Effect of mechanical and fractographic properties on hole expandability of various automobile steels during hole expansion test

Hole expandability is a vital formability parameter for automobile body parts that are subjected to deep drawing conditions. In this paper, the influence of mechanical and fractographic properties on hole expansion ratio has been studied and reported. The hole expansion test has been carried out for seven different automotive steel sheets of varying thicknesses. Hole expansion ratio expressed in terms of hole expansion percentage is strongly influenced by the microstructure of the sheet metal. Hole expansion test experiments were performed on flat circular plates with a hole in the center to investigate the fracture behaviors of various automobile steels such as microalloyed, C–Mn, high-strength I.F. (SPRC-35) of three grades, extra galvannealed I.F., and HSLA (E-36) steel sheets. In the hole expansion test, deformation by lip is caused when the punch expands the hole. Fracture by petalling occurs when the holes in the sheets are completely pierced by the punch. Large circumferential strains are accommodated in the deforming sheet material. The mechanical properties, namely, strain hardening exponent (n), normal anisotropy ( $ \overline{r} $ ), formability parameter (n $ \overline{r} $ ), and other properties, namely, Mohr's circle shear strains (γ ₃₁ and γ ₁₂), strain triaxiality factor (T), and stress triaxiality factor (T _o), affected the hole expansion ratio of different steels tested. Similarly, the fractographic factors, such as void size in micrometers, void area fraction, and d-factor, affect the hole expansion ratio. Among the steel sheets tested, extra galvannealed I.F. steel possesses the highest hole expansion ratio.     

Effect of friction factor on barrelling in elliptical shaped billets during cold upset forging

This work deals with the effect of friction factor of different lubricants on barrelling in elliptical shaped billets during cold upset forging. Experiments were carried out to generate data on cold upset forging of commercially pure aluminium solid of elliptical billets with different lubricants applied on both sides in order to evaluate the effects of friction factor on the forming behavior of barrelling phenomenon under plane stress state condition. The radius of curvature of both major and minor bulge measured conformed to the calculated one using experimental data and the calculations were made with the assumption that the curvature of the bulge followed the form of a circular arc. Three different b/a ratios (ratio of minor to major diameter) namely, 0.6, 0.7 and 0.8 and aspect ratio (ratio of height to diameter) of 0.75 were prepared and cold upset forged. The relationship was also established between the various bulge parameters like the hoop strain, the axial strain, the new geometric shape factor, the stress ratio parameters, the major and minor radius of curvature of the bulge and the friction factor ‘m’ of different lubricants.     

Dry sliding wear behaviour of AA 6351-ZrB2 in situ composite at room temperature

In the present work, AA 6351-xZrB₂ [x = 0, 3, 6 and 9 weight percentage (wt.%)] in situ composites have been prepared by the reaction of mixture of K₂ZrF₆ and KBF₄ with molten aluminium alloy at a reaction temperature of 850 °C. The in situ prepared composites were characterized by using scanning electron microscope (SEM), X-ray diffractometer (XRD), and microhardness analysis. The sliding wear properties of the prepared composite at room temperature were estimated by a pin-on-disc wear testing equipment using the composite material; the pins were machined according to standard sizes, and the tests were conducted as per the standards recommended by the ASTM G99-95a designation of different weighing percentage at room temperature. The wear characteristics of the composite in the as-cast, the solutionized and the solutionized-aged conditions were studied by conducting sliding wear test at the load of 9.81 N. The results indicated that the wear rate was decreased with an increase in the weight percentage of ZrB₂ and the wear resistance was increased with an increase in the fraction of ZrB₂ particulates in composite before and after heat treatment.     

Comparison of the transdermal absorption of nimesulide from three commercially available gel formulations

Nimesulide is a non-steroidal anti-inflammatory drug (NSAID) applied topically for a variety of conditions characterized by pain and inflammation. One of the aims of this study was to compare the permeation profile of nimesulide from the commercially available transdermal gel formulations across dermatomed porcine and human skin. The in vitro transdermal absorption of nimesulide formulations across porcine skin and human skin was studiedfor 24 hr using a continuous flow-through diffusion cell. The three commercial gels used in this study were Nimulid, Nise Gel, and Orthobid. All gels contained 1% (w/w) nimesulide. An infinite dose of nimesulide gel (about 300mg) was applied on the skin over 0.636 cm2 surface area. The rank order for the drug permeation from these formulations using porcine skin was: Nimulid > Orthobid > Nise Gel. The rank order of the permeation across human skin was: Nimulid> Nise Gel> Orthobid. The permeation profiles followed zero-order kinetics without any significant lag time. The steady-state flux of nimesulide from Nimulid was significantly higher than that of Nise Gel and Orthobid in both porcine and human skin (p <.05). However, there were no significant differences in the delivery of nimesulide (24 hr) from Nise Gel and Orthobid across both human and porcine skins. The results suggest that the Nimulid gel may have a greater bioavailability of nimesulide compared to the other gels. In addition, permeation profiles of the various gels across porcine skin did show a positive profile behavior to human skin. However, the in vitro drug release of nimesulide gels across a synthetic membrane did not correlate with skin permeation profiles.     

Factors influencing the kinetics of electrochemical reactions in milling

Input of mechanical energy at a high rate can drive a system and induce phase transformations and chemical reactions away from equilibrium. The evolution of such a change depends on both thermodynamic as well as kinetic factors. Besides the microstructural changes like attainment of nanostructure, which alters the overall free energy, the high rate of mechanical energy input also changes the kinetics by influencing the mass transport and related processes. In order to understand these factors, we have recently started a programme of looking at the influence of mechanical energy on driving simple chemical reactions in solid state. In this presentation we shall present and discuss the results of two kinds of situation that we have studied. The first one is simple electrochemical replacement reactions between metals and metal sulphates in solid state. We show that the mechanical milling alters the kinetics of these reactions, which can be rationalized by considering the phenomena taking place at the microscopic level. For example we will show that the crystal structure of the sulphate and the nature of the reaction product at the interface influence the mechanochemistry significantly. It is even possible in some special cases to alter the direction of the chemical reaction. In the second set of results we shall present the effect of mechanical milling on the site occupancy in ferrites, which can lead to a significant change in magnetic behaviour.     

Asymptotic Magnitude Bode Plots of Fractional-Order Transfer Functions

Development of asymptotic magnitude Bode plots for integer-order transfer functions is a well-established topic in the control theory. However, construction of such plots for the fractional-order transfer functions has not received much attention in the existing literature. In the present paper, we investigate in this direction and derive the procedures for sketching asymptotic magnitude Bode plots for some of the popular fractional-order controllers such as $PI^\alpha$, $[PI]^\alpha$, $PD^\beta$, $[PD]^\beta$, and $PI^\alpha D^\beta$. In addition, we deduce these plots for general fractional commensurate-order transfer functions as well. As applications of this work, we illustrate 1) the analysis of the designed fractional-control loop and 2) the identification of fractional-order transfer function from a given plot.      

Enhancing the oxidation stability of Mahua oil methyl ester with the addition of natural antioxidants

A rapid decrease in the availability of non-renewable fossil fuels has initiated the search for alternative fuels. Biodiesel obtained from various feedstocks has proved to be an effective alternative source for diesel engines due to its convincing fuel characteristics. The oxidation property of biodiesel is influenced by external factors such as sunlight and exposure to atmosphere.The oxidation stability of biodiesel can be improved by the addition of antioxidants which may be synthetic or natural. Natural antioxidants are more effective than synthetic ones in terms of economic value as well as prevention of adverse carcinogenic effects. Natural antioxidants, namely, ginger, Moringa oleifera, oregano, basil, and clove were extracted and used for the present study. The antioxidant activity of the additives was analyzed by DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging activity. The DPPH scavenging effect was calculated in terms of % by using absorbance values recorded with UV spectrophotometer. Among the antioxidants used, clove additive was found to be more efficient in enhancing the oxidation stability, with scavenging effect of 42.23%, 47.67%, 51.62%, and 55.61% for 500, 1000, 1500, and 2000 ppm, respectively. It was also observed that the scavenging activity increased with the concentration of antioxidant additives, and the maximum value was recorded at a concentration of 2000 ppm. Mahua oil methyl ester (MOME) was selected as biodiesel for the present study for which the oxidation stability has to be evaluated. The oxidation stability of MOME was measured in terms of induction period using the Rancimat method which does not meet the required standards. The oxidation stability of MOME, MOME + ginger 2000, MOME + M. oleifera 2000, MOME + oregano 2000, MOME + basil 2000, and MOME + clove 2000 was evaluated. The highest induction period was observed to be 38.44 h for MOME + clove 2000 blend. Hence, clove additive was found to be more effective among the selected natural antioxidants in terms of increasing the scavenging effect as well as increasing the oxidation stability of MOME. Thus, the addition of natural antioxidants can be recommended to improve the oxidation stability of biodiesel based on their scavenging effect which can be further validated by means of the Rancimat method in terms of the induction period