Study of formability of tailor-welded blanks in plane-strain stretch forming

In sheet metal forming, failure in the regions of the blank which are subjected to plane-strain deformation is one of the most common modes of failure. Therefore, study of forming limits of tailor-welded blanks (TWBs) deformed under plane-strain stretching is important to avoid failure in stampings of these prewelded composite blanks. In the present work, formability of three different types of tailor-welded blanks (TWBs) has been studied by limiting dome height (LDH) tests in plane-strain deformation mode. In all the three TWB combinations, the effect of weld orientation, with respect to major principal strain on formability, has been studied. It has been found that in TWBs with difference in thickness and properties, the LDH is higher in transverse (weld line parallel to width) cases when compared to longitudinal (weld line parallel to length) cases. The weld properties play a major role in the deformation of longitudinal specimens. But the extent of difference in properties, thickness, and surface characteristics has a strong influence on the location of fracture in transverse specimens. Weld line movement occurs toward thicker/stronger side during stretch forming of TWBs. The maximum weld line movement occurs at the pole, and it is highest in TWBs with difference in thickness. The extent of weld line movement is higher in the transverse samples than in the longitudinal samples.     

Mechanical,Thermal, and Interfacial Characterization of Randomly Oriented Short Sisal Fibers Reinforced Epoxy Composite Modified with Epoxidized Soybean Oil

Short sisal fibers were reinforced in epoxidized soybean oil (ESO) modified toughened epoxy blends to improve the mechanical and thermo mechanical properties. Tensile modulus and tensile strength of the composite with 15 wt% sisal fiber were found to be increased as compared with bio-based epoxy blend. From DTG analysis, rate of degradation peak is found to be shifted to higher temperature revealing enhanced thermal stability of composite over base matrix. Dynamic mechanical analysis predicted higher storage modulus and higher glass transition temperature of bio-based epoxy composite. Scanning electron micrographs showed strong fiber-matrix adhesion. Contact angle measurement reveals the hydrophilic character of bio-based epoxy composite     

Electrical impedance spectroscopic study of mandarin orange during ripening

Electrical impedance spectroscopy (EIS) as non-destructive investigation has been conducted to study the electrical impedance variations during ripening of mandarin orange. The objective of the work is to study the electrical impedance variations and variations in weight of the orange fruit with different ripening state. Electrical equivalent circuit has been modeled relative to the Nyquist plot obtained during the ripening of orange by non-linear curve fitting technique. EIS studies on orange fruit have been conducted by applying a small amount of alternating current through an array of Ag/AgCl electrodes attached to the orange fruit. The impedance and phase angles of orange fruit are measured at frequency sweep from 50 Hz to 1 MHz for 100 frequency points. The results revealed that the impedance, real part and imaginary part of the impedance all are increased and the weight of orange are decreased with the increase in ripening state. It is observed that the electrical equivalent circuit of orange fruit contains a constant phase element.     

Improved scatterer property estimates from ultrasound backscatter using gate-edge correction and a pseudo-Welch technique

Quantitative ultrasound (QUS) techniques have been widely used to estimate the size, shape and mechanical properties of tissue microstructure for specified regions of interest (ROIs). For conventional methods, an ROI size of 4 to 5 beamwidths laterally and 15 to 20 spatial pulse lengths axially has been suggested to estimate accuracy and precision better than 10% and 5%, respectively. A new method is developed to decrease the standard deviation of the quantitative ultrasound parameter estimate in terms of effective scatterer diameter (ESD) for small ROIs. The new method yielded estimates of the ESD within 10% of actual values at an ROI size of five spatial pulse lengths axially by two beamwidths laterally, and the estimates from all the ROIs had a standard deviation of 15% of the mean value. Such accuracy and precision cannot be achieved using conventional techniques with similar ROI sizes.     

Experimental and numerical studies on the forming behavior of tailor welded steel sheets in biaxial stretch forming

Stretch forming is an important process in making complex stampings for autobody components. In the present work formability of three different types of tailor welded blanks (TWBs) in biaxial stretch forming modes has been studied by conducting limiting dome height (LDH) tests. The TWBs are laser-welded samples of low carbon and ultra low carbon steel sheets with difference in thickness, grade and surface conditions. In TWBs with difference in thickness, the LDH decreases as the thickness ratio increases and the thickness of the thinner side is also crucial. A high thickness ratio causes two major strain peaks on thinner side and fracture takes place due to strain localization at the peak close to the pole. The weld ductility and the extent of difference in properties are the two crucial parameters for formability in TWBs with difference in properties. In both these TWBs, the fracture takes place perpendicular to the weld line and propagates towards the stronger side. Significant weld line movement occurs towards the thicker/stronger side in biaxial stretch forming. The maximum weld line movement occurs at the pole and it increases with increase in thickness ratio and becomes constant beyond a certain thickness ratio. The peak load required to deform the TWB specimens is less compared to the corresponding parent sheets. In case of TWBs with difference in thickness, as the thickness ratio increases, the peak load reduces due to decreasing punch-blank contact area.     

Fabrication of SnS2 flower like nanoflake assemblies through thermal evaporation

Uniform as well as flower like patterns of SnS2 nanoflakes were produced by a thermal evaporation process. Interpenetrating phenomenon was observed between the individual nanoflakes during the course of their lateral growth. The interpenetrating growth and controlled vapor concentration as well as the substrate temperature leads to the formation of flower like assemblies of SnS2 nanoflakes. Morphology and growth mechanism of the nanostructures were studied by scanning electron microscopic observations at different stages of the nanoflake growth. The produced nanoflakes were characterized by X-ray diffraction, scanning and transmission electron microscopy, and Raman spectroscopic measurements. SnS2 nanoflakes were perfectly single crystalline and growth direction of the nanoflakes was along the [101]-lattice plane.     

Antiamoebic activity of Piper longum fruits against Entamoeba histolytica in vitro and in vivo

Proposed changes in postgraduate surgical training must be seen in the context of changes being implemented in medical schools. The reorganization of discipline-based departments into large units of biomedical science; the reduction in time allotted to anatomy, particularly to dissection by students; the development of integrated courses with multidisciplinary examinations in which poor performance in anatomy can be compensated by good marks in other subjects; the decline in staff numbers (faculty) with expertise in human anatomy and corresponding enthusiasm for teaching it; and the loss of demonstratorships available to surgical trainees are all factors that leave today's medical graduates who embark upon surgical training programs poorly equipped in their knowledge of anatomy. This deficiency is not easily remedied by the proposed changes in Basic Surgical Training and is not adequately identified by the examination arrangements. It is argued that a structured oral examination with a wide spectrum of components, including dissections, living and surface anatomy, osteology, radiographs and scans, and microanatomy, would be the best way of assessing the familiarity of candidates with anatomy and their suitability to proceed to Higher Surgical Training.     

Secured and Imperceptible Data Transmission Through Digital Audio Signal with Reduced Internal Noise

Wireless Personal Communications - The work proposed in this paper aims at two major concerns of wireless transmission, which are security and imperceptibility of the transmitting data. This method...