Advanced Materials Research Vols. 488-489

Abstract: Effect of grain size on microstructure, transformation characteristics and shape recovery has been studied in Fe-24%Mn-4%Si-5%Cr-5%Co shape memory ribbons fabricated by melt spinning. Mean grain size of the ribbons could be controlled by wheel speed; in case of ribbon manufactured in the wheel speed of 10 m/sec, mean grain size was more or less 20 μm, while the mean grain size in 50 m/sec was about 1 μm. Thermal ε-martensite in the shape of plate could be observed in austenite matrix and the volume fraction of that decreased in smaller grains because of grain constraint. As a grain size decreased, one-way and two-way shape recoveries were increased. A change in shape recovery of ribbons was closely related to deformation mode i.e., transformation-induced plasticity or slip according to grain size; it could be confirmed that reversible ε-martensite was induced in preference to irreversible slip in the ribbon with smaller grains during deformation by X-ray diffractometry. Not like in bulk specimen, ε-martensite being very thin in the width of 10 ~ 20 nm and lots of stacking faults being inferred from streaks of SAD patterns, were revealed in melt-spun ribbons manufactured in the wheel speed of 50 m/sec.

Abstract: This investigation studies the effect on pressure of the filling volume rate in a manufactured nickel powder capillary structure (wick) for a loop heat pipe (LHP). The filling volume ratio is an index of pressure from 1 to 1.3 to investigate the influence on filling weights of the internal parameters of a wick (permeability, effective pore radius and porosity) and heat transfer performance for LHP. The wick is manufactured, based on the standard and non-pressurized filling weights in the manufactured wick mold. The conversion of a pressure change to a weight change used to investigate the relationship between the change in filling volume of pressure to the internal parameters of the wick and the heat transfer performance. As the filling volume rate increases, the capacity of the wick increases, but an excessive filling volume rate makes the wick too dense, affecting its permeability and heat transfer performance in LHP. An experimental test demonstrates that the permeability and heat transfer performance are optimal at a filling volume ratio of 1.2.

Abstract: The butt joints of semi solid 356 were produced in as cast conditions by friction stir welding process (FSW). This experiment studied in pre/post heat treatment (T6) using the welding speed 160 mm / min with tilt angle tool at 3 degree and straight cylindrical tool pin. The factors of welding were rotating speed rates at 1320, 1750 rpm and heat treatment conditions. They were divided into (1) As welded (AW) joints, (2) T6 Weld (TW) joints, (3) Weld T6 (WT) joints, (4) T6 Weld T6 (TWT) joints, (5) Solution treated Weld Artificially aged (SWA) joints and (6) Weld Artificially aged (WA) joints. Rotating speed and heat treatment (T6) condition were an important factor to micro, macro structure of metal and mechanical properties of the weld. Increasing rotating speed and different heat treatment condition impacted onto tensile strength due to the defects on joints. Therefore the optimum welding parameter on joint was a rotating speed 1320 rpm, the welding speed 160 mm/min, heat treatment condition of Weld T6 (WT) which obtained the highest tensile strength 228.92 MPa, as well as, highest hardness of 98.1 HV

Abstract: In this work, the consolidation of different alumina particles via sintering process was conducted to the compacted alumina pellets. This consolidation was also assisted with the sintering aid, MgO to densify the final ceramic structure. Comparison between the influence of additive to the different particles size of compacted alumina by observing the microstructure and physical properties was conducted. The value physical properties and microstructure clearly show that for both particle size of alumina, MgO additive can increase the density value and improve microstructure properties.

Abstract: In order to solve the severe wear problem of the core in water hydraulic high-speed on/off valve, according to the requirements of high-speed on/off valve components in water hydraulic transmission and from the practical standpoint, the core manufactured with ceramic materials could bring its advantages of high strength, big hardness, good wearability, non-affection with corrosion into play.By the wear-resisting experiment the wear case of Si₃N₄ ceramic core has been studied with weight-loss method by electronic analysis balanc.The results show that the core manufactured with Si₃N₄ has high abrasion resistance and low wear rate, and the structure design of water hydraulic high-speed on/off valve with ceramic core is reasonable and the performance is good.

Abstract: Friction stir welding is a technique useful for joining aluminum alloys that are difficult to weld. In recent years, however the focuses has been on welding dissimilar aluminum alloys, and analyze their mechanical properties and micro-structural characteristics. In the present study, the less investigated welding of cast aluminum alloys is considered. Cast aluminum alloys, A356 and A413, commonly used in automotive and aerospace industries, were friction-stir welded and their mechanical properties and micro-structural characteristics were analyzed. On testing their welded region, no welding defects were observed. The welded region exhibited a maximum tensile strength of 90 N/mm² and Vickers micro-hardness of 56.8. The micro-structural observations at the nugget region revealed a refined grain structure.

Abstract: In this paper, the effect of quench probe diameter on the heat transfer rate during immersion quenching of stainless steel (SS) probes in still water has bee studied. Quench probes of different diameters with an aspect ratio of 2.5 were prepared from SS. These probes were heated to 850 °C and then quenched in water. Time-temperature data were recorded during quenching. The surface heat flux and temperature were estimated based on the inverse heat conduction (IHC) method. The results of the computation showed that the different cooling regimes during quenching in water were significantly affected by the diameter of the quench probes. The peak heat flux was higher for the probe having larger diameter followed by the next larger diameter probes.

Abstract: Failure analysis of one-ply thin-walled hemispherical GRP dome internally pressurized was checked via analytical approach and finite element simulations using ABAQUS and MATLAB software. Tsai-Wu failure criterion was employed during analysis. The failure factor against changes of dome’s geometrical parameters was investigated. Subsequently, laminated hemispherical GRP dome failure behavior was theoretically analyzed using MATLAB software. During the analysis some geometrical parameters were assumed to be constant. Moreover, symmetrical laminations were taken into account. The Tsai-Wu failure factor was checked based on changes of applied internal pressure, ply thickness, dome’s internal radius and ratio of dome’s internal radius over ply thickness. The behavior was determined to be linear and quadratic both.

Abstract: The superior feature of composites such as high stiffness against low density have impelled engineers to use this material in automotive, aerospace and building industries. In the past few decades, composites shell has found applications in storage tanks and transmission pipelines. Designing laminated composite shells is challenging because of the complex mechanical behavior when combining laminate and shell theories. In this paper, the study is focused on the effect of lamina thickness on performance of the GFRP cylinder. For this purpose two 12-ply GFRP cylinders are considered with ply sequences of [0/90/45]s. The lamina thicknesses of the composite shell are assumed to be 0.1, 0.5, 1 and 1.5 mm, to evaluation of the mechanical behaviors of the cylinders and identifying one with the highest strength. The 250 mm diameter cylinders are subjected to a uniform radial patch load. A code is written for the solution based on the shell theory and classical mechanics of laminated composite using MATLAB software. The results are validated by comparing the present results with those found in literature. A good correlation justifies the study being extended to include the study on the effect of ply and shell thickness. The procedure is recommended for design and optimization for strength of various sizes of composite pipes

Abstract: To date, the highest pump pressure available in market is 648 MPa from FLOW International Corp. Cutting with ultra high pressure reduces abrasive usage, faster cutting speed, increased depth of cuts and increase efficiency. This research explores the possibility of applying pressure exceeding 1000 MPa to push pure water to cut solid objects. 10 grams of PE4 explosives are exploded in a confined chamber with a rectangular opening. Simulations in designing the blast test jig are discussed. Simulations are done using Autodyn software. The simulation aims to get the optimum geometry that can give the highest pressure at nozzle exit. Two materials are chosen to cut; stainless steel 304 and aluminum 1100. Simulations show the optimum blast test jig can cut aluminum and stainless steel at certain thickness.