Investigation on the Effect of Mold Constraints and Cooling Rate on Residual Stress During the Sand-Casting Process of 1086 Steel by Employing a Thermomechanical Model

In this study, the effects of mold constraints and cooling rate on residual stress were analyzed during the shaped casting process. For this purpose, an H-shaped sample was designed in which the contraction of its middle portion is highly restricted by the mold during the cooling process. The effects of an increasing cooling rate combined with mold constraints were analyzed by reducing the thickness of the middle portion in the second sample. A three-dimensional coupled temperature-displacement analysis was performed in finite-element code ABAQUS to simulate residual stress distribution, and then numerical results were verified by the hole-drilling strain-gauge method. It was concluded that the mold constraints have a greater effect on the values of residual stress than the cooling rate (thin section) in steel sand casting. Increasing the cooling rate would increase the amount of residual stress, only in the presence of mold constraints. It is also suggested that employing the elastic-plastic stress model for the sand mold will satisfy the experimental results and avoid exaggerated values of residual stress in simulation.     

Assessment of the dynamic effect of steel frame due to sudden middle column loss

The term progressive collapse is typically used to refer to the spread of an initial local failure within a structure. This paper proposes a new and simple method to calculate of the dynamic load amplification factor due to sudden column loss within a progressive collapse event in a structure. The conceptual basis of this method is the ability of the remaining structure after column loss to transfer the kinetic energy. Five principal stages are used in this research to achieve its purpose: (1) achieving the nonlinear static response of the remained structure to load using finite element method, (2) using the conceptual ductility at the maximum level of dynamic deformation to calculate the amplification factor, (3) designing a flowchart to determine the dynamic load amplification factor versus a ratio load, (4) achieving a series equation based on the statistical analyses to calculate dynamic load amplification factor and (5) designing a simplified graph using the results achieved from the previous stages. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of reprocessing on shrinkage and mechanical properties of ABS and investigating the proper blend of virgin and recycled ABS in injection molding

In this research, the effect of reprocessing of acrylonitrile–butadiene–styrene (ABS) on the mechanical properties of the polymer was studied through a five-stage reprocessing. To this end, the injection mold of the standard samples was manufactured. Then, using an injection molding machine, all of the virgin material was processed. After sampling, the rest of the parts were ground and then reprocessed under the same conditions. In order to get a proper combinational ratio of virgin and recycled ABS with respect to shrinkage and mechanical properties, another experiment was designed. In order to do this, virgin material was blended with 20%, 35% and 50% of the recycled material. The blends were reprocessed and samples were obtained. Impact, tensile, flexural and shrinkage tests, selected from ASTM standard, were used to investigate the mechanical properties of the polymer as well as its shrinkage. Furthermore, viscosity test was used to investigate the changes in the structure of the polymer. As the reprocessing cycles increased, shrinkage decreased and tensile and flexural ultimate strengths increased, more in flexural strength than in tensile. While Young's modulus slightly increased, viscosity decreased and consequently molecular weight decreased too. The proper blend for the least shrinkage was 50% whereas the best mechanical properties were achievable by the 20% blend. The obtained results suggest that reprocessing causes polymer degradation which is a result of the break in the bonds of poly butadiene. Moreover, it can be concluded that reprocessing in ABS can lead to the loss of effectiveness of some additives.     

FLEXIBLE MANUFACTURING SYSTEMS

Many existing manufacturing facilities and production methods, unable to satisfy global market needs, have become obsolete. Today's marketplace demands a form of manufacturing that is completely different from traditional operational batch manufacturing systems. More plant managers are accepting and implementing new technologies known as flexible manufacturing systems (FMSs).     

Data-Fusion Approaches and Applications for Construction Engineering

Data fusion can be defined as the process of combining data or information for estimating the state of an entity. Data fusion is a multidisciplinary field that has several benefits, such as enhancing the confidence, improving reliability, and reducing ambiguity of measurements for estimating the state of entities in engineering systems. It can also enhance completeness of fused data that may be required for estimating the state of engineering systems. Data fusion has been applied to different fields, such as robotics, automation, and intelligent systems. This paper reviews some examples of recent applications of data fusion in civil engineering and presents some of the potential benefits of using data fusion in civil engineering.     

Fluid flow characterization of liquid�Cliquid mixing in mixer-settler

Agitation in a mixer-settler is one of the most common operations, yet presents one of the greatest challenges in the area of computer simulation. Mixer-settlers typically contain an impeller mounted on a shaft, and optionally can contain baffles. The hydrodynamic characteristics of mixer-settlers have been studied in the present study. The effect of different geometrical parameters on the efficiency characteristics of the system has been investigated. The effects of different width of impellers, impeller speed, inlet velocity, impeller diameter, etc. have been studied. Computational fluid dynamics (CFD) model has been developed to predict the efficiency characteristics. The model has been validated with the help of experimental data for different velocity outlets used in the work. This work has enabled developing efficiency that can produce higher condition than those reported in previous literature. From the CFD simulations results, optimum mixer-settler geometry has been proposed.     

The use of Artificial Neural Network models for CO2 capture plants

Artificial Neural Networks (ANN) are multifaceted tools that can be used to model and predict various complex and highly non-linear processes. This paper presents the development and validation of an ANN model of a CO₂ capture plant. An evaluation of the concept is made of the usefulness of the ANN model as well as a discussion of its feasibility for further integration into a conventional heat and mass balance programme. It is shown that the trained ANN model can reproduce the results of a rigorous process simulator in fraction of the simulation time. A multilayer feed-forward form of Artificial Neural Network was used to capture and model the non-linear relationship between inputs and outputs of the CO₂ capture process. The data used for training and validation of the ANN were obtained using the process simulator CO2SIM. The ANN model was trained by performing fully automatic batch simulations using CO2SIM over the entire range of actual operation for an amine based absorption plant. The trained model was then used for finding the optimum operation for the example plant with respect to lowest possible specific steam duty and maximum CO₂ capture rate. Two different algorithms have been used and compared for the training of the ANN and a sensitivity analysis was carried out to find the minimum number of input parameters needed while maintaining sufficient accuracy of the model. The reproducibility shows error less than 0.2% for the closed loop absorber/desorber plant. The results of this study show that trained ANN models are very useful for fast simulation of complex steady state process with high reproducibility of the rigorous model.     

Formation of Nano/Ultrafine Grains in AISI 321 Stainless Steel Using Advanced Thermo-Mechanical Process

Production of nano/ultrafine grains through deformation-induced martensite formation and its reversion to austenite in an AISI 321 stainless steel was studied.The repetitive cold rolling and subsequent annealing were conducted to obtain nanocrystalline structure.Heavy cold rolling(90% reduction) at ?20 and-20 °C was carried out to induce the formation of a9-martensite from metastable austenitic material.The process was followed by annealing treatment at700–900 °C for 0.5–30 min.Effects of process parameters,i.e.,‘‘reduction percentage,' ‘‘rolling temperature,' ‘‘annealing temperature' and ‘‘annealing time',on the microstructural development were considered.Microstructural evolutions were conducted using feritscope,X-ray diffractometer and scanning electron microscope.Hardness of the specimens was measured by Vickers method.Results revealed that the higher thickness reduction and lower rolling temperature provided more martensite volume fraction and further hardness.X-ray diffraction patterns and feritoscopic results indicated that saturated strain(es) was reduced from 2.3 to 0.9 when temperature declined from ?20 to-20 °C.The smallest grain size(about 70 nm) was achieved in the condition of cold rolling at-20 °C followed by annealing at 750 °C for 5 min.     

Microstructure Modification of Powder Compact of Al-Zn-Mg Nanostructured Alloy by a Semisolid Thermomechanical Processing

A thermomechanical process(TMP) consisting of three cycles of cold pressing at 154 MPa and liquid-phase sintering at 600 ℃ for 30 min in each cycle was applied to modify the microstructure of nanostructured Al-Zn-Mg alloy.The alloy powders were produced by mechanical alloying.Also,solid-state sintering at 550 ℃ for 90 min was done to compare the results with those obtained from the TMP.The powders and the thermomechanically(TM) processed samples were analyzed by XRD to reveal the present phases in addition to calculating the crystallite size changes by the Williamson-Hall method.Moreover,scanning electron microscope was employed to observe the morphology of the powder and the microstructures of the sintered and the TM processed samples.The results revealed that the TMP affected the microstructure noticeably as well as the microhardness by removing the continuous grain boundary porosities and uniform distribution of the intermetallic phase particles as well as obtaining a near globular microstructure after the second cycle.Also,the average grain sizes in the first and the second cycles of the TMP were lower than those of the sintered sample.Furthermore,nanocrystalline grains were stable up to the second cycle of the TMP.     

Effects induced by gamma irradiation on free‐volumes,mechanical, and thermal properties of flame‐ and non flame‐retardant polyvinylchloride

Flame‐retardant polyvinylchloride (FRPVC),typically used in cable insulation and jacketing construction for multi‐purpose reactor (MPR) at Atomic Energy Authority of Egypt, as well as carbon‐black FRPVC (CB‐FRPVC) and nonflame‐retardant PVC and CB‐PVC materials produced by Egyptian Electrical Cable Company (EECC), have been irradiated up to 160 KGy, at room temperature with a ⁶⁰Co gamma source. Free‐volumes and thermal stability of irradiated and nonirradiated PVC samples have been examined using positron annihilation Lifetime Spectroscopy (PALS) and thermogravimetric analysis (TGA). In addition, the mechanical properties: tensile strength and elongation at break were examined. Considerable presence of flame‐retardant and carbon black additives in CB‐FRPVC sample led to both quenching and inhibition of Ps formation. The mechanical and thermal characterization showed that irradiation of PVC samples up to 80 KGy effectively induced cross‐linking to maxima. Higher doses then after results in degradation and thus a decrease in mechanical strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009