bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy Harvesting From Aeroelastic Instabilities for Highly Flexible Aircraft
Authors: Sotoudeh Zahra
Published: March 2015

Aeroelastic instabilities such as flutter, limit cycle oscillation (LCO), and divergence are traditionally considered undesirable. Designers try to avoid these instabilities by adding enough stiffness or damping to structures. A new approach to suppressing these instabilities is to use smart material to harvest energy from airflow. In this way not only are the aeroelastic instabilities avoided, but also some energy will be harvested. The harvested energy can be used for powering sensors, morphing parts of the structure, and ultimately increasing the performance of the aircraft. Energy harvesting from aeroelastic phenomena can also be used in designing small wind energy harvesters for home use. In this paper we will explore both capabilities. Piezoelectric materials are among the attractive smart materials for energy harvesting. Piezoelectric materials generate electric potential as they deform. We will explore the use of these materials in aeroelastic harvesting. Ref. 1 has a general overview of different forms of vibrational energy harvesting, including the use of piezoelectric materials. Harvesting energy from aeroelastic instabilities is a relatively new area; therefore, the body of literature on this subject is relatively young. Most of the analysis is limited to a 2-D cross-sectional analysis with steady or quasi-steady flow. We will use a 2-D model with an unsteady aerodynamic model as the preliminary result. More realistic cases with a beam model will be added to the final version of the paper. For the beam model, we will use fully intrinsic equations.
Novel Periodic and Turning Motions in the Simplest Passive Walking Model
Authors: Sabaapour M. R. , Hairi Yazdi M. R. , Beigzadeh B.
Published: March 2015

The ability to move along curved paths is an essential feature for biped walkers to move around obstacles. This study is aimed at extending passive walking concept for curved walking and turning to generate more natural and effective motion. Hence three-dimensional (3D) motion of a rimless spoked-wheel, as the simplest walking model, about a general vertical fixed coordinate system has been derived. Then, two kinds of a stable passive turning, i.e. limited and circular continuous have been considered and discussed. The first kind is actually transferring from a 2D periodic motion to another, and can be implemented on a straight slope surface. While, it was shown that the second kind is just related to novel 3D periodic motions and can be recognized on a special surface profile namely “helical slope” introduced here. The latter are interpreted as 3D fixed points of a Poincare return map again. So, their stability was evaluated numerically by a Jacobian analysis and demonstrated through several simulations. Results show asymptotical stability of such motions and their considerable basin of attraction with respect to initial states. In addition, the characteristic of passive turning is shown to be strictly connected with the value of the initial perturbed condition, for instance, to the initial inclination of the wheel. It is then surprising to note that the stability of a 3D passive periodic motion (turning) is higher than 2D one (straight walking) which is actually a special case just with an infinite radius of turn.
Study on Cutting Forces and Surface Finish During End Milling of Titanium Alloy
Authors: Vijayan Krishnaraj , Sadham Samsudeen , Sangeetha Saikumar , Palaniyandi Kuppan , Zitoune Redouane
Published: March 2015

This paper investigates numerical and experimental study of end milling of titanium alloy Ti–6% Al–4% V using carbide insert based cutting tool. The experiments were carried out under dry cutting conditions. The cutting speeds selected for the experiments are 20,30,40,50 mmin–1. The feed rates used in the experiment were 0.02, 0.04, 0.06 and 0.08 mmrev–1, while depth of cut is kept constant at 1.0 mm. For conducting the experiments single insert based cutting tool is based. For a range of cutting speeds and feeds measurements of cutting force, surface roughness and cutting temperature have been recorded. From the experimental study it can be seen that cutting speed has the significant effect on temperature when compared to feed/tooth. Further it is also found that cutting speed of 30 m min−1 and feed rate of 0.02 mm rev−1 could be used for machining Ti alloy. Moreover the experimental and numerical cutting force values are compared.
High-Intensity Targeted Cavitation as a More Efficient and Safer Approach to Treat Kidney Stones
Authors: Dion Steven , Riel Louis-Philippe , Sourial Michael W. , Brouillette Martin
Published: March 2015

An apparatus to provide a safer and more efficient non-invasive treatment of kidney stones is under development. The proposed non-invasive alternative is to produce a tightly focused high-intensity cavitation cloud right at the stone; the cloud being electronically steerable in real time to compensate for the respiratory movements which would significantly reduce the exposition of healthy tissues to damaging shock waves. The piloted cloud is produced by 19 independent novel shock wave generators that are geometrically oriented towards a single focal point. The real-time steering is accomplished by applying different emission delays between the shock wave generators. The steering capability of the 19-channel prototype was monitored in vitro using a pressure sensor and kidney stone analogs. Promising tests were also conducted on ex-vivo pigs to measure the erosion rate of implanted artificial kidney stones.
Nonlinear Vibrations of Pressurized Functionally Graded Plates Using Higher-Order Thickness Stretching Theory
Authors: Alijani F. , Amabili M.
Published: March 2015

Nonlinear vibrations of moderately thick functionally graded (FG) rectangular plates are investigated by considering a higher-order shear deformation theory that takes into account the thickness deformation effect. The geometrically nonlinear strain-displacement relationships are derived retaining full non-linear terms in the in-plane and transverse displacements and the three-dimensional constitutive equations are used by removing the assumption of zero transverse normal strain. The plate is assumed to have immovable boundary conditions at the edges. The equations of motion are obtained by using multi-modal energy approach. A code based on pseudo arc-length continuation and collocation scheme is utilized for numerical continuation and bifurcation analysis. Results show that higher-order thickness deformation theories yield a significant accuracy improvement for nonlinear vibrations of highly pressurized functionally graded plates.
Effect of Helmet Pads on the Load Transfer to Head Under Blast Loadings
Authors: Zhang Timothy G. , Satapathy Sikhanda S.
Published: March 2015

Recent wars have highlighted the need to better protect dismounted soldiers against emerging blast and ballistic threats. Current helmets are designed to meet ballistic performance criterion. Therefore, ballistic performance of helmets has received a lot of attention in the literature. However, blast load transfer/mitigation has not been well understood for the helmet/foam pads. The pads between the helmet and head can not only absorb energy, but also produce more comfort to the head. The gap between the helmet and head due to the pads helps prevent or delay the contact between helmet shell and the head. However, the gap between the helmet shell and the head can produce underwash effect, where the pressure can be magnified under blast loading. In this paper, we report a numerical study to investigate the effects of foam pads on the load transmitted to the head under blast loading. The ALE module in the commercial code, LS-DYNA was used to model the interactions between fluid (air) and the structure (helmet/head assembly). The ConWep function was used to apply blast loading to the air surrounding the helmet/head. Since we mainly focus on the load transfer to the head, four major components of the head were modeled: skin, bone, cerebrospinal fluid (CSF) and brain. The foam pads in fielded helmets are made of a soft and a hard layer. We used a single layer with the averaged property to model both of those layers for computational simplicity. Sliding contact was defined between the foam pads and the helmet. A parametric study was carried out to understand the effects of material parameters and thickness of the foam pads.
Nonlinear Vibrations of Plates in Axial Pulsating Flow
Authors: Tubaldi E. , Amabili M. , Alijani F.
Published: March 2015

A theoretical approach is presented to study nonlinear vibrations of thin infinitely long rectangular plates subjected to pulsatile axial inviscid flow. The case of plates in axial uniform flow under the action of constant transmural pressure is also addressed for different flow velocities. The equations of motion are obtained based on the von Karman nonlinear plate theory retaining in-plane inertia via Lagrangian approach. The fluid model is based on potential flow theory and the Galerkin method is applied to determine the expression of the flow perturbation potential. The effect of different system parameters such as flow velocity, pulsation amplitude, pulsation frequency, and channel pressurization on the stability of the plate and its geometrically nonlinear response to pulsating flow are fully discussed. In case of zero uniform transmural pressure numerical results show hardening type behavior for the entire flow velocity range when the pulsation frequency is spanned in the neighbourhood of the plate’s fundamental frequency. Conversely, a softening type behavior is presented when a uniform transmural pressure is introduced.
A Direct Tool Path Planning Algorithm for Line Scanning Based Stereolithography
Authors: Zhou Chi
Published: March 2015

This paper presents a novel tool path planning approach for polygonal mirror scanning based Stereolithography (SL) process. Compared with traditional laser scanning and mask projection based SL process, the polygonal mirror scanning based process can build part with high surface quality and precision without losing the fabrication efficiency. As an emerging additive manufacturing process, no efficient tool path planning algorithm is available in current system. This paper presented a direct tool path planning algorithm without converting the 3-Dimentional model into 2-Dimentional contours. Different test cases are used to verify its efficiency and effectiveness. Compared with the commercial software, the proposed algorithm is several times faster. Physical parts are also built using the tool path generated by the proposed algorithm.
Friction Coefficient Model of Friction Pair Composed of Automotive Brake Materials
Authors: Wan Zhishuai , Liu Xiandong , Wang Haixia , Shan Yingchun , He Tian
Published: March 2015

The friction experiments are conducted on a pin-on-disc friction material testing machine. The sliding velocity, pressure, temperature and friction coefficient are measured. The effects of brake temperature, brake pressure and braking speed on the friction coefficient are examined. Based on energy conservation theory, the model of friction coefficient is established using statistical methods. Then a semi-empirical model of friction coefficient is established by regression analysis methods. And the effects of the temperature, brake pressure, the relative sliding velocity and these cross-terms on the friction coefficient are also discussed.
The Role of Ethical Issues in Collaborative Manufacturing Research
Authors: Marcelino-Jesus Elsa , Sarraipa Joao , Ilie-Zudor Elisabeth , Jardim-Goncalves Ricardo
Published: March 2015

In the last years an increase in the importance of the role of ethical issues in the world has been observed. Research is a process of collecting and analyzing information to increase the understanding of a phenomenon under study. Due to the complexity of such phenomena, nowadays mostly of the times such research work is performed in a group or community, under public grants accomplishing a collaborative research consortium. Consequently to the nature of such collaborations, ethical conduct is vital to the maintenance of such research communities. This paper provides some information about ethical issues clarifying its importance and challenges in collaborative manufacturing research development and exploitation.
Transient Analysis of In-Plane and Through Thickness Flow During VARTM in the Presence of HPM
Authors: Adhikari Debabrata , Gururaja Suhasini
Published: March 2015

Modeling resin flow for a Vacuum Assisted Resin Transfer Molding (VARTM) process involves developing an approach for coupled flow-compaction, porosity-permeability, resin-cure and stress-development phenomena. In the present work, a modified transient incompressible resin flow model has been developed for VARTM without considering the constant flow rate assumption. The use of High Permeability Medium (HPM) during VARTM results in a through-thickness flow in addition to in-plane flow developing due to the pressure gradient. Results have been validated with existing literature. Fill time comparisons for with and without HPM cases have been presented. Some preliminary results of 2D plane flow have also been obtained which show promise in replicating the physics of vacuum assisted resin infusion composite manufacturing process.
An Analytic Continuation Method to Integrate Constrained Multi-Body Dynamical Systems
Authors: Younes Ahmad Bani , Turner James D.
Published: March 2015

Many numerical integration methods have been developed for predicting the evolution of the response of dynamical systems. Standard algorithms approach approximate the solution at a future time by introducing a truncated power series representation that attempts to recover an n-th order Taylor series approximation, while only numerically sampling a single derivative model. This work presents an exact fifth-order analytic continuation method for integrating constrained multi-body vector-valued systems of equations, where the Jacobi form of the Routh-Voss equations of motion simultaneously generates the acceleration and Lagrange multiplier solution. The constraint drift problem is addressed by introducing an analytic continuation method that rigorously enforces the kinematic constraints through five time derivatives. This work rigorously deals with the problem of handling the time-varying matrix equations that characterize real-world equation of motion models arising in science and engineering. The proposed approach is expected to be particularly useful for stiff dynamical systems, as well as systems where implicit integration formulations are introduced. Numerical examples are presented that demonstrate the effectiveness of the proposed methodology.
Simultaneous Improvement of Micro-Hardness and Surface Finish in Die Steels by Powder-Mixed EDM Process
Authors: Kumar Sanjeev
Published: March 2015

Electrical Discharge Machining (EDM) is widely used by the die and tool making industry for the accurate machining of complex internal profiles in various types of dies. Due to the absence of physical contact between the tool and the workpiece, the hardness of the workpiece is not a consideration in this process and die steels can be machined after hardening. Although EDM is a machining process, it has also been successfully used for improving the surface properties of dies and press tools. The intrinsic nature or the process causes some dissolution of the electrode and these particles may alloy with the machined surface under appropriate machining conditions. Breakdown of the hydrocarbon dielectric under intense heat of the spark contributes carbon to the plasma channel. Another method to produce similar alloying effect is the addition of powders of the desirable elements in the dielectric medium. If such powders are conductive in nature, they affect the energy distribution and sparking efficiency and consequently, the surface finish and micro-hardness. This paper presents the results of an experimental study into electrical discharge machining of H13 hot die steel with graphite powder mixed in the dielectric medium. Copper electrode and kerosene dielectric were used for the experiments and three operating parameters, namely peak current, pulse on-time and pulse off-time were varied. Results show increase in micro-hardness by 42% and improvement in surface finish by 68%. Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) analysis show smooth surface devoid of any craters and significant presence of carbon in the machined surface which is expected to provide self-lubricating properties to the die surface. Chemical composition of the machined surface checked with an optical emission spectrometer shows increase in percentage of carbon from 0.44% to 3.23%. All three operating parameters emerge as significant and the favorable machining conditions for surface alloying are found to be low value of peak current, shorter pulse on-time, longer pulse off-time and negative polarity of the tool electrode.
Analysis of Complex Structures Coupling Variable Kinematics One-Dimensional Models
Authors: Carrera Erasmo , Zappino Enrico
Published: March 2015

One-dimensional models are widely used in mechanical design. Classical models, Euler-Bernoulli or Timoshenko, ensure a low computational cost but are limited by their assumptions, many refined models were proposed to overcome these limitations and extend one-dimensional models at the analysis of complex geometries or advanced materials. In this work a new approach is proposed to couple different kinematic models. A new finite element is introduced in order to connect one-dimensional elements with different displacement fields. The model is derived in the frameworks of the Carrera Unified Formulation (CUF), therefore the formulation can be written in terms of fundamental nuclei. The results show that the use variable kinematic models allows the computational costs to be reduced without reduce the accuracy, moreover, refined-one dimensional models can be used in the analysis of complex structures.
Cutting Speed and Feedrate Based Analysis of Cutting Forces in the One Shot Drilling (OSD) of CFRC/Al Hybrid Stacks
Authors: Salguero Jorge , Ponce Moises Batista , Fernandez-Vidal Severo R. , Mayuet Pedro , Rosales Edwing I. , Marcos Mariano
Published: March 2015

Hybrid stacks structures Composite/Metallic Alloy are commonly applied for manufacturing of structural components in different industrial sectors. Particularly, they are increasingly widely used in the aerospace industry because of these materials combine light weight with a high mechanical resistance. This fact helps to increase the load without needing to increment — even diminishing — the energetic consumption. Carbon Fiber Reinforced Composites (CFRC) and light alloys, such as Aluminium or Titanium based alloys, are usually combined for performing those stacks.

CFRC/Alloy stacks based airship structural elements commonly require drilling operations for the posterior assembly tasks. However, the machining processes of Non-Metal Matrix Composites (NMMC), and particularly CFRC, show significant differences with the machining processes of metallic materials. Because of this, it is very difficult to find a joint only one of cutting parameters for drilling these structures using One Shot Drilling (OSD) techniques.

In this work, a study of the cutting forces developed in the dry-OSD of CFRC/UNS A92024 stacks has been achieved as a function of the cutting speed and feedrate parameters. Dry drilling tests have been performed using different parameters for drilling CFRC and alloy. A change of the parameters in the interface between CFRC and the alloy has been programmed through a CAM software.

Higher cutting force values have been observed in the case of the Aluminium alloys. For both materials, obtained results have shown a strong increase of the cutting force with the increase of feedrate. However, only a slight increase with cutting speed has been observed.

The evolution of the cutting force as a function of the holes number has shown a trend to increase only for highest feedrates when CFRC/Alloy is drilled. From the obtained results a F(f,v) model has been proposed.
3-D FEM Stress Analysis of Screw Threads in Bolted Joints Under Static Tensile Loadings
Authors: Sawa Shunichiro , Ishimura Mitsutoshi , Omiya Yuya , Sawa Toshiyuki
Published: March 2015

The stress concentration factor (SCF) for the roots of screw threads in bolted joints under static loadings is analyzed using 3-D elastic FEM taking account the spiral of screw threads. At first, the stress states at the roots of screw threads in initial clamping state in a bolted joint where two hollow cylinders were clamped with a bolt and a nut were analyzed in initial clamping. The elastic FEM result of SCF for the first root was obtained as SCF=3.2. When the bolt was clamped in initial clamping (preload) at the 60 % of bolt yield stress, the plastic deformations were found at the first and the second roots, and non-engaged screw threads. It was found that as the external tensile loads increased, the development in plastic deformation region increased from the first root to the other roots as well as the non-engaged screw threads. It was found that the rupture occurred from the non-engaged screw threaded part while the plastic deformation increased at each root of screw threads. The numerical result was coincided with the experimental result. In the experiments, it was observed that the rupture occurred from the non-engaged screw thread and not from the first root of screw thread. Also, the bolt fatigue was predicted from FEM and it was shown that a fatigue fracture occurred from the first root.
Liquid Spreading Characteristics due to Substrate Modal Vibrations
Authors: Agrawal Prashant , Gandhi Prasanna S. , Neild Adrian
Published: March 2015

Spreading of liquids on solid substrates is governed by mechanisms which induce contact line motion. Providing mechanical vibrations to the substrate is one such method which has proved effective in displacing the contact line. In the present work we experimentally explore the spreading characteristics of a liquid due to the substrate’s modal vibrations, in the frequency range of around 10kHz. The subsequent findings are then employed to subject the liquid to simultaneous low frequency actuations (in the 100Hz range) and substrate modal vibrations to produce a larger and a more evenly distributed spread about the substrate’s axis than that obtained with any of the two methods individually.
Characterization of Calcified Plaques Retrieved From Occluded Arteries and Comparison With Potential Artificial Analogues
Authors: Riel Louis-Philippe , Dion Steven , Brouillette Martin , Bérubé Simon , Despatis Marc-Antoine , Bousser Étienne
Published: March 2015

Cardiovascular disease is the leading cause of death worldwide. This disease includes chronic total occlusion (CTO), which is a complete blockage of an artery. Unlike partial occlusions, CTOs are difficult to cross percutaneously using conventional guidewires (thin and flexible wires) because of the fibrotic and calcified nature of the blockage. The lack of data regarding the mechanical properties of CTO limits the development of new technologies in the field of percutaneous coronary intervention (PCI) and percutaneous peripheral intervention (PPI). In this study, calcified plaques retrieved from occluded arteries are analyzed in order to better understand their mechanical properties and to help propose an artificial analogue. Calcified plaques samples were collected from the superficial femoral artery wall within one hour following a lower limb amputation surgery. These samples were studied to determine their composition and mechanical properties. The same characterization procedures were performed on various potential artificial analogues. These analogues include three plaster materials and dense hydroxyapatite blocks. The results were then compared with those of the calcified plaques in order to determine the more favorable analogue. This mechanical analysis and the proposal of a potential analogue for the calcified plaques found in occluded arteries could benefit the development of new technologies and devices in the field PCI and PPI.
Tensairity Concept Applied to Lighter-Than-Air Vehicles for Light-Weight Structures
Authors: Suñol Anna , Vucinic Dean , De Laet Lars
Published: March 2015

Airships have the intrinsic advantages of Lighter-Than-Air (LTA) vehicles: minimal energy consumption and Vertical Take-Off and Landing (VTOL) characteristics. Due to these advantages, significant efforts are being taken in order to investigate new applications and technical improvements. More specifically, there is a renewed interest in large airships for heavy payload transportation and for stratospheric airships. The design of large airships is a big challenge, especially when considering the structural point of view, since big volumes imply high loads, and since light weight is a major requirement for this type of vehicles. In this context, a light-weight structure is proposed by applying the structural Tensairity concept. A Tensairity beam consists of a rigid air beam designed on the basis of complete functional separation of the different structural elements, allowing for a maximum optimization. In this paper, the justification of the feasibility of applying Tensairity components in airships is discussed based on two criteria. The first criterion is the justification of the need of a lightweight structure by a state of the art analysis and a study of the principal characteristics of the existing types of LTA vehicles structures. The second criterion is a preliminary technical analysis, which aims to clarify if the load bearing behavior of airships is suited for the application of the Tensairity concept. Moreover, the bases for the development of the concept for the LTA vehicles structures are established.

The advantages and drawbacks of the traditional rigid airships structure in comparison with a non-rigid structure has been analyzed, which conclusion is that the use of a rigid structure is convenient for large airships, since it reduces significantly the stresses of the envelope, but at the same time decreases the payload efficiency due to the addition of the structure’s weight. Moreover, the analysis of the load bearing behavior suggests the technical feasibility of applying Tensairity components, since airships have to withstand high bending moments and Tensairity structures are appropriate for withstanding such loads. Finally, the principal guidelines for defining the various load cases and for modeling Tensairity beams have been defined. In order to confirm the hypothesis of the suitability of Tensairity structures on airships, extensive research on design, analysis and optimization of Tensairity beam grids in typical airship loading conditions is needed.
Signals Generated by a Sensor That Captures the Cantilever Deflection of the Atomic Force Microscope With Nonlinear Behavior
Authors: Nozaki Ricardo , Navarro Hélio A. , Brasil Reyolando , da Silva Marcelo A. Pereira , Tusset Angelo M. , Bueno Atila M. , Balthazar José M.
Published: March 2015

This paper presents results obtained numerically by an experimental approach. The sensor of the atomic force microscope generated cantilever deflections series that were recorded in data files as a function of time and as a function of tip-sample distance. With these series of deflections, we attempted to adjust parameters and refine models of classical oscillators atomic force microscope, making them more sensitive to tip-sample distance, through the method of system identification proposed by [12]. This method allows us to choose any model and, through its analytical solution, compare the results obtained with the experiment. The reconstruction of the state space is done with the intention of observing different phase portraits for different distances between sample-tip.
Effects of Common Breaching Practices on the Overpressures Recorded Within the Stack
Authors: Walilko Timothy J.
Published: March 2015

The objective of this paper is to provide useful information to both military and law enforcement dynamic entry teams for estimating the level of protection provided by their standard protective equipment and procedures. The procedures investigated include: the K-Equation for predicting safe standoff, the effects of stack spacing, and the effect of the orientation of the stack within the blast field on the breachers’ blast exposure. This investigation leveraged both experimental data gathered during explosive breaching training exercises (Breacher Consortium, 2011 - draft) and numerical simulations using the shock physics code CTH (McGlaun, 1990).

The analysis revealed that the presence of objects within the blast range, including the other team members, significantly affected the individual’s exposure to the point that it sometimes exceeds current exposure recommendations. When each team member’s exposure was compared to the current limit of 4 psi (28 kPa), the average pressure from the gauges on the breacher helmets exceeded that level 43% of the time, and the averaged pressure at the shoulders exceeded the limit 50% of the time. In a comparison of the measured incident impulse energy to the maximum impulse energy predicted based on 4 psi peak pressure, the helmet impulse energy was exceeded 79% of the time and 64% of the time at the shoulders. Because the K-Equation was shown to be accurate in predicting the free-field pressure, these results and the output from the numerical simulations suggest that the stack and blanket do not provide the level of protection anticipated and that reducing the standoff distance, as prescribed by some protocols, is not justified.

Ultimately, the operational impact of these results will depend on efforts to identify blast exposure injury thresholds. Since there is a direct relationship between the peak overpressure and total impulse to which the breaching team members in the stack are exposed, injury thresholds must reveal which component, pressure, impulse or a combination is more injurious. Based on whether pressure or impulse must be minimized, the ideal stack configuration can be calculated using the developed numerical model.
Computational Modeling of 3D Printed Tissue-on-a-Chip Microfluidic Devices as Drug Screening Platforms
Authors: Tourlomousis Filippos , Chang Robert C.
Published: March 2015

Physiological tissue-on-a-chip technology is enabled by adapting microfluidics to create micro scale drug screening platforms that replicate the complex drug transport and reaction processes in the human liver. The ability to incorporate three-dimensional (3d) tissue models using layered fabrication approaches into devices that can be perfused with drugs offer an optimal analog of the in vivo scenario. The dynamic nature of such in vitro metabolism models demands reliable numerical tools to determine the optimum tissue fabrication process, flow, material, and geometric parameters for the most effective metabolic conversion of the perfused drug into the liver microenvironment. Thus, in this modeling-based study, the authors focus on modeling of in vitro 3d microfluidic microanalytical microorgan devices (3MD), where the human liver analog is replicated by 3d cell encapsulated alginate hydrogel based tissue-engineered constructs. These biopolymer constructs are hosted in the chamber of the 3MD device serving as walls of the microfluidic array of channels through which a fluorescent drug substrate is perfused into the microfluidic printed channel walls at a specified volumetric flow rate assuring Stokes flow conditions (Re<<1). Due to the porous nature of the hydrogel walls, a metabolized drug product is collected as an effluent stream at the outlet port. A rigorous modeling approached aimed to capture both the macro and micro scale transport phenomena is presented. Initially, the Stokes Flow Equations (free flow regime) are solved in combination with the Brinkman Equations (porous flow regime) for the laminar velocity profile and wall shear stresses in the whole shear mediated flow regime. These equations are then coupled with the Convection-Diffusion Equation to yield the drug concentration profile by incorporating a reaction term described by the Michael-Menten Kinetics model. This effectively yields a convection-diffusion–cell kinetics model (steady state and transient), where for the prescribed process and material parameters, the drug concentration profile throughout the flow channels can be predicted. A key consideration that is addressed in this paper is the effect of cell mechanotransduction, where shear stresses imposed on the encapsulated cells alter the functional ability of the liver cell enzymes to metabolize the drug. Different cases are presented, where cells are incorporated into the geometric model either as voids that experience wall shear stress (WSS) around their membrane boundaries or as solid materials, with linear elastic properties. As a last step, transient simulations are implemented showing that there exists a tradeoff with respect the drug metabolized effluent product between the shear stresses required and the residence time needed for drug diffusion.
Redundancy Resolution for Singularity Avoidance of Wheeled Mobile Manipulators
Authors: Abbaspour Adel , Jafari Hadi Zare , Hemmat Mohammad Ali Askari , Alipour Khalil
Published: March 2015

Mobile robots consist of a mobile platform with manipulator can provide interesting functionalities in a number of applications, since, combination of platform and manipulator causes robot operates in extended work space. The analysis of these systems includes kinematics redundancy that makes more complicated problem. However, it gives more feasibility to robotic systems because of the existence of multiple solutions in a specified workspace. This paper presents a novel combination of evolutionary algorithms and artificial potential field theory for motion planning of mobile manipulator which guaranteed collision and singularity avoidance. In the proposed algorithm, the developed concepts of potential field method are applied to obstacle avoidance and interaction of mobile base with manipulator is used as a new idea for singularity avoidance ability of intermediate links for mobile operations. For this purpose, kinematic and dynamic modeling is derived to define redundant solutions. Afterward, methods from potential field theory combine with evolutionary algorithms to provide an optimum solution among possibly of redundancy resolution scheme. A controller based on dynamic feedback linearization is augmented to track the selective motion trajectory. Simulation results verify obstacle avoidance, singularity avoidance for the manipulators and asymptotic convergence of the robots errors.
System for Assistance on Bath of Bedridden Elderly People
Authors: Bezerra Karolina , Machado José , Carvalho Vitor , Soares Filomena , Silva Bruno , Matos Demétrio , Leão Celina P.
Published: March 2015

From Ambient Assisted Living (AAL) perspective it is important to have information regarding the type of care needed by bedridden elderly people (BEP) living in their homes, in order to support independence, autonomy and maximize their quality of life. Some basic tasks as eating, taking a bath and the hygiene cares may be difficult to execute, regarding that almost always the main caregiver is the other element of the couple (husband or wife). Following this trend, the development of mechatronic devices is of upmost importance in creating solutions to facilitate these tasks. This paper presents the conceptual design of a mechatronic system especially devoted to the assistance during the bath of BEP. Issues as reducing the number of caregivers to only one to assist the bath and reducing the system’s handling complexity (because most of the time it will be used by an aged person) are considered. Visits to rehabilitation centers and hospitals, and respective working meetings, are considered in the development of the proposed mechatronic system.
Multiphysics Chaotic Interaction in a Coupled Electro-Magneto-Mechanical System
Authors: Romeo Francesco , Georgiou Ioannis T.
Published: March 2015

The dynamic response of an electro-magneto-mechanical coupled system excited by a harmonic voltage is addressed. The system mathematical model involves coupling quadratic nonlinearities due to the dependence of the inductance on the displacement of the metallic oscillator mass; as a result, a strongly nonlinear behavior characterizes the system’s dynamic response. The numerical analysis is carried out through Poincaré mappings and dynamic continuation. The initial periodic attractor is shown to evolve into higher order and quasi-periodic attractors as the forcing amplitude increases. The peculiar irregular dynamics involving a number of bifurcations characterized by dramatic qualitative changes of both the mechanical and electrical responses for high excitation amplitude is discussed.
Experimental Evaluation of Wear Features of W-25%Re Pin Tool Used in Friction Stir Welding Mild Steel
Authors: Iqbal Zafar , Shuaib Abdel Rahman , Al-Badour Fadi , Merah Nesar , Bazoune Abdelaziz
Published: March 2015

This paper presents the results of studying butt welding of 4 mm thick mild steel plate with a W-25% Re pin tool using the relatively new friction stir welding (FSW) process. The study includes investigating the wear behavior of the pin tool and the effects of process conditions such as rotational speed on the quality of the weld, microstructures and hardness of mild steel. The results reveal that the traverse (welding) force increases with the increase in the traveled distance of the pin tool, whereas torque decreases with the increase in the travelled distance of the pin tool. The tool has shown wear resistance at lower rotational speed, but with the increase of the rotational speed, wear of the tool became prominent. All welded samples revealed grain size refining. Furthermore, at high rotational speed martensitic structure phase developed due to phase transformation. Different distinct regions of stir zones, thermomechanical heat affected zones and heat affected zones were present in the weld.
Nonlinear Free Vibration Analysis of a Fluid-Conveying Microtube
Authors: Mashrouteh Shamim , Sadri Mehran , Younesian Davood , Esmailzadeh Ebrahim
Published: March 2015

Nonlinear free vibration of a microstructure has been analyzed in this study. A fluid-conveying microtube is mathematically modeled using non-classical beam theory. Partial differential equation of the model is considered in non-dimensional form. Simply-supported boundaries are taken into account and assuming three vibrating modes, an analytical method is employed to obtain the nonlinear equations of motion. Variational iteration method has been utilized as an analytical solution technique. In order to obtain the nonlinear natural frequencies of the system, analytical expressions are found based on this method. A parametric study is also carried out to investigate the effect of different parameters on the vibration characteristics of the microstructure.
Fluid-Structure Interaction Within a Fuel Assembly Subjected to Seismic Excitation
Authors: Chang Gary H. , Modarres-Sadeghi Yahya , Karazis Kostas , Williams Gary T. , Hatman Victor , Matthews Brett
Published: March 2015

The interaction between fuel assemblies during a seismic or loss of coolant accident (LOCA) event is directly associated with safety and reliability issues for all types of nuclear reactors. This study concentrates on the modeling of a single fuel assembly represented by a cylinder subjected to external flow and an external forcing function at the base. The model investigates the response of the fuel assembly using continuum mechanics model. The general behavior of a cylinder supported at both ends and subjected to axial flow is summarized: The cylinder undergoes several flow-induced instabilities as the flow velocity increases. These instabilities start with a pitchfork bifurcation, resulting in the buckling of the cylinder. At higher flow velocities, period-doubling and torus instabilities are observed as well, eventually leading to chaotic oscillations of the cylinder. It is shown that an increased confinement results in lower critical flow velocities for the first point of instability, resulting in buckling at lower flow velocities. The cylinder response to a base excitation is also considered and it is shown that the response amplitude can change depending on the frequency of base excitation.
Joint Loading Effect on Kinematics of the Natural Knee During a Range of Simulated Walking Profiles
Authors: Fitzwater Fallon , Cole Kim , Maletsky Lorin
Published: March 2015

The physiological ratio of compression to anterior-posterior (A-P) knee joint loads has substantial effects on the loading of soft tissue structures, patellofemoral loads, and knee kinematics [1, 2]. There is also a direct relationship between resultant kinematics and joint forces. D’lima et al. was also able to compute A-P kinematics at a given flexion angle with minimal error using measured A-P and compressive load acquired from the instrumented tibia [3]. The direction of A-P load measured at the tibia is associated with the direction of translations of the femur relative to the tibia.
Preliminary Design and Analysis Tool for Aeroengine Turbine Fixings
Authors: Twahir Abdulhalim , Roy François , Attia Magdy , Moustapha Hany
Published: March 2015

A single platform D&A (Design & Analysis) tool is outlined in this paper that allows a user, through a single GUI (Graphical User Interface), to create a turbine rotor fixing as well as analyze the structural integrity of the fixing. This is done through the integration of CAD (Computer Aided Design) and FEA (Finite Element Analysis) software running in batch mode, driven by the GUI. This SPIE (Single Platform Integration Environment) captures the strength of CAD software to create a fully parameterized fixing that is able to model legacy, current designs and provides flexibility to design fixings not yet conceived. Using the automated use of FEA software through a secure and reliable gateway, stress analysis can be performed and the results displayed back to the user through the GUI. This tool provides a significant increase in quality and time savings to design a fixing when compared to the previous design methodologies. What used to take hours to design and analyze through the use of isolated specialist built and owned tools with little communication between them and non-ideal data management, now takes minutes; a reduction of up to 10 fold in the time taken.
Reactive Power-Based Performance Index for Planar Mechanisms
Authors: López Juan David , Rodríguez Carlos Francisco
Published: March 2015

This paper presents a new reactive power-based performance index of planar mechanisms. This index quantifies how much of the power introduced to a mechanism is transformed into motion. Generally, the mechanical advantage is used as an index to quantify the force or the velocity ratio between the input and the output link of a mechanism. However, this index is sensitive to the dimensions of the inlet and outlet of the mechanism so it cannot be used for the comparison of different types of mechanisms. To overcome the drawback of the physical inconsistency, the concept of reactive power is proposed to quantify the losses that occur in a mechanism and, based on this concept, the reactive power-based index is defined. The proposed approach is applied to various mechanisms and it is compared with the mechanical advantage to observe that the proposed index provides the same information as the mechanical advantage, but being dimensionally consistent for the analyzed cases (dimensionless in all cases), it can be used to the analysis, comparison and optimal design of different planar mechanisms.
The Effects of Directionality of Blunt Impacts on Mechanical Response of the Brain
Authors: Sarvghad-Moghaddam Hesam , Karami Ghodrat , Ziejewski Mariusz
Published: March 2015

The intrinsic complexity of the human head and brain lies within the non-uniformity of their constitutive components in terms of shape, material, function, and tolerance. Due to this complexity, the directionality of impact, when the head is exposed to an assault, is a major concern as different responses are anticipated based on the location of impact. The main objective of the study was to show that while most studies propose the injury criteria as based on the kinematical parameters, the tissue-level brain features are more substantiated injury indicators. Accordingly, a finite element (FE) approach was employed to elucidate the injury-related behavior of the head for front, back, and side impacts against a rigid wall. To this end, a 50th percentile FE head-neck model, including most anatomical features, was used. The kinematics of the head in terms of the linear acceleration, as well as the biomechanical response of the brain at the tissue level in terms of intracranial pressure (ICP) and maximum local shear stress, were evaluated as the main injury criteria. Ls-Dyna, a transient, nonlinear, and explicit FE code, was employed to carry out all the simulations. To verify the influence of impact directionality, identical boundary conditions were enforced in all impact scenarios. While brain responses showed similar patterns in all three directions, different peak values were predicted. The highest peak values for the local shear stress, ICP gradient, and the center mass linear acceleration of brain were observed for the frontal impact. These threshold values are of great significance in predicting injuries such as diffuse axonal injury (DAI) resulting from the shear deformation of brain axons. It is believed that directionality considerations could greatly help to improve the design of protective headgears which are considered to be the most effective tools in mitigating a TBI.
Universal Android-Based Kit for Wireless Control of Wheelchairs
Authors: Mitzlaff Paul , Niznik Robert , Alqasemi Redwan , Dubey Rajiv
Published: March 2015

The use of apps on hand-held devices has the potential to offer advancements in controlling many devices with an intuitive user interface, including power wheelchair control. Many powered wheelchair users require special adaptations to their control interface in order to drive the chair. This paper presents the development and testing of an Android based control system for a powered wheelchair. The control system utilizes the Android device’s sensors to control the wheelchair. The device can be attached to various parts of the user’s body which the user can move to control the wheelchair. The accelerometers in the device are used to drive the chair using Bluetooth technology connected to the wheelchair’s control system. Subject testing was performed with the user holding the Android device in their hand while they performed a variety of structured tasks. These series of tasks were duplicated while the Android device was attached to their hat and again when strapped to the upper left arm. The results from the collected data on specific metrics were compared against similar data when the wheelchair is controlled using a standard wheelchair joystick.