bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement in Forced Convection by a Two Stage Corona Wind Generator
Authors: Mazumder A. K. M. Monayem H.
Published: February 2021

In this study, forced convection enhancement in a square channel by a two stage electrohydrodynamic (EHD) gas pump is numerically analyzed. This study is implemented for a two stage EHD gas pump with three emitting electrode configurations: 8, 24, and 56 respectively to seek their effectiveness in the enhancement of forced convection and pumping power requirement. The EHD gas pump is evaluated for a wide range of operating voltages starting from 20 kV up to 28 kV. The influence of electric field on the flow and temperature fields is also examined for a wide range of Reynolds numbers. The three-dimensional governing equations for the flow and temperature fields are solved using the finite volume method. The Reynolds numbers (Re) considered in this study varies in a range between 100 and 2000. At Re = 100, a maximum increase of 42% in the average Nusselt number is achieved with an applied voltage of 28 kV. The overall effectiveness of the EHD gas pump in heat transfer enhancement is evaluated by the thermal hydraulic performance parameter, (Nu/Nu0)/(f/f0), which is always greater than unity. These results disclose that EHD technique has a great potential for many engineering applications, particularly for thermal management.
Research on Flow and Heat Transfer Characteristics of Multiple Impinging Jets on a Moving Conveyor Belt
Authors: Liu Rui , Sun Yu , Ni Jun
Published: February 2021

Turbulent impinging jets at three different jet nozzle forms were numerically analyzed using the SIMPLE algorithm and k-epsilon turbulent model to investigate the flow field and heat transfer characteristics. The food placed upon a moving conveyor belt cooled by series of impinging jets under a specific condition. Three semi-confined domains with different jet nozzles were established, thereby with slot, rectangular, and funnel-shaped nozzles, respectively. Based on computational fluid dynamic (CFD) calculations, distributions of the temperature and wind velocity at four critical cross-sections of domains were compared. The results reveal that the freezing rate of foods mainly relates to temperature and wind velocity. For three semi-confined domains, the impinging jet with slot nozzles produces higher exit wind velocity, lower center temperature, and a better mass flow uniformity than others, which could better improve the heat transfer performance, and could increase the freezing rate of foods.
Finite Element Study of the Effect of Load Sequence on the Fretting Wear
Authors: Dhaka Pankaj , Prakash Raghu V.
Published: February 2021

Understanding the effect of load sequence is important in the context of a blade-disc dovetail joint in an aero-engine and many other such applications where, the mating surfaces undergo fretting wear under variable slip amplitude loading conditions. In the present work, a two-dimensional finite element analysis is carried out for a cylinder-on-plate configuration. The cylinder is modeled as deformable whereas the plate is modelled as rigid. An incremental wear modelling algorithm is used to model the wear of cylindrical pad while the plate is assumed as un-worn. This simulates a practical scenario where, generally one of the mating surfaces is sufficiently hardened or an interfacial harder/sacrificial element is inserted to restrict the wear to only one of the surfaces. A Fortran-based ABAQUS® subroutine UMESHMOTION is used to simulate the wear profile for the cylinder. A constant extrapolation technique is used to simulate 18000 cycles of fretting. The finite element analysis results are validated with the analytical solutions and literature data. The fretting wear modelling is carried out for two different slip amplitudes viz., 25 μm and 150 μm, to simulate the low and high slip amplitude loading respectively. Two blocks of alternate low and high slip amplitudes are applied to understand the influence of load sequence. Important contact parameters viz., contact pressure, contact stresses and contact slip are extracted. A comparison is made between the low-high and high-low load sequence based on the contact tractions and worn out profiles.
Human-Machine Teaming: A Movement-Focused Approach
Authors: Fukuda Shuichi
Published: February 2021

To cope with today’s frequent, extensive and unpredictable changes, humans and machines need to work together on the same team. Team organization and management called for now is to develop a truly adaptable network without any constraints. Movement works as a communication tool for the human-machine team, and in addition, movement will bring emotional harmonization between humans and machines and psychological satisfaction and happiness to humans. Although instinct has been neglected in traditional engineering, it plays an important role to coordinate many body parts and balance our bodies, and for interactive holistic perception and for making better decisions. Emerging reservoir computing will produce extremely small devices so they will work together on us and enable us to interact directly with the outside world through our bodies. And such human-machine team will motivate us to challenge rehabilitation and healthcare, which, therefore, will become a kind of a game, But to achieve this goal, a holistic and quantitative performance indicator is necessary. Euclidean Space approach requires orthonormality and units. But to manage movements, we must be free from these constraints. Therefore, Mahalanobis Distance-Pattern Approach, which is non-Euclidean, is proposed.
The Topology Within Recirculating Flow in the Atomic Layer Deposition Thin Film Process
Authors: Coetzee Rigardt Alfred Maarten , Hoenselaar Damon James , Bhamjee Muaaz , Jen Tien-Chien
Published: February 2021

Nanotechnology fabrication has become a popular field in the development of advanced and cutting-edge technologies. Deposition processes are industrialized to achieve nano-thin films with absolute control over the film thickness, conformal and uniform film growth over complex structures, and minimal to no defects or pinholes. Atomic layer deposition (ALD) has revealed itself as a possible candidate to achieve these requirements. However, the in-depth understanding of the physical and chemical formation of the thin film is still unfamiliar to reactor designers, engineers and scientists. For the purposes of this study, the interest involves the mechanistic factors of geometry influences, fluid flow, and mass transportation on the heterogeneous chemical reaction process. Through an industrial ALD process recipe, the transitional and recirculation phenomena observed in the Atomic Layer Deposition (ALD) thin film process are seen to exert a significant influence on the effective formation and growth of the thin film on the substrate. Topological fluid dynamics are used to analyze the two-dimensional numerical simulations of the backward-facing step (BFS) phenomena and the recirculation flow patterns typically found within a horizontal ALD reactor. Focus is placed on investigating the saddle points in the resulting vortex shedding, eddy distortion and recirculation due to the BFS phenomena. The topological analysis is conducted for symmetrical step heights of 7.5mm and 10 mm respectively. Findings revealed close similarities to experimental studies.
Digital Image Correlation Method in Measuring the Out of Plane Displacement: A Case Study on an Artificial Intervertebral Disc
Authors: Raheem Hassan M. , Rochefort Willie “Skip” E. , Bay Brian K.
Published: February 2021

We have developed a simple, low-cost, and innovative design — known as a “disc emulator” to mimic the mechanical response of a motion segment (vertebra - intervertebral disc-vertebra) of the human spinal column under axial compression loads. The disc emulator consists of upper and lower components that mimic the human vertebrae and a middle component that represents the annulus fibrosus (AF). This study aims to investigate the effects of changing the stiffness of artificial annulus fibrosus of the disc emulator on the bulging measurements while performing compression tests on the disc emulator. A non-contact measurement — digital image correlation (DIC) — was used for the bulging measurements. The results show that the bulging at the posterior region for the discs without nucleus pulposus (NP) bulged inwards, but the bulging at the posterolateral region was outwards, which accords with the reported behavior of the human disc, for the disc without and with NP regardless of the stiffness of the discs. Changing the stiffness of the artificial annulus fibrosus (AAF) alters the bulging magnitudes in the disc, which shows similar responses with respect to the available data on the human disc. The emulator provides a convenient experimental platform for evaluating normal and pathological disc states and assessing the biomechanics of potential therapeutic interventions.
Validation of a Physics Based Three Phonon Scattering Algorithm Implemented in the Statistical Phonon Transport Model
Authors: Medlar Michael P. , Hensel Edward C.
Published: February 2021

Three phonon scattering is the primary mechanism by which phonon transport is impeded in insulating and semiconducting bulk materials. Accurate computational modeling of this scattering mechanism is required for high fidelity simulations of thermal transport across the ballistic (quantum mechanics) to Fourier (continuum mechanics) range of behavior. Traditional Monte Carlo simulations of phonon transport use a scaling factor such that each scattering event is considered representative of a large number of phonons, often on the order of 104 physical phonons per simulated event. The ability to account for every phonon scattering event is desirable to enhance model fidelity. A physics-based model using time dependent perturbation theory (Fermi’s Golden Rule) is implemented to compute three phonon scattering rates for each permissible phonon interaction subject to selection rules. The strength of the interaction is based on use of a Gruneisen-like parameter. Both Type I and Type II scattering rates are computed for the allowable interactions that conserve energy and momentum (up to the addition of a reciprocal lattice vector) on a given discretization of momentum space. All of the phonons in the computational domain are represented and phonon populations are updated in momentum space and real space based on the computed number of phonons involved in given scattering events. The computational algorithm is tested in an adiabatic single cell of silicon of dimension 100 × 100 × 100 nm at a nominal temperature of 500 Kelvin containing approximately 108 fully anisotropic phonons. The results indicate that phonon populations return to equilibrium if artificially displaced from that condition. Two approaches are introduced to model the relaxation time of phonon states: the single mode relaxation time (SMRT) which is consistent with the underlying assumptions for previously reported theoretical estimates, and the multi model relaxation time (MMRT) which is more consistent with in-situ conditions. The trends meet physical expectations and are comparable to other literature results. In addition, an estimate of error associated with the relaxation times is presented using the statistical nature of the model. The three phonon scattering model presented provides a high fidelity representation of this physical process that improves the computational prediction of anisotropic phonon transport in the statistical phonon transport model.
Construction and Performance Analysis of a Two-Stage Traveling-Wave Thermo-Acoustic Generator
Authors: Shamase H. S. , Tartibu L. K.
Published: February 2021

Thermo-acoustic technology offers the possibility to convert heat energy into a sound-wave that can potentially be used to generate electricity through a linear alternator. The construction of a two-stage traveling-wave thermo-acoustic generator is described in this paper. The potential of conversion of heat into electricity has been investigated experimentally. The effect of the geometrical configurations of the thermo-acoustic system on its performance has been analyzed. The two thermo-acoustic engine cores were tested separately and subsequently combined to build a two-stage system. Two different configurations of engine cores have been considered namely series and parallel configuration. Hence, the effect of the orientation of the engine core has been investigated to get an insight into its effect on the output of the device. Parallel arrangement was found to be the most efficient configuration. An onset time of 3.15 minutes was recorded for the device to generate a sound wave. This system has achieved 125.7 dB corresponding to an output voltage of 486 mV. This study guides the development of more efficient electricity generators using thermo-acoustic technology.
Virtual Commissioning for Advanced Manufacturing Using Digital Tools
Authors: Guerra-Zubiaga David , Kamperman Kevin , Aw Mohamed
Published: February 2021

Following the Industry 4.0 paradigm with the rise of smart factories, there is a growing need in exploring digital manufacturing tools compatible with Industrial Internet of Things (IIoT) functionalities. This paper discusses the concept of Virtual Commissioning (VC) including applications in present and near-future advanced automation and production. Specifically, global trends towards Industry 4.0 and virtual manufacturing processes are explored in addition to how and why these emerging technologies could be applied. Furthermore, the advantages of VC processes are contrasted to Traditional Physical Commissioning (TPC) to highlight the evolution of Product Lifecycle Management (PLM) software and the optimization of manufacturing processes since the turn of the century. This research aims to use state-of-the-art PLM software to replicate a physical prototype in near-perfect functionality to demonstrate the effectiveness of VC in an industrial setting. Developing a methodology for this research, the analysis is followed by a case study involving a Mini Festo Pick-and-Place (P&P) unit simulated in Siemens Tecnomatix Process Simulate and controlled via ladder logic executed in Totally Integrated Automation (TIA) Portal. As expected, the results of this case study validate the potential for optimized contemporary manufacturing solutions in which higher-quality goods are reliably produced with minimal delays at all-time low principal investments through the use of VC tools.
Improved Process Control Using Hybrid Industrial Internet of Things Network Topology
Authors: Guerra-Zubiaga David , Strickland Jay , Kamperman Kevin , McHale Ryan , Nasajpour-Esfahani Navid
Published: February 2021

Industry 4.0 is an important manufacturing paradigm driving research and the enhancement of Industrial Internet of Things (IIoT) technologies on a global scale. The expanding capabilities of IIoT technologies has risen to meet customer demand for intelligent, interconnected devices. Legacy Programmable Logic Controllers (PLCs) remain the industry standard for manufacturing and process control even though Free and Open Source Software (FOSS) has emerged as a feature-rich market alternative. This paper compares and contrasts traditional closed systems and new FOSS in the context of Industry 4.0 trends through a literature review and reports on the resultant capabilities of their synthesis. A methodology for linking these previously independent systems through IIoT is presented via case study using a mobile autonomous robot to interact automatically with a custom process control training bench (PCTB) in a scenario analogous to a mobile delivery robot. The novelty of this research is the synthesis of traditional closed and open systems across a new class of smart device, the semi-proprietary IIoT network bridge. Hybridization, it is concluded, presents the most advantageous features of both proprietary systems and FOSS without many of the trade-offs typically encountered when employing technologies under either paradigm.
Incorporating 3D Printing to Bridge Two Introductory Courses in Mechanical Engineering
Authors: Denizhan Onur , Chew Meng-Sang
Published: February 2021

A course in Computer Graphics using SolidWorks™ is one of the very first courses that a Mechanical Engineering major would take within the department at Lehigh University. In this course, students learn the basics of engineering graphics with a view towards engineering design. Such a course gives students an overall view of not just the mechanics of creating engineering drawings using SolidWorks, but also one of understanding the consequences of their drawings as they affect tolerances, material selection, fabrication processes as well as the viability of their designs. The very next introductory mechanical engineering course is a laboratory dealing with engineering measurements, data acquisition and testing. This article reports on the use of a 3-D printing exercise to bridge these two somewhat very different courses with different objectives, thereby giving students an early start into understanding the process of design; from a concept to its design and fabrication, and finally, testing and analysis of data. Moreover, it gives a fundamental understanding of the use of 3-D printing that many students would end up using for their Senior Design course in their senior year.
Machining Characteristics Estimation in WEDM Process While Machining Titanium Grade-2 Material Using ANN
Authors: Sudhir Prathik Jain , Holalu Venkatadas Ravindra , Gonchikar Ugrasen
Published: February 2021

Wire Electrical Discharge Machining (WEDM) provides an effective solution for machining hard materials with intricate shapes. WEDM is a specialized thermal machining process is capable to accurately machining parts of hard materials with complex shapes. However, selection of process parameters for obtaining higher machining efficiency or accuracy in wire EDM is still not fully solved, even with the most up-to-date CNC WED machine. The study presents the machining of Titanium grade 2 material using L’16 Orthogonal Array (OA). The process parameters considered for the present work are pulse on time, pulse off time, current, bed speed, voltage and flush rate. Among these process parameters voltage and flush rate were kept constant and the other four parameters were varied for the machining. Molybdenum wire of 0.18mm is used as the electrode material. Titanium is used in engine applications such as rotors, compressor blades, hydraulic system components and nacelles. Its application can also be found in critical jet engine rotating and airframes components in aircraft industries. Firstly optimization of the process parameters was done to know the effect of most influencing parameters on machining characteristics viz., Surface Roughness (SR) and Electrode Wear (EW). Then the simpler functional relationship plots were established between the parameters to know the possible information about the SR and EW. This simpler method of analysis does not provide the information on the status of the material and electrode. Hence more sophisticated method of analysis was used viz., Artificial Neural Network (ANN) for the estimation of the experimental values. SR and EW parameters prediction was carried out successfully for 50%, 60% and 70% of the training set for titanium material using ANN. Among the selected percentage data, at 70% training set showed remarkable similarities with the measured value then at 50% and 60%.
Development and Performance Evaluation of a Dynamic Compressed Air Energy Storage System
Authors: Kabinga R. K. N. , Tartibu L. K. , Okwu M. O.
Published: February 2021

Renewable and clean energy are safe sources for powering the world in the future. The use of fossil fuels in the transportation sector produces 15 to 20 % of greenhouse gas emissions. To solve this problem, renewable energy sources are being considered for use in the domain of transportation, and compressed air energy is one of them. But the efficiency of the compressed air powered systems depends largely on its energy storage density. In this paper, the performance of two distinct compressed air reservoirs for energy storage in small scale systems was investigated. Two air compressors fitted with static reservoirs were utilized for the experiment. The first air compressor was driven by an internal combustion engine (ICE) and the second was driven by an electric motor. The experimental results were used to provide a frame of reference for the computer (MATLAB) simulation on the dynamic reservoir. Additionally, the dynamic reservoir, which is a system fitted with a piston and spring, was analyzed considering three different spring stiffness. This study showed that the dynamic reservoir provides a consistent and better performance during the charging and discharging process, affecting positively the behavior of the pressure and the compressed air mass flowrate.
Molecular Dynamics Analysis of the Acceleration of Intergranular Cracking of Ni-Base Superalloy Caused by Accumulation of Vacancies and Dislocations Around Grain Boundaries
Authors: Kikuchi Ryo , Suzuki Shujiro , Suzuki Ken
Published: February 2021

Ni-based superalloys with excellent high temperature strength have been used in advanced thermal power plants. It was found that grain boundary cracking is caused in the alloy under creep-fatigue loading due to the degradation of the crystallinity of grain boundaries and the grain boundary cracking degrades the lifetime of the alloy drastically. In order to clarify the mechanism of intergranular cracking, in this research, static and dynamic strains were applied to a bicrystal structure of the alloy perpendicularly to the grain boundary using molecular dynamics analysis. In addition, the effect of the accumulation of vacancies in the area with high-density of dislocations on the strength of the bicrystal structure was analysed. It was found that the fracture mode of the bicrystal structure changed from ductile transgranular fracture to brittle intergranular one as strong functions of the combination of Schmid factor of the two grains and the density of defects around the grain boundary. The local heavy plastic deformation occurred around the grain boundary with large difference in Schmid factor between nearby grains and the diffusion of the newly grown dislocations and vacancies was suppressed by the large strain field due to the large mismatch of the crystallographic orientation between the grains. The accumulation of vacancies accelerated the local plastic deformation around the grain boundary. Therefore, the mechanism of the acceleration of intergranular cracking under creep-fatigue loading was successfully clarified by MD analysis.
Subsonic Stall Flutter of a Linear Turbine Blade Cascade Using Experimental and CFD Analysis
Authors: Slama Vaclav , Rudas Bartolomej , Ira Jiri , Macalka Ales , Eret Petr , Tsymbalyuk Volodymyr
Published: February 2021

Stall flutter of long blades influences the operation safety of the large steam turbines in off-design conditions. As angles of attack are typically high, a partial or complete separation of the flow from the blade surface occurs. The prediction of stall flutter of turbine blades is a crucial task in the design and development of modern turbomachinery units and reliable design tools are necessary. In this work, aerodynamic stability of a linear turbine blade cascade is tested experimentally at high angle of attack +15°, Ma = 0.2 and the reduced frequency of 0.38. Controlled flutter testing has been performed in a travelling wave mode approach for the torsion with the motion amplitude of 0.5°. In addition, ANSYS CFX with SST k-ω turbulent model is used for URANS simulations of a full-scale computational domain. A separation bubble formed on suction surface near the leading edge has been found in CFD results for each blade. Excellent agreement between the experimental and numerical results in stability maps has been achieved for this case under investigation. This is encouraging and both experimental and numerical techniques will be tested further.
Identification of Variation Sources for High Precision Fabrication in a Digital Twin Context
Authors: Hultman Hugo , Cedergren Stefan , Söderberg Rikard , Wärmefjord Kristina
Published: February 2021

The aerospace industry is increasing its focus on fabrication in manufacturing, foregoing large castings to instead assemble and join smaller parts into final products. This increases the total amount of geometrical variation introduced during the production process, since the unique variation from each individual part can add to a propagating effect putting the final assembled product outside of tolerance limits. Geometry assurance and variation simulation has traditionally been applied as a part of the design process to develop robust manufacturing concepts that are as insensitive as possible to variation. A concept for geometry assurance has been proposed where variation simulation is conducted for each individual assembly using real measurements from incoming parts, making it possible to make adaptive adjustments to production parameters to optimize results. It is however not feasible to measure and simulate every aspect of the process. This paper provides a summary of relevant sources of geometrical variation for a high precision fabrication process, based on input from a fabrication process in the aerospace industry. Variation sources are analyzed and discussed from an industrial perspective, putting them in the context of an actual fabrication process as well as in the context of digital twins for geometry assurance.
Walking Speed Estimation From a Wearable Insole Pressure System Using a Bayesian Regularized Back Propagation Neural Network
Authors: Wei Wang , Kaiming Yang , Yu Zhu , Yuyang Qian , Chenhui Wan , Min Li
Published: February 2021

In this study, we introduced a machine learning method for estimating human walking speed using plantar pressure and acceleration data. A pressure-derivative based with pretest feature selection method was proposed to extracted speed-related features from plantar pressure sensors. The maximum, minimum and standard deviation of acceleration data were also selected as neural network inputs. To improve the generalization ability of the neural network, a Bayesian regularization method was adopted. To validate the performance of the proposed method, experiments were conducted under seven different walking speeds. The results show that a strong linear correlation (R = 0.995) exists between the estimated and the actual walking speeds. The average error of the proposed method is 0.003 ± 0.043 m/s (mean ± root mean square error), which is better than previous works. The desirable performance of the proposed method proves that including the speed-related information of both stance and swing phase is beneficial for improving the accuracy of walking speed estimation.
Peristaltic Roller Pump: Parametric Optimization for Hemolysis Control
Authors: Capata Roberto
Published: February 2021

This work aims to analyze the various types of peristaltic pumps by studying, in particular, the use of the peristaltic roller pump to highlight its critical issues and propose new effective and innovative solutions. One possible application of this device is in hemodialysis, which is a physical therapy substitution of kidney function that allows, in almost all cases, recovery and maintenance of the main biological functions while remaining the uremic condition. As for the extracorporeal one, the equipment used to purify the blood from toxic substances that are no longer normally eliminated by kidney filtration is divided mainly into two types: rotary peristaltic pump and a linear peristaltic pump. Having to work with a very particular fluid such as blood and in direct contact with the patient, they need to be extremely accurate and must ensure a constant and continuous functioning. The rotary peristaltic pump is the most widely used for hemodialysis and having been extensively studied in literature it has since found extensive solutions in the application field. As is well known, peristaltic pump refers to a device that exploits the principle of peristalsis to function, i.e. the transit of a bottleneck on a tube, in this case, the catheter, to push the fluid contained outwards. In particular, a roundabout peristaltic pump consists of a rotating structure consisting of two or more rollers that in turn revolve around their axis. With their displacement, the rollers clog adjacent catheter sections at a time so that after the first roller has passed the tube returns to its initial size creating the vacuum and then sucking the fluid. In this way, the liquid is pushed from the tube towards the patient. The motion of all these components is powered by an electric motor connected directly to the main rotating structure. The pumping of fluids through hoses using the propagation of a peristaltic wave has been the subject of design and scientific studies for more than 4 decades. This is easily justifiable since the phenomenon of peristalsis is known to be an important responsible mechanism of fluid transport in many biological organs. The goal is (starting on studies on the blood, a variable density fluid) to analyze in detail the peristaltic roller pump and propose its parametric optimization, aimed at determining the critical speed, beyond which the machine damages any kind of fluid that needs special treatment (blood, food, special gel, medical ointments and so on).
Powdered Metal Heat Treatment Apparatus Designed for a Laboratory
Authors: Porter Jacob , Parmigiani John
Published: February 2021

Metal additive manufacturing is a rapidly growing and sophisticated industry however the manufacturing processes and equipment for the heat treatment of the needed powdered metals is underdeveloped. Heat treatment is a key step in the powdered metal production process and is often needed to produce desired material properties. The objective of this paper is to examine the design of a heat treatment machine that addresses the needs of a laboratory performing research on powdered metals. The device was designed to address the three criteria of a heat treatment device; treatment, environment, and containment. The treatment criterion is accomplished by continuous powder flow through a furnace. The environment criterion is accomplished through a gas handling system capable of creating both an argon and vacuum environment. Finally, the containment criterion is accomplished through a network of tubes that provides structure to contain the powder. The design of this machine will allow research and development labs to heat treat powdered to a higher quality at a significantly faster rate.
Francis Turbine Operation at Excess Flow Rate Using Large Eddy Simulation: The Effect of Water Injection
Authors: Altimemy Muhannad , Caspar Justin , Watheq Saif , Oztekin Alparslan
Published: February 2021

High-fidelity Large Eddy Simulations (LES) were conducted to characterize the spatial and temporal structure of turbulent flows in an industrial-sized Francis turbine running at 120% of the design flow rate. Injection at a 4% and 8% flow rate is applied and investigated as a mitigation method for pressure-induced fluctuations along the draft tube. Contours of velocity and vorticity in the draft tube are presented to examine the effects of water injection. Probes placed alongside the draft tube measure the pressure signal and compare both operational regimes to characterize the pressure fluctuations. The intensity of pressure fluctuations along the draft tube wall is an order of magnitude smaller compared to that at the center. As the injection is applied, the intensity of the pressure fluctuations along the draft tube wall is increased while the intensity of pressure fluctuations in the center of the draft tube is reduced. Pressure probes in the center of the draft tube measure an 86% to 57% reduction in amplitude for 4% to 8% flow rate injection, respectively. There is a 30% to 40% increase in fluctuations along the wall for 4% to 8% flow rate injection, respectively. These changes in flow structure are due to the dissipation of the vortex rope as the injection is applied.
Robotic Handling of Jet Engine Turbine Blade Using Collaborative Robot
Authors: Sahay Prateek , Dong Janet , Bisig Caleb , Ma Ou
Published: February 2021

The work discussed in this paper is a part of the project to build an automated robotic cell for removing two tabs from a Jet Engine Turbine Blade using a 3-axis CNC milling machine and for laser marking several lines of part information onto the blade body. The two tabs are extensions of the Turbine Blade, in which the necessary part information is ingrained. The part information is used as the identification of the Turbine Blade throughout its entire manufacturing process. The two tabs also serve as anchors during the milling of the body of the Turbine Blade in a 5-axis CNC machine. Once the milling of the blade body is done, the two tabs will be removed from the blade body. Removing tabs is currently being done in the same 5-axis CNC milling machine. It is expensive and wastes 5-axis machine time. Therefore, using a 3-axis CNC milling machine to remove tabs is proposed with a robot to tend machines to be cost-effective. Due to the complexity of the Turbine Blade having 3-D wavy geometry, it adds challenges in undertaking any operations on the blade with automation.

As automation is becoming relevant in many industries including the Aerospace, the method discussed in this paper can be used as a general guideline for carrying out material handling tasks with a thin part of wavy geometry by using a collaborative robot.
Airfoil Deterministic Lateral Displacement for High-Throughput Particle Separation in Viscous Fluids
Authors: Senf Brian , Ahasan Kawkab , Kim Jong-Hoon
Published: February 2021

Deterministic Lateral Displacement (DLD) is an inertial size-based particle separation technique with great possibilities for use with biological sample preparation. Recently it has been shown that particle shift of a DLD is highly dependent on the Reynolds number. Additionally, particle trajectory has been characterized in a high throughput airfoil array DLD with varying Angle of Attack (AoA) in Deionized water. The AoA can be shifted negatively assisting in particle trajectory increases at low Reynolds numbers. With variations in fluid viscosity, particle trajectories compared to Reynolds value should theoretically have a constant and similar slope. In this work, various viscosities are tested in a DLD with a neutral and negative AoA to eventually characterize non-Newtonian fluids within a DLD. Due to higher viscosities increasing the internal pressure of the device, the negative AoA DLD shows promising results at higher range viscosities due to its ability to shift particles at lower Reynolds numbers.
An Approach to Bayesian Optimization in Optimizing Weighted Tchebycheff Multi-Objective Black-Box Functions
Authors: Biswas Arpan , Fuentes Claudio , Hoyle Christopher
Published: February 2021

Bayesian optimization (BO) is a low-cost global optimization tool for expensive black-box objective functions, where we learn from prior evaluated designs, update a posterior surrogate Gaussian process model, and select new designs for future evaluation using an acquisition function. This research focuses upon developing a BO model with multiple black-box objective functions. In the standard multi-objective optimization problem, the weighted Tchebycheff method is efficiently used to find both convex and non-convex Pareto frontier. This approach requires knowledge of utopia values before we start optimization. However, in the BO framework, since the functions are expensive to evaluate, it is very expensive to obtain the utopia values as a priori knowledge. Therefore, in this paper, we develop a Multi-Objective Bayesian Optimization (MO-BO) framework where we calibrate with Multiple Linear Regression (MLR) models to estimate the utopia value for each objective as a function of design input variables; the models are updated iteratively with sampled training data from the proposed multi-objective BO. The iteratively estimated mean utopia values are used to formulate the weighted Tchebycheff multi-objective acquisition function. The proposed approach is implemented in optimizing a thin tube design under constant loading of temperature and pressure, with multiple objectives such as minimizing the risk of creep-fatigue failure and design cost along with risk-based and manufacturing constraints. Finally, the model accuracy with and without MLR-based calibration is compared to the true Pareto solutions. The results show potential broader impacts, future research directions for further improving the proposed MO-BO model, and potential extensions to the application of large-scale design problems.
Estimation of Endpoint Impedance of a 2D Parallel Manipulator Using Numerical Simulation Experiments
Authors: Regmi Sambad , Song Yun Seong
Published: February 2021

While endpoint impedance of manipulators can be modulated through feedback control, it may not be feasible to reduce it below a certain bound that is dictated by the inherent mechanical characteristics of the robot. In applications where the endpoint impedance of a robot arm needs to be modulated within a large range, it is beneficial to have a method that can estimate the passive characteristics (endpoint inertia and endpoint damping) of the robot arm as early as in the design phase, and use this information to modify the design, if necessary, before building the prototype. In our previous work, we developed a numerical simulation method to estimate 1-D endpoint impedance that is applicable only to limited scenarios. In this article, we present a new numerical simulation method to estimate the 2-D endpoint impedance for any general 2-D manipulators at various locations inside the workspace. We show that our method accurately estimates the endpoint inertia and presents feasible estimates of endpoint damping through numerical simulations. An analysis of the feasibility of using the robot for interaction tasks — based on the obtained impedance characteristics — is also discussed. With our method, robot output impedance can be tailored as early as in the design phase.
Numerical Analysis of Load Transfer Mechanism in Fiber-Reinforced Composites Enhanced by Zinc Oxide Nanowires
Authors: Marashizadeh Parisa , Abshirini Mohammad , Saha Mrinal , Liu Yingtao
Published: February 2021

In this study, a three-dimensional model of single carbon-fiber composites enhanced by radially grown zinc oxide (ZnO) nanowires is investigated numerically. Due to the different length scales of the composites and the theories used in the system, a multi-scale analysis is employed to simulate the behavior of the fiber-reinforced composites. The effective mechanical properties of the enhancement layer are extracted at the micro-scale by the homogenization analysis of an appropriate representative volume element. The fiber interface is modeled at the meso-scale utilizing the cohesive zone method. A thin layer of interface with the cohesive element is modeled around the fiber. The material properties of the interface are evaluated based on the properties of fiber and the enhancement layer. The macro-scale damage behavior of fiber is defined by user-defined mechanical material behavior. Single fiber fragmentation test is simulated in ABAQUS by applying the tensile loads on the structure. The load transfer mechanism is evaluated by capturing the number of fiber fragmentation and calculating the interfacial shear strength. The effect of different ZnO diameters and volume fractions are also investigated. The results show stronger interface and higher load transfer capacity in the enhanced composite compared to the bare composite.
On the Use of the Accident Dynamic Simulator Method in Ship Collision Accident Analysis
Authors: Shi Shuquan , Wang Tengfei , Diaconeasa Mihai
Published: February 2021

This paper proposes a maritime Accident Dynamic Simulator (MADS) method from one ship’s perspective of ship collision accident. The MADS model is built based on discrete dynamic event trees (D-DET) to generate the time-dependent ship collision accident scenarios. According to the characteristics of maritime activities, such as high freedom of participation, the big influence of the environment, and the high uncertainty, the MADS method is modified, and the analyzed ship collision scenario is reasonably simplified. Both crews’ decision-making process and ship manoeuvre are fully discretized to generate new branches of the D-DET. The interactions between encountered ships are modelled with an information transfer model to form the uncertainties between two ships. The MADS consists of physical simulation engine, crew response and interaction model, reliability model of the system hardware, functional model of human-system interfaces and event sequence controlling model. The MADS starts with a pre-set initiating event under a specific situation. Event branches are discretely generated based on probable alternative state changes of operator response or system evolution. The output probability of an end state can be calculated in the same way with the conventional event tree after the whole scenario completed. At the end of the paper, an accident case study is used to verify the efficiency of the ADS.
Characterizations of Crack Growth Behavior of Porous Polymer Membranes Using Digital Image Correlation and Finite Element Method
Authors: Kodaira Yasuhisa , Miura Tatsuma , Ito Shoma , Yonezu Akio , Nagatsuka Hideki
Published: February 2021

This study investigated the crack growth behavior of porous polymer membranes, experimentally and numerically, in order to clarify the criterion of crack growth. A notch was introduced into the membrane as an initial crack (pre-crack) and a uniaxial loading was applied for the stable crack propagation. During the test, crack propagation behavior was observed using a CCD camera and Digital Image Correlation (DIC) method. The strain around the pre-crack tip at the onset of crack propagation was measured experimentally using DIC method. It was clarified that large-scale yielding developed before the onset of crack growth. The stable crack propagation was observed for all tensile tests. In parallel, a homogenized model that mimicked porous polymer membrane was created using finite element method (FEM) in order to investigate stress/strain distribution around the crack tip. This study employed the yield criterion proposed by Deshpande and Fleck. The computed strain distribution was compared with that of experiment, showing a good agreement each other. By using strain distribution from DIC method and FEM computation, J-integral value was calculated to investigate the criterion of crack growth. Regardless of the initial crack length, it is found that the J-integral value at the initiation of crack growth becomes constant for all tests. It is concluded that we successfully determined the criterion of crack propagation of porous polymer membrane. Therefore, our study using DIC experiment and FEM computation is useful to clarify the crack growth behavior of porous polymer membrane and determines the criterion of crack propagation.
The Condition of Dynamic Stability for Self-Paced Treadmill Walking Based on Inverted Pendulum Model
Authors: Qian Yuyang , Yang Kaiming , Zhu Yu , Wang Wei , Wan Chenhui
Published: February 2021

A self-paced treadmill automatically adjusts speed in real-time to match the user’s walking speed, presumably leading to a more nature gait than fixed-speed treadmill. However, previous study has proven that the acceleration applied to the subjects would influence the gait stability. In order to have insights on to which extent will the accelerations affect gait stability, simulation analysis based on conceptual model has been done in the current study. This paper utilized a non-inertial frame based spring-loaded inverted pendulum model to analysis the condition of stability during continuous self-paced treadmill walking. Simulations were done for 100 continuous self-paced treadmill walking at the normal walking speed. And 10ms impulse accelerations of different magnitudes with the range of (−1g, 1g) were applied at different gait events such as toe-off, foot-flat and heel-strike. The simulation results showed that the magnitude of the accelerations had significantly influence on continuous self-paced treadmill walking and directional-dependency was also found. However, no significantly difference was found when applying the impulse acceleration at different gait events.
Driving Wetting Transitions on Textured Surfaces Using Ultrasonic Vibration
Authors: Trapuzzano Matthew , Crane Nathan , Guldiken Rasim , Tejada-Martínez Andrés
Published: February 2021

Adhesives, medical devices, and many cleaning products depend on the wetting of liquids on solid surfaces. The liquid/solid interaction depends on chemistry, surface topology, and external energy input. For instance, surfactants are commonly used in cleaning solutions to improve their effectiveness, and electrical fields are frequently used to control the contact angle of liquid droplets. Low frequency vibration has been used to spread, move, and manipulate droplets using the mode shape oscillations of the droplet to displace the contact line. Ultrasonic vibration (above 20 kHz) can also cause a liquid droplet to wet or spread out on a solid surface under the right circumstances. We have previously demonstrated that ultrasonic vibration can be used to control the wetting/spreading of liquid droplets on smooth hydrophobic surfaces and that the response is relatively insensitive to excitation frequency or fluid properties [1]. This paper reports on the use of ultrasonic vibration to initiate spreading on surfaces with etched pillars. Ultrasonic vibration successfully initiated a transition from Cassie to Wenzel states in all geometries with no apparent need to tune excitation frequencies to the geometry. However, the magnitude of the acceleration required to initiate the transition decreased with increased pillar spacing. For small pillar spacing, some smooth spreading in the Cassie wetting mode was observed before transition.
Static Strength Reliability Analysis of the FLNG Compact and High Efficient Heat Exchanger
Authors: Tang Xu , Liu Tao , Song Wei , Wang Hongpu
Published: February 2021

Because of the harsh marine environment and limited offshore natural gas liquefaction work space, the compact and high efficient heat exchanger is the best choice for FLNG (floating liquefied natural gas) heat exchanger. To optimize the heat exchanger’s structural parameters and improve the performance, the factors mostly affecting the strength of the heat exchanger need to be determined, and static strength analysis and reliability analysis should be required. The strength of the heat exchanger core is analyzed by using the Static Structural, and the stress intensity distribution is obtained. According to the operation conditions, the temperature boundary condition has been set and the mechanical stress and thermal stress are considered to evaluate the strength. By choosing the thickness between the cold channels, cold channel pressure, hot channel pressure and elastic modulus as input random variables, the reliability analysis of heat exchanger has been done by using the Six Sigma Analysis of ANSYS Workbench, and next the cumulative distribution function curves of the membrane stress intensity, membrane plus bending stress intensity, response surface and the sensitivity are obtained. The reliability analysis results have shown that the cold channel pressure loading is found to be the greatest factor to the structural strength. The reliability of the heat exchange is more than 99.9% without considering thermal stress.