Mechanical Engineering

Present investigation is on aluminum alloymetal matrix composite reiforced with aluminum oxide fibers in varying percentage like 10%, 20% and 30% and so on. The casting can be produced by using familiarized process i.e. Squeeze casting method, in this investigation we are using Aluminum and Copper as a base metal and aluminum oxide fibers as an a reinforcement. During this investigation we are going to study the wear behavior of the produced components and the result obtained from the investigation shows that the wear behavior enhances by expanding aluminum oxide and the valuable in the commercial enterprises such as automotive and aerospace.

The plane elasticity problem studied is of a circular inclusion having a circular arc-crack along the interface and a crack of arbitrary shape in an infinite matrix of different material subjected to uniform stresses at infinity. The solution of the problem is given using Muskhelishvili's complex variable method with sectionally holomorphic functions. First, the solution to the (auxiliary) problem of a dislocation (or force) applied at a point in the matrix with the circular inclusion partially bonded is derived fully in its general form by solving the appropriate Rieman-Hilbert problem. It is subsequently used as the Green's function for the initial problem by introducing an unknown density function associated with a distribution of dislocations along the crack in the matrix. The initial problem is then reduced to a singular integral equation (SIE) over the crack in the matrix only. The SIE is solved numerically by appropriate quadratures and the stress intensity factors ...

This paper reviews experimental and analytical techniques that examine the efficiency of systems for the injection of powders in plasma jets used in spray coating. The types of injectors, the experimental techniques for observing particle trajectories and distributions, and the mathematical models used to investigate the momentum and heat-transfer phenomena between particles, carrier gas, and plasma jet are described. Experimental data are presented from numerous examples from the plasma spraying of ceramic powders.

In recent years, the mechanics of materials group at ETSECCPB-UPC has developed an approach for meso-mechanical analysis of concrete using zero-thickness interface elements in 2D and more recently in 3D. In this methodology, the meso-structure is generated with in-house developed computer programs based on Voronoï/Delaunay theory. In the analysis, continuum elements are assumed linear elastic. Non-linearity and fracture phenomena are made possible by the systematic use of zero-thickness interface elements inserted on a priori determined potential fracture planes. In this paper, the results obtained for a 3D specimen under biaxial loading are presented. The results turn out to be very satisfactory and, in particular, it is observed that even the specimens which contain a reduced number of aggregates (14 in the present calculations) lead to a realistic failure envelope under biaxial loading, and they also capture the tendencies of cracking and fracture orientations observed in experiments for different rates of biaxial loading. The special limit case of biaxial loading under restrained out-of-plane deformations is also analysed, leading to practically elastic behaviour as shown by available experimental evidence.

A detailed analytical and experimental investigation is presented to understand the dynamic fracture behavior of functionally graded materials (FGMs) under mode I and mixed mode loading conditions. Crack-tip stress, strain and displacement fields for a mixed mode crack propagating at an angle from the direction of property gradation were obtained through an asymptotic analysis coupled with a displacement potential approach. This was followed by a comprehensive series of experiments to gain further insight into the behavior of propagating cracks in FGMs. Dynamic photoelasticity coupled with high-speed photography was used to obtain crack tip velocities and dynamic stress fields around the propagating cracks. Birefringent coatings were used to conduct the photoelastic study due to the opaqueness of the FGMs. Dynamic fracture experiments were performed using different specimen geometries to develop a dynamic constitutive fracture relationship between the mode I dynamic stress intensity factor (K ID ) and crack-tip velocity ( ${\mathop a\limits^ \cdot }$ ) for FGMs with the crack moving in the direction of increasing fracture toughness. A similar ${\mathop a\limits^ \cdot }$ -K ID relation was also obtained for matrix material (polyester) for comparison purposes. The results obtained show that crack propagation velocities in FGMs were about 80% higher than the polyester matrix. Crack arrest toughness was found to be about 10% lower than the value of local fracture toughness in FGMs.

Nano-textured surfaces (NTSs) can reduce adhesion and friction and thus have potential to increase the reliability of micro-electro-mechanical systems and nano-electro-mechanical systems. However, deformation of the nanotextures severely limits the effectiveness of using NTSs. This article presents a novel concept of nano-surface-engineering by texturing the surface with core–shell nanostructures to produce deformation-resistant nanotextures. The NTSs were produced by thermal evaporation of Al on Si substrates to form Al nanostructures and then depositing amorphous silicon on top of Al by plasma-enhanced chemical vapor deposition. Friction and deformation of the NTSs were studied using a TriboIndenter and a scanning electron microscope. The results show that the novel NTS significantly reduced the coefficients of friction of the surface without any detectable plastic deformations of the nanotextures even after heavy scratches.

Received: 27 February 2009 / Accepted: 31July 2009 / Published (online): 01 November 2009 ... Association between neuromuscular tests and kumite performance on the Brazilian Karate National Team ... Hamilton Roschel ✉1, Mauro Batista 1, Rodrigo Monteiro 1, Romulo C. ...

Power is transmitted from motor to output shaft without any interference when no excessive load acting on the machine. But major problem is faced by industry on the machine that is when excessive load will act on the output shaft then problem of overloading make the driving motor or engine to stall; which will lead to burnout of the electric motor. In extreme cases this overload will lead to the breakage of drive elements or the clutch itself. In order to avoid the damage of the transmission elements it is necessary that the input and output shafts be disconnected in case of sudden overloads. The isolation of the input driver member i.e.; motor from the output member is absolutely necessary to avoid damage itself. Such serious problem which face by the industry can be avoided by use of Torque limiter timer belt spindle drive for overload protection and this can be achieved by the overload slipping ball clutch which is an safety device used in the transmission line to connect the driving and driven elements such that in case of occasional overload the clutch will slip there by disconnecting the input and output members. This protects the transmission elements from any breakage or damage and to cope up with this situation static structural analysis is done on the different parts of Torque limiter such as Base flange, Test rig, output shaft, plunger etc. In this case according to the discussion with company person we will decide to done the static analysis of various parts such as base flange, test rig, output shaft etc.

The analysis of the mineralogical composition of most rock wastes shows the presence of a high percentage of minerals with SiO2 and Al2O3, which could be used as raw materials for ceramic products. The main objective of this work is to recover wastes from one primary rock industry, utilised in the production of tiles and flooring, for the manufacturing of ceramics, using powder technology: pressing and sintering. The sinterability of the powders, with and without previous heat treatment, was studied in order to obtain a product with the best performance. Powders from different quarries after being uniaxial pressed at 40 MPa, or isostatic pressed at 170 MPa and sintered within the range 1150–1170°C present properties as follows: (a) hardness: 5.5–7.5 GPa; (b) transverse rupture strength: 55–94 MPa; (c) abrasion and erosion wear better than that of bulk to be drawn materials, and (d) water absorption of less than 0.5%. The results allow the conclusion that these wastes can be recovered and used successfully in the manufacture of ceramics with better performance than traditional tiles and flooring.

Pulsed beams, originating from a high pressure, fast acting valve equipped with a shaped nozzle, can now be generated at high repetition rates and with moderate vacuum pumping speeds. The generated high intensity beams properties are discussed, together with their propagation in the vacuum system requirement of skimmed beams systems.