bluuebunny/crossref_metadata_2025 huggingface dataset:
Safe and Automated Tool-Path Generation for Multi-Axis Production Machines
Authors: Ahmad Rafiq , Plapper Peter
Published: March 2015

Multi-axis machines are growing rapidly their precision and complexity with the increasing importance of machine intelligence, automation, optimization and safety. It is necessary to identify collision risks and avoid them in manufacturing otherwise production stops may cost a huge amount to the manufacturing company. This study has focused on safe trajectory generation for CNC machines especially focusing on high risked non-functional trajectories. These machines should be able to see any unwilling situation (i.e. collisions) in their vicinity and must be able to detect and react automatically in real-time for safe tool movements. Currently CAM software and some multi-axis machines are able to detect collisions but they do not have any solution to avoid such collisions automatically. The main objective is to make multi-axis machine vision system effective enough that it can see all its activities regarding collisions and can react or command automatically online as well as off-line for real and virtual productions. In presence of obstacles during manufacturing, the proposed approach will provide decisions regarding trajectory correction and improvement automatically. The proposed vision concept is able to take into account the evolution of the scene i.e. the aspects of changes to the obstacle like shape, size or presence during production. The application presented in this paper is for 2D traversal safe online trajectories generation in virtual simulated dynamic environment, which will be adapted to the real-time real machining scenarios at shop-floor by integrating it with STEP-NC technology in future.
Assessment of the Performance of Microbumped Cutting Tool in Machining of AISI 1045 Steel
Authors: Ma J. , Duong Nick H. , Lei Shuting
Published: March 2015

This paper investigates the performance of microbump textured cutting tool in dry orthogonal machining of mild steel (AISI 1045 steel) using AdvantEdge finite element simulation. Microbumps are designed on the rake face of cemented carbide (WC/Co) cutting inserts. The purpose is to examine the effect of microbump textured tools on machining performance and to compare it with non-textured regular cutting tools. Specifically, the following microbump parameters are examined: microbump width, microbump height, and edge distance (the distance from cutting edge to the first microbump). Their effects are assessed in terms of the main force, thrust force, and chip-tool contact length. It is found that microbump textured cutting tools generate lower cutting force and thrust force and consequently lower the energy consumption for machining. The micobump width, microbump height, and edge distance all have influence on cutting force in their own ways.
Development and Oxidation Test of Metal Mesh Reinforced Ceramic Composite Material
Authors: Kibsey Mitch , Huang Xiao
Published: March 2015

As part of an ongoing research development at Carleton University in ceramic matrix composites (CMCs) for high-temperature gas turbine applications, it was recognized that the performance of an oxide matrix could be improved by incorporating a metal reinforcement material. For this reason, a low cost CMC was created by reinforcing a yttria-stabilized zirconia (7YSZ) ceramic matrix with a Hastelloy X (HX) wire mesh. The CMC was manufactured by coating the HX mesh with a NiCrAlY bond coat, and then 7YSZ ceramic matrix, both using plasma spraying. The bond coat was employed to improve bonding and also to act as an oxygen diffusion barrier. In order to evaluate the performance of the HX/7YSZ composite at high temperatures, isothermal and cyclic oxidation tests were carried out for 1000 hours at 1050°C. The results showed that oxidation resistance was improved by vacuum heat treatment prior to testing due to the formation of stable thermally grown oxides (TGO) on the NiCrAlY bond coat. In the cyclic oxidation test, differences in thermal expansion coefficients caused cracking at interfaces between mesh/bond coat and bond coat/7YSZ. Minimizing the effect of thermal expansion by better material combination, as well as modifying manufacturing methods will allow for improved performance of metal mesh reinforced CMCs.
Thermostructural Analyses Supporting the Design of the HYPROB Heat Sink Subscale Breadboard
Authors: Ferraiuolo M. , Martucci A. , Battista F. , Ricci D.
Published: March 2015

Today’s rocket engines regeneratively cooled using high energy cryogenic propellants (e.g. LOX and LH2, LOX and LCH4) play a major role due to the high combustion enthalpy (10–13.4 kJ/kg) and the high specific impulse of these propellants. In the frame of the HYPROB/Bread project, whose main goal is to design build and test a 30 kN regeneratively cooled thrust chamber, a breadboard has been conceived in order to:

• investigate the behavior of the injector that will be employed in the full scale final demonstrator,

• to obtain a first estimate of the heat flux on the combustion chamber for models validation,

• to implement a “battleship” chamber for a first verification of the stability of the combustion

The breadboard is called HS (Heat Sink) and it is made of CuCrZr (Copper Chromium Zirconium alloy), Inconel 718 and TZM (Titanium Zirconium Molybdenum alloy). The aim of the present paper is to illustrate the thermostructural design conducted on the breadboard by means of a Finite Element Method code taking into account the viscoplastic behavior of the adopted materials. An optimization process has been carried out in order to keep the structural integrity of the breadboard maximizing the life cycles of the component. Heat fluxes generated by combustion gases have been evaluated by means of CFD quick analyses, while convection and radiation with the external environment have not been considered in order to be as conservative as possible from a thermostructural point of view. Transient thermal analyses and static structural analyses have been performed by means of ANSYS code adopting an axisymmetric model of the chamber. These analyses have demonstrated that the Breadboard can withstand the design goal of 3 thermo-mechanical cycles with a safety factor equal to 4 considering a firing time equal to 3 seconds.
RQL Combustion as an Effective Strategy to NOx Reduction in Gas Turbine Engines
Authors: Ingenito Antonella , Agresta Antonio , Andriani Roberto , Gamma Fausto
Published: March 2015

The growing need to drastically reduce aircrafts CO2 emissions has led engineers and scientists in the last years to develop a clean, renewable and sustainable energy system. Hydrogen as a fuel in aviation has shown to be a good choice, since it has an energy release much higher than common and long chain hydrocarbons (119.96 MJ/kg vs ∽42.8 MJ/kg, respectively), a wide flammability limits, a high diffusivity and a very short ignition time. Its thermal conductivity, the highest among all gases, its high heat capacity and its very low dynamic viscosity provide superior cooling properties for operation at high flight speeds and at combustor high temperatures. Furthermore, its low molecular weight makes it the fuel with the higher specific impulse (ISP), ∼450 s: this means that burning 1 kg/s of hydrogen with oxygen produces a thrust of 450 kg-force.

However, for its high combustion temperature, it has been demonstrated to be disadvantageous in terms of NOx production. Although NOx pollution is a relatively small part of global human pollution (less than 4%), a particular feature of air transport is that pollutants from air traffic are emitted at high altitudes, in the upper troposphere/lower stratosphere (8 to 12 km), where they are of greater influence than those emitted at ground level. Moreover, further emission reductions need to be achieved by the air transport community, since air traffic has a growth (3% to 5% per year) which exceeds the technology improvement rate.

Emissions may be controlled by operating at lean or very lean equivalence ratios (thanks to the wider flammability limits of the hydrogen-air flames compared to kerosene-air flames), or reducing the combustor length (thanks to the higher flame speed of hydrogen compared to other fuels), or via innovative strategies. In this paper, the RQL (Rich-Quench-Lean) strategy for the NOx abatement will be proposed for a high speed hydrogen fuelled vehicle.
Multi-Disciplinary Design Optimization of Transonic Fan Blade Design Using Analytical Target Cascading
Authors: Naz Saima , Tribes Christophe , Trépanier J.-Y. , Nichols Jason , Petro Eddy
Published: March 2015

Analytical Target Cascading (ATC), a multilayer multidisciplinary design optimization (MDO) formulation employed on a transonic fan design problem. This paper demonstrates the ATC solution process including the specific way of initializing the problem and handling system level and discipline level targets. High-fidelity analysis tools for aerodynamics, structure and dynamics disciplines have been used. A multi-level parameterization of the fan blade is considered for reducing the number of design variables. The overall objective is the transonic fan efficiency improvement under structure and dynamics constraints. This design approach is applied to the redesign of the NASA Rotor 67. The overall study explores the key points of implementation of ATC on transonic fan design practical problem.
Deformation Prediction of Aero-Structural Assembly Involving Drilling-Induced Stresses
Authors: Wang Hua , Ge Qing
Published: March 2015

Drilling is a material removal process which introduces the plastic deformation and stresses around the hole. When large amounts of drilling stresses are added up, there will be deformation in the aero-structural assembly. This work presents a deformation predicting method based on finite element analysis considering drilling stresses. A riveting equivalent unit is employed to simulate the riveting process in order to obtain a balance between accuracy and the computational efficiency in finite element analyzing. Drilling stresses are added up into the riveting process with additional temperature fields in ABAQUS. The assembly of the two riveted plates and the trailing edge were considered to illustrate effects of drilling stresses coupling. The simulation results had shown that drilling stresses had little influence on one riveting deformation. When so many drilling stresses and riveting effects were added up, there will be striking deformation in the aircraft’s structure. The deformation predicting method outlined in this work will enhance the understanding of the compliant components deformation resulting from the drilling stresses, and help systematically improving the precision control efficiency in civil aircraft industry.
Experimental Verification of Ball-Nose End-Milling Conditions Derived From Catalog-Mining System Based on Classified Inclination Angles of Machining Surface
Authors: Kodama Hiroyuki , Okuda Koichi , Sugaya Yui , Hirogaki Toshiki , Aoyama Eiichi , Ogawa Keiji
Published: March 2015

We previously proposed data-mining system to derive useful information from the data and attempt to determine the ball-nose end-milling conditions in a rapid prototype manufacturing system. Practical end-milling condition decision equations are derived to determine the end-milling conditions at each cluster by using response surface method. End-millings of hardened die steel JIS SKD61 (HRC53) and DH31S were carried out to investigate the practicability of derived mining conditions under contour line milling. As a result, our catalog-mining system was found to be effective in selecting the end-milling conditions as the first trial condition. Catalog mining can derive indicative cutting conditions for unskilled engineers.
Redesign of the B-1B Bomber Inlets for Improved Supersonic Performance
Authors: Berra Lee M. , Olcmen Semih , Slater John W.
Published: March 2015

This paper presents a conceptual study of two alternative inlet concepts for the United States Air Force B-1B bomber to provide for improved supersonic performance with expansion of capabilities to high-altitude, high-speed flight at Mach 2.0. The two inlet concepts are two-dimensional, variable-ramp inlet systems designed to replace the current fixed-geometry, pitot inlets of the B-1B. One inlet incorporates a two-ramp system, while a second inlet incorporates a two-ramp system containing an isentropic contour. The entire inlet system including the supersonic diffuser, throat, cowl lip, and subsonic diffuser sections was designed to maximize the total pressure recovery at the engine fan face to achieve maximum thrust by the engine at Mach 2.0 conditions. Analytic methods implemented into the MATLAB and the NASA SUPIN codes are used to design and analyze the two-dimensional inlet concepts. In addition, high-fidelity WIND-US computational fluid dynamics (CFD) simulations were used to verify the results of the analytic design methods. The results suggest that at Mach 2.0, the total pressure recovery of the inlets could increase from 0.70 to 0.94. The inlet capture area and cowl drag increased; however, the overall improvements resulted in a 98% thrust increase over the existing inlet at the design point.
Dimensional Analysis of Thermal Fields Surrounding Friction Stir Welding Process
Authors: Payton Lewis N. , Chandrasekaran Vishnu Vardhan , Hunko Wesley S.
Published: March 2015

A dimensionless correlation is developed based on Buckingham’s Pi-Theorem to estimate the temperature fields generated by the movement of a tool during the Friction Stir Welding of an aluminum alloy (6061-T6). Symmetrical thermocouple measurements are taken during a statistically designed experiment using different factor levels (RPM, Traverse, etc). Analytical comparison (using multivariate ANOVA) validates the predicted dimensionless correlation including the often-reported difference between the advancing versus retreating side of the Friction Stir Tool.
Study of Cutting Speed Variation in the Ultrasonic Assisted Drilling of Carbon Fibre Composites
Authors: Gupta Aniruddha , Barnes Stuart , McEwen Iain , Kourra Nadia , Williams Mark A.
Published: March 2015

Ultrasonic assisted drilling (UAD) has been proven effective for the thrust force reduction as compared to conventional drilling (CD) for same machining parameters. The following research was focused on the examination of exit delamination, machined surface and cutting temperature measurement in UAD and a comparison to that in CD at the cutting speeds of 0.942 m/min, 9.42 m/min, 94.2 m/min and 282.6 m/min at a constant feed rate of 0.05 mm/rev in the through-hole drilling of CFRP material. X-Ray computed tomography (CT) was used to identify the exit delamination, internal damage, circularity and center deviation in CD and UAD. A maximum of 82.8% reduction in the center deviation and 33.2% reduction in circularity of the holes were found when drilled in UAD as compared to those in CD. Furthermore, the cutting temperature in the drilling of CFRP has been measured and compared for both the cases of CD and UAD. Ultrasonic assistance produced 10°C higher cutting temperature than that in CD at the cutting speed of 282.6 m/min while at lower cutting speeds (0.942 m/min and 9.42 m/min), the cutting temperatures with and without ultrasonic assistance did not have a significant difference (2°C and 4°C respectively).
Effect of Process Parameters on Weld Penetration During Pulsed Nd:YAG Laser Welding
Authors: Hudon Mathew , Saigal Anil
Published: March 2015

Weld penetration is an important parameter to be considered for given process parameters on a pulsed Nd:YAG laser welding machine. A gauge repeatability and reproducibility study (GR&R), components of variation study (COV), and design of experiments (DOE) are used to understand the relationship between the process parameters and weld penetration on 17-4PH H900, 304 Annealed, and 420 Hardened stainless steel pins joined to a 17-4PH H900 stainless steel block. These stainless steels are selected because of their common use for laser welding of medical devices. The function determined via the DOE is then confirmed empirically by trial laser welds at the determined process settings for different weld penetrations. For a given pulse duration (8 ms), laser beam focus diameter (0.4 mm) and cover gas flow rate (5 L/min), the linear regression equation describing the weld penetration, h(mm) as a function of Peak Pulse Power, Pp(W) is found to be h = 0.001657 (Pp) – 0.389 where 300W < Pp < 1100W.
On the Effect of Johnson Cook Material Constants to Simulate Al2024-T3 Machining Using Finite Element Modeling
Authors: Daoud Monzer , Chatelain Jean-François , Bouzid Hakim
Published: March 2015

Finite element modeling (FEM) of machining has recently become the most attractive computational tool to predict and optimize metal cutting processes. High speed computers and advanced finite element code have offered the possibility of simulating complex machining processes such as turning, milling, and drilling. The use of an accurate constitutive law is very important in any metal cutting simulation. It is desirable that a constitutive law could completely characterize the thermo-visco-plastic behavior of the machined materials at high strain rate. However, there exist several constitutive laws that are adopted for machining simulation, the choice of which is difficult to make. The most commonly used law is that of Johnson and Cook (JC) which combines the effect of strains, strain rates and temperatures. Unfortunately, the different coefficients provided in the literature for a given material are not reliable since they affect significantly the predicted results (cutting forces, temperatures, etc.). These discrepancies could be attributed to the different methods used for the determination of the material parameters. In the present work, three different sets of JC are determined based on orthogonal machining tests. These three sets are then used in finite element modelling to simulate the machining behavior of Al 2024-T3 alloy. The aim of this work is to investigate the impact of the three different sets of JC constants on the numerically predicted cutting forces, chip morphology and tool-chip contact length. It is concluded that these predicted parameters are sensitive to the material constants.
Fully Coupled Dynamic Analysis of Electro-Magneto-Mechanical Problems in Electrically Conductive Composite Plates
Authors: Chernikov Dmitry , Zhupanska Olesya I.
Published: March 2015

This paper will present a numerical method for solving fully coupled dynamic problems of the mechanical behavior of electrically conductive composite plates in the presence of an electromagnetic field. The mechanical behavior of electrically conductive materials in the presence of an electromagnetic field is described by the system of nonlinear partial differential equations (PDEs), including equations of motion and Maxwell’s equations that are coupled through the Lorentz ponderomotive force. In the case of thin plates, the system of governing equations is reduced to the two-dimensional (2D) time-dependent nonlinear mixed system of hyperbolic and parabolic PDEs. This paper discusses a numerical solution method for this system, which consists of a sequential application of the Newmark finite difference time integration scheme, spatial (with respect to one coordinate) integration scheme, method of lines (MOL), quasilinearization, and a finite difference spatial integration of the obtained two-point boundary-value problem. The final solution is obtained by the application of the superposition method followed by orthonormalization.
Investigation and Improvement of Thermal Efficiency of Hypersonic Scramjet
Authors: Hossain Mohammad A. , Rahman Md. Taibur , Soiket Mohammad Ikthair Hossain , Hossain Sarzina
Published: March 2015

This work is focused on investigation of thermal efficiency of a Hypersonic scramjet engine and propose some improvement of thermal efficiency based on thermodynamic and fluid flow analysis. Thermal management system is one of the main research fields in scramjet design. As it has no moving parts, the total thermal efficiency depends on inlet conditions, conditions of combustor exit and conditions of the engine exit. A combustor exit condition dictates the velocity and temperature after combustion. we concentrate our focus on this section. The first part of the paper, we tried to describe the fundamental exergy relationship for scramjet and we developed the relation of exergy distribution and exergy delivery rate. From an extensive literature review, we have found the relations between fluid velocity, pressure and temperature, which is described in the later part of the paper. Our main focus is to develop a combined relation of thermal efficiency in terms of engine exit velocity, temperature and air-fuel ratio. Different characteristic parameters such as overall efficiency, thermal efficiency, specific impulse have been determined at different inlet temperature ratio or the cycle static temperature ratio (T3/T0) and an optimum inlet temperature ratio is proposed for maximum overall efficiency.
Methodology for Negotiation in Collaborative Working Environment for Innovation in Services Design
Authors: Coutinho Carlos , Jardim-Goncalves Ricardo , Cretan Adina
Published: March 2015

Service-oriented technologies drive new ways to perform interoperability between manufacturing companies. The aerospace segment is a highly competitive area, supported by numerous partners and applications which need to collaborate and to be interoperable. Particularly, the subcontracted small and medium enterprises (SMEs) need to be flexible towards the changes that are imposed by the major contractors, doing so at the lowest cost. This paper proposes a framework which advocates negotiations as a pillar mechanism to support innovation during the development of services in industrial collaborative working environments.
Method to Calculate Aircraft VNAV Trajectory Cost Using a Performance Database
Authors: Murrieta-Mendoza Alejandro , Botez Ruxandra
Published: March 2015

Vertical Navigation (VNAV) trajectory optimization has been identified as a means to reduce fuel consumption. Due to the computing power limitations of devices such as Flight Management Systems (FMSs), it is very desirable to implement a fast method for calculating trajectory cost using optimization algorithms. Conventional trajectory optimization methods solve a set of differential equations called the aircraft equations of motions to find the optimal flight profile. Many FMSs do not use these equations, but rather a set of lookup tables with experimental, or pre-calculated data, called a Performance Database (PDB). This paper proposes a method to calculate a full trajectory flight cost using a PDB. The trajectory to be calculated is composed of climb, acceleration, cruise, descent and deceleration flight phases. The influence of the crossover altitude during climb and step climbs in cruise were considered for these calculations. Since the PDB is a set of discrete data, Lagrange linear interpolations were performed within the PDB to calculate the required values. Given a takeoff weight, the initial and final coordinates and the desired flight plan, the trajectory model provides the Top of Climb coordinates, the Top of Descent coordinates, the fuel burned and the flight time needed to follow the given flight plan. The accuracy of the trajectory costs calculated with the proposed method was validated for two aircraft; one with an aerodynamic model in FlightSIM, software developed by Presagis, and the other using the trajectory generated by the reference FMS.
Flow Structure on a Retreating Rotor Blade at High Advance Ratios
Authors: Mayo Michael , Raghav Vrishank , Barbely Natasha , Liberi Brandon , Komerath Narayanan
Published: March 2015

This paper provides unambiguous velocity-field proof that a strong edge vortex occurs on a rotating blade in reverse flow. The rotor blades of a helicopter encounter reverse flow during flight at high advance ratio. Reverse flow is a limiter in rotorcraft design with excursions in pitch link loads and bending moments. Stereo particle-image velocimetry is used on the flow under the retreating blade of a two-bladed teetering rotor system in a low speed wind tunnel. The results are correlated with earlier aerodynamic loads and flow visualization data using the same rotor blade planform placed in a yawed, fixed-wing position. Results obtained with the blade held fixed at several rotor azimuths and angles of attack are used to ascertain the rotation effects on the flowfield by comparison with rotating blade results. Initial results suggest that radial velocity due to rotation hinders separation and delays the formation of an attached vortex, compared to the static case. The circulation of the reverse flow attached vortex is of the same order of magnitude as the bound circulation of the airfoil section, proving that the vortex contributes significantly to the lift force in addition to the pitching moment.
Viscous Effects on Performance of Linear Plug Micronozzles
Authors: Pearl Jason M. , Louisos William F. , Hitt Darren L.
Published: March 2015

A parametric, two-dimensional, computational study examining steady-state plug micronozzle performance has been conducted. As part of the study, a new method for plug contour construction is proposed. The performance of several different nozzle geometries is compared to that of a traditional plug nozzle geometry designed using the Method of Characteristics (MOC). New nozzle designs are derived from the MOC based design and geometric transformations are used to produce plug nozzles of reduced length. Spike lengths corresponding to 60, 50, 40, and 27% of the MOC nozzle’s length are examined. The throat Reynolds number is varied from 80–820. Thrust is used a metric to assess nozzle performance. The geometry which maximizes performance is found to vary with Reynolds number. It is observed that reducing the plug length improves thrust production for the range of Reynolds number examined.
Using Genetic Algorithms to Optimize the Build Orientation for Fused Deposition Modeled Components Containing Internal Reinforcement Structures
Authors: Eiliat Hasti , Urbanic Ruth Jill
Published: March 2015

Fused Deposition Modeling (FDM) is an additive fabrication process that builds a part from extruded filaments of a melted thermoplastic. Typically, the parts are built using a ‘solid’ (complete fill) or ‘shell’ (3–4 mm external boundary with a loose internal weave) strategy. The introduction of parametric internal structures to support the required tensile or compressive loads provides an intermediate solution to the standard build options, and reduces the material usage while reinforcing the part as required. The internal structures can have a hexagonal, pyramidal, or orthogonal configuration. Because of the configuration variation, the internal structure form arrangement and geometric structure will influence the optimal build orientation. This will have an effect on the productivity or build time, mechanical properties such as strength, surface finish, materials usage and the total build cost. This paper presents a model to optimize the orientation of a part for FDM fabrication while considering these various factors. The CAD part model (in STL format) is an input to the system. A genetic algorithm is used to obtain optimum orientation of the parts for FDM. The objective function for optimization is considered a weighted average of the performance measures such as build time, part quality, material usage, surface finish, interior geometry, strength characteristics, and related parameters. The merits of the approach will be demonstrated using models with varying levels of complexity. The final model tested consists of a human tibia.
Tribological Investigation of Copper (Cu) and Copper Oxide (CuO) Nanoparticles Based Nanolubricants for Machine Tool Slideways
Authors: Nesappan Saravanakumar , Palanisamy Nallasamy , Chandran Mahesh
Published: March 2015

The present study intends to evaluate the tribological characteristics of Copper (Cu) and Copper oxide (CuO) based nanolubricant for its use in machine tool slideways. Different sizes of copper and copper oxide particles were chosen and physical characterisation were carried out using scanning electron microscope (SEM) and transmission electron microscope (TEM). The nanolubricants were prepared by adding various proportions (0.1%, 0.25%, 0.4% wt) of the particles in Polyalphaolefin (PAO) base oil with lecithin and oleic acid surfactants. Friction and stick-slip characteristics of the nanolubricants were assessed using pin-on-block reciprocating friction monitor simulating the actual loading conditions prevailing in machine tool slideways. Studies were also conducted under elevated temperatures to ascertain the performance of particles at higher temperatures. Extreme pressure properties of the lubricants were studied using Four Ball Tester. The results of the experiments were compared with ISO VG 32 oil, a conventional mineral lubricant meant for machine tool slideways and it was found that the tribological properties nanolubricants using both the nanoparticles were considerably better. The coefficient of friction found to be decreased by 2.5% and 17.5% for copper particles with 0.1% weight composition in ambient temperature and elevated temperature respectively. Whereas for copper oxide particles with 0.1% weight composition a reduction of 14.25% and 10% were obtained.
Virtual Commissioning by Means of an Adaptive Selection of the Modeling Depth
Authors: Schmüdderrich Tanja , Trächtler Ansgar
Published: March 2015

In many areas of modern engineering, especially in the field of plant engineering, models have become indispensable. Models are not only used for construction, but also to simulate the system behavior e.g. for the control design or during virtual commissioning (VC). In all applications, it has to be decided how detailed the created models should be. For this, a methodology for selecting the modeling depth can be used, which is based on four different modeling depths. However, if requirements change during the operation of the system, it may be necessary to change the modeling depth during simulation run time. The main purpose of this article is to present an approach which allows the modeling depth to be adjusted in terms of changing conditions during simulation runtime. This approach is illustrated by an example of a material flow system.
Evaluation of Zinc Coating Adhesion in Stamping Advanced High Strength Steel
Authors: Shih Hua-Chu
Published: March 2015

Advanced high strength steels (AHSS) have been widely used in vehicle structural components due to their high strength properties balanced with good formability. In many applications, a zinc coating is often applied to AHSS for the corrosion protection. Due to the high strength properties of AHSS, higher forming forces and binder pressures are also required in stamping AHSS, which often results in coating powdering/flaking or galling around the draw bead and die radius areas. The degree of coating powdering/flaking depends upon forming process variables such as draw bead force, forming speed, lubrication, and die temperatures. This study was designed to develop a lab-based coating adhesion test to quickly characterize the coating adhesion behavior of AHSS. In this study, both the bending under tension test and the modified draw bead test were used. A typical substrate of AHSS is coated with either a hot-dip Galvannealed (GA) or a Galvanized (GI) coating. In this study, dual phase (DP) steels with tensile strength levels of 600, 780 and 980 MPa were investigated at two different thicknesses and with two different coating types, GI and GA. The results reveal that GA tends to have worse coating adhesion than GI coatings under normal forming conditions. However, GI coatings are more sensitive to the lubrication condition and have worse coating adhesion than GA coatings under a larger draw bead penetration and smaller draw bead corner radius condition.
Liquid Metal Inks for Flexible Electronics and 3D Printing: A Review
Authors: Wang Lei , Liu Jing
Published: March 2015

Flexible electronics and 3D printing are quickly reshaping the world in many aspects spanning from science, technology to industry and social society. However, there still exist many barriers to impede further progress of the areas. One of the biggest bottlenecks lies in the strong shortage of appropriate functional inks. Among the many printable materials ever tried such as conductive polymers, powdered plastic, metal particles or other adhesive materials, the liquid metal or its alloy is quickly emerging as a powerful electronic ink with diverse capabilities from which direct printing of flexible electronics and room temperature 3D printing for manufacturing metal structures are enabled. All these fabrication capabilities are attributed to the unique properties of such metal’s low melting point (generally less than 100 °C), flowable feature and high electrical conductivity etc. To better push forward the research and application of the liquid metal printed electronics and 3D manufacture, this article is dedicated to present an overview on the fundamental research advancements in processing and developing the liquid metal inks. Particularly, the flow, thermal, phase change and electrical properties of a group of typical liquid metals and their alloy inks will be systematically summarized and comparatively evaluated. Some of the practical applications of these materials in a wide variety of flexible electronics fabrication, 3D printing and medical sensors etc. will be briefly illustrated. Further, we also explained the basic categories of the liquid metal material genome towards discovering new functional alloy ink materials as initiated in the authors’ lab and interpret the important scientific and technical challenges lying behind. Perspective and future potentials of the liquid metal inks in more areas were also suggested.
Indirect Additive Manufacturing Based Casting (I AM Casting) of a Lattice Structure
Authors: Mun Jiwon , Ju Jaehyung , Thurman James
Published: March 2015

Direct-metal additive manufacturing (AM) processes such as Selective Laser Melting (SLM) and Electron Beam Melting (EBM) methods are being used to fabricate complex metallic cellular structures with a laser or electron beam over a metal powder bed. Even though these processes have excellent capabilities to fabricate parts with cellular mesostructures, there exist several constraints in the processes and applications: limited selection of materials, high thermal stress by the high local energy source, poor surface finish, and anisotropic properties of parts caused by combined effects of one-dimensional (1D) energy based patterning mechanism, the deposition layer thickness, powder size, power and travel speed of laser or electron beam. In addition, manufacturing cost is still high with the Direct-metal AM processes. As an alternative for manufacturing metallic 3D cellular structures, which can overcome the disadvantages of direct-metal AM techniques, polymer AM methods may be combined with metal casting. We may call this “Indirect AM based Casting (I AM casting)”. The objective of this study is to explore the potential of I AM Casting associated with development of a novel manufacturing process — Indirect 3D Printing based centrifugal casting which is capable of producing multifunctional metallic cellular structures with internal cooling channels having a 2mm inner diameter and 0.5mm wall thickness. We characterize polymers by making expendable patterns with a polyjet type 3D printer; e.g., modulus, strength, melting and glass transition temperatures and thermal expansion coefficients. A transient flow and heat-transfer analysis of molten metal through 3D cellular network mold will be conducted. Solidification of molten metal through cellular mold during casting will be simulated with temperature dependent properties of molten metal and mold over a range of running temperatures. The volume of fluid (VOF) method will be implemented to simulate the solidification of molten metal together with a user defined function (UDF) of ANSYS/FLUENT. Finally, experimental validation will be conducted.
Mechanical Characteristics and Design of Bolted T-Shape Flange Joints Subjected to Tensile Loadings
Authors: Sawa Shunichiro , Omiya Yuya , Ishimura Mitsutoshi , Sawa Toshiyuki
Published: March 2015

Bolted joints have been widely used in mechanical structures. However, a design of bolted joints has been carried out empirically. In designing a bolted joint, it is necessary to know a ratio of increment Ft in axial bolt force to an external tensile loading W, that is, the load factor φ=Ft/W. In our previous paper, the new formulation for obtaining the value of the load factor φ for a bolted joint in which two hollow cylinders were clamped was proposed by introducing the tensile spring constant Kpt for clamped parts. Then, it is shown that the values of the load factor of bolted joint obtained from our formulation are in a fairly good agreement with the experimental values. In addition, the effect of the position where an external load is applied to the joint is significant on the value of the load factor. In the present paper, a method for obtaining the value of the load factor for bolted T-shape flange joints in which two T-shape flanges are clamped by two bolts and nuts under tensile loadings is demonstrated using two-dimensional theory of elasticity. In the analysis of the load factor φ, the compressive spring constant Kc for a hollow cylinder around the bolt hole is calculated. The value of the correction factor Kc′/Kpt is also analyzed using the two-dimensional theory of elasticity. When the external tensile loads are applied to the joints, the bolts are inclined and as the result, the bending moment occurs in the bolts. A method for analyzing the bending stress in the bolts is also demonstrated. In the numerical calculations, the distance C between the bolt position and the center of T-shape flange is varied and the effect of the distance C on the load factor is examined. For the validation of the analyses, calculations are also carried out. Experiments to measure the load factor and the maximum stress due to the bending moment occurred in the bolts were carried out. The numerical results of the load factor and the maximum stress in the bolts are fairly coincided with the experimental results. Furthermore, a design method for the joints is discussed, that is, how to determine the bolt position C, the bolt preload for the external tensile loading, how to choose the bolt strength.
SJA-Based Robust Nonlinear Control of Airfoil Gust-Induced LCO
Authors: Nguyen Lap , Pedroza Natalie Ramos , MacKunis William , Golubev Vladimir
Published: March 2015

We examine a new robust nonlinear flight control technology that employs an array of synthetic-jet micro-actuators embedded in UAV wing design in order to completely eliminate moving parts (such as ailerons) thus greatly enhancing maneuverability required for small fixed-wing air vehicles operating, e.g., in tight urban environments. Estimated fast response times are critical in mitigating gust effects while greatly improving flight stability and control. The new controller design is particularly advantageous for high levels of uncertainty and nonlinearity present both in the unsteady flow-path environment and in the embedded actuator’s response. The current work focuses on a benchmark case of flutter control of 2-DOF elastically-mounted airfoil entering limit-cycle oscillations (LCO) due to impinging upstream flow disturbance. Preliminary parametric studies conducted for various SJA excitation amplitudes and frequencies examine the thresholds of the actuator’s control authority to produce a desirable impact.
Direct Contact Heating for Hot Forming Die Quenching
Authors: Rasera J. N. , Daun K. J. , D’Souza M.
Published: March 2015

Most hot forming lines use slow, energy-intensive roller hearth furnaces to austenitize boron steel “blanks”. This paper describes an alternative heating technology in which blanks are austenitized by bringing them into contact with a hot monolith. The austenitizing temperature was reached in less than 30 seconds, and subsequent material characterization tests on oil-quenched blanks confirm that a fully martensitic structure is formed, and that the hardness and yield strength are comparable to furnace-treated samples. An Al-Si coating is typically used to prevent the oxidation and decarburization of the blanks within the furnace; preliminary tests found that the coating adheres to the monolith, impeding blank transfer and damaging the Al-Si-Fe ternary coating. Five interchangeable striking surfaces were assessed to see if they were less prone to adhering to the molten Al-Si coating.
A Numerical Study of High Temperature and High Velocity Gaseous Hydrogen Flow in a Cooling Channel of a Nuclear Thermal Rocket Core
Authors: Akyuzlu K. M.
Published: March 2015

Two mathematical models (a one-dimensional and a two-dimensional) were adopted to study, numerically, the thermal hydrodynamic characteristics of flow inside the cooling channels of a Nuclear Thermal Rocket (NTR) engine. In the present study, only a single one of the cooling channels of the reactor core is simulated. The one-dimensional model adopted here assumes the flow in this cooling channel to be steady, compressible, turbulent, and subsonic. The physics based mathematical model of the flow in the channel consists of conservation of mass, momentum, and energy equations subject to appropriate boundary conditions as defined by the physical problem stated above. The working fluid (gaseous hydrogen) is assumed to be compressible through a simple ideal gas relation. The physical and transport properties of the hydrogen is assumed be temperature dependent. The governing equations of the compressible flow in cooling channels are discretized using the second order accurate MacCormack finite difference scheme. Convergence and grid independence studies were done to determine the optimum computational cell mesh size and computational time increment needed for the present simulations. The steady state results of the proposed model were compared to the predictions by a commercial CFD package (Fluent.) The two-dimensional CFD solution was obtained in two domains: the coolant (gaseous hydrogen) and the ZrC fuel cladding. The wall heat flux which varied along the channel length (as described by the nuclear variation in the nuclear power generation) was given as an input.

Numerical experiments were carried out to simulate the thermal and hydrodynamic characteristics of the flow inside a single cooling channel of the reactor for a typical NERVA type NTR engine where the inlet mass flow rate was given as an input. The time dependent heat generation and its distribution due to the nuclear reaction taking place in the fuel matrix surrounding the cooling channel. Numerical simulations of flow and heat transfer through the cooling channels were generated for steady state gaseous hydrogen flow. The temperature, pressure, density, and velocity distributions of the hydrogen gas inside the coolant channel are then predicted by both one-dimensional and two-dimensional model codes. The steady state predictions of both models were compared to the existing results and it is concluded that both models successfully predict the steady state fluid temperature and pressure distributions experienced in the NTR cooling channels. The two dimensional model also predicts, successfully, the temperature distribution inside the nuclear fuel cladding.
On the Robustness of the Volumetric Shrinkage Method in the Context of Variation Simulation
Authors: Lorin Samuel , Cromvik Christoffer , Edelvik Fredrik , Lindkvist Lars , Söderberg Rikard
Published: March 2015

Welding induces high temperatures that cause residual stresses and strains in the welded structure. With a welding simulation, these stresses and strains may be predicted. A full simulation implies performing a transient thermal and a quasi-static mechanical analysis. These analyses usually involve a large number of time steps that leads to long simulation times. For welding distortions, there are approximate methods that require considerably less time. This is useful when simulating large structures or for analyses that use an iterative approach common in optimization or variation simulation. One of these methods is volumetric shrinkage, which has been shown to give reasonable results. Here it is assumed that the driving force in welding distortion is the contraction of the region that has been melted by the weld. In volumetric shrinkage, the nodes that are inside the melted region are assigned a uniform temperature and the distortion is calculated using elastic volumetric shrinkage. Although this method has been shown to give reasonable predictions, we will show that it is sensitive to small perturbations, which is an essential part in variation simulation. We also propose a modification of the volumetric shrinkage method that addresses this lack of robustness; instead of defining the melted region by applying a uniform temperature to the nodes inside the zone, we formulate an optimization problem that finds a temperature distribution such that the local melted volume is preserved. A case study with application to variation simulation has been used to elicit the proposed method.
Sheet Metal Blank Development of a Deep Drawing Fan Support Using Theoretical Rules and FEM
Authors: Garcia Zugasti Pedro de Jesus , Salcedo Murillo Erick M. , Medellín Castillo Hugo I. , De Lange Dirk Frederik , Granja Juan Gabriel Sandoval
Published: March 2015

Deep drawing is a cost effective sheet metal forming process to produce many industrial components. However, complex geometrical drawn parts are difficult to form due to several modes and conditions of the material flow. Commonly problems associated to the forming operation are wrinkling and tearing defects, which affect the cost and quality of the parts. Actually, there are not theoretical methods developed in the literature yet, so the trial and error method are used to reduce or eliminate the deep drawing defects or inclusive is utilized in the earlier production stages, resulting in higher costs and longer production times.

This paper describe a proposed solution to reduce or eliminate the wrinkles defects on the flanges of an industrial fan support that result from applying the forming process. An analysis procedure based on the development of the correct sheet metal blank considering three different blank geometries was proposed. The analysis include the analytical methods available in the literature, the simulation with a computer program based on the Finite Element Method (FEM) and experimentation. FEM model, simulation and results, these were validated by measuring the thickness profile on the flanges of a deep drawing part, before and after the procedure implementation. The results have shown that combining both the analytical and FEM methods, were possible to know the influence degree of the sheet metal blank geometry to reduce or eliminate the wrinkle defect and these can be used as an effective design tool.