bluuebunny/crossref_metadata_2025 huggingface dataset:
New Expression for a Blanking Force Calculus of a Cospel Using a Die Matrix Angled
Authors: Garcia Zugasti Pedro de Jesus , Navarro Delgado José de Jesús , Medellín Castillo Hugo I. , Valdez Dávila Carlos , Sandoval Granja Juan Gabriel
Published: March 2016

Frequently it is desired to calculate the blanking shear force of a cospel using an angled matrix as main characteristics of the cutting die. There are two reasons that support the development of this calculation: the first is that the product may change its shape or material, which makes necessary to modify the operating parameters according to the geometric size and metal composition changes. The second is that the nominal capacity of the working press is established by the manufacturer and cannot be altered to adapt to a new product, this means that any new product parameters must be adapted to the capabilities of the machine. Also, the force equation must contain the main variables of the product and not just “proportions” or “factors”, allowing a better approximation of the cutting operation. In this work, a new expression for the blanking force calculus of a cospel is obtained, based on the geometric characteristics of the cutting die (punch and matrix). A matrix die angled is considered as a main characteristic of the sheet metal cutting die, maintaining the punch geometry without cut angles. Two formulas derived from analytical and graphical proposed methods are used and several blanking tests were conducted with a die designed and fabricated properly to run the laboratory tests. The graphical methods are based on a projected area of the metal cospel, obtained from the three dimensional cospel area to cut, this two dimensional projected area is utilized in the expression for the cutting force calculus. On the other hand, the analytical approach considers an area limited from a mathematical equation obtained from a model based on the geometry regions of the blanking die; this area has also utilized as the shear area in the cutting force calculus of a metal cospel. The experimental procedure consisted in reproduce the blanking operation of several metal cospels using the designed and fabricated die. The cutting force was measured using three different matrix die angles probed during the blanking tests, maintaining the same cut angle of the punch during the tests. The tests results were compared with both analytical and graphical methods showing good agreement. Similarly, the cutting force was calculated with analytical and experimental expressions obtained from the specialized literature in order to determine the degree of accuracy of the calculations.
Osmosis Process Development for Innovative Product Design and Validation
Authors: Agostinho Carlos , Marques-Lucena Catarina , Sesana Michele , Felic Artur , Fischer Klaus , Rubattino Cinzia , Sarraipa João
Published: March 2016

The emerging Liquid-Sensing Enterprise (LSE) concept provides to manufacturing enterprises the required enablers to modernize traditional strategies for product design and validation. The proposed osmosis processes integrates innovative processes and paradigms comprising a MDA/MDI based approach with the focus to potentiate the generation of technological innovations. These osmosis processes address the existing real, digital and virtual related data of specific products design supported by sensing assets to facilitate ready-to-run business processes, to then perform efficient product development and validation. This paper integrates model-driven techniques and runtime environments as well as novel form of information access and visualization for systems design and process development. The developments are accompanied with a real example from a manufacturing environment of engine camshafts.
Tensile Properties of Polylactic Acid (PLA) Additive Manufactured Parts
Authors: Cardenas Joselyn , Stewart Calvin M.
Published: March 2016

In the advancement of Additive Manufacturing (AM) technologies, 3D desktop printers have become an accessible solution to address the current manufacturing practices for most industries and the general public. This study explores the effect default build parameters have on the tensile properties of additive manufactured parts by comparing the Young’s Modulus and tensile strength of polylactic acid (PLA) in the elastic region before and after the AM process through experiments and numerical simulations. The build parameters are specified via MakerBot Desktop — the file preparation software for the MakerBot Replicator 3D printer used to create the specimens tested herein. This work presents the tensile mechanical properties for specimens built using low infill rate, low layer resolution, and standard build speed and extrusion temperature to recreate the worst possible part quality attainable using MakerBot 3D Desktop printers. Using these build parameters results in a part with a hollow honeycomb interior structure, and due to its heterogeneous cross sectional area, experimental stress-strain curves do not accurately represent its physical response to tensile loading. Therefore in this case, an experimental-numerical study of the 3D printed specimens is performed, using the load-displacement experimental data acquired from tensile tests to calibrate the ANSYS Structural Mechanics simulations. The goal is to optimize the material properties in our simulation such that the equivalent strain magnitude matches the experiments. This is an approach to determine the experimental Young’s modulus of PLA additive manufactured parts where the AM process, heterogeneous structure, and size greatly influence the part strength. This is completed by studying the worst part quality possible first to better understand this effect. Tensile tests are performed using an ADMET 5603 Universal Test Machine (UTM) synched with a Correlated Solutions 3D Digital Image Correlation (DIC) system. A fine heterogeneous speckle pattern is sprayed on the specimens and used by the DIC system to obtain surface contours of deformation. This data is compared to the displacement fields in the finite element analysis (FEA) simulation of the specimen.

When compared to the pre-manufacturing PLA, additive manufactured parts exposed that the post-processed stiffness of the material is increased when tested under this loading condition. The Poisson’s ratio for printed PLA was also noted to decrease when compared to pre-manufactured PLA, due to the larger longitudinal deformation compared to the transverse. Specimens failed by brittle fracture across the hex pattern, showing limited deformation and failing short after. The failure location based on the influence interior geometry has on failure showed that specimens failed by brittle fracture across the hex pattern, initiating fracture in the same region of all specimens.
Developing an Educational and Research Human Robot Interaction Environment for a Mechanical Finger/Hand
Authors: Ábrego Christopher E. , Shiakolas Panos S. , Sobhy Michael R.
Published: March 2016

Human robot interaction (HRI) has become a growing area of study due to the increasing application of robots in work environments and daily life and interact and work in tandem with human operators. This synergy between humans and robots have expanded human endeavors and motivated neoteric and prospective areas of robotics research.

The objective of this research is to develop an environment where both researchers and students can experience and experiment with different interaction modes with a robotic finger and hand. The acquisition and the post processing of environmental data from the hardware allow the user to envisage decision making algorithms.

The present HRI environments have both closed and open loop controlled interaction modes for research and demonstration purposes. The interaction modes include direct open loop manipulation, force threshold interaction, voice commands, and variable force close. This additionally demonstrates the ease in functionality and augmentation in the testbed. As a result of speech recognition test, the testbed has a 79% success rate and has a 90% success rate in the force threshold test. The manuscript will also describe how certain actions are performed based on Prime States. An overview of the state algorithms are described as well as decision making diagrams.
Boundary Layer Control of an Axial Compressor Cascade Using Nonconventional Vortex Generators
Authors: Diaa Ahmed M. , El-Dosoky Mohammed F. , Ahmed Mahmoud A. , Abdel-Hafez Omar E.
Published: March 2016

Boundary layer control plays a decisive role in controlling the performance of axial compressor. Vortex generators are well known as passive control devices of the boundary layer. In the current study, two nonconventional types of vortex generators are used and their effects are investigated. The used vortex generators are doublet, and wishbone. Three dimensional turbulent compressible flow equations through an axial compressor cascade are numerically simulated. Comparisons between cascade with and without vortex generators are performed to predict the effect of inserting vortex generator in the overall performance of the axial compressor. Results indicate that using vortex generators leads to eliminate or delay the separation on the blade suction surface, as well as the endwall. Furthermore, the effects of the vortex generators and their geometrical parameters on the aerodynamic performance of the cascade are documented. In conclusion, while the investigated vortex generators cause a slight increase in the total pressure loss, a significant reduction in the skin friction coefficient at the bottom endwall is found. This reduction is estimated to be about 46% using doublet and 32% using wishbone.
Spring-Follower-Cam Assembly for Muscular Training at Different Speeds
Authors: Amaral de Araújo Cleudmar , Siquieroli Warner Artur , Goulart Oliveira Sonia A. , Lourenço de Souza Fernando , Sartini de Oliveira Lidiane , Peres de Souza Márcio
Published: March 2016

Conventional equipment for muscular rehabilitation and training uses passive load systems. This work seeks the creation of an alternative resistance generation device for the skeletal muscle contraction to be applied in conventional machines of muscular training and physiotherapy. The proposed device uses a group spring-follower-cam to produce the resistance and does not use cables, belts or chains. The device was designed to generate mechanical resistance through low inertia set, accessibility, modular and low-cost to be adapted on training machines. This device consists of a cam-follower pair connected to a compression spring. Its operating principle is based on the pressure angle variation between the cam-follower pair. The mathematical modeling and the numeric solution for the cam profile is presented. It was noted that prototype can be applied in high speeds unlike conventional equipment. The maximum torque curve available and the torque curve obtained in the device approached, as the movement training approached motor gesture, with maximum errors of about 10 %. The results confirm that the device is capable of generating a resistance profile that resembles the maximum available torque profile at the joint user when performing certain movement training, which can more adequately represent the motor gesture to be trained. Two case studies were conducted using the motor gesture of judo training and rower’s movement which mainly uses elbow flexion.
Analytical Investigation of Vibration Attenuation With a Nonlinear Tuned Mass Damper
Authors: Dick Andrew J. , Atzil Aaron , Nagarajaiah Satish
Published: March 2016

Vibration attenuation devices are used to reduce the vibrations of various mechanical systems and structures. In this work, an analytical method is proposed to provide the means to investigate the influence of system parameters on the dynamic response of a system. The method of multiple scales is used to calculate an approximate broadband solution for a two degree-of-freedom system consisting of a linear primary structure and a nonlinear tuned mass damper. The model is decoupled, approximate analytical solutions are calculated, and then they are combined to produce the desired frequency-response information. The approach is initially applied to a linear two degree-of-freedom system in order to verify its performance. The approach is then applied to the nonlinear system in order to study how varying the values of parameters associated with the nonlinear absorber affect its ability to attenuate the response of the primary structure.
An Analytical Design Methodology for High Speed Nanopositioning Scanners
Authors: Sabade Vaibhav , Joseph Tim John , Kartik V.
Published: March 2016

An analytical methodology is presented for the systematic design of a serial kinematic flexure-guided high speed nanopositioning scanner. Approximate relations for the first natural frequency in different directions, achievable range, and in-plane cross-coupling between the axes are obtained considering each stage as a simple one-dimensional mass spring system. Parametric studies are performed to compare these characteristics for a particular range of flexure dimensions. The robustness of the design to manufacturing tolerances, and especially their influence on cross-coupling is investigated. The relations obtained are experimentally verified on a single-axis test system and the measured natural frequencies closely match analytical and FEA predictions. A two-axis nanopositioning system is designed, which has the fast and slow scanning axes’ resonances at 26.36 kHz and 5.28 kHz. The design is validated using finite elements, and the predicted actuation-direction resonances (25.5 kHz and 5.24 kHz respectively) closely agree with those found analytically.
Roll-Yaw Coupling Effect of Jeffcott Rotor With Breathing Crack
Authors: Zhao J. , DeSmidt H. A. , Peng M. , Yao W.
Published: March 2016

A new rotor model is developed in this paper to explore the dynamic coupling effect of roll-yaw motion. The rotor model employs a 6 degree-of-freedom Jeffcott rotor with a breathing crack. Based on the energy method and Lagrange principle, equation of motion is derived in yawing coordinate system with consideration of unbalance mass. The breathing crack model is established by Zero Stress Intensity Factor (SIF) method based on the crack released strain energy concept in fracture mechanics. SIF method is used to determine the crack closure line by computing SIF for opening mode. The vibration responses of the cracked rotor system are solved by Gear’s method. The coupling effect of yawing and rolling motion is studied in this paper to investigate vibration response of cracked rotor system. With the yawing motion, the dynamics of the rotor-bearing system is changed by additional stiffness and force terms. The parametric study is conducted to analyze the effect of yawing rate and acceleration on the crack breathing behavior. Finally, the vibration responses of the nominal and damaged rotor systems are analyzed to find out the indication for the damage detection and health monitoring.
Influence of Surface Energy in the Osteogenesis Process of Treated Titanium Surfaces
Authors: Sartini de Oliveira Lidiane , Amaral de Araújo Cleudmar , Lourenço de Souza Fernando , Mendonça Gustavo , Mendonça Daniela B. S. , Goulart Oliveira Sonia A.
Published: March 2016

In the 1960’s, Brånemark and colleagues developed a dental implant system using a direct attachment to bone structure without generating soft tissue. This phenomenon called osseointegration involves biomechanical behavior of materials. In several studies it has been verified that the surface treatment on titanium implant has been the main factor for the osteogenesis process and, consequently, osseointegration [1, 2, 3]. Treated titanium surfaces have better conditions for cell adhesion that can lead to load application in the shortest time.

The aim of this study was to evaluate the surface energy and the cell osteogenesis on titanium discs under different conditions of blasting and acid attack. Osteoblastic cells Hfob 1.19 were used to measure cell culture parameters like cell viability and cell proliferation, alkaline phosphatase activity and mineralized nodule formation. Osteogenesis cell was defined through a mathematical model proposed by a similitude in engineering with osteogenic parameters analyzed in culture cells.

Fowkes Theory was used to calculate the surface energy by measuring contact angles between liquid sensors (Deionized Water, Chloroform) on different titanium surfaces.

Significant difference (P < 0,01) was observed for surface energies ranging between 26,76 a 33,81 mJ/m^2 using ANOVA and Bonferroni test. It was noted that the highest surface energies are related with osteogenesis levels.
Research on the Piezoelectric Ultrasonic Actuator Applied to SFSS
Authors: Tang Y. J. , Yang Z. , Wang X. J. , Wang J.
Published: March 2016

This paper presents an investigation of a novel linear-type piezoelectric ultrasonic actuator for application in a Smart Fuze Safety System (SFSS). Based on the requirements of SFSS, the structural parameters of the proposed piezoelectric ultrasonic actuator are determined by fuze arming mode. Moreover, sensitivity analysis of the structural parameters to the frequency consistency is conducted using FEM software, after which the optimal dimensions are obtained with two close natural vibration frequencies. To validate the results of FEM, the frequency sweep tests of the piezoelectric ultrasonic actuator are performed to determine the motor’s actual working mode frequencies with PSV-300-B Doppler laser vibrometer system. Furthermore, the results of frequency sweep test are compared with that of the finite element analysis, and further verified by impedance analyzer. To investigate the overall performance of the piezoelectric ultrasonic actuator, vibration modes of actuator’s stator, output speed and force of the piezoelectric ultrasonic actuator are tested. The experimental results show that the output speed and force of the actuator can reach 88.2 mm/s and 2.3N respectively, which means that piezoelectric ultrasonic actuator designed in this paper can meet the demands of the SFSS.
Vortical Features of a Rotor Blade in Reversed Flow
Authors: Shukla Dhwanil , Hiremath Nandeesh , Komerath Narayanan
Published: March 2016

The nature of the flow around a rotating blade in reverse flow is described, integrating results from fixed and rotary wing experiments. The highly 3-dimensional flow phenomena do not conform to expectations based on 2-D airfoil aerodynamics. Fixed-wing results from load measurements and flow visualization showed that the sharp-edge vortex (SEV) is a primary feature when the blade is yawed either forward or backward. The loads are better modeled using the Polhamus leading edge suction analogy. Vortex-induced pressure gradient induces an inward radial flow overcoming centrifugal effects, but away from the vortex, outward radial flow is evident everywhere. A strongly three-dimensional and attached SEV is evident under the blade at 240 degrees azimuth. This detaches and convects with the flow, remaining close to the blade by 270 degrees. The vortex seen at 300 degrees is clearly detached, but growth of the core diameter corresponding to vortex bursting, causes strong suction under the blade. The flow around the blunt edge is again strongly 3-D. Some evidence of intermittent separation is seen, but the azimuth-resolved, ensemble-averaged flow is mostly attached around the blunt edge. Preliminary static pressure contours derived from the measured 3-component velocity field are presented.
Analysis of the Thermoacoustic Flame Instability With Proper Orthogonal Decomposition
Authors: Zhang Jianan , Ratner Albert
Published: March 2016

Lean premixed combustion technology is a method that can inhibit the NOx emission by decreasing the flame temperature. Nevertheless, lean combustion systems are more sensitive to acoustic oscillations than rich systems. As a result, thermoacoustic instability, which is caused by the coupling between pressure and heat release rate oscillations, could causes serious device failure in the lean operating systems. A common mechanism that can trigger thermoacoustic instability is the flame-vortex interaction. The vortices forming in the shear layer can directly affect the energy exchange between combustion and the pressure field. Flame structure can experience significantly spatial change with the effect of the vortex. Therefore, this is essential to obtain the local heat release rate information to understand the global flame behavior. To capture the local information of the flame, planar laser induced fluorescence of OH radicals (OH-PLIF) was used to obtain the flame surface density (FSD), which is directly related to the local mean heat release rate. However, interruptions from the turbulent flow makes the raw local FSD data are difficult to be analyzed, especially when the acoustic perturbation level is low. To overcome this problem, the proper orthogonal decomposition (POD) method was used in the current research to analyze the FSD data to capture the dominant trend of the flame oscillation. The POD method was applied to a 5 m/s premixed low swirl flame forced by different levels of acoustic perturbation. After the dominant POD modes that contain most of the oscillation energy were obtained, they were used to reconstruct FSD results. By comparing the FSD results gained with and without POD method, it can be concluded that the dominant modes of POD can reasonably capture the key features of the heat release rate oscillation. Analysis results demonstrate that the POD method is a good candidate that can be applied to unstable combustion study to capture the dominant global and local heat release rate oscillation information, which is essential in understanding the thermoacoustic instability.
Undergraduate Senior Design: A Viable and Sustainable Mechanism to Solve Industrial Projects in Mechanical Engineering
Authors: Kumpaty Subha , Mahinfalah Mohammad
Published: March 2016

In collaboration with a local industry, Rexnord Technologies, mechanical engineering undergraduate students at the Milwaukee School of Engineering have undertaken a series of senior design projects to solve practical problems in thermal engineering. A team of four students are working on Gearbox oil immersion heater control. This team is developing a control scheme to preheat the oil prior to gear movement and that which will ensure that the heater turns off at the correct time so as to maintain the oil temperature in V-series gearboxes. Another team of four students is tackling Gearbox forced convection heat dissipation-modeling and optimization. The beneficial effects of university-industry alliance and the development of well-rounded engineers are discussed along with the solutions for the specific projects. Assessment results highlighting the impact of senior design in the overall undergraduate curriculum are also be presented in this paper. The senior exit surveys also provide the premium value on senior design experience and industry involvement. The goal of this paper is to give the audience a taste of the senior design opportunities undergraduates have at the Milwaukee School of Engineering highlighting the Rexnord Technologies-sponsored projects and the role of industry collaboration.
An Analysis of Variation Correlating Post Processing Infiltrate Types, Build Parameters and Mechanical Characteristics for Binder Jet Built Parts
Authors: Impens David , Urbanic Ruth Jill
Published: March 2016

The 3D Printing (3DP) “binder jetting” process is an additive manufacturing process that fabricates components and assemblies by layering powered material, and applying a binder where a ‘solid interior’ should be. This process creates brittle components as a powder is set with a weak binder material; however, the component strength characteristics can be significantly modified when infiltrating the component during post processing operations. The different factors that can influence the mechanical properties when engaging in post-processing operations need to be understood. A full factorial design of experiments (DOE) is conducted for tensile, compressive, and flexural specimens for 10 infiltrate and various build conditions. The experiment and resultants are set up to perform an analysis of variance (ANOVA). All of the observed stress-strain curves for the specimens are non-linear, or have limited linear regions. The infiltrate absorption depth affects the mechanical characteristics, and the binder jetting specimens are stronger in compression than tension. The tensile test results are similar to those of biological materials. Certain infiltrates do not improve the mechanical performance characteristics, which are validated using the Tukey method. This research needs to be extended in scope to include additional build orientations as well as torsion, fatigue, and notch tests to be able to predict model sensitivities effectively for components built using the binder jetting process, and to develop optimization strategies, which include time, material, and strength conditions.
Investigation on Temperature Control Model of the Focal Cooling Human Physiological System
Authors: Uehara Kenyu , Ukida Yasumi , Murakami Takahiro , Mori Koji , Saito Takashi
Published: March 2016

For efficient temperature control of the cooling device for medical purposes, accurate modeling of the focal cooling system taking into account the human physiological reaction and nonlinearity of the thermoerectric device, is required. In this paper, we examined about model parameters identification in order to establish a mathematical model for a focal cooling device for a living body using a Peltier device. Cooling experiments applied input constant voltage were performed to identify the model parameters. The temperature response data are obtained for every 0.1V, from 0.1V to 1.8V. As a result of the parameters identification, it was shown that some unknown parameters vary with a certain tendency to the input voltage. As a result of comparison between simulation value using identified parameters and experimental value, it was shown that one can simulate results in the error range of the parameter identification in the control surface.
Computer-Aided Modeling and Prototyping in Manufacturing Automation
Authors: Bzymek Zbigniew M. , Hagewood Aaron , Kosovay Dimitriy , Mealy Thomas , Summers Mark
Published: March 2016

The Manufacturing Automation course in a standard engineering education prepares students for the most contemporary production and technology challenges. This paper describes Rapid Prototyping and Modeling done as subtractive and additive manufacturing operations in the scope of the UConn Engineering program, as well as its integration into the Manufacturing Automation course. It is a companion paper with IMECE 2014-38355 [1] that reports how students of Manufacturing Automation are exposed to rapid prototyping. This is done in the UConn School of Engineering Machine Shop, Mechanical Engineering Machine Shop and Laboratory of the desk top modelers. Some experience students gain also in MEM Prototyping Laboratory and during class trips to Pratt & Whitney/ UConn Additive Manufacturing Research Laboratory and to CNC Software Inc Experimental Testing Shop. One of the objectives of the course is to introduce students to the processes of advanced Subtractive and Additive Manufacturing (SM and AM). The CAD/CAM cutting software such as CAMM-3 Micromodeler, G-code and Mastercam were used successfully in those operations. The elements of CAD/CAM software were integrated in the model cutting exercises. Full automation of integrated design and manufacturing data exchange was attempted but was found still not possible to accomplish. However the use of automation software in a sequence, tin tandem with data export and import, marks a significant step forward towards integrated manufacturing automation. The research to accomplish the next level of automation will be continued and the results will be applied to reinforce the teaching and practice of Manufacturing Automation. Significant role in helping students to understand the methods of subtractive and additive manufacturing has cooperation with two Connecticut companies that achieved outstanding results in modeling and prototyping. These are Pratt & Whitney in East Hartford and CNC Software Inc in Tolland, Connecticut. The class visits to their facilities and experience with their equipment played a significant role in understanding of the subtractive and additive machining processes. Efforts to introduce students to the concepts of subtractive and additive machining process are described. Conclusions about the teaching methods of product machining concepts and lessons learned are pointed out.
Virtual Simulation of the Effects of Intracranial Fluid Cavitation in Blast-Induced Traumatic Brain Injury
Authors: Haniff Shivonne , Taylor Paul , Brundage Aaron , Burnett Damon , Cooper Candice , Gullerud Arne , Terpsma Ryan
Published: March 2016

A microscale model of the brain was developed in order to understand the details of intracranial fluid cavitation and the damage mechanisms associated with cavitation bubble collapse due to blast-induced traumatic brain injury (TBI). Our macroscale model predicted cavitation in regions of high concentration of cerebrospinal fluid (CSF) and blood. The results from this macroscale simulation directed the development of the microscale model of the superior sagittal sinus (SSS) region. The microscale model includes layers of scalp, skull, dura, superior sagittal sinus, falx, arachnoid, subarachnoid spacing, pia, and gray matter. We conducted numerical simulations to understand the effects of a blast load applied to the scalp with the pressure wave propagating through the layers and eventually causing the cavitation bubbles to collapse. Collapse of these bubbles creates spikes in pressure and von Mises stress downstream from the bubble locations. We investigate the influence of cavitation bubble size, compressive wave amplitude, and internal bubble pressure. The results indicate that these factors may contribute to a greater downstream pressure and von Mises stress which could lead to significant tissue damage.
2D and 3D Multiscale Computational Modeling of Dynamic Microorgan Devices as Drug Screening Platforms
Authors: Tourlomousis Filippos , Chang Robert C.
Published: March 2016

The ability to incorporate three-dimensional (3D) hepatocyte-laden hydrogel constructs using layered fabrication approaches into devices that can be perfused with drugs enables the creation of dynamic microorgan devices (DMDs) that offer an optimal analog of the in vivo liver metabolism scenario. The dynamic nature of such in vitro metabolism models demands reliable numerical tools to determine the optimum process, material, and geometric parameters for the most effective metabolic conversion of the perfused drug into the liver microenvironment. However, there is a current lack of literature that integrates computational approaches to guide the optimum design of such devices. The groundwork of the present numerical study has been laid by our previous study [1], where the authors modeled in 2D an in vitro DMD of arbitrary dimensions and identified the modeling challenges towards meaningful results. These constructs are hosted in the chamber of the microfluidic device serving as walls of the microfluidic array of channels through which a fluorescent drug substrate is perfused into the microfluidic printed channel walls at a specified volumetric flow rate assuring Stokes flow conditions (Re<<1). Due to the porous nature of the hydrogel walls, a metabolized drug product is collected at the outlet port. A rigorous FEM based modeling approach is presented for a single channel parallel model geometry (1 free flow channel with 2 porous walls), where the hydrodynamics, mass transfer and pharmacokinetics equations are solved numerically in order to yield the drug metabolite concentration profile at the DMD outlet. The fluid induces shear stresses are assessed both in 3D, with only 27 cells modeled as single compartment voids, where all of the enzymatic reactions are assumed to take place. In this way, the mechanotransduction effect that alters the hepatocyte metabolic activity is assessed for a small scale model. This approach overcomes the numerical limitations imposed by the cell density (∼1012 cells/m3) of the large scale DMD device. In addition, a compartmentalization technique is proposed in order to assess the metabolism process at the subcellular level. The numerical results are validated with experiments to reveal the robustness of the proposed modeling approach and the necessity of scaling the numerical results by preserving dynamic and biochemical similarity between the small and large scale model.
Low Velocity Impact Testing of Laminated Carbon Fiber/Carbon Nanotube Composites
Authors: Christoph Jake E. , Gregg Colin M. , Raney Jordan R. , Jack David A.
Published: March 2016

Carbon fiber laminated thermoset composites have become the industry standard for applications dictating a high strength-to-weight ratio. However, the brittle nature of the carbon fiber composite structure limits its energy dissipation characteristics, often leading to catastrophic failure under low energy impact loadings. This research examines the potential effects of including vertically aligned multi-walled carbon nanotube forests within a layered laminate structure with the goal being to increase the energy dissipation of the structure with attention given to the increase in the aerial density as a result of including the insert. These nanotube forests are of interest due to their broader application in coupled scenarios requiring tenability of structural, thermal and electrical properties. These nanotube forests have unique energy dissipative effects due to their hierarchical architecture (see e.g., Dario et al. (2006), Zeng et al. (2010) and Raney et al. (2011)). We synthesize vertically aligned nanotubes (VACNTs) on a single crystalline silicon wafer. After separation with the wafer, the VACNTs are placed within a carbon fiber laminated structure prior to resin infusion using vacuum assisted resin transfer molding (VARTM). Drop tower tests similar to ASTM D7136 are performed on carbon fiber laminates, carbon fiber laminates with nanotube forests, and carbon fiber laminates with several alternative materials. Results show an improved damage tolerance of the laminate with each of the investigated inserts, with the CNT system showing an increase of 13% in mean peak force. These results show a similar improvement to the alternative inserts while maintaining the potential for their broader application as a multifunctional material.
Failure Analysis in Hybrid Composite Laminates Using Acoustic Emission and Microscopy
Authors: Bourchak Mostefa , Dobah Yousef , Algarni Abdullah , Khan Adnan , Ahmed Waleed K.
Published: March 2016

Fiber Reinforced Plastic (FRP) composite materials are widely used in many applications especially in aircraft manufacturing because they offer outstanding strength to weight ratio compared to other materials such as aluminum alloys. The use of hybrid composite materials is potentially an effective cost saving design while maintaining strength and stiffness requirements. In this work, Woven Carbon Fibers (WCFs) along with Unidirectional Glass Fibers (UDGFs) are added to a an aerospace-rated epoxy matrix system to produce a hybrid carbon and glass fibers reinforced plastic composite plates. The manufacturing method used here is a conventional vacuum bagging technique and the stacking sequence achieved consists of a symmetric and balanced laminate (±451WCF, 03UDGF, ±451WCF) to simulate the layup usually adopted for helicopter composite blades constructions. Then, tensile static tests samples are cut according to ASTM standard using a diamond blade and tested using a servohydraulic test machine. Acoustic Emission (AE) piezoelectric sensors (transducers) are attached to the samples surface using a special adhesive. Stress waves that are released at the moments of various failure modes are then recorded by the transducers in the form of AE hits and events (a burst of hits) after they pass through pre-amplifiers. Tests are incrementally paused at load levels that represent significant AE hits activity which usually corresponds to certain failure modes. The unbroken samples are then thoroughly investigated using a high resolution microscopy. The multi load level test-and-inspect method combined with AE and microscopy techniques is considered here to be an innovation in the area of composite failure analysis and damage characterization as it has not been carried out before. Results are found to show good correlation between AE hits concentration zones and the specimens damage location observed by microscopy. Waveform analysis is also carried out to classify the damage type based on the AE signal strength energy, frequency and amplitude. Most of the AE activity is found to initiate from early matrix cracking that develops into delamination. Whereas little fiber failure activity has been observed at the initial stages of the load curve. The results of this work are expected to clear the conflicting reports reported in the literature regarding the correlation of AE hits characteristics (e.g. amplitude level) with damage type in FRP composite materials. In addition, the use of a hybrid design is qualitatively assessed here using AE and microscopy techniques for potential cost savings purposes without jeopardizing the weight and strength requirements as is the case in a typical aircraft composite structural design.
Forecasting Subcritical and Supercritical Flutter Using Gust Responses
Authors: Ghadami Amin , Epureanu Bogdan I.
Published: March 2016

This work presents a unique method to forecast flutter (Hopf) bifurcations based on observations of the system only in the pre-bifurcation regime. New techniques are introduced in to enhance prediction accuracy for both low-frequency oscillations and large-dimensional dynamical systems. The method is applied to an aeroelastic system using its response to gust loads. Numerical results demonstrate that the method can predict the post-bifurcation regime accurately for both supercritical and subcritical flutter.
Unsteady Lift for the Wagner Problem of Starting Flow at Very Large Angle of Attack
Authors: Li Juan , Bai Chen-Yuan , Wu Zi-Niu
Published: March 2016

A total vortex force line (TVFL) method has been proposed recently which is capable of studying and understanding the unsteady lift force behavior of inviscid starting flow of a flat plate at an angle of attack (AoA) up to 20 degree. The role of additional leading and trailing edge vortices on the Wagner lift curve has been correctly analyzed. In this paper we consider starting flow at much higher AoAs. By comparing with CFD simulations, we find that the TVFL method, derived originally for lift, predicts well the normal force for large angle of attack up to 40 degree. The oscillatory behavior of the normal force is related to leading and trailing edge vortices in a similar way as the lift oscillation for lower angle of attack. It is shown that apart from the initial singularity, the peak value of the normal force coefficient does not exceed a value around 3. Since the TVFL method can clearly identify the origins of lift increasing or decreasing mechanisms due to vortices, the correct prediction of the normal force for large AoAs means that this method can be used to study flapping flight problems.
Robust Optimal Trailing-Edge Flaps for Helicopter Vibration Reduction for Various Flying Conditions
Authors: Kizhakke Kodakkattu Saijal , Nair Prabhakaran , Joy M. L.
Published: March 2016

This paper aims to find a robust optimal design for twin trailing-edge flap for helicopter vibration reduction for various flying conditions with minimum flap power requirement. The objective is to find the optimum length and locations of twin trailing-edge flaps to minimize hub vibration in the helicopter with minimum flap power requirement and to evaluate the robustness of these optimum at various flying conditions such as advance ratio and thrust to solidity ratio. Polynomial response surface metamodels is used to approximate the hub vibration and flap power objective functions for optimization. Firstly, a single objective optimization minimizing hub vibration alone is carried out without considering the flap power requirement. A multi-objective optimization minimizing vibration and flap power is also carried out to explore the possibility of a compromise design of trailing-edge flaps. This optimization finds the robust optimal length and locations of twin trailing-edge flaps with the objective of minimizing hub vibration for various flying conditions. Result shows that a flap length of 9 percentage of the rotor is the optimum giving 55 percentage reduction in hub vibration compared to the baseline values. The corresponding inboard and outboard flap positions are 0.61R and 0.87R respectively. The robustness of these design solution with flying conditions such as advance ratio and thrust to solidity ratio are also explored.
Effect of Tool Shape on Surface Finish of Components Formed Through Incremental Sheet Forming Process
Authors: Kumar Pavan , Priyadarshi Satwik , Roy J. J. , Samal M. K. , Jain P. K. , Tandon Puneet
Published: March 2016

This work explores the effect of tool geometry on surface finish in incremental sheet forming (ISF) process. In the present work, two different tool geometries i.e. hemispherical shaped tool and ellipsoidal shaped tool are considered. Area at tool-sheet contact and scallop height were calculated for both the tool geometries. To assess the effect of tool geometry on the surface finish of the formed components, both analytical and experimental approaches have been used. A test geometry having the shape of frustum of pyramid was considered for the proposed investigation and four surface roughness parameters i.e. arithmetic mean surface roughness (Ra), root mean square surface roughness (Rq), maximum peak-to-valley height (Rt) and average peak-to-valley height (Rz) have been selected as response parameters. Based on the analytical model and experimental investigations, both qualitative and quantitative comparisons had been made among the effects of hemispherical and ellipsoidal tool geometries on surface finish. The investigation deduces that better surface finish of the formed component can be achieved by using ellipsoidal shaped tool rather than the hemispherical shaped tool.
MAAT Cruiser/Feeder Airship Design: Intrinsic Stability and Energetic Flight Model
Authors: Trancossi Michele , Dumas Antonio , Cimarelli Andrea , Pascoa Jose
Published: March 2016

Airships are expected to have in future an increasing diffusion in the aeronautic scenario. The use of airships is not necessary expected to be the same proposed in the past. Several new uses will assume a relevant importance in the next 20 years. The resurgence of airships has created a need for dynamics models and simulation capabilities of these lighter-than-air vehicles. A theoretical framework for designing flexible airships has developed deriving the equations for determining the flight behavior of an airship directly form the data of wind tests and CFD simulations. This model has been a fundamental part of the final design activities of the MAAT (Multibody Advanced Airship for Transport) EU FP7 project, which has studied an innovative cruiser feeder airship based transport system. Main results relates to the definition of a specific mathematical model, which allow approximating the behavior of a flexible or low structured semi rigid airship in presence of external oscillations, in pitch or yawing. Different shapes of airships with different shapes, also not conventional, are assumed and aerodynamic behavior has been evaluated when slightly disturbed from steady forward motion or from hovering conditions in presence of an impacting wind. New uses and the exigency of adopting photovoltaic energy for long endurance missions, is producing airship shapes, which are slightly different from traditional Parsifal.

The model presents defines effective criteria based on constructal law, which allow designing an airship with an intrinsic stability in pitch and yaw. An approximate condition for a dynamically stable motion, such as unamplifying pitch, has been expressed in familiar aerodynamic quantities. These results allow stating the following theorem, which has been demonstrated: “Stable pitch flight conditions can be ensured if damping moment is in rotational equilibrium with the disturbing moment and if the disturbing force, the damping force, and the inertia force, are in translational balance”. If pitch angle and angular speed are small it can be obtained a relation that must be necessarily satisfied for ensuring a stability condition. An effective flight model based on energetic model of flight is also produced and results have been compared with traditional models giving a good accordance in terms of results.
Toward an Affordable Automation Scheme of Friction Stir Processing
Authors: Ammouri A. H. , Hamade R. F.
Published: March 2016

Friction stir processing (FSP), an offshoot from friction stir welding (FSW), is an intricate operation that involves refining the material by a rotating tool. Active control of the resulting size and distribution uniformity of grain structure is desirable. Achieving such a control across the processed area requires real-time control of the process input variables in order to control the pertinent state variables (e.g., temperature, strain, and strain rate) throughout the process. Many active control schemes typically used in friction stir processes (such as position-, speed-, force-, and torque-control schemes) require the utilization of dynamometers to provide feedback to the control loop. Many drawbacks are associated with such utilization including the complexity of the required instrumentation and control systems. Another complexity is the required rigidity of the machine tool needed to perform friction stir processes.

In this work, we advance the notion of eliminating the usage of dynamometers by using the readily available motor current signals from the NC machine tool in the computer numeric control (NC) machines. This approach would drastically reduce the cost of FSP machine retrofitting. Presented in this work are guidelines for the implementation of affordable automation of CNC milling machines to perform friction stir processes. The guidelines are demonstrated by retrofitting a vertical machining center with current transducers to replace the usage of a dynamometer. The current transduces were tapped on the output of the drivers of the spindle and the z-drive motors. A custom LabVIEW software program was developed to control the machining center via direct numeric control mode and to monitor current signals which were in turn, correlated to the generated forces.

To demonstrate the methodology, friction stir processing was performed on magnesium alloy sheets for a wide range of process parameters. The tool rotational speed was varied from 600 RPM to 2000 RPM and the traverse feed from 75 mm/min to 900 mm/min. Current signals were monitored during frictions stir processing and were related to the process forces which were measured using a 4-component dynamometer. Linear relations between thrust force and torques with current signals of the spindle and the z-drive motors were established and the signal to noise ratio for each correlation was investigated.

It was found that the current spindle signals are highly correlated to the process torque where results can be used in a torque control loop without the need for expensive dynamometers. To a lesser extent was the correlation satisfactory between thrust force and z-drive motor signal due to bad signal to noise ratio.