Influence of Tool Tilt Angle on Material Flow and Defect Generation in Friction Stir Welding of AA2219

Heat treatable aluminium alloy AA2219 is widely used for aerospace applications, welded through gas tungsten and gas metal arc welding processes. Welds of AA2219 fabricated using a fusion welding process suffers from poor joint properties or welding defects due to melting and re-solidification. Friction stir welding (FSW) is a solid-state welding process and hence free from any solidification related defects. However, FSW also results in defects which are not related to solidification but due to improper process parameter selection. One of the important process parameters, i.e., tool tilt angle plays a critical role in material flow during FSW, controlling the size and location of the defects. Effect of tool tilt angle on material flow and defects in FSW is ambiguous. A study is therefore taken to understand the role of tool tilt angle on FSW defects. Variation in temperature, forces, and torque generated during FSW as a result of different tool tilt angles was found to be responsible for material flow in the weld, controlling the weld defects. An intermediate tool tilt angle (1o-2o) gives weld without microscopic defect in 7 mm thick AA2219 for a given set of other process parameters. At this tool tilt angle, x-force, and Z- force is balanced with viscosity and the material flow strain rate sufficient for the material to flow and fill internal voids or surface defects in the weld

Welding Studies on a Near-alpha Titanium Alloy

The mechanical properties and microstructures of electron beam and friction welds of a near-alpha titanium alloy IMI 834 (presently TIMET 834) have been evaluated. Electron beam welds that contain micro pores and friction welds are free from such solidification-related defects. Porosity index in electron beam welds shows a decreasing trend with an increase in the welding speed. Electron beam welds contain coarse prior β grains and fine transformed β microstructure while, friction welds contain fine prior β grains and coarse transformed β microstructure. Electron beam welds with fine transformed β microstructure exhibited higher strength as compared to friction welds with coarse transformed β microstructure. The impact toughness of both the welds is comparable. Drastic reduction in impact toughness was observed when the welds were subjected to post-weld ageing as a result of inter-lath precipitation. Coarse-grained electron beam welds exhibited better creep and stress rupture properties as compared to friction welds.Defence Science Journal, 2011, 61(6), pp.590-596, DOI:http://dx.doi.org/10.14429/dsj.61.64

Role of Threaded Tool Pin Profile and Rotational Speed on Generation of Defect Free Friction Stir AA 2014 Aluminium Alloy Welds

Influence of threads on tool pin and rotational speeds on defect occurrence in friction stir welding (FSW) of aluminum alloy AA 2014 T6 plates has been studied. The effect of FSW forces on the evolution of mechanistic defects, caused in turn through a variation in heat generation during the process has also been examined. In case of conical tool pin, relatively lower rotational speeds resulted in unbounded zones and micro defects while high speeds caused excessive flash, thereby resulting in surface defects and voids inside the weld. The FSW joints were defect-free at moderate speeds, hinting an optimum heat generation and flow. Reaction forces on the tool pin, in the welding direction, were correlated with the defect formation. Tools equipped with a threaded conical pin profile resulted in sound welds, irrespective of the tool rotational speeds in the entire range of 400 rpm - 2400 rpm. The threaded conical pin, with a relatively larger frictional area, may be contributing to higher levels of heat generation compared to a plain conical pin. Further, positive displacement of the hot plasticised material by the threads will carry away excess heat from the advancing-to-the-retracting side and simultaneously downwards, thus confining all heat within the weld zone.

IN VITRO ACCUMULATION OF CADMIUM CHLORIDE IN PAPAYA SEEDLING AND ITS IMPACT ON PLANT PROTEIN

Background: Carica papaya has wide range of applications in traditional medicine. It has high nutritional content and various medical applications. Objectives: In the present study, changes have been observed at the morphological, biochemical, antioxidation and protein level in Carica papaya L variety Pusa Dwarf by accumulation of cadmium chloride in vitro. Material and methods: Plants were treated with different concentrations (20ppm, 40ppm, 60ppm and 80ppm) of cadmium chloride, and examined changes in growth and protectively induced oxidative stress in relation to heavy metal in three weeks old seedlings. Protein profiling by SDS-PAGE was done to study the influence of severe heavy metal stress in Carica papaya L. variety Pusa Dwarf leaf and root explants. Result: Plant seedlings showed decrease in morphological characteristics like plant height, root and shoot length in response to increasing concentrations of heavy metal stress. Similarly carbohydrate content decreased in both leaves and roots while chlorophyll pigments (a+b) increased in leaf explants. Proline and polyphenolic compounds showed an increase in stressed plants compared to control. Conclusions: Plants undertake many adaptive mechanisms for their survival under metal stress which includes morphological as well as biochemical characters. Proline and polyphenolic compounds indicate the presence of excellent antioxidative ingredients to protect the induced by free radicals. Plant protein profiling supports the effect of heavy metal stress in papaya

Short-term safety and beneficial effects of hydroxyurea therapy in children with sickle cell disease

Introduction: Worldwide, sickle cell disease (SCD) is the most common hemoglobinopathy among which SS pattern is more common. Although hydroxyurea (HU) is approved by the Food and Drug Administration for the treatment of recurrent moderate-to-severe painful crises in pediatric sickle cell anemia, there is a fear of toxicities. Objectives: The objectives of the study were to evaluate the short-term safety and beneficial effects of low-dose HU therapy in SCD (SS pattern) children. Materials and Methods: This prospective cohort study enrolled 40 cases of severe SCD and started HU in a fixed dose of 10 mg/kg/day. During follow-up, cases were evaluated for compliance of HU, its toxic effects and adverse events from their histories, clinical examinations, and laboratory parameters. Furthermore, beneficial effects of HU therapy were evaluated by assessing blood transfusion rate, frequency of painful events, strokes, acute chest syndrome, avascular necrosis of femur, and estimation of hemoglobin F (HbF) level after 2 years of therapy. HU was discontinued temporarily if any toxicity or minor adverse drug events occurred during therapy and was restarted at the same dose after normalization of deranged laboratory parameters. Results: The clinical adverse drug events seen were nausea (8.33%), diarrhea (2.78%), and hematuria (2.78%). The most common hematological toxicity was anemia and thrombocytopenia. Renal and hepatic toxicities were transient in nature. The mean acute painful events and blood transfusion rate reduced significantly on HU therapy. It increased Hb and HbF level significantly in SCD children. Conclusion: HU is a safe drug without significant toxicity or adverse events in a dose of 10 mg/kg/day for short duration and it is beneficial in SCD (SS pattern) children in reducing acute painful events and decrease blood transfusion rate

Isolated congenital factor VII deficiency

Congenital factor VII (FVII) (proconvertin) is a rare autosomal recessive bleeding disorder. Bleeding manifestations and clinical findings vary widely, ranging from being asymptomatic to life-threatening bleeding. Intracranial bleeding is relatively less common with inherited FVII deficiency than with other coagulation disorders. We report a rare case of congenital FVII deficiency in an 11-year-old male child. The patient had recurrent subdural hemorrhages. The prothrombin time was markedly prolonged with a normal bleeding time, normal partial thromboplastin time and normal platelet count. Treatment consists of replacement therapy with fresh frozen plasma, prothrombin complex concentrates or plasma-derived FVII concentrates, and/or recombinant factor VIIa. Clinical heterogeneity is the hallmark of this disorder

Friction welding of AA6061 to AISI 4340 using silver interlayer

The present work pertains to the study on joining of AA6061 and AISI 4340 through continuous drive friction welding. The welds were evaluated by metallographic examination, X-ray diffraction, electron probe microanalysis, tensile test and microhardness. The study reveals that the presence of an intermetallic compound layer at the bonded interface exhibits poor tensile strength and elongation. Mg in AA6061 near to the interface is found to be favourable for the formation and growth of Fe2Al5 intermetallics. Introduction of silver as an interlayer through electroplating on AISI 4340 resulted in accumulation of Si at weld interface, replacing Mg at AA6061 side, thereby reducing the width of intermetallic compound layer and correspondingly increasing the tensile strength. Presence of silver at the interface results in partial replacement of Fe–Al based intermetallic compounds with Ag–Al based compounds. The presence of these intermetallics was confirmed by X-ray diffraction technique. Since Ag–Al phases are ductile in nature, tensile strength is not deteriorated and the silicon segregation at weld interface on AA6061 in the joints with silver interlayer acts as diffusion barrier for Fe and further avoids formation of Fe–Al based intermetallics. A maximum tensile strength of 240 MPa along with 4.9% elongation was obtained for the silver interlayer dissimilar metal welds. The observed trends in tensile properties and hardness were explained in relation to the microstructure

<span style="font-size:11.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-GB">Virtual screening and docking exploration on estrogen receptor: An <i>in silico</i> approach to decipher novel anticancer agents</span>

389-395Breast cancer is a prominent disorder that affects mostly mid aged women with a high intensity, upsetting every ninth women of ten. The available drugs and treatments fall back as they do not completely eradicate the cancerous cells from body. Hence, newer and more effective drugs and treatments against breast cancer are the need-of-hour. The increased level of estrogen within body increases the chance of breast cancer, whereas the regular concentration plays significant role in normal cell functioning. Melatonin is popularly used as an anti-estrogenic compound, whereas violacein an active secondary metabolite secreted by bacteria like ‘Chromobacterium violaceum’ has strong structural similarity with melatonin and, thus, possess latency of being tested for its anti-cancerous activity. In the current study, docking and virtual screening was utilized to prove the fact that violacein and similar compounds can bind more efficiently to estrogen receptor than that of melatonin and, hence, has potential to emerge as lead anti-estrogenic compound in treatment of breast cancer. </span