Advanced Materials Research Vol. 445

Abstract: This research was aimed to synthesize calcium carbonate nanoparticles from CaCl₂, NaCl and Na₂CO₃ precursors by mechano-chemical route without any subsequent heat treatment of the as-milled powder. Effects of intensive milling duration and amount of NaCl as a diluting agent on the powder particle characteristics have been investigated. XRD results showed that CaCO₃ nanoparticles were obtained after 30 minutes of continuous milling in the planetary ball mill regardless of the amount of NaCl. Further milling up to 10 hour resulted in peak broadening indicating the crystallite refinement. For the 10-hour milled sample in the presence of 3.5 mole% NaCl, the mean crystallite and particle sizes were 12 and 56 nm, respectively. Those values decreased slightly when the amount of NaCl increased from 3.5 to 10.3 mole%.

Abstract: This paper aims to evaluate the machinability of a novel composite material which is textile fabric reinforced composite. In this study, four different cutting tools with different geometries were used due to the lack of information on tool selection for thermoplastic matrix composites. During machining of this novel composite, the fixture design is essential due to the very low elastic modulus of composite plates about 0.5 GPa. After designing special milling fixture, tests were performed in two limit values of cutting parameters, cutting speed and feed rate. Cutting force results, chip and burr formation were evaluated to determine suitable tool and cutting parameter selection.

Abstract: For the improvement of the deformation characteristic and the energy absorption efficiency of the tubular structure at impact event, a method generating the first buckling lobe using the inertia force was investigated. The solid block was attached to the wall so that its inertia force causes the partial plastic deformation that plays a role of the trigger of progressive buckling at the beginning of impact. Drop-weight impact experiment revealed that the onset of progressive buckling was achieved at the desired portion by the method. To increase the variety of tube shapes, numerical examination was conducted with the dynamic explicit finite element method. Long straight and S-curved tubes, which have square cross-section, were numerically modeled with shell elements. They were assumed to be impacted to the rigid wall to estimate the dynamic collapse behavior. The first buckling lobe generated by inertia force was demonstrated for the straight tube. The S-curved tube exhibited a bending collapse mode without the method. However, such mode was avoidable by applying the method. Then the energy absorption efficiency of the tube was drastically increased.

Abstract: Chlorinated-PVC (CPVC) pipes are used extensively for water supply pipes, wastewater, and gas distribution. They are desired for their quick installation, durability and strength. CPVC is a heat resistant type of plastic that welds, bends and shapes easily. Its utilization in harsh environmental conditions requires an understanding of weathering effects on its mechanical properties. In this work, the effect of dry heat on the tensile properties of CPVC is studied using artificial weathering procedures. CPVC specimens were prepared according to ASTM standard D 638 and exposed to accelerated dry heat temperature to simulate natural weathering effects of long term outdoor exposure. Tests were performed at two different temperatures of 40^o C and 70^o C for duration up to 3000 hours. Stress-strain curves were developed for this material and weathering effects on the tensile strength, modulus of elasticity and strain at fracture were obtained. The results of this investigation show that the ultimate tensile stress and the fracture stress exhibit a slight increase over the period of the exposure. The modulus of elasticity was not affected by the exposure while the fracture strain decreases slightly at the beginning of the exposure and remains constant for the remaining period of the exposure.

Abstract: Permeability and green compression strength are among the important mechanical properties and considered much in the sand casting mould preparation. These molding sand properties play a vital role in determining the optimum moisture content for making green sand casting mould. Tailing sand is the residue mineral from tin extraction, which contains between 94% and 99.5% silica and in abundance in Kinta Valley of state of Perak, Malaysia. In this research work, samples of tailing sands were gathered from four identified ex tin mines located at the Perak State, Malaysia. They were investigated by the standards and testing procedures prescribed by the American Foundrymen Society (AFS). Sand specimens of size Ø50 mm×50 mm in height from various sandwater ratios bonded with 4% clay were compacted on applying three ramming blows of 6666 g each by using a Ridsdale-Dietert metric standard rammer. The specimens were tested for green compression strength using Ridsdale-Dietert universal sand strength machine and permeability number with Ridsdale-Dietert permeability meter. Before the tests were conducted, the moisture content was measured using moisture analyzer. Samples with moisture content ranging from 3 to 3.5% were found to have optimum working range with effective green compression strength and permeability.

Abstract: Electro-chemical discharge machining (ECDM) is one of nontraditional processes for micro-fabrication of non-conductive materials. A high applied voltage is preferable to form a gas film and to generate discharge in the film. However, accumulation of discharge heat often causes cracks of the surface because non-conductive materials have low heat conductivity. In this study, the effect of ultrasonic vibration and the electrolyte level on the performance of gravity-feed drilling by ECDM was investigated. Ultrasonic vibration was applied to a glass plate. A tungsten rod as a tool electrode was fed by gravity. Ultrasonic vibration changed the discharge behavior and improved electrolyte circulation. Although high amplitude ultrasonic vibration caused very dense and wide current pulses consistently during machining process, it decreased removal rate significantly. In addition, electrolyte levels affect single bubble size and the resistance in the electrolyte. Low electrolyte level will cause higher resistance, and higher temperature of the tool electrode and workpiece. A high bias current flew at a low electrolyte level without ultrasonic vibration. In this case, removal rate decreased and surface integrity was improved.

Abstract: Systematic design is an effective methodology which generates possible designs and eliminates them in a step by step manner. The methodology allows designers to generate sub modules and creates relationships or network between these modules to form to functional structure of the design. Due to its capability of reducing development time and that of satisfying customer requirements it has wide application areas. Height adjustment mechanisms for consumer goods industry are special interest for designers and have limited application area due to fact that such kind of mechanisms cannot totally meet customer requirements and they may be too complex to manage. So, different techniques or approaches must be employed to design a specific mechanism for height adjustment. Systematic design approach is employed in this study to produce potential design proposals together with their driving mechanisms for height adjustable refrigerator foot. First stage of systematic approach employed in this study is definition of the height adjustment problem and design requirements. A wide patent research is then completed to seek for existing solutions. Subsystems and functional structure of height adjustment problem arc then formed using "Technical Process Flow" and "Functional Structure Chart". "Morphological Matrix" is created to illustrate each process step and types of design proposals. Last stage is to evaluate the generated design proposals according to the systematic design philosophy to create a novel conceptual design to be patented. Finally, the novel design produced has been manufactured with rapid prototyping technology for further evaluations.

Abstract: The objective of this work is to study the stress-strain responses of ultra high molecular weight polyethylene (UHMWPE) under uniaxial and biaxial cyclic loading through systematically conducting experiments and model simulations. Experiments involved prescribing axial, strain and stress controlled, cycles to the specimens of UHMWPE. Since the ratcheting strain and its accumulation rate are sensitive to the mean (or steady) and amplitude stresses of the prescribed loading cycles, these parameters were varied in the experiments conducted. The viscoplasticity theory based on overstress (VBO) [ was implemented to simulate the cyclic and ratcheting responses of UHMWPE. Kinematic stress is the main state variable in constitutive models which affect cyclic behavior and the ratcheting. Therefore, different kinematic hardening laws such as Prager, Frederick-Armstrong, Burlet-Cailletaud, Ohno-Wang and Chaboche, are used to investigate ratcheting behavior of UHMWPE. The experimental and VBO simulated responses are compared to demonstrate the current state of the simulations and future model development needs.

Abstract: Fused deposition modelling (FDM) is one of the rapid prototyping (RP) processes that build part of any geometry by sequential deposition of material on a layer by layer basis. Unlike other RP systems which involve an array of lasers, powders, resins, this process uses heated thermoplastic filaments which are extruded from the tip of nozzle in a prescribed manner. Present work focuses on extensive study to understand the effect of five important parameters such as layer thickness, part build orientation, raster angle, raster width and air gap on the sliding wear of test specimen built through FDM. The study provides insight into complex dependency of wear on process parameters and proposes a statistically validated predictive equation. Microphotographs are used to explain the mechanism of wear. Finally, the predictive equation is used to find optimal parameter setting through bacteria foraging optimization algorithm (BFOA).

Abstract: This paper describes the processing and characterization of a new class of epoxy matrix composites reinforced with short fibers obtained from the scales of a fresh water fish (Labeo rohita). The functional groups involved in the formation of the resulting composite are identified. Fourier Transform Infrared (FTIR) spectroscopic analysis shows that the formation of hydrogen bonds occurring at the fiber-matrix interface between the oxygen atom of the epoxy and hydrogen atom of the polypeptide chain of fish scale is responsible for the formation of this new class of composites. These composites possess improved micro-hardness and exhibit tensile and flexural strengths marginally different from those of neat epoxy. These composites are expected to find applications as potential materials for conveyor belt rollers, pipes carrying pulverized coal in power plants, pump and impeller blades and also as low cost housing materials.