bluuebunny/crossref_metadata_2025 huggingface dataset:
Circular Cylinder Drag Reduction By Three-Electrode Plasma Symmetric Forcing
Authors: D'Adamo Juan , Leonardo Leandro , Castro Federico , Sosa Roberto , Duriez Thomas , Artana Guillermo
Published: February 2017

This study reports an efficient reduction of the drag exerted by a flow on a cylinder when the former is forced with a plasma actuator. A three-electrode plasma device (TED) disposed on the surface of the body is considered, and the effect of the actuation frequency and amplitude is studied. Particle image velocimetry (PIV) measurements provided a detailed information that was processed to obtain the time-averaged drag force and to compare the performances of TED actuator and the canonical dielectric discharge barrier actuator. For the Reynolds number considered (Re = 5500), excitations with the TED actuator were more efficient, achieving drag reductions that attained values close to 40% with high net energy savings. The reduction of coherent structures using the instantaneous vorticity fields and a clustering technique allowed us to gain insight into the physical mechanisms involved in these phenomena. This highlights that the symmetrical forcing of the wake flow at its resonant frequency with the TED promotes symmetrical vorticity patterns which favor drag reductions.
Impact of Hydrofoil Material on Cavitation Inception and Desinence
Authors: Amromin Eduard
Published: February 2017

Flow-induced vibration of hydrofoils affects pressure pulsations on their surfaces and influences cavitation inception and desinence. As these pulsations depend on the hydrofoil material, cavitation inception and desinence numbers for hydrofoils of the same shape made from different metals can be substantially different. This conclusion is based on the comparison of the multistep numerical analysis of fluid–structure interaction for hydrofoils Cav2003 with earlier obtained experimental data for them. The material impact on cavitation must be taken into account in future experiments.
The Topology of a Precessing Flow Within a Suddenly Expanding Axisymmetric Chamber
Authors: Chen Xiao , Tian Zhao F. , Kelso Richard M. , Nathan Graham J.
Published: February 2017

A comprehensive study on the flow structure of an ensemble-averaged fluidic precessing jet (FPJ) flow is reported. This study is based on the concepts of critical point theory, previous experimental data, and validated simulation results. The unsteady k–ω shear stress transport (SST) turbulence model was adopted for the simulation, which provided high resolution flow details. The numerical model successfully reproduced the four main flow features of the FPJ flow. The predicted equivalent diameter and the centerline velocity of the phase-averaged FPJ flow were compared against the measured results and achieved reasonable agreement. The streamlines, velocity, and vorticity contours in a series of cross-sectional planes are presented. The calculated streamlines at the surfaces of the nozzle and the center-body (CB) are compared with previously deduced surface flow patterns. With these methods, a vortex skeleton with six main vortex cores of the FPJ flow within the nozzle is identified for the first time. This skeleton, which is illustrated diagramatically, is deduced to be responsible for the jet precession.
Microtexturing Into AISI-SUS420 Molds for Injection Molding Via Plasma Nitriding
Authors: Aizawa T. , Suga H. , Nagata T. , Yamaguchi T.
Published: February 2017

The initial microdot and microline patterns were first ink-jet printed onto the surface of polished AISI420 stainless steel mold. This masked mold substrate was nitrided at 693 K for 7.2 ks at 70 Pa by using the high-density plasma nitriding system. The unmasked parts were selectively nitrided to have higher hardness than 1200 HV. This hardness-profiled substrate was mechanically sand-blasted to fabricate the microtextured mold. Microdisk patterned plastic cover-case for cellular phones were injection-molded by using this method for practical demonstration. Both the selective hardening and anisotropic inner nitriding processes were experimentally discussed as a key step in the present processing.
A Novel Hybrid Heating Method for Mechanical Testing of Miniature Specimens at Elevated Temperature
Authors: Li Lin , Ngaile Gracious , Hassan Tasnim
Published: February 2017

A novel hybrid heating method which combines the conventional electric-resistance specimen heating with microcoil heating of specimen ends to achieve uniform heating over the gauge length is presented. Resistive heating of a miniature specimen develops a parabolic temperature profile with lowest temperature at the grip ends because of the heat loss to the gripper. Coil heating at the specimen ends compensates for this heat loss resulting in uniform temperature distribution over the central segment of the specimen. Thermo-electric finite element simulations were carried out to analyze the transient and steady temperature distribution in miniature specimens followed by experimental validation.
Effect of Reprocessing on the Rheological, Electrical, and Mechanical Properties of Polypropylene/Carbon Nanotube Composites
Authors: Stan Felicia , Sandu Laurentiu Ionut , Fetecau Catalin , Rosculet Razvan
Published: February 2017

In this paper, polypropylene (PP) filled with different levels of multiwalled carbon nanotubes (MWCNTs) manufactured by injection molding was closed-loop recycled in order to investigate the effect of recycling and reprocessing on its rheological, electrical, and mechanical properties. It was found that the PP/MWCNT composites keep the flow performance after mechanical recycling. Moreover, the stress and strain at break increase after one reprocessing cycle (mechanical recycling and injection molding), whereas no statistically significant changes in electrical conductivity, Young's modulus, and tensile strength of the PP/MWCNT composites filled with 1, 3, and 5 wt.% were observed.
Laser Nanopatterning for Wettability Applications
Authors: Orazi Leonardo , Gnilitskyi Iaroslav , Serro Ana Paula
Published: February 2017

We report on periodic, homogeneous nanoripples fabricated on stainless steel (SS), copper (Cu), and aluminum (Al) substrates using an ytterbium pulsed femtosecond laser. These structures called laser induced periodic surface structures (LIPSS) are processed at a relatively high-speed and over large areas. This paper investigates the effect of LIPSS on a wettability behavior of SS, Cu, and Al surfaces. It is shown that nanoripples significantly influenced the wettability character of these metals turning them from hydrophilic to hydrophobic behavior.
Prediction of Turbulent Flow Around a Square Cylinder With Rounded Corners
Authors: Dai S. S. , Younis B. A. , Zhang H. Y.
Published: February 2017

Predictions are reported of the two-dimensional turbulent flow around a square cylinder with rounded corners at high Reynolds numbers. The effects of rounded corners have proved difficult to predict with conventional turbulence closures, and hence, the adoption in this study of a two-equation closure that has been specifically adapted to account for the interactions between the organized mean-flow motions due to vortex shedding and the random motions due to turbulence. The computations were performed using openfoam and were validated against the data from flows past cylinders with sharp corners. For the case of rounded corners, only the modified turbulence closure succeeded in capturing the consequences of the delayed flow separation manifested mainly in the reduction of the magnitude of the lift and drag forces relative to the sharp-edged case. These and other results presented here argue in favor of the use of the computationally more efficient unsteady Reynolds-averaged Navier-Stokes approach to this important class of flows provided that the effects of vortex shedding are properly accounted for in the turbulence closure.
Modeling Legged Microrobot Locomotion Based on Contact Dynamics and Vibration in Multiple Modes and Axes
Authors: Qu Jinhong , Teeple Clark B. , Oldham Kenn R.
Published: February 2017

A dynamic model is developed for small-scale robots with multiple high-frequency actuated compliant elastic legs and a rigid body. The motion of the small-scale robots results from dual-direction motion of piezoelectric actuators attached to the legs, with impact dynamics increasing robot locomotion complexity. A dynamic model is developed to describe the small-scale robot motion in the presence of variable properties of the underlying terrain. The dynamic model is derived from beam theory with appropriate boundary and loading conditions and considers each robot leg as a continuous structure moving in two directions. Robot body motion is modeled in up to five degrees-of-freedom (DOF) using a rigid body approximation for the central robot chassis. Individual modes of the resulting multimode robot are treated as second-order linear systems. The dynamic model is tested with two different centimeter-scale robot prototypes having an analogous actuation scheme to millimeter-scale microrobots. In accounting for the interaction between the robot and ground, a dynamic model using the first two modes of each leg shows good agreement with experimental results for the centimeter-scale prototypes, in terms of both magnitude and the trends in robot locomotion with respect to actuation conditions.
Validation of the PTM Transition Model on a 3D Flow Through a Turbine Cascade
Authors: Yershov Sergiy , Yakovlev Viktor
Published: February 2017

This study presents a numerical simulation of a 3D viscous subsonic flow in the VKI-Genoa turbine cascade taking into account the laminar-turbulent transition. The numerical simulation is performed using the Reynolds-averaged Navier-Stokes (RANS) equations and the low-Reynolds k-ω SST turbulence model. The Langtry’s algebraic Production Term Modification (PTM) model is applied for modeling the laminar-turbulent transition. The governing equations are integrated using the second-order accurate Godunov’s type implicit ENO scheme. Computations of both fully turbulent and transitional flows are carried out. Much attention is given to the comparison between the present numerical results and the existing experimental data. The comparison was based on the surface distributions of the isentropic velocity, the friction velocity, the flow acceleration parameter, the displacement thickness, the shape-factor, and the momentum thickness Reynolds number. Velocity profiles upstream and downstream of the transition onset were compared also. The numerical results obtained show an influence of the transition on the secondary flow pattern. In the case of the transitional flow, when compared with the fully turbulence flow case, the endwall boundary layer cross-flow starts upstream, and it is more intensive, but less massive due to a thinner boundary layer in the laminar flow region.
Selection of Vibro-Characteristics for Monitoring Flange Integrity in the Field Conditions
Authors: Palmov Vladimir , Malinin Len
Published: February 2017

Monitoring of flange integrity in the field traditionally has been based on evaluating bolt tension and deriving pressure on the gasket from these data. Multiple techniques of evaluating bolt tension based on measuring speed of propagation of a longitudinal wave (time of flight), or ratio of speeds of longitudinal and shear waves (“L+S method”), demonstrate 5–10% accuracy in the controlled laboratory conditions [1]. However, accuracy in the field, on the flanges exposed to harsh environment, is often worse than 20%, which makes it difficult to evaluate flange integrity and predict a leak. The need for knowing acousto-elastic parameters of steel (in case of L+S method) may also present a hurdle.

Tools based on measuring a shift of the resonance frequencies (RF) are commercially available, though RF are relatively robust to tension, and require a reliable data processing procedure to discern the proper peaks. Evaluation of tension based on natural modes is more sensitive, but relatively complex and costly. Use of transfer functions (TF) offers several advantages over both RF and natural modes, as TFs depend on both RF frequencies and natural modes, and a properly selected parameter of TF can offer greater sensitivity.
Effect of Elasticity on Viscoplastic Flow
Authors: Letelier Mario F. , Díaz Nicolás , Siginer Dennis , Báez Ercio
Published: February 2017

The effect of superimposing elasticity on a viscoplastic fluid (elasto-viscoplastic fluid) is investigated through a linear combination of the simplified Phan-Thien Tanner (SPTT) model of viscoelasticity and Bingham model of viscoplastic fluid. The equation of motion is solved for the case of parallel steady flow in tubes of non-circular cross-sections. The effect of elasticity on the evolution of plug and stagnant zones, and rate of flow in terms of the Weissenberg number, a material parameter in the SPTT model, and the Bingham number is investigated. We find that elasticity tends to enhance the rate of flow for given viscoplastic conditions.
Bio-Inspired Engineering: Self-Healing Materials
Authors: Bakhtiyarov Sayavur I. , Kutelia Elguja R.
Published: February 2017

The objective of this study was to develop a composite metallic material with self-healing capabilities. A developed heterogeneous metal/ceramic composite is able to self-heal at temperatures as high as 1,200 °C.
Experimental Investigation on the Effect of Oxygen Enhancement on Radiation Distribution in Inverse Diffusion Flames
Authors: Wang Baolu , Eri Qitai , Li Ting , Duan Ran
Published: February 2017

Intense investigations have been focused on radiative heat transfer in oxygen-enhanced inverse diffusion flames since it plays a significant role not only in fundamental combustion research, but also in terrestrial and spacecraft fire safety study. To investigate the characteristics of the radiative heat transfer, a calibrated mid-infrared camera was used to acquire images of radiation intensity including soot and carbon dioxide in the 2–5μm wavelength range. The mole fraction of oxygen in the oxidizer varied from 21% to 100% with co-flowing inverse flame burner used to stabilize the flames. The characteristics of axial and radial radiation intensity distribution in different oxygen enhanced conditions are compared and analyzed. The results indicated that oxygen enhancement broadens the radial range of inner blue reaction zone and stretches the axial height of the plume zone. Similar to radial peak radiation intensity value and the growth rate of radial radiation intensity in different axial heights from X = 1D to X = 3D (X: axial height above the burner along the flame centerline; D: diameter of oxidizer exit), the peak value of radiation intensity and the growth rate of radiation intensity along the flame centerline both have a positive linear relationship with the oxygen mole fraction in the oxidizer.
Thermometric Studies of Newly Developed Nanolubricants
Authors: Bakhtiyarov Sayavur I. , Kutelia Elguja R. , Siginer Dennis A.
Published: February 2017

One of the primary requirements of space lubricants is that they have extremely low vapor pressures to withstand the space vacuum environment. Nanolubricants are known to have extremely low vapor pressure and some have attractive lubricant properties such as low coefficient of friction and good lifetimes. However, many other physical properties need to be evaluated in bringing forth new space liquid lubricants such as wide liquid temperature range and adequate heat transmission capabilities. The heat capacity and heat flow measurements for two newly developed nanolubricants Kolkhida 1 and Kolkhida 2 were conducted using Modulated Differential Scanning Calorimetry (MDSC). The experimental results revealed that the tested ionic liquids have large heat storage capacity as compare to the conventional heat transfer fluids.
Generic Steel Vehicle Front Bumper and Crush Can Assemblies Subjected to a Rigid High Speed Offset Frontal Impact
Authors: Seyed Yaghoubi A. , Begeman P. , Newaz G. , Board D. , Chen Y. , Faruque O.
Published: February 2017

This study presents experimental investigations of generic steel Front Bumper and Crush Can (FBCC) assemblies subjected to a 40% offset frontal impact. As automotive industries aim to reduce overall vehicle weight by applying lighter-weight materials to its structures, component-level studies become important. Computer aided models are valuable tools to complement physical testing by assessing the performances of these structures. Due to the lack of studies on component-level tests with FBCCs, a novel component-level test procedure would be useful to aid in CAE correlation. A sled-on-sled testing method was used to perform all the tests reported here. Impact speed was optimized such that there was no bottoming-out force for this type of test. Three high-speed cameras (HSCs), an infrared (IR) thermal camera, and several accelerometers were utilized to study impact performance of the FBCC structures.

The results showed that time histories of displacement and velocity from video tracking and accelerometers were in good agreement. The force-time history and force-displacement curves from different FBCC specimens were consistent and in good agreement with respect to each other with a low coefficient of variation calculated. Post-impact deformation pattern analysis of the samples showed consistent crush patterns. Heat was generated and dissipated at the tip of the crush can and progressed as the can started to fold.
Study of Steady Natural Convection With Laminar Flow in the Enclosures of Different Shapes
Authors: Gupta Anuj , Thakur H. C. , Vats Bhavyanidhi
Published: February 2017

This paper deals with the results of a simulative study of free convective heat transfer in the enclosure having different shapes. Problem has been characterized with the constant temperature on lower and upper walls while side walls have been considered as adiabatic walls. This study has been conducted for finding the shape of enclosure having maximum heat transfer rate considering different values for the aspect ratio and the Grashof number. Steady state natural convection problem has been formulated for all enclosures having laminar flow of air (at Pr = 0.7). Values for the aspect ratio vary from 0.2 to 0.5 while for the Grashof number from 10e4 to 10e8. ANSYS 14.0 has been used for modelling and simulation and for concluding study in the terms of Nusselt Number.
Microscale Modeling to Study Shot Peening Effects on Aluminum Alloy
Authors: Bae H. , Ramulu M. , Hossain A.
Published: February 2017

Shot peening is a cold working process used to produce a compressive residual stress to modify mechanical properties of metals. It causes impacting a surface with shots with significant force to create plastic deformation. The compressive residual stresses developed by shot peening process helps to avoid the propagation of micro-cracks exist in surface. Shot peening process is often used in aircraft industries to relieve tensile stresses built up in the grinding process, and replace them with beneficial compressive residual stresses. Shot peening has been developed to increase the fatigue strength of metallic parts. Compressive residual stress and surface hardening induced by shot peening process are found beneficial to increase the fatigue life and the resistance to stress corrosion cracking within the metallic component. Even though shot peening has been used for more than 50 years, a review of published papers indicates a lack of studies in numerical modeling. In particular, the effect of complex shot peening process to predict the target material responds to the multiple impacts of shots is not fully revealed. Most studies have investigated the fundamental mechanism and characteristics of fatigue improvement by single shot peening, and have studied the compressive residual stress induced by single normal impact on the surface of the specimen. However, single impact model is appropriate and efficient for sensitivity studies, local plastic effect, and indentation estimation. It is well known that the residual stress by single shot model is not suitable for practical use. The residual stress field from multi impacts is the resultant sum of all the fields by repeated and progressive impacts. It is not feasible to extrapolate results from the single impact model to a practical shot peening process with multiple impacts. Therefore, this research attempts to conduct a microscale modeling to study the shot peening effects of aluminum alloy responds to single and multiple impacts. First, a single shot impact model, representing single shot peening process, has been developed for the estimation of indentations at different velocities. The numerical simulations has been performed with the finite element software code LS-DYNA. The validations of the numerical simulations has been made from experimentally measured surface roughness data. Once the finite element code of single shot peening model is validated, additional numerical models are developed to simulate multiple shot peening process, using multiple impact shots. The multiple impact model are developed for the estimation of the residual stress field.
Fault Sensitivity Analysis of Data Feedback Control Design Based on Multiobjective Optimization
Authors: Kim Young-Man
Published: February 2017

This paper analyzes the fault sensitivity of data feedback control which is synthesized with H∞/H_ optimization technique. With I/O data, a closed-loop output predictor is parameterized by stochastically uncertain Markov parameters which are estimated by least squares. The estimation error due to bias and noise are rejected over infinite horizon and guarantees mean square stability in the sense of worst case. The measured I/O data is setup as state which makes the stability analysis and data feedback control synthesis possible. In order to improve fault sensitivity, the H_ index method is applied. Then, the controller design problem based on multiobjective optimization approach is solved in a numerically efficient way such as Linear Matrix Inequality (LMI). The fault sensitivity is analyzed in the full frequency range and its effect on the pre-defined performance is described with a simulation example.
Steam Turbine Loss Evaluation and Condition Monitoring: A Loss Data Based Study
Authors: Zhou Bin
Published: February 2017

Steam turbine mechanical breakdowns dominate equipment losses in the Power-Gen and Forest Product industries. As steam turbines are likely custom-built, variations in design, operation and maintenance practices across different industries could result in different levels of significance of the loss drivers. The present study focuses on comparing the turbine loss drivers and effective condition monitoring for loss mitigation in both industries. Steam turbine loss events from the two industries during a recent 10-year period were first reviewed and classified into typical turbine loss scenarios. Contributions of each loss scenario to the total loss count and value were summarized and compared across the two industries. Subsequently, applicable turbine condition monitoring methods were identified for each loss scenario, and evaluated with expert domain knowledge and available loss data. These monitoring methods were finally prioritized according to their functional effectiveness in turbine loss reduction.
Target Cell Detection via Microfluidic Magnetic Beads Assay
Authors: Liu Fan , K. C. Pawan , Zhang Ge , Zhe Jiang
Published: February 2017

We present a novel cell detection device based on a magnetic bead cell assay and microfluidic Coulter counting technology. The device can detect specific target cells ratios, as well as cells size distribution and concentrations. The device consists of two identical micro Coulter counters separated by a fluid chamber where an external magnetic field is applied. Target cells conjugated with magnetic beads are retarded by the magnetic field; transit time of a target cell passing through the second counter is longer than that through the first counter. In comparison, a non-target cell transit through two counters with nearly the same time. We demonstrated the transit time delay increased approximately linearly with the increasing target cell concentration. The limit of detection (LOD) of the assay was estimated to be 5.6% in terms of target cell ratio.
Model-Reference Based Adaptive Control for Enhancing Lateral Stability of Car-Trailer Systems
Authors: Vempaty Smitha , Lee Eungkil , He Yuping
Published: February 2017

This paper presents a model reference adaptive control (MRAC) approach to enhance the lateral stability of car-trailer systems. To this end, a 3 degrees of freedom (DOF) linear yaw-plane car-trailer model was developed as a “reference model”. The yaw rate of leading and trailing units of the reference model were used as the target states to control and stabilize a virtual vehicle plant represented by a 5 DOF linear yaw-roll car-trailer model. A Lyapunov-based controller was designed to handle the lateral stability of the car-trailer dynamical system. The model parameters and operating conditions of the system were predefined while designing the controller. The effectiveness of the adaptive controller for improving the lateral stability of car-trailer systems was demonstrated under a simulated multiple cycle sine-wave steering input maneuver. It was observed that the lateral stability of car-trailer system was improved by controlling respective yaw rates of the car and the trailer, using model reference adaptive control approach in conjunction with Lyapunov stability criterion.
Virtual Testing Applied to Door Latch Performance Evaluation
Authors: Friedman Keith , Bui Khanh , Hutchinson John , Stephens Matthew
Published: February 2017

Vehicle door latch minimum force capability testing presently utilizes uniaxial quasi-static loading conditions created toward the middle of the last century. Current technology enables more sophisticated virtual testing of a broad range of systems. Door latch failures have been observed in vehicles under a variety of conditions. Typically these conditions involve multiple axis loading conditions. The loading conditions presented during rollovers on passenger vehicle side door latches are not currently evaluated. Background on these conditions is reviewed. Rollover crash test results, rollover crashes and physical FMVSS 206 latch testing are reviewed. In this paper, the creation and validation of a passenger vehicle door latch model is described. The multi-axis loading conditions observed in virtual rollover testing at the latch location are characterized. These loads are then applied to the virtual testing of a latch in both the secondary and primary latch positions. The results are then compared with crash test and real world rollover results for the same latch. The results indicate that while a door latch in the secondary latch position may meet minimum existing uniaxial horizontal plane loading requirements, the incorporation of multi-axis loading conditions may result in failure of the latch to accomplish its intended purpose at loads substantially below the FMVSS 206 uniaxial failure loads. The findings suggest the need for reexamining the relevance of existing door latch testing practices in light of the prevalence of rollover impacts and other impact conditions in today’s vehicle fleet environment.
Feasibility Study of Erecting a Wind Farm in Kuwait
Authors: Gharbia Yousef , Anany Mohammed
Published: February 2017

Kuwait is considering diversifying its energy resources and not solely depending on oil and gas. According to the Ministry of Electricity and Water (MEW), the annual increase in electricity demand is 6–8%, which is considered higher than neighboring countries (2–3%). Wind energy is one of the renewable energy resources considered by the Government to close the gap between the supply and the demand. In this work, we are exploring the feasibility of erecting a wind farm of installed capacity of 120 MW in a suitable location in Kuwait. Hourly wind data was collected from three promising locations. Abraq Al-Habari (AH), one of three areas studied, enjoys the highest average wind speed of 5.12 m/s resulting in wind power density (WPD) of 181 W/m2 at a mast height of 10 meters. Wind Atlas Analysis and Application Program (WAsP) was used to estimate the energy production from the wind farm. The program takes into account the complexity of the terrain, the site roughness, and the obstacles and shelters effects. The results showed that the wind farm should be able to produce a net annual energy production (AEP) of 322 GWh and will cost about 260 million US$. This cost includes the installation capital cost as well as the operation expenses over the lifespan of the wind farm. The cost of energy production is estimated at 0.04 US$/kWh. The payback period considering an annual price escalation rate of 1% and a discount rate of 2.25% over the lifespan of the farm is predicted to be around ten years.
Influence of Fractional Damping and Time Delay on Maxwell-Voigt Model for Vibration Isolation
Authors: Kaul Sudhir
Published: February 2017

Models of vibration isolators are very commonly used for the design and analysis of isolation systems. Accurate isolator modeling is critical for a successful prediction of the dynamic characteristics of isolated systems. Isolators exhibit a complex behavior that depends on multiple parameters such as frequency, displacement amplitude, temperature and loading conditions. Therefore, it is important to choose a model that is accurate while adequately representing the relationships with relevant parameters. Recent literature has indicated some inherent advantages of fractional derivatives that can be exploited in the modeling of elastomeric isolators. Furthermore, time delay of damping is also seen to provide a realistic representation of damping. This paper examines the Maxwell-Voigt model with fractional damping and a time delay. This model is compared with the conventional Maxwell-Voigt model (without time delay or fractional damping) and the Voigt model in order to comprehend the influence of fractional damping and time delay on dynamic characteristics. Multiple simulations are performed after identifying model parameters from the data collected for a passive elastomeric isolator. The analysis results are compared and it is observed that the Voigt model is highly sensitive to fractional damping as well as time delay.
Life Centered Design Using Morphological Chart
Authors: Jawaharlal Mariappan , Ellingwood Stephanie Nguyen , Thokchom Kiranbala
Published: February 2017

Traditional engineering design is a customer-centric approach that focuses on maximizing performance objectives and minimizing costs under resource constraints. This approach may be effective in meeting the needs of a particular customer but may be detrimental for a larger group of people. A more inclusive human-centered design attempts to deal with a broader base of customers extending beyond geographical boundaries. Inadequacy of even this approach is apparent, as only humans are the center of this design paradigm.

Life Centered Design (LCD) is different from traditional design methodology. It accounts for all forms of life by creating beneficial symbiotic relationships between humans and other living matters leading to sustainability. Nature has solved most problems we face in some form, and it continues to inspire humans. In this context, the LCD approach makes perfect sense as a concept. The challenge, however, is to find solutions using the LCD approach. How do engineers, who avoided biology in the first place, identify potential solutions from nature for solving problems in hand?

This paper proposes the use of morphological charts in the early design phase to generate potential solutions. Specifically, the objective is to develop a structured system that will enable industry innovators to correlate everyday engineering functions with those available in nature. By developing a morphological chart with this correlation, engineers and designers can now identify and create life-friendly designs.
Performance Evaluation of Novel Spline-Curved Blades of a Vertical Axis Wind Turbine Based on the Savonius Concept
Authors: Mari Michele , Venturini Mauro , Beyene Asfaw
Published: February 2017

In this study, we present the results of a two-dimensional fluid-dynamic simulation of novel rotor geometry with spline function which is derivative of the traditional S-shape Savonius blade. A Computational Fluid Dynamic (CFD) analysis is conducted using the Spalart-Allmaras turbulent model, validated using experimental data released by Sandia National Laboratory. Results are presented in terms of dimensionless torque and power coefficients, assuming a wind speed of 7 m/s and height and rotor diameter of 1 m. Furthermore, analysis of the forces acting on the rotor is conducted by evaluating frontal and side forces on each blade, and the resultant force acting on the central shaft. A qualitative representation of the vorticity around the traditional and spline rotor is shown to prove that the novel blade is more “flow-friendly”, thus the air flow is less turbulent through the rotor. Finally, energy conversion capability of the Savonius turbines is estimated in parametric form for both the traditional and spline-curved geometry.
A Translation Technique: Dimensionless Ratings and Conversion Factors Between ISO and AGMA Gear Standards
Authors: Geren Necdet , Uzay Çagri
Published: February 2017

ISO and AGMA Standards are the most commonly used accurate approaches while designing a gear. But the most important gear design outputs that are module (m) and face width (b) are obtained from both of the approaches always differ from each other even under the same input parameters. Therefore, gear designers require detailed knowledge on the relative comparison of design outputs including cost. And a translation technique using conversion factors in between the standards are demanded as a stated need in the literature. Hence, this paper firstly obtains dimensionless gear rating numbers (GRi) to rate the design results of spur gears determined from both ISO 6336 and ANSI/AGMA 2101-D04 Standards, and then derives correlation equations to generate dimensionless conversion factors (CFs) to convert the design results obtained from ISO to AGMA. The CFs allow designers to move from one standard to another very easily. This enables engineering students and designers to meet the ever changing needs of global market.
Is Race Walking Lower Impact Than Running?
Authors: Norberg Jaclyn , Schmitz Anne
Published: February 2017

Race walking has grown over the past decade because it provides exercise without the high impact loads of running. However, whether race walking is truly a lower impact sport remains to be tested. Fifteen competitive race walkers ran and race walked over a force plate. The loading rate of the vertical ground reaction force was 46% lower for race walking in comparison to running. This suggests race walking is a lower impact exercise safer for the joints. This may be advantageous for people who would like to exercise at a higher intensity that walking provides but have joint problems, e.g. those with osteoarthritis.
Analysis of Base-Cooled Total Temperature Probes With Radiation
Authors: Schetz Joseph A. , Vincent Tyler , Lowe K. Todd
Published: February 2017

The design of total temperature probes for accurate measurements in hot, high-speed flows remains a topic of great interest in a number of engineering areas, despite a broad and deep prior literature on the subject. Prediction of error sources from convection, conduction and radiation is still an area of concern. For hot-flow conditions, the probe is normally mounted in a cooled support, leading to substantial axial conduction. Also, radiation plays a very important role in most hot, high-speed conditions. One can apply detailed computational methods for simultaneous convection, conduction and radiation heat transfer, but such approaches are not suitable for rapid, routine design studies. So, there is still a place for approximate analytic methods, and that is the subject of this paper.
An Ants-Search Based Method for Optimum Synthesis of Compliant Mechanisms
Authors: Diab Nadim , Smaili Ahmad
Published: February 2017

Compliant mechanisms are widely used in the industry and have gained more popularity in the past few decades with the advancements in smart materials and micro-electro mechanical systems (MEMS). Compliant mechanisms offer huge advantages over the classical rigid linkages due to their flexible behavior. Such flexible mechanisms reduce production time and cost especially that they eliminate the need of joints that can get pretty hectic especially at micro level manufacturing and assembly. By avoiding multi-joints in the design and their consequent clearances, a compliant mechanism can offer higher precision over its rigid counterpart. However, these advantages come with a price; compliant mechanisms are more challenging in terms of design and analysis. Many compliant mechanisms are designed to undergo relatively large deflections which in turn impose geometric nonlinearities. In the past, many compliant designs were based on intuition, experience, and trial and error. Later on, many theories developed to assist in designing and analyzing compliant mechanisms before proceeding with the manufacturing phase. This paper covers topology optimization of compliant structures using beam elements. The swarm intelligence technique known as Ant Search (AS) is used to find the optimum design that satisfies the required mechanism performance. A case study that involves the topology design of a miniature compliant displacement amplifier is presented and results are compared with the finite element solver ANSYS. The optimized topology mechanism produced a much larger amplification ratio as compared to that presented in literature. Results produced show the high potential of swarm intelligence and AS in particular at solving multi-disciplinary optimization problems that should not be limited to designs that involve physical paths.
A Numerical Investigation of the Effect of Inlet Velocity Oscillation on Heat Transfer in a Two-Dimensional Laminar Jet Impinging on an Isothermal Surface
Authors: Issa Johnny , Saliba Najib , Sidnawi Bchara
Published: February 2017

Heat transfer in a laminar confined oscillating slot jet impinging on an isothermal surface is numerically investigated. A uniform inlet velocity profile, oscillating with an angle φ, is used at the jet exit. The angle φ changes in a sinusoidal form. The height-to-jet width ratio is fixed at 5. The working fluid is air with constant physical properties corresponding to Prandtl number, Pr, equal to 0.74 at ambient conditions. Reynolds number, Re, is defined based on the jet hydraulic diameter and is varied in the self-stable range between 100 and 400. Strouhal number, St, is also varied between 0.05 and 0.75. Oscillating the jet at Reynolds number equal to 100 showed no heat transfer improvement over the steady state case, regardless of the used Strouhal number values. The vortices generated by the oscillation were too weak and could barely reach the wall. The flow showed a high vulnerability to severe oscillations which drastically reduced the jet heat removal ability. The vorticity contours showed a perfect symmetry which resulted in instantaneous and average Nusselt number distributions that are symmetric about the center of the isothermal surface at x = 0. The average stagnation Nusselt number, Nu0, decreased by about 1.25% as Strouhal number is increased from 0.4 to 0.625 then dipped by 44.1% as St is further increased to 0.75, a fact that was attributed to reduction in the bulk momentum by the relatively high frequency. With Reynolds number at 250, the lowest two frequencies corresponding to St of 0.05 and 0.1, resulted in a flow field that is more developed to the right side of the channel, a phenomenon that was linked to the direction of the first jet swing. The corresponding average Nusselt number distributions were consequently asymmetric, with a significant shift to the right. This asymmetric behavior gradually disappeared as the frequency is increased. At St of 0.4 and 0.5, the average stagnation Nusselt number Nu0, showed a 2.2% increase over the steady jet case. As Strouhal number is further increased beyond 0.5, the average Nu0 gradually decreased, since the oscillation period became too short for a vortex to be strong enough to reach the wall. For Reynolds number set at 400, the oscillating condition at the inlet engaged the jet into flapping. The jet showed a tendency to a permanent lean towards one side of the channel, for all used frequencies. Flapping was more one-sided which led to a shift in the average Nusselt number distribution at low frequencies. As Strouhal number is increased to 0.75, flapping became more stable and the generated vortices were expectedly weaker due to the higher frequency. Also, at this Strouhal number value, the average Nu distribution showed the best symmetry with a 2.45% improvement of the average stagnation Nusselt number, over that of the steady state case.
Extending Die-Attachment Fatigue Life of Power Electronics Using Phase Change Materials
Authors: Elston Levi J.
Published: February 2017

The ever-increasing power throughput and ever-decreasing size of modern electronics, specifically power electronics, requires more advanced packaging techniques and materials to maintain thermal limits and sustain mechanical life. Specific applications with known operating conditions for these components can realize added benefits through a tailored thermal-mechanical-electrical optimized assembly, potentially utilizing niche material classes. Without losing any expected functionality, solid-liquid phase change materials could be incorporated into the device structure to reduce peak temperature and/or suppress high-cycle fatigue problems commonly found at die-attachment interfaces. The purpose of this study was to investigate, through model-based design and analysis, the impact of using organic phase-change materials (PCMs) at two strategic locations in the standard device stack. The results suggest noteworthy life improvement (40%) is possible when optimizing for a given melt point material. Additionally, further improvements were predicted through future material enhancements, namely thermal conductivity and latent heat.
Analysis of Deep Sea Umbilical in Steep Wave Configuration
Authors: Nair Akash A. , A. Anbu Gnanaraj , Rajamanickam Panneer Selvam , Kuttikrishnan Gopakumar , Gidugu Ananda Ramadass
Published: February 2017

Deep sea mining is mineral retrieval process that takes place on the ocean floor wherein global industries are actively exploring and experimenting of different techniques in this relatively new concept of mining for extracting it economically from depths of 5000–5500 m below the ocean’s surface. National Institute of Ocean Technology (NIOT), India has been working on a mining concept for ∼6000 m water depth where a crawler based mining machine collects, crushes and pumps nodules to the mother ship using a positive displacement pump through a flexible riser (umbilical) system. The umbilical also serve as the weight supporting member for the miner and pump. In this paper, static and dynamic analysis of the umbilical system in steep wave configuration and the miner is carried out using ORCAFLEX for launching and touchdown conditions. Three different materials are considered and the best suitable material for umbilical is selected as the first step based on the tension. Then umbilical with Single Miner System is analyzed for the launching and touchdown conditions. Based on the analysis the optimum number and spacing of buoyancy tanks that will keep the stresses within the allowable limits in the umbilical cable are recommended.
Ricochet of High Speed Aluminium Projectiles From a Steel Plate
Authors: Farouk Bakhtier , Segletes Steven B.
Published: February 2017

A ricochet is a rebound, bounce or skip off a surface, particularly in the case of a projectile (a bullet). Many ricochets are accidental and while the force of the deflection decelerates the projectile, it can still be energetic and almost as lethal as before the deflection. The likelihood of ricochet is dependent on many factors, including projectile shape, projectile material, spin, velocity (and distance), target material and the angle of incidence. A numerical study on aluminum projectiles ricocheting off a steel plate is presented in this paper. The numerical package LS-DYNA is used to model the process of the impact of aluminum projectile on a steel plate. The simulations are carried out for a given range of projectile velocity (250 m/s to 1500 m/s) with varying impact angles. From the numerical results the ricochet angle and the ricochet velocity is predicted in terms of the incident angle and the incident velocity. The impact velocity effect on the ricochet phenomenon is studied. The numerical results are compared with available analytical solutions of the ricochet problem available in the literature.
Modeling of an Experimental Hydraulic System With Two Flow Control Parameters
Authors: Ben-Galim Y. , Bar-Or L. , Cahana Y. , Kadmon Y. , Barda K. , Horesh N. , Miron G. , Weiss Y.
Published: February 2017

This study suggests an innovative method for analyzing the behavior of hydraulic experimental systems that can be used as a tool for a system design. Design of experimental hydraulic systems can be a complicated challenge. Unlike industrial facilities, where the process is designated to work in a single or a limited narrow range of duty points and therefore classical design methods can be used, in experimental systems, where any selected duty point within a vast range may be needed, the system design may require much more advanced methods. Such an example is presented in this work where modeling of flow characteristics for an experimental hydraulic system is required. In this example, the system should provide any desired water flow rate in the wide range of 10–450 m3/h (an exceptional ratio in industrial facilities) with accuracy of ±2% while maintaining good stability. Review of former studies in this field didn’t reveal any suggested methods for such a design. In addition, standard process and piping software were examined and found unsuitable for this challenge. Therefore, an independent hydraulic model was developed. The modeling method is based on conventional analytical correlations of hydraulic resistance for a fully developed turbulent flow, modeling of centrifugal pump’s Pressure-Flow Curve (PFC) which depends on the frequency of the supplied voltage and by modeling the varying hydraulic resistance of a throttle control valve. This technique enables analytic evaluation of the possible flow rates in the system, to inspect the system stability and to perform a parametric study of the piping characteristics (diameter, valve type etc.) for two design alternatives. The code of the model was written in a free open-source Scilab platform. The results of the analytical model were illustrated on three dimensional plots displaying the system’s flow-rate versus the pumps frequency and the degree of rotation of the throttle control valve. According to these results, the most prominent alternative was chosen for manufacture.