Fatigue fracture surface analysis in C45 steel specimens using X-Ray fractography

X-Ray fractography is a useful technique to analyse the mechanisms operating in fracture and involves an examination of the fracture surface. In the present investigation, this technique has been employed to study the fatigue fracture behaviour of a medium carbon steel of C45 grade in different heat treated conditions. The different trends observed in the residual stress (σr) and diffraction profile full width at half maximum intensity (B) relationships with the maximum stress intensity factor (Kmax) on the fracture surface have been correlated to the differences in flow characteristics of these materials. The root mean square value of microstrain , and the coherent domain (particle) size, D, were determined through single line diffraction profile (Voigt's) analysis. It has been observed that contribution of microstrain to profile broadening is more significant than that due to domain size. However, at higher Kmax values an influence of D was found on line broadening, to a small extent. Results of sub-surface stress measurements were compared in two conditions. A good correlation was noticed between the depths below the fracture surface, designated as ymax, at which the measured σr, reaches the base material value and the corresponding monotonic plastic zone size (rp) obtained by calculation. The observed depths below the fracture surface (ypeak) at which an increase in σr or a decrease in B was noticed, appear to be related to the conditions of the near-tip regions where the material has undergone severe fatigue damage and cyclic softening

Effect of pressure on the phase transition behavior of ammonium nitrate

Ammonium nitrate (AN) is used as oxidizer in solid propellants, explosives, gas generator systems and also as a fertilizer. AN crystallizes in five polymorphic phases that appear at different temperatures. Phase transition of AN from one polymorphic phase to another is very important as an oxidizer and also as fertilizer. During its use as an oxidizer, whether pressure plays any role in phase transition is described in this paper. High Pressure−Differential Thermal Analysis (HP−DTA) system is used for this study

Some studies on the influence of stress ratio and test temperature on X-ray fractography observations in C45 steel specimens

This paper deals with additional ¿X-ray fractography¿ observations made on C45 steel, subsequent to the earlier work [K. Rajanna, B. Pathiraj and B. H. Kolster, Fatigue fracture surface analysis in C45 steel specimens using X-ray fractography. Engng Fracture Mech. 39, 147¿157 (1991)]. Fatigue crack: growth tests were carried out at 20°C on CT samples prepared from this steel using different stress ratios (0.1R, 0.5R and 0.7R). Tests were also carried out at different temperatures (¿20°C, 20°C and 115°C) using a stress ratio of 0.1. The fractured surfaces were analysed for their residual stress state. The influence of the test conditions on the residual stresses developed is discussed

Combined anticonvulsant effect of nifedipine and pentazocine in experimentally induced seizures in rats

Background: Epilepsy is one of the common disorders of human with a prevalence of approximately 1% of the total population. Majority of seizures can be controlled with available antiepileptic drugs, about 20% of them still remain resistant to treatment. Recognizing this, there is a need to develop newer antiepileptic drugs with therapeutic potential. Present work is based upon the production of convulsions by maximal electroshock in rats. Evaluation of combined anticonvulsant effect of nifedipine and pentazocine on the duration of convulsion and duration of tonic hind limb extension and recovery in rats.Methods: The study was commenced after obtaining approval from IAEC, Department of Pharmacology, Osmania Medical College, Koti, Hyderabad. All the wistar rats were induced convulsions by Maximal Electro-Shock (MES) method and rats showing tonic hind limb extension response were randomised into four groups (six animals in each group). Group 1 received distilled water, group 2 treated with nifedipine 10mg/kg BW, group 3 treated with pentazocine 30mg/kg BW and group 4 treated with both nifedipine 10mg/kg BW and pentazocine 30mg/kg BW. Drug administered by intraperitoneal route. The data analysed using ANOVA and group means with LSD Post Hoc Test. p‐values <0.05 were considered as significant.Results: When nifedipine and pentazocine were combined, the mean duration of convulsions, tonic hind limb extension and recovery were significantly decreased compared to control, nifedipine and pentazocine.Conclusions: The results obtained in this study provide supporting pharmacological evidence of efficacy, possible potential benefit of combining nifedipine with pentazocine in epilepsy

A Preliminary Study on Phytoplankton in Fresh Water-Lake of Gogi, Yadgir District, Karnataka

The present study was conducted in a semi arid region of Karnataka. The study discusses the phytoplankton diversity of the Gogi lake ecosystem. A standard methodology was followed in conducting to complete this study and samples were collected at different points from the lake ecosystem located at the core area of the proposed uranium mining site. Through a field survey, twenty one species of phytoplankton were recorded coming under four classes viz., Bacillariophyceae(8), Chlorophyceae(7),Cyanophyceae (5) Charophyceae (1) and twelve families and Fragilariaceae (4), Bacillariaceae (3), Zygnemataceae(3), Desmidiaceae (2), Oscillatoriaceae (2), Melosiraceae (1), Cladophoraceae (1), Scenedesmaceae (1), Microcystaceae (1), Nostocaceae (1), Phormidiaceae (1), Characeae (1). The data were collected over two seasons- March to May and September to November -2012. A total of 21 species were recorded from the study region of which 10 species were recorded during March to May, while 02 species from September to November, nine species were recorde

Crushing and Grinding Practice at Ingaldhal Copper mines

Ingaldhal copper mines are situated in the Bangalore -- Bombay National Highway about 10 Kms from Chitradurga town (Karnataka State). The main mineral is chalcopyrite ( Cu FeS2 ) occuring as a vein deposit in chlorite schist, the thicknes of the veins varying from 60 cms to 18 cms. The estimated reserves of developed and blocked out ore is 0.2 million tonnes of grade 1.23% Cu. Probable reserves are one million tonnes at 1.0% copper.The ore from the under ground mines is hoisted up and stored in the surface ore bins. It is transported by trucks to the hopper of the crushing unit

Ru (III) Catalyzed Oxidation of Aliphatic Ketones by N-Bromosuccinimide in Aqueous Acetic Acid: A Kinetic Study

Kinetics of Ru (III) catalyzed oxidation of aliphatic ketones such as acetone, ethyl methyl ketone, diethyl ketone, iso-butylmethyl ketone by N-bromosuccinimide in the presence of Hg(II) acetate have been studied in aqueous acid medium. The order of [N-bromosuccinimide] was found to be zero both in catalyzed as well as uncatalyzed reactions. However, the order of [ketone] changed from unity to a fractional one in the presence of Ru (III). On the basis of kinetic features, the probable mechanisms are discussed and individual rate parameters evaluated

DESIGN AND OPTIMIZATION OF BULK MICROMACHINED ACCELEROMETER FOR SPACE APPLICATIONS

The accelerometers used for Inertial Navigation in satellite launch vehicles demand excellent performance in terms of sensitivity, noise immunity, linearity, bias and scale factor stability over time and environmental changes. Detailed and in-depth design of the microstructure by computer simulation is required to ensure structural integrity and reliability of the microstructure. The microstructure of the accelerometer consists of a proof mass suspended from the mounting frame by beam springs. Extensive Finite Element simulation of the silicon microstructure has been carried out to obtain application specific optimum design parameters. Based on the deflection, frequency and stress analyses the optimum geometry and dimensions of the accelerometer have been determined. Noise analysis has been carried out, the performance of the accelerometer has been predicted and its compliance to the expected performance is ensured