bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced diversity and aflatoxigenicity in interspecific hybrids ofAspergillus flavusandAspergillus parasiticus
Authors: Olarte Rodrigo A. , Worthington Carolyn J. , Horn Bruce W. , Moore Geromy G. , Singh Rakhi , Monacell James T. , Dorner Joe W. , Stone Eric A. , Xie De‐Yu , Carbone Ignazio
Published: March 2015

Aspergillus flavusandA. parasiticusare the two most important aflatoxin‐producing fungi responsible for the contamination of agricultural commodities worldwide. Both species are heterothallic and undergo sexual reproduction in laboratory crosses. Here we examine the possibility of interspecific matings betweenA. flavusandA. parasiticus. These species can be distinguished morphologically and genetically, as well as by their mycotoxin profiles.Aspergillus flavusproduces both B aflatoxins and cyclopiazonic acid (CPA), B aflatoxins orCPAalone, or neither mycotoxin;Aspergillus parasiticusproduces B and G aflatoxins or the aflatoxin precursorO‐methylsterigmatocystin, but notCPA. Only four of forty‐five attempted interspecific crosses between opposite mating types ofA. flavusandA. parasiticuswere fertile and produced viable ascospores. Single ascospore strains from each cross were shown to be recombinant hybrids using multilocus genotyping and array comparative genome hybridization. Conidia of parents and their hybrid progeny were haploid and predominantly monokaryons and dikaryons based on flow cytometry. Multilocus phylogenetic inference showed that experimental hybrid progeny were grouped with naturally occurringA. flavusL strain andA. parasiticus. Higher total aflatoxin concentrations in some F1 progeny strains compared to midpoint parent aflatoxin levels indicate synergism in aflatoxin production; moreover, three progeny strains synthesized G aflatoxins that were not produced by the parents, and there was evidence of allopolyploidization in one strain. These results suggest that hybridization is an important diversifying force resulting in the genesis of novel toxin profiles in these agriculturally important fungi.
Configuration E-7 Supersonic Fighter/Attack Technology Program
Authors: Jenista John E. , Bodden David S.
Published: March 2015

The program covering the design and early technology development of Configuration E-7, a supersonic STOVL Fighter/Attack aircraft is described. This aircraft uses the ejector principle to augment engine fan air for vertical lift. The initial design objectives selected in 1980 are listed and discussed. Some design considerations applicable to the propulsion concept and the chosen configuration are mentioned. The test program accomplished thus far, including wind tunnel models plus other test articles and activities is outlined. The program has proceeded without major technological obstacles and a full-scale engine-powered model will soon be ready for test.
Unburned Hydrocarbon, Volatile Organic Compound, and Aldehyde Emissions From General Electric Heavy-Duty Gas Turbines
Authors: Pavri Roointon E. , Symonds Richard A.
Published: March 2015

Field data clearly show that the emissions of UHC, VOC, (sometimes also called Reactive Organic Gases), and Aldehydes from GE heavy-duty gas turbines are very low. At loads exceeding 75% of base, these emissions are less than 2 ppm. In fact, stack emissions are often less than background concentration. Proper methods of measurement and quality assurance are necessary to detect and measure such low values. Allowance for background hydrocarbons should be made when guaranteeing UHC/VOC.
Gas Turbine Powered Blue Riband Winner
Authors: Allen Robert , Lauriat T. B.
Published: March 2015

The high speed yacht “Gentry Eagle” has set a new record for Atlantic Ocean crossing plus two other speed records. The British built, United States owner 110 ft. craft is powered by two diesels and a centerline 4,000 hp marine gas turbine.

The paper will describe all the power plants and the propulsion system for each. Gas turbine mounting, control, inlet and exhaust treatment, and operating scenario will be covered. Craft details will be included.

History of the vessel including performance and speed run details will be noted.
An Investigation of Convective Heat Transfer in a Rotating Coolant Channel
Authors: Medwell J. O. , Morris W. D. , Xia J. Y. , Taylor C.
Published: March 2015

A numerical method is presented for the determination of heat transfer rates in a cylindrical cooling duct within turbine blades which rotate about an axis orthogonal to its own axis of symmetry.

The equations of motion and energy are solved in conjunction with the k-ε model of turbulence using the finite element method. The predicted results are compared with experimental data and it is clearly demonstrated that conduction in the solid boundary must be taken into account if satisfactory agreement is to be achieved.

Excluding these effects can lead to an over-estimation of the maximum wall temperature by approximately 50%.
Water Treatment and Moisture Separation in Steam-Injected Gas Turbines
Authors: Kolp D. A. , Gagnon S. R. , Rosenbluth M. J.
Published: March 2015

Steam injection has been employed in gas turbines for over twenty years. Initially the emphasis was on injection for small amounts of power augmentation and NOx reduction in the turbine exhaust gas. More recently it has been used for massive power increases (more than 50% on some gas turbines) and efficiency improvements (more than 20%). Equipment selection, operation and economics are essential ingredients in producing the high-purity steam required in a steam-injected gas turbine cycle.

The most common means of producing steam for the steam-injection cycle is by means of a waste heat boiler operating in the turbine exhaust gas stream. Steam generated in this boiler may then be injected into the compressor discharge, combustor or turbine sections of the gas turbine to improve performance.

Manufacturers require extremely high purity steam for injection into their gas turbines; less than 30 parts per billion (PPB) of some contaminants is not an unusual requirement. If this steam quality is not obtained, serious damage can occur, particularly in the turbine hot section. To meet these stringent steam quality requirements without excessive amounts of boiler blowdown, it is necessary to provide highly demineralized makeup water to the boiler, i.e. less than 1 PPM TDS (Total Dissolved Solids). Low silica concentrations are particularly important since silica can vaporize at higher boiler pressures, pass through the moisture separators and deposit on turbine components. The selection of equipment required to produce high quality makeup water from various grades of raw water is critical to the successful operation of the steam injection plant. Because the steam cannot be recovered effectively, it is necessary to install a large water treatment system to provide the quantities of makeup required for steam injection. Equally critical to the cycle is the type of drum moisture separation used in achieving manufacturers’ recommended steam quality.

Just as the steam injection cycle has a dramatic impact on the economics of a gas turbine power plant, so too do the operation and selection of steam purification equipment influence the overall economics of the steam injection cycle.
Effects of Operating Conditions on Plastic Strain and Temperature in Ultrasonic Vibration Process
Authors: Yi Dalong , Zhang Hui , Zheng Lili
Published: March 2015

Ultrasonic vibration is widely used in rapid prototyping process which creates solid joint from work pieces using high frequency and low amplitude. The quality of the joint is strongly related to operating parameters used, but the key operating parameters and their impacts on the quality of the joint are not well understood. A 3-D thermal-mechanical finite element model is developed to investigate the effects of control parameters of ultrasonic vibration (vibration amplitude, vibration cycle, applied force, preheating temperature) on the joint quality. Simulation results show that with the increase of each parameter, such as applied force, vibration amplitude, vibration cycle and preheating temperature, both average plastic deformation and joint temperature are increased. This temperature-strain map can help us find the optimum operating conditions in manufacturing.
Design of Double Cone Twist Drill Geometry to Improve the Holes Quality While Drilling in Multi-Stack Made of CFRP/Al
Authors: Zitoune Redouane , Bouacif Sofiane Alma , Vijayan Krishnaraj , Francis Collombet
Published: March 2015

In this paper, experimental and numerical studies on drilling of multi-material made of CFRP laminate sandwiched with aluminum part have been carried out. These tests have been conducted using carbide drills (K20) to study the influence of spindle speed, feed rate and lip length of the double cone drill on cutting forces and holes quality. From the experimental study it was found that the double cone drills used for the experimental analysis encountered less thrust force compared to the standard twist drill. In addition the quality of the holes after drilling was evaluated, and found that no delamination (entry and exit of the hole of the composite part) even at higher feed rate (> to 0.1 mm/rev). By numerical modeling, it was noticed that, after machining with standard twist drill at higher feed rates, the thrust force generated induces a small opening at the CFRP/Al interface.
High Performance Zinc Oxide Thin Film Transistors Through Improved Material Processing and Device Design
Authors: Adl Ahmad Hossein , Farsinezhad Samira , Ma Alex , Barlage Douglas W. , Shankar Karthik
Published: March 2015

Solution processing (SP) is a cheap, simple and high-throughput method for the fabrication of ZnO thin film transistors (TFTs). Lack of enhancement mode operation, poor crystallinity, traps, and poor control of the carrier concentration are some of the disadvantages of this method. The high intrinsic electron concentration of SP-ZnO makes saturation of TFTs non-trivial. We report on Schottky barrier thin film transistors (SB-TFT). By biasing the source Schottky contact in reverse bias, a depletion region is formed around the source contact hence depleting the region from the free charge carriers which produces the saturation of the device. The effect of the Schottky contact is illustrated by comparing the operation of SB-TFTs with that of conventional TFTs.
Thermo-Structural and Thermo-Fluid Dynamics Analyses Supporting the Design of the Cooling System of a Methane Liquid Rocket Engine
Authors: Ferraiuolo M. , Ricci D. , Battista F. , Roncioni P. , Salvatore V.
Published: March 2015

The HYPROB Program, developed by the Italian Aerospace Research Centre, has the aim to increase the system design and manufacturing capabilities on liquid oxygen-methane rocket engines. It foresees the designing, manufacturing and testing of a ground engine demonstrator of three tons thrust. The demonstrator baseline concept is featured by 18 injectors and it is regeneratively cooled by using liquid methane. In particular, the cooling system is made by a constant number of axial channels and the counter-flow architecture has been chosen; methane enters the channels in the nozzle region in supercritical liquid condition, is heated by the combustion gases along the cooling jacket and then injected into the combustion chamber as a supercritical gas by means of the injection head.

The goal of this paper is to describe the thermo-structural and the thermo-fluid dynamic analyses that have been performed in order to support the design activities aiming at identifying the optimal configuration of the cooling jacket in terms of number of channels, rib height and width. In fact, a fully 3-D model, regarding a single channel, heated by the design input heat flux has been considered in order to perform CFD simulations aiming at describing the thermo-fluid dynamic behavior of methane. The results in terms of convective heat transfer coefficients have been taken into account as inputs for the thermo-structural simulations on the most critical sections of the cooling jacket. The thermo-structural activity has been conducted on the demonstrator by means of a Finite Element Method code taking into account the visco-plastic behavior of the adopted materials. In particular, transient thermal analyses and static structural analyses have been performed using ANSYS code on a 2-D model. These analyses have demonstrated that the cooling jacket can withstand the design goal of 5 thermo-mechanical cycles with a safety factor equal to 4 considering a firing time equal to 30 seconds.
An Efficient Analytical Model for the Structural Analysis of Wrapping Machine Rotating Rings
Authors: Croccolo D. , De Agostinis M. , Fini S. , Olmi G.
Published: March 2015

Wrapping machines usually consist of a two- or a four-column frame, supporting a huge rotating ring, connected to a pre-stretch unit with film coil carrier. Stiffness is a key point of packaging machines, since it is strictly related to the accuracy of the wrapping task. It depends on the stiffness of the frame, which can be achieved by the four-column architecture, and on the ring constraint system. As a consequence, the ring structures are usually highly statically indeterminate. Nowadays, there is an increasing demand for higher rotational speeds and more reduced operation times. Therefore, an accurate structural analysis of the ring, considering its actual loading and constraints is more and more important. The structural analysis of the rotating ring is treated by many references, however, such a hyperstatic constraining makes this problem highly complicated. The goal of this paper consists in the development of a general and original analytical model, useful for the structural analysis of rotating rings. The results are collected in a user-friendly way in terms of normalized internal loads, so that they can be of a great help even for not expert users. This model has been experimentally validated and easily applied to case studies and optimization tasks.
Nanoscale Thermal Transport in Plasmonic Nanofocusing Structure With Strong Nonlocality
Authors: Chen Chen , Du Zhidong , Pan Liang
Published: March 2015

Nanoscale optical energy concentration and focusing is crucial for many high-throughput nanomanufacturing applications, such as material processing, imaging and lithography. The use of surface plasmons has resulted in the rapid development of nanofocusing devices and techniques at spatial confinements as good as a few nanometers associated with strong nonlocal plasmonic response. However, operations of these plasmonic nanofocusing structures usually require extremely high optical energy density at nanoscale, which leads to intense structure heating and causes unreliable device functions and short device lifetimes. In many plasmonic applications, optical heating has become a very important issue, which has not been investigated intensively yet. In these structures, the ballistic transport and interface scattering of the energy carriers both become significant because the characteristic lengths of the devices are comparable to or smaller than the mean free paths of the carriers. A comprehensive model is desired to understand the heat generation and transport inside the plasmonic nanofocusing structures.

This work studied the electromagnetic and optothermal responses of plasmonic nanofocusing nanostructures. At the nanometer length scale, the local optical response and diffusive thermal model are no longer sufficient to describe the device optothermal response because of the strong interactions between energy carriers and the ballistic nature of carriers. Here, we used the hydrodynamic Drude model to consider the nonlocality of plasmonic response and calculate the heat generation inside the metallic nanostructures. Starting from Boltzmann transport equation, we derived the energy transport equations for both electron and phonon systems under the relaxation-time approximations. The obtained multi-carrier ballistic-diffusive model was used to study the non-equilibrium heat transports inside the structures. We assume that the ballistic electrons originate from boundaries and the electron-photon couplings inside the structure, experiencing out-scattering only in the material. The optically-generated “hot” electrons are considered as ballistic and are treated separately from the “ordinary” electrons which are in local thermal equilibrium and have significantly lower energies. Meanwhile, the electron-phonon couplings are considered under the non-equilibrium conditions between the electron and phonon systems. Using our model, we further investigated the transient optothermal responses of a one-dimensional (1D) plasmonic nanofocusing structure. In comparison to the diffusive transport description, our multi-carrier ballistic-diffusive model can more accurately describe the optothermal responses of the plasmonic nanofocusing structures which are crucial for predicting the performance and the lifetime of the plasmonic nanofocusing devices.
Load Distribution of Ball Screw With Consideration of Contact Angle Variation and Geometry Errors
Authors: Xu Sheng , Yao Zhenqiang , Sun Yaofei , Shen Hong
Published: March 2015

Hundreds of mirror segments are needed to realize the laser fusion system and the next generation ground based extra-large telescopes. In order to manufacture the mirror segments, the ultra-precise optics grinding machine is essential equipment. As the most widely used motion transfer device in these machines, the ball screw mechanism need predetermine its positional accuracy. And the positional accuracy is based on load distribution of ball screw. This will be discussed in the article. Based on existing analytical models, an improved model is developed to accurately predict load distribution of ball screw. In this model, variation of contact angle is considered. And a simple approach considering of the influence of the geometry errors on the load distribution is developed. The results of this model demonstrate the load distribution of ball screw is not average and load of every ball falls from the position near the load to further. Downward trend is more marked when introducing the variation of contact angle into the model. Besides, the effect of geometry errors on the load distribution is not as remarkable as existing models. Based on the model, the larger ratio of helical pitch to screw diameter is, the worse the nonuniformity of load distribution is. This will impair the stiffness of ball screw and its positional accuracy. The calculated results are significant to ball screw design.
Probabilistic Assessment of Turbine Disk Considering Geometry Distribution Based on Surrogate Models
Authors: Fan Jiang , Wang Hao
Published: March 2015

For rotating critical parts of aero engines, such as turbine disks, it is essential to perform reliable life predictions. Probabilistic methods are ideal to investigate these life predictions. Beside other system parameters, the distribution of geometrical parameters has a strong effect on the system behavior. However, as there are always so many geometry parameters, it always takes lots of time to complete such a probabilistic analysis considering geometry.

Within this paper, a probabilistic method based on two surrogate models is proposed and applied to an analysis of a turbine disk. In order to save the computation time as well as to get accurate results, this process is divided into two cycles. The purpose of the first cycle is to filter the parameters which have little influence on the life of the disk. In this cycle, DOE method is used and a normal response surface is created as a surrogate model to calculate the sensitivities of all the input parameters. With the sensitivities some key parameters can be selected as the inputs for the second cycle. In the second cycle DACE method is used and a more accurate Kriging model is created as the surrogate model. By conducting MCS on the calculated Kriging model, the reliability of the turbine disk can be get. In this way a huge number of computations can be avoided, thus much time can be saved and the computational efficiency can be improved.
Lateral Navigation Optimization Considering Winds and Temperatures for Fixed Altitude Cruise Using Dijsktra’s Algorithm
Authors: Murrieta-Mendoza Alejandro , Botez Ruxandra
Published: March 2015

Optimizing the flight trajectory is a goal that will minimize fuel consumption and time related costs. Lateral Navigation (LNAV) has been investigated as part of identifying optimal trajectories. Winds and temperature have an important influence in the cost of a flight. Tail winds and low temperatures are desired, as both reduce flight costs. Implementing algorithms to locate where these favorable conditions exist close to the defined trajectory of a given flight will help to achieve optimal flight trajectories. These algorithms are to be implemented in an FMS using an aircraft model which is normally given in the form of a Performance Database (PDB). The approach given in this paper uses Dijsktra’s algorithm. This method is part of the graph-search techniques. The search area is defined by discretizing the cruise trajectory and defining adjacent waypoints, forming a grid where the possible trajectories are created. The algorithm requires the aircraft’s gross weight at the top of climb (TOC), the location of the top of descent (TOD), and the desired cruise speed and altitude. The related costs are calculated using the PDB’s model for two different commercial aircraft at a constant altitude and at a constant indicated mach. To minimize the costs, the algorithm considers the fuel burned, the flight time and the cost index (CI). The temperature and winds in the trajectory are obtained from the Canadian weather forecast (Environment Canada). Wind influence is taken into account by adding it to the ground speed, based on its direction regarding the aircraft’s trajectory heading. The effect of temperature is considered in the PDB. Generated trajectories are compared against the geodesic (or great circle) route.
Three Dimensional Modeling of Unfired Ceramics During Lamination
Authors: Wimmer Stephanie A. , Pan Ming-Jen , DeGiorgi Virginia G.
Published: March 2015

A finished ceramic component with complex geometries such as micro-channels requires a high degree of dimensional accuracy. This accuracy depends upon precise control of the unfired ceramic body before sintering. One method for creating precise micro-channel geometries is the fugitive phase approach. In this approach, a sacrificial material, the fugitive phase, is used to form channels or voids in the unfired ceramic body. The fugitive phase is removed or sacrificed during the subsequent sintering. For this paper, the authors examine the lamination step of the fugitive phase approach computationally. The lamination step is where the unfired ceramic and fugitive phase pieces are layered and pressed together to remove voids before sintering. The compression of the unfired ceramic during pressing causes pressure gradients, viscoelastic deformation, displacement of the fugitive phase pieces, and rebounding. Three dimensional modeling is used to capture out of plane movement or bending of the long fugitive phase pieces that are used to form long micro-channels. For this research, the unfired ceramic phase consists of tape cast mullite and the fugitive phase is paper. This work primarily examines viscoelastic material models of the unfired ceramic phase for a range of temperatures. The filling of voids, movement of the fugitive phases, pressure gradients, and the rebounding that occurs when the unfired ceramic body is removed from the die press are also noted. The information obtained from computational simulations is used to help direct concurrent experimental investigations.
Prediction of Hardness Profile of 4340 Steel Plate Heat Treated by Laser Using 3D Model and Experimental Validation
Authors: Billaud G. , Barka N. , El Ouafi A. , Chebak A. , Brousseau J.
Published: March 2015

The paper presents a study of hardness profile of 4340 steel plate heat treated by scanning laser technique using 3D model. The proposed approach is carried out in three distinguished steps. First, a commercial software 3D model was developed using an adequate formulation and taking into account the nonlinear behaviour of the material. Second, the hardness curve is approximated from the temperature distribution using metallurgical assumptions related to the kinetic transformation and the temperature-time transformation diagram. Then, the case depth is analyzed quantitatively versus the beam power density and scanning speed. Finally, the developed approach is validated using experimental tests. The gap between simulation and experience results is determined. The obtained results allow predicting of the hardness profile with a fairly good precision.
Identifying Relative Importance of Input Parameter(s) for Developing Predictive Model for Laser Cladding Process
Authors: Aggarwal Kush , Urbanic Ruth Jill , Aggarwal Luv , Saqib Syed
Published: March 2015

Laser cladding (LC) is a multi-variable coating process which consists of process multiple inputs and associated bead geometry outputs. Fabrication of a desired clad bead geometry configuration is expensive, as it involves investment of specialized raw materials, specialty equipment, and time resources. Hence, it is vital to determine factors/inputs that affect the overall physical bead geometry parameters (response variables), and the nature of the responses. The objective of this research is to identify the extent of the contribution of each factor and impact of their interactions on the output which is essential in developing effective predictive models. Analysis of variance (ANOVA) and sensitivity analysis methodologies are studied in this research to determine the most significant process factors that relate to the shape parameters for a typical laser cladding production process scenario. A set of statistical based summaries for all response variables are presented. This includes contour and surface plots to illustrate the difference in effects for a response variable by a single process parameter as compared to two or more interacting process parameters. Finally, an optimization solver toolbox is applied to determine single and multiple objective optimization results that can be obtained for various desired bead geometries.
Process Analysis of Expert and Non-Expert Engineer in Quartz Glass
Authors: Suda Masamichi , Qiu Peng , Takahashi Toru , Hattori Akio , Yang Yuqiu , Goto Akihiko , Hamada Hiroyuki
Published: March 2015

Quartz glass is a special glass material known as “King of Glass”. The silicon purity of the quartz glass is very high, therefore it is excellent in heat resistance, chemical resistance and optical transparency as compared to other glasses, such as borosilicate glass.

At present, it is used in the production field of leading-edge. Now researches are carried out to develop it as key components of special manufacturing equipment, scientific instruments and analysis equipment that require high-precision, high purity, the high light transmittance. However, due to its high heat resistance, it is difficult to be processed into various shapes. As a result, manufactured quarts glass products, generally, might be different even in one batch. To respond to such products for precision instruments, it is preferable to select the heat molding process by flame called “fire-process” in many cases. “fire-process” is the process of forming a softening point of heated quartz glass material by a mixed combustion flame of hydrogen and oxygen. Therefore, a technique for forming a glass material softened by heating is required, and now it is done by human hand processing of engineers. While skilled human technique of long time experience is required in order to produce high precision and an efficient products. Therefore digitizing and analysis of the work of expert engineers with high level of hand skill is needed to increase the processing technology of the engineers less skilled and take advantage in the manufacture of high-precision products. In this study, the differences in the working process between engineers with different years of experience during the “fire-process” of quartz glass material were analyzed. Fire-process is of heating joint glass cylinders during rotating using a dedicated glass lathe machine. The working behaviors of three operators were recorded by videos during “fire-process”. And the thickness of jointed part of final products was measured by ultrasonic equipment to evaluate the quality of the jointed situation. It is found that these differences in the process of heating joint of glass cylinder have effects on the accuracy of finial production and the manufacturing efficiency.
Towards Automated Design of Fastening Systems for Accelerated Product Development
Authors: Friedrich C. , Hubbertz H. , Roser H. , Walker P.
Published: March 2015

Although considered a well-established machine element, screw fastening systems are required to fulfill ever increasing demands for performance, reliability, economy, and sustainability. Yet there are limitations to the capabilities of existing design procedures which often neglect a comprehensive analysis of both soft and hard design parameters over the entire system life cycle.

This paper presents a holistic approach towards automated design of screw joints, going beyond established methods by incorporating soft (intangible) design parameters additionally. Based on the vectorial design method developed by Friedrich, a multi-objective optimization process is used to tradeoff various, often conflicting design parameters from the vectorial design approach (such as screw diameter, assembly method, preload loss, material strength, etc.) to derive an optimum solution with a high level of confidence.

For this, a complex network of strategy parameters and safety factors is used (optimization parameters). It is referred to geometry, material, contact, assembly and production for boundary conditions. A definite solution for the model of the fastening system must incorporate analytical functions, numerical relationships and correlation with technical and non-technical aspects (including cost and environmental impact).

This multi-objective approach entails inherent flexibility enabling designers to set application specific design priorities as a key part prior to defining an optimized solution. Overall, this gives the capability for an automated design process, which can be performed with computational engineering. A major benefit from this is saving product development time and therefore cost as well as evaluating influence-intensity of design parameters (rating of influencing values).

An example of a wheel bolt connection is provided to demonstrate this approach referring to a well-known application. From this it is outlined that conflicting safety factors lead to an optimum which is determined by the level of reliability or performance. The presented process offers considerable benefits in reduced development time particularly for complex, customized fastening systems, reducing unnecessary design iterations and empirical testing. The following process is intended to give a modern structure for fastener selection procedures linked with computational engineering capabilities and design experience.
Aerolelastic Analysis of a Thin-Walled Composite Aircraft Wing With an External Store Subjected to a Follower Force
Authors: Aksongur Alev Kacar , Eken Seher , Kaya Metin O.
Published: March 2015

This study reports dynamic aeroelastic analyses of an aircraft wing with an attached mass subjected a lateral follower force in an incompressible flow. A swept thin-walled composite beam with a biconvex cross-section is used as the structural model that incorporates a number of non-classical effects such as material anisotropy, transverse shear deformation and warping restraint. A symmetric lay-up configuration i.e. circumferentially asymmetric stiffness (CAS) is further adapted to this model to generate the coupled motion of flapwise bending-torsion-transverse shear. For this beam model, the unsteady aerodynamic loads are expressed using Wagners function in the time-domain as well as using Theodorsen function in the frequency-domain. The flutter speeds are evaluated for several ply angles and the effects of follower force, transverse shear, fiber-orientation and sweep angle on the aeroelastic instabilities are further discussed.
Surface Tribology Study Resulting by Diamond-Like Carbon Coating
Authors: Mordo Sergio , Popravko Valery , Barari Ahmad
Published: March 2015

Companies that coat their products with DLC often have strict surface roughness and goals. This research investigates the surface roughness properties of uncoated and DLC coated specimens in an effort to know what uncoated surface roughness is needed to obtain a certain DLC coated surface roughness. Therefore, a model describing the relationship between uncoated and DLC coated surface roughness is needed. If this relationship can be estimated, the cost of surface finishing can be minimized by avoiding any unnecessary processes. A total of 7 specimens were tested before and after coating process with a non-contact surface roughness measurement microscope. Mathematical relationships are found between the DLC coated surface roughness and uncoated surface roughness. An experimental methodology was described for applying the findings to other coating methods and materials as the mathematical relationships found in this study are specific to the coating process and materials used.
Development of an Aeroelastic Wing Model With Piezoelectric Elements for Gust Load Alleviation and Energy Harvesting
Authors: Bruni Claudia , Cestino Enrico , Frulla Giacomo , Marzocca Pier
Published: March 2015

The lifting surfaces of next generation of flying vehicle exhibits enhanced flexibility, particularly for high aspect-ratio solutions needed for high-altitude long endurance aircrafts and for 24/7 operations. Often the wing of these vehicles is designed as slender body with an aeroelastic behavior distinctive of cantilever beam. Based on this typical assumption the governing equations of a thin-walled beam modified to account for surface mount piezoelectric elements and subjected to deterministic external gust loads have been derived and its dynamic behavior examined. This paper assesses the effectiveness of piezoelectric elements to carry out load alleviation function over the slender structure invested by atmospheric disturbances along with the evaluation of the amount of the power density harvested via a suitable electric circuit connected to the piezoelectric elements.
Additive Manufacturing of Glass
Authors: Luo Junjie , Pan Heng , Kinzel Edward C.
Published: March 2015

Additive manufacturing has shown potential for manufacturing parts out of metals, plastics and even ceramics. This paper reports on Selective Laser Melting (SLM) for depositing glass which has significantly different material properties from metals, ceramics or polymers. A CO2 laser is used to locally melt portions of a powder bed to explore the effects of process parameters on stationary particle formation as well as continuous line quality. Numerical modeling is also applied to gain insight into the physical process. The experimental and numerical results indicate that the absorptivity of the glass powder is nearly constant with respect to the processing parameters. Finally we show that higher quality parts can be created using a wire-fed instead of powder-bed process. Industrially, the additive manufacturing of glass is potentially relevant for gradient index optics, systems with embedded optics and applications where glass is used to form a hermetic seal.
Dynamics of 3D Micropolar Gyroelastic Beams
Authors: Hassanpour Soroosh , Heppler G. R.
Published: March 2015

This paper is devoted to the dynamic modeling of micropolar gyroelastic beams and explores some of the modeling and analysis issues related to them. The simplified micropolar beam torsion and bending theories are used to derive the governing dynamic equations of micropolar gyroelastic beams from Hamilton’s principle. Then these equations are solved numerically by utilizing the finite element method and are used to study the spectral and modal behaviour of micropolar gyroelastic beams.
Evaluation of Electron Beam Welded AISI 415 Stainless Steel
Authors: Sarafan Sheida , Wanjara Priti , Champliaud Henri , Thibault Denis , Mathieu Louis
Published: March 2015

Sustainable manufacturing for assembly of turbines used in hydro power generation systems is driving the development of advanced technologies targeted to reduce life-cycle costs whilst assuring high performance over the prolonged product life-span. The turbine runner, a critical component in hydro power generation systems, requires weld assembly between the crown, band and blade sub-components. With due consideration of the thick-gauge sections involved, design and fabrication of a turbine runner that would integrate a high energy density technology for assembly, such as vacuum electron beam welding (EBW), has marked potential to achieve deep penetration with a low heat input, thereby rendering a weldment with narrow heat-affected zones (HAZ) and low distortion. In this study, the weldability of thick-gauge section AISI 415 martensitic stainless steels that are widely utilized in hydro turbine manufacturing was investigated by EBW. Particularly, bead-on-plate (BOP) welding of 88 mm-thick AISI 415 plate was carried out using a 42 kW high vacuum EBW system. The characteristics of the weldments, such as fusion zone (FZ) and HAZ microstructures and hardness were evaluated. The microstructural constituents across the weldment for process conditions that rendered near-complete penetration were studied and related to the microhardness evolution.
Stress Optimization of TBC System Based on Parametric Study of Aluminum Depletion and TGO Growth
Authors: Lim J. G. , Koo J. M. , Seok C. S. , Kim M. K.
Published: March 2015

Thermal Barrier Coating (TBC) system has been increasingly applied to gas turbine engine because of its outstanding ability to effectively protect substrate materials against impinging hot gas. However, the durability issue has still existed due to the growth of oxidation layer called thermal growth oxidation (TGO) and depletion of aluminum. Therefore, more detailed investigation is required to understand the effects of these two factors on the durability of TBC. In this study, a finite element (FE) model was developed to calculate the stress state near TGO interfaces by considering both the morphology of TGO and aluminum depletion effect. For acquiring the mechanical properties at the depletion area of bond coating layer, indentation tests were carried out, particularly, to the TBC specimens isothermally exposed at 1000 degree Celsius for 100h. Based on the proposed FE model with specific parameters obtained from experiments, parametric studies were performed in a variety of conditions of mechanical properties and TGO thickness. Simulation results clearly showed the influence of aluminum depletion and TGO growth on the durability of TBC system. Finally, optimal design criteria can be suggested to minimize the stress of TBC system.
Asymptotically Compatible Schemes for Peridynamics Based on Numerical Quadratures
Authors: Du Qiang , Tian Xiaochuan
Published: March 2015

We present some studies of numerical schemes for nonlocal peridynamic and nonlocal diffusion models. We describe asymptotically compatible (AC) schemes recently developed for robust discretizations of nonlocal models. The AC schemes for peridynamic models provide convergent approximations to nonlocal models associated with fixed horizon parameter as well as their limiting local models. We illustrate what quadrature based discretizations can be AC schemes and what may fail to be AC.
Using the DLR-F6 Aircraft Model for the Evaluation of the Academic CFD Code “Galatea”
Authors: Lygidakis Georgios N. , Nikolos Ioannis K.
Published: March 2015

Nowadays, the research in the aerospace scientific field relies strongly on CFD (Computational Fluid Dynamics) algorithms, avoiding (initially at least) a large fraction of the extremely time and money consuming experiments in wind tunnels. In this paper such a recently developed academic CFD code, named Galatea, is presented in brief and validated against a benchmark test case. The prediction of compressible fluid flows is succeeded by the relaxation of the Reynolds Averaged Navier-Stokes (RANS) equations, along with appropriate turbulence models (k-ε, k-ω and SST), employed on three-dimensional unstructured hybrid grids, composed of prismatic, pyramidical and tetrahedral elements. For the discretization of the computational field a node-centered finite-volume method is implemented, while for improved computational performance Galatea incorporates an agglomeration multigrid methodology and a suitable parallelization strategy. The proposed algorithm is evaluated against the Wing-Body (WB) and the Wing-Body-Nacelles-Pylons (WBNP) DLR-F6 aircraft configurations, demonstrating its capability for a good performance in terms of accuracy and geometric flexibility.
Mechanical Properties of Out-of-Autoclave Non-Crimp Fabric Epoxy Composites for Manufacturing Plant Elevations
Authors: Soltani Seyed A. , Le Gena , Asmatulu Ramazan
Published: March 2015

Mechanical properties of a commercial out-of-autoclave non-crimp fabric epoxy prepreg (AR2527 NCF) composite were investigated in detail for the manufacturing plant elevations. To simulate the effects of elevation, the vacuum pump used for pulling vacuum from the laminate during debulking and curing was adjusted to provide two different vacuum pressures: 1) 96 kPa corresponding to 450 m elevation in Wichita KS, and 2) 84 kPa corresponding to 1550 m elevation in Denver CO. One laminate for each vacuum pressure was cured in an oven using manufacturer’s recommended cure cycle and subsequently, the laminates were machined into appropriate mechanical test coupons tested at room temperature. It was observed that the average short beam shear, combined loading compression, and flexural strength of the prepreg dropped 5%, 9%, and 12% as a result of 1100 m increase in the elevation. It was also observed that the two laminates had similar porosity (∼4%). The decrease in mechanical properties of the prepreg was attributed to the increase in resin content of the laminate.
Peridynamic Beams and Plates: A Non-Ordinary State-Based Model
Authors: O’Grady James , Foster John T.
Published: March 2015

While multiple peridynamic material models capture the behavior of solid materials, not all structures are conveniently analyzed as solids. Finite Element Analysis often uses 1D and 2D elements to model thin features that would otherwise require a great number of 3D elements, but peridynamic thin features remain underdeveloped despite great interest in the engineering community. This work presents non-ordinary state-based peridynamic models for the simulation of thin features. Beginning from an example non-ordinary state-based model proposed by Silling in 2007, lower dimensional peridynamic models of beams and plates are developed and shown to be energy equivalent to classical models for well-behaved deformations. The resulting plate model is initially restricted to a Poisson’s ratio of ν = 1/3, but is extended to arbitrary Poisson’s ratio via a bending state decomposition. Simple test cases demonstrate the model’s performance.
Dosimetric characteristics of the novel 2D ionization chamber array OCTAVIUS Detector 1500
Authors: Stelljes T. S. , Harmeyer A. , Reuter J. , Looe H. K. , Chofor N. , Harder D. , Poppe B.
Published: March 2015

Purpose:

The dosimetric properties of the OCTAVIUS Detector 1500 (OD1500) ionization chamber array (PTW‐Freiburg, Freiburg, Germany) have been investigated. A comparative study was carried out with the OCTAVIUS Detector 729 and OCTAVIUS Detector 1000 SRS arrays.

Methods:

The OD1500 array is an air vented ionization chamber array with 1405 detectors in a 27 × 27 cm2 measurement area arranged in a checkerboard pattern with a chamber‐to‐chamber distance of 10 mm in each row. A sampling step width of 5 mm can be achieved by merging two measurements shifted by 5 mm, thus fulfilling the Nyquist theorem for intensity modulated dose distributions. The stability, linearity, and dose per pulse dependence were investigated using a Semiflex 31013 chamber (PTW‐Freiburg, Freiburg, Germany) as a reference detector. The effective depth of measurement was determined by measuring TPR curves with the array and a Roos chamber type 31004 (PTW‐Freiburg, Freiburg, Germany). Comparative output factor measurements were performed with the array, the Semiflex 31010 ionization chamber and the Diode 60012 (both PTW‐Freiburg, Freiburg, Germany). The energy dependence of the OD1500 was measured by comparing the array's readings to those of a Semiflex 31010 ionization chamber for varying mean photon energies at the depth of measurement, applying to the Semiflex chamber readings the correction factor kNR for nonreference conditions. The Gaussian lateral dose response function of a single array detector was determined by searching the convolution kernel suitable to convert the slit beam profiles measured with a Diode 60012 into those measured with the array's central chamber. An intensity modulated dose distribution measured with the array was verified by comparing a OD1500 measurement to TPS calculations and film measurements.

Results:

The stability and interchamber sensitivity variation of the OD1500 array were within ±0.2% and ±0.58%, respectively. Dose linearity was within 1% over the range from 5 to 1000 MU. The effective point of measurement of the OD1500 for dose measurements in RW3 phantoms was determined to be (8.7 ± 0.2) mm below its front surface. Output factors showed deviations below 1% for field sizes exceeding 4 × 4 cm2. The dose per pulse dependence was smaller than 0.4% for doses per pulse from 0.2 to 1 mGy. The energy dependence of the array did not exceed ±0.9%. The parameter σ of the Gaussian lateral dose response function was determined as σ6MV = (2.07 ± 0.02) mm for 6 MV and σ15MV = (2.09 ± 0.02) mm for 15 MV. An IMRT verification showed passing rates well above 90% for a local 3 mm/3% criterion.

Conclusions:

The OD1500 array's dosimetric properties showed the applicability of the array for clinical dosimetry with the possibility to increase the spatial sampling frequency and the coverage of a dose distribution with the sensitive areas of ionization chambers by merging two measurements.