Optimization of the forging of aerofoil blade using the finite element method and fuzzy-Pareto based genetic algorithm

In this research non-isothermal forging process of an aerofoil blade was simulated using 3-dimentional finite element method. Then an optimization approach integrated with the finite element method has been applied to optimize the blade forging process. Preform shape and angular position of the die parting line were optimized in order to minimize the flash volume, strain non-uniformity and lateral forces generated during the forging operation. The optimization method includes the finite element approach and the response surface method for the formulation of the objective functions. Using the multi-objective genetic algorithm, Pareto front of global optimal solutions was generated. Then a fuzzy-based membership value assignment method was used to select the best compromise solution. The simulation of the blade forging process was verified by experimental test. Results show that the numerical results and experimental tests have a good agreement. Waste material and lateral forces generated during the forging operation is decreased with optimization method significantly. Therefore the proposed approach is an appropriate method for multi-objective optimization of the forging process of aerofoil blades.     

The effect of tube material, microstructure, and heat treatment on process responses of tube hydroforming without axial force

In this paper, the influence of tube material, microstructure, and heat treatment on process responses of tube hydroforming has been studied. One of the most important parameters in performing a successful tube hydroforming process is the selection of appropriate material for tubes. In the analysis section, effective parameters for the selection of an appropriate tube material for the hydroforming process have been investigated; it was concluded that higher strain hardening exponent (n), elasticity modulus (E), and anisotropy index (R) can enhance formability in this process; and the effects of microstructure and heat treatment on the formability of ASTM C11000 copper and ASTM AA1050 aluminum have been investigated. Consequently, four different heat treatment processes, which had different heating temperatures and durations, were selected, in addition to different cooling methods for each of the materials. In the experimental tests, the effects of these heat treatment methods on maximum bulging height, thickness strains, and final forming pressures were scrutinized. The effects of heat treatment on copper microstructure were also studied through metallographic tests; on the other hand, the effects of microstructure on tube hydroforming process were justified. As a result of these analyses, two heat treatment methods, namely, heating to 450 and 350 °C for 15 min and cooling in water, were recommended for copper and aluminum, respectively. Using these methods and due to their consequent fine and homogenous microstructure, higher mechanical strength and increase in material formability was achieved by attaining higher thickness strain and bulging height values. Finally, after extracting the mechanical properties of the two materials and comparing them with each other, parameters of strength coefficient and strain hardening exponent were reported as two effective factors that would improve tube deformation by tube hydroforming process.     

The Application of Response Surface Methodology for the Optimization of an Extractive Distillation Process

Abstract

There is ample opportunity to save energy consumption of an extraction distillation unit by optimizing the stripper operation. Applying a surface response technique determined that the stripping water injection rate and stripper base temperature have an impact on unit energy consumption, whereas the lean solvent circulation has no effect. Optimization of the stripping water injection rate will provide the greatest energy savings. On the other hand, the lean solvent circulation and stripper base temperature have a positive correlation on raffinate purity, whereas stripping water injection does not influence the purity. Stripper base temperature has the greatest impact on raffinate purity.     

High-order free vibrations of doubly-curved sandwich panels with flexible core based on a refined three-layered theory

There are few reports on the free vibration of soft core doubly-curved sandwich shells. Previous studies are largely based on the equivalent single layer theories in which the natural frequencies are grossly overestimated. This study deals with the analytical free vibrations of doubly curved sandwich shell with flexible core based on a refined general-purpose sandwich panel theory. In this theory, equations of motion are formulated based on displacements and transverse stresses at the interfaces of the core. The first order shear deformation theory and assumptions of linear distribution of transverse normal stress and uniform shear stresses over the thickness of core (based on 3D-elasticity solution of weak core) are used in the present theory. In this model, the in-plane displacements take cubic polynomial distributions and the transverse displacement has a quadratic one thorough the core thickness. Hamilton’s principle is used to obtain the equations of motion. The obtained results are validated by the analytical and numerical results published in the literatures. Parametric study is also included to investigate the effects of radius of curvature, thickness and flexibility of core.     

Deposition Patterns of Evaporating Sodium Alginate Sessile Droplets Cross-Linked by Calcium Chloride

Controllable patterning of bio-compatible polymers in the presence of a cross-linker in evaporating bi-dispersed colloidal drops is of critical importance in functional coatings, bioprinting, and food packaging. This study investigates the effect of calcium chloride and sodium alginate concentration on the evaporative deposition and elemental distribution of dried-out patterns. Different concentrations of alginate and salt in aqueous solutions are deposited on clean glass substrates to gain a deeper understanding of the final structures. Overall, the results indicate that changing the concentrations of sodium alginate and calcium chloride can significantly alter the elemental distribution and deposition uniformity of the final patterns. The modifications in relative concentration alter the physicochemical characteristics of the solution, resulting in significant changes in the pinning time and contact angle of the droplets that correspond to the alteration of the colloidal size and concentration, ultimately resulting in significant differences in deposition patterns. The dried-out patterns are categorized based on their structures and mechanisms (crystallization, sedimentation, and adsorption) controlling the evaporative deposition, and then justified based on the competitive effects of cross-linking, crystallization, and evaporation-driven flows. Using scanning electron microscopy and energy-dispersive X-ray spectroscopy, the elemental distribution of dried-out patterns is also mapped to substantiate the discussion made.     

Model Development and Parameter Estimation for the Oxidation of Pyrrhotite‐Containing Rock Surfaces

A novel experimental method was developed for the evaluation of the biotic oxidation rate of waste rock containing sulphide minerals. Sized waste rock samples were inoculated with an Acidithiobacillus ferrooxidans suspension and sparged with discontinuing humidified air to yield the oxygen consumption rate. A kinetic/mass transport model was proposed based on oxidation of pyrrhotite. Bayesian statistical analysis using the Metropolis‐Hastings algorithm showed that at ambient oxygen concentration the mean (i.e., estimated) values of the initial oxygen flux, the reaction order, the oxygen diffusion coefficient through the oxidation product layer, and the surface reaction rate constant were 1.3×10^?7 mol/m².s, 0.55, 2.91×10^?13 m²/s and 3.23×10^?7 mol^0.45/m^0.35.s, respectively.     

Comparison of Analytical,Numerical, and Experimental Methods in Deriving Fracture Toughness Properties of Adhesives Using Bonded Double Lap Joint Specimens

Stress and fracture analysis of bonded double lap joint (DLJ) specimens have been investigated in this paper. Numerical and analytical methods have been used to obtain shear- and peel-stress distributions in the DLJ. The generalized analytical solution for the peel stress was calculated for various forms of the DLJ geometry and, by using crack closure integral (CCI) and by means of the J-integral approach, the analytical strain energy-release rate, G, was calculated. Experimental fracture tests have also been conducted to validate the results. The specimens were made of steel substrates bonded by an adhesive and loaded under tension. Specimens with cracks on both sides and at either end of the DLJ interface were tested to compare the fracture behavior for the two crack positions where tensile and compressive peel stresses exist. Tests confirmed that the substrates essentially behave elastically. Therefore, a linear elastic solution for the bonded region of the DLJ was developed. The fracture energy parameter, G, calculated from the elastic experimental compliance for different crack lengths, was compared with numerical and analytical calculations using the experimental fracture loads. The stresses from analytical analysis were also compared with those from the finite element results. The strain energy-release rate for fracture, G _f , for the adhesive has been shown to have no R-curve resistance, was relatively independent of crack length, and compared well with those obtained from numerical and analytical solutions. However, it was found that fracture energy for the crack starter in the position where the peel stress was tensile was about 20% lower than where the crack was positioned at the side, where the peel stress was found to be compressive.     

Cluster analysis of antioxidant compounds in dates (Phoenix dactylifera): Effect of long-term cold storage

Both soft (SD, Bam) and dry (DD, Kharak) date varieties were stored at 4 °C for six months followed by an additional one week storage at 18 °C. Antioxidant compounds (total phenolic content (TPC) and total flavonoid content (TFC)) of the dates increased following storage. Cluster analysis applied on TPC and TFC data before and after storage obtained two statistically significant clusters of SD and DD indicating that TPC and TFC had different behaviors according to the types of dates. As antioxidant concentration in dates was dependent on type of dates, selection of variety with high antioxidant compounds may be recommended. Further cold storage of up to six months followed by one week storage at 18 °C may further improve the level of antioxidant compounds.     

Disinfection of dairy wastewater effluent through solar photocatalysis processes

Due to the strict regulations and reuse policies that govern wastewater's use as an irrigation water resource for agricultural purposes, especially in dry climates, optimization of the disinfection process is of the utmost importance. The effects of solar radiation along with Titanium dioxide(TiO_2) nanoparticles applied to optimization of the photolysis and photocatalysis processes for inactivating heterotrophic bacteria were investigated. Temperature, p H, and dissolved oxygen fluctuations in the dairy wastewater effluent treated by activated sludge were examined. In addition,different dosages of TiO_2 were tested in the solar photocatalysis(ph-C S) and concentrated solar photocatalysis(ph-C CS) processes. The results show that the disinfection efficiencies of the solar photolysis(ph-L S) and concentrated solar photolysis(ph-L CS) processes after 30 min were about 10.5% and 68.9%, respectively, and that the ph-C S and ph-C CS processes inactivated 41% and 97% of the heterotrophic bacteria after 30 min, respectively. The p H variation in these processes was negligible. Using the ph-L CS and ph-C CS processes, the synergistic effect between the optical and thermal inactivation caused complete disinfection after three hours. However, disinfection was faster in the ph-C CS process than in the ph-L CS process. Significant correlations were found between the disinfection efficiency and the variation of the dissolved oxygen concentration in the ph-C S and ph-C CS processes, while the correlations between the disinfection efficiency and temperature variation were not significant in the ph-L S and ph-C S processes. Moreover, the oxygen consumption rate was greatest(3.2 mg··L~(-1)) in the ph-C CS process. Hence,it could be concluded that the ph-C CS process is an efficient photocatalysis process for disinfection of dairy wastewater effluent.