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Abstract This article discusses a multi-item planning and scheduling problem in a job-shop system with consideration of energy consumption. Planning is considered by a set of periods, each one is characterized by a demand, energy, and length. Scheduling is determined by the sequences of jobs on available resources. A Mixed-Integer Linear Programming (MILP) problem is formulated to integrate planning and scheduling, it is considered as an NP-difficult problem. A Genetic Algorithm (GA) is then developed to solve the MILP, and then a hybridized approach of simulated annealing with genetic algorithm (HGASA) is presented to optimize the results. Finally, numerical results are presented and analyzed to evaluate the effectiveness of the proposed algorithms.

Abstract Lightweight and high-strength high-pressure die casting (HPDC) aluminum has been widely used in automotive components such as the cylinder block, lower crankcase extension, transmission case, and drive unit. Die cast parts have good surface finishes with relatively higher material strength in the casting skin than the center core material, maintain consistent features and tolerance, and maximize metal yield, therefore making it the most cost-effective casting process for mass production of aluminum parts. However, due to the rapid filling rates, the HPDC process tends to form large porosity and oxides because of the entrapped gas and solidification shrinkage, thereby deteriorating the mechanical properties of the casting parts.

Abstract In subsonic aircraft design, the aerodynamic performance of aircraft is compared meaningfully at a system level by evaluating their range and endurance, but cannot do so at an aerodynamic level when using lift and drag coefficients, CL and CD , as these often result in misleading results for different wing reference areas. This Part I of the article (i) illustrates these shortcomings, (ii) introduces a dimensionless number quantifying the induced drag of aircraft, and (iii) proposes an aerodynamic equation of state for lift, drag, and induced drag and applies it to evaluate the aerodynamics of the canard aircraft, the dual rotors of the hovering Ingenuity Mars helicopter, and the composite lifting system (wing plus cylinders in Magnus effect) of a YOV-10 Bronco. Part II of this article applies this aerodynamic equation of state to the flapping flight of hovering and forward-flying insects.

Abstract Part I introduced the aerodynamic equation of state. This Part II introduces the aerodynamic equation of state for lift and induced drag of flapping wings and applies it to a hovering and forward-flying bumblebee and a mosquito. Two- and three-dimensional graphical representations of the state space are introduced and explored for engineered subsonic flyers, biological fliers, and sports balls.

Abstract The purpose of the present article is to develop a Finite Element Method (FEM) for steady potential flows over a range of bluff bodies like cylinders to streamlined profiles such as airfoils. In contrast to conventional panel methods, Laplace’s equation describing the potential flow is solved here for the velocity-potential function using the Galerkin method. A brief discussion on edge singularities in potential flows has also been presented using a half-cylinder case study. A novel method for implementing Kutta condition over airfoils to have lifting flow is explained. Compared with other Finite Difference Methods (FDM) and Finite Volume Methods (FVM), the present methodology has proven to be computationally faster for airfoils with both a finite angle trailing edge and cusped trailing edge. The results obtained have demonstrated excellent accuracy compared to analytical and panel methods.

Abstract At supersonic aircraft speeds, aerodynamically heated surfaces, e.g., nose, wing leading edges, are infrared (IR) signature sources from the tactically crucial frontal aspect. This study numerically predicts and then illustrates the minimization of IR contrast between the nose and background sky radiance by the emissivity optimization (εw,opt) technique, which has the least performance penalties. The IR contrast between the aircraft nose and its replaced background in 1.9-2.9 μm short-wave IR (SW-IR), 3-5 μm medium-wave IR (MW-IR), and 8-12 μm long-wave IR (LW-IR) bands are obtained. The IR contrast especially in LW-IR (i) increases with flight Mach number (M ∞) for a given flight altitude (H) and εw (ii) decreases with increasing H for a given M ∞ and εw. The εw,opt for a flight altitude of 5 km is found to decrease from 0.99 at M ∞ = 0.001 (low subsonic) in all three bands to 2 × 10−4 in MW-IR and 0.0213 in LW-IR bands at M ∞ = 3 (high supersonic).

Abstract New analytical structural stress solutions for a rigid inclusion in a finite square thin plate with clamping edges under opening loading conditions are developed. The new solutions are used to derive new analytical structural stress and stress intensity factor solutions for similar and dissimilar spot welds in cross-tension specimens. Three-dimensional finite element analyses are conducted to obtain the stress intensity factor solutions for similar spot welds and dissimilar magnesium/steel spot welds in cross-tension specimens of equal thickness with different ratios of half-specimen width-to-weld radius. A comparison of the analytical and computational solutions indicates that the analytical stress intensity factor solutions for similar spot welds in cross-tension specimens of equal thickness are accurate for large ratios of half-specimen width-to-weld radius.

Abstract The turboshaft engine performance is closely related to the helicopter’s design, and because of its location beneath the helicopter’s main rotor, it has unique features that distinguish it from other families of gas turbine engines. The impact of the engine suction and main rotor’s blow in different flight regimes and climatic conditions lead to variations in speed, pressure, and temperature at the inlet of the turboshaft engines, which, in turn, will affect the design of the engine cycle. Therefore, in this article, the equations governing the airflow for turboshaft engines are enhanced to incorporate these effects. The equations in this article are derived using aerodynamics, flight dynamics, helicopter, and turboshaft design to lend the inlet velocity of the engine. In order to validate the analytical outcomes of these equations, a computational fluid dynamics (CFD) analysis is carried out to evaluate the turbulent flow at the T700-GE turboshaft inlet.

Abstract The paper presents a complete description of the design and manufacturing of a Carbon Fiber/epoxy mold with an embedded Carbon Fiber resistor heater, and the mold performances in terms of its surface temperature distribution and thermal deformations resulting from the heating. The mold was designed for manufacturing aileron skins from Vacuum Bag Only prepreg cured at 135°C. The glass transition temperature of the used resin-hardener system was about 175°C. To ensure homogenous temperature of the mold working surface in the course of curing, the Carbon Fiber heater was embedded in a layer of a highly heat-conductive cristobalite/epoxy composite, forming the core of the mold shell. Because the cristobalite/epoxy composite displayed much higher thermal expansion than CF/epoxy did, thermal stresses could arise due to this discrepancy in the course of heating.

Abstract Cavitation erosion caused by high-frequency vibrating walls can appear in the cooling circuit of internal combustion engines along the liners. The vibrations caused by the mechanical forces acting on the crank drive can lead to temporary regions of low pressure in the coolant with local vapor formation, and vapor collapse close to the liner walls leads to erosion damage, which can strongly reduce the lifetime of the entire engine. The experimental investigation of this phenomenon is so time consuming and expensive, which it is usually not feasible during the design phase. Therefore, numerical tools for erosion damage prediction should be preferred. This study presents a numerical workflow for the prediction of cavitation erosion damages by coupling a three-dimensional (3D) Multi-Body-Dynamic (MBD) simulation tool with a 3D Computational Fluid Dynamics (CFD) solver.

Abstract The present study deals with the investigation on microstructural and mechanical properties of friction stir processed (FSPed) pure Aluminum (Al)-Graphene Nanoplatelets (GNPs) composites. Composite specimens such as castings were made by blending 0.5 wt.%, 1.0 wt.%, 1.5 wt.%, and 2.0 wt.% of GNPs in pure Al matrix using the ultrasonic-assisted stir casting technique (UASCT). Also for enhancement of mechanical properties via grain refinement the friction stir processing (FSP) has been employed, as well as mechanical properties like tensile strength and microhardness were evaluated. Moreover, the microstructural analysis were done using Scanning Electron Microscope (SEM), Field Emission Scanning Electron Microscope (FESEM), transmission electron microscopy (TEM), and X-Ray Diffraction (XRD) examination were also performed for inspecting the changes occurred during synthesis of the fabricated composites after FSP.

Abstract High-cycle fatigue (HCF) is one of the main concerns for spot-welded structures, and finite element (FE)-based simulations have critical importance for the life assessment and design optimization. The accuracy of spot weld modeling methodologies has a key role in achieving the development objectives. This article presents a comparative study for HCF simulations of different spot weld modeling methodologies and their comparison with the test data. In this regard, HCF analyses based on Findley’s multi-axial damage model are conducted with a commercial software. Direct equivalenced spot weld modeling with and without offset adjustment, rigid spot weld, and rigid beam (single) spot weld methods are analyzed for overlapped sheet metals under axial cyclic loading. Two specimens with different thicknesses, spot weld diameters, and number of nuggets are simulated under six cyclic load cases: 2000-4000 N, 1400-2800 N, 1800-3600 N, 200-8000 N, 100-8300 N, and 200-6800 N.

Abstract Ground vibration testing (GVT) is an important phase of the development, or the structural modification of an aircraft program. The modes of vibration and their associated parameters extracted from the GVT are used to modify the structural model of the aircraft to make more reliable dynamics predictions to satisfy certification authorities. Due to the high cost and the extensive preparations for such tests, a new method of vibration testing called taxi vibration testing (TVT) rooted in operational modal analysis (OMA) was recently proposed and investigated by the German Institute for Aerospace Research (DLR) as alternative to conventional GVT. In this investigation, a computational framework based on fully coupled flexible multibody dynamics for TVT is presented to further investigate the applicability of the TVT to flexible airframes. The time domain decomposition (TDD) method for OMA was used to postprocess the response of the airframe during a TVT.

Abstract The Naval Nose Landing Gear (NLG) structural assembly consists of components with complex structural geometry and critical functionalities. The landing gear components are subjected to high static and dynamic loads, so they must be appropriately designed, dimensioned, and made by materials with mechanical characteristics that meet high strength, stiffness, and less weight requirements. This article contributes to the shape, size, and material optimization for the NLG of a supersonic naval aircraft for the estimated static loads. The estimated modal frequency values of the NLG assembly using Finite Element Analysis (FEA) software were compared with available Ground Vibration Test data of an aircraft to literally prove the accuracy and suitability of finite element (FE) model that can be used for any further analysis.

Abstract Powder metallurgy is a widely used manufacturing methodology in the gearbox industry. Noise and vibration is a common cause for concern in the gearbox industry due to the continuous contact between gear teeth at high rotational frequencies. Despite this, limited research has been performed investigating the modal properties of powder metal products. This work investigates the damping ratios of a copper-infiltrated steel powder metal ring and a hot-rolled steel ring both experimentally and computationally. Negligible difference was observed between the damping ratios of the powder metal and hot-rolled steel rings. Two proportional damping models were investigated to predict the damping ratios of the powder metal ring. It was found that the Caughey damping model was the most accurate, generating damping ratios within 2.36% for a frequency bandwidth of up to 4000 Hz.

Abstract The simple oleo pneumatic (shock absorber) model was developed using the available computational fluid dynamics (CFD) program to understand how various parameters influence the performance of the undercarriage shock absorber. The study is divided into two parts: first part is focused on the influence of orifice geometry and the second part of the study is focused on the other parameters including chamber geometry. Both the studies are carried out using design of experiments (DOE) for the same output characteristics (response). In this study, the impacts on the flow behavior due to the orifice shapes are also studied. The results and the other outcomes are shown in the form of DOE parameters such as main effect plots and interaction plots.

Abstract Cast magnesium (Mg) door inner panels can provide a good combination of weight, functional, manufacturing, and economical requirements. However, several challenges exist including casting technology for thin-wall part design, multi-material incompatibility, and relatively low strength versus steel. A project was supported by the US Department of Energy to design and develop a lightweight frame-under-glass door having a thin-wall, full die-cast, Mg inner panel. This development project is the first of its kind within North America. The 2.0 mm Mg design, through casting process enablers, has met or exceeded all stiffness and side-impact requirements, with significant mass reduction and part consolidation. In addition, a corrosion mitigation strategy has been established using industry-accepted galvanic isolation methods and coating technologies. The performance of the Mg design has been demonstrated through component and vehicle tests.

Abstract An investigation was carried out to evaluate the potential aerodynamic benefit of spanwise jet injection from the wingtips. Aircraft currently use conventional solid winglets that add extra structural weight. However, results reveal that fluidic on-demand winglets effectively reduce drag for low-speed flight regimes without the addition of any extra weight. These utilize the spanwise airflow from the wingtips using hydraulic actuators to create jets that negate tip vortices. This research aims to investigate the fluidic winglet jet characteristics on the aerodynamic performance of the wing. Results indicate that the spanwise blowing shifts the core of the wingtip vortices upward and outward from the wing surface. In a particular range of jet velocity ratio, the magnitude of vorticity near the wingtips tends to reduce, resulting in a reduction of induced drag.

Abstract ERRATUM

Abstract Combining ball milling with stir casting in the synthesis of nanocomposites is found effective in increasing the strength and ductility of the nanocomposites. In the first step, the nanoparticles used as reinforcement are generated by milling a mixture of aluminum (Al) and manganese dioxide (MnO2) powders. A mixture of Al and MnO2 powders are mixed in the ratio of 1:2.4 by weight and milled at 300 rpm in a high-energy planetary ball mill for different durations of 120 min, 240 min, and 360 min to generate nano-sized alumina (Al2O3) particles. It is supposed that the powders have two different roles during milling, firstly, to generate nano-sized Al2O3 by oxidation at the high-energy impact points due to collision between Al and MnO2 particles, and secondly, to keep nano-sized Al2O3 particles physically separate by the presence of coarser particles.