Creep Tension Tests on Hastelloy Alloy X Bar, Predicting its Behavior and Applying the Data in a Design Problem

Creep is a continuing deformation at elevated temperatures under constant stress. Creep data are important in the design of many machine members subjected to high temperatures. Examples of these would be steam and gas turbine components, thermal cracking equipment in oil refineries, jet air-craft, missiles, rockets and mobile reactors. The second law of thermodynamics shows us that the efficiency of an ideal heat engine can be increased by increasing the temperature of the working fluid. The optimum strength-to-weight ratio is an essential requirement in aircraft structural design. But all these facts bring us the problem of higher creep rates for the same stresses. In some applications, the permissible creep deformations are critical, e.g. Allowance for creep is important in turbine blades for proper operation to maintain small clearances between the moving and stationary parts and in others no significance. The creep phenomenon has been known for the last 80 years, but knowledge of the phenomenon has advanced rapidly since World War II, due to more demand for high temperature materials, resulting in today’s successful new alloys. Creep deformation can be determined in the laboratory with a testing machine but conducting such tests for the entire life of the machine element is impracticable. As we know, the operating characteristics of an original model can be obtained from a small scale model by means of dimensional analysis. The idea was to have lead creep curves similar to those of the original material in order to obtain direct extrapolation from low temperature lead tests to operating conditions. Cases occur where parts are subjected to combine bending and direct load. For example, turbine blades are subjected to a b3ending action due to the transverse loading applied by the steam, and to a direct load due to centrifugal force. Under creep conditions, parts subjected to this combined straining action when the predominant action is bending are much more favorably stressed than would be the case if the material were elastic and when the predominant action is direct load the stress conditions will approach those for elastic condition. So analyzing the forces acting on a machine element is an important step in a design problem

Antihepatotoxic effect of Elephantopus scaber L. on carbon tetrachloride-induced hepatotoxicity in rats

Elephantopus scaber was used in folk medicine in several countries to treat different diseases. Liver diseases are major World wise health Problems. The Present aim of the study was evaluate The Antihepatotoxic effects of different fractions of Elephantopus scaber against Carbon tetrachloride (CCl4) induced hepatic damage in Rats. All the fractions were given orally in different doses (125mg/kg, 250mg/kg, 500mg/kg). The Antihepatotoxic effect was assessed by measuring serum parameters like  aspertate transaminase (AST), alanine transaminase (ALT), Alkaline Phospatase (ALP) and total bilurubin.  All the fractions of Elephantopus scaber showed Antihepatotoxic effect.The ethanol fraction was shows significant percentage protection than compared to other fractions. Therefore, our study supports the isolation and use of active constituents from Ethanol fraction of Elephantopus scaber in treating of liver disease

Qualitative and quantitative phytochemical screening and in vitro anti oxidant and anti microbial activities of Elephantopus scaber Linn.

Preliminary phytochemical analysis and quantification of total phenols, In-vitro antioxidant and anti microbial activities of the different fractions (hydro alcoholic, hexane, ethyl acetate and methanol) of Elephantopus scaber were carried out against five selected pathogenic bacteria and three fungal species. The plant fraction possesses steroids, triterpinoids, saponins, flavonoides, carbohydrates, glycosides and oils. For total phenolic content gallic acid was taken as a standard, the ethyl acetate fraction contains rich phenolic content than other fractions and the methanol fraction shows more DPPH, superoxide and hydroxyl radical scavenging activity. In Anti-microbial activity study all fractions showed good inhibition zone against three organisms i.e., Escherichia coli, Staphylococcus aureus Klebsiella pneumonia among the other test organisms along with Candida spp (fungal organism)

Shielding Effectiveness of Laminated Shields

Shielding prevents coupling of undesired radiated electromagnetic energy into equipment otherwise susceptible to it. In view of this, some studies on shielding effectiveness of laminated shields with conductors and conductive polymers using plane-wave theory are carried out in this paper. The plane wave shielding effectiveness of new combination of these materials is evaluated as a function of frequency and thickness of material. Conductivity of the polymers, measured in previous investigations by the cavity perturbation technique, is used to compute the overall reflection and transmission coefficients of single and multiple layers of the polymers. With recent advances in synthesizing stable highly conductive polymers these lightweight mechanically strong materials appear to be viable alternatives to metals for EM1 shielding

Dynamics of Magnetized Bulk Viscous Strings in Brans-Dicke Gravity

We explore locally rotationally symmetric Bianchi I universe in Brans-Dicke gravity with self-interacting potential by using charged viscous cosmological string fluid. We use a relationship between the shear and expansion scalars and also take the power law for scalar field as well as self-interacting potential. It is found that the resulting universe model maintains its anisotropic nature at all times due to the proportionality relationship between expansion and shear scalars. The physical implications of this model are discussed by using different parameters and their graphs. We conclude that this model corresponds to an accelerated expanding universe for particular values of the parameters.Comment: 17 pages, 6 figure

Isolation of a new isomer of (+)-leucofisetinidin from Cassia marginata leaves

Cassia marginata Roxb. (family: Leguminosae) is a small deciduous tree growing in the forests from South Arcot to Travancore (India) and often planted for 0rnament. The bark of the tree is a good tanning material and has been found to be a substitute for wattle and avaram. The present communication describes the isolation and identification of (+)-catechin, butein 4'-glucoside (coreopsin), and a new dextrorotatory isomer of leucofisetinidin from the Cassia marginata leaves. (+)-Catechin and butein 4'-glucoside were separated by cellulose column chromatography; the former was identified by comparison of its infrared spectrum, analytical values, and R, values with those of the authentic sample and also by mixed melting points of the compound and its derivatives with authentic samples. Butein 4'-glucoside (coreopsin) was identified by thoroughly comparing it with an authentJic sample. The presence of butein 4'-glucoside (coreopsin) was earlier noticed in several plants. Though the compound seems to occur widely in nature, its presence in a Leguminosae plant is noted for the first time. The (+)-leucofisetinidin was found to be a new dextrorotatory isomer of 7,3',4'-trihydroxyflavan-3,4-diol, since the melting points and rotation of this compound and its derivatives (see Experimental) were quite different from those of the corresponding isomers of (+)-7,3',4'-trihydroxyflavan-3,4-diol

A dynamics-driven approach to precision machines design for micro-manufacturing and its implementation perspectives

Precision machines are essential elements in fabricating high quality micro products or micro features and directly affect the machining accuracy, repeatability and efficiency. There are a number of literatures on the design of industrial machine elements and a couple of precision machines commercially available. However, few researchers have systematically addressed the design of precision machines from the dynamics point of view. In this paper, the design issues of precision machines are presented with particular emphasis on the dynamics aspects as the major factors affecting the performance of the precision machines and machining processes. This paper begins with a brief review of the design principles of precision machines with emphasis on machining dynamics. Then design processes of precision machines are discussed, and followed by a practical modelling and simulation approaches. Two case studies are provided including the design and analysis of a fast tool servo system and a 5-axis bench-top micro-milling machine respectively. The design and analysis used in the two case studies are formulated based on the design methodology and guidelines