bluuebunny/crossref_metadata_2025 huggingface dataset:
A Smooth Multimode Waveform Command Shaping Considering the Effect of Hoisting
Authors: Alhazza Khaled A.
Published: February 2017

Input shaping and command shaping control techniques are the subject of large body of research in the past several decades. Most of the research is dedicated to time invariant single-mode systems. For a double pendulum hoisting system, hoisting results in a complex system of equations of motion. For rest-to-rest maneuvers, it is a common practice in research to split maneuvers into three consecutive independent stages; hoisting up the payload from an initial position, moving it horizontally, and finally lowering it to a final location. Input shaping is used is the horizontal travel motion stage to eliminate inertia excited vibrations. Although, this approach is effective, significant time penalties are involved due to the split motion approach. Further, traditional input shaping techniques involve significant jerks in the motion commands. To overcome these drawbacks, a new smooth waveform command shaping technique is proposed to enable concurrent hoisting and travel actions. The equations of motion including time varying coefficients are derived and used to determine the coefficients of an optimum waveform shaped command profile. Genetic algorithm optimization technique is used to find the optimal values of the command parameters. The initial values of these parameters are determined assuming a constant cable length. The effectiveness of the shaped command is demonstrated through numerical simulations and experiments on a scaled model of double pendulum using different maneuvers involving simultaneous travel and linear hoisting.
Dynamic Instability of Cantilever Beams With Open Cross-Section
Authors: Coaquira Júlio C. , Gonçalves Paulo B. , Carvalho Eulher C.
Published: February 2017

Structural elements with thin-walled open cross-sections are common in metal and composite structures. These thin-walled beams have generally a good flexural strength with respect to the axis of greatest inertia, but a low flexural stiffness in relation to the second principal axis and a low torsional stiffness. These elements generally have an instability, which leads to a flexural-flexural-torsional coupling. The same applies to the vibration modes. Many of these structures work in a nonlinear regime, and a nonlinear formulation that takes into account large displacements and the flexural-flexural-torsional coupling is required. In this work a nonlinear beam theory that takes into account large displacements, warping and shortening effects, as well as flexural-flexural-torsional coupling is adopted. The governing nonlinear equations of motion are discretized in space using the Galerkin method and the discretized equations of motion are solved by the Runge-Kutta method. Special attention is given to the nonlinear oscillations of beams with low torsional stiffness and its influence on the bifurcations and instabilities of the structure, a problem not tackled in the previous literature on this subject. Time responses, phase portraits and bifurcation diagrams are used to unveil the complex dynamic.
Small Form Factor Peltier-Based Liquid Cooling for High Power Density Electronics
Authors: Panigrahy Arunima , Pang Ying Feng , Xia Amy , Polyanko Victor P.
Published: February 2017

Water block and thermoelectric cooler (TEC) are two of the main components in a peltier-based cooling solutions. An optimized water block design and high performance TEC are the key to having a good peltier-based cooling solution. In this study, experimental investigations were performed on small form-factor peltier-based cooling solutions designed for high density electronics. The experiments were conducted in four incremental steps in evaluating the thermal performance of water block with different manufacturing options, different sizes and capabilities of the off-the-shelf TECs, TECs’ optimal operating voltage, thermal performance of the peltier-based liquid cooling solutions, and finally the reliability of the TECs through temperature cycling.
Wind Tunnel Test of a Blended Wing Aircraft in Ground Effect With Active Flow Control
Authors: Mayo Michael , Carroll Jonathan , Motahari Nicholas , Lee Warren , Englar Robert
Published: February 2017

This paper describes the test methodology and results for a wind tunnel experiment featuring a blended wing aircraft in ground effect with built-in circulation control. A 82.55cm wingspan blended wing model was tested in a subsonic wind tunnel at velocities ranging from 18m/s – 49m/s and corresponding Reynolds numbers ranging from 130k – 350k. Pitch angle was held constant at 0 degrees and the height above the wind tunnel floor was modified to determine lift and drag modification due to ground effect. At a normalized height (y/bw) of 0.06, ground effect increased lift production by 24% and reduced drag by 22% when compared to a normalized height of 0.5. The addition of the circulation control significantly increased the lift production of the model at a cost of increased drag. At a normalized height of 0.031, the lift production increased by 200% at a blowing coefficient of 0.01, but the drag also increased by 72%, ultimately increasing L/D by 178%. Experimental results also suggest that ground effect and circulation control have a synergistic effect when used simultaneously. The effects of Reynolds number and circulation control slot height are also investigated.
Characterization of Three-Constituent Interface in CNT-Embedded Nanocomposites
Authors: Subramanian Nithya , Rai Ashwin , Chattopadhyay Aditi
Published: February 2017

An atomistic methodology to simulate the constituent interphases in carbon fiber reinforced CNT/epoxy nanocomposites is presented in this paper. Two critical interphase regions are considered in the study: CNT/polymer interphase and the fiber/matrix interphase. The elastic and inelastic responses of the interphases are investigated through molecular dynamic (MD) simulations with appropriate force fields, and integrated with an atomistically informed multiscale modeling framework. The elastic behavior is studied at the molecular level using harmonic force fields whereas bond elongation and subsequent bond dissociation in epoxy polymer chains, and the fiber/matrix interphase are investigated using a bond order based force field. An MD simulation approach adopted from the concept of quasi-continuum (QC) is employed to calculate the bond dissociation energy during virtual deformation tests. The variation of bond dissociation energy density during the deformation tests is integrated into a continuum damage mechanics model to characterize microscale damage in the epoxy matrix. Furthermore, the atomistic force-displacement behavior is also extracted to formulate a traction-separation law for the microscale cohesive zone models for the fiber/matrix interface.
Correlation of Strain on Instrumentation to Simulated Posterolateral Lumbar Fusion in a Sheep Model
Authors: Munro Deborah S. , Gupta Munish C.
Published: February 2017

Determining the stability and integrity of posterolateral lumbar spinal fusions continues to be one of the leading challenges facing surgeons today. Radiographs have long been the gold standard for evaluating spinal fusion, but they often give delayed or inaccurate results.

It is the goal of this research to develop a new method for determining the strength and stability of a posterolateral lumbar spinal fusion using a sensor based on two strain gauges attached to a spinal rod. It was hypothesized that the spinal implants, in particular the plates or rods, would respond to this change in strain as the stiffness of the fusion increased.

To investigate this hypothesis, an in vitro sheep model of the lumbar spine was developed and bony fusion was simulated with polymethylmethacrylate (PMMA), also known as bone cement. Eight sheep spines were prepared for use in a test fixture that applied a physiological moment of 5 Nm in flexion. One of the spinal rods was instrumented with two strain gauges in a Wheatstone half bridge, and all of the results were ported directly to a data collection system on a dynamic fatigue test machine.

For each spine, the magnitude of the strain was plotted versus amount of simulated fusion. To evaluate the effect of simulated fusion, a moving average of the slope of three sequential strain values was used.

The results showed there is a strong correlation between strain and spinal fusion and that a computer algorithm could be developed that would be more accurate than current techniques in predicting when a spinal fusion is mature enough for a patient to resume normal activities.
Experimental and Theoretical Modeling of Cargo Sloshing During Braking
Authors: Romero Navarrete José Antonio , Otremba Frank
Published: February 2017

Taking into account a multitude of experimental and theoretical studies reported in the literature, the braking efficiency of road tankers can be affected by the sloshing forces developed by the carried liquid during such maneuvers, as a result of the dynamic pressures exerted by the sloshing liquid on the vehicle containers walls, and of the shifting of the liquid center of gravity. However, such studies have not involved a full scale experiment. In this paper, a simplified model is proposed to study the effect of the sloshing dynamics on a road tanker braking efficiency. Results from this simplified approach, are compared with data from full scale testing, revealing that the simplified model is good to predict the maximum pressure that the sloshing liquid exerts on one of the vehicle chambers. The simplified model considers a straight truck and a pendulum analogy for the sloshing liquid, whose parameters are derived from a validated methodology to predict the sloshing frequency of the fluid within its container. Simulation of non-sloshing cargo further suggests that the stopping time can be increased by 7 % due to the sloshing cargo.
Case-Based Support to Sustainable Interoperability and Decision in Enterprise Networks
Authors: Marques Maria , Agostinho Carlos , Jardim-Gonçalves Ricardo
Published: February 2017

Nowadays companies do not thrive solely through their own individual efforts and isolated knowledge. Enterprises have to become agile, sensitive to changes in market forces, and capable of responding with incremental modifications in business and services provided (adaptation) as well as anticipating radical changes by responding with new and breakthrough business models (innovation). This involves a mix of both cooperative and competitive elements, where decision support, evolving information systems, and the use of networking concepts such as the virtual enterprise or the enterprise ecosystem is becoming more common. The approach here presented aims at facilitating and sustaining interoperability in a dynamic networked enterprise environment. Relying on domain-based semantic translation services, sustainable interoperability enables each organization to keep its own terminology and seamlessly communicate with others (i.e. enterprise interoperability). This work contributes to that paradigm, proposing a novel mechanism based in probabilistic analysis (PA), case-based reasoning (CBR) and similarity calculation (SC) to support decision, service redesign and mapping modifications, e.g. when a company changes its internal model but wants to ensure that communication with external entities is not affected.
Chaotic Behavior in the Double Pendulum Under Parametric Resonance
Authors: Avanço Rafael H. , Navarro Helio A. , Nabarrete Airton , Balthazar José M. , Tusset Angelo Marcelo
Published: February 2017

In literature, the classic parametrically excited pendulum is vastly studied. It consists of a pendulum vertically displaced with a harmonic motion in the support while it oscillates. The chaos in this mechanism may appear depending on the frequency and amplitude of excitation in superharmonic and subharmonic resonance. The double pendulum is also well analyzed in literature, but not under parametric excitation. Therefore, this is the novelty in the present paper. The present analysis considers a double pendulum under a harmonic excitation following the same idea performed previously for a single pendulum. The results are obtained based on methods, such as, phase portraits, Poincaré sections and bifurcation diagrams. The 0–1 tests analyze the presence of chaos while the parameters are varied. The dimensionless parameters take into account the excitation frequency and amplitude as mentioned for the classic parametric pendulum. In this case, we have the particular characteristic that the two pendulums have the same length, the same mass and the same friction coefficient in the joints. The types of motion observed include fixed points, oscillations, rotations and chaos. Results also demonstrated that there was a self-synchronization between these pendulums in ideal excitation.
Effect of Chemical Fuel Additives on Liquid Fuel Saving, and Emissions for Heavy Fuel Oil
Authors: Emara Ahmed
Published: February 2017

As fossil fuel resources are considered non-renewable sources of fuel, they will be totally consumed in the near or far future. Due to the intensive and extensive consumption of these fossil fuels in all life sectors such as transportation, power generation, industrial processes, and residential consumption, it is important to find other new methods to cover this fuel demand. Fuel additives are chemicals used to enhance fuel combustion performance, save fuel amounts required for combustion, and correct deficiencies in power and efficiency during consumption. The fuel additives are blended with the traditional fuel even by parts per million range for controlling chemical contaminants and emission reduction.

In the present work, the experimental measurements were done, to evaluate the effect of fuel additive blending with the raw heavy fuel oil (Mazut) on fuel saving which is of a great significance, emissions control, and combustion characteristics as well as the combustion efficiency. These measurements are as follows: initial temperature of Mazut, exhaust gas temperature at the end of combustor, air and fuel mass flow rates to determine the heat load, inlet and outlet temperatures of cooling water, mass flow rate of water, concentration of different exhaust gases, acoustic (noise level) measurements, smoke number, and flame length. These measurements are performed using swirled vanes, co-axial, and double heavy fuel nozzle (1.5 gal/hr for each one) burner with maximum heating load of 550 kW.

GC-MS (Gas chromatography-mass spectrometry) analysis was performed by using Hewlett Packard model 5890 equipped with a flame ionization detector (FID) to identify the fuel additives substances within the tested samples.

The results reveal that the use of fuel additives improves the combustion characteristics and play an important role in fuel saving as well as emission and combustion process.
Adaptive Gimbal Control Approach to Account for Power Consumption and Landmark Tracking Quality
Authors: Tatoglu Akin , Campana Claudio
Published: February 2017

Unmanned Aerial Vehicles (UAV) are commonly used for robotics research and industrial purposes. Most of the autonomous applications use visual sensors and inertial measurement units for localization. Design constraints of such systems are defined considering smooth operation requirements such as indoor environments without external forces where input tracking signal is constant during an operation. In this research paper, we simultaneously investigate and compare stability, power consumption and landmark tracking quality of a visual sensor mounted gimbal specifically for rapid UAV motion requirements where input signal continuously varies such as at obstacle rich environments. We not only attempt to find efficient control parameters but also compare these settings with power consumption and landmark tracking quality metric which are vital for mobile robots and localization algorithms. Efficiency of the system response is analyzed with rise and settling time as well as oscillation amplitude and frequencies. These parameters are tested and benchmarked with various voltage and current limitations. In addition to that, different response behaviors were investigated considering landmark tracking quality metrics including feature detection and image blur. We have shown that gimbal stabilization controller under continuously varying input signal requires less responsive behavior to keep landmark tracking accuracy stable. Initial simulation results, system development and experimental setup procedure are explained and behavior plots for each topic are listed and analyzed.
Classical Control Design for a Gyroscopically Stabilized Inverted Pendulum
Authors: Luecke Greg R. , Walck Chris
Published: February 2017

This work reports on the design and development of an inverted pendulum using a control moment gyro as a stabilizing mechanism. A common educational demonstration calls for a person to stand on a pivoting platform, and hold a spinning bicycle tire with one hand on each side of the axle. As the person rotates their arms, they begin to spin on the platform. This is due to the interesting effect of the control moment gyro. Similarly, this paper suggests the use of control moment gyros as a compact way of dynamically controlling objects. This paper will first discuss some of the current applications of control moment gyro systems, and how they could be used to improve existing technologies. This paper derives the dynamics of a particular gyroscope influenced pendulum, and shows a simple way to design a controller that stabilizes the pendulum. With the theory and background in place, experimental results are presented to verify the predicted response and validate the control approach. Finally, this paper will evaluate some of the strengths and weakness of this control approach, compared to other balancing techniques.
Thermoelectric Effects of Size of Microchannels on an Internally Cooled Li-Ion Battery Cell
Authors: Mohammadian Shahabeddin K. , Zhang Yuwen
Published: February 2017

Thermoelectric effects of size of microchannels on an internally cooled Li-ion battery cell is investigated in this paper. The liquid electrolyte was flowed as the coolant through rectangular microchannels embedded in the positive and negative electrodes. The effects of size of microchannels on the thermal and electrical performances of a Li-ion (Lithium-ion) battery cell were studied by carrying out 3D transient thermal analysis. Six different cases were designed according to the ratio of the width of the microchannels to the width of the cell from 0 to 0.5. The effects of inlet velocity of electrolyte flow, inlet temperature of electrolyte flow, and size of the microchannels were studied on the temperature uniformity inside the battery cell, maximum temperature inside the battery cell, and cell voltage. The results showed that increasing the size of the microchannels enhances the thermal performance of the battery cell; however, it causes slight decrease on the cell voltage (less than 2%). Comparison between the case with width ratio of 0.5 (Case 6) with the case without microchannel (Case 1) showed that this internal cooling method can decrease the maximum temperature of the battery up to 11.22K, 9.36K, and 7.86K for the inlet temperature of electrolyte flow of 288.15K, 298.15K, and 308.15K, respectively. Furthermore, the case with width ratio of 0.5 (Case 6) has up to 77% better temperature uniformity compare with the case with width ratio of 0.1 (Case 2). Increasing the inlet temperature of electrolyte flow enhances the temperature uniformity up to 33% and increases the cell voltage up to 3%, but it keeps the battery on higher temperatures. Furthermore, increasing the inlet velocity of electrolyte flow from 0.01m/s to 0.01m/s enhances the thermal management of the battery cell by decreasing the temperature inside the battery up to 8.09K, 6.75K, and 5.67K for the inlet temperature of electrolyte flow of 288.15K, 298.15K, and 308.15K respectively. Furthermore, it improves the temperature uniformity up to 89% and decreases the voltage less than 1%.
Flow Conditioning Techniques for a Bent Pipe in a Constrained Latent Heat Storage System
Authors: Moloney Francesca , Wickramaratne Chatura , Almatrafi Eydhah , Goswami D. Y. , Stefanakos Elias , Guldiken Rasim
Published: February 2017

This study was conducted to improve the flow distribution of air after a single 90-degree bend for temperatures above ambient conditions. In the literature, no study has been performed in the literature testing a flow conditioner for heated compressible flow. This study used an existing Thermal Energy Storage (TES) system for flowrates above 100 m3/h with Reynolds numbers over 10,000 was used. Due to a single 90-degree bend in the inlet flow a distance of three diameters from the entrance to the tank, the flow distribution was considerably shifted to the side of the outer bend. The constrained systemwas tested with various flow conditioners with fluid temperatures between the ambient temperature and 60°C. The Spearman and the Mitsubishi Heavy Industries (MHI) plates were the most effective at improving the flow under all tested conditions. The system was modeled for different flow conditioners and validated using a computational fluid dynamic (CFD) model.
Taguchi Experimental Design in Carbon Nanomaterials Synthesis
Authors: Contreras-Navarrete José de Jesús , Granados-Martínez Francisco Gabriel , Durán-Navarro Alejandro , Domratcheva-Lvova Lada , Flores-Ramírez Nelly , Gutiérrez-García Carmen Judith , Aguilar-García Omar , Mondragón Sánchez María de Lourdes
Published: February 2017

Nowadays Carbon Nanomaterials (CNMs) are important in the applied nanoscience development, due to their extraordinary chemical and physical properties. The present research proposes a Taguchi methodology to obtain CNMs with high carbon concentration using hexane as carbon source, and stainless steel core as catalysis by Chemical Vapor Deposition (CVD). The Taguchi experimental design identified the optimal variable and level. Flow rate, temperature and time synthesis were studied. Scanning Electronic Microscopy (SEM) depicted different carbon morphologies. Energy Dispersive Spectroscopy (EDS) demonstrated a carbon atomic percentage concentration above 97. Temperature was the most significant variable according to Taguchi analysis.
CFD Analysis and Experimental Investigation of a Heavy Duty D.I. Diesel Engine Exhaust System
Authors: Emara Kareem , Emara Ahmed , Abdel Razek Elsayed
Published: February 2017

Exhaust manifold is one of the most critical components of an internal combustion engines and overall engine performance can be obtained from the proper optimized design of engine inlet and exhaust systems. In this study two exhaust system models with different configuration (the existing as base one and the modified one) are simulated using ANSYS-CFX 15 with the appropriate boundary conditions and fluid properties specified to the system with suitable assumptions. The model is based on solving NAVIERE STOKES and energy equations in conjunction with the standard K-ε turbulence model. The first design is a single pipe receives exhaust gases from all runners and delivers the exhaust gases to turbocharger inlet. But the second design consists of two tubes each of one receives the exhaust gases coming from the three cylinders only. This design makes the intensity of the exhaust pulses of high pressure, which leads to increase the speed of the turbocharger. The uniformity of the flow field and back pressure variations in the two models are discussed in. A decrease in backpressure and increase in velocities are shown using the pressure contour and the velocity contour in the exhaust manifold as well as temperature distribution inside the exhaust manifold system. The best design is also simulated at different engine speed. Finally the modified model with limited back pressure was fabricated and experiments are carried out on a fully instrumented six cylinder in line water cooled heavy duty direct injection diesel engine; (350 hp@2200 rpm and 1400 Nm@1350 rpm).The pressure and temperature are measured at definite points in the exhaust gas manifold. The results obtained by experimental work were compared with the analytic CFD and found to be closely matching with accepted error.
Analysis of the Attitude of a Gyroscope Controlled With Joint Actuation
Authors: Pereira Marcelo , Weber Hans I. , Carrera Danny Hernán Z.
Published: February 2017

This paper presents the study of a 3 degree of freedom gyroscope system. The mechanical structure is composed of a pair of gimbals with low inertia and a non-axisymmetric spinning rotor. By using sequential Euler rotations the system is modeled with Matlab and Simulink and, by using specific initial conditions, the chaotic movement of the gyroscope is animated, firstly with no friction and no actuation. Next, we implement a control actuation between the gimbals that reduces that chaotic movement and stops the gyro at a certain position, trying to minimize the acting on the spinning rotor. Finally, we use the same control under the presence of friction between the gimbals and the rotor. The simulation results are shown and analyzed, by interpreting the movement according to the parameters used, and the conclusions are presented, along with some comments on future work.
Numerical Study on the Effect of Control Elements on Laminar Airflow Over a Flat Plate
Authors: Gartrell Jessica , Law Deify
Published: February 2017

Boundary layer separation over a surface is an important phenomenon that has great implications on the aerodynamic performance of aircraft. The ability to control flow fields to improve performance and reduce drag is also important and driven by potential savings in fuel expenditures or expansion of the flight envelope. Drag reduction may be achieved by preventing or delaying laminar-to-turbulent transition from occurring over the surface or by inducing turbulence to create secondary flow motion that alters the flow field [1]. The present work is to perform CFD simulations in ANSYS FLUENT of flow velocity profiles with and without a single control element in laminar flow ranging from 2 cm/s to 8 cm/s on a 1 meter long flat plate in a two-dimensional (2D) space, respectively. The simulations without the control element on the flat plate were validated with the Blasius solution as well as compared with the flow velocity profiles produced by the control element on the flat plate. Additionally, the effects of multiple control elements on airflow over the flat plate were studied and compared with the cases with and without a control element on the flat plate. Furthermore, the effects of the flat plate’s angle of incidence at 3° on the drag forces of airflow on the flat plate with and without the control element at 2, 4, and 6 cm/s flow velocity will be investigated and compared numerically.
Optimizing Fluid Production From Porous Media: From Hydraulic Fractures to Plant Roots
Authors: Lu Yunhu , Chandrashekar Sriram , Chen Kang Ping
Published: February 2017

This paper discusses the physical mechanisms of enhanced fluid production from thin and slender porous structures such as hydraulic fractures and plant roots. The work shows how the end effect induces a large local pressure gradient in the medium which creates a converging flow pattern that focuses the fluid to the end region. As a result, a nearly singular flux density around the end develops which can promote the flux density distribution along the structure-medium surface, thus enhancing the production rate. For a given porous structure volume, a competition exists between the structure conductivity and the structure penetration length. This leads to an optimal length-to-width ratio for the structure that maximizes the fluid production rate. Optimized fracture and plant root are discussed.
Hygrothermal Degradation of GFRP/HSS Interface in Metal-Polymer Hybrid Structures
Authors: Wang Qian , Sun Lingyu , Li Lijun , Shen Le
Published: February 2017

Polymer-metal hybrid (PMH) by over-molding is a kind of weight reduction technology, in which the interface is formed by injecting liquid polymer directly on the surface of stamped metal and then curing under pressure. This technique takes the advantages of both the high strength and stiffness of metal and the complex geometry formability of polymer, and it is usually applied in structural components for weight reduction compared to all-metal structure. However, the different coefficient of thermal expansion (CTE) or hygroscopicity for polymer and metal in PMH structure may possibly produce additional interface stress and decrease joining strength degradation, and finally lead to local separation or complete fracture under various environmental loads. The present paper will provide an effective numerical method and investigate the influence of temperature and humidity on the onset and growth of crack, as well as the degradation of interface fracture toughness in PMH structures. Additionally analytical analysis provides qualitative guidelines and orientation for numerical method. The crack initiation is studied by the tensile test of a lap joint specimen, and the crack growth is studied by the DCB (Double Cantilever Beam) test and ENF (End Notched Flexure) test and of PMH specimen with an initial crack. It proves that both temperature and humidity has a great influence on interfacial strength, ultra bearing capacity and energy release rates of PMH structures, and their coupling has more influence than a single factor. The interface degradation degree of the GF30/PA66-HSS is lower than that of PA66-HSS under the same hygrothermal environment.
The Effects of Multi-Mesh Tooth Profile Modifications on Planetary Gear Vibration
Authors: Xun Chao , Long Xinhua , Hua Hongxing
Published: February 2017

In this paper, the different effects of tooth profile modifications (TPMs) for the sun-planet and the ring-planet meshes on the first two rotational modes are investigated with the consideration of tooth thickness errors. A nonlinear model with multiple degree of freedoms is built to descript the rotational vibration of the planetary gears. In contrast to the majority of the models in the literature, the variable mesh stiffness, TPM, manufacturing error, and loss of contact in both of the sun-planet and ring-planet meshes are introduced in the analysis. Multiple scale method is used to analyze dynamic response and transmission errors. Numerical integrations are carried to verify the perturbation results and explore the nonlinear phenomena in the planetary gears. The frequency response curves of dynamic transmission error (DTE) obtained for different TPM with different tooth thickness errors are presented. Results indicate the TPM not only affects the amplitude of response but also results into the change of the margin of contact between sun gear and planet gears and the margin of contact between the ring gear and planet gears. In addition, the optimal TPM for the first mode may induce high level vibration on the second or higher order modes. These mean one need to consider the effects of TPM on the response amplitude and the margin of the loss of contact for both rotational modes to get an optimal TPM among the teeth of sun gear, planet gears, and ring gear. This provides guidance for practical design and tolerance standard for the planetary gears.
First Order Perturbation Technique for Squeeze Film Dampers Executing Small Amplitude Circular Centered Orbits With Aero-Engine Application
Authors: Hamzehlouia Sina , Behdinan Kamran
Published: February 2017

This work develops inertial expressions for the lubricant pressure distribution and fluid velocity components for squeeze film dampers (SFDs) executing small amplitude circular centered orbits (CCO), by applying a first order perturbation to the fluid equations. For small amplitude motions of the journal center, it is assumed that the fluid convective inertia terms are negligible relative to the unsteady (temporal) inertia terms. Firstly, a first order perturbation is applied to the pressure and velocity components in the flow equations. Subsequently, the flow equations are solved for the zeroth-order (i.e. non-inertial) velocities and the first-order (i.e. inertial) velocities. The velocity components are incorporated into the flow equations to develop separate expressions for the zeroth-order and the first order pressures. Furthermore, the pressure expressions are numerically solved by applying finite difference approximations to the equations. Finally, a simulation model is developed to determine the lubricant pressure distribution and fluid film reaction forces for different damper operating parameters, including Reynold’s number (i.e. inertia effect), journal eccentricity ratio, and bearing slenderness ratio.
Differences in Predicted Flow-Induced Vibration of Submarine Pipelines Considering Cross-Flow and Inline Oscillations and its Influence in Fatigue-Life
Authors: Dominguez Anthony , Blanco Armando , Casanova Euro , Loaiza Nelson , García Janneth
Published: February 2017

In offshore facilities, the most widely spread way to transport fluids in relatively short distances is through submarine pipelines. These structures are subject to internal and external forces. Nowadays, most of the proposed models to study submarine pipelines subjected to vortex induced vibrations feature a circular cylinder, submitted to a cross-flow, and are able to display oscillations in just the transverse direction to the fluid flow velocity.

In this paper three different models that consider a two-dimensional fluid flow around a pipeline were studied via ANSYS CFX®, for Reynolds numbers between 100 and 700, with the purpose of determining the limitations of the 1-DOF models based on the Strouhal number and lift and drag coefficients and account its influence in fatigue lifespan. These models consisted of a static cylinder — i.e. no oscillations —, a cylinder with 1-DOF — i.e. cross-flow oscillations — and a cylinder with 2-DOF — i.e. cross-flow and inline oscillations —.

It was found that, although fluid flow Reynolds numbers were very small as to make the submarine pipeline models fall within the finite-life region, a 1-DOF model is accurate enough to predict fatigue lifespan, since it presents respect to the 2-DOF model little deviation in the chosen comparison parameters.
Three Dimensional Numerical Simulation of Particle Deposition in Cold Gas Dynamic Spray Process
Authors: Jen Tien-Chien , Pan Yen-Ting , Zhu Lin , Chen Qinghua
Published: February 2017

Cold gas dynamics spraying (CGDS) is a process employing aerodynamics particle acceleration and high-speed impact dynamics surface-coating technology. The main advantages of CGDS include : (1) A low level of residual stresses; (2) CGDS can collect and reuse the undeposited particle more efficient than thermal spray processes; (3) Coatings can be deposited on materials that are temperature-sensitive; (4) Thick coatings can be produced to allow for free-standing structures or for rapid prototyping; (5) CGDS is safer because it is operated in low temperatures and low noise levels (6) Easy implementation due to its simplicity of technical design; (7). CGDS could produce high thermal and electrical conductivity of coatings.

In the CGDS process, a high-pressure gas stream (generally 20–30 atm) carries metal particles (usually 1–50 μm in diameter) through a DeLaval type nozzle to reach a supersonic velocity before impact on the substrate. Typically, the impact velocities in the CGDS process range from 300 to 1200 m/s. When the particle exceeds the minimum deposition speed, adiabatic shear instabilities occur. This minimum deposition speed is also called critical velocity. In this paper, single particle impact simulations were performed to investigate the critical velocities of different particle sizes on the bonding process. This paper presents a three-dimensional numerical analysis of the particle critical velocity on the bonding efficiency in Cold Gas Dynamic Spray (CGDS) process by using ABAQUS/CAE 6.9-EF1. The particle impact temperature in CGDS is one of the most important factors that can determine the properties of the bonding strength to the substrate. In the CGDS process, bonding occurs when the impact velocity of particles exceed a critical velocity, which can reach minimum interface temperature of 60% of melting temperature in °C. The critical velocity depends not only on the particle size, but also the particle material. Therefore, critical velocity should have a strong effect on the coating quality. In the present numerical analysis, impact velocities were increased in steps of 100 m/s from the lowest simulated impact velocity of 300 m/s. This study illustrates the substrate deformations and the transient impact temperature distribution between particle(s) and substrate. In this paper, an explicit numerical scheme was used to investigate the critical velocity of different sizes of particle during the bonding process. Finally, the computed results are compared with the experimental data. Copper particles (Cu) and Aluminum substrate (Al) were chosen as the materials of simulation.
Optimization on High Adhesive Ability of Lunar Rover Wheel Based on Discrete Element Method
Authors: Zhang Kailiang , Hou Xuyan , Xue Pingping , Zhang Kaidi , Liang Ping , Deng Zongquan
Published: February 2017

The acquirement of lunar soil samples is the foundation to analyze and know about the composition of lunar soil and the lunar geologic structure. Because of the restrictions of the sampling method, the size of driller, the drilling pressure and the driller’s output power, the traditional digging method and vertical drilling method can only acquire the samples from lunar surface to 3 meters deep. In order to acquire the deeper samples based on the existing technique methods, a new exploration concept in which a driller fixed on the rover takes a horizontal drilling and sampling at the cross section of a crater after cleaning the surface chaotic soil was proposed in this paper. When drilling horizontally, the maximum drilling pressure is limited by the low adhesive ability between wheels and soil. For the purpose of making sure enough drilling pressure, study was carried out in this paper to improve the wheel’s adhesive ability by modifying the wheel’s surface. A wheel with a new kind of micro convex structures was proved to be more adhesive and stable during horizontal drilling by comparing with the existing wheel structures, such as wheel with thorns or discontinuous rims. The structural parameters of the convex structures may have significant influences on the adhesive ability. In order to study the effects of the convex structure’s parameters on wheel’s adhesive ability, the motion process of wheels on sandy road was simulated by using a DEM software EDEM. According to the simulation results, when the structural parameters of the convex structures are: flat-end shape, length/diameter = 5 and distribution density = 81/mm2, the wheel’s adhesive ability is much better than the wheel with other parameters based on a criterion which is the ratio of the tangential force to the normal force in the tangential motion process. Besides, the friction coefficient of wheels with convex structures is about 5 times as much as the friction coefficient of normal wheels, which proves that it is a useful method to improve wheel’s adhesive ability by modifying wheel’s surface with the convex structures.
Effects of Kurtosis Value on the Response of Vibrating Beam With Different Boundary Conditions
Authors: Hoursan Hesam , Ahmadian Mohammad Taghi
Published: February 2017

Effect of signal kurtosis value on the response of the beam with different boundary conditions has been studied. The signals with various Kurtosis have been generated in a Signal generator code- combined with an algorithm for random data generation for various kurtosis values. Subsequently, a simple Finite Element model of a rectangular Euler-bernoulli beam is introduced and the PSD1s are applied to the model in the form of low frequency base excitation acceleration input. The results show that, generally, the signals with higher kurtosis tend to create more stress and deformation in the structure due to the more frequent existence of peaks with higher amplitudes. However, at lower kurtosis values near normal distribution, the response behavior is different. Also, the stress induced in the beam end is the most critical in clamped-clamped conditions, and where both ends are excited.
The Effect of Interfacial Microstructures on Joining Strength of Polymer-Metal Hybrid Interface
Authors: Shen Le , Sun Lingyu , Li Lijun , Huang Bincheng , Ye Xiao
Published: February 2017

The high strength steel (HSS) material has high stiffness and strength, which is usually applied in load-bearing structures, but its density is also high. Although the glass fiber-reinforced polymer material has low density and excellent designability, they couldn’t be used as a structural element solely due to their low absolute stiffness and strength. Polymer Metal Hybrid (PMH) structure combines polymer with metal and take the advantages of both materials, that could achieve both the light weight and excellent mechanical properties. The main problem of this technology is that the connection strength of the two materials is possibly insufficient.

This paper takes the polypropylene/HSS hybrid structure as an example, and studies the influence of interface microstructure on the bonding strength. Four kinds of micro-scale interfacial geometry, the smooth plane, the triangular serrated, the rectangular serrated and the mechanical interlocking, were modeled and compared with each other. Under the bending, tension and shear loads, respectively, the bonding strength were studied using analytical method and finite element simulation. It is found that the microstructure geometry has important effect on bonding strength. When the ratio of polymer modulus to HSS modulus rises, the interfacial strength and ultra load-bearing capability increase. The optimal interfacial microstructure for different loading type will be suggested, which is very useful to the design of PMH structures.
Numerical Analysis of Blockage Ratio Effect on a Portable Hydrokinetic Turbine
Authors: Daskiran Cosan , Riglin Jacob , Oztekin Alparslan
Published: February 2017

Three-dimensional steady state Computational Fluid Dynamics (CFD) analyses were performed for a pre-designed micro-hydrokinetic turbine to investigate the blockage ratio effect on turbine performance. Simulations were conducted using a physical turbine rotor geometry rather than low fidelity, simplified actuator disk or actuator lines. The two-equation k-ω Shear Stress Transport (SST) turbulence model was employed to predict turbulence in the flow field. The turbine performance at the best efficiency point was studied for blockage ratios of 0.49, 0.70 and 0.98 for three different free stream velocities of 2.0 m/s, 2.25 m/s and 2.5 m/s. Distinct blockage ratio results at a free stream velocity of 2.25 were compared to a previous numerical study incorporating the same rotor geometry within an infinite flowing medium. The pressure gradient between turbine upstream and turbine downstream for blocked channel flows elevated the turbine performance. The increment in blockage ratio from 0.03 to 0.98 enhanced power coefficient from 0.437 to 2.254 and increased power generation from 0.56 kW to 2.86 kW for the present study.
Viscosity Prediction of Water-Based Silver Nanofluid Using Equilibrium Molecular Dynamics
Authors: Ma Qianli , Fang Haisheng
Published: February 2017

Nanofluids containing silver (Ag) nanoparticles have been used in three dimensional ink-jet printing (3DP) in recent years. Rheological properties of the nanofluids, for example, viscosity, play significant roles during the application. In this paper, viscosity of Ag-water nanofluid has been predicted using the equilibrium molecular dynamics method. The influencing factors of the viscosity, including temperature, nanoparticle size, nanoparticle concentration and nanoparticle aggregation, have been investigated. By screening the existing water models, TIP4P/2005 model is found the most suitable for viscosity calculation under the temperature range. The weight fraction of the nanoparticles, which proves more appropriate, is used during the study of the concentration effect instead of volume fraction. The results show that the viscosity of the nanofluid goes up by decreasing temperature or increasing nanoparticle concentration. Furthermore, as the nanoparticles get smaller, or aggregate, the viscosity increases slightly.
Influence of Species Transport and Inlet Condition on the MOCVD-Grown GaN Uniformity
Authors: Zhang Zhi , Fang Haisheng , Zheng Jiang , Yan Han , Gan Zhiyin
Published: February 2017

A three-dimensional model focusing on fluid flow, heat transfer, species transport and chemical reaction is investigated in a commercial metal-organic chemical vapor deposition (MOCVD) reactor. The key reaction pre-exponential factor is improved to yield more reasonable results matching the experiment data. The growth rate and growth uniformity are carefully investigated with the premixed and non-premixed inlets, as well as with the various temperatures, flow rates and V:III ratios. The susceptor of the reactor is divided into Zone A, Zone B and Zone C according to the heater alignment. The results reveal that the premixed inlet leads to a more uniform growth rate than the non-premixed inlet does. Temperature change of the inlet gas has a negligible influence on the growth rate and uniformity. A larger flow rate and/or lower V:III ratio result in increase of the growth rate and uniformity. However, growth uniformity of the particular zones shows different variable-dependent tendency. The conclusions can be instructive for high-efficiency and better-quality manufacture in industry production with a balance between the growth rate and the growth uniformity.
Path Tracking Experimentation With Epi.q-Mod 2: An Obstacle Climbing Mobile Robot
Authors: Quaglia Giuseppe , Nisi Matteo , Bruzzone Luca , Fanghella Pietro
Published: February 2017

In this paper, an experimental activity on the path tracking for a hybrid wheeled-legged mobile robot is presented. The activity has been conducted on the Epi.q-Mod 2 prototype, a mobile robot with obstacle climbing ability. This feature has been obtained using a smart rotating leg architecture. Unfortunately, this solution introduces complexity on the kinematic and dynamic modeling of the robot. In order to understand the behavior of the robot during the motion on a generic trajectory, an open loop position controller has been implemented. In particular, the experimental robot trajectory has been reconstructed from odometric quantities through a simplified kinematic model. This trajectory has been compared with the trajectory obtained from a multibody model of the real prototype in order to evaluate the differences between the two approaches. This activity represents a preliminary step for the development of a self-guidance vehicle. In future works the developed model will be used to provide a position feedback for a closed loop position controller without the necessity to use additional sensors.