Statistical analysis of high cycle fatigue investigations of cast magnesium alloys under transverse load

Magnesium is the lightest structural material used and it is important to explore its properties completely as it is used in aviation, automotive, communication etc., This paper reports the reliability analysis carried out on the high cycle fatigue investigations performed on cast AZ91 Magnesium alloys under transverse load. An Electro dynamic shaker system was used to apply transverse load on the specimens fabricated as per ASTM standard. Weibull analysis was under taken to check and compare the reliability of the investigations on gravity cast and low pressure cast AZ91 magnesium alloys.     

Analysis of Metallurgical and Mechanical Properties of Continuous and Pulsed Current Gas Tungsten Arc Welded Alloy C-276 with Duplex Stainless Steel

The present work investigates the microstructure and mechanical properties of alloy C-276 fabricated by continuous and pulsed current gas tungsten arc welding process and by employing ER2553 filler wire. Optical and scanning electron microscopic analyses were carried out to study the microstructures of weldments produced. Energy dispersive X-ray spectroscopy (EDS) was performed to investigate the formation of secondary phases in the weldments. The results disclosed that pulsed current gas tungsten arc welding showed refined microstructure compared to continuous current gas tungsten arc welding. SEM/EDS analysis revealed the segregation of Mo in the weld interface regions in both the welding techniques. The extent of microsegregation reduced the strength and toughness of the weld joint compared to the base metal. Bend test revealed cracks in the weld interface region in both the weldments.     

Monitoring of hard turning using acoustic emission signal

Monitoring of tool wear during hard turning is essential. Many investigators have analyzed the acoustic emission (AE) signals generated during machining to understand the metal cutting process and for monitoring tool wear and failure. In the current study on hard turning, the skew and kurtosis parameters of the root mean square values of AE signal (AERMS) are used to monitor tool wear. The rubbing between the tool and the workpiece increases as the tool wear crosses a threshold, thereby shifting the mass of AERMS distribution to right, leading to a negative skew. The increased rubbing also led to a high kurtosis value in the AERMS distribution curve.     

Pyrolysis kinetics of Athabasca bitumen using a TGA under the influence of reservoir sand

Pyrolysis kinetics of thermal decomposition of bitumen was investigated by thermogravimetric analysis (TGA). TGA experiments were conducted at multiple heating rates of 5, 10, 20°C min^–1 up to 800°C to obtain the pyrolysis characteristics of bitumen. Weight loss curve from TGA shows that two different stages occurred during bitumen pyrolysis. Differential method has been used for determining the kinetic parameters and the best fit for the order of reaction was found based on the R² values. Kinetics results confirm the presence of two different stages in bitumen pyrolysis with varying kinetic parameters. The average activation energy for the first and second stage was 29 and 60 kJ mol^?1 and the average order of the reaction was 1.5 and 0.25, respectively. Experiments have been conducted with different reservoir sand. The effect of different source of sand reveals no effect on the pyrolysis behaviour of bitumen. A considerable difference was found with the pyrolysis of bitumen–sand mixtures and bitumen alone based on coke yield and activation energy. © 2011 Canadian Society for Chemical Engineering     

Antimicrobial and anticoagulation activity of silver nanoparticles synthesized from the culture supernatant of Pseudomonas aeruginosa

Here, we describe biosynthesis of silver nanoparticles by reduction of aqueous Ag⁺ ions with the culture supernatant of Pseudomonas aeruginosa. The morphological, physiological, biochemical and molecular level identification of the strain GS1 resembles P. aeruginosa. The nanoparticles synthesized by P. aeruginosa were characterized by UV–vis spectroscopy, dynamic light scattering (DLS) and scanning electron microscopy (SEM). The size-distribution of nanoparticles was determined using a particle-size analyzer and the average particle-size was found to be 80 nm. The biological activities of the synthesized silver nanoparticles like antimicrobial activity were confirmed against Escherichia coli and Staphylococcus aureus and it have stable anti-coagulant effect.     

Optimization of plasma treatment variables to improve the hydrophilicity of polylinen® fabrics

Polylinen^® fabrics are obtained as a result of modification in the physical structure of polyester yarns to replicate the linen fabric. The scanning electron microscope analysis and Fourier transform infrared results reveal that the plasma treated fabric surface is effectively modified to enhance the wettability of the fabrics. In the present study, response surface methodology was employed to investigate the effects of different plasma treatment variables on the wetting behavior of polylinen fabrics. Box–Behnken design was used for the optimization of plasma treatment process and to evaluate the effects and interactions of the process variables, i.e. treatment time, power, and distance between the electrodes on the wettability of polylinen fabrics. The optimum conditions for maximum wicking height (4.3?cm) and spreading rate (86?s) of polylinen fabrics were established at 75?s treatment time, 460 watt power, and 2.5?cm distance between the electrodes. The plasma treated polylinen fabrics showed much better wettability in terms of wicking and spreading rate compared to untreated fabrics, which confirms that the modified structure of polylinen fabric and the plasma treatment influences the wettability of fabrics.     

Influence of transverse load on the high cycle fatigue behaviour of low pressure cast AZ91 magnesium alloy

A new testing procedure, employing transverse load was adopted to investigate the high cycle fatigue behaviour of low pressure cast AZ91 magnesium alloy. The tests were conducted with an electro dynamic shaker system by employing specimens fabricated as per ASTM standard. S–N plot was generated from the test results and compared with that of gravity cast AZ91 alloy tested in identical ambience. The influence of transverse load on the fatigue behaviour of these alloys is discussed. As fatigue cracks were found to have initiated in pores in most of the tested samples, pores were assumed as initial cracks as per linear fracture mechanics and the critical stress intensity amplitude (K_cr) was estimated. Structure–fatigue property correlations are discussed using fractographs. Mean stress effect on the fatigue properties and effects of alloying constituents are also discussed.     

Numerical and experimental investigation on the thermochemical gasification potential of Cocoa pod husk (Theobroma Cacoa) in an open-core gasifier

Clean Technologies and Environmental Policy - Thermochemical conversion is a promising technology to generate producer gas (PG) from different types of agroforestry biomass residues. To use an...     

3D printing-assisted combinatorial approach for designing mechanically-tunable and vascular supportive nanofibrous membranes to repair perforated eardrum

Perforation of eardrum or tympanic membrane (TM) is a common clinical condition, which occurs due to infection or injury of the eardrum, and could results in varying degrees of conductive hearing loss among all ages. In this study, the authors report the combinatorial approach of designing mechanically-tunable and vascular supportive nanofibrous membranes by 3D printing-assisted electrospinning (e-spin) using polycaprolactone (PCL) and gelatin with different mass ratios suitable to repair a perforated eardrum. The physicochemical, mechanical, and biological properties of the membranes were characterized. The results show that the membrane has nanofibrous morphology with fibers are of varying size (400–600 nm in diameter) depending on processing conditions. The wettability and mechanical properties of the membrane can be tuned by regulating the gelatin content. Moreover, a biomimetic repair strategy inspired by chicken eggshell membrane, often used in wound dressings, was also presented for study and results show that the suture retention strength of the fabricated membrane can meet clinical translational requirements to promote TM healing. The vascular cell responsiveness of PCL/gelatin nanofibrous membrane was evaluated using human umbilical vein endothelial cells (HUVECs) and the results showed satisfactory biocompatibility, vascular cell responsiveness, and cell proliferation. The findings of this study demonstrate that the combinatorically engineered PCL/gelatin nanofibrous membrane has great potential for repairing perforated eardrum.