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[en] Nickel-titanium is one kind of smart material alloy; it is capable to regain its earlier shape when heated. The machinablity constraints arises with the use of conventional machines while machining of NiTi alloys such as high tool wear, adverse chips, formation of burr after machining and grinding. To overcome these difficulties non-conventional machining process, electrical discharge machining (EDM) are used. In this research, the effect of process parameters such discharge current (A), gap Voltage (V), pulse on time (Ton) and pulse off time (Toff) on the performance parameters like material removal rate (MRR), surface roughness (SR) and white layer thickness (WLT) has been investigated for NiTi60 (Smart Material Alloy). Design of Experiments was conducted by Taguchi’s method by considering orthogonal array of L27 and using Minitab software. The process parameters set during the performance of experiments are Current −4, 6, and 8 A, Voltage −40, 55, and 60 V, pulse on time 20, 40, 60 μs, and Pulse off time 5, 7, 9 μs. The corresponding performance values obtained for MRR was 0.155 to 1.24 mm3 min−1, SR was 1.597 to 7.474 and WLT was 5 to 20 μm. Process parameters of optimum settings are developed for each performance parameters and based on these optimum setting confirmation test were conducted which shows that, the percentage of error obtained for material removal rate was 7.63%, 2.49% for surface roughness and 2.86% for white layer thickness. (paper)
[en] Most commonly, a specimen for microscopy is seen as proper if it doesn't have any scratches. However, the fact is that this is very often wrong and thus another criteria for a proper specimen must be found. By defining specimen preparation as sequences of abrasive processes with finer and finer abrasives to remove the damage created by the former step, we are able to obtain scientifically correct procedures to obtain structures, which give a high probability of presenting the 'true inner material' or true structure. Copyright (2003) Australian Microbeam Analysis Society
[en] A new yet classical approach of powder sample introduction into the inductively coupled plasma is presented. Internal standards were added to powder samples in solution form. The dried powder samples were dispersed using a high speed Ar stream in a custom-made powder dispersion device (PD). The construction and analytical performance of PD are described. Calibration curves are linear around 3 orders of magnitude for a set of synthetic geological standards. Curves of intensity ratio versus concentration for another set of certified reference materials of geological sediments with different matrices among the standards are obviously scattered. Possible errors in PD-ICP analysis are discussed. A strategy of sample preparation using wet-grinding to overcome such errors is proposed.
[en] The planar-cam type pick-and-place device can clearly and effectively achieve the desired curvilinear motion of its end effector, and it can be designed and fabricated easily. By employing the concept of velocity instant center, the cam profiles, the paths of cutters, the pressure angles and the radii of curvature of the dual cams of the planar-cam type pickand- place device can be expressed parametrically. The cam profiles may have concave portions, and each minimum radius of curvature of the concave portion of the dual cam profiles is the upper bound of the grinding-wheel radius that may not cause undercutting
[en] The change in effective grinding power with change in the grinding fluid is studied experimentally, in fixed machining conditions. A method is proposed for assessing the life of the wheels. This method facilitates the choice of the tool, grinding conditions, and composition of the grinding fluid.
[en] Several machines, such as crushers use the physical effect of compression to cause fragmentation 'crushing' of brittle rocks. As a consequence of the complex fragmentation process, crushers are still sized by empirical approaches. This paper present the results of a numerical study to understand some aspects of rock crushing phenomenon in terms of energy consumption. The study uses the discrete element approach of PFC2D code to simulate a stamp mill. The stamp mill has a simple crushing mechanism of a fixed kinetic energy delivered by a rigid ram impact. A single rock fragment crushing process dependent on the number of stamp mill ram blows is numerically examined. Both amount and type of energy generated by a ram blow are monitored besides the type of fractures generated. The model results indicate that the ram impact energy is mainly consumed in form of friction energy (up to 61 %) while strain energy stays at about 5 % of delivered energy. The energy consumed by crushing the rock represents only 32 % to 45 % of stamp mill energy and tends to decrease as the number of impacts increases. The rock fragmented matrix tends to convert into more friction energy with reduced number of new fractures as number of blows increase. The fragmentation caused by tensile is more often compared to those caused by shear, this behaviour increased with increasing number of ram blows. (orig.)
[en] A laser dressing is an effective dressing method to accomplish efficient ceramic grinding. Since laser dressing achieves protrusion heights of abrasive-grains without grain dislodgment, the number of abrasive-grains in a laser dressed grinding stone (LGS) is higher than that in a mechanically dressed grinding stone (MGS), remaining the initial grain distribution. Thus, the LGS contains higher number of effective cutting edges, and forms higher number of ground grooves on a ground surface than the MGS. Consequently, the LGS can achieve lower specific grinding energy than the MGS. Copyright (2003) AD-TECH - International Foundation for the Advancement of Technology Ltd
[en] Influence of fixture on the errors of a machined surface can be very significant. The machined surface errors generated during machining can be measured by using a coordinate measurement machine (CMM) through the displacements of three coordinate systems on a fixture-workpiece pair in relation to the deviation of the machined surface. The surface errors consist of the component movement, component twist, deviation between actual machined surface and defined tool path. A turbine blade fixture for grinding operation is used for case study
[en] We applied combined response surface methodology (RSM) and Taguchi methodology (TM) to determine optimum parameters for minimum surface roughness (Ra) and vibration (Vb) in external cylindrical grinding. First, an experiment was conducted in a CNC cylindrical grinding machine. The TM using L27 orthogonal array was applied to the design of the experiment. The three input parameters were workpiece revolution, feed rate and depth of cut; the outputs were vibrations and surface roughness. Second, to minimize wheel vibration and surface roughness, two optimized models were developed using computer aided single objective optimization. The experimental and statistical results revealed that the most significant grinding parameter for surface roughness and vibration is workpiece revolution followed by the depth of cut. The predicted values and measured values were fairly close, which indicates 2 ( 94.99 R2Ra=and 2 92.73) R2Vb=that the developed models can be effectively used to predict surface roughness and vibration in the grinding. The established model for determination of optimal operating conditions shows that a hybrid approach can lead to success of a robust process
[en] This paper presents the deformation behavior and crash worthiness of electric resistance welded mild steel tubes with axial gradient microstructures in quasi-static compression. Three sets of tubes were prepared, and regions of each tube were Induction heated and directly quenched (IH-DQ). The effect of the length to diameter (L/D) ratio, and length of the IH-DQ region on crushing characteristics was investigated, and compared with untreated tubes. The compression tests revealed that improved energy absorption can be obtained in IHDQ tubes if the collapse is controlled by the formation of a concertina buckling mode. However, there was a tendency to produce mixed or Euler buckling modes as the ratio of L/D increased. Meanwhile, the results of the crush experiments and the FEM models showed that the heat-treatment process should be precisely controlled to produce the correct type of microstructure, and circumferential uniformity of microstructure distribution.