bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Callus Ossification and Extraosseous Formation on the Mechanical Performance of Internal Fixation Systems
Authors: Coates Cameron , Heurter Chad , Hippert Scott
Published: March 2016

An investigation into the effect of extraosseous formation around an internal fixation plate (long bone mid-shaft) and callus ossification on the localalized stress distribution in the periosteum is performed. An analytical model of the system is developed; predicted trends are compared with Finite Element (FE) model predictions. Both models are described and the limitations relevant to their predictions are discussed. Two load cases are examined: pure bending and bending coupled with compression. Both models indicate that the presence of the plate results in stress shielding for both load cases. For the pure bending case, the analytical model predicts that the extraosseous formation serves to reduce the level of stress shielding caused by the plate, while the FE model predicts an increase. Both models predict that the presence of callus serves to further increase stress shielding, however the magnitude of the effect of the callus on the tension side of the bone differs substantially between models. Further refinement of both models is recommended.
Development and Validation of Multibody Model of Wind Energy System
Authors: Al-Shahrani Ali S. , Nada Ayman A.
Published: March 2016

The wind energy is observed as an essential and powerful energy resource for the socio-economic development. It is proposed that the small-size wind turbines can demonstrate the innovative solution for the wind energy conversion for low speed regions. An innovative design, control, and monitoring processes require accurate and validated dynamic model of such turbines. In this investigation, the flexible multibody dynamics approach is used to extend the traditional method of dynamic modeling of small-size wind turbines. A systematic approach is developed based on Floating Frame of Reference formulation (FFR) that includes the dynamics of the flexible blades as well as the aerodynamic loads. Beam element is used to model the blade structure with variable twist angle and the corresponding generalized aerodynamic forces are developed. In order to counteract the effect of the geometric stiffening, the coupling terms in the expression of axial strain energy are taken into account. An experimental test-rig equipped with wind generator is used for the FFR model validation. The equipment gives a maximum discharge flow of 10 [m/s] in a 500 [mm] diameter duct. The dynamic effect of the twist angle of 30 [cm] diameter of rotor blades is studied based on the measured rotor speed of the wind turbine. High sensitivity multi-axis accelerometers are used to measure the induced vibration and the data points are collected via data acquisition card of 16 bit resolution. The comparison of experimental results and numerical solution shows a very good agreement and consequently the wind turbine model obtained is suitable for stress analysis, structural and control design. It is concluded that the FFR formulation is best suited for large rotation and small deformation problems, which coincide with the operational conditions of small-size wind energy systems.
Assessment of the Academic CFD Code Galatea-I With the DARPA SUBOFF Test Case
Authors: Sarakinos Sotirios S. , Lygidakis Georgios N. , Nikolos Ioannis K.
Published: March 2016

In this study an academic CFD code, named Galatea-I, is presented, capable for simulating inviscid, viscous laminar and viscous turbulent incompressible fluid flows. It employs the RANS (Reynolds-Averaged Navier-Stokes) approach along with the SST (Shear Stress Transport) turbulence model to predict turbulent flow phenomena, such as recirculations and separations of flow, on three-dimensional unstructured hybrid grids, composed of prismatic, tetrahedral and pyramidal elements. Discretization of the governing equations is obtained with a node-centered finite-volume scheme. Parallel processing and agglomeration multigrid scheme are implemented for the acceleration of the numerical process. As the title of this paper reveals, the solver is validated against the test cases of the DARPA SUBOFF program; in particular, flows over the SUBOFF bare hull submarine geometry at two incident angles and the SUBOFF hull with fairwater configuration are examined. The obtained results, compared to available in open literature experimental data as well as results computed by reference solvers, indicate the proposed methodology’s potential to accurately simulate complex fluid flows.
CFD Multiphase Flow Modelling of Air Porosity Defect Formation During High-Pressure Die-Casting Filling Process
Authors: Hao J. , Lin Y. J. , Nie Y.
Published: March 2016

High-Pressure Die-Casting (HPDC) is an important process for manufacturing high-volume and low-cost components. In this process molten metal is injected at high speed under high pressure into the die cavity, which often leads to entrapment of air into the liquid metal. This will cause air porosity after solidification, the main defect in the parts made by HPDC. The aim of this work was to develop a CFD multiphase flow simulation method to numerically study the air porosity defect formation in HPDC.

Some numerical models have been developed to predict the air porosity defect in HPDC. However, most of them are limited to one phase flow model which could only simulate the filling process of liquid metal. In this study both the bulk fluid and surrounding air were modeled by a 3D multiphase flow model. The proposed model can describe the entrapment, advection and coalescence of air bubbles within the melt, and thus has the ability to accurately simulate the air porosity defect formation in HPDC.

In the present paper, an incompressible-compressible two-phase flow model was developed. The numerical benchmark test of a broken dam problem was used to demonstrate the effectiveness of the proposed model. Then numerical model was applied to simulate a high speed water filling process. Results of the modeling were compared with corresponding experimental data and good agreement has been found.
Experimental Study of Nitinol Wire Arrangements as Servo-Biomimetics for Facial Muscles
Authors: Hariri Nasir , Riofrio Jose , Shin Moochul
Published: March 2016

This paper examines the implementation of Nitinol wire as a complex-shape actuation source specifically targeted for low-power muscle biomimetics. Nitinol is a type of shape memory alloy (SMA) which recovers its original shape after experiencing large deformation when heated above an austenite finish temperature. Previous preliminary work by the authors demonstrated successful closed-loop force control (i.e., recovery stress) using a simple proportional controller. The work presented in this paper builds upon the previous work by demonstrating closed-loop position control of various wire arrangements in the presence of inertial loads. A predeformed NiTi (4% pre-strain) wire is energized via Joule heating (martensite to austenite) and de-energized by conductive cooling (austenite to martensite). The experimental setup consists of a horizontally arranged NiTi wire (or wire bundle) fixed at one end and connected to a hanging weight through a pulley on the opposite end. The angular displacement of the pulley is measured with a non-contact magnetostrictive angle sensor, thereby providing the control feedback signal for the wire displacement. Successful closed-loop position control is demonstrated, and the relative ease of control is assessed for increasing weights. Given the dynamic loading of the moving wire, a proportional controller alone is insufficient to obtain stabilized responses. Therefore, PID with anti-windup method is employed. Although PID requires some trial and error and is quite sensitive to varying conditions, it appears to be stable and sufficiently precise when properly tuned. The effect of bundling wires on the speed of response is experimentally characterized, and different bundling arrangements are designed and examined in order to increase the geometric rate of convective heat transfer. Increasing the rate of heat transfer is particularly important during the forward (austenite-to-martensite) transformation, since its speed relies solely on passive cooling of the wires. Limitations in controlled load capabilities are discussed in the context of wire diameter, bundle size and controller tuning. A repeatability study of a properly tuned PID controller is also carried out by comparing the first few and last few samples of a 50,000-cycle test. In addition, it is shown that identical wires, when swapped, do not require re-tuning of the PID gains. Finally, this paper shows some preliminary actuator designs that can mimic complex muscle movement. Various geometric arrangements of Nitinol wires are embedded into a curable elastomer with skin-like flexibility and durometer. The potential facial muscle movements from these arrangements are shown and discussed.
A Dual Frequency IVUS Transducer With a Lateral Mode Transmitter for Contrast Enhanced Intravascular Ultrasound Imaging
Authors: Wang Zhuochen , Martin K. Heath , Dayton Paul A. , Jiang Xiaoning
Published: March 2016

Recent studies suggest that dual frequency intravascular ultrasound (IVUS) transducers are promising in contrast ultrasound for molecular imaging or vasa vasorum (VV) assessment to identify vulnerable plaques. Low frequency (1–3 MHz) acoustic waves are widely used for contrast imaging because it can excite microbubbles more effectively. However, conventional thickness mode 1–3 MHz transducers are not suitable for IVUS since bulky transducer size is not permitted in fine IVUS catheters used for coronary interventions (approx. 3-French). In this paper, a dual frequency (2.25 MHz/30 MHz) IVUS transducer with a lateral mode transmitter (2.25 MHz) and a thickness mode high frequency receiver (30 MHz) was designed, fabricated and characterized. In contrast detection tests, superharmonic microbubble responses flown through a 200 μm diameter tube was successfully detected with a contrast to noise ratio (CNR) of 13 dB and an axial resolution (−6 dB) of 0.1 μs (150 μm). The results showed that this dual frequency IVUS transducer with a lateral mode transmitter can be used to detect super-harmonic signal (12th to 15th harmonic) ideal for superharmonic imaging of microvascular structures.
A Moving Frame Method for Multi-Body Dynamics Using SE(3)
Authors: Murakami Hidenori
Published: March 2016

To describe the configuration of a multi-body system, Cartesian coordinate systems are attached to all bodies comprising the system. Their connections through joints and force elements are efficiently expressed by using 4×4 matrices of the homogeneous transformation, presented by Denavit and Hartenberg in 1955. However, at this time, there is no systematic method to compute velocities and angular velocities using the matrices of such homogeneous transformations.

In this paper, homogeneous transformation matrices are identified as a subset of a Lie group, called the special Euclidean group denoted by SE(3). This observation enables the usage of the Lie group theory in multibody kinematics. The effective use of the theory is built upon a platform of a moving frame method as presented in this paper. In this method, for each body-attached Cartesian coordinate system, the coordinate vector basis is written explicitly following Élie Cartan. This moving frame notation enables us to use the Lie algebra of SE(3), denoted by se(3), to compute velocities and angular velocities by minimizing the complexities of the Lie group theory.

For kinetics, a variational method is established in se(3) by deriving a relationship between a virtual angular velocities and the corresponding virtual rotational displacements. This constrained variation of virtual angular velocities allows the derivation of the d’Alembert principle of virtual work from Hamilton’s principle for multibody systems. Utilizing this variational tool, we present a systematic computation of equations of motion from Hamilton’s principle.

Finally, we reduce the spatial dynamics to planar dynamics and list the simplifications achieved in the two-dimensional problems using SE(2). Then, for a two-degree-of-freedom manipulator the analytical equations of motion are obtained to demonstrate the power of the moving frame method.
Experimental Investigation of Micro-Machinability of Nano-TiC Reinforced Inconel Fabricated by Direct Metal Laser Melting
Authors: Liu Xinyu , Lou Ning , Patole Swapnil , Rutman Dan , Wang Yachao , Shi Jing
Published: March 2016

The objective of this paper is to experimentally investigate the machinability of nano-TiC reinforced Nickel based super alloy Inconel 718 fabricated by direct metal selective laser melting (SLM). Four 10×10×3 square test coupons were fabricated with different amount of nano-TiC: (1) pure Inconel 718, (2) Inconel 718+0.25% TiC, (3) Inconel 718 + 0.5% TiC, of 508 microns. The machinability of the four materials were examined in terms of cutting forces, tool wear and chip morphology. Three level of federates (1.0, 1.5 and 2.0 um/flute) and three level of spindle speeds (12,000, 15,000 and 18,000 rpm) were selected and a 32 full factorial experiment was performed on each test coupon. Full immersion slotting was selected with a fixed axial depth of cut at 20 microns. The SEM images of the tools reveal that the dominant wear mechanisms were abrasive wear at the tool tip and flank face. The adhesion and build up edge were also common. The wear rate increases with the addition of nano-TiC. The loss of the AlTiC coating will result in accelerated wear, which was observed for machining of nano-TiC reinforced Inconel 718, but not on pure Inconel 718. The edge chipping and abrasive wear at the tool tip reduced the effective cutting diameter, enlarged the edge radius, and caused the increase of the cutting force. For all the materials tested, the cutting chips had serrated edge on the free surface and much smoother surface on the other side, which suggests that a cyclic chip formation of alternating high shear strain followed by low shear strain. This is in agreement with the chip formation mechanism for the Inconel 718 fabricated with conventional method rather than DMLS. The serration is more severe with the and (4) Inconel 718 + 1% TiC. Tensile tests were performed on all four material and the material strength increases with the increase of the TiC content up to 0.5% then plateaued. The elongation drop significantly with the inclusion of TiC in Inconel substrate. Micro-endmilling experiments were conducted using AlTiN coated WC micro-mill with nominal diameter addition of nano-TiC. The cutting forces were collected with a Kistler 3-axial load cell 9017B. The cutting forces increases with the increase spindle speed (hence surface speed) within the range examined, but the effect of feedrate is not statistically significant. The cutting forces were much higher for TiC reinforced Inconel and the magnitude of the cutting forces increases with the increase of the weight percentage of TiC contents.
Parameter Optimization of Incremental Sheet Metal Forming Based on Taguchi Design and Response Surface Methodology
Authors: Shrivastava Parnika , Roy J. J. , Samal M. K. , Jain P. K. , Tandon Puneet
Published: March 2016

Incremental Sheet Forming (ISF) is a flexible and innovative rapid prototyping technique for the fabrication of limited sheet metal components. In the present investigation, the dependency of formability and thickness reduction of ISF parts on tool diameter, incremental step depth along with the preheating of sheet material has been determined. After preheating, initial grain size of the sheet material is selected as a parameter under study. Incremental Sheet Forming process has been studied using Taguchi design of experiments along with Response surface methodology (RSM). ANOVA, 3D surface graphs, S/N ratio and main effect plots have been analyzed. Results indicated that the initial grain size is the most significant parameter as far as forming load and thickness reduction is concerned in ISF. Preheating of the sheet material reduces forming load and favors homogenous thickness distribution. Response surface is optimized and a model developed can be used to predict forming load and thickness reduction within the limits of factors being studied.
In Situ Polymerization of PEGDA Foam for Bone Defects
Authors: Forghani A. , Garber L. , Chen C. , Devireddy R. , Pojman J. , Hayes D.
Published: March 2016

The purpose of this study is to develop a novel bone replacement using in situ polymerization of thiol-acrylate with adipose tissue derived adult stem cells (ASCs). Specifically, Poly(ethylene glycol) diacrylate-co-trimethylolpropane tris (3-mercaptopropionate) (PEGDA-co-TMPTMP) was synthesized with 10% Hydroxyapatite (HA) foam by an amine-catalyzed Michael addition reaction. Initial characterization studies were performed to determine the temperature profile during the exothermic reaction showing a peak temperature of 50°C. To prevent hyperthermic cell damage and death during the exothermic polymerization procedure, the hASCs were encapsulated in alginate. Characterization of the 3-D structure and interconnectivity of pores in the polymeric foam scaffolds were performed using FIB-SEM and Micro-CT showing uniform distribution of HA. Cell viability experiments within the polymeric scaffold were performed using Vybrant® MTT cell profileration method, as well as fluorescent dyes: Calcein-AM (live) and Ethidium homodimer-1 (dead) showing viability of cells inside the samples.
Observation of Melting Wire Solder for Sleeve Soldering
Authors: Nomura Hajime , Imanishi Ken , Enoki Shinichi , Ebisawa Mitsuo , Tsuji Katsuyuki
Published: March 2016

Wire solders usually contain flux and it can remove an oxide film on the metal surface chemically. The influence of the flux is important in soldering. Recently, the new packaging technology was developed, it is called Sleeve soldering. It is a kind of through-hole technology. Sleeve soldering can prevent to spatter flux contained in the wire solder and solder balls. It is not known behaviors of melting wire solder in the sleeve. The purpose of this study is to investigate the behaviors and to obtain proper conditions for Sleeve soldering. The proper condition consists of two factors. One is temperature of the sleeve. The other is amounts of wire solder. The behavior of melting wire solder in the sleeve is observed using a high speed camera. This paper describes observation results using a high-speed camera and influences of the flux in Sleeve soldering.
Vibration Isolation From Harmonic Disturbances Through Use of Internally Rotating Masses
Authors: Smith Eric , Ferri Al
Published: March 2016

This paper considers the use of a chain of translating carts or housings having internally rotating eccentric masses in order to accomplish vibration isolation. First a single degree-of-freedom system is harmonically excited to uncover the qualitative behavior of each rotating mass. The simple model is then expanded into a chain of housings, containing rotating eccentric masses, which are interconnected with springs. The internal rotating eccentric masses are damped along their circular pathway by means of linear viscous damping. Due to the lack of elastic or gravitational constraint on the rotating eccentric masses, they provide a nonlinear inertial coupling to their housings. Previous research has shown that such systems are capable of reducing shock or impulsive loading by converting some of the translational kinetic energy into rotational kinetic energy of the internal masses. This paper examines the potential for vibration isolation of a chain of such systems subjected to persistent, harmonic excitation. It is seen that the dynamics of these systems is very complicated, but that trends are observed which have implications for practical isolation systems. Using simulation studies, tradeoffs are examined between displacement and transmitted force for a range of physical parameter values.
Development of Video Training Course Containing Human Kinematic Mechanism Analysis for Caregivers
Authors: Liao Mengyuan , Yoshikawa Takashi , Goto Akihiko , Takai Yuka , Ota Tomoko
Published: March 2016

A 30-minute of simple understanding video course was proposed, which included of normal movie comparison between expert and non-expert, corresponding body model motion simulation movie, transfer care process division and different mechanics of movement analysis results. Through video display in training course, nursing care staff could easily compare and catch the motion detail differences with expert and deeply imprinted in mind. In a word, the target of this paper was to give the feedback to elder nursing care occupational site by video training course development, help to improve and optimize beginner and non-expert’s care skill in a shorter cycle period.
Effects of Cyclic Strain at Focal Adhesions on Migration of an Osteoblast
Authors: Fukuno Tomohiro , Shiraishi Toshihiko
Published: March 2016

Cells respond to not only biochemical signals but also mechanical forces, which indicates that cells have some mechanosensors that convert mechanical forces into biochemical signals. According to recent reports, one of the candidates of the mechanosensors is focal adhesions that form multi-protein structures having mechanical links between intracellular cytoskeletons and extracellular matrices. Since the cellular mechanisms of sensing and responding to the mechanical stimulations at focal adhesions have not been clarified yet, we developed a micropillar substrate embedding micron-sized magnetic particles and enabling the micropillars to be cyclically deflected by a time-varied magnetic field. Using the magnetic micropillars, here we apply cyclic strain of some frequencies to a single osteoblast cell through focal adhesions and track cell migration with time-lapse observation to understand how the cell senses and responds to cyclic strain. Our data indicate that the cell may change the direction of migration to move away from the micropillar cyclically deflected in the frequency range from 0.1 to 50 Hz.
Image Schema Based Landing and Navigation for Rotorcraft MAV-s
Authors: Enikov Eniko T. , Escareno Juan-Antonio , Rakotondrabe Micky
Published: March 2016

To date, most autonomous micro air vehicles (MAV-s) operate in a controlled environment, where the location of and attitude of the aircraft are measured with an infrared (IR) tracking systems. If MAV-s are to ever exit the lab, their flight control needs to become autonomous and based on on-board image and attitude sensors. To address this need, several groups are developing monocular and binocular image based navigation systems. One of the challenges of these systems is the need for exact calibration in order to determine the vehicle’s position and attitude through the solution of an inverse problem. Body schemas are a biologically-inspired approach, emulating the plasticity of the animal brain, which allows it to learn non-linear mappings between the body configurations, i.e. its generalized coordinates and the resulting sensory outputs. The advantages of body schemas has long been recognized in the cognitive robotic literature and resulting studies on human-robot interactions based on artificial neural networks, however little effort has been made so far to develop avian-inspired flight control strategies utilizing body and image schemas.

This paper presents a numerical experiment of controlling the trajectory of a miniature rotorcraft during landing maneuvers suing the notion of body and image schemas. More specifically, we demonstrate how trajectory planning can be executed in the image space using gradient-based maximum seeking algorithm of a pseudo-potential. It is demonstrated that a neural-gas type artificial neural network (ANN), trained through Hebbian-type learning algorithm, can be effective in learning a mapping between the rotorcraft’s position/attitude and the output of its vision sensors. Numerical simulation of the landing performance, including resulting landing errors are presented using an experimentally validated rotorcraft model.
Modeling and Actuators Design of an Unconventional Airship
Authors: Khamlia Mahmoud , Bennaceur Sélima , Azouz Naoufel , Samaali Sarra , Abichou Azgal , Lerbet Jean
Published: March 2016

This paper presents a dynamic modeling of a quadrotor flying wing airship. This airship is a scale model of airships dedicated for freight transport. It is equipped with steerable thrusters that made over-actuated. A control strategy based on the linearization of the local equation and the use of backstepping control is applied to this model. We made a focus on the relations between the control vectors obtained from the control strategy and the response of the airship actuators.

Numerical results show the benefits of the proposed algorithm.
Cutting Forces With 3-D Tool Wear Analysis in Orthogonal Tube Machining of 6061-T6 Aluminum Alloy With Uncoated Carbide Tool Inserts Using Cold Compressed Air Versus Liquid Nitrogen as Metal Working Fluids
Authors: Chandrasekaran Vishnu Vardhan , Payton Lewis N. , Hunko Wesley S.
Published: March 2016

Metal working fluids remain in common use throughout many industries where metal cutting is necessary. Optimizing the use of a metal working fluid must balance environmental needs, production needs and economic needs.

An orthogonal tube turning machining experiment on 6061-T6 aluminum alloy was conducted to study the performance of uncoated carbide tool inserts utilizing cold compressed air and liquid nitrogen environments as the metal working fluid of choice. The tool inserts selected for this study did not have any chip breaker and studied at 3 different rake angles of 0°, 7° and 15°. Aluminum alloy 6061-T6 was used because of its commercially dominant availability and usage. Cold cryogenic cooling was selected because of its growing usage in high performance machining applications. The use of cold compressed air has been much less studied in the machining of metals than in the machining of plastics and composites where it is quite commonly used. The comparisons between these two methods represent the first published values comparing the current extremes of gaseous metal working fluid applications in a commercially dominant aluminum alloy.

This statistically designed experiment produced a large amount of comparative data that focused on the wear of the tools in two different cutting environments allowing for multivariate analysis of variance and regressive curve fitting. The orthogonal tube turning was set up on a conventional two axis HAAS TL-2 CNC tool room lathe. Forces were collected utilizing a standard Kistler force dynamometer to record the force data in X, Y and Z axes. Two levels of uncut chip thickness, 0.002” and 0.004” per revolution were maintained with a constant feed and depth of cut of 0.125”. Tool rake angles and depth of cuts were selected to ensure maximum statistical power / decisiveness of the experiment. The experiment was carried out for duration of 1 minute while the force data was collected for the entire duration of cut. New tool insert was used for each factor level combination.

The traditional force analysis results are provided for an orthogonal tube turning experiment. In addition, all tools were analyzed for 3-dimensional rake face wear using an innovative Keyence white light microscope in conjunction with a Dektak surface profilometer. Although cutting forces were statistically the same, the inexpensive, simple cold compressed air produced less rake wear than the more expensive liquid nitrogen for all cutting factor level combinations. There was no measureable benefit in using the more expensive liquid nitrogen system.
A Four-Pendulum Omnidirectional Spherical Robot: Design Analysis and Comparison
Authors: DeJong Brian P. , Yelamarthi Kumar , Bloxsom Brad
Published: March 2016

This paper presents a four-pendulum design for an omnidirectional spherical robot. The robot moves by the rotation of tetrahedrally-located pendulums to change the center of mass, and can do so instantaneously in any direction. In that respect, it is omnidirectional unlike the more common single-pendulum designs. In the paper, the theoretical design is discussed and contrasted to existing theoretical center-of-mass designs in terms of directionality, torque arm, eccentricity, and radius of gyration. The torque arm comparison is based on the envelope of the dynamically-controlled mass (i.e., how far in any direction can the center of mass be moved), while the eccentricity and gyration criteria are based on homogeneity and size of the mass moment of inertia (i.e., how much does the design “wobble” while rolling; how much inertia does it have). In these regards, the four-pendulum architecture is better than some in one respect, better than many in other respects. A prototype has been built and tested to successfully implement the four-pendulum propulsion. Significance of the proposed system is presented through a comparison of results with previous work.
Methane Transcritical Behavior in the Cooling System of the HYPROB-BREAD LOX/LCH4 Demonstrator Rocket Engine
Authors: Ricci D. , Battista F. , Ferraiuolo M. , Salvatore V. , Fragiacomo M.
Published: March 2016

The HYPROB Program, developed by the Italian Aerospace Research Centre, has the aim of increasing the Italian system design and manufacturing capabilities on liquid oxygen-hydrocarbon rocket engines; the most important activity is represented by the development and testing of a ground engine demonstrator of three tons thrust based on methane as propellant. The demonstrator baseline concept is featured by 18 injectors and is regeneratively cooled by using liquid methane. The cooling system has a counter-flow architecture and is made by 96 axial channels; methane enters the channels in the nozzle region in supercritical liquid condition, is heated by the combustion gases along the cooling jacket and then is injected into the combustion chamber as a supercritical gas.

The goal of the present paper is to describe the activities supporting the cooling jacket design, aiming at identifying the optimal configuration of the cooling channels. 3-D CFD analyses have been performed on different cooling channel arrangements, in terms of channel height and rib width. Moreover, simulations described the thermo-fluid dynamic behavior of methane by means of NIST real gas modeling and they were necessary to give the proper input to the thermo-structural analyses in order to verify the most critical sections of the cooling jacket.
On the Development of a Modular 3D Bioprinter for Research in Biomedical Device Fabrication
Authors: Ravi Prashanth , Shiakolas Panos S. , Oberg Jacob C. , Faizee Shahid , Batra Ankit K.
Published: March 2016

Biomanufacturing research involving solid freeform fabrication techniques has become fairly widespread in recent times. The layer-by-layer building concept provides an opportunity towards the development of a modular 3D printer to broaden the scope of biomanufacturing research. This research discusses the features of a Custom Multi-Modality 3D Bioprinter (CMMB) developed in the MARS lab at the University of Texas at Arlington (http://mars.uta.edu/). The CMMB currently includes a number of printing modules; two Fused Filament Fabrication (FFF), one Photo Polymerization (PP), one Viscous Extrusion (VE) and one Inkjet (IJ). The development of the custom bioprinter and each module are discussed; focusing on the advantages of a modular design, and on the unique features present in each individual module. Select constructs fabricated using individual or a combination of modules are presented and discussed. Design of Experiments (DOE) principles employing statistical software were used to characterize the CMMB; interactions between fabrication process parameters and their effect on deposited strand characteristics were analyzed. These results were employed to improve the quality of subsequently fabricated constructs. Initial experiments and fabricated constructs demonstrate that the custom bioprinter is a novel CAD-CAM biomanufacturing platform for research in methodologies, materials and processes for the fabrication of biomedical devices.
Numerical Analysis of Design Parameters With Strong Influence on the Aerodynamic Efficiency of a Small-Scale Self-Pitch VAWT
Authors: Xisto Carlos , Páscoa José , Trancossi Michele
Published: March 2016

In the paper, four key design parameters with a strong influence on the performance of a small-scale high solidity variable pitch VAWT (Vertical Axis Wind Turbine), operating at low tip-speed-ratio (TSR) are addressed. To this aim a numerical approach, based on a finite-volume discretization of two-dimensional Unsteady RANS equations on a multiple sliding mesh, is proposed and validated against experimental data. The self-pitch VAWT design is based on a straight blade Darrieus wind turbine with blades that are allowed to pitch around a feathering axis, which is also parallel to the axis of rotation. The pitch angle amplitude and periodic variation are dynamically controlled by a four-bar-linkage system. We only consider the efficiency at low and intermediate TSR, therefore the pitch amplitude is chosen to be a sinusoidal function with a considerable amplitude. The results of this parametric analysis will contribute to define the guidelines for building a full size prototype of a small scale turbine of increased efficiency.
Dynamic Modelling of an Off-Road Vehicle for the Design of a Semi-Active, Hydropneumatic Spring-Damper System
Authors: Panetta Giuseppe , Mancarella Francesco , Borghi Massimo , Zardin Barbara , Pintore Francesco
Published: March 2016

In this paper a tool integrating a multibody full car model of a tractor and the hydraulic model of the suspension system is presented as a virtual tool able to help the designer and also the control tuning of the system. The full car approach is chosen in order to be able to describe all the vehicles movements (roll, yaw, pitch) while the detailed lumped parameters model of the hydraulic suspensions allows to consider the role of the electrohydraulic valves, accumulator, hydraulic actuator on the vehicle dynamic behaviour. The hydraulic model and the multibody model exchange forces and displacements at the joint points: one between actuator and sprung mass (chassis) and the other one between actuator and unsprung mass (front axle and wheels).

Experimental test have been performed (suspension leveling maneuvers, tests on ISO 50008 track, bump tests) and the results of the numerical model have been compared with the experimental data, allowing the understanding of the influence of the numerous design and control parameters involved in the determination of the vehicle dynamic behaviour. The influence of mechanical and geometrical parameters on the damping force hysteresis measured during levelling test are shown and described. Finally, the dynamic behavior of the suspension is analyzed making reference to a dynamic test over a bump.
Noise-Influenced Response of Duffing Oscillator
Authors: Agarwal Vipin , Balachandran Balakumar
Published: March 2016

Noise is unavoidable and present in a range of engineering systems, and it can play a significant role in influencing system dynamics. In the present study, a combination of experimental and numerical studies are undertaken to understand the responses of Duffing oscillators with hardening and softening spring characteristics. To serve as a prototype for hardening type and softening type oscillators, a cantilever structure with a magnet at the free end is considered. This tip magnet is located in the magnetic field of another magnet that is fixed in position. In the presence of harmonic excitations, the complex motions of this system are examined through experimental and numerical means. The influence of noise on the system response is studied, and it is shown that with an appropriate level of noise, the chaotic behavior of a harmonically forced oscillator can be significantly influenced. The present work provides a glimpse into the possibilities for noise-influenced responses.
MATLAB Image Processing as a Viable Tool to Study Low Surface Roughness
Authors: Hunko Wesley S. , Chandrasekaran Vishnuvardhan , Payton Lewis N.
Published: March 2016

The purpose of this paper is to present the results of a study comparing an old technique for measuring low surface roughness with a new technique of data acquisition and processing that is potentially cheaper, quicker and more automated. It offers the promise of in-process quality monitoring of surface finish.

Since the late 1800s, researchers have investigated the light scattering effects of surface asperities and have developed many interferometry techniques to quantify this phenomenon. Through the use of interferometry, the surface roughness of objects can be very accurately measured and compared. Unlike contact measurement such as profilometers, interferometry is nonintrusive and can take surface measurements at very wide ranges of scale. The drawbacks to this method are the high costs and complexity of data acquisition and analysis equipment. This study attempts to eliminate these drawbacks by developing a single built-in MATLAB function, to simplify data analysis, and a very economically priced digital microscope (less than $200), for data acquisition. This is done by comparing the results of various polishing compounds on the basis of the polished surface results obtained from MATLAB’s IMHIST function to the results of stylus profilometry methods. The study with the MATLAB method is also to be compared to 3D microscopy with a Keyence microscope.

With surface roughness being a key component in many manufacturing and tribology applications, the apparent need for accurate, reliable and economical measuring systems is prevalent. However, interferometry is not a cheap or simple process. “Over the last few years, advances in image processing techniques have provided a basis for developing image-based surface roughness measuring techniques” [1]. One popular image processing technique is through the use of MATLAB’s Image Processing Toolbox. This includes an array of functions that can be used to quantify and compare textures of a surface. Some of these include standard deviation, entropy, and histograms of images for further analysis. “These statistics can characterize the texture of an image because they provide information about the local variability of the intensity values of pixels in an image. For example, in areas with smooth texture, the range of values in the neighborhood around a pixel will be a small value; in areas of rough texture, the range will be larger. Similarly, calculating the standard deviation of pixels in a neighborhood can indicate the degree of variability of pixel values in that region” [2].

By combining the practices of interferometry with the processing techniques of MATLAB, this fairly new method of roughness measurement proved itself as a very viable and inexpensive technique. This technique should prove to be a very viable means of interferometry at an affordable cost.
Microstructure and Mechanical Properties of Ti-6Al-4V Parts Fabricated by Laser Engineered Net Shaping
Authors: Bagheri Allen , Shamsaei Nima , Thompson Scott M.
Published: March 2016

Laser Engineered Net Shaping (LENS®) is a Direct Laser Deposition (DLD) additive manufacturing technology that can be used for directly building complex 3D components from metal powders in a combined deposition/laser-melting process. In this study, the effect of LENS process parameters, such as laser power, powder feed rate and traverse speed, on the resultant microstructure, hardness and tensile strength of Ti-6Al-4V components is experimentally investigated. Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) are used to characterize the microstructure in terms of grain size and morphology. Relationships between process parameters and the microstructural/mechanical properties are provided. Results indicate that the scale of columnar grains increases with slower laser traverse speeds while other process parameters are maintained constant. The size of the α and β laths increases with higher laser powers and slower traverse speeds. The ultimate tensile and yield strengths of the LENS specimens were found to be higher than those of cast and wrought materials, and this can be generally attributed to the different cooling rates inherent to LENS — which impacts grain size. The percent elongation to failure, however, was consistently lower than that of the wrought material.
High Sensitivity Damage Detection With Vibration Mode Shape Tuning Through the Optimal Design of Piezoelectric Actuators
Authors: Zhao Shengjie , Wu Nan , Cheng Yukun
Published: March 2016

This paper develops an advanced technique to significantly increase the frequency based damage detection sensitivity on a beam structure through a mode shape tuning process with the optimal design of the piezoelectric actuators. Piezoelectric sensors and actuators are mounted on the surface of the host beams to generate the feedback voltage and the active controlled excitations respectively. The excitations induced by the piezoelectric effect will be utilized to change the curvature distribution of the vibration mode shapes of the host beam structure so as to magnify the natural frequency difference between the intact beam and the damaged one to realize the high sensitivity damage detection. In this paper, theoretical models of the cantilever beams with and without mode shape tuning induced by piezoelectric layers are built first, while the damage is represented by a fixed end crack. Then, through the numerical simulations, the vibration mode shapes and corresponding natural frequencies of the beams can be solved to study the sensitivity improvement by using the proposed technique. In order to improve the detection efficiency, a couple of piezoelectric actuators are installed symmetrically on the upper and lower surface of the host beam, generating shifty bending moments to tune the vibration mode shapes. The actuation voltages applied on the actuators are determined by applying certain gain to the voltage from the piezoelectric sensors. Different gain factors are applied to the mode shape tuning process to reveal their effects on damage detection sensitivity improvement. As a result of the control process with proper gain factor, the curvature is more concentrated at the position close to the crack in the first vibration mode shape of the damaged beam comparing with the one without mode shape tuning. Therefore, the first natural frequency variation induced by the crack effect with mode shape tuning is much more significant than the one without mode shape tuning. In addition, further numerical simulations also indicate that the improvement of the detection sensitivity is closely related to the dimensions of the piezoelectric actuators. To realize better detection results, the optimal design of the size of the piezoelectric actuators is presented. The optimal length of the piezoelectric actuators is found leading to the best performance on damage detection. The theoretical studies and numerical simulations reflect that the proposed technique with mode shape tuning and optimally designed actuators is effective and promising in the field of damage detection. It is noted that the proposed technique can also be applied to improve the sensitivity of frequency based damage detection on other structures, e.g. plates and frames.
PMMA in Bone Allograft Fixation Utilizing Unicortical Versus Bicortical Screws: A Finite Element Analysis
Authors: Hildebrand Lucas , Allan D. Gordon , Paliwal Manish
Published: March 2016

Bone grafts are widely used in skeletal reconstruction subsequent to tumor surgery, traumatic injuries, or in conjunction with a total joint procedure. As the graft site may be subjected to destabilizing mechanical forces, any motion at the interface between graft and the host tissue may impede or prevent healing. The application and the maintenance of the compression between screw threads and the bone is the most important factor in attaining rigid internal fixation by means of screws or screws & plates. This study is designed to assess various allograft fixation options with the intent of finding an option that is secure yet does minimal damage to the allograft. Utilizing computational modeling and analysis (SolidWorks), we compared the bending stiffness for diaphyseal bone constructs with a gap and stabilized with a dynamic compression plate, with screws placed in a unicortical or bicortical manner, with and without intramedullary PMMA. The model was validated by comparing the simulation results with the experimental results from literature for two unicortical screws application with PMMA in bending test. The study was then exteneded by looking at the stress distribution across the plates with the use of bicortical and unicortical screws with and without PMMA. For unicortical screws the use of PMMA reduces the displacement by 4:65% and reduces the stress by 5:69%. For bicortical screws, the use of PMMA reduces the displacement by 1:78% and reduces the stress by 9:45%. The bicortical screws with PMMA has a displacement which is 0:74% smaller but a stress which is 0:73% higher when compared to the unicortical screws with PMMA. From the results of total displacement and maximum stress on the plate, conclusion can be drawn that the two best arrangements are the use of unicortical screws with PMMA and bicortical screws with PMMA, thus allowing the use of fewer screws.
Segregation of Cortical Bone’s Haversian Systems via Automated Image Segmentation
Authors: Hage Ilige S. , Hamade Ramsey F.
Published: March 2016

The lamellar or Haversian system is comprised mainly of fundamental units “osteons”. Haversian canals run through the center of the osteons where one or more blood vessels are located. The bone matrix is comprised of concentric lamellae surrounding Haversian canals. Those lamellae are punctuated by holes called lacunae, which are connected to each other through the canaliculi supplying nutrients. Haversian canals, lacunae and canaliculi of the Haversian system constitute the main porosities in cortical bone, thus it is advantageous to segregate those systems in segmented images that will help medical image analysis in accounting for porosities.

To the authors’ best knowledge, no work has been published on segregating Haversian systems with its 3 predominant components (Haversian canals, lacunae, and canaliculi) via automated image segmentation of optical microscope images. This paper aims to detect individual osteonal Haversian system via optical microscope image segmentation. Automation is assured via artificial intelligence; specifically neural networks are used to procure an automated image segmentation methodology.

Biopsies are taken from cortical bone cut at mid-diaphysis femur from bovine cows (which age is about 2 year-old). Specimens followed a pathological procedure (fixation, decalcification, and staining using H&E staining treatment) in order to get slides ready for optical imaging. Optical images at 20X magnification are captured using SC30 digital microscope camera of BX-41M LED optical Olympus microscope. In order to get the targeted segmented images, utilized was an image segmentation methodology developed previously by the authors. This methodology named “PCNN-PSO-AT” combines pulse coupled neural networks to particle swarm optimization and adaptive thresholding, yielding segmented images quality. Segmentation is occurred based on a geometrical attribute namely orientation used as the fitness function for the PSO. The fitness function is built in such way to maximize the identified number of features (which are the 3 components of the osteonal system) having same orientation.

The segmentation methodology is applied on several test images. Results were compared to manually segmented images using suitable quality metrics widely used for image segmentation evaluation namely precision rate, sensitivity, specificity, accuracy and dice.

The main goal of segmentation algorithms is to capture as accurate as possible structures of interest, herein Haversian (osteonal) system. High quality segmented images obtained as well as high values of quality metrics (approaching unity) prove the robustness of the segmentation methodology in reaching high fidelity segments of the Haversian system.