bluuebunny/crossref_metadata_2025 huggingface dataset:
Propagation of a Plane Strain Hydraulic Fracture With a Fluid Lag in Permeable Rock
Authors: Chen B. , Barron Andrew R. , Owen D. R. J. , Li Chen-Feng
Published: July 2018

Based on the KGD scheme, this paper investigates, with both analytical and numerical approaches, the propagation of a hydraulic fracture with a fluid lag in permeable rock. On the analytical aspect, the general form of normalized governing equations is first formulated to take into account both fluid lag and leak-off during the process of hydraulic fracturing. Then a new self-similar solution corresponding to the limiting case of zero dimensionless confining stress (T=0) and infinite dimensionless leak-off coefficient (L=∞) is obtained. A dimensionless parameter R is proposed to indicate the propagation regimes of hydraulic fracture in more general cases, where R is defined as the ratio of the two time-scales related to the dimensionless confining stress T and the dimensionless leak-off coefficient L. In addition, a robust finite element-based KGD model has been developed to simulate the transient process from L=0 to L=∞ under T=0, and the numerical solutions converge and agree well with the self-similar solution at T=0 and L=∞. More general processes from T=0 and L=0 to T=∞ and L=∞ for three different values of R are also simulated, which proves the effectiveness of the proposed dimensionless parameter R for indicating fracture regimes.
Security in Cyber-Enabled Design and Manufacturing: A Survey
Authors: Chaduvula Siva Chaitanya , Dachowicz Adam , Atallah Mikhail J. , Panchal Jitesh H.
Published: July 2018

Developments in digital technology and manufacturing processes have expanded the horizon of designer innovation in creating products. In addition to this, real-time collaborative platforms help designers shorten the product development cycle by enabling collaborations with domain experts from concept generation to product realization and after-market. These collaborations are extending beyond enterprise and national boundaries, contributing to a growing concern among designers regarding the security of their sensitive information such as intellectual property (IP) and trade secrets. The source of such sensitive information leaks could be external (e.g., hacker) or internal (e.g., disgruntled employee) to the collaboration. From a designer's perspective, this fear can inhibit participation in a collaboration even though it might result in better products or services. In this paper, we aim to contextualize this evolving security space by discussing various security practices in digital domains, such as encryption and secret sharing, as well as manufacturing domains, such as physically unclonable function (PUF) and physical part watermarking for anticounterfeiting and tamper evidence purposes. Further, we classify these practices with respect to their performance against different adversarial models for different stages in product development. Such a classification can help designers to make informed decisions regarding security practices during the product realization process.
The Enthalpy-Transforming-Based Lattice Boltzmann Model for Solid–Liquid Phase Change
Authors: Huo Yutao , Rao Zhonghao
Published: July 2018

A new lattice Boltzmann (LB) model to solve the phase change problem, which is based on the enthalpy-transforming model has been developed in this paper. The problems of two-region phase change, natural convection of air, and phase change by convection are solved to verify the present LB model. In two-region phase change, the results of the present LB model agree well with that of analytical solution. The benchmark solutions are applied to evaluate the present LB model in natural convection of air and phase change material (PCM) as well. The results show that the present LB model is able to simulate the temperature distribution and capture the location of solid–liquid interface in the cavity accurately. Moreover, the present LB model is effective in computing owing to the fact that no iterations are necessary during the simulations.
Parameter–Excited Instabilities of a 2UPU-RUR-RPS Spherical Parallel Manipulator With a Driven Universal Joint
Authors: Wu Guanglei
Published: July 2018

This paper presents the parametrically excited lateral instabilities of an asymmetrical spherical parallel manipulator (SPM) by means of monodromy matrix method. The linearized equation of motion for the lateral vibrations is developed to analyze the stability problem, resorting to the Floquet theory, which is numerically illustrated. To this end, the parametrically excited unstable regions of the manipulator are visualized to reveal the effect of the system parameters on the stability. Critical parameters, such as rotating speeds of the driving shaft, are identified from the constructed parametric stability chart for the manipulator.
The Deformable Quad-Rotor: Mechanism Design, Kinematics, and Dynamics Effects Investigation
Authors: Zhao Na , Luo Yudong , Deng Hongbin , Shen Yantao
Published: July 2018

This paper focuses on designing, kinematically and dynamically characterizing a novel deformable quad-rotor that is based on the scissor-like foldable mechanisms. Inspired by morphological adaptation of birds during flight, the quad-rotor allows that its volume can be varied to dynamically adapt complex environments and spaces. The advantages of such mechanism are twofold following the scenario, that is, the quad-rotor can stably fly with a big volume/size and can also switch to a smaller volume for a swift flight in response to the changes of the environments and spaces. It therefore is capable of efficiently avoiding obstacles, stably passing through narrow spaces, and resisting certain-extent wind effects. To generate the controllable deformation, the actuated angulated scissor elements in the structure play an important role. In this paper, the scissor element design, its actuation mechanism, and volume deformation of the new quad-rotor are presented in detail. Simulations and experiments are then conducted to validate the controlled deformation as well as to investigate the deformation elicited effects to the activated quad-rotor airframe and its aerodynamics. The results demonstrate the effectiveness of the proposed deformable quad-rotor, and prove that it enables excellent volume deformation performance, good flight adaptation, as well as minimal aerodynamics influences during deforming.
Transient Analysis of the Interactions Between a Heat Transferring, Radial Stagnation Flow, and a Rotating Cylinder-Magnetohydrodynamic and Nonuniform Transpiration Effects
Authors: Alizadeh Rasool , Rahimi Asghar B. , Karimi Nader , Alizadeh Ahmad
Published: July 2018

This paper aims at providing further understanding on the fluid flow and heat transfer processes in unsteady rotating systems with mass transpiration. Such systems can be found in chemical separators, hydraulic systems, and printing devices. To this end, an unsteady viscous flow in the vicinity of an unaxisymmetric stagnation-point on a rotating cylinder is examined. The nonuniform transpiration and a transverse magnetic field are further considered. The angular speed of the cylinder and the thermal boundary conditions are expressed by time-dependent functions. A reduction of the Navier–Stokes and energy equations is obtained through using appropriate similarity transformations. The semisimilar solution of the Navier–Stokes equations and energy equation are developed numerically using an implicit finite difference scheme. Pertinent parameters including the Reynolds number and magnetic parameter and transpiration function are subsequently varied systematically. It is shown that the transpiration function can significantly affect the thermal and hydrodynamic behaviors of the system. In keeping with the findings in other areas of magnetohydrodynamics (MHD), the results show that the applied magnetic field has modest effects on the Nusselt number. However, it is demonstrated that the magnetic effects can significantly increase the imposed shear stress on the surface of the rotating cylinder.
Risk Analysis of Spent Fuel Pool Caused by Seismic Events
Authors: Wang Ming , Lin Modi , Wang Jinkai
Published: July 2018

Spent fuel pool (SFP) stores fuel assemblies removed from the reactor over the years. SFP and its accident mitigation measures may fail simultaneously at the time of the earthquake, which may cause serious accident consequences. This paper uses probabilistic safety assessment (PSA) method to quantitatively evaluate the risk of SFP for a CPR1000 unit caused by seismic events. Quantitative analysis results show that seismic events' risk is the highest in all internal events and external events for SFP. In order to reduce the risk of SFP, more attention should be paid to improve seismic capacity or reduce the common failure for systems and components associated with SFP under the earthquake situation.
Power Management and Distribution System for a Mars Surface Fission Power Reactor
Authors: Hew Yayu M. , Schillo Kevin J. , Kumar Akansha , Harris Kurt E. , Howe Steven D.
Published: July 2018

This paper presents a power management and distribution system (PMAD) for a growing Martian colony. The colony is designed for a 15-year operation lifetime, and will accommodate a population that grows from 6 to 126 crewmembers. To provide sufficient power, a nuclear fission surface power (FSP) system is proposed with a total capacity of 1 MWel. The system consists of three 333 kWel fission reactors. Direct current (DC) transmission with 2000 voltage direct current (VDC) is found to provide the best power density and transmission efficiency for the given configuration. The grounding system consists of grounding rods, grounding grids, and a soil-enhancement plan. A regenerative fuel cell using a propellant tank recycled from the lander was found to have the best energy density and scalability among all the options investigated. The thermal energy reservoir, while having the worst storage efficiency, can be constructed through in situ resource utilization (ISRU), and is a promising long-term option. A daily load following a 12-h cycle can be achieved, and the power variation will be less than 10% during normal operation. Several main load-following scenarios are studied and accommodated, including an extended dust storm, nighttime, daytime, and transient peak power operation. A contingency power operation budget is also considered in the event that all of the reactors fail. The system has a power distribution efficiency of 85%, a storage efficiency of 50%, and a total mass of 13 Mt.
Transport Mechanism of Steam Methane Reforming on Fixed Bed Catalyst Heated by High Temperature Helium for Hydrogen Production: A Computational Fluid Dynamics Investigation
Authors: Wang Feng , Yang Ziqiang , Wang Long , Wen Qiang
Published: July 2018

In this study, we numerically evaluated the performance of a steam methane reforming (SMR) reactor heated using high-temperature helium for hydrogen production. The result showed that with an increase in the reactant gas inlet velocity, the temperature at the same reactor length position decreased. The maximum gas temperature difference at the gas collection chamber reached approximately 55 °C. The outlet temperature difference increased to 35 °C when the inlet temperature increased from 370 °C to 570 °C. A higher inlet temperature did not have a positive effect on the system's thermal efficiency. The methane conversion rate increased by 68%, and the hydrogen production rate increased by 55%, when the helium inlet velocity increased from 2 m/s to 22 m/s. When the helium inlet temperature increased by 200 °C, the highest temperature of the reactant gas increased by 132 °C. In the SMR for hydrogen production using a high-temperature gas-cooled reactor (HTGR), low reactant-gas inlet velocity, suitable inlet temperature, high inlet velocity, and a high HTGR outlet temperature of helium were preferable.
Creating Value in the Coal Delivery Chain to a Captive Power Plant
Authors: Osborne Dave , Eyre Dan
Published: July 2018

Integration of a supply chain involves the design, planning, execution, control, and monitoring of delivery chain activities for creating net value. This includes building appropriate infrastructure, leveraging logistics, synchronizing supply with demand, and continually measuring/monitoring performance. The combination of advanced mining and beneficiation technologies and power plant improvement processes when integrated within a “whole-of-supply chain” promises great potential for creating step changes in the way that coal is delivered to its end user. When the supply chain involves a direct mine-to-power plant, the benefits may initially seem limited, but the adoption of a value-in-use model to determine costs incurred along the chain can show how changes in mining, beneficiation, and supply impact on power plant performance and, ultimately, total-supply chain costs. Uniper Technologies' proprietary Fuel Evaluation Tool as described in the paper is an expert value-in-use model, which combined with coal beneficiation modeling and expertise from Somerset International can show the potential improvements achievable by adopting a “whole-of-supply-chain” approach.
The Influence of Surface Patterning on the Thermal Properties of Textured Thrust Bearings
Authors: Fu Gen , Untaroiu Alexandrina
Published: July 2018

Contact performance can be enhanced by using textured surfaces. These are also found to have influences on lubricated contacts. A procedure to find the optimal partially textured thrust bearing configuration is presented in this study. A parallel sector-pad thrust bearing is simulated by a three-dimensional (3D) computational fluid dynamics (CFD) model. The stationary surface of the bearing is textured with dimples, while the rotor surface is flat. The results of the baseline model are validated by experimental data. In this study, we compare rectangular and elliptical dimples by investigating design parameters, such as major the length of the major axis (width), the length of the minor axis (length), dimple depth, circumferential space between two dimples, radial space between two dimples, radial extent, circumferential extent are selected as design parameters. A parametric study is conducted to investigate the influence of the texture geometries and a surrogate model is created. Based on the surrogate model, a multi-objective optimization scheme is used to navigate the design space and find the optimal texture structure that provides a lower maximal temperature inside the fluid film, higher load capacity, and lower friction torque. The results show that the optimal radial extent of the texture is around 80% of the pad radial length for both cases. The optimal length of the elliptical dimples in the circumferential direction is about 30% larger than the value of the rectangular dimples. In the final optimal design, the maximal temperature reduces 1.1% and 1.3% for rectangular and elliptical dimples while the load capacities are maintained at the same level.
Model for Elastic–Plastic Contact Between Rough Surfaces
Authors: Wang Zhiqian , Liu Xingna
Published: July 2018

This paper studies elastic–plastic contact between Greenwood–Williamson (GW) rough surfaces, on which there are many asperities with the same radius whose height obeys the Gaussian distribution. A new plasticity index is defined as the ratio of the standard deviation of the height of asperities on the rough surface to the single-asperity critical displacement (the transition point from the elastic to the elastic-fully plastic deformation regime), which is linearly proportional to the GW plasticity index to the power of 2. The equations for the load/area–separation relationship of rough surfaces are presented based on Wang and Wang's smooth model of singe-asperity elastic–plastic contact, which is an improvement of the Kogut–Etsion (KE) empirical model based on finite element analysis (FEA) data. The load/area–separation relationship can be described by empirical Gaussian functions. The load–area relationship of rough surfaces is approximately linear. The average pressure is only function of the new plasticity index. According to Wang and Wang's conclusion that Etsion et al. single-asperity elastic–plastic loading (EPL) index is approximately equal to the ratio of the single-asperity residual plastic contact displacement to the single-asperity total elastic–plastic contact displacement, the equations for the relationship between Kadin et al. modified plasticity index (MPI) and separation of rough surfaces are also presented. In addition, the MPI is approximately linearly proportional to the separation between rough surfaces for a given new plasticity index ranging from 5 to 30. When the new plasticity index is smaller than 5, due to the large proportion of the elastic deformation in the total deformation, the MPI slightly deviate from linearity.
Experimental and Numerical Visualization of Heat Transfer and Hydrodynamics Induced by Double Droplet Train Impingement
Authors: Zhang Taolue , Muthusamy Jayaveera , Alvarado Dr. Jorge L. , Kanjirakat Anoop , Sadr Reza
Published: July 2018

The objective of this study was to visualize and simulate the thermal physical process during double droplet train impingement for three different horizontal impact spacings (S = 0.65 mm, 1.2 mm and 2 mm). Two identical HFE-7100 droplet trains were produced using a piezoelectric droplet generator at a frequency of 6000 Hz with a corresponding droplet Weber number of 312. A translucent sapphire substrate with a thin film ITO coating was used as heater in the experiments. The heat transfer and hydrodynamics of double droplet train impingement have been visualized using IR thermal imaging and high speed optical imaging techniques, respectively. The double droplet train impingement process was also simulated numerically using the Coupled Level Set-Volume of Fluid (CLS-VOF) approach with dynamic mesh adaption (DMA). Humps were observed both numerically and experimentally between two adjacent impact craters due to the interactions caused by the impinging droplet trains. It was found that the hump height decreased when impact spacing increased. IR images show that higher impact spacing leads to better heat transfer performance, which could be due to the lower hump height at greater impact spacing conditions. It was also observed that higher impact spacing leads to better thermo-hydrodynamics within and outside the impingement zone. In summary, results show that horizontal impact spacing plays a significant role in double droplet train impingement cooling.

This work was supported by the National Priority Research Program of the Qatar National Research Fund, Grant No.: NPRP 6-1304-2-525.
Visualization of Dropwise Condensation on a Superhydrophobic Microporous Surface
Authors: Kim Jin Sub , Shin Dong Hwan , Moon Wooyong , Heo Jaehun , Lee Jungho
Published: July 2018

Condensation behavior on a superhydrophobic microporous surface was visually compared with that on a plain surface in the water saturated at the pressures of 101.3 kPa (Tsat = 100 °C) and 3.2 kPa (Tsat = 25 °C). The microporous surface was formed by sintering copper powders with the average diameter of 50 µm on the bare copper surface, resulting in the coating thickness of approximately 250 µm. The microporous surface was coated with the polytetrafluoroethylene (PTFE) layer by the spray-coating method to change the wettability into superhydrophobic, which was verified from a measured apparent contact angle of above 150°. While dropwise condensation is observed on both bare and hydrophobic plain surfaces at Psat = 101.3 kPa, filmwise condensation is seen on the superhydrophilic plain surface. At the low saturation pressure of 3.2 kPa, condensation behavior on the bare plain surface is changed into the filmwise condensation with improved wettability. In contrast, on the microporous surface, the only superhydrophobic microporous surface shows dropwise condensation behavior, where the surface is considered at the Cassie-state. However, filmwise condensation behaviors are observed on both superhydrophilic and bare microporous surfaces due to the wicking into the pores.
A Survey on Fractional Derivative Modeling of Power-Law Frequency-Dependent Viscous Dissipative and Scattering Attenuation in Acoustic Wave Propagation
Authors: Cai Wei , Chen Wen , Fang Jun , Holm Sverre
Published: July 2018

This paper aims at presenting a survey of the fractional derivative acoustic wave equations, which have been developed in recent decades to describe the observed frequency-dependent attenuation and scattering of acoustic wave propagating through complex media. The derivation of these models and their underlying elastoviscous constitutive relationships are reviewed, and the successful applications and numerical simulations are also highlighted. The different fractional derivative acoustic wave equations characterizing viscous dissipation are analyzed and compared with each other, along with the connections and differences between these models. These model equations are mainly classified into two categories: temporal and spatial fractional derivative models. The statistical interpretation for the range of power-law indices is presented with the help of Lévy stable distribution. In addition, the fractional derivative biharmonic wave equations governing scattering attenuation are introduced and can be viewed as a generalization of viscous dissipative attenuation models.
Characterization of Limacon Gas Expanders With Consideration to the Dynamics of Apex Seals and Inlet Control Valve
Authors: Phung Truong H. , Sultan Ibrahim A.
Published: July 2018

Limaçon machine, of which the relative motion between the rotor and housing follows the limaçon curve, belongs to a class of rotary positive displacement machines. The profiles of rotors and housings of those machines can be constructed of either limaçon or circular curves, hence the names: limaçon-to-limaçon, circolimaçon, and limaçon-to-circular machines. This paper presents the investigation into the thermodynamic performance of the limaçon-to-circular machines with the presence of apex seals and inlet valve. This paper sets out by briefly introducing the limaçon technology and the construction of the limaçon-to-circular machine working volume. The mathematical descriptions of ports' positions and areas have also been introduced. The paper then discusses the flow and phase composition of working fluid through the working chambers as well as how the fluid velocity is modeled and calculated. Then the seal dynamic model and response of inlet valve are presented followed by the machine thermodynamic model. A case study has also been presented to show the responses of seals and inlet valve during the machine operation.
Design for Manufacturability-Based Feedback to Mitigate Design Fixation
Authors: Abdelall Esraa S. , Frank Matthew C. , Stone Richard T.
Published: July 2018

This study assessed the effectiveness of three-dimensional (3D) visual feedback from design for manufacturability (DFM) software on mitigating design fixation on nonproducible manufacturability features. A fixation group and a defixation group were asked to design a basic product for additive manufacturing (AM) and then to modify the next iteration for conventional machining. The fixation group relied on their self-assessment while modifying, while the defixation group utilized dfm software feedback. Results showed that 3D feedback reduced design fixation on nonproducible features and improved the machinability of modified designs. Findings suggest the use of dfm software for treating the design fixation related to AM and for facilitating migration of designs from additive to conventional manufacturing. This work could be applied to manufacturing industries, particularly where AM is used for prototyping, or when demand for part changes and an AM part needs to migrate to conventional methods.
Differential Gear Bending Stresses in the Presence of Misalignments and Run-out
Authors: Kolivand M. , Sun V. , Chemelli D. , Balenda J. , Shi Z.
Published: July 2018

Automotive differential gears are usually operating at very low speed and high load conditions and hence are usually designed to be protected against the root bending fatigue failure. Depending on application requirements and lubrication regime, surface failures may occasionally be encountered as well. Mainstream existing design procedures published by AGMA are based on analyzing one single gear pair engagement while up to four potential engagements, between two side gears and two differential pinions, exist. There are also differential designs with three or four differential pinions that increase potential number of engagements to, respectively, six and eight. Usually, the hypoid gear loading is divided by number of side gears, two, also differential pinion loads are usually assumed to be equal; this is a good estimate when no misalignments are present. When misalignments are present, load sharing between the differential pinions becomes greatly imbalanced. This study tries to come up with a simplified analytical approach to evaluate overload factor between the differential pinions as a result of misalignments realized by differential gears inside a differential case. The total indexing run-out quality of gears is also studied through treating it as a source of misalignment. This study will help designers to evaluate the effects of tolerance limits and differential case machining errors on differential gear bending lives.
Variation Analysis of Compliant Parts in Composite Material Joined by Adhesive: A Numerical Tool
Authors: Corrado Andrea , Polini Wilma
Published: July 2018

Tolerance analysis defines a procedure to estimate the resultant variation of the assembly geometry, given the tolerances associated with individual components and the functional relationship between the individual components and the assembly requirements. This aspect is particularly relevant when parts made of composite material are considered, since the research emphasis to date was on the design and fabrication of composite parts, with considerably less attention to quality issues in their subsequent assembly. This work presents a numerical tool to solve the tolerance analysis of assemblies made of compliant parts in composite material; it estimates the geometric deviations of an assembly due to the compliance of the material, the geometrical deviations of the components and the fastening of the parts by adhesive. The comparison between numerical and experimental results obtained for a case study shows a good agreement.
Additive Manufacturing of Structural Cores and Washout Tooling for Autoclave Curing of Hybrid Composite Structures
Authors: Türk Daniel-Alexander , Ebnöther Andreas , Zogg Markus , Meboldt Mirko
Published: July 2018

This paper presents a study combining additive manufactured (AM) elements with carbon fiber-reinforced polymers (CFRP) for the autoclave curing of complex-shaped, lightweight structures. Two approaches were developed: First, structural cores were produced with AM, over-laminated with CFRP, and co-cured in the autoclave. Second, a functional hull is produced with AM, filled with a temperature- and pressure-resistant material, and over-laminated with CFRP. After curing, the filler-material is removed to obtain a hollow lightweight structure. The approaches were applied to hat stiffeners, which were modeled, fabricated, and tested in three-point bending. Results show weight savings by up to 5% compared to a foam core reference. Moreover, the AM element contributes to the mechanical performance of the hat stiffener, which is highlighted by an increase in the specific bending stiffness and the first failure load by up to 18% and 310%. Results indicate that the approaches are appropriate for composite structures with complex geometries.
Analysis Method for Impact and Dispersion Behavior of Water-Filled Tank
Authors: Takazawa Hidekazu , Hirosaka Kazuma , Miyazaki Katsumasa , Tohyama Norihide , Matsumoto Naomi
Published: July 2018

A new Japanese nuclear regulation involves estimating the possible damage to plant structures due to intentional aircraft impact. The effect of aircraft impact needs to be considered in the existing nuclear power plants. The structural damage and fuel dispersion behavior after aircraft impact into plant structures can be evaluated using finite element analysis (FEA). FEA needs validated experimental data to determine the reliability of the results. In this study, an analysis method was validated using a simple model such as a cylindrical tank. Numerical simulations were conducted to evaluate the impact and dispersion behavior of a water-filled cylindrical tank. The simulated results were compared with the test results of the VTT Technical Research Centre of Finland (VTT). The simulations were carried out using a multipurpose FEA code LS-DYNA®. The cylindrical tank was modeled using a shell element, and the tank water was modeled using smoothed particle hydrodynamics (SPH) elements. First, two analysis models were used to evaluate the effect of the number of SPH elements. One had about 300,000 SPH elements and the other had 37,000 SPH elements. The cylindrical tank ruptured in the longitudinal direction after crashing into a rigid wall, and the filled water dispersed. There were few differences in the simulated results when using different numbers of SPH elements. The VTT impact test was simulated with an arbitrary Lagrangian-Eulerian (ALE) element to consider the air drag. The analytical dispersion pattern and history of dispersion velocity ratio agreed well with the impact test results.
A Reference Pelton Turbine—Three-Dimensional Flow Front Tracking Within a Rotating Pelton Bucket
Authors: Solemslie Bjørn W. , Dahlhaug Ole G.
Published: July 2018

A postprocessing method has been developed to enable the extraction of quantifiable data from images captured from within the rotating frame of reference of a Pelton turbine. The turbine tested was the reference Pelton runner, designed at the Waterpower Laboratory, Norwegian University of Science and Technology (NTNU). The method relies on interpolation to three-dimensional (3D) map the inner hydraulic surface of the bucket. Interpolation has been conducted with two different schemes, i.e., Barycentric triangular and biharmonic spline, where the latter showed significant increase in accuracy. The 3D mapping provides the world coordinates of the pixels within the bucket and enables the tracking of the water front as it propagates through the bucket. The method has been described and the uncertainties have been estimated in the order of 0.4 mm for most of the hydraulic surface. The results follow expected, and previously observed, behavior and show great promise with regard to validation of numerical simulations. Results obtained by the method will be of great interest for the computational fluid dynamics (CFD) community as it can be used as direct validation data for flow propagation found with numerical methods. The method relies heavily on manual input due to the high noise and low contrast of the available images, which causes an increase in both uncertainty and time consumption. Suggestion for reducing uncertainty and time consumption are presented and will be implemented in future publications.
Composite Laminate Delamination Simulation and Experiment: A Review of Recent Development
Authors: Tabiei Ala , Zhang Wenlong
Published: July 2018

Composite laminate has extensive usage in the aerospace and automotive industries. Thus delamination, one of its most prevalent and challenging failure modes, has attracted substantial research efforts, and lead to the rapid development of both simulation and experiment method. Although reviews exist about simulation and experiment methods, there are not many that cover the development in the last five years. This paper is targeted to fill that gap. We covered a broad range of topic in delamination, from the basic delamination onset and propagation theories to complex loading scenarios, like impact and fatigue loading. From a simulation point of view, virtual crack closure technique (VCCT) and cohesive zone model (CZM), the two most famous methods of delamination modeling, are compared and elaborated. Their implementation techniques are described, and their merits and drawbacks are discussed. We also covered the failure mode of combined delamination and matrix cracking, which is prevalent in impact loading scenarios. Simulation techniques, along with the failure mechanisms, are presented. From experiment point of view, the discussed topics range from delamination fracture toughness (DFT) tests under static, dynamic, or cyclic loading conditions, to impact tests that aim to obtain the impact resistance and residual strength after impact. Moreover, a collection of recent experiment data is provided.
A Free Interface Component Mode Synthesis Approach for Determining the Micro-End Mill Dynamics
Authors: Singh Kundan K. , Kulkarni Salil S. , Kartik V. , Singh Ramesh
Published: July 2018

The prediction accuracy of the stability boundary in the machining process depends upon accurate estimation of cutting tool-tip dynamics. Note that the experimental modal analysis using direct impact at miniature end mill (typically 50–500 μm in diameter) is not feasible as it can result in tool failure. Consequently, alternative techniques such as experimental modal analysis using reciprocity theory and frequency-based receptance coupling substructure analysis (RCSA) have been used extensively for determining tool-tip dynamics. The experimental approach based on reciprocity theory assumes that the structure is symmetric (cross frequency response functions (FRFs) are same between two points of interest in a structure). RCSA requires a very fine frequency resolution and matrix inversion, which can lead to computational complexities. In addition, RCSA takes into account the FRFs only at the interface and free end, which can induce errors. Owing to these issues with existing approaches, this paper proposes a free-interface component mode synthesis (CMS) approach for estimation of micro-end mill dynamics. The effect of machine tool compliance including the collet–tool interface has been included for estimation of micro-end mill dynamics via a free-interface CMS approach wherein the experimental and analytical mode shapes are coupled. The predicted micro-end mill dynamics have been compared with RCSA and experimental modal analysis using reciprocity theory. Finally, the stability lobe diagrams for high-speed micromilling of Ti6Al4V has been made using the tool-tip dynamics from CMS, RCSA, and experimental technique using reciprocity theory and validated against experimental measurements for onset of instability.
Hyperspectral Imaging With Burn Contour Extraction for Burn Wound Depth Assessment
Authors: Ding Houzhu , Chang Robert C.
Published: July 2018

Skin thermal burn wounds are classified according to subjective assessments of wound depth that indicate divergent modes of medical intervention. However, clinically discriminating superficial partial from deep partial thickness burns remains a significant challenge, where only the latter requires excision and skin grafting. Motivated by the need for and ramifications of an objective burn wound assessment tool, this paper advances hyperspectral imaging (HSI) in a porcine skin burn model to quantitatively evaluate thermal burn injuries (superficial and deep partial thickness burns). Two-dimensional (2D) principal component analysis for noise reduction is applied to images captured by HSI in the visible wavelength range. Herein, a multivariate regression analysis is used to calculate the total hemoglobin concentration (tHb) and the oxygen saturation (StO2) of the injured tissue. These perfusion profiles are spatially mapped to yield characteristic distributions corresponding to the burn wound degree validated histologically. The results demonstrate that StO2 and tHb diverge significantly for superficial partial and deep partial burns at 24 h and 1 h, respectively (p < 0.05). A StO2 burn map at 1 h post-burn yields a 2D burn contour that is registered with a burn color image. This early stage burn-specific contour has implications to guide downstream burn excision and grafting.
Yule Series Model Application for Blade Tip Timing Readouts Processing Resulting in Blade Oscillation Characteristics Estimation
Authors: Karmalita V.
Published: July 2018

This paper deals with an application of the Yule series model for contactless (blade tip timing, BTT) measurements. The approach creates a straightforward processing procedure from the experimental data to obtain estimates of blade logarithmic decrement and natural frequency. The existing analytical expressions for confidence intervals enable a priori evaluation for the accuracy of blade oscillation characteristics estimates. Proposed sensors allocation scheme ensures oscillation sampling rates providing efficient estimates of oscillation characteristics. Real-time measurements of blade logarithmic decrement and natural frequency give a chance of this method implementation for research and health monitoring purposes.
Optimum Tuning of Passive Tuned Mass Dampers for the Mitigation of Pulse-Like Responses
Authors: Salvi Jonathan , Rizzi Egidio , Rustighi Emiliano , Ferguson Neil S.
Published: July 2018

Tuned mass dampers (TMDs) are typically introduced and calibrated as natural passive control devices for the vibration mitigation of the steady-state response of primary structures subjected to persistent excitations. Otherwise, this work investigates the optimum tuning of TMDs toward minimizing the transient structural response. Specifically, a single-degree-of-freedom (SDOF) system is considered as a primary structure, with added TMD, subjected to pulse-like excitations. First, the system is analytically analyzed, within the time domain, for unit impulse base displacement, through Laplace transform. Then, the tuning process is numerically explored by an optimization procedure focused on an average response index, to extract the optimum condition toward best TMD calibration. The efficiency of the proposed control device is then assessed and demonstrated through further post-tuning numerical tests, by considering as dynamic loadings: first, a time unit impulse base displacement, coherent with the source description above; second, different pulse-like excitations, to detect the effectiveness of the so-conceived TMD for generic ideal shock actions; third, a set of nonstationary earthquake excitations, to enquire the achievable level of seismic isolation. It is shown that this leads to a consistent passive TMD in such a transient excitation context, apt to mitigate the average response. Additionally, the present tuning forms a necessary optimum background for a possible upgrade to a hybrid TMD, with the potential addition of an active controller to the so-optimized TMD, to achieve even further control performance, once turned on, specifically for abating the peak response, too.
Influence of Rain Ingestion on the Endwall Treatment in an Axial Flow Compressor
Authors: Li Jichao , Du Juan , Li Mingzhen , Lin Feng , Zhang Hongwu , Nie Chaoqun
Published: July 2018

The effects of water ingestion on the performance of an axial flow compressor are experimentally studied with and without endwall treatment. The background to the work is derived from the assessment of airworthiness for an aero-engine. The stability-enhancing effects with endwall treatments under rain ingestion are not previously known. Moreover, all the endwall treatments are designed under dry air conditions in the compressor. Water ingestion at 3% and 5% relative to the design mass flow proposed in the airworthiness standard are applied to initially investigate the effects on the performance under smooth casing (SC). Results show that the water ingestions are mainly located near the casing wall after they move through the rotor blade row. The pressure rise coefficient increases, efficiency declines, and torque increases under the proposed water ingestion. The increase of the inlet water increases the thickness of the water film downstream the rotor blade row and aggravates the adverse effects on the performances. Subsequently, three endwall treatments, namely circumferential grooves, axial slots, and hybrid slots–grooves, are tested with and without water ingestion. Compared with no water ingestion, the circumferential grooves basically have no resistance to the water ingestion. The axial slots best prevent the drop of the pressure rise coefficient induced by water ingestion, and hybrid slots–grooves are the second-best place owing to the contribution of the front axial slots. Therefore, the hybrid slots–grooves can not only extend the stall margin with less efficiency penalty compared with axial slots, but also prevent rain ingestion from worsening the compressor performance.
Extremum Seeking for Wind and Solar Energy Applications
Authors: Ghaffari Azad , Krstic Miroslav , Seshagiri Sridhar
Published: July 2018

This paper explores the advantages of extremum seeking (ES) for wind and solar energy applications. The experimental results are also provided for the photovoltaic system. ES is an attractive alternative to perturb and observe (P&O) techniques for solving maximum power point tracking (MPPT) problems in wind and solar systems. As a model-free, real-time optimization approach, ES is well suited for systems with unknown dynamics or those that are affected by high levels of uncertainty or external dynamics, like wind turbines (WT) and PV systems. ES has the dual benefit of rigorously provable convergence and the simplicity of hardware implementation. In addition to a probing signal, the ES algorithm employs only an integrator, as well as optional high-pass and a low-pass filters. Finally, multivariable MPPT based on ES for PV systems are presented, and the validity of the proposed algorithms with experimental results are verified. Experimental results verify the effectiveness of the Newton-based MPPT versus its scalar and multivariable gradient-based counterparts.
Seeing the Light
Authors: Brown Alan S.
Published: July 2018

This article discusses innovations and evolution in the optics industry. Local firms teamed with Monroe Community College to hold events that introduced high school students to optics . Paul Ballentine, who analyzes technology opportunities as deputy director of University of Rochester’s Center for Emerging and Innovative Sciences, sees plenty of upside. Light-based systems are continuing to grow, but Rochester’s optics community will have to reinvent itself to thrive. The Rochester Regional Photonics Cluster has morphed into New York Photonics, with additional clusters in Buffalo, central New York, Albany, and Long Island. It now represents hundreds of optics and photonics companies throughout the state. Paul Conrow, who was teaching physical sciences at Rochester’s East High School, is now recruiting 10th graders and showing them Rochester’s optics industry. Conrow presented the idea to the district superintendent, who had been principal in the only school in America with a student eyeglass program. He introduced Conrow to teachers at a sister high school where members of the cluster were helping to plan a precision optics program.
The Lithium-Ion Battery Modeling Challenge
Authors: Docimo Donald J. , Ghanaatpishe Mohammad , Rothenberger Michael J. , Rahn Christopher D. , Fathy Hosam I.
Published: July 2018

This article addresses various challenges associated with lithium-ion battery modeling. Lithium-ion batteries have a key role to play in mobile energy storage. One can potentially expand the envelope of lithium-ion battery performance, efficiency, safety, and longevity by using fundamental electrochemistry-based models for battery control. There are clear trade-offs between battery model fidelity and complexity, and a significant literature addressing these trade-offs. Electrochemistry-based battery models can be effective at capturing frequency-domain battery dynamics, especially at lower frequencies. When they are examined in this light, the commonalities between them and equivalent-circuit models become more visible. Constructing lithium-ion battery models certainly takes effort, and so does reducing these models for control design purposes. One important open challenge in lithium-ion battery modeling is the matching of sophisticated battery models to experimental data. Half-cell testing or insertion of a third reference electrode in a fuel cell can separate the contributions of the negative and positive electrodes, and researchers are pursuing other novel technologies for in-cell instrumentation and measurement.
The Quiet Forefront
Authors: Thilmany Jean
Published: July 2018

This article highlights the acoustical analysis changes made by manufacturers in design cycle. Acoustical simulation is being pushed from experts to designers, following the trend for the last 15 or so years that saw other types of engineering applications like finite element analysis and computational fluid dynamics become integrated with computer-aided design packages used by mechanical engineers. With the advent of software packages that allow for design and for acoustical analysis in tandem, design engineers are increasingly running these analyses early in the development cycle and are making design changes to decrease noise and vibration issues they find. Experts suggest that with speaker sound quality and other pertinent information in hand, designers can actually design from the get-go with that information in mind, resulting in fewer design changes down the line. Though early acoustical simulation is still perhaps one of the consumer electronics’ industries best-kept secrets, that’s likely to change as word gets out about the many advantages of front-line simulation.
Robot See Robot Do
Authors: Kaipa Krishnanand N. , Langsfeld Joshua D. , Gupta Satyandra K.
Published: July 2018

This article elaborates the concept of programming a robot by showing it how to do the job. This is often called “learning from demonstrations” or “imitation learning.” Labs at several institutions – for example, the Swiss Federal Institute of Technology at Lausanne, the University of Maryland, Massachusetts Institute of Technology, and Worcester Polytechnic Institute – are experimenting with technology that may one day make imitation learning common for machines. The underlying idea of this approach is to allow an agent to acquire the necessary details of how to perform a task by observing another agent (who already has the relevant expertise) perform the same task. Usually, the learning agent is a robot and the teaching agent is a human. Often, the goal of imitation learning approaches is to extract some high-level details about how to perform the task from recorded demonstrations. Research into imitation learning has achieved some impressive results ranging from training unmanned helicopters to perform complex maneuvers to teaching robots general-purpose manipulation tasks.
Impedance & Admittance-Based Coordination Control Strategies for Robotic Lower Limb Prostheses
Authors: Lawson Brian E. , Goldfarb Michael
Published: July 2018

This article presents and compares two different control systems for a powered knee and ankle prosthesis for transfemoral amputees, which were constructed to provide the user a safe, intuitive, and well-coordinated interaction with the prosthesis. The piecewise-passive impedance (PPI) controller utilizes only impedance-like behaviors, while the second – a hybrid impedance-admittance (HIA) controller – utilizes both impedance-like and admittance-like behaviors in a hybrid approach. The HIA approach maintains many of the desirable characteristics of the PPI controller while also reducing the number of selectable control parameters. The HIA approach essentially incorporates the PPI control structure during the early and middle stance phases of gait, and a trajectory tracking control approach in terminal stance and swing. These controllers were implemented on a powered knee and ankle prosthesis and tested in walking trials by a transfemoral amputee. Data from these trials indicate that both controllers achieve comparable performance with respect to healthy subject data, despite some substantial structural differences between the two.