Computational Methods in Engineering

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Hydroxyapatite coatings have been used on metallic substrates in a variety of applications, including modifying the surface of human implants, bone osseointegration and biological fixation. In this paper, the effects of various kinds of metallic substrate on clinical and pathological results of in vivo tests are presented. Four kinds of endodontic implants i.e, stainless steel, cobalt base alloy, plasma sprayed hydroxyapatite coated stainless steel, plasma sprayed hydroxyapatite coated cobalt base alloy were prapared and implanted in mandibular canine of cats. After a healing period of 4 months, investigation by SEM and histopathological interpretation and evaluation showed significant differences in tissue response and osseointegration between coated and non-coated metallic implants. It was concluded that the results were affected by the kind of metallic substrate . Keywords: Hydroxyapatite coating, Dental endodontic implant, Osseointegration, Corrosion, Stainless steel, Cobalt base alloy

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Zinc-Nickel electrodeposits have been widely adopted for surface treatment of automobile steel sheet for high corrosion resistance. In this work the effect of pulse parameters on the Zn-Ni alloy electrodeposits was investigated. The hardness, thickness, corrosion resistance and composition of deposits thus produced were investigated. The surface topography of the deposits was also observed in SEM and results are reported. It has been shown that the thickness of the pulse electrodeposits was almost even. The hardness in the pulse electrodeposits increased by increasing the on-time period and by decreasing the current density. It was also noticed that increasing the on-time period increases the nickel content of the deposit. Pulse electrodposits had fine structure and the structure become finer by reducung the on-time period and pulse frequency. The corrosion dehaviors of the deposits were then investigated. The results showed that the corrosion resistance of the DC electrodeposits improves in their nickel content increases. Pulse electodeposits show the same behavior, but deposits with about 13% nickel show maximum corrosion resistance.

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The 25Cr-35Ni heat resistant steel has been widely used when resistance to oxidation and creep rapture at elevated temperatures is required. In this paper, the microstructural effect on the weldability of this alloy is investigated. The results of this study indicate that this steel has a perfect weldability in the as cast condition but does not possess good weldability in the aged condition. The as cast microstructure of 25Cr-35Ni steel consists of austenite matrix and a network of primary carbides, while the aged condition consists of austenite matrix and y primary and secondary carbides. The morphological change of primary carbides and the secondary carbides precipitate formation, reducing the elongation and ductility of aged steel, should have enhanced the steel susceptibility to cracking, particularly in the area of the eutectic carbides, and hence, the reduced weldability of the steel. The cracking observed was of the intergranular type and spread along the eutectic carbides. It was found that the carbides in the as cast steel consisted of NbC and M23C6, whereas that of the aged steel also exhibited Ni16Nb6Si7 and M23C6 carbides

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An effective approach for strengthening masonry buildings is to apply shotcrete reinforced with mesh on the surface of the wall. It is not possible to assess the behaviour of coated walls solely using analytical approaches based on simple equations of theory of elasticity without the use of numerical methods. Unreinforcced masonry wall is modelled in this study using the finite element software “ANSYS” to assess the behavior of walls strengthened with reinforced jacket. The accuracy of the model is ensured by calibrating the model against results obtained from laboratory tests. Then the calibrated model is generilized to model the strengthed wall and, finally, the analytical results obtained from masonry walls and strengthed walls are compared and evaluated.

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Although studies on RC beams under shear have a history record of more than 100 years, many important issues in this context still remain that have evaded attention. The aim of the current study is to study a number of these less investigated aspects of the behavior of RC beams under shear. For this purpose, and based on the modified compression field theory, a computer program has been written to study the effects of transverse and longitudinal steel reinforcement and shear span, a/d, on the behavior of RC beams under shear. The results show that the shear capacity of the beam cannot be increased beyond an optimum amount of transverse steel ratio. This paper will try to provide a precise definition of this optimum transverse steel ratio. Another finding of the present study is that increasing tensile longitudinal steel ratio increases the amount of the optimum transverse steel ratio, while increasing a/d decreases the optimum transverse steel ratio.

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Diagonal Strap bracing is one of the most applicable lateral bracing systems in light steel framing (LSF). In practice, one or more panels of Gypsum Wall Boards (GWBs) is used for the cladding of strap braced frames. Usually, the effect of these GWBs in modelling and design is neglected by designers, but this effect can affect the seismic performance of the system In this paper, firstly, a simple numerical method is developed to model the monotonic and cyclic behavior of cold-formed strap braced shear walls together with GWBs. Then, the effects of GWB on the lateral characteristics and seismic performance levels of shear walls are evaluated. It is found that neglecting GWB in the lateral design or modeling of LSF is not rational and GWB can increase the dissipation of earthquake energy, lateral strength and stiffness of the walls. Also, the shear wall composed of strap bracing and SWBs reaches a certain performance level in a less drift ratio in comparison to to only strap braced system