Experimental studies on optimization of process parameters and finite element analysis of temperature and stress distribution on joining of Al�CAl and Al�CAl2O3 using ultrasonic welding

This study is carried out to optimize the process parameters like weld time, weld pressure, and amplitude of vibration to maximize the weld strength in Al?CAl welding using Taguchi??s design of experiments methodology. Experiments are conducted using 0.3-mm thick pieces of aluminum, and the temperature generated at the weld interface and the weld strength for all the specimens are measured. Also, a finite element model is developed that is capable of predicting the interface temperature and stress distribution during welding. Further, a preliminary study on the joining of alumina to aluminum is also carried out, and the finite element models of temperature and stress distribution during welding are simulated. Results of experimental work and FEM studies are compared and found to be in good agreement.     

Effect of enzyme assisted extraction on quality and yield of volatile oil from black pepper and cardamom

The present study investigated the effect of enzyme pre-treatment on extraction of active compounds from spices, namely, black pepper and cardamom. A mixture of enzymes, namely, Lumicellulae (a mixture of cellulase, β-glucanase, pectinase, and xylanase), was used for the pre-treatment of black pepper and cardamom. The pre-treatment of spices with enzyme increased the yield of essential oil. The GC and GC-MS evaluation of the essential oil showed that the major active components in spices, such as, β-caryophyllene in black pepper and α-terpenyl acetate in cardamom, markedly increased from 15.03 to 25.58 and 38.91 to 48.6%, respectively, on enzyme treatment as compared with the untreated control. The improvement in the yield and the major components of essential oil was attributed to the destruction of the cell wall structure by the enzymes pre-treatment which was substantiated with microscopical images using SEM.     

Candida tropicalis BPU1, a novel isolate from the rumen of the Malabari goat,is a dual producer of biosurfactant and polyhydroxybutyrate

This unique study reports a new strain (BPU1) of Candida tropicalis isolated from the rumen of the Malabari goat, showing dual production of biosurfactant and polyhydroxybutyrate. C. tropicalis strain BPU1, a facultative anaerobe, was tuned to become an aerobe in specially designed flask, the Benjamin flask. The puffy circular colonies were smooth, white‐to‐cream in colour, with pseudo‐filaments. The strain fermented glucose, sucrose, maltose and dextrose, but not lactose and cellulose. It assimilated (NH₄)₂SO₄, peptone, glycine and arginine, but not NaNO₃, as the nitrogen source. Interestingly, it utilized groundnut oil (up to 0.3%) in a specially designed basal mineral salt medium (BSM). Its capability for dual production of a biosurfactant and a polyhydroxybutyarate (PHB) was explored by various methods from the BSM–oil medium. Extracted biosurfactant from 6 day‐old culture was biochemically characterized as a complex of lipid and carbohydrate with an R_f value of 0.88 by thin layer chromatography. Its PHB production was confirmed by specific staining methods with Nile blue sulphate, Sudan black B and Sudan 3. Briefly, this first‐ever report gives ample physical evidence for the dual production of a glycolipid (biosurfactant) and PHB by C. tropicalis strain BPU1 on a specially designed medium, which would open up elaborate research on this yeast. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermal expansion characteristics of cast Cu based metal matrix composites

Like any other metal/alloy, copper and its alloys also soften at elevated temperatures. Reinforcing with ceramic or carbon fibres is one of the suggested solutions to overcome this. Very limited literature is available on Cu based metal matrix composites (MMCs); none of these pertain to liquid phase fabrication. Hence, a systematic investigation was carried out on MMCs based on copper, with alumino-silicate fibres and carbon fibres as reinforcements. The MMCs thus produced exhibit a uniform distribution of reinforcement in the matrix. Coefficient of thermal expansion (CTE) values are lower than that of pure copper.     

Parametric optimization of ultrasonic metal welding using response surface methodology and genetic algorithm

This paper focuses on the development of an effective methodology to determine the optimum welding conditions that maximize the strength of joints produced by ultrasonic welding using response surface methodology (RSM) coupled with genetic algorithm (GA). RSM is utilized to create an efficient analytical model for welding strength in terms of welding parameters namely pressure, weld time, and amplitude. Experiments were conducted as per central composite design of experiments for spot and seam welding of 0.3- and 0.4-mm-thick Al specimens. An effective second-order response surface model is developed utilizing experimental measurements. Response surface model is further interfaced with GA to optimize the welding conditions for desired weld strength. Optimum welding conditions produced from GA are verified with experimental results and are found to be in good agreement.