bluuebunny/crossref_metadata_2025 huggingface dataset:
Best Structural Theories for Free Vibrations of Sandwich Composites via Machine Learning
Authors: Petrolo Marco , Carrera Erasmo
Published: January 2020

This work presents a novel methodology for the development of refined structural theories for the modal analysis of sandwich composites. Such a methodology combines three well-established techniques, namely, the Carrera Unified Formulation (CUF), the Axiomatic/Asymptotic Method (AAM), and Artificial Neural Networks (NN). CUF generates structural theories and finite element arrays hierarchically. CUF provides the training set for the NN in which the structural theories are inputs and the natural frequencies targets. AAM evaluates the influence of each generalized displacement variable, and NN provides Best Theory Diagrams (BTD), i.e., curves providing the minimum number of nodal degrees of freedom required to satisfy a given accuracy requirement. The aim is to build BTD with far less computational cost than in previous works. The numerical results consider sandwich spherical shells with soft cores and different features, such as thickness and curvature to investigate their influence on the choice of generalized displacement variables. The numerical results show the importance of third-order generalized displacement variables and prove that the present framework can be of interest to evaluate the performance of any structural theory as typical design parameters change and provide guidelines to the analysts on the most convenient computational model to save computational cost without accuracy penalties.
Investigation of Flashing Flow in a Siphon to Extract Condensate in Paper Dryer Application
Authors: Majeed Hamed Abdul , Wang Ting
Published: January 2020

The paper industry uses steam to dry paper web through cylinder dryers. As steam condenses inside the cylinder dryer, the condensate is removed by means of either a stationary or a rotary siphon. However, during the siphoning process for transporting the condensate, flashing of the condensate occurs, which could cause backflow or discontinuity in the siphoning process. To resolve this flashing issue, two approaches have been employed: (a) increasing the amount of steam supplied to the cylinder to “blow-through” the stalled condensate-steam mixture and (b) reducing the back pressure by inducing “suction” through a thermocompressor from downstream. This practice of employing push from the upstream and suction from the downstream requires excessively large amounts of high-grade steam, resulting in an estimated 10 to 15 %, 15 to 25%, and 40 to 90 % of blow-through steam for stationary siphons, rotary siphons, and Yankee dryers respectively. The objective of this study is to investigate and improve understanding of the flashing phenomena during condensate transport through the siphon and piping system in order to develop means to reduce this excessive steam consumption during the paper drying process. A computational fluid dynamics (CFD) simulation is performed that uses the Eulerian-Eulerian multiphase method. The steady-state case is first solved to obtain the flow field without flashing. Then the transient method is initiated by employing flashing and condensation models. The results show that reduction of local pressure triggers flashing, however, flashing in turn reduces local temperature, and subsequently induces condensation, resulting in an alternating flashing and condensation behavior. To maintain continuity of the siphon flow, the inlet pressure fluctuates corresponding to the variation of total vapor volume ratio inside the siphon. The results will be used to modify the current siphon system design and operating practices to reduce steam consumption.
Experiments on Vortex Shedding From Reconfigured Flexible Filaments Vibrating in Flow
Authors: Silva-Leon Jorge , Cioncolini Andrea
Published: January 2020

This paper describes an experimental study of the spanwise vortex shedding frequencies from cantilever flexible filaments which are bent (reconfigured) when exposed to air crossflow. At a reduced velocity of approximately U* = 1500 (based on filament diameter) the filaments started to vibrate in the inline direction. Hot-wire anemometry was thus employed to investigate the wake flow of filaments of three aspect ratios (L/D = 38, 80, and 113) at Reynolds numbers Re < 300. Despite the large relative inclination angles between the filament and the flow direction, the vortex shedding frequency measured along the span of the filaments remained close to those of a cylinder in pure crossflow. Moreover, it was found that as the aspect ratio (axial length) of the filaments was increased, vortex shedding lost coherence towards the free end of the filaments, whereas this was not the case for the shortest aspect ratio filament currently tested. This is thought to be due to the interaction between the crossflow vortex shedding and the axial flow component developing along the wake of the inclined filaments. Through comparisons with stiff inclined wires it was confirmed that the spanwise vortex shedding behaviors observed (frequency and coherence) were not modulated by the motions of the filaments.
Design of a Deformable Smart Tire Using Soft Actuator
Authors: Nandikolla Vidya K. , Costa Michael , Boyd Nathan , Rosales Gilberto
Published: January 2020

The unique functional properties of nickel-titanium Shape Memory Alloys (SMA) enable them to be used as actuators. This research paper demonstrates theoretically and experimentally the feasibility of using SMA in smart tires for a mobile robot. The design procedure for SMA as a coil spring actuator for a soft deformable wheel is described. The primary focus is the mechanical modeling, manufacturing, and system dynamics of a soft deformable wheel. The 3D printed soft tire exploits the capabilities of the SMA actuation using a voltage signal. The printed components are activated and integrated with electromechanical circuit for wireless communication system. The performance of the force feedback control system is evaluated at different operating conditions to demonstrate the shape-changing characteristic of the smart tire. The developed prototype is designed to propel forward and backward on flat and uneven surface. The experimental results obtained demonstrate the potential of SMA as soft actuators, its benefits and limitations as flexible systems.
A Method for Approximating the Mechanical Section Properties of Structural Members With Highly Complex Cross-Sections
Authors: Munsell W. P.
Published: January 2020

While mechanical section properties (such as the centroidal moment of inertia) of simple cross sections are easily calculated, those of highly complex structures (including organically-generated structures) defy such analyses. In this paper a method is described for approximating the mechanical section properties of highly complex cross-sections, and the factors affecting its accuracy are tested and its error rate is quantified. The method relies on the analysis of digital images of the subject cross-section and does not require extensive user expertise or investment in expensive FEA programs to implement. The limited file space necessary to install the required code means that standard smart phones could be used to directly evaluate the most complex cross-sections in the field.
Performance Variation of Nano-Scaled Devices in 3D-IC Packaging Architecture Induced by TSV Residual Stress
Authors: Lee Chang-Chun , Huang Pei-Chen , Wang Chi-Wei
Published: January 2020

Through-silicon via (TSV) technique, is widely adopted as the vertical interconnection technology of three-dimensional integrated circuit packaging architecture. However, fabrication process-induced residual stress occurred in TSV during annealing and introduced the subsequent thermal–mechanical stress into silicon-based interposer. Aforementioned residual stress will affect the performance and electric stability of p-type metal-oxide-semiconductor field-effect transistor (pMOSFET) located around TSV. Accordingly, this study is focused on the influences of TSV layout with intrinsic residual stress on concerned pMOSFET performance. Process-oriented finite element analysis (FEA) is performed to simulate stress distribution of pMOSFET when concerned device channel region was affected by TSV residual stress and embedded SiGe alloy. To conquer the difficulty of FEA construction on TSV and pMOSFET with significant scale mismatch in same FEA model, the global–local submodeling technology is adopted to manage the balance between model complexity and numerical convergence. The residual stress magnitude effect of different designed TSV diameter on concerned channel stress components is extracted to estimate its influence on pMOSFET with scaled gate width. The presented results indicated that increased TSV residual stress could obviously reduce performance of concerned device. It should be noted that the S/D stressor remarkably dominated mobility gain of strained pMOSFET.
Convergence of PIV Measurements at the Inlet of a Turbocharger Compressor
Authors: Banerjee Deb , Selamet Ahmet , Dehner Rick , Miazgowicz Keith
Published: January 2020

Particle Image Velocimetry has become a desirable tool to investigate turbulent flow fields in different engineering applications, including flames, combustion engines, and turbomachinery. The convergence characteristics of turbulent statistics of these flow fields are of prime importance since they help with the number of images (temporally uncorrelated) to be captured in order for the results to converge to a certain tolerance or with the assessment of the uncertainty of the measurements for a given number of images. The present work employs Stereoscopic Particle Image Velocimetry to examine the turbulent flow field at the inlet of an automotive turbocharger compressor without any recirculating channel. Optical measurements were conducted at five different mass flow rates spanning from choke to surge at a corrected rotational speed of 80 krpm. The velocity fields thus obtained were used to analyze the convergence of the mean (first statistical moment) and variance (second statistical moment) at different operating conditions. The convergence of the mean at a particular location in the flow field depends on the local coefficient of variation (COV). The number of required images for the mean to converge to a particular tolerance was also found to follow roughly a linear trend with respect to COV. While the convergence of the variance, on the other hand, did not appear to show any direct dependence on the coefficient of variation, it takes significantly more images than the mean to converge to the same level of tolerance.
Introduction of Prevention Engineering Into the Mechanical Engineering Curriculum
Authors: Bzymek Zbigniew M. , Brown Eliot
Published: January 2020

In today’s fast growing world, the economy — especially the field of technology and production — are developing very rapidly. Engineering design that would predict the results of this rapid development and equip the society with tools to control them, faces a big challenge. Rapidly developing technology brings many benefits to humanity and makes life easier, friendlier and more comfortable. This has been the case for thousands of years as new branches of engineering were born and came to serve society. One might say that engineers have the privilege of creating a bloodless and peaceful revolution resulting in easier and happier lives for people.

At the same time, such fast developing technology creates traps and dangers, and may cause harm. The inventions of Alfred Nobel, Samuel Colt and Eliphalet Remington, for example, or nuclear research have all brought significant technological progress to nations and societies but have also brought harms and disasters affecting both societies and individuals. The role of engineering design is to predict these harmful actions and plan to neutralize or eliminate them, or even change them from harmful into friendly. Such actions follow the way recommended by BTIPS (Brief Theory of Inventive Problem Solving) procedures [1], especially those using the Prediction module [2], [3]. When developing Prevention Engineering a system approach should be observed and hierarchy of systems established and defined. All systems should be designed in such a way that prevents harm to humans and the natural world.

Recommendations for introducing Prevention Engineering as a branch of engineering practice, and as an educational and research discipline, should be created as soon as possible, and directions for introducing courses in Prevention Engineering design and practice should also be developed [4]. For example, personal protective equipment for individuals and groups as designed by ME and MEM engineering students in their courses might be considered as Prevention Engineering developments [5].

Defining and formulating Prevention Engineering as a new branch of engineering is necessity in our times. In every step of our lives we face the challenge of preventing harms and destruction that can be done by the contemporary surrounding world. The goal of Prevention Engineering [PE] is to make the world safe. Prevention and safety are connected, prevention is an action, while safety is the condition or state that we are trying to achieve. Preventative actions can be based on the recommendations of BTIPS - Brief Theory of Inventing Problem Solving - and may use BTIPS’s approach [4], [5].

The reasons for the development of PE have already been described [6]. Each of these should be pointed out and preventative measures should be found. Adding these preventative measures to the contemporary engineering research, practice and education, and especially reflecting them in the engineering curriculum would be useful now and will also be necessary in the future [7], [8].
Influence of Oil Volume Upon Operation and Performance of Screw Machines With High Built-In Volume Ratio
Authors: Stosic Nikola
Published: January 2020

A performance calculation of a screw compressors with increased built-in volume ratio was performed and presented in this paper to establish how increased built-in volume ratio influences compressor efficiency. It is known that screw compressors have limited built-in volume ratio which is determined by their standard discharge port size and position close to the bores cusp. However, if the discharge port size is reduced beyond its cusp position, the screw machine built-in volume may be increased. In such a case, influence of the oil volume in the air-oil mixture of oil-flooded compressors increases the machine built-in volume further. A performance improvement achieved if the built-in volume ratio is doubled in comparison with the standard port during the machine operation at high pressure ratio of more than 20, is up to 26% in the specific power and adiabatic efficiency. This confirms superiority of the reduced size high pressure port for compressors which operate at high pressure ratio.
Research on Wall Thickness Uniformity of Hollow Axles by Three-Roll Skew Rolling
Authors: Zhang Song , Shu Xuedao , Xu Chang , Wang Jitai , Li Zixuan
Published: January 2020

The paper describes wall thickness non-uniformity of hollow axles by three-roll skew rolling and the proposed improved measure. According to the characteristics of the three-roll skew rolling process, a simulation model of hollow axles by three-roll skew rolling was established. In order to study the influence of different process parameters on wall thickness uniformity, five main process parameters (feed angle, rolling angle, length of forming zone, axial feed speed, temperature) were selected and imported into the simulation model for simulation analysis. The results show that the optimum process parameters are feed angle 7°, rolling angle 30°, length of forming zone 5mm, axial feed speed 20–30 mm/s and temperature 1050°C with the same conditions, and the maximum deviation of the wall thickness is 0.7mm. The uneven wall thickness of the axle body is caused by the metal reflow, which can be solved by compensating for the radial feed of the roller or by secondary machining. Reasonable selection of process parameters can significantly improve wall thickness uniformity of hollow axles by three-roll skew rolling.
Improvement of Axial Tension Distribution of Bolted Joints Tightened by Calibrated Wrench Method From Viewpoint of Quality and Process Control Using Elliptical Confidence Limit
Authors: Hareyama Soichi , Manabe Ken-ichi , Kobayashi Satoshi
Published: January 2020

When tightening a large number of bolted joints, the calibrated wrench method is used. Since this method is indirect, the axial tension varies greatly in many cases. However, the calibrated wrench method is still widely used because of the simplicity of the tool and easy standardization. When the tightening torque and axial tension are considered to be two independent random variables, the axial tension (stress) is distributed within an elliptical confidence limit. Conventionally, it is thought that the shape of this distribution is a rhombus. Considering the permitted limit for a working load (stress) on a bolted joint, the elliptical variation has a larger margin to the yield point than that of a conventional rhombus. On the basis of this feature, we show in this paper that a higher tightening target torque and a higher axial tension can be set than before. By applying the elliptical confidence limit, one can obtain higher tightening torque and initial axial tension than the conventional values within a smaller range of variations. In this study, in the case of tightening a large number of bolted joints at factories and so forth, tightening reliability is considered as a problem associated with quality or process control and a probabilistic statistical method is investigated. Finally, we carry out analysis to establish the optimum tightening torque for bolted joints.
A Study of Corner Separation in a Linear Compressor Cascade Based on SBES Model
Authors: Lu Bingxiao , Teng Jinfang , Zhu Mingmin , Qiang Xiaoqing , Ma Wei
Published: January 2020

Under the condition of large incidence angle in an axial compressor, corner separation will occur in corner region. When the blade loading increases, there may even be corner stall. This three dimensional complex flow structure is high intermittent and unsteady. In order to study the flow mechanisms, a hybrid RANS/LES turbulence model (SBES) was used to simulate the corner separation in the cascade. Firstly, the evolution of vortical structures in the corner separation region were analyzed. The boundary layer and the backflow in the corner separation region encounter, forming vortices with opposite rotation and developing downstream continuously. This cause the unsteady flow in corner separation. In addition, the shedding of detached eddies at the trailing edge is another sources of unsteadiness. Secondly, based on studying the turbulent characteristics, it can be seen that there is active turbulent fluctuation in the corner separation region. The turbulence is high anisotropic because the distribution and the values of Reynolds stresses in different directions are quite different. Thirdly, the mechanism of bimodal phenomenon was explained in this paper. Bimodal means there are two peaks in the velocity probability histogram, it is found in the region between separated flow and non-separated flow. This indicates that there are two non-periodic switching flow modes. Through the analysis of this paper, we find that it is related to the development of large scale coherent vortical structures.
Electromigration Analysis of Power Modules by Electrical-Thermal-Mechanical Coupled Model
Authors: Kato Mitsuaki , Omori Takahiro , Goryu Akihiro , Fumikura Tomoya , Hirohata Kenji
Published: January 2020

Power semiconductors and modules are basic components of electrical infrastructure and are currently widely used in applications such as power conversion devices, industrial equipment, railways, and automobiles. Power modules are being developed with the aim of downsizing and increasing power output. With the larger current densities and higher operating temperatures associated with downsizing and increasing power output, degradation of power modules can occur as a result of electromigration. Electromigration is a phenomenon where atoms move due to the momentum transfer between conducting electrons and metal atoms. In addition, atoms are also moved by mechanical stress gradients and temperature gradients, so it is necessary to take into consideration the combined effects of electrical, thermal, and mechanical stress.

In this report, we describe an electrical-thermal-mechanical coupled analysis of electromigration in a bonding wire of a power module. First, the analysis is validated under the condition that the displacement of the wire surface is fixed. The distributions of vacancy concentrations and hydrostatic stress are almost equal to those in previous studies. Next, we present the influences of current density, temperature, and the displacement constraint on electromigration in a wire with a simplified shape. The analysis results confirm that the plasticity and creep should be taken into consideration in a bonding wire. This also confirm that vacancy concentration increase more rapidly by changing the displacement of the wire surface from the fixed condition to the free condition. Finally, we present analysis results for a bonding wire with the actual shape found in power modules. In this wire, a local concentration peak appear in the electrode terminal. The analysis results reveal that electromigration may affect not only void formation but also other failure phenomena in the bonding wire of power modules.
Analysis of CCR Expansion Joints
Authors: Kaul Sanjay , Gohil Rajpalsinh , Bisharia Parul , Roy Apoorva
Published: January 2020

The CCR (Continuous Catalytic Reforming) Platforming™ process is Honeywell UOP’s technology to convert low octane naphtha to high octane fuel or petrochemical feedstock such as aromatics. It is accomplished in a hydrogen atmosphere at elevated temperature and pressure across a platinum containing catalyst. The process flow is routed through heaters, blowers and coolers between reactors to maintain the heat of reaction. This article captures the procedure of selecting a suitable expansion joint for absorbing thermal movement between two important pieces of CCR equipment — the regeneration cooler and regeneration blower. It shows the design calculations of a universal hinged expansion joint operating at 0.14 MPa and 593°C in a pipe of 762mm diameter. The joint contains 5 single-ply INCOLOY 800H bellows with unreinforced convolutions. Design calculations of the expansion joint have been carried out using formulae prescribed in the Expansion Joints Manufacturers Association (EJMA) standard. Since it is difficult to quantify stresses using a movement test, the EJMA calculations have been verified against finite element analysis results of the bellows.
Structural and Thermal Loads for Hypersonic HEXAFLY-INT Vehicle
Authors: Cristillo D. , Scigliano R. , Di Benedetto S. , Cardone S. , Appolloni M. , Jasko A.
Published: January 2020

The purpose of this paper is to describe the procedures used to evaluate structural and thermal loads experimented by the HEXAFLY-INT Experimental Flight Test Vehicle (EFTV) and Experimental Service Module (ESM) during the ascent phase of the flight trajectory.

The HEXAFLY-INT payload will be launched by a rocket in a suborbital trajectory having an apogee at around 90 km and Mach 8. During this phase the structure is subjected to the launcher environment that includes several events which generates static, random and sinusoidal acceleration and by a fixed thermal distribution. The load conditions due to mechanical loads have been defined by dynamic analyses by means of MSC Nastran software. Thermal loads have been identified by using Ansys Workbench software.

The thermo-structural load conditions due to launcher environment have been defined by means of an interpolation procedure for transferring thermal distribution from Ansys to the Nastran FE Model.
Optimization of Mg Scraps Hydrolysis for Hydrogen Generation Using HCl: Experimental and Simulation
Authors: Akbarzadeh Rokhsareh , Ibrahim Qusai , Adeniran Joshua , Oviroh Peter , Jen Tien-Chien
Published: January 2020

Worldwide concerns on environmental pollution and the need for clean energy supply have attracted researchers’ interest for power generation using technology which not only is a clean technology but also utilizes the Mg scrap waste, a part of solid waste from electronic and automobile industries. The Mg scraps have been used for the hydrogen generation via hydrolysis. In an attempt we conducted the experimental study and optimization of hydrolysis of Mg scraps waste in the presence of HCl to generate hydrogen. This work optimizes the process of using Mg scraps to produce H2, Mg(OH)2 and MgCl2. The effect of different concentration of HCl on hydrolysis was studied to find the optimum concentration for the hydrogen generation. The most influencing parameters such as acid concentration of solution was selected and studied. The kinetic behaviour was analysed to determine the effect of different HCl concentration on hydrogen generation pattern. Numerical modeling was performed considering the chemical reaction using ReaxFF. The effect of the selected parameters on the system and the hydrogen concentration were investigated to predict the performance of the hydrolysis of Mg scraps in the designed reactor. This study proposes an eco-efficient method as it utilizes the Mg waste to produce hydrogen which is an energy carrier.
Introducing Sensor and Signal Processing Technologies With Hands-On Experiments and Software Designing Platform to Students in the Undergraduate Mechanical Engineering Program
Authors: Zhu Na
Published: January 2020

The hands-on ability and problem-solving skills have always been an essential requirement of engineering graduates, while there is an increased demand on the data processing skills recently. To improve such abilities for students, an elective course, sensor technology and signal processing, is introduced to the mechanical engineering undergraduate program. A combination of the lectures and lab activities is completed, where students learn the essential theory and structure of sensors and algorithms in signal processing, such as fast Fourier transform (FFT), windowing, filtering, etc., while applying the knowledge in hands-on activities and design both the simulation and experiment process. Student performance is evaluated in programming assignments, project reports, and exams. Assessment results for problem-solving skills, hands-on activities, and programming skills are presented in the paper.
Experiments on Nonlinear Vibrations of a Nuclear Fuel Rod Supported by Spacer Grids in Air and Submerged in Water
Authors: Amabili Marco , Balasubramanian Prabakaran , Ferrari Giovanni , Franchini Giulio M. , Giovanniello Francesco , Karazis Kostas , Painter Brian
Published: January 2020

For safety reasons, the nuclear fuel assemblies of Pressurized Water Reactors (PWR) must be able to withstand external excitations ranging from large amplitude seismic motions of the reactor to flow-induced vibrations from the surrounding coolant water. A nuclear fuel assembly is composed of long slender tubes, most of them filled with uranium pellets, maintained in a square array by spacer grids. The spacer grids provide a nonlinear flexible boundary condition with friction and micro-impacts that complicates the nonlinear dynamics. In order to improve safety margins in the design of nuclear fuel assemblies, it is of great interest to understand the influence of the spacer grids, as it relates to the overall structural stiffness and damping properties. In particular, the evolution of the vibration amplitude with increasing excitation forces is still undetermined.

In order to understand the nonlinear vibration response of a zirconium fuel rod filled with nuclear fuel pellets and supported by spacer grids, experiments were carried out in water and in air. They consisted of measuring the vibration response of the rod under a step-sine harmonic excitation at different force amplitude levels in the frequency neighborhood of the fundamental mode. If the excitation is large enough, the response of the rod displays nonlinear phenomena such as the shift of the resonant frequencies, multiple solutions with instabilities (jumps) and hysteresis, and one-to-one internal resonances. These experiments were carried out on zirconium tubes filled with axially unconstrained as well as axially blocked metallic pellets, which simulate the nuclear fuel. The zirconium tubes were tested both in air and immersed in water. The experimental data will be processed in the future by means of an identification procedure to extract the nonlinear stiffness and damping parameters of the system. An increase of the equivalent viscous damping with the excitation amplitude level is expected.
Experimental Determination of Layer-Specific Hyperelastic Parameters of Human Descending Thoracic Aortas
Authors: Bozzo Isabella , Amabili Marco , Balasubramanian Prabakaran , Breslavsky Ivan , Ferrari Giovanni
Published: January 2020

Heart disease is the second leading cause of death in Canada resulting in $20.9 billion annual healthcare expenditures [1,2]. Understanding the mechanics of the human descending thoracic aorta is fundamental for comprehending the development of pathologies and improving surgical prostheses. This study presents hyperelastic and viscoelastic material characterizations of the human descending thoracic aorta from twelve different donors, with a mean age of 49.4 years. The specimens were dissected into the three constituent layers: intima, media and adventitia. Evaluating the layer-specific opening angles led to the computation of the circumferential residual stresses. Uniaxial tensile tests of each layer, in both the circumferential and axial direction, were used to model the hyperelastic behavior according to the Gasser-Ogden-Holzapfel model (GOH). The storage modulus and loss tangent for the layers were obtained from uniaxial harmonic excitations at varied frequencies, to model the viscoelastic behavior with the generalized Maxwell model. The results showed a positive correlation between age and stiffness for all layers, both axially and circumferentially. Similar loss tangent values were found across the three layers. A large increase in the storage modulus from static to dynamic experiments further corroborates the importance of a viscoelastic model of the aorta, rather than solely hyperelastic.
Vortex Generator Designs to Improve Flow for a Vehicle Side-View Mirror
Authors: Dong Zulong , Jawad Badih , Liu Liping , Metwally Hossam
Published: January 2020

The unsteady airflow over automotive side-view mirrors is a typical source of turbulence which creates extra drag force, aerodynamic noise and vibration. A CFD analysis is presented for vortex generators (VGs) application on the vehicle side-view mirrors for the purpose of flow improvement. Vortex generators are used to delay flow separation and increase the control surfaces which affect the drag force and down force of the vehicle. Reduced drag force can potentially increase fuel economy, and an increased downforce will increase vehicle grip force and improve vehicle stability which is essential for racing cars. This paper presents practical solutions for mitigating flow turbulence and adjusting down force for existing side-view mirrors.

Four VG configurations were designed and numerically analyzed in combination with the baseline model at air speeds ranged from 15 to 80 miles per hour. This research investigated the effect of each VG configuration on the side-view mirror’s aerodynamic performance. The turbulent flow through the side-view mirror were analyzed by using standard K-epsilon (K-ε) Reynolds-averaged Navier-Stokes method. The drag and down forces results were obtained and compared with the baseline model. The CFD analysis concluded the following: (1) Setting the VGs with a 5 degree attack angle on the upwind face of the mirror slightly reduced the drag force. (2) Setting the VGs at the top of the mirror surface greatly increased the downforce with a large drag force increase.
Quantitative Characterisation of Pearlite Morphology in Hot-Rolled Carbon Steel
Authors: Musonda Vincent , Akinlabi Esther T.
Published: January 2020

During the hot rolling of carbon steel, austenite phase transforms into a pearlitic morphology, which essentially is a matrix of ferrite lamellae (α-Fe) and cementite (Fe3C). This transformation occurs at the cooling bed after an equalisation temperature of around 600 °C. Pearlitic steels find their use in ropes for bridges and elevators, rails, and tyre cords among others. Characterisation of microstructure has not been broadly applied to pearlitic steels because of their complex microstructures. Therefore, the characterisation of this morphology becomes inevitable, in order to identify potential weaknesses in the matrix. In this study, hot-rolled reinforcement bars (rebars) produced from recycled steel and direct reduced iron (DRI), were used for microstructural examination using standard metallurgical procedures. Although the optical microscope (OM) and scanning electron microscope (SEM) were used to obtain qualitative microstructure, they could not characterise the pearlite morphology quantitatively because of their three-dimensional (3D) limitation. Hence, the image analyser - Gwyddion Software, was used to quantify the pearlite morphology of these Y16 rebars. The results indicate that the pearlite colony is characterised by 3D single interpenetrating crystals of ferrite and cementite running parallel to each other due to their common growth during the transformation process of austenite. It was further observed that, the dimensional properties of the phases in the morphology in terms of their width and Interlamellar spacing (S), including the roughness of the pearlite colony can vary significantly. These results could be used to enhance the processing methodology of the industrial production processes.
Investigation of the Effects of Simultaneous Internal Flow Boiling and External Condensation on the Heat Transfer Performance
Authors: Kabir M. M. , Lee Sangsoo
Published: January 2020

Recent leaps in heat dissipation make it difficult for typical heat exchangers to meet the requirements of the advanced applications even with the maximally obtainable heat transfer performance associated with a single-phase process. Especially high heat flux applications such as thermal management in microelectronics, advanced material processing, and nuclear fusion reactors require extreme heat transfer methods to overcome the current limits.

In this study, a heat exchanger adopting simultaneously two-opposite, phase-change heat transfer processes (internal flow boiling and external condensation) was proposed and analytically investigated. The phase-change heat transfer analyses were conducted for internal flow boiling and external condensation at a test section and the heat transfer performances were compared with that of a system with an internal single-phase, liquid flow process. It is found that the proposed heat exchanger configuration with an internal flow boiling can substantially enhance the heat transfer performances and provide better methods to manage the temperature difference comparing to those with an internal single-phase heat transfer due to its significant increase in a heat transfer coefficients and constant temperatures during phase-change processes.

Additionally, this study also explains the design for a test rig to evaluate and validate the results in detail. The test rig consists of an internal flow boiling loop with a test section, an external condensation loop, sensors, auxiliary monitoring parts, and controlling and data acquisition systems. Thermodynamic cycle, pressure drop, and heat transfer analyses were conducted to determine the conditions and the specifications of components and sensors for the test rig.
Macro-Scale Geometric Voids to Alter Stress Wave Propagation in Solids
Authors: Florio C. S.
Published: January 2020

Structural discontinuities, such as voids or inclusions in otherwise uniform, solid materials have previously been successfully implemented to alter the propagation of various types of waves through a range of materials and structures. Much of this work has focused on micro-scale features and low energy waves. The disruption of waves carrying larger amounts of energy currently relies mainly on large material deformation, typically with a layer of the structure becoming permanently damaged in order to protect other portions. However, the ability to disrupt, alter, direct, and control higher energy waves without significant damage to the material or structure can be desirable.

Microscale features can disperse wave fronts, scattering their energy and reducing the potentially damaging effects of the concentrated loads carried in these waves. However, the control of the distribution of these microscale features throughout the material and structure can be difficult, limiting the ability to use these materials to control the dispersion of the wave energy or direct it to more desirable regions in the structure. Macro-scale features can be more easily formed into patterns and arrangements which can be designed for specific wave-controlling or directing properties. Additionally, materials and structures with macro-scale discontinuities can result in a greater change in energy per inclusion and a greater spatial range of their effects throughout the domain of the material. Therefore, they have the potential to be used to address input waves of higher energy. The use of macro-scale features may provide added manufacturing-based benefits, particularly with the more widespread development and use of advanced manufacturing methods, such as additive manufacturing.

This study examines the feasibility of the use of arrays of macro-scale features to direct and control input stress waves. The effect of the shape and arrangement of macro-scale geometric features is studied under a range of orders of magnitudes of the incident stress wave. Methods are developed in this work to predict the propagation of the stress waves through the material and to quantitatively assess the effects of these included arrays of structural, geometric discontinuities. The results of this study are used to evaluate the feasibility of the use of these geometric macro-scale arrays to control the propagation of stress waves in structures while limiting gross material deformation and damage to the overall structure.
Development and Design of the Dynamic Vibration Absorber Using Magneto-Rheological Elastomer for the Weight and Power Consumption Saving
Authors: Terashima Osamu , Nakata Mika , Komatsuzaki Toshihiko
Published: January 2020

In this study, a broadband frequency tunable dynamic absorber was designed and fabricated based on the primary design principle of a mass damper. A magneto-rheological elastomer that can change the relative stiffness when an external magnetic field is applied was used to control the natural frequency of the movable mass of the absorber. A coil to generate the magnetic field was also used as a movable mass to decrease the total weight and to create a constant closed loop of the magnetic force. The hammer impact test results show that the present absorber could change its natural frequency with minimal electric power and had a constant damping ratio. Experimental results of vibration absorbing of an acrylic flat plate show that the proposed absorber could change the natural frequency of the movable mass and reduce the vibration over a wide band by constantly applying the optimum current to the coil in the device with a small power consumption (less than 10 W). Therefore, the proposed absorber works effectively. Further, a technique to determine the electric current applied to the coil automatically based on the phase difference of the vibrational acceleration of the movable mass and the vibrating objective was also presented.
The Design and Analysis of a New Solar-Module Automated Cleaner
Authors: Martin-Garcia Oscar , Huhmann Brianna , Dryden Alec , Duan Shawn
Published: January 2020

In the photovoltaic industry, it is very important that solar modules are kept clean and free of particulates so that the maximum amount of light can get through to the solar cells inside the glass. The development of the new solar-module automated cleaner (S-MAC) is presented in this paper could potentially help keep residential arrays clean and operating at peak efficiency.

The design and analysis of the S-MAC is detailed. The S-MAC went through a series of iterative design, but a final design prevailed. In this final design, a cleaning module is deployed via stackable arms and power screws. The stackability of the arms and power screws allows the reach of the cleaning module to vary accounting for arrays that are asymmetric. The arms will also be translated across the array frame via rack and pinion. Thus, the S-MAC product will be adaptable to arrays of any size and even arrays of varying width. Calculations concerning the stresses on the arms during operation as well as calculations concerning how many supports are required to reduce stress on the glass, have been completed and are included in the following sections.
Self-Vibration Analysis of the Free-Fall Absolute Gravimeter
Authors: Li Zhenxing , Wu Kang , Wen Yi , Yao Jiamin , Guo Meiying , Wang Lijun
Published: January 2020

The ballistic free-fall absolute gravimeters are widely used in acquiring information of gravity field and the self-vibration of the absolute gravimeter is crucial for high precision gravitational measurement. The self-vibration of the T-1 absolute gravimeter has a multi-directional full-band excitation. The resulted horizontal swing has the major impact, since the T-1 absolute gravimeter is simplified as a cantilever beam. A laser vibrometer was applied to directly measure the mechanical self-vibration. The frequency of self-vibration has a nonlinear effect on the measurement error of g, and the peak frequencies should be avoided. The vibration signal was analyzed in time and frequency domain by continuous wavelet transform (CWT). The close frequency profiles were measured in the scalogram and the beat vibrations were observed in time domain as the results of the horizontal swing. The 38 Hz self-vibration had the dominating effect on the measurement error of g for T-1 absolute gravimeter. After optimizing the structure of the tripod, the dominating frequency increased from 38 Hz to 42 Hz. A 11% increase of the vibration frequency can reduce the measurement error of g.
Research on Actuation Properties of Shape Memory Alloy Wire-Based Flow Effector Actuator
Authors: Wu Miao , Wu Lianmei , Yang Fei , Yue Honghao , Yu Hongying , Lu Yifan , Wang Jian , Wang Gang
Published: January 2020

The character of supersonic air-to-air missile is centered with capturing the target or evading the attack of target. Hence, active disturbance control method is proposed by means of using nose-mounted micro-structures what are called flow effectors. In general, flow effector actuator is buried inside the projectile. For satisfying the active disturbance control, the flow effector actuator pushes up from the cone nose of the projectile. For the reason of the air pressure and shape memory alloy wire actuation characteristic, it is necessary to calculate the input stiffness/output stiffness of the transmission mechanism of flow effector actuator.

This paper analyses the system dynamics using the matrix method for serial compliant mechanism. Based on the stiffness characteristics of the corner filleted compliant mechanism, the shape memory alloy wire-based actuator analysis model is built. Besides, the stiffness model and output capacity of the flow effector actuator system are given. The actuation properties of shape memory alloy wire-based flow effector actuator by systematic approach is described, which contains kinematic analysis, static analysis of the system, and using the shape memory alloy strain-stress relationship under high temperature. Several transmission mechanism experiments are performed and the results indicate that the stiffness calculation methods proposed agree well with the experimental results. Flow effector actuator actuation properties test platform is setup and the input displacement and external load is tested.
An Improved Holographic Microwave Breast Imaging Based on Deep Neural Network
Authors: Wang Lulu
Published: January 2020

Microwave imaging offers excellent potential for breast cancer detection. Deep learning is state-of-the-art in biomedical imaging, which has been successfully applied for biomedical image classifications. This paper investigates a deep neural network (DNN) based classification method for identifying breast lesion in holographic microwave image (HMI). A computer model is developed to demonstrate the proposed method under practical consideration. Various experiments are carried out to evaluate the proposed DNN-based HMI for breast lesion classification. Results have shown that the proposed method could serve as a helpful imaging tool for automatically classifying different types of breast tissues.
Eccentricity of Rotor Prediction of Aero-Engine Rotor Based on Image Identification and Machine Learning
Authors: Zhang Zihao , Guo Junkang , Sun Yanhui , Hong Jun
Published: January 2020

The eccentricity of rotor seriously affect the vibration and reliability of aero-engine. Due to the machining error of parts, it is very important to accurately predict the error propagation in assembly. A method based on image recognition and machine learning is proposed to predict the eccentricity of rotor. Firstly, by analyzing and calculating the axial and radial runout error data, the error is mainly concentrated in the first 30 orders of the Fourier series. Secondly, based on the mapping relationship between profile trajectory and eccentricity of rotor, the feature information of the profile trajectory is extracted by constructing the complex domain autoregressive (CAR) model for the radial and axial direction error profile trajectory. Then use the finite element method to calculate the rotor eccentricity. Using the feature information as the input of the neural network, the rotor eccentricity is assembled as the output of the neural network, and the radial basis function (RBF) neural network is built to predict the rotor eccentricity. Theoretical and experimental results show that the proposed method has good enforceability, high accuracy, short calculation time and high engineering application value. In addition, this method can not only be applied to predict the eccentricity of aero-engine rotor flange assembly, but also can be used in the general field of interference fit of assembly.
Lattice Boltzmann Modelling of Contact Angle and Hysteresis Under Homogeneous and Heterogeneous Dynamic Wetting Regime
Authors: Zhumatay Nursultan , Dauyeshova Bagdagul , Adair Desmond , Monaco Ernesto , Rojas-Solorzano Luis
Published: January 2020

The contact angle is a measurement of wettability of a solid surface resulting from molecular attraction or repulsion at the encounter point between a liquid-gas interface and a wall. To date, the determination of the contact angle is commonly performed experimentally with very limited numerical modelling, due to the complex nature of the intermolecular forces at the liquid-gas-solid contact point, even in static conditions. This investigation presents the numerical modelling of the contact angle in static and dynamic conditions on homogeneous and heterogeneous wetting regimes using the multiphase Shan-Chen Lattice Boltzmann Model (SC-LBM). The dynamics of the phenomenon is modelled firstly through a statically suspended droplet and secondly through a sessile droplet subject to the shear flow of air. The Wenzel and Cassie-Baxter states are well reproduced as the response to surface roughness homogeneity. Numerical results demonstrate the excellent suitability of the multiphase SC-LBM for this problem. Furthermore, contact-angle hysteresis is determined under the homogeneous wetting dynamic regime. Two different motion modes were observed during the investigation of the contact angle hysteresis.