Herein, attempts are made to estimate the mechanical properties using microstructure-based finite element (FE) modeling and validate these results with the experimental results. The two high-carbon steel specimens are hot-rolled and air-cooled to develop ferrite–pearlite microstructures. Different characterizations are utilized to observe microstructures as well as Vickers hardness and tensile tests are carried out to determine the mechanical properties. Two high-resolution scanning electron micrographs are chosen for representative volume element-based FE analyses for modeling the mechanical behavior of ferrite–cementite microstructure. Object-oriented finite elements (OOF2) and Abaqus FEA 6.14 software are used to estimate the elastic and elastoplastic behavior assuming plane stress conditions. The correlation between cementite lamellae orientation and the predicted elastoplastic properties is investigated and compared with the experimental results. The influence of image size and mesh size on the predicted true stress–true strain behavior is discussed. The hard and brittle cementite lamellae face maximum stress while the softer ferrite matrix experiences maximum strain. It is found that strain accumulation is maximum at the interfaces of ferrite and cementite. These findings are further validated by the microvoid and crack initiation spots in the fracture surface and subsurface micrographs of broken tensile specimens. 相似文献
It is difficult to reduce the ash content in Indian coals below a certain level by conventional physical beneficiation techniques due to their poor washability characteristics. In the present work, the effect of aqueous alkali leaching at elevated temperature, followed by acid washing on the removal of mineral matter, was evaluated for different captive coals of Tata Steel. The research study revealed that the ash content of all these coals could be reduced by more than 50% using this method. The degree of demineralization improved by increasing the reaction time, alkali concentration, and temperature, and by reducing the coal particle size. No significant change was observed in the alkali content, whereas silica, alumina, and phosphorous content reduced significantly after the final acid treatment. The mechanism of demineralization was evaluated by analyzing the coal samples before and after the alkali and acid treatments using X-ray diffraction (XRD) techniques. Overall, this study provides an insight into possible alternative methods of beneficiation for removal of ash from physically beneficiated high-ash Indian coals. 相似文献
A unified model is developed for the analysis of heat transfer (radiation and non-Fourier conduction) in an axisymmetric participating medium. The proposed model includes three different variants of hyperbolic–parabolic heat conduction models, that is, the single phase lag model, dual phase lag model, and the Fourier (no phase lag) model. The radiating-conducting medium is radiatively absorbing, emitting, and isotropically scattering. Significance of all the above mentioned models on the heat transfer characteristics is investigated in a two-dimensional axisymmetric geometry. The equation of transfer and the coupled non-Fourier conduction-radiation equation are solved via finite volume method. A fully implicit scheme is used to resolve the transient terms in the energy equation. For spatial resolution of radiation information, the STEP scheme is applied. Tri-diagonal-matrix-algorithm is used to solve the resulting set of linear discrete equations. Effects of two important influencing parameters: the scattering albedo and the radiation- conduction parameter are studied on the temporal evolution of temperature field in the radiatively participating medium. The non-Fourier effect of heat transport captured well with the proposed unified model. A good agreement can be found between the proposed model predictions and those available in the literature. It is also found that when the phase lag of the temperature gradient and the heat flux are the same, it reduces to conventional Fourier conduction-radiation and the wave behavior diminishes. However, the reduction to this Fourier model fails in the presence of constant blood perfusion and metabolic heat generation. 相似文献
This paper reports about the discharge characteristics of jatropha biodiesel blends along with producer gas from waste babul wood pieces in a dual-fuel direct injection diesel engine. The biodiesel blends were examined in both individual and dual-fuel modes at a constant gas flow rate of 21.69 kg/h at all loading conditions. From the results it may be concluded that oxides of nitrogen and smoke opacity reduce, whereas carbon dioxide (CO2), carbon monoxide (CO), and hydrocarbon (HC) increase for all test fuels in dual-fuel operation compared with that of a single style at different loading conditions. The fuel blends show better emissions than that of diesel in both the ways. 相似文献
Microcombustion is a promising method for fulfilling the energy requirements of small-scale systems currently powered by portable batteries. However, its applications rely upon mitigation of heat losses, which adversely affect flame stability and performance. Heat losses in turn depend upon wall properties, especially thermal conductivity. It is thus necessary to systematically investigate the relationship between wall thermal conductivity and microcombustor performance using the exergy analysis. In this work, entropy generation rates of different irreversible processes in an annular microcombustor were computed for stoichiometric hydrogen-air mixture using CFD simulations of reactive flow for wall thermal conductivities in the range 0.1-325 W/m K. Chemical reaction, heat conduction, and mass diffusion were the dominant contributors to entropy generation, in the decreasing order. Irreversibilities due to combustion decreased as thermal conductivities increased. Diffusion contributions were most sensitive to the changes in thermal conductivity but chemical reaction and heat conduction contributions changed marginally. Results showed that walls did not contribute significantly to entropy generation, but increased wall heat losses at higher thermal conductivities adversely affected the exergetic performance of microcombustor through availability losses and by influencing the flow gradients. Based on the results of this study, wall thermal conductivity in the range 0.1-1.75 W/m K was found suitable in order to obtain uniform wall temperature profiles and high exergetic efficiencies. 相似文献
This paper presents a resilient localization scheme for wireless sensor networks (WSNs). It suits well in estimation of node position under a corrupted radio environment. Position computation is based on information of angle-of-arrivals (AoA) and references obtained from a few mobile anchors. In the network, anchors are equipped with smart antennas and global positioning system receivers. They broadcast signals in a synchronous and periodic fashion. The neighboring nodes having the signals with received signal strength values above a prescribed threshold level, respond with their respective IDs. Anchors evaluate AoA information from these signals using estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm. Next, they forward beacon messages, containing their references and estimated angles, to the corresponding nodes and move along random trajectories. After receiving three sets of such data, at least, nodes can initiate selective segregation of the inconsistent position estimations. Simulation results attaining higher degree of localization accuracy validate its competency over the existing schemes.
A radio wave attenuation measurement survey program was undertaken for the tropical rain forests of India. Measurements were taken at frequencies from 50 to 800 MHz, for antenna heights from 1.5 to 16.5 m above the ground with both horizontally and vertically polarized emissions, and at various separation distances varying from 40 to 4000 m. There were 96 combinations of system parameters for each selected distance between transmitting and receiving locations. In addition to the copolar measurements, cross-polar measurements were carried out to study cross-polar phenomenon in the presence of vegetation. The results of the studies are discussed, covering scatter of the data, lack of homogeneity of the foliage, variation in foliage proximity of the antenna, scattering of radio waves, effect of antenna beamwidth, effect of changes in wind velocity, frequency and polarization dependence of the basic transmission loss, seasonal variation of the loss, effect of climate and type of vegetation, foliage loss, specific attenuation, and effect of increased antenna height in the forest. An empirical model derived from these measurements is proposed 相似文献