Simulation of friction welding of alumina and steel with aluminum interlayer

Friction welding is a complicated metallurgical process that is accompanied by frictional heat generation and plastic deformation. Since the thermal cycle of friction welding is very short, simulation becomes very significant. In the present work, a finite element-based numerical model has been developed to understand the thermo-mechanical phenomenon involved in the process of friction welding. The developed model is capable of predicting thermal distribution during friction welding of ceramics with metal using an aluminum interlayer for various time increments. Frictional heating at the interfacial region consumes the aluminum interlayer and establishes a bond between alumina and mild steel. Though there is mechanical mixing, the bond is incomplete in the aluminum-alumina interface. Due to the variation of thermal properties between alumina and mild steel, more amount of thermal stress is induced at the joint interface. Numerical simulation predicts the formation of residual stress in the alumina-mild steel side of the interface. This leads to incomplete interlocking that results in poor joint strength.     

The Durability of Adhesively-bonded Ti-6Al-4V

The durability of chromic acid-anodized Ti-6Al-4V alloy, adhesively-bonded with FM-5 supported polyimide adhesive has been studied. The performance tests compared titanium samples that had been thermally treated and bonded, and samples that were bonded and thermally treated. Following the thermal treatment, the durability was examined (1) by immersing wedge-type specimens in boiling water and measuring the crack growth and (2) by measuring the lap shear strength for single lap specimens. In the wedge tests, failure occurs within the adhesive for specimens treated at temperatures below 371°C for less than one hour. For treatments at higher temperatures and for longer periods of time, failure occurs within the anodic oxide. From the lap shear tests, the principal finding is that the lap strength decreases with increasing treatment time at constant temperature and with increasing temperature at a fixed time. For the lap specimens, failure occurs to a greater extent within the oxide as the treatment time and temperature increase. Surface analysis results indicate the formation of an aluminum fluoride species. It is reasoned that the formation of fluorine-containing materials weakens the oxide and promotes failure within the anodic oxide.     

Synthesis and characterization of polysaccharide based graft copolymer by using potassium peroxymonosulphate/ascorbic acid as an efficient redox initiator in inert atmosphere

Polysaccharide based graft copolymer (xanthan gum‐g‐4‐vinyl pyridine) was synthesized using potassium peroxymonosulphate/ascorbic acid redox initiator in inert atmosphere at 40°C. By studying the effect of the concentration of monomer, peroxymonosulphate (PMS), ascorbic acid (AA), xanthan gum (XOH), hydrogen ion along with effect of time and temperature on grafting characteristics: grafting ratio (%G), add on (%A), conversion (%C), efficiency (%E), homopolymer (%H), and rate of grafting (Rg), the reaction conditions for optimum grafting were determined. The optimum concentration of AA, H⁺ ion, 4‐VP for maximum grafting were found to be 10.0 × 10^?3 mol dm^?3, 2.5 × 10^?2 mol dm^?3, 10.0 × 10^?3 mol dm^?3, respectively. Maximum %G was obtained at minimum concentration of xanthan gum i.e., at 40.0 × 10^?2 g dm^?3 and at maximum concentration of PMS i.e., at 10.0 × 10^?3 mol dm^?3. The optimum temperature and time duration of reaction for maximum % of grafting were found to be 45°C and 120 min respectively. The synthesized graft copolymer was characterized by FTIR analysis. Thermogravimetric analysis showed that the xanthan gum‐g‐4‐vinyl pyridine is thermally more stable than pure gum. A probable mechanism was suggested for the graft copolymerization. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Hypoglycaemic and Hypolipidaemic Effects of Withania somnifera Root and Leaf Extracts on Alloxan-Induced Diabetic Rats

Withania somnifera is an important medicinal plant, which is used in traditional medicine to cure many diseases. Flavonoids were determined in the extracts of W. somnifera root (WSREt) and leaf (WSLEt). The amounts of total flavonoids found in WSREt and WSLEt were 530 and 520 mg/100 g dry weight (DW), respectively. Hypoglycaemic and hypolipidaemic effects of WSREt and WSLEt were also investigated in alloxan-induced diabetic rats. WSREt and WSLEt and the standard drug glibenclamide were orally administered daily to diabetic rats for eight weeks. After the treatment period, urine sugar, blood glucose, haemoglobin (Hb), glycosylated haemoglobin (HbA1C), liver glycogen, serum and tissues lipids, serum and tissues proteins, liver glucose-6-phosphatase (G6P) and serum enzymes like aspartate transaminase (AST), alanine transaminase (ALT), acid phosphatase (ACP) and alkaline phosphatase (ALP) levels were determined. The levels of urine sugar, blood glucose, HbA1C, G6P, AST, ALT, ACP, ALP, serum lipids except high density lipoprotein-bound cholesterol (HDL-c) and tissues like liver, kidney and heart lipids were significantly (p < 0.05) increased, however Hb, total protein, albumin, albumin:globulin (A:G) ratio, tissues protein and glycogen were significantly (p < 0.05) decreased in alloxan-induced diabetic rats. Treatment of the diabetic rats with WSREt, WSLEt and glibenclamide restored the changes of the above parameters to their normal level after eight weeks of treatment, indicating that WSREt and WSLEt possess hypoglycaemic and hypolipidaemic activities in alloxan-induced diabetes mellitus (DM) rats.     

Experimental and Morphological Investigations Into Electrical Discharge Surface Grinding (EDSG) of 6061Al/Al2O3p 10% Composite by Composite Tool Electrode

In this study, a special experimental setup of EDSG using EDM and surface grinding machine has been developed in the laboratory to investigate the effect of seven input parameters namely tool polarity, peak current, pulse on-time, pulse off-time, rotational speed, abrasive particle size, and abrasive particle concentration on material removal rate (MRR) as performance measure of the process. The novelty of the present research work is that successful efforts have been made to machine the 6061Al/Al₂O_3p 10% metal matrix composites (MMC) by composite tool itself. The copper-based composite tool electrodes were fabricated by powder metallurgy route with different sizes of abrasives of silicon carbide, while 6061Al/Al₂O_3p 10% MMC were fabricated through stir-casting process. The research outcome will identify the important parameters and their effect on MRR of 6061Al/Al₂O_3p 10% composite in EDSG. The experimental results reveal that tool polarity, peak current, and rotational speed are the most influential parameters that affect MRR in EDSG process. The micro-structural and morphological analysis of machined surfaces has also been carried out to analyze the surface topography. It has been concluded that the abrasive particles substantially improves the MRR after removing the resolidified layer from the machined surface.     

Machining Performance and Surface Integrity of AISI D2 Die Steel Machined Using Electrical Discharge Surface Grinding Process

The aim of this study is to establish optimum machining conditions for EDSG of AISI D2 die steel through an experimental investigation using Taguchi Methodology. To achieve combined grinding and electrical discharge machining, metal matrix composite electrodes (Cu-SiC_p) were processed through powder metallurgy route. A rotary spindle attachment was developed to perform the EDSG experimental runs on EDM machine. Relationships were developed between various input parameters such as peak current, speed, pulse-on time, pulse-off time, abrasive particle size, and abrasive particle concentration, and output characteristics such as material removal rate and surface roughness. The optimized parameters were further validated by conducting confirmation experiments.     

Influence of Pd Precursor and Method of Preparation on Hydrodechlorination Activity of Alumina Supported Palladium Catalysts

A series of alumina supported Pd catalysts were prepared by the novel deposition-precipitation method adopting the chloride precursor (DP-Cl) of Pd and varying the metal content from 0.25 to 1.0 wt%. The catalytic properties of prepared catalysts were studied by various characterization techniques such as N₂ adsorption, CO chemisorption, TPR, XRD, XPS, and TEM techniques. The activity and stability of the catalysts were evaluated for the gas phase hydrodechlorination (HDC) of chlorobenzene operating at atmospheric pressure. At 1 wt% of Pd the catalyst showed higher chlorobenzene conversion with good stability when tested for a period of 25 h, whereas the other catalysts exhibited a loss in activity with time. In order to elucidate the exceptional activity and stability of this catalyst, a few more catalysts with 1 wt% Pd were prepared by impregnation technique and also using a non-chloride precursor, palladium nitrate. The 1 wt% DP-Cl catalyst again was found to be the best among the others. The activity and stability of the DP-Cl catalyst was also found to be superior to two low-dispersed catalysts, each with 10 wt% Pd, prepared by conventional impregnation method using the chloride and nitrate as the precursors. The characterization results reveal that the high activity and stability of the DP-Cl catalyst is related to the formation of electron deficient Pd species and its stabilization in the octahedral vacancies of alumina.     

Nanoenergetic Composites of CuO Nanorods,Nanowires, and Al‐Nanoparticles

This paper reports on the synthesis of the nanoenergetic composites containing CuO nanorods and nanowires, and Al‐nanoparticles. Nanorods and nanowires were synthesized using poly(ethylene glycol) templating method and combined with Al‐nanoparticles using ultrasonic mixing and self‐assembly methods. Poly(4‐vinylpyridine) was used for the self‐assembly of Al‐nanoparticles around the nanorods. At the optimized values of equivalence ratio, sonication time, and Al‐particle size, the combustion wave speed of 1650 m s⁻¹ was obtained for the nanorods‐based energetics. For the composite of nanowires and Al‐nanoparticles the speed was increased to 1900 m s⁻¹. The maximum combustion wave speed of 2400 m s⁻¹ was achieved for the self‐assembled composite, which is the highest known so far among the nanoenergetic materials. It is possible that in the self‐assembled composites, the interfacial contact between the oxidizer and fuel is higher and resistance to overall diffusional process is lower, thus enhancing the performance.     

Investigation on the Phase Diagram of LiCl-KCl-NdCl<Subscript>3</Subscript> Pseudo-Ternary System

The ternary phase diagram of LiCl-KCl-NdCl₃ system has been investigated by differential thermal analysis (DTA), followed by characterization of the coexisting phases in the solid state by x-ray diffraction, in order to understand the interactions in the NdCl₃-LiCl-KCl ternary system. The results of these experiments showed that LiCl and K₂NdCl₅ form a non binary join section. This divides the LiCl-KCl-NdCl₃ system into two quasi-ternary sections, namely (1) LiCl-KCl-K₂NdCl₅ and (2) LiCl-K₂NdCl₅-NdCl₃ systems. Both are simple eutectic ternary phase diagrams. The ternary eutectic temperatures and eutectic compositions are determined to be 316?±?3 °C and 53.9 mol.% LiCl-38.7 mol.% KCl-7.4 mol.% K₂NdCl₅ in the LiCl-KCl-K₂NdCl₅ quasi-ternary section, while the other eutectic temperature and composition are determined to be 376?±?9 °C and 46.2 mol.% LiCl-32.5 mol.% K₂NdCl₅-21.3 mol.% NdCl₃ in the LiCl-K₂NdCl₅-NdCl₃ quasi-ternary section. A quasi-ternary peritectic reaction is observed at 37.7 mol.% LiCl-36.2 mol.% KCl-26.1 mol.% K₂NdCl₅ at 445?±?1°C. The primary and secondary crystallization temperatures for the samples are deduced from the heating runs of DTA traces, and the phases responsible for the various thermal events are ascertained. Isothermal sections at chosen temperatures and polythermal liquidus projection with isothermal contours are drawn over the ternary phase field.