Effect of Binder Composition on the Shrinkage of Chemically Bonded Sand Cores

Modern foundries increasingly use chemically bonded no-bake sand cores and molds because they provide ease of molding, good surface finish, and collapsibility. One of the most popular binder systems is alkyd oil urethane no-bake system comprising three parts: alkyd resin, catalyst, and crosslinking agent. Their amounts and ratios can influence mold shrinkage, and thereby dimensional quality of the resulting casting. With rising emphasis on net-shape casting, there is a need to optimize the binder composition to minimize dimensional errors, while achieving the desired bench life, stripping time and hardness. This work investigates the effect of binder composition on the dimensions of chemically bonded sand cores with respect to time. The maximum shrinkage of 0.15% over length was observed when resin content was 2.4% by weight of sand. The rate of shrinkage increased with the amount of catalyst. Measurement of core hardness and reduction in weight, followed by SEM studies, provided a better understanding of the underlying phenomena, especially formation of resin bridges between compacted sand particles and evaporation of solvent. This work is expected to aid in selection of the most appropriate binder composition for a given set of molding process constraints and cast product requirements.     

Experimental analysis of Deccan hemp oil as a new energy feedstock for compression ignition engine

This study investigates the biodiesel from Deccan hemp oil and its blends for the purpose of fuelling diesel engine. The performance and emission characteristics of Deccan hemp biodiesel are estimated and compared with diesel fuel. The experimental investigations are carried out with different blends of Deccan hemp biodiesel. Results show that brake thermal efficiency is improved significantly by 4.15% with 50 BDH when compared with diesel fuel. The Deccan hemp biodiesel reduces NO_x, HC and CO emission along with a marginal increase in CO₂ and smoke emissions with an increase in the biodiesel proportion in the diesel fuel. The improvement in heat release rates shows an increase in the combustion rate with different percentage blends of Deccan hemp biodiesel. From the engine test results, it has been established that 30–50 BDH of Deccan hemp biodiesel can be substituted for diesel.     

Room-temperature multiferroic properties and magnetoelectric coupling in Bi4−x Sm x Ti3−x Co x O12−δ ceramics

We present the structural, dielectric, ferroelectric, magnetic and magnetoelectric studies of lead free; single phase Bi_4?x Sm _x Ti_3?x Co _x O_12?δ (0 ≤ x ≤ 0.07) ceramics, synthesized using a standard solid-state reaction technique. Raman spectroscopy analysis reveals the relaxation of distortion in TiO₆ octahedron. Field emission scanning electron microscopy confirmed the growth of plate-like grains. It is observed that with the substitution of Sm³⁺ and Co³⁺ ions the dielectric constant, loss tangent and ferroelectric transition temperature decreases. Electrical dc resistivity, remnant polarization and magnetization increases with increasing Sm³⁺ and Co³⁺ contents. The magnetoelectric coupling co-efficient, α = 0.65 mV cm^?1 Oe^?1 is realized for Bi_4?x Sm _x Ti_3?x Co _x O_12?δ (x = 0.07) ceramic sample. Our results clearly demonstrate the lead free, multiferroic nature of Sm/Co-substituted Bi₄Ti₃O₁₂, which may find useful application in designing cost-effective electromagnetic devices.     

Photoluminescence and color tunability of γ-irradiated Tb3+–Sm3+-codoped oxyfluoride aluminoborate glasses

The main goal of this paper is to generate a warm white light through γ-irradiated Tb³⁺/Sm³⁺-codoped oxyfluoride aluminoborate glasses under 387 nm excitation xenon lamp. The transparent Tb³⁺/Sm³⁺-codoped oxyfluoride aluminoborate glass samples were prepared by melt-quenching technique. The energy transfer mechanism between Tb³⁺ and Sm³⁺ ions with an emphasis on the role of Al₂O₃/Al³⁺ is systematically studied before and after γ-irradiation. The characteristics of white light emission defined by chromaticity color coordinates and correlated color temperature are evaluated. In the present glass systems, the tuning of cold-to-warm white light as a function of Al₂O₃ and γ-irradiation is demonstrated.     

Oxygen vacancy induced dielectric relaxation studies in Bi4−xLaxTi3O12 (x = 0.0, 0.3, 0.7, 1.0) ceramics

In the present work, oxygen vacancy induced dielectric relaxations were studied for Lanthanum substituted Bi_4?xLa_xTi₃O₁₂ (x = 0.0, 0.3, 0.7, 1.0) ceramics. X-ray diffraction patterns reveal the formation of single phase orthorhombic structure in all the samples. The partial substitutions of lanthanum ions were found to significantly influence the grain morphology of the sintered ceramics. Temperature dependent dielectric measurements indicate a well-defined dielectric constant peak around 150 °C, with strong frequency dispersion. This dielectric anomaly was attributed to the Maxwell–Wagner space charge relaxation phenomenon related to oxygen vacancies. The space charges related to oxygen vacancies were confirmed by annealing the samples in oxidative atmosphere. The electrical modulus analysis shows that the samples exhibit non-Debye type relaxation behavior. Doubly ionized oxygen vacancies were found to influence the relaxation behaviour at higher temperature. The observed dielectric relaxation as a function of temperature and frequency were explained on the basis of oxygen vacancies.     

The effect of stress state on high-temperature deformation of fine-grained aluminum–magnesium alloy AA5083 sheet

The effect of stress state on high-temperature deformation of fine-grained aluminum–magnesium alloy AA5083 sheet is investigated over a range of temperatures and strain rates for which the grain-boundary-sliding and solute-drag creep mechanisms govern plastic flow. Experimental data from uniaxial tension and biaxial tension are used in conjunction with finite-element-method simulations to examine the role of stress state. Three different material constitutive models derived from uniaxial tensile data are used to simulate bulge-forming experiments. Comparison of simulation results with bulge-forming data indicates that stress state affects grain-boundary-sliding creep by increasing creep rate as hydrostatic stress increases. Thus, creep deformation is faster under biaxial tension than under uniaxial tension for a constant effective stress. No effect of stress state is observed for solute-drag creep. A new material model that accounts for the effect of stress state on grain-boundary-sliding creep is proposed.     

A fatigue-to-creep correlation in air for application to environmental stress cracking of polyethylene

The present study was undertaken to determine whether the correlation between fatigue and creep established for polyethylene in air could be extended to environmental liquids. Fatigue and creep tests under various conditions of stress, R-ratio (defined as the ratio of minimum to maximum load in the fatigue loading cycle), and frequency were performed in air and in Igepal solutions. The load–displacement curves indicated that stepwise fatigue crack growth in air was preserved in Igepal solutions at 50 °C, the temperature specified for the ASTM standard. In air, systematically decreasing the dynamic component of fatigue loading by increasing the R-ratio to R = 1 (creep) steadily increased the lifetime. In contrast, the lifetime in Igepal was affected to a much smaller extent. The fatigue to creep correlation in air was previously established primarily for tests at 21 °C. Before testing the correlation in Igepal, it was necessary to establish the correlation in air at 50 °C. Microscopic methods were used to verify stepwise crack growth by the sequential formation and breakdown of a craze zone, and to confirm the fatigue to creep correlation. The crack growth rate under various loading conditions was related to the maximum stress and R-ratio by a power law relationship. Alternatively, a strain rate approach, which considered a creep contribution and a fatigue acceleration factor that depended only on strain rate, reliably correlated fatigue and creep in air at 50 °C under most loading conditions of stress, R-ratio and frequency. The exceptions were fatigue loading under conditions of R = 0.1 and frequency less than 1 Hz. It was speculated that compression and bending of highly extended craze fibrils were responsible for unexpectedly high crack speeds.     

Mobility and Layer 2 Tunnels

An increase in the size and requirements of a mobile workforce is driving the development of better mobility oriented services in terms of both content and connectivity. Even though traditional {Mobile IP} has been the primary means of providing mobility to nodes roaming between foreign networks, its extension to support the mobility of entire networks leads to an increase in the encapsulation overheads. In addition, the increasing perception within the mobile workforce as to the inadequacies of Layer 3 connectivity provided by traditional Mobile IP opens up the possibility of considering the mobility problem from a Layer 2 perspective.This paper presents a Layer 2 extension to the traditional implementation of Mobile IP by replacing the IP-IP tunnels of Mobile IP with L2TPv3 based Layer 2 tunnels. Simulations results obtained from performance evaluation indicate comparable performance of the proposed Layer 2 mobility solution with respect to traditional {Mobile IP} in terms of real-time and best-effort traffic streams. The proposed Layer 2 mobility solution increases the possible services available to mobile nodes with minimal performance degradation.Ravi Bhagavatula got his M.S degree from Wichita State University in 1998, and his PhD from Wichita State University in 2003. His research interests are in mobile wireless networking. He is currently with Cisco Systems Inc.Patricia Best received a Bachelor’s degree in computer engineering at Wichita State University, Kansas, in 2000, and a Ph.D. in electrical engineering at Wichita State University in 2004. She worked as a software engineer at LSI Logic and is currently a systems design and integration specialist at Spirit Aerosystems.Dr. Ravi Pendse is an Associate Vice President for Academic Affairs and Research, Wichita State Cisco Fellow, and Director of Advanced Networking Research Center at Wichita State University, Wichita, Kansas. He is a senior member of the IEEE. His research interests include ad hoc networks, network based aviation security.