bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Investigation of High Speed Combustion and its Impact on Thermal Structure
Authors: Zhang Litao , Zheng Lili , Hou Lingyun
Published: March 2015

This paper presents numerical study of high-speed combustion and its relationship with thermal stress distribution on a cavity combustion chamber. First, a physical model is established to describe high speed compressible turbulent reacting flow as well as thermal transport in combustor structure. It is then applied to a model combustor with two-staged fuel injections to examine the effects of fuel flow rate and inflow conditions on the heat flux intensity and thermal stress distributions across the thickness of the combustor wall. The result shows that the injection method of the first stage has a great influence on the flow field near the second one, and it affects combustion and heat release distribution inside the combustor. The intensity of heat flux passing through the combustor wall changes along the downstream of the flow, and large thermal stresses are generated in the vicinity of the injector, the leading edge and the trailing edge of the cavity.
Particulates Depositions in Patient-Specific Simulations of Respiratory System
Authors: Taherian Shahab , Rahai Hamid , Gomez Bernardo Z. , Waddington Thomas
Published: March 2015

Ambient particulates depositions have major impacts on respiratory functions. Patient-specific simulations of the respiratory system of a patient were performed to investigate the relationship between the flow characteristics and particulate depositions in the upper respiratory domain. CT scan images were imported to create a 3D model of the bronchial tree and then transferred to a computational fluid dynamics (CFD) software for simulation. Appropriate boundary conditions were assigned to simulate the sinusoidal behavior of the normal breathing cycle with the corresponding pressures at the outlets. Lagrangian phase model was used to simulate the micron solid round particulates transport and depositions. The simulations were performed for 2.5 micron and 10 micron particles. The implicit-unsteady Reynolds Averaged Navier-Stokes equations with K-ω turbulence model were used for these simulations. Results indicate high correlation between regions of high vortices, secondary flow and high wall shear stress and particulate depositions. The total deposition number for 10-micron particles was higher than that for the 2.5-micron particles. The differences in the locations of depositions at various generations of the lung illustrate the importance of the patient-specific simulations.
A FEA Simulation Model for Thin-Walled C-Section Composite Beam Assembling With R-Angle Deviation
Authors: Wang Hua , Si Suo
Published: March 2015

There are unavoidable deviations, such as shrinkage and distortions, in the composite detail parts production due to the complexity of composites fabrication. Interests in the assembly analysis of composite beams have led to a need for more accurate analysis especially in the case of fabrication deviations. This work proposes a numerical finite element model of thin-walled C-section composite beam with R-angle deviation for assembling. The rule of Hashin failure combined with cohesive element is applied to study the mechanical performance of the fiber and matrix (implemented as user subroutine UMAT in ABAQUS) while positioning and clamping. Tension and compression tests are carried out based on available standards to determine the C-section beam behavior under load. The testing data validates the proposed numerical model. The numerical model captures the experimentally obtained results with minimal error, and predicts the failure modes successfully. The proposed model allows to determine accurately the first failure location and the associated load level. It will enhance the understanding of the composite components pre-loading analysis, and help systematically improving the composites assembling efficiency in civil aircraft industry.
Orthogonal Turning of Aluminum 6061 in Liquid Nitrogen Cutting Environment
Authors: Chandrasekaran Vishnu Vardhan , Payton Lewis N. , Hunko Wesley Scott
Published: March 2015

Liquid nitrogen is studied as an alternative metal working fluid during the machining of Aluminum 6061-T6 alloy using two different tool materials (HSS and an uncoated carbide). The design of the experiment utilized two feeds (0.002”/rev and 0.004”/rev) with a constant depth of cut (0.125 inch) and 3 different tool rake angles of 0°, 7° and 15°. Force data was collected using Kistler dynometer. Three-dimensional (3D) measurements of the tool wear were analyzed using a 3D Keyence optical microscope in conjunction with a Dektak surface profilometer. When contrasted with dry cutting (hard turning), it was found that the liquid nitrogen increased the tool wear with HSS tools but decreased tool wear using uncoated carbide tools. Effect on cutting forces in all cases was statistically insignificant.
Vibration Modelling of String-Harnessed Beam Structures Using Homogenization Techniques
Authors: Martin Blake , Salehian Armaghan
Published: March 2015

Harnessing structural elements with strings, power cables, and signal cables increases the complexity in modelling the dynamic behaviour of such structures. Developing models capable of accurately predicting the dynamic behaviour of these systems is of great importance for space structures that cannot be tested prior to launch. The focus of this work is obtaining an equivalent continuum model for string-harnessed beam-like structures with periodic wrapping patterns. The tension in the string is assumed to vary as the beam deflects. The displacement field with second-order terms is determined and from which the Green-Lagrange strain tensor is obtained. After finding kinetic and potential energy expressions Hamilton’s principle is used to obtain the partial differential equation and boundary conditions. Numerical results for the shift in the natural frequencies are presented for various string properties to investigate their effects on the structure.
Comparison of Adaptive and Robust Controllers for Fully-Constrained and Redundant Planar Cable Robots
Authors: Torres-Mendez Sergio J. , Gungor Gokhan , Fidan Baris , Khajepour Amir
Published: March 2015

This work deals with the design and comparison of two adaptive position control schemes with a classical PID controller for fully constrained and redundant planar robots. First, a novel method based on inclusion of virtual cables facilitates the linear separation of the uncertain parameters from the input-output signals. Then, two Lyapunov based adaptive controllers based on the sliding mode and PD schemes are designed to compensate for the structure matrix uncertainties, which result from errors in the anchor point locations. Finally, the adaptive controllers are evaluated and compared with a classical PID controller through simulations for a desired 2D singularity-free pose of the mobile platform. The simulation results have shown that the adaptive PD control scheme has the best performance for both fully constrained and redundant cases.
Vibration of a Functionally Graded Timoshenko Beam on an Elastic Foundation due to a Moving Mass
Authors: Teimoori Khashayar , Sadegh Ali M.
Published: March 2015

In the past decade, beams that are made of functionally graded materials (FGM) have been employed in many engineering and biomedical application fields. In this paper, dynamic response of a FGM Timoshenko beam that is supported by an elastic foundation and is subjected to a moving mass, i.e., the effects of boundary flexibility, has been investigated. It is assumed that the material properties of the beam will change only in the thickness direction. The governing equations of motion are derived using Hamilton’s principles. The partial governing differential equations of motion are reduced to a set of ordinary differential equations by using Petrov-Galerkin method. Runge-Kutta numerical scheme is employed to solve the obtained set of ordinary differential equations. After verification of the results for some special cases with known sloutions the effect of various parameters such as the velocity of moving loads, the boundary flexibility, the power-law index on the vibration of the beam have been investigated. The special case of the solution of the problem was compared with the study of Mesut Simsek [2010] and H. P. Lee [1998] which showed excellent agreement. The results have also been compared to the similar beam without FGM and the advantages of FGM have been discussed.
Dynamic Modelling of Horizontal Shafts With Annular Surface Contact and Friction: Application to Oilwell Drilling
Authors: Sarker Md. Mejbahul , Rideout D. Geoff , Butt Stephen D.
Published: March 2015

Lateral whirl vibrations in long sections of horizontal oilwell drillstrings, which are essentially enclosed shafts lying on the low side of the wellbore, are potentially destructive to the bit, pipes and downhole tools. Forward or backward whirl can lead to impact with the borehole, and stick slip and bit bounce can cause tool joint failure, twist-off, and bit damage. A complete deviated drillstring has been modelled by having decoupled axial and torsional segments for the vertical and curved portions, and nonlinear three-dimensional multibody segments with lateral vibration in the final horizontal section ending at the bit. The model can predict how axial and torsional bit-rock reactions are propagated to the surface, and the role that lateral vibration near the bit plays in exciting those vibrations and stressing components in the bottom-hole-assembly. The proposed model includes the mutual dependence of these vibrations, which arises due to bit-rock interaction and friction dynamics between the drillstring and wellbore wall.
Stochastic Modeling of Crevice Corrosion With Emphasis on Titanium Alloys Modular Total Joint Arthroplasty
Authors: Rajput Sandeep , Paliwal Manish
Published: March 2015

Titanium alloy (Ti6Al4V (ASTM F-136)) is typically used for modular hip implant stems. This highly corrosion resistant alloy forms passive surface oxide films spontaneously. However, with modular designs, micro-motion may occur at the taper junctions during mechanical loading.

Complex physical/chemical reactions take place which may result in pitting and crevice corrosion. Crevices between the taper junctions may allow the body fluids to enter and remain stagnant. These conditions make the modular tapers susceptible to fatigue and mechanically assisted crevice corrosion. When two or more surfaces are in close proximity, it leads to the creation of a locally blocked region in which enhanced dissolution may occur. The in vivo degradation of metal alloy implants compromises the structural integrity.

Stochastic modeling of crevice corrosion is performed based on the mechanism behind the phenomenon. Sensitivity analysis is performed, and conclusions drawn.
Influence of Bearing Configuration on Spindle Modal Characteristics
Authors: Hong Jun , Liu Guanghui , Li Xiaohu , Wu Wenwu , Wan Shaoke , Ma Shaohang , Wang Dongfeng
Published: March 2015

Since bearing configuration has significant influence on the spindle modal characteristics which can reflect the dynamic performance of spindle system in machine tools, so it would be of extraordinary importance and necessity to analyze the spindle modal characteristics through simulation and experiment when it comes to designing spindle system. In this paper, the number and span of bearings, the spacer of bearing set and the overhang of spindle are considered as the main designing parameters of the spindle system. Firstly, a coupled spindle-bearing model is established considering the radial deformation of the bearing inner ring caused by interference fits of spindle assembly, as well as the centrifugal and thermal deformations. Based on the model, the modal characteristics of different bearing configurations are analyzed. Secondly, a spindle test bench is designed and constructed. Finally, modal characteristics of the spindle system are tested with different bearing configurations. From the simulation and experimental results, it’s indicated that there is a correlation between the natural frequency and the number of bearings. The using of short spacer inside the bearing set can increase spindle natural frequency slightly. Besides, the first natural frequency of the spindle system rises with the bearing span, whereas the second one tends to decrease. And shortening the overhang of spindle can also increase its natural frequencies, which can be taken into account in spindle design.
Multidisciplinary Optimization Technology Research on Typical Turbine Assembly Structure
Authors: Liao Huming , Fan Jiang , Wang Rongqiao , Shen Xiuli , Hu Dianyin
Published: March 2015

A multidisciplinary design optimization (MDO) method for turbine mortise assembly structure is presented. This method takes tenon and mortise as a whole to carry on the design optimization. With the adoption of Design of Experiment (DOE) method and Collaborative Optimization (CO) Strategy, this method has realized the coupling parallel optimization of the mortise assembly structure. To verify the effectiveness of the proposed method a typical fir-tree mortise structure design optimization is provided as an example. The results show that the mass and Von Mises Stress of the mortise assembly structure were reduced remarkably, which means that the proposed method has a significant role in enhancing structural performance.
Design of Plate Surface Displacement Sensors
Authors: Eaton Jonathon , Zahui Marcellin
Published: March 2015

The present work uses PolyVinyliDene Fluoride (PVDF) film to develop surface displacement sensors for vibrating plates with various boundary conditions. Two constant shape PVDF films are bonded together and to the surface of the plate covering the entire plate. The films are arranged such that the piezoelectric axis 1 of the top film is perpendicular to the piezoelectric axis 2 of the bottom axis. Right angle quadrilaterals patches are etched on the films to create multiple separate sections of the sensors. The output charges of sensor patches covering the same subarea are processed to compute the slopes of the lateral displacement surface of that subarea. The actual plate lateral displacement elevations are calculated from these slopes using forward difference equations. Theoretical analysis and numerical verification show that the proposed sensor can be used to effectively measure the lateral vibration displacements of plates with various boundary conditions. However the accuracy of the measurement is closely related to the number of sensor sections and thus, relatively large number of channels is required for accurate measurements. Furthermore, for non-zero slop conditions at the boundaries, additional point sensors are required.
Non-Invasive Displacement Measurement of Lightweight Structures Under Dynamic Excitations
Authors: Kotek Lubos , Holub Michal , Vetiska Jan , Hadas Zdenek , Blecha Petr
Published: March 2015

The present article deals with the processing of data obtained by non-invasive measurement methods of instantaneous displacement of lightweight structures. This data is necessary to evaluate tuning-up of characteristics of an electro-magnetic vibration energy harvester, which is used for energy harvesting from these ambient mechanical vibrations. The electro-magnetic vibration energy harvester is device for powering of low power consumption wireless sensors without any external source of energy. The primary source of energy is only mechanical vibrations in place of wireless sensor and the operation without primary batteries is required. These techniques of wireless measurement are commonly used in aeronautics applications. The knowledge of mechanical vibrations in place of wireless sensors with vibration energy harvester is used for development of vibration energy harvester design.

The major idea is to verify the use of non-invasive measurement using high-speed cameras with measurement obtained from the laser interferometer. The measurement using high-speed camera can provide very important information about resonance operation of the vibration energy harvester during the future development.
Adaptive Control of Electrically-Driven Robot Manipulators Without Velocity/Current Measurements
Authors: Homayounzade Mohamadreza , Keshmiri Mehdi , Keshmiri Mohammad
Published: March 2015

An adaptive output feedback controller for electrically-driven robot manipulators is developed in this paper. The proposed controller can compensate for parametric uncertainties while only requiring link position measurements. To eliminate the need for measuring link velocity and electrical winding current, two individual observers are used as a surrogate for unmeasurable quantities: one for joint velocity estimation, and another for motor current estimation. Based on these observers, a modified adaptive integrator backstepping procedure is utilized to design input voltage which guarantees semiglobal asymptotic link position/velocity tracking in spite of the mechanical parametric uncertainties and lack of link velocity and rotor current measurements. The main novelty of our presented work lies in simultaneous estimation of joint velocities, rotor currents, and mechanical uncertainties to produce a controller which provides a system level input, the voltage to an electric actuator, to control the link position/velocity of electrically-driven robot manipulators.
A Hybrid Flexoelectric-Piezoelectric Design for Structural Sensing
Authors: Hu S. D. , Li H.
Published: March 2015

Distributed sensing using piezoelectric sensors have been widely studied on shell-type structures. Usually, sensing signals by piezoelectric sensors are contributed by both membrane and bending strains which are always closely coupled so that either of them is not easy to be extracted from the physical output signal. Based on the direct flexoelectric effect, flexoelectric materials are promising transducers with capability of monitoring the structural vibration especially the bending behavior. In this study, a hybrid flexoelectric-piezoelectric configuration based on a cylindrical shell is proposed to separately monitor its membrane and bending behaviors. A five-layer composite cylindrical shell is established. A piezoelectric layer is embedded in the neutral surface of the shell and flexoelectric layers are laminated on the inner and outer surfaces. The piezoelectric layer and the flexoelectric layers are segmented into a number of patches serving as distributed sensors. Results show that for piezoelectric sensors, only the membrane strain component is detected while the flexoelectric sensing signals are only contributed by the bending strain component. In order to further obtain signal information respectively indicating the longitudinal and the circumferential bending strains, an orthogonal lamination scheme of flexoelectric layers was proposed. Signal modulate circuits with different flexoelectric material constants were also designed in order to directly achieve on-line monitoring. Spatial distributions of hybrid flexoelectric-piezoelectric sensing signals were evaluated and analyzed in case studies. Results show that by implementing the orthogonal lamination scheme, the flexoelectric sensors can individually predict the longitudinal and circumferential bending behaviors. Such a hybrid configuration is also applicable to other structures.
Wearable Wireless Inertial Sensors for Estimation of Gait Parameters and its Integration With Portable Harness Ambulatory System for Rehabilitation
Authors: Kumar Neelesh , Haghani Sasan , Shetty Devdas
Published: March 2015

There is a growing demand for quantifying the performance and efficacy of rehabilitation programs. Researchers are advocating home based rehabilitation devices and continuous monitoring of patients status in real time through wearable sensors. This paper investigates the use of inertial measurement sensors for recording the dynamic gait status. In order to facilitate long term recording and minimal interface of recording devices, these MEMS sensors are advantageous in many ways over the conventional laboratory methods. Portable Harness Ambulatory System (PHAS) can be effectively used in home environments with minimal assistance for gait rehabilitation. This paper addresses the stages of mechatronic integration of a prototype of PHAS with an aim for early gait rehabilitation of elderly and stroke survivors without fear of falling. Sensors modules comprised of accelerometer and gyroscope were developed. X-bee wireless communication protocol is used for transmitting the gait data for computer storage. Gait experiments with wireless sensor modules attached to shoulder, wrist, thigh and ankle joints of normal human subjects were conducted for slow and fast walking speed. The inertial measurement sensors provide information on the range of motion, gait speed, and orientation. Experimental results prove that sensor modules were successfully able to acquire and record the gait information wirelessly. These sensor modules can also be integrated in the PHAS prototype. The paper outlines the results of initial research and discusses possible alternatives.
Time History Steam Hammer Analysis for Critical Hot Lines in Thermal Power Plants
Authors: Bayoumy Ahmed H. , Papadopoulos Anestis
Published: March 2015

Pressure surges and fluid transients, such as steam and water hammer, are events that can occur unexpectedly in operating power plants causing significant damages. When these transients occur the power plant can be out of service for long time, until the root cause is found and the appropriate solution is implemented. In searching for root cause of transients, engineers must investigate in depth the fluid conditions in the pipe line and the mechanism that initiated the transients. The steam hammer normally occurs when one or more valves suddenly close or open. In a power plant, the steam hammer could be an inevitable phenomenon during turbine trip, since valves (e.g., main steam valves) must be closed very quickly to protect the turbine from further damage. When a valve suddenly stops at a very short time, the flow pressure builds up at the valve, starting to create pressure waves along the pipe runs which travel between elbows. Furthermore, these pressure waves may cause large dynamic response on the pipeline and large loads on the pipe restraints. The response and vibrations on the pipeline depend on the pressure waves amplitudes, frequencies, the natural frequencies and the dynamic characteristics of the pipeline itself. The piping flexibility or rigidity of the pipe line, determine how the pipes will respond to these waves and the magnitude of loads on the pipe supports. Consequently, the design of the piping system must consider the pipeline response to the steam hammer loads. In this paper, a design and analysis method is proposed to analyze the steam hammer in the critical hot lines due to the turbine trip using both PIPENET transient module and CAESAR II programs. The method offered in this paper aims to assist the design engineer in the power plant industry to perform dynamic analysis of the piping system considering the dynamic response of the system using the PIPENET and CAESAR II programs. Furthermore, the dynamic approach is validated with a static method by considering the appropriate dynamic load and transmissibility factors. A case study is analyzed for a typical hot reheat line in a power plant and the results of the transient analysis are validated using the theoretical static approach.
Study on Detection of Epileptic Discharges Based on a Duffing Oscillator Model
Authors: Murakami Takahiro , Ukida Yasumi , Fujii Masami , Suzuki Michiyasu , Saito Takashi
Published: March 2015

In order to establish a quantitative detection method for appearance in epileptic discharges (EDs), we propose using the model parameters in a Duffing oscillator, which is a nonlinear mathematical model. Extracting four frequency bands of delta, theta, alpha and beta waves from the time history of the electrocorticogram (ECoG) obtained from rats with induced EDs, we applied a sweep window to the time history for each band. So as to fit the equation for the Duffing oscillator to the time history of the ECoG, we used the least square method to determine the model parameters expressing characteristics of ECoG. The Duffing oscillator has three kinds of vibrational parameters and four kinds of parameters about the amplitude for the driving force with two predominant frequencies contained in ECoG. In order to examine the appearance time of the EDs and the change of ECoG characteristics, we determined the model parameters for each sweep window. When epilepsy occurs, we found that the amount of the parameters related to “conservation”, “dissipation” and “input quantities” increases. On the other hand, the parameter value corresponding to nonlinearity tends to decrease. It is found that the proposed method by the model parameters of the Duffing oscillator can be used in quantitative detection for EDs.
Design of a Boat Simulator Using Two Parallel Manipulators
Authors: López Juan David , Rodríguez Carlos Francisco
Published: March 2015

In this paper a boat simulator is designed using parallel manipulators. The simulator allows the training of five or seven people in a river environment. Due to the high payload and high inertial forces, it was proposed to divide the simulator into various synchronized platforms. Additionally different configurations of mechanisms were evaluated as well as linear or rotational actuation. The dimensional synthesis was performed by introducing a power index based on the Virtual Work equations of motion, and applying Genetic Algorithms for optimization. This design process results in using two coordinated manipulators with rotational actuators. The first one has two degrees of freedom (pitch and roll); it will simulate the motion of the boat’s stern. The second one has three degrees of freedom: pitch, roll and heave; and simulates the motion of the boat’s bow. The detail design was concluded and the manipulators were built. A real time controller is under design nowdays and the integration of the fluid and the boat dynamics into the inverse dynamics analysis of the manipulators is proposed as future work.
Hybrid Optimal Power Management of a Ship
Authors: Meyer Richard T. , DeCarlo Raymond A. , Pekarek Steve D. , Sun Jing , Park Hyeongjun
Published: March 2015

Power management of a ship’s electrical system has become important due to increasing loads from manpower-reducing automation, greater power requirements of advanced weapons and sensors, introduction of all electric propulsion, and the increasing cost of oil-based fossil fuels. A coordinated power management strategy of the ship’s electric power grid is desired to optimally allocate power flows and minimize fuel consumption. This paper develops such an optimal power management system for an interconnected, supervisory-level ship power system model based upon a ship power system test bed developed for the Office of Naval Research. The ship power system consists of two electrical generators, one rated at 59 kW to represent a gas turbine engine-generator pair and the other rated at 11 kW to represent a diesel generator, an 8 kW pulsed power load that represents the discharge and charge of a capacitor bank for an electromagnetic railgun system, and 37 kW ship propulsion system comprised of an induction motor coupled to the propeller shaft. The ship propulsion system’s induction motor has switched operation with two modes of operation, propelling and generating; the latter mode means that excess kinetic energy during ship slowing can be used to charge the capacitor bank for loads such as pulsed power loads. Given the switched system model, the paper sets forth a hybrid model predictive control strategy based on a minimization of a performance index that trades off fuel consumption, velocity tracking error, and electrical bus voltage error. The optimization is performed using a relaxed representation of the control problem (termed the embedding method) and collocation for discretization with traditional numerical programming to compute the mode and continuous control inputs. The methodology avoids the computational complexity associated with alternative approaches, e.g., mixed-integer programming. Numerical optimization is performed with MATLAB’s sqpLineSearch. To demonstrate the power management approach, a scenario is simulated where the ship is to follow a changing desired velocity while simultaneously maintaining the bus voltage at a desired value, keeping the 11 kW generator at a fuel efficient operating point, and minimizing the fuel use of the 59 kW generator.
Accuracy of Surface Point Detection With an 850nm Laser and NDI Stereo Camera
Authors: Goerlach Franziska S. , Lueddemann Tobias , Pfeiffer Jonas , Lueth Tim C.
Published: March 2015

The use of three-dimensional scanning techniques in the medical field has become increasingly relevant. Laser projection systems have been applied onto human skin tissue in a variety of ways, especially in navigated surgery. However, a highly accurate and portable scanning system with the ability to analyze human tissue from multiple recording directions has yet to be developed and certified as a Class I medical device. This project aims to find the ideal setup of a portable, intuitive and certified scanning system of human tissue without the need of projective equipment. The scanning tool consists of a stereo camera by Northern Digital Instruments (NDI) and an infrared laser module. This paper presents the system’s ideal parameter settings while varying its accuracy when applying a laser module with wavelength of 850nm onto human tissue.
Geometry Assurance Integrating Process Variation With Simulation of Spring-In for Composite Parts and Assemblies
Authors: Jareteg Cornelia , Wärmefjord Kristina , Cromvik Christoffer , Söderberg Rikard , Lindkvist Lars , Carlson Johan , Larsson Stig , Edelvik Fredrik
Published: March 2015

Geometrical variation and deviation in all manufacturing processes affect quality of the final product. Therefore geometry assurance is an important tool in the design phase of a new product. In the automotive and aviation industries where the use of composite parts is increasing drastically, new tools within variation simulations are needed.

Composite parts tend to deviate more from nominal specification compared to metal parts. Methods to simulate the manufacturing process of composites have been developed before. In this paper we present how to combine the process variation simulation of composites with traditional variation simulations.

The proposed method is demonstrated on a real complex subassembly, representing part of an aircraft wing-box. Since traditional variation simulation methods are not able to capture the spring-in and the special deviation behavior of composites, the proposed method adds a new feature and reliability to the geometry assurance process of composite assemblies.
Dynamics of Bladed Disks With Frictional Coupling and Alternate Mistuning Pattern
Authors: Tatzko Sebastian , von-Scheidt Lars Panning , Wallaschek Joerg
Published: March 2015

In the field of turbo machinery design frictional coupling has been found to be a low cost method to increase the mechanical damping of bladed disks. Underplatform dampers (UPD’s) are commonly used which are metal devices pressed against the blades by centrifugal forces. The main task is to find the optimum value of the contact normal force to maximize energy dissipation. This optimum strongly depends on the excitation of the structure. Traveling waves are excited by engine order excitation and flutter. Flutter caused by fluid structure interaction can be reduced by intentional mistuning of the bladed disk whereas forced response levels will be typically increased by mistuning. A compromise is alternate mistuning.

The present paper deals with the influence of alternate mistuning on frictional coupling of blisks. Firstly, the dynamics of a tuned blisk are explained with a simplified lumped mass cyclic oscillator model. It is pointed out that eigenfrequencies of traveling waves around the blisk are influenced by structural coupling. Alternate mistuning leads to mode coupling with the possibility of energy transfer. The performance of friction coupling strongly depends on the nodal diameter mode shape of vibration which is stated analytically for pure Coulomb sliding contact. Following this, a simplified blisk model with underplatform dampers is developed to analyze alternate mistuning and frictional coupling. The simulation results show a significant influence of the mistuning on the damping performance.
Towards the Framework for the Design of Human Centric Internet of Things
Authors: Luís-Ferreira Fernando , Ghimire Sudeep , Zdravkovic Milan , Jardim-Goncalves Ricardo
Published: March 2015

The research and development of Internet of Things (IoT) paradigm, encompassing different related concepts and technologies, such as Cyber Physical Systems and Wireless Sensor Networks, is currently facing the challenges related to a lack of possibilities to de-verticalize the market of devices. These challenges were caused by incoherent development of the different standards, models and languages for the devices operations, hence dramatically reducing their capability to interoperate. It is our belief that these challenges can be overcome by the design in which the devices networks are functioning by following the principles of human communication. In this paper, we propose a framework to support Knowledge Management of a human-centric IoT, while considering the different enabling factors in anthropomorphic approach, such as awareness, perceptivity and physiological enrolment. This framework takes into account a new type of data, a sensorial physiological data that is assumed to enrich the expressivity of devices and thus, enable more accurate and complete perception of the signals, transmitted by the devices.
Cycloidal Rotor Propulsion System With Plasma Enhanced Aerodynamics
Authors: Xisto Carlos M. , Páscoa José C. , Leger Jakson A.
Published: March 2015

A cyclorotor consists of a set of blades rotating about an horizontal axis that is parallel to the blade span. The designation of cycloidal rotor is related to the cycloidal path described by the rotating blades during forward flight. In the following paper we study, trough the use of numerical tools, the PECyT (Plasma Enhanced Cycloidal Thruster) system as a way of improving the performance of classical cycloidal rotors. PECyT consists in the introduction of Dielectric Barrier Discharge (DBD) plasma actuators in the CR blades. Such system act as an active flow control that is able to delay the stall onset at high angles of attack, thus increasing the aerodynamic efficiency of each blade.
ROM of Primary Resonance of Electrostatically Actuated MEMS/NEMS Plates
Authors: Caruntu Dumitru I. , Oyervides Reynaldo
Published: March 2015

This paper utilizes Reduced Order Model (ROM) method to investigate the voltage-amplitude response of electrostatically actuated M/NEMS clamped circular plates. Soft AC voltage at frequency near half natural frequency of the plate is used. This results in primary resonance of the system. The effects of nonlinearities of the system including pull-in instability on the voltage-amplitude response are investigated. Namely, the effects of detuning frequency, damping, Casimir force, and van der Waals force on the voltage response of clamped circular plates are reported. Casimir and van der Waals forces are found to have significant effects on the response of clamped circular plates and must be considered to accurately model and predict the behavior of the system.
Effect of Varying Diameter of Dental Implants During Placements in Compromised Bony Ridges at Different Insertion Torques: A Finite Element Study
Authors: Aziz Imran , Khan Waleed A. , Moeen Faisal , Akhtar Imran , Tarar Wasim
Published: March 2015

The life of dental implant depends on various parameters such as insertion torque, implant diameter and cortical and cancellous bones thickness. The thickness of the cortical and cancellous bones varies from patient to patient and for each thickness, the corresponding studies are required to determine the favorable implant loading. In this study, stress analysis on various dental implant fixtures inserted in compromised bony ridges is performed using three dimensional finite element analyses. Initially, the modeling and analysis of previously analyzed structure is done to validate the solution procedure. After successful validation, three dimensional linear elastic analysis of bone implant bone assembly is performed. The implant material is treated as isotropic whereas the bone materials are taken as anisotropic materials. The parametric study finds the effect of insertion torque and variation of implant diameter on stress induced in the compromised bony ridge. Further, the implant bone assembly was analyzed using various cortical bone thicknesses. It has been observed that the increase in torque results in increased stress and deformation in the bone. With increasing bone thickness, the similar variation of torque produces less stress and deformation in dental implants. The study is helpful in prediction of favorable implant loading and implants diameters for compromised bony ridges. The study provides useful knowledge in improving the performance and life of dental implants.
Variable Geometry Dies for Polymer Extrusion
Authors: Giaier Kevin S. , Myszka David H. , Kramer Wesley P. , Murray Andrew P.
Published: March 2015

This paper presents the development of variable geometry dies that enable the extrusion of plastic parts with a varying cross section. Extrusion accounts for 40% of all manufactured plastic parts because it is a relatively low-cost and high-production-rate process. Conventional polymer extrusion technology, however, is limited to fixed dies that produce continuous plastic products of constant cross section defined by the die exit profile. A shape-changing die allows the cross section of the extruded part to change over its length, thereby introducing the capacity to manufacture plastic faster and with lower tooling costs than injection molding. This paper discusses design guidelines that were developed for movable die features including revolute and prismatic joint details, land length, and the management of die leakage. To assess these guidelines, multiple dies have been designed and constructed to include an arbitrary four-sided exit profile where changes were made to the internal angles and length of sides as the extruder was operating. Experimental studies were conducted by using different extruder line settings and time between die movements. Test results are presented that include shape repeatability and the relationship between extrudate profile and die exit geometry.
Numerical Analysis of Lateral Wave Propagation in Drill-String for Stability Monitoring
Authors: Liu Yu , Dick Andrew J.
Published: March 2015

In this paper, the propagation of lateral waves in a drill-string are studied by using a new numerical method and a stability monitoring scheme is proposed. The drill-string is modeled as a linear beam structure under gravitational field effects. An iterative wavelet-based spectral finite element method (WS-FEM) model is developed to obtain a high fidelity response. Numerical simulations of the lateral impact wave propagation at the bottom-hole-assembly (BHA) are conducted and a time-frequency analysis technique is applied to the response in order to identify the relationship between the position of the transition point between positive and negative strain and the dispersive properties of the lateral wave. Based on the results, a new monitoring scheme is proposed to monitor the stability of the drill-string based on a combination of lateral impact wave analysis at the BHA and the axial acoustic telemetry technique.
On Cross Flow-Induced Vibration of a Flexible Cylinder
Authors: Cen H. , Ting D. S-K. , Carriveau R.
Published: March 2015

An experiment study on the cross flow-induced vibration of a flexible cylinder with two degrees of freedom had been conducted in a towing tank. The test cylinder was a 45 cm long Tygon tubing with outer and inner diameter of 7.9 mm (5/16 in) and 4.8 mm (3/16 in), giving a mass ratio of 0.77 and an aspect ratio of 56. It was towed from rest up to 1.6 m/s before slowing down to rest again over a distance of 1.6 m in still water, covering the range of Reynolds number from 1500 to 13000 and reduced velocity from 4 to 35. Multi-mode vibration and sudden shift between different modes were observed. The vibration amplitude, frequency and mode were quantified. The results obtained during the brief constant towing speed were expressed in term of the corresponding Reynolds number or reduced velocity. These findings were cast with respect to the existing knowledge in the literature.
Optimal Positioning Control of IPMC Actuators
Authors: Tripathi Smriti , Selekwa Majura , Naversen Andrew
Published: March 2015

There has been a growing interest in electroactive polymers (EAP) because of their ability to serve as artificial muscles for both macro and micro positioning tasks. Ionic Polymer Metal Composites (IPMC) are among the EAP materials that have been extensively studied in the last few years. Along with development of better manufacturing methods and increasing understanding of their mechanical properties, extensive studies have been geared towards controlling the actuation of these actuators. Despite many efforts, the one problem that has not been fully addressed is on electromechanical modeling and control of these actuators. This paper presents additional details on the model that was earlier proposed by the authors for positioning such actuators. Experimental data on Nafion IPMC specimens of various sizes indicated that the specimen has both resistive and capacitive properties that vary with time. By using this experimental data, electrodynamics and electrostatics principles were used in developing an electromechanical model that was experimentally validated on Nafion IPMC specimens of various sizes again. The resulting model was found to be nonlinear time varying that can be linearized and controlled by standard linear optimal control algorithms.
The Recreation of a Human Face Using a Low-Cost Reverse Engineering System
Authors: Jacobsen C. , Dominguez A. , Noorani R.
Published: March 2015

The primary goal of this research is to evaluate the effectiveness of a low-cost reverse engineering system to recreate a 3D model of a human face. In order to achieve the goal of this research, three key objectives were fulfilled: (1) the first objective was to recreate the physical model of the human face using a low-cost experimental setup (< $5000) using a NextEngine 3D Scanner and Makerbot Replicator 2, (2) the second objective was to investigate the dimensional accuracy at which models can be produced by the system and (3) the third objective was to evaluate the surface finish of the physical models. A chosen test subject had his face scanned several times using several different orientations. From these scans, a model of the face was generated and built using a low-cost Makerbot Replicator 2 Desktop 3D Printer. The dimensional accuracy and surface finish were then measured on the finished product. Three iterations of two different 3D models of the human face were printed using the MakerBot Replicator 2 in order to create a dimensionally accurate model (< 5% error). While it was known that the reverse engineering system could recreate simple objects with easily defined characteristics with minimal error (< 5%) with no holes or other significant imperfections to the surface finish, it was not known how well it would be able to create something as detailed and complex as the human face. The first printed model of the human face was not recognizable as a human face. The second model possessed dimensional errors of up to 33.33%, the third 3D model had dimensional errors less than 4%. The final model showed no holes or other significant imperfections to the surface finish. Further research can be done trying to recreate the fine details and textures of the human face, such as the eyebrows, lip structure and facial hair.
Modeling of a Dynamic Knee Simulator With Advanced PID Controller to Evaluate Joint Loading Conditions
Authors: Fitzwater Fallon , Lenz Amber , Maletsky Lorin
Published: March 2015

In-vitro dynamic knee simulators allow researchers to investigate changes in natural knee biomechanics due to pathologies, injuries or total joint replacement. The advent of the instrumented tibia, which directly measures knee loads in-vivo, has provided a wealth data for various activities that in-vitro studies now aim to replicate [1, 2]. Dynamic knee simulators, such as the Kansas Knee Simulator (KKS), achieve these physiological loads at the joint by applying external loads to either bone ends or musculature. Determining the external loading conditions necessary to replicate activity specific joint loads, obtained from instrumented tibia data, during dynamic simulations are calculated using computational models.
Wave Propagation Through Soft Tissue: Effect of Material Nonlinearity and Nonuniform Cross–Section
Authors: Valdez Marcelo F. , Balachandran Balakumar
Published: March 2015

A better understanding of the influence of material nonlinearities on the propagation of mechanical stress waves is necessary to generate insights into damage mechanisms of soft tissues subjected to rapid and strong external excitations. In this effort, the authors study the propagation of longitudinal stress waves through soft tissue. Emphasis is placed on the influence of nonlinear material behavior and nonuniform cross–section on the characteristics of the stress–wave propagation. The mechanical behavior of the soft tissue is represented by a nonlinear viscoelastic model that is obtained through a maximum dissipation, thermodynamically consistent construction. The effect of the tissue nonlinear mechanical behavior is studied through asymptotic analysis. Examining the obtained analytical approximation, it is possible to discern nonlinear wave front steepening and the effect of the material dissipation. The effects of a nonuniform cross–sectional area are investigated through numerical simulations. These studies can be applied to understand the effect of geometric features of axons on the propagation of longitudinal stress waves. For example, the diameter of an axon gradually increases near its ends, and varicosities/boutons along the axons represent concentrated cross–sectional area variations. Simulations are carried out to examine various aspects of the nonlinear wave propagation such as wave front steepening. This work can serve as a basis for better understanding the mechanical causes underlying mild traumatic brain injury caused by a head impact or explosive blast waves.
Replacing Servos With Braking in an Omnidirectional Vehicle
Authors: McGough Jeff S. , Bedillion Mark , Hoover Randy C.
Published: March 2015

We present an underactuated approach for steering a vehicle which reduces the number of required servos. This method replaces steering servos with braking actuators which can reduce energy use, weight and support electronics. The design of the steering system, the control system and comparison to traditional steering is considered.