bluuebunny/crossref_metadata_2025 huggingface dataset:
Closed Greenhouse Heating in an Arid Egyptian Winter Using Earth-Air Heat Exchangers
Authors: Hegazy Anwar , Subiantoro Alison , Norris Stuart
Published: January 2022

In cold climate regions, closed greenhouses with minimal ventilation minimize the energy requirement for heating compared to open-ventilated greenhouses. In this paper, a model of a closed greenhouse with Earth-Air Heat Exchanger (EAHE) heating is presented and simulations are performed using climate data of a representative day of the coldest month of the year (i.e. January) at the case study location, Hurghada, Egypt. A comparison is made between a closed greenhouse with and without EAHE heating. The simulations show that without heating the greenhouse interior temperature drops below the minimum temperature for cultivation (20°C) during the early and late hours of the day. Furthermore, at midday the temperature inside the greenhouse exceeded the maximum temperature for cultivation (30°C). The results showed that EAHE enabled the greenhouse interior to be maintained at a temperature suitable for plant cultivation, cooling during the day and warming at night. Further, the variability in relative humidity was reduced from 35% to 15%, simplifying the control of the humidity within the greenhouse. Additional simulations that cover the winter period (November to February), demonstrated that the EAHE is a viable sustainable method for temperature regulation without any requirement for additional heating.
Compressible-Gas Coolants in Electromagnetic Heat Exchangers: A Thin Domain Model
Authors: Mohekar Ajit A. , Tilley Burt S. , Yakovlev Vadim V.
Published: January 2022

An electromagnetic (EM) heat exchanger (HX) converting EM energy into heat or mechanical work acts as a receiver end in high power-beaming applications. One potential design of an EM HX consists of a porous ceramic material, which is heated by EM waves, and a compressible gas coolant that delivers energy from the porous media to the outlet. The ceramic materials of interest absorb energy from the EM waves better as temperature increases, that can lead to extremely rapid temperature rises known as thermal runaway. Modeling such an EM HX requires an understanding of the gas dynamics taking place at the pore-scale when coupled with the phenomenon of thermal runaway. To capture the pore-scale gas dynamics, we consider a 2D thin and long structure with a channel carrying a pressure-driven ideal gas flow in perfect thermal contact with a thin ceramic layer. We derive two thin-domain asymptotic models: with and without thermal diffusion along the flow direction, each of which is solved numerically. We find that when local onset of thermal runaway takes place in the ceramic, diffusion along the flow direction at the microscale cannot be ignored. Unlike models of EM HX found in the literature, this work includes thermal expansion done by the gas at the microscale. By looking at temperature profiles at the steady-state, we show that Joule-Thompson cooling of the gas occurs locally when work done by the gas dominates.
Relative Pose Estimation for Cooperative Vehicles and Tracking of Multiple Dynamic Objects
Authors: Ghorai Prasenjit , Eskandarian Azim , Nayak Anshul , Doerzaph Zachary
Published: January 2022

A cooperative perception (CP) between two vehicles to work correctly requires relative positions between two vehicles to be established through a robust and accurate estimation method. This study focuses on relative pose estimation between two vehicles for cooperative perception-based autonomous driving through indirect methods. The indirect method utilizes the positioning data sharing from the Inertial Navigation System (INS) of each vehicle. The relative pose estimation is highly effective in cooperative perception where uncertainties are often involved due to full or partial occlusions caused by dynamic or moving objects such as Vulnerable road users (VRUs) to avoid hazardous situations. The objective is to enhance each autonomous vehicle’s perception capability beyond its own field of view through cooperation with other surrounding vehicles. Hence, in this study, the relative pose estimation between two vehicles in a dynamic situation is presented for cooperative perception-based automated driving system (ADS). The study also presents the detection and tracking results of multiple dynamic objects such as bicyclists, pedestrians, and other vehicles from the scene to avoid accidents or collisions during uncertain or critical situations by sharing their perception information.
Reciprocating Flow for Enhancing Thermal Performance of Latent Thermal Energy Storage Systems
Authors: Singh Virk Akashdeep , Park Chanwoo , Mitsingas Constandinos , Kweon Chol-Bum
Published: January 2022

Efforts related to the enhancement of thermal efficiency of latent thermal energy storage systems (LTESS) are primarily focused on increasing the heat transfer from heat transfer fluid (HTF) at phase change material (PCM) boundaries and increasing the heat conduction inside the PCM. For enhancing heat transfer at PCM boundaries, comparatively less attention has been paid to the thermodynamic characteristics of HTF at the PCM boundary. The current study describes a simple method of increasing heat transfer rate from HTF to PCM in a shell and tube LTESS by increasing the uniformity of temperature at HTF-PCM boundary compared to conventional unidirectional flow methods through the use of a periodically reciprocating HTF flow. This results in the generation of higher temperature gradients across the HTF-PCM boundary which leads to higher heat transfer rates, lower average temperatures, lower maximum temperatures, and lower temperature differences across the PCM. Detailed parametric studies are performed to investigate the effects of flow and heat transfer parameters of HTF, and the design of PCM container on the relative thermal efficiency of the latent thermal energy storage system with reciprocating flow to unidirectional flow.
Irreversibility Analysis, Design, and Optimization of a Combined Hybrid Hot Air and Buoyant Gas Balloon for Stratospheric Persistence
Authors: Trancossi Michele , Jose Pascoa
Published: January 2022

This paper presents the heat and mass transfer model and the design analysis of ALCHEMIST (Atmospheric Laboratory for the study of Circulation at High-altitude, Exchange of Markers and Intercontinental routes between Stratosphere and Troposphere). It is an innovative hybrid balloon project. It is constituted by coupling an external unconventional parachute envelope and a Hydrogen balloon. The dynamic equilibrium conditions with the surrounding atmosphere are considered. The system has been modeled as a limited unsteady irreversible thermodynamic living system. The mission is considered as an evolution of the system in equilibrium with the surrounding environment. Hence, a thermodynamic model based on irreversible thermodynamics is presented. The results according to both first and second law are produced and compared to actual flight data. The primary physical processes responsible for balloon performance aloft are accurately modeled in the proposed optimization process. The results demonstrate that the system could be optimized up to a stratospheric altitude around 30 km and shows that second law optimization produces an effective performance improvement.
Design of a Lightweight Robotic Mule
Authors: Su Jian , Zhi Xin , Lu Sha , Zhang Qichun , Dong Janet
Published: January 2022

Off road terrain poses a continual challenge to military movement. To meet this challenge, a robotic mule is designed to be a personal mobility device that can carry a soldier or that a soldier can carry. This paper will discuss the design process of such novel robotic mule, including overall structure, cargo/soldier platform, driving system, power system, and stress analysis and simulation. This robotic mule provides a new approach for army soldiers or soldiers’ equipment to move across field effortlessly and efficiently. The movement of the robot can be guided by GPS system or follow a soldier who carries emitter with sensor. The robot is designed to operate in nature terrain, which is standard nature trail in a boreal forest and may have a few roots and rocks but free from climbing obstacles.

The robotic mechanism is suitable for one-man lift, with weight not to exceed 20 kg. The robot is capable of moving through a standard door width 80 cm while fully loaded. The system can support 100 kg payload. It also provides soldier following capability and be able to perform with or without the operator on board. The system controls balance of the vehicle, while avoiding obstacles, and negotiating narrow urban or off-road terrain. The speed on flat terrain is 5–7 m/s with a range of 30 km.

The robot mule consists of a robust chassis platform, a driving system, a power system, a chair system for soldier, and GPS and vision system for autonomous control. For chassis platform, its structure is designed to be both light and sturdy. Stress analysis of the structure is applied to verify the safety of carrying objective payload. The width of the chassis platform is designed to access standard handicap door. For driving system, considering both terrain and weight limits, a four-wheel driving system is designed to overcome nature terrain which may have a few roots and rocks. Next, based on calculation of traction need and travel range, motor and lithium battery kit are selected to maintain target speed on flat terrain with target mileage. Power for extra functional features needed, such as sensors for navigation and surrounding detection etc. is also considered in calculation of battery capacity. Cargo/soldier platform is designed to provide proper space for carrying the soldier and/or equipment. Security fixtures are designed and added to the cargo/soldier platform which avoid swaying and falling of equipment. Also, ergonomics research is conducted to make a comfortable and hazards free platform for soldiers. Moreover, two handles are designed and will be mounted on each side of the robot mule, which makes the robot be lifted easily by a soldier and helps guard cargo payload in place.
Robotic System for Plant Tending in Remote Habitat
Authors: Hament Blake , Oh Paul , Carr Danielle , Moore Carl , Dev Satyanarayan , Ferguson Ian , Pena Pedro , Ehrlich Josh W.
Published: January 2022

The integration of robotics with agriculture in a controlled or closed environment is attractive because it enables remote production of food and oxygen without siphoning valuable hours of astronaut labor. Similar techniques can also be applied to terrestrial habitats to improve food security in areas that may not be well-suited to outdoor and/or labor-intensive traditional agricultural practices. In this paper, a robotic system for plant tending is presented with reflections on results of early demonstrations. The system includes remote teleoperation capabilities, a 6-DOF robotic arm, vision system for 3D reconstruction of plants, pneumatic multi-tool changer, and custom end-effectors including an enclosure latch tool and a plant shear tool. This work is a collaborative effort between NASA Kennedy Space Center, Lockheed Martin Space, and university partners to test the technologies of autonomous plant growth systems in deep space.
Numerical Investigation and Validation of Jet Temperature Effects on Nozzle-Afterbody Drag
Authors: Haznedaroglu Berke , Ciftci Omer , Cadirci Sertac , Aytac Serhad
Published: January 2022

In this study, jet temperature effects on afterbody drag in subsonic, transonic and supersonic flow conditions have been investigated for a wide range of nozzle throat total pressure to free-stream static pressure ratio (NPR) at Mach numbers 0.6, 0.9 and 1.2 using CFD. Preliminary CFD simulations are conducted for cold air flow with constant specific heat. Experimental data available in NASA Technical Paper 1766 is utilized for validation purposes thus, the CFD simulations are carried out for the identical geometry and boundary conditions reported in the technical paper. Depending on the Mach number, either pressure-based solver with coupled algebraic multigrid scheme or implicit density-based flow solver with Roe-FDS are used for the simulation of compressible flows to maintain convergence and obtain accurate solutions. Second order upwind schemes are preferred for all simulations and it is shown that convergence problems could be prevented when density based solvers are used at relatively high Mach numbers. For all simulations SST k-ω turbulence model proposed by Menter is selected. Based on a robust and verified CFD approach for cold jet analysis, the average drag coefficients Cd at various NPR values between 1.5 and 7 have been successfully estimated at all Ma with relative errors ranging from 5 to 15 % compared to experimental data. Then, the same numerical approach is adopted to the hot jet analysis. Further comparisons to empirical relations revealed a satisfactory agreement only at Ma = 1.2, but no acceptable match at Ma = 0.6 and 0.9.
Damage Assessment Method of Battery Pack of Electric Vehicle in Undercarriage Collision
Authors: Chen Powen , Xia Yong , Zhou Qing , Qu Yunlong , Wei Xinqi
Published: January 2022

Undercarriage impact occurs when vehicle’s ground clearance is incompatible with obstacle on the road. This kind of accidents are particularly dangerous to electric vehicles as battery pack is usually integrated into the vehicle floor. In case of an undercarriage collision, the battery pack could be ploughed through by the obstacle on the road, which could cause damage to battery cells in the pack and occurrence of internal short circuit and thermal runaway. To tackle this new problem, damage assessment method is needed to guide design of protective structure of battery pack. The present paper documents an analysis of battery damages in undercarriage collisions and development of a test method for evaluating undercarriage collisions. We first used a simplified finite element model of battery pack and conducted computer simulations to understand the influences of key parameters. The battery pack model included blade battery cells that had no module-level assemblies. Based on the learning from the finite element analysis, we then developed a generic test method for evaluating undercarriage collisions. The test method is robust in terms of repeatability and the device is adaptable for evaluating a wide range of electric vehicle undercarriage collision. We hope that this test method can become a unified and standard method for evaluating battery pack damage in undercarriage collisions and guide design of protection structures for enhancing safety performance of battery packs.
Prediction of Shock Wave Position Considering Non-Equilibrium Phase Change of Wet Natural Gas in Nozzle
Authors: Liu Yang , Cao Xuewen , Bian Jiang
Published: January 2022

The existence of back pressure will cause shock wave in the Laval nozzle of the supersonic separator, which will lead to the condensed droplets to evaporate and reduce the separation efficiency of the separator. It is of great significance to determine the shock position and avoid the secondary evaporation of droplets for improving the separation efficiency. In this paper, one-dimensional isentropic flow function method was used to calculate the shock position in nozzle. A mathematical model of methane-water vapor was established. The results show that the pressure energy recovery leads to the shock wave. With the increase of energy recovery efficiency, the position of shock wave moves to the throat, which shortens the droplet growth space and reduces the liquefaction of Laval nozzle. When the pressure energy recovery efficiency is 56.25%, the liquid mass fraction is 1.63% at the outlet. The shock wave position error of theoretical calculation and numerical simulation increases with the enlargement of divergent angle when considering condensation. The average error between numerical simulation and theoretical calculation results was less than 5%, thus the one-dimensional isentropic flow function method can provide a theoretical basis for predicting the shock position.
Residual Formability of Single Point Incrementally Formed Part
Authors: Nikhare Chetan P.
Published: January 2022

Single point incremental forming is a potential manufacturing process under sheet metal forming which promises various advantages over other manufacturing processes. Single point incremental forming is a die-less manufacturing process. In this process the sheet metal is clamped in the fixture and then a single point, incrementally form each point by sliding the material forward and downward. As at each point the single point is formed, the uniform deformation can be achieved in the whole part and due to which the part can show much higher formability as compared to the conventional forming. The process has these other advantages over conventional forming like complex shapes can be created, and higher flexibility in the process as it depends on the forming program. Enormous research on the subject are available in the literature on formability, process variation, process parameters and their influence, but limited research are available on residual formability on single point incrementally formed parts. The previously published paper in IMECE2019 by the author studied the residual formability of single point incrementally formed part with four cone angles. It was found that the 30 and 45° cone angle did not survive during single point incremental forming but 60 and 90° did. Further 60 and 90° cones were conventionally restrike with spherical dome punch to determine the residual formability, however the 60° cone failed without conforming the dome shape, but 90° deformed to full shape of dome and then fractured. In this paper the aim is to construct the whole section of forming limit point from uniaxial to equal-biaxial deformation mode restrike and measure the forming limits. These points will construct the whole residual forming limit curve of a single point incrementally formed part. For this, the successfully formed part by incremental forming were restrike with hemispherical tool in tensile, plane and biaxial deformation mode and limits were plotted. It was found that the maximum deformation is due to the single point incremental forming and less deformation are left in the part if it would be restrike by the conventional forming method.
Overlap Ratio as the Design Variable for Maximizing the Efficiency of a Savonius Wind Rotor: An Optimization Approach
Authors: Mohan Man , Saha Ujjwal K.
Published: January 2022

The application of Savonius wind rotor is increasing worldwide to provide electricity without contributing to global warming and promoting the small-scale power production. However, its lower performance remains a major problem due to high unproductive torque produced by the returning blade. In this paper, an optimum blade profile is obtained by maximizing the power coefficient (CP) considering the overlap ratio (OR) as an optimization parameter. This is done by coupling computational fluid dynamics (CFD) simulation to the rotor blade profile developed through the simplex search method. The blade profile is symmetric about the x-axis, where half of the blade geometry is formed by a natural cubic spline curve using three points. Two end points are retained fixed, while x and y of the third point is taken as a variable in addition to OR in the simplex search process throughout its iteration using the MATLAB platform. In all the iterations, the blade profile is meshed by using ANSYS ICEM CFD platform. The rotor performance analysis is carried out by ANSYS Fluent using the shear-stress transport (SST) k-ω turbulence model. The finite volume method (FVM) is used as a solver setup to solve the transient 2D flow around the rotor blade. The optimum blade profile is compared to a conventional semicircular blade profile over a wide range of tip speed ratio (TSR). The present study demonstrates the superior performance of the optimum blade profile showing CPmax that is 23% higher than the conventional semicircular blade profile at TSR = 0.8. Further, at OR = 0.154, the CP is found to be maximum. The velocity magnitude contours, total pressure and turbulence intensity contours are generated to analyse the effect of the optimal design approach.
Process Parameter Optimization in Machining of γ-TiAl With Hexagonal Inserts
Authors: Peng Ching-Tun , Shareef Iqbal
Published: January 2022

γ-TiAl, gamma titanium aluminide, is a unique metal matrix composite, the structure of which provides exceptional properties that include low density, high yield strength, high stiffness, high specific stiffness, etc. Consequently, γ-TiAl alloys are long being considered for substituting several superalloys for various applications in the fields of automotive, aerospace and biomedical industries. However, γ-TiAl is well-known as very difficult to machine, which has hindered the widespread application of γ-TiAl. In this paper, a central composite design (CCD) of experiments is adopted to investigate various turning process responses with hexagonal shape inserts. Results show that, among three turning factors, the depth of cut factor has the greatest impact on cutting force responses, while the feed rate factor has the most dominating effect on specific cutting energy and surface finish. Quadratic equations are developed, and the corresponding two-dimensional and three-dimensional plots are established. By means of regression analysis and response surface methodology (RSM), a series of optimal turning parameters is obtained, which renders the minimum machining energy, leading to increased tool life and improved machinability. Furthermore, it is feasible to achieve an industry-accepted surface finish. The results of this work cover a machinability investigation of a gamma titanium aluminide that can find application in automobile and aerospace industries for machining of high-temperature resistance parts.
On the Maximization of the Waste Heat Recovery From Exhaust Gases of Internal Combustion Engines
Authors: Di Battista Davide , Carapellucci Roberto
Published: January 2022

In this work, two different options of waste heat recovery from internal combustion engines have been proposed and compared to each other. Both consider two thermodynamic cycles in order to maximize the energy recoverable. The first considers a Brayton-Joule cycle as top cycle, which is immediately interfaced with the exhaust gases and has a supercritical CO2 as working fluid; while an ORC is bottomed to this, using R1233zdE as the organic working fluid. In this way, the supercritical CO2 can have better efficiency and the bottomed ORC can further recover the low temperature energy discharged by the Brayton-Joule cycle.

The second option considers an Inverted Brayton Cycle as top thermodynamic cycle, which uses the same exhaust gases as working fluid and, so, has a lower complexity. The thermal power discharged at low temperature by the inverted Brayton Cycle is further recovered by the ORC bottom unit.

The two options will be studied using a mathematical model developed and tailored to a 3L turbocharged diesel engine, whose experimental data are available measuring the most relevant quantities (exhaust temperature and pressure, fuel consumption, brake efficiency, etc.) in typical operating points of a heavy duty vehicle. A comparison of the two combined systems assesses the most effective recovery option.
Crystalline Phase Changes Due to High-Speed Projectiles Impact on HY100 Steel
Authors: Slewa Muna
Published: January 2022

High yield HY-100 steel is a unique alloy and well known for its employment in heavy construction. HY-100 offers good characteristics like ductility, notch toughness, corrosion resistance, and weldability. The physical characteristics and molecular structure of HY-100 steel are also well known; however, there is little known about the effect of high-velocity projectiles impact on this metal alloy’s crystalline structure and material phase. The effects of high-speed velocity impact on the crystalline structure and material phase changes are studied herein experimentally. The results of an impact on the crystalline structure are assessed by impacting HY-100 steel plates (15.4 × 15.4 × 1.27 cm) with Lexan projectiles. A two-stage light gas gun accelerates these projectiles to a velocity of 6.70 km/s at the point of the impact. The impacted plates’ surfaces are prepared as required for inspection by the Electron Back Scatter Diffraction (EBSD) microscope. Ten regions on each impacted plate area are examined and analyzed after impact. These regions are selected from the area immediately under the impact crater to locations that are not physically affected by the impact. Observations of collected EBSD images show that the predominant phase is Body-Centered Cubic (BCC). Moreover, Face-Centered Cubic (FCC) and Hexagonal-Close-Packed (HCP) phases are also indexed. The samples are also post-impact examined for molecular structure allocation changes. The results were then tabulated according to the regions relative to the impact crater. In this study, traces of HCP were found at some locations in all post-impact stages. This study also indicates that the BCC crystalline structure remained the dominant phase structure after impact, and it is valid with all test samples and all levels of shock loading. At this velocity, the damage zone develops within 5 microseconds due to impacting momentum. HY-100 steel materials go through a reversible phase change when subject to elevated temperature and high quasi-static pressure.
Numerical Simulation of Turbulent Pipe Flow With 90-Degree Elbow Using Wall y+ Approach
Authors: Abuhatira Ahmed A. , Salim Salim M. , Vorstius Jan B.
Published: January 2022

This study presents the use of the wall y+ approach as a form of guidance for reliable selection of mesh and turbulence models in bent pipe flow investigations. The research builds on previous studies recommended by Salim et al.[1]–[3] for using the wall y+ approach to balance between the computational cost and time. This method is proposed as an effective tool for selecting an appropriate near wall treatment and corresponding turbulence model and remove the necessity of physical validation when experimental data is unavailable or difficult to obtain. Flow in a 90-degree pipe elbow is modelled using the ANSYS FLUENT CFD solver to evaluate the performance of different Reynolds-Averaged Navier-Stokes (RANS) turbulence models. The RANS models tested are the standard k-ε, the Reynolds Stress Model (RSM), the k–ω Shear Stress Transport (SST) and the Spalart–Allmaras. A range of near wall spatial resolutions is used to determine the effectiveness of near wall modelling techniques when used in conjunction with each of the turbulence models. The near-wall treatments are investigated by solving the y+ values for the first layer of cells are in the viscous sublayer (y+ ≈ 3), buffer region (y+ ≈ 19) and log law region (y+ ≈ 39). The achieved results in this current study using the wall y+ approach are compared against experimental data published by Sudo et al.[4] and numerical simulations published by Kim et al.[5]. Qualitative analysis and quantitative assessment are carried out to identify which turbulence model agrees best with the published data. It is observed that the near wall models provide better results when the y+ values for the first layer of near wall cells are within viscous sublayer in comparison to simulations where it is in the buffer and log-low regions. The RSM predicts the flow field most accurately when compared against the reference data. This in turn will allow pipeline designers to assess the effectiveness of their design, and any potential problems with it, before the manufacturing stage.
Intelligent Defect Diagnosis of Spiral Bevel Gears Under Different Operating Conditions Using ANN and KNN Classifiers
Authors: Tayyab Syed Muhammad , Pennacchi Paolo , Chatterton Steven , Asghar Eram
Published: January 2022

Spiral bevel gears are important part of many mechanical transmission systems and are known for their smooth operation and strong load carrying capacity. This type of gear has a high contact ratio, which makes it very difficult to diagnose even serious defects. Therefore, spiral bevel gears have rarely been used as a reference for defect diagnosis techniques. To overcome these challenges, artificial intelligence (AI) techniques are used in this research to diagnose defects in spiral bevel gears. Although Al techniques in the field of fault diagnosis have been very successful, however, these methods largely use the assumption that the training and test data come from the same operating conditions. However, when the operating conditions in which the trained model is deployed for predictions, differ from the operating conditions in which the model was trained, the performance of these approaches might be significantly reduced. Outside the laboratory, in real-world applications, operating conditions significantly vary, and it is difficult to obtain data for all potential operating conditions. To overcome this limitation and to make AI techniques suitable for diagnosing spiral bevel gear faults under different operating conditions, an effort is made to find fault distinguishing features, which are lesser sensitive to operating conditions. Artificial neural network (ANN) and K-nearest neighbors (KNN) are used as classifiers for fault detection. Performance comparison between both classifiers is made to determine their individual capability and suitability for diagnosing defects of spiral bevel gears under different operating conditions.
A Fluids Experiment for Remote Learners to Test the Unsteady Bernoulli Equation Using a Burette
Authors: Traum Matthew J. , Mendoza Zambrano Luis Enrique
Published: January 2022

The COVID-19 pandemic illuminated the critical need for flexible mechanical engineering laboratories simultaneously deployable in multiple modalities: face-to-face, hybrid, and remote. A key element in the lesson portfolio of a forward-looking engineering instructor is economical, hands-on, accessible, “turn-key” lab activities; kits that can be deployed both in brick-and-mortar teaching labs and mailed home to remote learners. The Energy Engineering Laboratory Module (EELM™) pedagogy, described elsewhere, provides an underpinning theoretical framework and examples to achieve these features. In addition, instructional lab kits must demonstrate foundational engineering phenomena while maintaining measurement accuracy and fidelity at reasonable cost. In the energy-thermal-fluid sciences, achieving these conditions presents challenges as kits require energy and matter transport and conversion in real time at scales large enough to reveal measurable phenomena but not so large as to become hazardous to users. This paper presents theoretical underpinning and experimental verification of a fluid mechanics lab experiment appropriate for undergraduate engineering students that 1) meets all the above-described criteria, 2) costs less than $30 in materials, and 3) can be easily mailed to remote learners.
Horizontal Axis Wind Rotors With Twisted Blades
Authors: McGuire Joseph , Zhou Hong
Published: January 2022

Horizontal axis wind turbines are now prevalent across the world for wind energy harvesting. Electric power is produced by the electric generator of a wind turbine that catches wind power through its wind rotor that is mainly driven by the lift force on its rotor blade. Airfoil characteristics such as airfoil shape, cord length, camber and airfoil twist are utilized to generate lift force that is perpendicular to the rotor axis. Although horizontal axis wind turbines have been widely used on wind farms, there is still room to further improve their efficiency and power generation. In this research, the power conversion efficiency or coefficient of a wind rotor is improved from airfoil twist. The airfoil twist angles of a rotor blade are selected based on maximizing the ratio between lift and drag forces. Three blade twist configurations are introduced for three different tip speed ratios. Four blades that have the three optimal and one reference twist configurations and their corresponding rotors are modeled and simulated. The simulation results show that the power conversion coefficients of the rotors with the optimal twist configurations have significant improvements on power conversion efficiency over that of the reference rotor.
Novel Nanocomposite Refractive Index Tuning Mechanism Based on Controlling Embedded Particle Morphology
Authors: Liu Sipan , Islam Md Didarul , Ku Zahyun , Urbas Augustine M. , Derov John , Boyd Darryl A. , Kim Woohong , Sanghera Jasbinder S. , Ryu Jong E.
Published: January 2022

This study investigates the embedded nanoparticles’ morphology and distribution effects on the effective refractive index (RI) of composite. The study is based on the FEA model for the Fabry-Pérot interference cavity made from the nanocomposite film. The composites’ effective RI can be derived from the simulation reflection spectrum. In constant particle volume fraction condition, the embedded particles with a larger diameter, locating at the region with high electric field and having longer side length along the electric field oscillating direction, are identified as the factors to reinforce the effective RI. For 4 μm incident light-wave, as controlling the diameter from 24.8 nm to 212 nm, distribution from middle-gathered (high electric field region) to top-bottom gathered (low electric field region), and the rectangular cylinder particle shortest side along electric field oscillating direction to longest side along electric field oscillating direction, the effective RI increasing from 1.687 to 1.719, 1.638 to 1.745 and 1.66 to 1.901, respectively. The underlying RI shifting principle is recognized from the light scattering loss by embedded nanoparticles. This discovering provides one novel idea for next-generation real-time RI tuning structure and device.
On the Dynamic Response of a Dielectric Elastomer Membrane
Authors: Sarker Pratik , Chakravarty Uttam K.
Published: January 2022

The dielectric elastomer material is a category of electroactive polymers which produces large deformation under applied voltage. This property made them much promising as smart materials that can rapidly adapt to changes in environmental conditions due to their mechanical response to an electrical input. In this study, a specimen of a hyperplastic elliptic DE membrane is considered to observe the structural dynamics and aerodynamic characteristics under external flow of air subjected to electric excitation. For the structural dynamic characteristics, a finite element model of the membrane subjected to three different electric voltages is created. The frequencies obtained from the finite element model are compared to that of the analytical method. For the aerodynamic response, a fluid-structure interaction model is created under steady airflow with low Reynolds number characteristics. The variations of the aerodynamic coefficients of lift and drag with the angle of attack are studied for a particular fluid velocity. In addition, the out-of-plane deformation of the membrane with different angles of attack subjected to different voltages are also investigated. It is found that the vibration frequency decreases as the voltage increases due to the softening effect of the voltage on the membrane. The aerodynamic coefficient of lift is observed to increase with the angle of attack up to the critical value which is a trend similarly followed by the aerodynamic efficiency.
Ductile-to-Brittle Fracture Size Effect of Titanium Sheets in Micro/Meso-Scale Plastic Deformation
Authors: Sun Lei , Xu Zhutian , Peng Linfa , Lai Xinmin
Published: January 2022

With a significantly increasing demand for miniaturized titanium thin-walled products, micro forming using sheet metals is a promising approach with high productivity. However, once the sheet thickness is scaled down to a micro-scale, there are many unknowns in terms of size effect and its affected fracture behavior. In this research, the influence of grain size on the fracture behavior of commercially pure titanium sheets with a thickness of 0.1 mm was investigated by the uniaxial tensile tests combined with a digital image correlation measurement system. The ductile-to-brittle transformation of fracture behavior with the grain size increasing from 33.07 to 107.70 μm was revealed. Macroscopically, the elongation and critical fracture stress of CP-Ti samples decrease with the increase of grain size. According to the scanning electron microscopic observations, the number of dimples decreases with grain size increasing, while the cleavage planes and river patterns gradually dominate in the coarse grain fracture surface. To explore the fracture mechanism, the dislocation evolution of various grain sizes is further observed by a transmission electron microscope. The dislocation emission from crack-tips was revealed at different grain sizes. Significant dislocation pile-up at grain boundaries was observed in the specimen with a grain size of 33.07 μm. Those intense dislocations reduce the effective stress at the crack tip resulting in higher crack propagation resistance. Nevertheless, the dislocation density at crack-tip decreases strongly with the increase of grain size leading to high crack-tip effective stress and less crack plasticity. Hence cleavage fracture was dominated in coarse grain CP-Ti sheets.
Error Analysis of Models for the Forces on a Cylinder Undergoing 2-DOF Prescribed Motion in a Stream
Authors: Aktosun Erdem , Xiros Nikolaos I. , Dahl Jason M.
Published: January 2022

Based on experimental data, a data error estimation model is developed for an existing neural network time dependent hydrodynamic force model. The force model, based on forces measured in forced motion experiments, is used to approximate the time dependent forces on a cylinder that may undergo combined in-line and cross-flow vortex-induced vibrations. This model will be used to develop future control models to improve VIV-based energy harvesting systems. Previously, a dynamic model of appropriate complexity was created in order to approximate time dependent lift and drag forces based on force time histories measured in an expansive set of forced motion experiments. Position and velocity were used as input to the dynamic model. A feed forward neural network was trained using the force database in order to develop time dependent models of forces on the cylinder for prescribed sinusoidal motion. The time series error between the measured and feed forward Artificial Neural Network (ANN) model was found for the lift and drag force time histories. In the present study, an autoregressive error predictor is developed from the existing neural network time dependent model of forces on the cylinder for given kinematic conditions. This autoregressive (AR) error predictor is developed based on the error between the measured signal and artificial neural network model and can be used to improve predictions from the model.
Residential Appliance Usage Patterns From Overall Energy Consumption Data: A Statistical Machine Learning Approach
Authors: Bandyopadhyay Arkasama , Bhattacharya Anirban
Published: January 2022

Large energy-intensive domestic appliances like heating, ventilation, and air-conditioning systems, electric water heaters, refrigerators, clothes washers, dishwashers, and dryers can together comprise about 58% of annual residential electricity consumption in the US. Accurate knowledge of domestic appliance-level energy usage patterns can help energy modelers and electric utilities design optimal demand response programs in residential communities. However, while the widespread installation of residential smart meters in the US over the past decade has enabled electric utilities to collect diurnal individual household-level electricity consumption profiles, it is extremely rare to find location-specific, short-interval, disaggregated appliance-level data for individual residences. This study develops a novel methodology to reliably predict future domestic appliance energy consumption profiles based primarily on overall electricity consumption and local weather data. The model is demonstrated using fifteen-minute interval appliance-level empirical energy consumption data for a test-bed of 25 single-family detached homes in Austin, TX from Pecan Street Inc. — a non-profit entity based in Austin. Although the training of our model utilizes historical appliance profiles, the results obtained from this analysis can be used to reliably and accurately predict time-granular appliance-level energy consumption patterns (not only on/off times) using only the overall electricity consumption profile of the household. Thus, this study opens up the possibility for energy modelers to reliably forecast domestic appliance electricity consumption profiles without having appliance-level historical energy usage datasets available.
Equivalent Energy Absorption (EEA) - A Methodology for Improved Automotive Crash & Safety Design
Authors: Narayana Peddi Sai Rama , Prakash Raghu V. , Gunti Srinivas , Raghu Kanugula
Published: January 2022

Safety norms across the world are becoming more and more stringent posing new challenges to achieve lightweight vehicle structures. Structures made of Advanced/Ultra high strength steels (AHSS) play a vital role in meeting the vehicle safety targets, by absorbing large amounts of impact energy, as well as by withstanding higher impact loads that occur due to vehicle collisions.

Safety simulations usually take longer solution times due to their complexity and nonlinear nature. Engineers often encounter with a problem of quick evaluation of safety performance by using different grades of materials to optimize the weight & cost. In this paper, a new methodology - Equivalent Energy Absorption (EEA) has been proposed to do a quick trade-off study on performance vs weight for various thickness and material combinations. A relationship is established between the gauge and grade of a component to derive an equivalent safety performance so that engineers can make quick decisions by conducting minimal number of simulations. a simple rectangular crush box was considered for study to assess the Energy Absorption (EA) with various material and thickness combinations. A Design of Experiments (DOE) study was done using simulations with many numbers of material grades and gauges to construct a 3D Response Surface between gauge, grade & EA parameters to understand the relationship between each of these parameters.

A case study has been discussed in the paper about application of this methodology on a vehicle to evaluate its safety performance. It has been found that more than 80% evaluation time is reduced by using this methodology.
Towards Development of 3D Printed Swimming Robot Using Soft Electromagnetic Actuation
Authors: Garcia Martin , Rouse Ciaphus , Estrada Benjamin , Tekes Coskun , Moghadam Amir Ali Amiri , Tekes Ayse
Published: January 2022

Success of emerging field of soft robotics relies on the development of efficient soft actuators. Most of these actuators suffers from disadvantages such as limited blocking force, lifetime, high actuation voltage, and slow response time. Swimming robots in particular utilizes single or multiple soft actuators to mimic the dynamic of a fish during motion. In this study we used 3D printing to fabricate soft electromagnetic actuators based swimming robot. The mechanism consists of soft actuator legs, compliant paddle and floatation. We designed a hybrid propulsion mechanism by using double soft leg actuators as caudal fins and side paddles as pectoral fins. This increases the thrust and efficiency to overcome the water drag as well as providing stability. We 3D printed the soft actuator using thermoplastic polyurethane (TPU) filament to reduce the manufacturing cost as well as to simplify the process. The main body is also 3D printed using polylactic acid (PLA). The infill percentage of the soft body is adjusted to increase the bending performance without yielding under actuation. The prototype of the swimming robot was tested in water. The body velocity of the robot is measured as 0.106 BL/s. Motion analysis was made MSC Adams by simulating the deformation of flexible beams.
A Numerical Study on Springback of a Channel Through the Oscillation of Punch
Authors: Nikhare Chetan P. , Buddi Tanya , Kotkunde Nitin , Singh Swadesh Kumar
Published: January 2022

To meet the demand of light weighting, environmental regulation, increase fuel economy, many innovations are underway. Options are light weighting the part to reduce the fuel consumption or decrease the gage in high strength dense material. In both cases during or after deforming the part these challenges occur like higher tonnage machine for deformation, sudden fracture, geometric defect, etc. One of the geometric defects which is very common in sheet metal forming is springback. Springback is the deviation of the part from the desired shape after the part is shaped and then load is released. It is the material tendency to relaxed back based on the accumulated strain and its elasticity. In lighter material or higher strength steels, the springback phenomena is very common due to lower elasticity or higher strength value. In this paper springback is analyzed by conceptualizing an innovative process. The innovative process is oscillation of the punch after the forming process is done. The 2D channel strip of the aluminum 2024 high strength alloy was used in the bending process. The process of bending with punch die and the blank was modeled in the ABAQUS finite element software. First, the conventional channel deformation was performed, and the deformation was studied and springback was compared with the desired shape. Then the oscillation of the punch was set either in the longitudinal or lateral direction. The frequency of the punch was also been changed to see the effect on the deformation behavior of the material and springback after the punch release. The residual stress during the process was studied and compared. Further the maximum stress, deformation of the channel and springback was analyzed and presented. It was found that the punch oscillation contributes in reducing the springback.
A Novel Mean Stress-Independent Fatigue Model for Bonded Joints With Ductile Adhesives
Authors: Gerini-Romagnoli Marco , Nassar Sayed A.
Published: January 2022

A mean stress-independent lap shear fatigue model is proposed for Aluminum 2024 alloy Single Lap Joints (SLJ) that are bonded with ductile, polyurethane-based, adhesive. Fatigue data is generated in the High Cycle Fatigue range, for 4 values of mean stress and multiple levels of alternating load. Individual S-N curves are constructed, for each value of mean stress, and the results are statistically analyzed. A separate logarithmic regression of the entire pool of data is performed, considering maximum stress and fatigue life of the samples. The test data align along the same regression line. As a result, the amount of tests to perform for durability characterization of single lap joints bonded with ductile adhesive can potentially be reduced.

High sampling frequency information of the displacement of the specimens during fatigue tests is periodically acquired and filtered. The creep-like curve describing the evolution of the mean displacement during the fatigue tests suggests that cold flow phenomena could trigger fatigue failure, rather than the propagation of a crack.