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Search Results: 1 - 10 of 345843 matches for " S. Paul Vizhian "
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Microstructure and Mechanical Properties of as Cast Aluminium Alloy 7075/Basalt Dispersed Metal Matrix Composites  [PDF]
S. Ezhil Vannan, S. Paul Vizhian
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2014, DOI: 10.4236/jmmce.2014.23023
Abstract: This paper aims to study the effects of short basalt fiber reinforcement on the mechanical properties of cast aluminium alloy 7075 composites containing short basalt fiber of content ranging from 2.5 to 10 percent by weight in steps of 2.5 percent and fabricated using compo-casting technique. The objective is to investigate the process feasibility and resulting material properties such as young’s modulus, ductility, hardness & compression strength. The properties obtained are compared with those of as-cast that were manufactured under the same fabrication conditions. The results of this study revealed that, as the short basalt fiber content was increased, there were significant increases in the ultimate tensile strength, hardness, compressive strength and Young’s modulus, accompanied by a reduction in its ductility. Furthermore, the microstructure & facture studies were carried out using Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) in order to establish relationships between the quality of the fiber/aluminium interface bond and hence to link with mechanical properties of the composites.
Prediction of the Elastic Properties of Short Basalt Fiber Reinforced Al Alloy Metal Matrix Composites  [PDF]
Ezhil Vannan, Paul Vizhian
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2014, DOI: 10.4236/jmmce.2014.21010
Abstract: In this paper, a micro-mechanical model is implemented in software for the prediction of local mechanical properties of discontinuous short fiber reinforced composites. The model, based on the Mori and Tanaka method, shear-lag, computational model, Nielsen-Chen model and Miwa’s model is used to predict the elastic behaviour of basalt short fiber reinforced with Al alloy composites. The Al/basalt Metal Matrix Composites (MMCs) contain basalt short fiber from 2.5% to 10% in steps of 2.5 wt.% and are fabricated using squeeze infiltration technique. The effects of fiber length and orientation on elastic properties of Al/basalt MMCs are investigated. A comparison between the experimental data and the theoretical data based on physical models is made, and the significance of the findings is discussed. The results show that as short basalt fiber content was increased from 2.5% to 10% by wt.%, an improvement in Young’s modulus of 13.26% has been observed. Optical microscopy was used to examine the general microstructure and fiber distribution in the composite produced. Scanning Electron Microscopy (SEM) was performed on the fractured surface to understand the failure mechanisms.
A study of microstructure and wear behaviour of TiB2/Al metal matrix composites
Sreenivasan, A.;Paul Vizhian, S.;Shivakumar, N.D.;Muniraju, M.;Raguraman, M.;
Latin American Journal of Solids and Structures , 2011, DOI: 10.1590/S1679-78252011000100001
Abstract: the present paper deals with the study of microstructure and wear characteristics of tib2 reinforced aluminium metal matrix composites (mmcs). matrix alloys with 5, 10 and 15% of tib2 were made using stir casting technique. effect of sliding velocity on the wear behaviour and tribo-chemistry of the worn surfaces of both matrix and composites sliding against a en24 steel disc has been investigated under dry conditions. a pin-on-disc wear testing machine was used to find the wear rate, in which en24 steel disc was used as the counter face, loads of 10-60n in steps of 10n and speeds of 100, 200, 300, 400 and 500 rpm were employed. the results showed that the wear rate was increased with an increase in load and sliding speed for both the materials. however, a lower wear rate was obtained for mmcs when compared to the matrix alloys. the wear transition from slight to severe was presented at the critical applied loads. the transition loads for the mmcs were much higher than that of the matrix alloy. the transition loads were increased with increase in tib2 and the same was decreased with the increase of sliding speeds. the sem and eds analyses were undertaken to demonstrate the effect of tib2 particles on the wear mechanism for each conditions.
On the Definition of State Variables for an Internal State Variable Constitutive Model Describing Metal Deformation  [PDF]
Paul S. Follansbee
Materials Sciences and Applications (MSA) , 2014, DOI: 10.4236/msa.2014.58062
The quest for an internal state variable constitutive model describing metal deformation is reviewed. First, analogy is drawn between a deformation model and the Ideal Gas Law. The use of strain as a variable in deformation models is discussed, and whether strain serves as an internal state variable is considered. A simple experiment that demonstrated path dependence in copper is described. The importance of defining appropriate internal state variables for a constitutive law relates to the ability to accurately model temperature and strain-rate dependencies in deformation simulations.
Structure Evolution in Austenitic Stainless Steels—A State Variable Model Assessment  [PDF]
Paul S. Follansbee
Materials Sciences and Applications (MSA) , 2015, DOI: 10.4236/msa.2015.66049
Abstract: Strain hardening in austenitic stainless steels is modeled according to an internal state variable constitutive model. Derivation of model constants from published stress-strain curves over a range of test temperatures and strain rates is reviewed. Model constants for this material system published previously are revised to make them more consistent with model constants in other material systems.
Some Important Characteristics of Asset Bubbles and Financial Crises  [PDF]
Paul S. L. Yip
Modern Economy (ME) , 2018, DOI: 10.4236/me.2018.97075
Abstract: This paper first discusses the major characteristics of the seeding stage, the development stage and the final stage of an asset bubble. In particular, it emphasizes the role of expectation, some major changes in economic behaviors, financial leveraging, some important vicious cycles, upward spirals and herding behavior in the eventual development of an asset bubble. Thereafter, it discusses the policy implications of such an analysis. The second half of the paper extends the discussion to some important changes in economic behaviors, financial deleveraging, vicious cycles and downward spirals that would push an early-developed financial crisis into a full-blown economic crisis. Based on the characteristics and the experience of some major financial crises in the past few decades, the paper discusses policy measures that could be adopted during the crisis period and the post-crisis recession.
Analysis of Deformation in a High Entropy Alloy Using an Internal State Variable Model  [PDF]
Aaron Stein, Paul S. Follansbee
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.86033
Abstract: Deformation in the model high entropy alloy CoCrFeMnNi is assessed using an internal state variable constitutive model. A remarkable property of these alloys is the extraordinarily high strain hardening rates they experience in the plastic region of the stress strain curve. Published stress-strain measurements over a range of temperatures are analyzed. Dislocation obstacle interactions and the observed high rate of strain hardening are characterized in terms of state variables and their evolution. A model that combines a short-range obstacle and a long-range obstacle is shown to match experimental measurements over a wide range of temperatures and grain sizes. The long-range obstacle is thought to represent interactions of dislocations with regions of incomplete mixing or partial segregation. Dynamic strain aging also is observed at higher temperatures. Comparisons with measurements in austenitic stainless steel show some common trends.
Iris pigment in ocular melanomata
Paul S
Indian Journal of Ophthalmology , 1965,
Erythrocyte sedimentation rate in uveitis - a critical analysis
Paul S
Indian Journal of Ophthalmology , 1963,
Hyperspherical Partial Wave Theory with Two-term Error Correction
S. Paul
Physics , 2008, DOI: 10.1103/PhysRevA.77.052714
Abstract: Hyperspherical Partial Wave Theory has been applied to calculate T-matrix elements and Single Differential Cross-Section (SDCS) results for electron-hydrogen ionization process within Temkin-Poet model potential. We considered three different values of step length to compute the radial part of final state wave function. Numerical outcomes show that T-matrix elements and SDCS values depend on the step length h. Here, we have presented T-matrix elements and the corresponding SDCS results for 0.0075 a.u., 0.009 a.u. and 0.01 a.u. values of h and for 27.2eV, 40.8ev and 54.4eV impact energies. With the help of the calculated data for three different step lengths, we have been able to evaluate a two-term error function depending on the step length h. Finally, two-term error corrected T-matrix elements and the corresponding SDCS values have been computed. We fitted our two-term error corrected SDCS results by a suitable curve and compared with the benchmark results of Jones et al. [Phys. Rev. A, 66, 032717 (2002)]. Our fitted curves agree very well with the calculated results of Jones et al. and two-term error corrected SDCS results somewhere agree with the benchmark results. Two-term error corrected SDCS results are significantly better than the calculated SDCS results of different step lengths.
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