bluuebunny/crossref_metadata_2025 huggingface dataset:
Rheology Characterization of Solder Paste
Authors: Barbosa Flávia V. , Ribeiro Pedro E. A. , Cerqueira Maria F. , Soares Delfim F. , Teixeira José C. F. , Teixeira Senhorinha F. C. F. , Lima Rui A. M. M. , Pinho Diana M. D.
Published: January 2018

Reflow soldering process is widely implemented in the electronics industry. This method allows the attachment of electronic components to a printed circuit board (PCB) through the melting of solder paste, which makes the interconnection between them. The reflow soldering process must ensures the correctly melting of the solder paste and heating of the adjoining surfaces, without the electronic components suffer overheating or any other type of damage.

Solder paste is the most widespread material in the SMT (Surface Mount Technology) process using reflow soldering. An ideal solder paste will increase production efficiency, decreasing the amount of defects associated with the reflow soldering process. However, several factors affects the performance of the solder paste, from rheology, printability, and reliability to the adhesion strength of components and the ability to avoid defects related to reflow. Therefore, all these factors need to be considered during the selection of a solder paste for a specific application.

The rheological properties were determined using both a double cylinder (PHYSICA-RHEOLAB MC1) and a double plate (Malvern) rheometers. The later enable the determination of viscoelastic properties.

The present paper analyses the rheological behavior of a SAC405 solder paste, a mixture containing a metal alloy powder (25–45 μm) and a flux which at its base is a resin. The tests were carried out at conditions (temperature and shear rate) of relevance to the printing process. The results obtained show that the paste viscosity closely follows the Herschel-Bulkley model and shows a thixotropic behavior without fully recovery between applications. In addition, the viscosity decreases with the increase of shear rate confirming that the solder paste is a non-Newtonian fluid, shear thinning in behavior. The oscillatory tests have shown that the transition from elastic to viscous behavior occurs at a shear stress above 35 Pa. On the other hand, the creep/recovery test confirms that the level of solicitation influences the capacity of recovery of the solder paste.
Design, Modeling and Optimization of the Universal-Spatial Robotic Tail
Authors: Rone William , Saab Wael , Ben-Tzvi Pinhas
Published: January 2018

This paper presents a novel robotic tail design that utilizes a serial chain of universal joints to generate spatial motion. In nature, animals utilize their tails to assist in maneuvering and stabilization while moving; this research aims to provide a robotic platform capable of extending these functionalities to a mobile robot. By utilizing a tail to assist in stabilization and maneuvering, the required functionality of other locomotion mechanisms in a mobile robot, such as legs, is reduced. The tail mechanism presented is actuated by sets of three cables routed along the robotic structure; quasi-independent segments within the tail are created by tying off a set of three cables to a link along the tail. Actuation is distributed within the underactuated mechanism by compression and extension springs mounted along the tail. Kinematic and dynamic analysis of the tail is performed to model the tail trajectory and predict the actuation requirements. Three methods of optimizing spring stiffnesses are provided that weigh different performance goals, and a methodology for using these results to select spring stiffnesses is provided. Results are generated to compare the kinematic, static and dynamic models to one another to analyze the impact the different loading effects have on the tail behavior.
Three Dimensional Measurements of a Turbine Blade Using Magnetic Resonance Thermometry and Magnetic Resonance Velocimetry
Authors: Williams Elliott T. , Caniano Daniel C. , Davis Gregory , Ferrell Angus M. , Benson Michael J. , Van Poppel Bret P. , Elkins Christopher J.
Published: January 2018

A hollowed NACA-0012 airfoil with removable inserts was developed to study the complex flow through two interior chambers. The geometry represented an internally cooled gas turbine blade with internal impingement in several locations. A fully turbulent water flow passed the airfoil. Within the airfoil, a second fluid at a different temperature was mixed through the insert nearest the leading edge and recirculated to the aft chamber for additional internal cooling before exiting the airfoil as film cooling on the suction side and at the trailing edge. Time-averaged, three-dimensional temperature and three-component velocity measurements were collected using Magnetic Resonance Imagery (MRI) based techniques.

Magnetic Resonance Velocimetry (MRV) and Thermometry (MRT) are techniques for measuring the velocity and temperature of fully turbulent flows at sub-millimeter-scale resolution. The benefits of these techniques over similar measuring techniques include the ability to collect full-field, three-dimensional, nonintrusive, non-optical measurements for conjugate heat transfer simulation validation in complex, turbulent flows. Multiple MRI-based techniques can be combined within the same experiment to explore the interaction between the mean fields of multiple quantities. The experimental setup employed in this work produced time-averaged velocity and temperature data illustrating flow details through the airfoil’s interior chambers and heat flux through the entire airfoil and at specific locations.
Sensing Artificial Hole and Crack in Carbon Nanotube Enhanced Glass-Fiber Reinforced Composite Panel
Authors: Ikikardaslar Kerim Tuna , Ardebili Mahmoud K. , Delale Feridun
Published: January 2018

Glass fabric epoxy resin based composite panels enhanced with carbon nanotubes were subjected to damage while changes in electrical resistance were obtained via embedded electrodes. The purpose of the study was to develop an alternative method to Electrical Impedance Tomography (EIT), which generates conductivity field, hence, indicating presence of various damages. The current method provides damage field by taking meticulous measurements of electrical resistance of panel. The method does not monitor conductivity as in the EIT but utilizes electrical resistance changes to detect damage. In the current form, it employs a network of 64 (8 × 8 grid) electrodes distributed evenly in a typical panel instead of the boundary electrodes used in EIT. Even though 64 electrodes were employed, fewer electrodes were sufficient to produce accurate indication of damage location and its size. In previous studies percolation threshold for carbon nanotube-epoxy mixture was determined, which enabled selection of optimal CNT concentration used in manufacturing of glass fiber reinforced panels. The glass fiber reinforced panels were manufactured by vacuum infusion method. The typical panel consisted of 10 glass fabric (S-2) plies. Copper electrodes were embedded beneath the top layer fabric ply. Electrical resistances measurements were obtained using four-probe technique. In the four-probe method, two outer electrodes are used to source a known current through the panel, while the two inner electrodes provide voltage drop needed to compute resistance. The technique minimizes contact resistance between electrodes and the composite, which could be order of magnitude larger than the material resistance being measured. Electrical resistance of cured glass fiber reinforced CNT-epoxy panels was first measured without any damage. Afterwards, damages in form of circular hole were inflicted to the panel starting with 1/8” diameter and enlarging it to 1/2” in steps of 1/8”. After the largest hole, 0.04” (∼1 mm) width cracks emanating from the hole were inflicted. During all measurements, electrical current passing through the source and sink electrodes was kept constant and changes in voltage from the inner probes were recorded. The thrust of the method is to incorporate a curve fit for quantifying the changes in resistance. The method can be applied to damage quantification in panels. The smaller spaced electrode distribution was more sensitive to smaller damages as expected, but the larger spaced electrodes network was sufficiently responsive to smallest damage. Experimental results were fairly good at predicting the damage and its magnitude. Results also indicated a very good agreement with the finite element simulations of the panels. Application of this technique can be a powerful tool for real time structural health monitoring of manufactured composites.
Understanding Fundamental Physics of Aqueous Droplet Generation Mechanisms in the Aqueous Environment
Authors: Mastiani Mohammad , Seo Seokju , Melgar Jimenez Sofia , Petrozzi Nick , Kim Myeongsub (Mike)
Published: January 2018

Recent advent of Aqueous-Two-Phase-System (ATPS), more biologically friendly compared to conventional oil-water systems, has shown great potential to rapidly generate aqueous droplets without tedious post-processing. However, understanding of underlying physics of droplet formation in ATPS is still in its infancy. In this paper, we investigate hydrodynamic behaviors and mechanisms of all-aqueous droplet formation in two flow-focusing droplet generators. Two incompatible polymers namely polyethylene glycol (PEG) and dextran (DEX) are mixed in water to make ATPS. The influence of inlet pressures and flow-focusing configurations on droplet sizes, and thread breakup length is studied. Flow regime mapping for two different configurations of droplet generators possessing junction angles of 30° and 90° is also obtained. The results show that droplet size is very susceptible to the junction angle while inlet pressures of the PEG and DEX flows readily control four main flow regimes including back flow, dripping, jetting and stratified.
Modeling and Characterization of PCM-Based Thermal Energy Harvesting
Authors: Wang Guangyao , Ha Dong , Chao Yi , Wang Kevin G.
Published: January 2018

This paper investigates the feasibility of using phase change materials (PCMs) to harvest the environmental thermal energy, which is often associated with a relatively low temperature differential, less than 100°C. First, we develop a thermodynamic model for an idealized setting based on Tait equation of state, thereby deriving a theoretical upper limit of the thermal efficiency that can be achieved using PCMs. Next, we couple the thermodynamic model with a structural mechanics model based on Kirchhoff-Love plate theory, and predict the performance of specific PCM-based energy harvesters that convert the harvested energy into mechanical energy. To validate the thermomechanical model and demonstrate the feasibility of the underlying approach, we present the development and characterization of a prototype device. The measured specific energy and the prediction of the thermomechanical model are in close agreement.
Thermal Transport in Thorium Dioxide
Authors: Park Jungkyu , Farfán Eduardo B. , Enriquez Christian , Kinder Nicholas , Greeson Matthew
Published: January 2018

Thorium is more abundant in nature than uranium and thorium fuels can breed fissile U-233 fuel that can be used in various types of nuclear reactors. Moreover, thorium dioxide has drawn interest from researchers due to its relatively superior thermal properties when compared to conventional uranium dioxide fuel pellets. In this study, thermal transport in thorium dioxide is investigated using reverse non-equilibrium molecular dynamics. The thermal conductivity of bulk thorium dioxide was measured to be 20.8 W/m-K and the phonon mean free path was estimated to be between 7 ∼ 8.5 nm at 300 K. It was also observed that the thermal conductivity of thorium dioxide has a strong dependency on temperature; the thermal conductivity decreases with an increase in the temperature. Moreover, by simulating thorium dioxide structures with different lengths at different temperatures, it was also identified that short wavelength phonons dominate thermal transport in thorium dioxide at high temperatures, resulting in decreased intrinsic phonon mean free paths and minimal effect of boundary scattering while long wavelength phonons dominate the thermal transport in thorium dioxide at low temperatures.
Shape Memory Alloy As Artificial Muscles for Facial Prosthesis
Authors: Mazza Paul , Shin Moochul , Santamaria Anthony
Published: January 2018

Facial paralysis affects hundreds of thousands of people each year; a common result of infection, trauma, stroke, and Bell’s palsy, among others. Achieving facial prosthetics that are lightweight, comfortable, aesthetically pleasing, energy efficient, and that allow human-like facial motion is a challenge. This study focuses on examining the feasibility of the use of a shape memory alloy as a means of low-power artificial muscles. Nitinol is a shape memory alloy (SMA) that can recover up to four percent of its original length when exposed to either a large enough change in temperature which can be controlled via electrical current or a stress. In this work, human eyelid muscles are replicated using Nitinol embedded in silicon. Silicone is used due to its elasticity, texture, flexibility, compatibility and ease of manufacturing. A mold is created based on human facial geometry around the orbital using a 3D printer. Based on average human eyelid dimensions, as well as the contraction properties of the Nitinol wire, an elliptical equation is used determine the length of wire required to completely close the eyelid from an open position. Temperature change of the system is controlled by modulating current through the resistive Nitinol wire. The contraction and expansion times of the eyelids are measured. The circuit is then optimized so that response times mimicked that of the human eyelid. Finally, based on the amount of times the average human blinks, the average daily power consumption is calculated. Future directions including miniaturization of the control system, bonding between SMA wires and silicone, and energy management are discussed.
A Review of the State of Art in Heat Sealing of Multilayer Polymer Films
Authors: Uribe Juárez Jorge Enrique , Ramírez-Reivich Alejandro C. , Mendoza Covarrubias Crisanto , Corona-Lira Ma. del Pilar
Published: January 2018

All sealing technologies present inconveniences to be solved. One of the most significant adverse effects in the sealing production lines is the amount of material waste that is genetated due to the difficulties of achieving the correct thermal phase change in the polymer film during the sealing process. Sealing methods such as Induction, ultrasonic or heated jaw have similar operating characteristics, minimum gradients in pressure and temperature that are nedeed to create an efficient polymer transition, to produce the correct molecular arrangements and to avoid zones with little or null interaction between melted surfaces. This review shows the factors that affect the performance of jaw-multilayer polymer films that produce bad seal integrity; through understanding the design parameters to generate a small pressure and temperature gradients also characterizing and testing this phenomenon, the result of the review will help to identify theoretical basis and opportunities to design an innovate heated jaw sealing system with a uniform pressure and temperature along the sealing area.
Characterization of Adhesively Bonded Composite Joints Under High Strain Rate Loading
Authors: Gollins Kenneth , Chiu Jack , Baudrand Céline , Delale Feridun
Published: January 2018

With the advantage of having a high strength to weight ratio, composite materials are frequently being implemented as alternatives to steel and aluminum in military vehicles. To perform satisfactorily, joined composite laminates on a vehicle must be able to absorb a significant amount of energy under high strain rate loading events such as ballistic impact. In this paper the dynamic behavior and failure modes of adhesively bonded S2-glass/epoxy laminate joints are investigated. For this experiment, two structural adhesives are selected for comparison: a brittle methacrylate and a more compliant epoxy. The tests are conducted on an in-house assembled gas-gun to achieve the high strain rates necessary to break the adhesive bonds in two configurations, Mode I and II. Results obtained from the ballistic impact tests are compared to quasi-static test results to emphasize the rate-sensitivity of the bonded joints. Irrespective of the material configuration, the failure load of the adhesively bonded joint is seen to increase with the loading rate. Overall, epoxy appears to be 35–50% stronger than methacrylate by most measures. Under bending loading (mode I), most cases exhibit some amount of damage within the composite surrounding the bonded area, demonstrating a fiber-tear failure rather than a cohesive failure. The failure strength of the composite joint is thus not always proportional to the adhesion strength of the adhesive due to the weakness of delamination of the composite material, especially when loaded through the thickness of the composite. As compared with metal adherends, the composites are shown to absorb three times more energy per unit area.
An Empirical Stretch Bending Failure Criterion for AHSS
Authors: Shih Hua-Chu , Gambon Taylor
Published: January 2018

The failure mechanism in stretch bending over a small die radius for Advanced High Strength Steels (AHSS), commonly referred as “shear fracture”, has rendered the Forming Limit Diagrams (FLD) fail to predict it based on the initiation of a localized neck. As shown in previous studies using a Stretch-Forming Simulator (SFS) and Bending Under Tension (BUT) test, shear fracture depends not only on the radius-to-thickness (R/T) ratio but also on the tension/stretch level applied to the sheet during bending. Although the stress-base empirical fracture limit criterion was developed for various AHSS grades, the fracture limit was not well implemented in the computer simulations to predict stretch bending fracture.

In this paper, the new developed experimental analysis is conducted on the modified bending under tension test to further investigate the stretch bending fracture mechanism under the production die condition. Various AHSS grades including DP590, DP780, DP980 and DP1180 are included in the study. Based on numerous experimental results, the maximum shear stress at failure, the thinning strain and strain gradient across the die radius are obtained for all test materials. Results demonstrate that the presence of the large strain gradient is the cause for fracture in stretch bending AHSS over a small die radius. The maximum shear stress at failure and the limit thinning strain on the die radius in the stretch bending condition are determined and used as the new fracture criteria, which can be easily implemented in the computer simulations.
Measurement of Electrical Properties of Sickle Cells From Electrical Impedance of Cell Suspension
Authors: Liu Jia , Qiang Yuhao , Du E.
Published: January 2018

Analysis of the electrical properties of a biological cell can provide useful information about its characteristic features, such as the intracellular composition, charge distribution and composition changes in cell membrane, as well as the extracellular environment. Electrical impedance spectroscopy of a cell suspension can be used to extract an average measure of the electrical properties of single cells. In sickle cell disease, the disease state of a sickle red blood cell is closely related to the intracellular hemoglobin composition and concentration. This study presents an electrical impedance measurement of sickle cell suspension with normal red blood cells as control. Electrical impedance spectra of cell suspensions are obtained in the range of 1000 Hz to 1MHz. Based on Maxwell’s mixture theory, average values of membrane capacitance and cytoplasm resistance of single cells are extracted for both normal and sickle blood samples. Comparing to traditional parallel-plate setup for cell suspension subjected to frequency sweep, this method requires low quantity of blood specimens and can be potentially valuable for patients that are already anemic.
Modeling Reichardt’s Formula for Eddy-Viscosity in the Fluid Film of Tilting Pad Thrust Bearings
Authors: Deng Xin , Weaver Brian , Watson Cori , Branagan Michael , Wood Houston , Fittro Roger
Published: January 2018

Oil-lubricated bearings are widely used in high speed rotating machines such as those used in the aerospace and automotive industries that often require this type of lubrication. However, environmental issues and risk-adverse operations have made water lubricated bearings increasingly popular. Due to different viscosity properties between oil and water, the low viscosity of water increases Reynolds numbers drastically and therefore makes water-lubricated bearings prone to turbulence effects. The turbulence model is affected by eddy-viscosity, while eddy-viscosity depends on wall shear stress. Therefore, effective wall shear stress modeling is necessary in producing an accurate turbulence model. Improving the accuracy and efficiency of methodologies of modeling eddy-viscosity in the turbulence model is important, especially considering the increasingly popular application of water-lubricated bearings and also the traditional oil-lubricated bearings in high speed machinery. This purpose of this paper is to study the sensitivity of using different methodologies of solving eddy-viscosity for turbulence modeling.

Eddy-viscosity together with flow viscosity form the effective viscosity, which is the coefficient of the shear stress in the film. The turbulence model and Reynolds equation are bound together to solve when hydrodynamic analysis is performed, therefore improving the accuracy of the turbulence model is also vital to improving a bearing model’s ability to predict film pressure values, which will determine the velocity and velocity gradients in the film. The velocity gradients in the film are the other term determining the shear stress. In this paper, three approaches applying Reichardt’s formula were used to model eddy-viscosity in the fluid film. These methods are for determining where one wall’s effects begin and the other wall’s effects end. Trying to find a suitable model to capture the wall’s effects of these bearings, with aim to improve the accuracy of the turbulence model, would be of high value to the bearing industry. The results of this study could aid in improving future designs and models of both oil and water lubricated bearings.
Multibody Dynamic Simulation of a Double ‘A’ Suspension Focusing on the Lower Control Arm Fatigue Life Analysis
Authors: Rodrigues L. P. , Silva R. C. , Oliveira A. B. S.
Published: January 2018

A vehicle suspension subsystem consists of springs, shock absorbers and linkages, which attach to the wheels and chassis. The interaction between vehicle suspension and road generates dynamic forces in the suspension subsystem. In fact, vehicles travel at variable speed suffering a wide spectrum of vibrations and, usually, road profiles describe the roughness of the pavement surface, which represent their elevation as a function of a distance traveled or time. Consequently, suspension subsystem undergoes complex loading history that never reaches a level sufficient to cause failure in a single application. This means that components may fail due to fatigue.

At this context a Double A suspension, which has two sets of linkages called lower and upper control arms, could fail by fatigue according to MBS and FEA.

Thus, this work aims to present a MBS analysis of a Double A suspension submitted to a random road profile using a multibody commercial software. The fatigue life analysis focus in the lower control arm (LCA).

For this, forces components (longitudinal, vertical and lateral force) and torques, composed by eleven loading history acting on pre-defined points at the LCA, characterize the response of the component in such a situation. In fact, forces computed by multibody simulations improve the FEA by providing better assessment of how they vary throughout the random profile. For FEA, a methodology is proposed to simplify the loads acting at this element and perform the fatigue analysis by finite element method, in which transient analysis was performed.

This work represents a secondary stage of a broader study concerning the proposition of a constant amplitude proportional loading road profile based on the fatigue life results obtained from the complex loading history. Thus, it is expected to obtain in future works a simple signal to reproduce in numerical simulations, especially in fatigue analysis, and in experimental tests.
A Computer Experiment Based Model for a Spirally-Wounded Lithium-Ion Cell
Authors: Li Chao , Pelegri Assimina A.
Published: January 2018

Based on previous numerical models of spirally-wounded lithium-ion cells and the coordinate transformation method, a new method to carry out real-time calculation and simulation to predict the temperature distribution within the cell is developed. Based on the coupling of heat equation and a pseudo two dimensional (P2D) physics-based electrochemical model, samples of input combinations covering the input space are collected as training data. Computer experiments to predict current source density and thus heat generation rate in the cell with Gaussian process are done to exam the validity of the method.
Numerical Investigation of the Drag of Rockets at Subsonic, Transonic and Supersonic Speeds
Authors: Steppert Michael , Epple Philipp
Published: January 2018

To compute the trajectory of a rocket the knowledge of the external aerodynamics and the resulting forces is essential. The drag coefficient is an important parameter in the computation of rocket trajectory in case of vertical ascent. For compressible flows, at subsonic and supersonic velocities, the drag coefficient is a function of the Reynolds number and of the Mach number. Both dimensionless numbers depend on the temperature, however, not in the same way. For that reason, the Mach number dependency and the Reynolds number dependency are different. Since in the atmosphere pressure and temperature are functions of the height, the drag of rockets is also dependent on the height of the rocket in the atmosphere.

In this work, the dependence of the drag on the shape of the rocket is investigated at different heights and velocities, i.e. Reynolds and Mach numbers. For this purpose, the historical rocket from Johannes Winkler, the first liquid propulsion rocket in Europe, and a modern rocket geometry were chosen and compared. These rockets were investigated numerically with the commercial Navier–Stokes solver STAR-CCM+.

A detailed analysis of the drag coefficient, split into friction, pressure and wave drag was performed at these heights, Mach numbers and Reynolds numbers for the different aerodynamic shapes and rockets. In particular on the transonic and supersonic range the shock wave system leading to the wave drag was analysed in detail. Graphs of the corresponding friction, pressure, wave and total drag coefficients as a function of the Reynolds and as a function of the Mach numbers at different heights and a detailed analysis of these results are shown for the two rockets, the historical and a modern one.
Promoting Life-Long Learning Skills in CAD Using the Peer-Generated Screencast Tutorials
Authors: Duan Chang , Peng Xiaobo , Yuan Tianyun , Yalvac Bugrahan , Ketsetzi Antonia , Lai Hing Ebony , Eseryel Deniz , Eyupoglu T. Fulya
Published: January 2018

To promote life-long learning skills in Computer-Aided Design (CAD) education, authors designed and implemented a student-centered instruction in the CAD courses. A quasi-experimental pre-and-post test research design was implemented. Experimental group students were asked to design screencast tutorials with their verbal explanations recorded. Students shared their screencast tutorials with their peers and provided feedback to each other’s video tutorials. Control group students were asked to review the instructor made screencast tutorials. A life-long learning survey, an engineering attitude survey, an exit project survey, and a CAD modeling exam were used as the study instruments. A total of 147 students participated in this study over three years. Findings indicated that female and first generation college students in the experimental group performed better than their peers in the control group in the CAD modeling exam. Our student-centered instruction was more affective on female students’ and first generation college students’ skills and knowledge than male students’ and not-first generation college students’ skills and knowledge.
Characterizing the High Reynolds Number Regime for Deterministic Lateral Displacement (DLD) Devices
Authors: Dincau Brian , Aghilinejad Arian , Kim Jong-Hoon , Chen Xiaolin
Published: January 2018

Deterministic lateral displacement (DLD) is a common name given to a class of continuous microfluidic separation devices that use a repeating array of pillars to selectively displace particles having a mean diameter greater than the critical diameter (Dc). This Dc is an emergent property influenced by pillar shape, size, and spacing, in addition to the suspending fluid and target particle properties. The majority of previous research in DLD applications has focused on the utilization of laminar flow in low Reynolds number (Re) regimes. While laminar flow exhibits uniform streamlines and predictable separation characteristics, this low-Re regime is dependent on relatively low fluid velocities, and may not hold true at higher processing speeds. Through numerical modeling and experimentation, we investigated high-Re flow characteristics and potential separation enhancements resulting from vortex generation within a DLD array. We used an analytical model and computational software to simulate DLD performance spanning a Re range of 1–100 at flow rates of 2–170 μL/s (0.15–10 mL/min). Each simulated DLD array configuration was composed of 60 μm cylindrical pillars with a 45 μm gap size. The experimental DLD device was fabricated using conventional soft lithography, and injected with 20 μm particles at varying flow rates to observe particle trajectories. The simulated results predict a shift in Dc at Re > 50, while the experimental results indicate a breakdown of typical DLD operation at Re > 70.
Modeling and Experimental Characterization of Viscoelastic 3D Printed Spring/Damper Systems
Authors: Lai Heather L. , Kuang Cuiyu , Nelson Jared
Published: January 2018

The development of flexible, viscoelastic materials for consumer 3D printers has provided the opportunity for a wide range of devices with damping behavior such as tuned vibration isolators to be innovatively developed and inexpensively manufactured. However, there is currently little information available about the dynamic behavior of these 3D printed materials necessary for modeling of dynamic behavior prior to print. In order to fully utilize these promising materials, a deeper understanding of the material properties, and the subsequent dynamic behavior is critical.

This study evaluates the use of three different types of models: transient response, frequency response and hysteretic response to predict the dynamic behavior of viscoelastic 3D printed materials based on static and dynamic material properties. Models of viscoelastic materials are presented and verified experimentally using two 3D printable materials and two traditional viscoelastic materials. The experimental response of each of the materials shows agreement with the modeled behavior, and underscores the need for improved characterization of the dynamic properties of viscoelastic 3D printable materials.
Design and Evaluation of Automated Robotic Ultrasonic Guided Wave Based Inspection System
Authors: Bland Scott M. , Joshi Shiv P.
Published: January 2018

This paper discusses the development and testing of an automated robotic ultrasonic guided wave based inspection system developed to provide an efficient, accurate and reliable method for performing nondestructive evaluation and longer term structural health monitoring in advanced composite structures. The development process and challenges in the design of the automated robotic system are described. A number of tests were performed using the developed robotic ultrasonic inspection system on composite honeycomb core sandwich materials. Experiments showed that the developed automated ultrasonic guided wave inspection system was successful at locating disbonds between the core and the facesheets. Environmental sensitivity testing was also performed to characterize the effect of changing temperature and humidity on system performance. These tests indicate that approach was relatively insensitive to environmental changes, so that this approach could be used in service environment without a significant reduction in performance. Current system testing indicates that the described robotic ultrasonic inspection approach offers an accurate and robust method for inspection and long term tracking of advanced structural system health.
Analysis of Two-Dimensional Kinetic Shape Systems
Authors: Handžić Ismet , Muratagić Haris , Rasouli Fatemeh , Reed Kyle B.
Published: January 2018

A Kinetic Shape has a physical and continuous curve with a changing radius that is exactly defined by its kinetic behavior. A Kinetic Shape curve is defined by specifying the force applied to the Kinetic Shape and the force with which the Kinetic Shape subsequently reacts at ground contact. This concept allows for predictable, position-dependent, and purely mechanical force redirection which make it broadly applicable. Kinetic Shapes have been previously used in several applications to predict the redirection of forces applied to the shape into ground reaction forces. Here, we analyze various ways 2D Kinetic Shapes interact and show how different mechanical force-based computational operations can be performed using these interconnected Kinetic Shapes, which we call Kinetic Shape Systems.
Investigation of Energy Absorption Characteristic of Ceramic Fiber Reinforced Elastomer Composites
Authors: Yasuda Nathan K. , Schulman David S. , Traina David J. , Mather Emily R. , Lane Kerry V. , Lo Michael E. , Weaver Kenneth D. , Shih Frank J.
Published: January 2018

Head protection from impact events for participants in contact sports or other activities is of current interest. Custom designed and synthesized material systems which effectively reduce the peak force transmitted to the individual and absorb a substantial portion of the impact energy are highly desirable. In applications in which recovery time of the material is not a primary concern, multiple means of energy absorption, including deformation and fracturing of the reinforcement material, may be suitable. In the present study, new composite material systems using a urethane elastomer matrix reinforced with glass and unidirectional carbon fiber rods were synthesized and subjected to compression loading along the fiber direction. The constituent fiber rods absorbed energy either through plastic deformation, buckling, or fracturing during compression loading. The effect of different reinforcement material, configuration, and length were physically tested. A cascading failure mode was achieved by embedding fibers of varying length in the matrix. This triggered successive failure events as the primary load was transferred from the longest rod to each successive shorter rod. The elastomer matrix was also experimentally characterized quasi-statically. A thin outer polymer layer further constrained the elastomer composite and allowed for fine adjustment and optimization of its crushing characteristics.
OCT-Based Three Dimensional Modeling of Stent Deployment
Authors: Dong Pengfei , Prabhu David , Wilson David L. , Bezerra Hiram G. , Gu Linxia
Published: January 2018

Stent deployment has been widely used to treat narrowed coronary artery. Its acute outcome in terms of stent under expansion and malapposition depends on the extent and shape of calcifications. However, no clear understanding as to how to quantify or categorize the impact of calcification. We have conducted ex vivo stenting characterized by the optical coherence tomography (OCT). The goal of this work is to capture the ex vivo stent deployment and quantify the effect of calcium morphology on the stenting. A three dimensional model of calcified plaque was reconstructed from ex vivo OCT images. The crimping, balloon expansion and recoil process of the Express stent were characterized. Three cross-sections with different calcium percentages were chosen to evaluated the effect of the calcium in terms of stress/strain, lumen gains and malapposition. Results will be used to the pre-surgical planning.
Dependency ECoG Band Spectrum in Epileptic Discharges Upon Local Cooling Rate on Brain
Authors: Uehara Kenyu , Saito Takashi
Published: January 2018

Focal brain cooling has recently drawn attention as a less-invasive treatment for intractable epileptic patients. The objective of this study is to investigate the dependence of brain cooling rate on epileptic discharges (EDs) suppression with experiments using four epilepsy model rat. EDs were induced by Penicillin G in anesthetized rat, and cooled to 16 °C under four different time conditions (30, 60, 100 and 200 second, respectively). The ECoG obtained from the experiments were sorted into frequency band components which have physiological significance. The results of frequency analyses confirmed that the suppression of EDs have a cooling rate dependency, and power of four frequency bands (delta, theta, alpha and beta waves) in EDs are smaller when the cooling rate is slower. Our results suggested that slower cooling on brain surface can effectively suppress EDs and rapid brain cooling is not necessarily the best way. This finding implied that there are optimum cooling condition depending on the degree of EDs or epileptic symptoms.
Thermal Energy Recovery From Small Sewage Treatment Plants in Northern Canadian Communities
Authors: Duan Xili , Haque Isa R. , Ducey Aloysius
Published: January 2018

This paper presents feasibility study and concept design of a thermal energy recovery system with an adsorption heat pump integrated with a small sewage treatment plant in northern Newfoundland communities. Treated fluids from the sewage treatment systems are quite warm even in winter. For example measured fluids temperature is averaged at 17 °C when air temperature is at −10 °C in the town of Whitbourne. This provides an attractive heat source particularly for winter seasons. Four heat pump concepts, i.e., vapour compression, absorption, adsorption and chemical heat pumps, were reviewed and compared. The results show that the adsorption system best fits the sewage treatment plants with minimum power requirements. Thermal fluidic parameters of the key components were designed with fluid flow and heat transfer analysis. A brief economic and environmental analysis showed that the integrated energy recovery unit would lead to a net reduction of CO2 emission and feasible payback time.
Research on the Impact of Feature-Based Model Simplification on CAE Simulation Results
Authors: Wang Qingmiao , Zhan Zhenfei , Yang Xin , Lu Jun
Published: January 2018

When solving real-world engineering problems, simplified models are commonly used to improve the calculation efficiency. However, the obtained simulation results are usually with low accuracy. Some researches are conducted to investigate the impact of feature-based model simplification on simulation results. First, models with similar features of different parameters are simplified. Then the simplified model and the corresponding original model are simulated in the same boundary conditions. And the simulation results between the simplified and original model are evaluated with some validation metrics. Finally, through an engineering case, some conclusions are obtained about the impacts of the features with different sizes and locations on simulation results.
A Finite Element Model of a Surgical Knot
Authors: Qwam Alden Arz Y. , Geeslin Andrew G. , King Jeffrey C. , Gustafson Peter A.
Published: January 2018

Background Surgical knots are one of several structures which can fail during surgical repair. However, there is no universal agreement on the superiority (best/safest) of one particular surgical knot technique. Tensile testing of repaired soft tissue has been used to assess the efficacy of surgical knot tying techniques, however, few computational models exist. The purpose of this study was to create a validated biomechanical model to evaluate the effect of knot configuration on the mechanical performance of surgical sutures.

Methods Two sutures were tested experimentally to find the mechanical properties and strength. Single throw knots were also tested for strength. Finite element models were constructed of each configuration and correlation was established.

Results The finite element results are quantitatively and qualitatively consistent with experimental findings. The FE model stress concentrations are also consistent with published strength reductions. Model and experimental results are presented using as-manufactured No. 2 FiberWire as well as its core and jacket constituents separately.

Clinical Relevance This paper describes a model which can evaluate the effect of knot topology on the mechanics of surgical suture. In the future, the model may be used to evaluate the mechanical differences between surgical techniques and suture materials. The findings may impact choices for suture and knot types selected for soft tissue repairs.
A DNS Study of Falling Droplets Under Effects of Electric Field
Authors: Ghasemisahebi Esmaiil , Bararnia Hassan , Soleimanikutanaei Soheil , Lin Cheng-Xian
Published: January 2018

In this study deformation and breakup of a falling drop which is surrounded by another liquid are modeled numerically. The drop is influenced by an external electric field which is applied uniformly on the side walls of the domain. An open-source volume-of-fluid solver, Gerris with dynamic adaptive grid refinement has been used for numerically modeling the three-dimensional deformation of a falling droplet. The numerical results are presented for various values of density ratios and electrical conductivity and permittivity. The current numerical results are compared with previous experimental and analytical works which shows a great agreement between them.
Analysis and Numerical Simulation of the Mechanical Performance of FDM Samples With Variable Infill Values
Authors: Cerda-Avila Steffany N. , Medellín-Castillo Hugo I. , de Lange Dirk F.
Published: January 2018

The prediction of the mechanical properties of AM parts is very important in order to design and fabricate parts not only of any geometrical shape but also with variable or customized mechanical properties. A limited number of investigations have focused on the analysis and prediction of the mechanical properties of AM parts using theoretical and numerical approaches such as the Finite Element Method (FEM); nevertheless, their results have been not accurate yet. Thus, more research work is needed in order to develop reliable prediction models able to estimate the mechanical performance of AM parts before fabrication.

In this paper the analysis and numerical simulation of the mechanical performance of FDM samples with variable infill values is presented. The aim is to predict the mechanical performance of FDM components using numerical models. Thus, several standard tensile test specimens were fabricated in an FDM system using different infill values, a constant layer thickness, one shell perimeter, and PLA material. These samples were measured and modelled in a CAD system before performing the experimental tensile tests. Numerical models and simulations based on the FEM method were then developed and carried out in order to predict the structural performance of the specimens. Finally the experimental and numerical results were compared and conclusions drawn.
Geometrical Effects of Channel Configuration on the Performance of Membraneless Fuel Cells
Authors: Gomez Hector , Tohid Usama , Pacheco-Vega Arturo
Published: January 2018

In this study, numerical simulations were performed to find the current-voltage distribution for a laminar flow-based membraneless fuel cell (LFFC). The system uses formic acid and oxygen as the fuel and oxidant, respectively, and has a Y-shaped geometry with two separate inlets that merge into a single channel. The main objective of this work is to analyze the impact of geometry and operating conditions on the performance of these devices. This is done by proposing a novel wavy-channel-based geometry for the side walls, along with planar top and bottom walls, and comparing the behavior of the corresponding system to that of LFFCs based on straight-channel walls. Special attention is placed on the effect of both the amplitude of the sinusoid and its wavelength on the performance of the device. The effect of flow rates — in the range of [200, 350] μL/min — is also studied. The mathematical model is formulated by considering the Navier-Stokes equations along with Butler-Volmer and Fick’s law. For each fuel-cell configuration, the governing equations are discretized and solved using finite elements, and the solutions given in terms of the polarization curves. The model was first verified using published numerical data for a straight-channel-based LFFC. The simulations show that the performance achieved by the device, based on the proposed wavy channel geometry, is slightly better than that of the LFFC with straight channel walls. On the other hand, higher flowrates significantly improve the power density of the device. Although the current mathematical model may be useful in a variety of applications, improvements on it are currently underway to account for the effects of potential distributions on ions within the flow channel, and results from it will be reported in the future.
Project-Based Learning: Microfluidic Lab-on-a-Chip Point-of-Care Medical Tests for Engineering Undergraduates
Authors: Mauk Michael G. , Chiou Richard Y. , Ruiz Carlos , Varapula Dharma , Liu Changchun , Song Jinzhao
Published: January 2018

Point-of-care (POC) medical diagnostics tests based on instrumented microfluidic chips are instructive and highly-multidisciplinary projects for undergraduate research and Senior Design. Students can apply their knowledge of fluid mechanics, heat transfer, optics, electronics and microcontrollers, materials, prototyping and systems engineering in translating and adapting a laboratory-based test for use in non-traditional venues. We discuss the design, prototyping, and testing of POC lab-on-a-chip (LOC) systems in an educational setting, where undergraduate students develop and demonstrate novel and practical POC tests. This application area serves as an effective gateway to the medical diagnostics field for engineering students, with opportunities for providing sustainable, appropriate, and ‘green’ technology to the developing world where healthcare infrastructure is lacking.