NISCAIR Online Periodicals Repository Collection: IJEMS Vol.12(4) [August 2005]

Effect of contact geometry on fretting fatigue life of aluminium alloy 2024-T3

Fri, 29 Jul 2005 22:58:59 GMT

Title: Effect of contact geometry on fretting fatigue life of aluminium alloy 2024-T3

Authors: Farrahi, G H; Majzoobi, G H; Chinekesh, H

Abstract: The effect of contact geometry on fretting fatigue life was investigated by experiments and numerical simulation. The experiments were conducted for flat and cylindrical pads under the same contact normal force. The post-test examinations including crack growth measurements and fractography were carried out using optical and scanning electron microscopy (SEM). Numerical simulations of pad-specimen assembly with and without crack were performed using a finite element (FE) analysis. The experimental study revealed that the rate of crack growth was higher at the early stages of fretting fatigue for cylindrical pads. This stage corresponds to a higher K_II for cylindrical contact model. After this stage, the effects of friction force and K_II decrease and the effects of tensile stress and K_I become more significant. The experimental results also showed that fatigue life of AA2024 reduced by nearly 75% under fretting fatigue condition. However, the reduction for cylindrical contact geometry was more than that measured for flat contact model. The numerical results indicated that the maximum shear, tensile, and Von-Mises stresses which are thought to be the origin for initiation and growth of crack, occur at the trailing edge of the contact surface for flat and cylindrical pads. SEM examination confirmed that the crack initiated from the points of stress maxima.

Page(s): 331-336

Blue-green emission from organic light emitting diodes based on aluminum complex

Fri, 29 Jul 2005 22:58:59 GMT

Title: Blue-green emission from organic light emitting diodes based on aluminum complex

Authors: Misra, Aparna; Kumar, Pankaj; Kumar, Lokendra; Ganesh, Nikhil; Gupta, Mohit; Dhawan, S K; Kamalasanan, M N; Chandra, Subhas

Abstract: Bluish-green emission from double layer organic light emitting diode (OLED), based on an aluminium complex, bis-(2-methyl 8-hydroxyquinoline) aluminium hydroxide (Almq₂OH), as an emissive material and N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)benzidine (TPD), as hole transport material with an electro-luminescence maximum at 506 nm, has been reported. The good thermal stability, good performance for the OLED applications, and a noticeable blue shift in the electroluminescence, in comparison to Alq₃, make this Al complex a good contender for OLED applications for light emission in the blue-green region. It was also found that the devices based on this material have a slightly higher turn-on voltage than similar Alq₃ devices. This can be attributed to the higher energy-gap of the material. The photoluminescence and electroluminescence spectra are reported and a shift of 9 nm in peaks is observed. The current-voltage characteristics of the device have also been studied.

Page(s): 321-324

Design and implementation of PLC cum micro-controller based electrically synchronized lift

Fri, 29 Jul 2005 22:58:59 GMT

Title: Design and implementation of PLC cum micro-controller based electrically synchronized lift

Authors: Sivanandam, S N; Sumathi, S; Deepa, S N

Abstract: Automobile industry is developing most extravagantly. The maintenance of the automobiles plays an important role, which is achieved by latest service station equipments. Electro-mechanical two-post lift is used to lift the vehicle to top or bottom and performs the required service operations under chassis. As in the present design and fabrication of the two-post lift, sprockets and chain mechanism are present for the transmission of the drive, but this results in slight non-linearity in the arm arrangements. This non-linearity in worst case may result in destruction of the automobile placed on the lift. The main aim of this paper is to avoid this non-linearity hence synchronization control of the arm movements is proposed for automating the lift, by removing the sprocket and chain mechanisms. The synchronization is implemented using two types of controllers, which includes micro-controller and the programmable logic controller. An inductive proximity sensor is selected to sense the rotation of the motors and produce pulses, which is used to control the movement of arm arrangements. The micro-controller programming is implemented using the software AVR Studio 3.5. The programmable logic controller programming is performed using the software STEP-7 Micro/Win 32.

Page(s): 269-277

Effect of carboxylic acids on the morphology, physical characteristics and hydration of -hemihydrate plaster

Fri, 29 Jul 2005 22:58:59 GMT

Title: Effect of carboxylic acids on the morphology, physical characteristics and hydration of -hemihydrate plaster

Authors: Singh, N B; Vellmer, C; Middendorf, B

Abstract: Hydration of -hemihydrate in the presence of different concentrations of tartaric, succinic, malic and citric acids was studied. All the acids, except tartaric acid, retard the hydrations. pH measurements have shown that during hydration acids are adsorbed at solid surfaces, leading to the retardation of hydration. E-modulus of elasticity, tensile strengths, total porosity, compressive strength, morphological and temperature changes during hydration were studied. It is found that morphological changes control the strength properties.

Page(s): 337-344