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Structural Modifications in Semi Solid Processed LM4
Issue:
Volume 2, Issue 3, June 2013
Pages:
29-31
Received:
21 May 2013
Published:
20 June 2013
Abstract: This paper presents a report on the study of structural modifications LM4 processed by semi solid metallurgy. This was with the view to determine effects of degree of cold work, thermal treatment temperature and soaking time on the structural formations in the alloy. LM4 alloy was prepared and cast in sand mould into rods of diameter 12 mm and 200 mm in length. The cast rods were then heated to different temperatures which fall within the slurry region of the alloy. The heated samples were soaked at these temperatures for various times. There was also a set of non-treated control samples. The thermally treated rods were subjected to various degrees of cold work after which the metallographic examination of the samples was carried out. The observed microstructure of the alloy showed significant modifications.
Abstract: This paper presents a report on the study of structural modifications LM4 processed by semi solid metallurgy. This was with the view to determine effects of degree of cold work, thermal treatment temperature and soaking time on the structural formations in the alloy. LM4 alloy was prepared and cast in sand mould into rods of diameter 12 mm and 200 ...
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Cylindrical Space Fourier-Bessel Mode solver for Maxwell’s Wave Equation
Robert Claude Gauthier,
Mohammed Alzahrani
Issue:
Volume 2, Issue 3, June 2013
Pages:
32-35
Received:
18 May 2013
Published:
30 June 2013
Abstract: A Fourier-Bessel basis set in cylindrical coordinates is used to cast Maxwell’s wave equations into an eigenvalue problem from which the steady states of rotationally symmetric photonic structures can be determined. The rotational symmetry of the structure significantly reduces the order of the matrix making an efficient computation process that can be accommodated by desk top computers running MATLAB ©. In addition the matrix can be tuned to a particular mode profile type such as monopoles, dipoles, … enabling the user to target the desired mode features in the computations. The technique is applied to solving for the states of three different photonic structures; 12-fold quasi-crystal, silicon ring resonator and photonic crystal fiber. The particular features of a modal state are easily obtained by examining the eigenvector.
Abstract: A Fourier-Bessel basis set in cylindrical coordinates is used to cast Maxwell’s wave equations into an eigenvalue problem from which the steady states of rotationally symmetric photonic structures can be determined. The rotational symmetry of the structure significantly reduces the order of the matrix making an efficient computation process that c...
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Hybrid Effects on Tensile Properties of Carbon/Glass Angle Ply Composites
GuruRaja M N,
A. N. HariRao
Issue:
Volume 2, Issue 3, June 2013
Pages:
36-41
Received:
15 May 2013
Published:
10 July 2013
Abstract: Hybrid composites are considered materials of great potential for engineering applications. One advantage of hybrid composite materials for the designer is that the properties of a composite can be controlled to a considerable extent by the choice of fibers and matrix and by adjusting the orientation of the fiber. The scope for this tailoring of the properties of the material is much greater, however, when different kinds of fiber orientations are incorporated in the same resin matrix. For the study of potential of these materials, in this work specimens were prepared with different angle ply orientation of carbon /glass hybrid with epoxy resin as an adhesive. Three orientations viz 0/90, 45/45 and 30/60 were considered for studies. Mechanical properties such as tensile strength, tensile modulus, & peak load of the hybrid composites were determined as per ASTM standards. Vacuum bagging technique was adopted for the fabrication of hybrid specimens. It was observed that angle ply orientation at 0/90 showed significant increase in tensile properties as compared to other orientation. Scanning electron micrographs of fractured surfaces were used for a qualitative evaluation of interfacial properties of woven carbon–glass hybrid composites. These results indicated that carbon –glass hybrid composites offered the merits of synthetic fibers.
Abstract: Hybrid composites are considered materials of great potential for engineering applications. One advantage of hybrid composite materials for the designer is that the properties of a composite can be controlled to a considerable extent by the choice of fibers and matrix and by adjusting the orientation of the fiber. The scope for this tailoring of th...
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Influence of Negative Poisson's Ratio on Stent Applications
S. K. Bhullar,
A. T. Mawanane Hewage,
A. Alderson,
K. Alderson,
Martin B. G. Jun
Issue:
Volume 2, Issue 3, June 2013
Pages:
42-47
Received:
6 June 2013
Published:
20 July 2013
Abstract: Stents are usually defined as small tubular structures that are inserted into the diseased region which provide mechanical support of damaged artery or some other hollow organ to restore lumen and blood flow conditions in arteries. Recently developed stents may accumulate functions; for example, they can be used for drug delivery or for treatment of bleeding esophageal varices. Further clinical failures such as crushing, removing, restenosis are some of the most serious reasons for continuing stent improvements. Therefore, our research study has the design and manufacture of an auxetic structure with enhanced mechanical properties through the tailored negative Poisson’s ratio, and its configuration as an auxetic stent to be used for example in the palliative treatment of esophageal cancer and for the prevention of dysphagia as the main objective. Background: The use of stents for esophageal diseases has evolved greatly over the past 30 years. Esophageal cancer is the growth of cancer cells in the esophagus tube which usually originates in the inner layers of the lining of the esophagus and grows outward. In time, the tumor can obstruct the passage of food and liquid, making swallowing painful and difficult. Since most patients are not diagnosed until the late stages of the disease, esophageal cancer is associated with poor quality of life and low survival rates. Method: This research study is organized in three parts devoted to fabrication of auxetic structure and stent samples, experimental testing and discussion of results. For this purpose a model of an auxetic rotating-square geometry with a circular hole structure is developed by laser cutting apolyurethane sheet. The auxeticoesophageal stent was made by folding and gluing the auxetic sheet (with rigid squares and circular holes) into a cylindrical shape. Combined videoextensometry with compressive and tensile testing are employed to determine the deformation response of the auxetic sheet and stent to obtain stress-strain curves and estimation of Poisson’s ratio.Conclusions: The stenting outcomes are improved through mechanical design with tailored negative Poisson’s ratio through cell geometry of the esophagus stent. Theauxetic stent geometry of rotating squares with circular holes will be lighter in weight; reduces obstruction and food impaction because of its unique deformation mechanism; and can reduces migration of the implant stent by embedding inside the tissue.
Abstract: Stents are usually defined as small tubular structures that are inserted into the diseased region which provide mechanical support of damaged artery or some other hollow organ to restore lumen and blood flow conditions in arteries. Recently developed stents may accumulate functions; for example, they can be used for drug delivery or for treatment o...
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