered article was investigated. It was found that the amount and shape of the space holder particle greatly affect the percentage of porosities and the shape of the pore of the sintered article.

Abstract: In the reported research, a subject-specific multibody dynamics model was proposed to predict impact force induced in lateral fall of the elderly. Parameters such as anthropometric dimensions, segment masses, mass center, and mass moment of inertia that are required for constructing the dynamics model were extracted or calculated from a whole body DXA image of the subject. Governing equations of the fall process were established and computer codes were developed for solving the equations. The dynamics model was then validated by a controlled fall test using young volunteer. Good agreements between predicted and experimental results were observed, indicating that the proposed dynamics model has the capability to predict subject-specific impact force induced in fall.