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101.
Raw material handling areas in an integrated steel plant experience severe wear of engineering components. The use of hardfacing plates is one of the ways to combat this problem. Three commercial hardfacing Fe-Cr-C alloys of varying Cr content were deposited on mild steel base plate and studied in this work. Abrasive wear tests were conducted by using pin-on-disk tribometer in accordance with the ASTM G99. Microstructural characterization was done by using optical and scanning electron microscopes. Energy- and wavelength-dispersive spectroscopies were carried out to study the carbide type and distribution in the hardfaced deposit. It was observed that wear resistance increases with increasing Cr content in the alloy. Along with hardness, morphology and type of carbide are also important factors to decide the wear resistance. An attempt has been made to corelate the chemical composition, carbide morphology, and macrostructural features with wear properties of hardfacing alloys. 相似文献
102.
Kaushal Kishore Goutam Mukhopadhyay Manashi Adhikary 《Journal of Failure Analysis and Prevention》2018,18(6):1321-1326
Worm drives are commonly used where large reduction in speed and greater transfer of torque are required within a small space. Phosphor bronze is normally used material for this application owing to its lower coefficient of friction and good wear and fatigue properties. This work presents a failure analysis of a worm wheel. Analysis revealed that around 40% of the teeth of worm wheel were broken. Failure mode was identified to be intergranular brittle fracture using scanning electron microscopy. A number of casting voids could be observed. In addition, network of intermetallic phases were present along the grain boundaries. These phases were identified to be Cu3Sn and Ni3P using elemental mapping through wavelength dispersive spectroscopy technique. These phases were found to have significantly higher hardness compared to the matrix and their precipitation along grain boundaries made the alloy susceptible to intergranular fracture even under small increase in service stress than nominal level. 相似文献
103.
104.
VandeWalle Don; Ganesan Shankar; Challagalla Goutam N.; Brown Steven P. 《Canadian Metallurgical Quarterly》2000,85(6):996
This study replicates, integrates, and extends prior research on the dispositional, contextual, and cognitive antecedents of feedback-seeking behavior. Regression analysis was used to analyze data collected from a sample of salespeople (N?=?310) from 2 Fortune 500 companies. The study hypotheses were supported with the following results. First, the individual disposition of learning goal orientation and the contextual factors of leader consideration and leader initiation of structure influenced cognitions about the perceived cost and value of feedback seeking. Second, the strength of the relationship of learning goal orientation with the cost and value perceptions was moderated by the leadership style of the supervisor. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
105.
Rohit S. Deo 《时间序列分析杂志》2012,33(2):325-339
The restricted likelihood is known to produce estimates with significantly less bias in AR(p) models with intercept and/or trend. In AR(1) models, the corresponding restricted likelihood ratio test (RLRT), unlike the t‐statistic or the usual LRT, has been recently shown to be well approximated by the chi‐square distribution even close to the unit root, thus yielding confidence intervals with good coverage properties. In this article, we extend this result to AR(p) processes of arbitrary order p by obtaining the expansion of the RLRT distribution around that of the limiting chi‐squared and showing that the error is bounded even as the unit root is approached. Next, we investigate the correspondence between the AR coefficients and the partial autocorrelations, which is well known in the stationary region, and extend to the more general situation of potentially multiple unit roots. In the case of one positive unit root, which is of most practical interest, the resulting parameter space is shown to be the bounded p‐dimensional hypercube (?1, 1] × (?1, 1)p?1. This simple parameter space, in addition with a stable algorithm that we provide for computing the restricted likelihood, allows its easy computation and optimization as well as construction of confidence intervals for the sum of the AR coefficients. In simulations, the RLRT intervals are shown to have not only near exact coverage in keeping with our theoretical results, but also shorter lengths and significantly higher power against stationary alternatives than other competing interval procedures. An application to the well‐known Nelson–Plosser data yields RLRT based intervals that can be markedly different from those in the literature. 相似文献
106.
The scattering of elastic waves in polycrystalline materials is relevant for ultrasonic materials characterization and nondestructive evaluation (NDE). Diffuse ultrasonic backscatter measurements are used widely to extract the microstructural parameters such as grain size and also to detect flaws in materials. Accurate interpretation of experimental data requires robust scattering models. Line transducers are often used for ultrasonic experiments such that an appropriate model for these two-dimensional problems is needed. Here, a theoretical expression for the temporal diffuse backscatter is derived for such domains under a single-scattering assumption. The result is given in terms of transducer and microstructural parameters. In addition, the problem is examined in terms of numerical simulations using Voronoi polycrystals that are discretized using finite elements in a plane-strain formulation. The material properties of the individual Voronoi cells are chosen according to appropriate material distributions. Such numerical models also allow scattering theories, including the one discussed here, to be examined for well-controlled microstructures. Example numerical results for materials with varying degrees of scattering that are of common interest are presented. The numerical results are compared with the theory developed with good agreement. These results are anticipated to impact ultrasonic NDE of polycrystalline media. 相似文献
107.
Goutam De Samar Kumar Medda Sucheta De Sudipto Pal 《Bulletin of Materials Science》2008,31(3):479-485
Several noble metal nanoparticles doped sol-gel derived thin coloured films have been synthesized and characterized. These
are pure (Ag, Au, Cu and Pt), mixed/alloy (Ag-Cu, Au-Cu, Au-Ag and Au-Pt) nanoparticles in SiO2, Au in mixed SiO2-TiO2 and SiO2-ZrO2, Au and Ag nanoparticles in inorganic-organic hybrid film matrices etc. This investigation leads to the development of tailor-made
coloured coatings by tuning the surface plasmon resonance (SPR) band positions originating from the embedded nanometals by
controlling mainly (i) refractive index of the film matrices and (ii) nanoalloy composition. In the later case a new layer-by-layer
(two-layer) synthetic protocol has been developed to prepare binary nanoalloy particles with controlled atomic ratios. 相似文献
108.
Rahman Sabidur Ahmed Tanjila Ferdousi Sifat Bhaumik Partha Chowdhury Pulak Tornatore Massimo Das Goutam Mukherjee Biswanath 《Photonic Network Communications》2020,40(3):126-136
Photonic Network Communications - Optical multi-domain transport networks are often controlled by a hierarchical distributed architecture of controllers. Optimal placement of these controllers is... 相似文献
109.
Ajay Kumar Shukla Brahma Deo D. G. C. Robertson 《Metallurgical and Materials Transactions B》2013,44(6):1398-1406
The role of the air gap formed between scrap and a solidified metal shell at the beginning of the scrap dissolution process has been investigated. The effect of air gap has been investigated for different Biot numbers (10 to 100) and ratios of air gap to liquid melt heat transfer coefficient (0.1 to 0.9). The predictions of the mathematical model are compared with the experimental results reported elsewhere. The role of air gap is found to be significant only for low Biot numbers (<50) and for low ratios of air gap to liquid melt heat transfer coefficient (<0.25). 相似文献
110.
In general mass measurements are carried out in air and that’s why air buoyancy correction plays a major role in mass measurements and it is totally dependent on density of air of the laboratory during the measurement. The density of air is calculated from temperature, relative humidity, air pressure, concentration of CO2 monitored (for CIPM formula only) in the laboratory rather direct determination and for calculation of density of air, CIPM-2007 formula is recognized as most accurate formula. Since CIPM formula is very complicated formula and it is not required for less accurate measurements, different National Metrology Institutes have derived simple equations to calculate air density and those are known as approximation formulas. We had gone through a comparative analysis among different formulas of density of air to evaluate which approximation formula is most accurate compare to CIPM-2007 formula. 相似文献