bluuebunny/crossref_metadata_2025 huggingface dataset:
Profile Loss of a Printed Transonic Turbine Cascade
Authors: Hake Leander , aus der Wiesche Stefan
Published: January 2022

Profile losses of turbine blades are one of the main problems in turbine technology. Besides the occurring aerodynamic effects, it is well known that the surface roughness has a significant influence on these losses. It is generally known that a better surface quality leads to lower profile losses. Many studies for this topic are given in open-source literature, but the investigations were mainly performed in an ideal gas atmosphere (air). The present contribution presents the results of an experimental study of profile losses of an additive manufactured linear turbine cascade placed in the test section of a closed-loop organic vapor wind tunnel, or CLOWT for short. The investigations are carried out under an organic superheated steam atmosphere. For this organic vapor atmosphere, the of carbon based liquid Novec™ 649 has been used. In addition, measurements were also realized in an air atmosphere. To get different point of views, three different approaches are chosen to determine the profile losses.
Improved Tensile Strength and Electrical Conductivity of the Electrical Conductor Aluminum Alloy 6201
Authors: Allamki Alyaqadhan , Al-Maharbi Majid , Arunachalam Ramanathan , Zahid Qamar Sayyad
Published: January 2022

The aluminum-magnesium-silicon alloy 6201-T81 is a popular electrical conductor, widely used for overhead and distribution lines. Its light weight makes its mass conductivity twice that of copper. Aluminum conductors however experience creep, corrosion, power loss, and other drawbacks. Therefore, it has become a necessity for manufacturers to improve mechanical and electrical properties. The alloy 6201-T81 is an age hardenable alloy, in which a controlled precipitation of Mg2Si is performed through two different successive heat treatments: Solution heat treatment and precipitation heat treatment. ∅ 3.5 mm wires of the alloy were solution heat treated at 510 °C for an hour, quenched in ice water, and precipitation heat treated at the temperature range 150–200°C for the time range 2–24 h. Results show that strength and hardness increase with aging time at the precipitation heat treatment temperatures 150 °C, 165 °C, and 175 °C, but decreased with aging time at 185 °C and 200 °C. The increase was due to the precipitation of finely and uniformly coherent needle-like Mg2Si precipitates, β″. The decrease was due to the precipitation of the semi-coherent and incoherent rod-like Mg2Si precipitates β′ and β, respectively. Electrical conductivity increases with the aging temperature and time. Maximum conductivity was 60 %IACS obtained after treatments (185°C, 18h), (200 °C, 13h), and (200 °C, 24h. Optimum mechanical properties were obtained after the treatment (165 °C, 18 h) (313 MPa, 8%, 95 HV, and 57.7 %IACS). Optical micrographs verified the correlation between the microstructural grain size and both the mechanical and electrical properties.
Comparison of Clustering Techniques for Feature-Based Toolpath Generation in Dieless Manufacturing
Authors: Nagargoje Aniket , Kankar Pavan Kumar , Jain Prashant Kumar , Tandon Puneet
Published: January 2022

The aim of the current research is to compare the data clustering techniques for the geometrical feature extraction. The CAD models of the geometries are sliced to generate the data sets for clustering. This paper presents the comparison of K-means, Spectral, Density-based spatial clustering of applications with noise (DBSCAN) and Single Linkage Hierarchical (SLH) clustering techniques for arbitrary shaped contour clustering and formation of the groups based on the means of the contours. The factors considered for the comparison include, the inputs desired by the clustering techniques; time taken for contour clustering; ability to identify the arbitrary shaped contours; and the ability to form the features in feature-based toolpath generation in dieless manufacturing. The paper discusses three different approaches designed to accomplish the task. From the comparative analysis, it is found that the Spectral, DBSCAN and SLH can identify the arbitrary shaped contours. Further, DBSCAN and SLH clustering techniques can form the groups that can be used for feature-based toolpath generation in dieless manufacturing, whereas the other two fails to perform the same. The DBSCAN performs the contour clustering faster than the Spectral and SLH clustering.
Development of an Automatic Detection and Regulation Model of Brush Wire Pressure for a Micro Aerospace Components
Authors: Kang Yonggang , Ren Haodi
Published: January 2022

Micro-component brush wires are important parts of many conductive structures. The pressure of the brush wires has a crucial influence on product performance. Testing and adjusting the pressure of the brush wires is a key step to improve product performance. The existing measurement and adjustment schemes are poor in accuracy and low in automation, and rely heavily on the experience of workers. This study has developed a set of high-precision automatic brush-pressure testers, obtained the rule of brush-wire pressure adjustment through simulation calculations, and realized the high-precision, automatic measurement, and adjustment of brush pressure.
A Novel Fractional Fixed-Time Sliding Mode Control Method for Spherical Robot Linear Motion Speed Control
Authors: Ting Zhou , Yugong Xu , Bin Wu
Published: January 2022

This paper studies the linear motion speed control problem of an underactuated spherical robot under unknown disturbances. A novel fractional fixed-time terminal sliding mode control with a nonlinear disturbance observer is proposed for the spherical robot to achieve fast stabilization and robust control performance. First, a novel fixed-time terminal sliding surface is proposed by adding a fractional differential operator in the traditional integer order fixed-time terminal sliding surface. A nonlinear disturbance observer is designed to estimate the unknown disturbances. Then a fractional hierarchical sliding mode speed controller is designed based on the novel fractional fixed-time terminal sliding surface and the nonlinear disturbance observer. Through the Lyapunov stability theorem, the boundedness of each sliding surface is achieved, and the stability of the whole system is guaranteed. The effectiveness of the proposed controller has been verified via simulation work. The simulation results show the fractional sliding mode controller has a shorter settling time and lower overshoot compared to an integer order sliding controller. When subjected to the abrupt changes of rolling friction, the fractional hierarchical sliding mode controller shows stronger robustness than the integer order one.
Evaluating Bicep Stiffness in Increasing Age Groups
Authors: Salman Muhammad , Contois Zachary , Tanveer M. Hassan
Published: January 2022

Over many years muscle tissue is continuously broken down and reformed through hypertrophy, where the muscle is damaged and then the fibers are fused together to increase muscle in mass and size. As a person ages muscle tissue makeup changes based on 2 significant factors: lifestyle and genetics. Diagnosing significant injuries in this tissue requires the use of expensive technology (magnetic resonance imaging or electromyography) and invasive techniques. The focus of the study is to find an accurate, cost effective method to analyze muscle stiffness, and to observe a trend between age and muscle stiffness. The devices used in the study are a Modally Hand Impact Hammer, and three miniature PCB accelerometers. In order to capture data, the Impact Hammer is used to excite a shear wave across the Bicep Brachii. From there, the data is collected in a Signal Express software and evaluated for accuracy within MATLAB figures. The data was collected from 10 subjects. There was no clear indication that age affected the stiffness. However, this could be disproved by collecting data from a larger subject pool. The data collected was validated by other studies using tried methods.
An Experimental Investigation Onto the Effect of Two Design Methods of Leading-Edge Tubercles on the Aerodynamic Performance of a High Lift Airfoil at Low Reynolds Number
Authors: Khedr Amr A. , Adam Ihab , Ookawara Shinichi , El-Wardany Ahmed , Hassan Hamdy
Published: January 2022

Inspired by the tubercles on the pectoral flipper leading-edge of the humpback whale, the most acrobatic of baleen whales, sinusoidal leading-edge have been used as a passive flow control method to enhance the stall characteristics of lifting surfaces in different applications. They are supposed to reduce the lift gradually during the stall with an increase in the post-stall lift, however, their enhancement ability in pre- and post-stall is highly dependent on the geometrical parameters and the flow regime. Two different design schemes: nonlinear shear transformation design scheme (NLST) and channelled-like scheme, of the sinusoidal leading edge of the high lift airfoil S1223 are tested and compared with the unmodified airfoil at angles of attack of −6 to 30 degrees experimentally inside a wind tunnel at low Reynolds number Re = 100,000. Experimental data show that Tubercles implemented on S1223 at such a flow regime with either design scheme enhance the post-stall characteristics as much as a 42% increase in lift at some angles for NLST with pre-stall lift penalties. NLST, compared with baseline and channelled models, exhibit a significant increase in aerodynamic efficiency which make it more preferable for wind turbines applications.
Kinematic and Dynamic Modelling and Simulation of Soft Continuous Arm Based on Modal Method
Authors: Kong Qingfeng , Bai Zhengfeng
Published: January 2022

Inspired by the muscle structures of elephant’s trunk, octopus’ arm and tongue, the soft continuous arm developed based on bionics can extend, contract and bend along any point of its structure. Compared with the rigid manipulator, it has the characteristics of high flexibility, complex environment adaptability and safe human-machine interactivity. In this work, a three-dimensional (3D) kinematic and dynamic model of the soft continuous arm based on the modal method is presented and analyzed. The spatial kinematics model of the soft continuous arm is established based on the modal method first, in which the deformation of the soft continuous arm is assumed to be an arc without torsion, and the complex nonlinear function is approximated by a simple mathematical function. The accurate, singularity free and unique modal transformation matrix can be deduced conveniently. Also, it overcomes the limitations of the previous models in which the curve parameters are used and the curvature of the cross section assumes to be not zero as well as the dynamic model does not include the pure linear motion. The modal method can be used to simulate the spatial bending motion, but also effectively overcome the singularity problem caused by using the curve parameters for simulating the pure linear motion. Then, the dynamics model of the soft continuous arm is established using the Lagrange method. Due to large number of complex nonlinear integral operations is inevitably involved, and the computational efficiency is low in the numerical solution, the modal method is used in the numerical simulation, which greatly simplifies the complex nonlinear integral operation and improves the efficiency of numerical calculation. The simulation results of the pure elongation and bending of the soft continuous arm show that the modal method has the characteristics of fast and accurate response.
Electrohydrodynamic Settling Droplet With Weak Inertia Subjected to a Uniform Electric Field Based on the Lattice Boltzmann Method
Authors: Zhang Yimo , Zhang Yu , Luo Kang , Yi Hongliang
Published: January 2022

Electrohydrodynamic settling of droplets is governed by the combined influence of electric field and gravitational field in many practical applications and innovative researches. To simulate the deformation and motion of the droplet under the interaction of gravity and electric stress, a numerically multiphase model based on the lattice Boltzmann method (LBM) is established. A perfectly dielectric (PD) drop suspended in another immiscible medium with perfectly dielectric fluids and a leaky dielectric (LD) drop immersed in a leaky dielectric medium are considered to study the dynamic behavior of an electrified droplet driven by gravity. The predictions of the LBM model demonstrated in this paper are in good agreement with classic analytical solutions and conventional numerical results reported in previous literature, particularly for drops with small deformation. Moreover, the electrohydrodynamics of settling droplets subjected to a uniform electric field which is perpendicular to a weak gravitational field is studied computationally for fluids with various electrical parameters. Numerical simulations for droplets with different permittivity ratios and conductivity ratios are conducted over a range of electric capillary numbers. It is found that, unlike PD settling droplets which always transform into a prolate shape due to the presence of the electric field, whether the LD droplets under weak inertia deform into a prolate or an oblate shape depends on the electrical properties of the dispersed medium and surroundings. This phenomenon is in a similar manner as in the previous work for EHD droplets owing to the imposition of weak inertia. However, with the shape feature unaltered, the electric stress acted at the fluid-fluid surface has a significant influence on the drop deformation and the distribution of charges and consequently results in noticeable changes in transient settling speed.
3D Printed and Nickel-Coated Electrodes for Photocatalytic Electrolysis for Hydrogen Generation
Authors: Ndoye Babacar , Ouedraogo Noufou , Demisse Wondwosen , Grizzle Andrew , Mutunga Eva , Tyagi Pawan
Published: January 2022

The hydrogen-based economy is gaining momentum with the advent of fuel cell electric cars and other systems. Hence hydrogen production becomes critically important to meet a supply demand in the near future. One of the cheapest hydrogen generation sources can be solar energy and seawater or water in the lakes and rivers. One can utilize solar energy to provide electricity or energy for the photocatalytic process to split water into hydrogen and oxygen. Under electrolysis, electricity is supplied to provide the energy required for water splitting converting hydrogen ions into hydrogen gas from the aqueous medium. There is a strong need to create innovative electrodes for hydrogen generation that are economical in production and highly efficient. To address this issue, we focused on designing electrodes for photocatalytic electrolysis for hydrogen generation. We used 3D printing to produce different electrodes with various surface features to provide optimum surface area and used electroless nickel to coat the surface of the 3D printed metal components. It is noteworthy that nickel is a promising metal to produce hydrogen economically. We used the Taguchi Design of Experiment approach to optimize the nickel coating on the 3D printed metal electrodes. We used cyclic voltammetry to quantify the volume of H2 produced by the nickel-coated 3D printed electrodes.
Effect of Coupled Helmholtz Resonators on Sound Control
Authors: Sabat R. , Leveque G. , Pennec Y. , Torrent D. , Djafari-Rouhani B.
Published: January 2022

In our work, we are interested in the effect of coupling between Helmholtz resonators using the finite element model. We show that the coupling between two spheres leads to two peaks of resonance at low frequencies. One of them is symmetric and corresponds to a mono-polar breathing mode. The second one is anti-symmetric and behaves like a dipole. Consequently, the first one produces an isotropic wave in the far pressure field, while the second produces a directional propagation wave. Therefore, by changing the distance and / or the orientation between the resonators, we aim to manipulate and control the direction of the acoustic wave at specific frequencies.
Extending the Life of Classic Cars, the Additive Manufacturing Way
Authors: Luniya Tanmay , Chimata Geetha
Published: January 2022

There has been a steadily increasing global market for Additively Manufactured (AM) products, with a growth forecast of USD 23.75 billion by 2027. Of the various industrial sectors applying AM, the automotive/motor vehicles market takes up approximately 18% share. Saying AM is being widely used in the automotive sector with rapidly growing application avenues is not an overstatement. One such section of the automotive industry is the classic cars. Classic cars are 20 years or more older cars no longer in regular production, preserved and restored for their historical value. Classic cars face a huge problem of spare parts. The non-availability of the spare part leads to the break-down of the car, leaving them as display pieces or eventual scrapping. It is not economically viable to manufacture the spare parts in small volume due to challenges such as high cost of tooling, and indefinite storage time.

Additive manufacturing offers attractive solutions to problems precisely such as these as it requires no additional tooling and can produce functional parts in small batches on-demand, provided accurate three-dimensional model data is available. This 3D model data is converted to one of the AM compatible file formats such as STL, AMF, 3MF etc. and then is processed using a Slicer Software. The slicer software converts three-dimensional (3-D) model data to two-dimensional (2-D) layer information that will be printed by the AM machine. Obtaining drawings or 3-D model information for classic car parts is a daunting challenge in itself, often deemed impossible. However, with the advances in imaging and scanning combined with computer aided design technologies, it is shown to be possible to generate the 3-D model data from even partial or broken parts. Now, producing spare parts using AM is not just feasible but has been successfully applied. Few notable examples include restoration of Elvis Presley’s BMW 507, originally released in 1957, which took two years to complete, Jaguar’s XK120 SE restored in 2017, 2019 restorations of Volkswagens iconic 1962 minivan, Bentley’s 1929 Blowers and Bugatti’s 1926 Bugatti Baby. Not just car manufacturers, but hobbyist collectors also found success in producing spare parts for their classic cars. This paper discusses various types of additive manufacturing technologies used to manufacture classic car parts and the strategic impact after implementing them using the examples of famous restored classic cars. The discussion further includes commercialization of these technologies, challenges, material selection and availability. Additionally, the economic implications and, the future are explored.
Deep Learning-Based Error Mitigation for Assistive Exoskeleton With Computational-Resource-Limited Platform and Edge Tensor Processing Unit
Authors: Fabarisov Tagir , Morozov Andrey , Mamaev Ilshat , Janschek Klaus
Published: January 2022

Recently we introduced a new model-based fault injection method implemented as a highly customizable Simulink block called FIBlock. It supports the injection of typical faults of essential heterogeneous components of Cyber-Physical Systems (CPS), such as sensors, computing hardware, and network. The FIBlock allows to tune a fault type and configure multiple parameters to tune error magnitude, fault activation time, and fault exposure duration.

The FIBlock is able to generate various types of highly adjustable CPS faults. We demonstrated the performance of the FIBlock on a Simulink case study representing a lower-limb EXOLEGS exoskeleton, an assistive device for the elderly in everyday life. In particular, we discovered the spatial and temporal thresholds for different fault types. Upon exceeding said thresholds, the Dynamic Movement Primitives-based control system could no longer adequately compensate errors.

In this paper, we proposed a new Deep Learning-based approach for system failure prevention. We employed the Long Short-Term Memory (LSTM) network for error detection and mitigation. Error detection is achieved using the prediction approach. The LSTM models are mitigating the detected errors with computed predictions only when they were subject to the imminent failure (i.e., exceeded the aforementioned thresholds). To compare our approach with previous findings, we trained two LSTM models on angular position and angular velocity signals. For evaluation, we performed fault injection experiments with varying fault effect parameters. The ‘Sensor freeze’ fault was injected into the angular position sensor, and the ‘Stuck-at 0’ fault was injected into angular velocity sensor. The presented Deep Learning-based approach prevented system failure even when the injected faults were substantially exceeding thresholds. In addition, reasoning for data access point choice has been evaluated. We compared two options: (i) the input data for LSTM is provided from the sensor output and (ii) from the controller output. In the paper, the pros and cons for both options are presented.

We deployed the trained LSTM models on an Edge Tensor Processing Unit. For that, the models have been quantized, i.e. all the 32-bit floating-point numbers (such as weights and activation outputs) were converted to the nearest 8-bit fixed-point numbers and converted to the TensorFlow Lite models. The Coral USB Accelerator was coupled with a Raspberry Pi 4B for signal processing. The result proves the feasibility of the proposed method. Because the LSTM models were converted to the 8bit integer TensorFlow Lite models, it allowed firm real-time error mitigation. Furthermore, the light weight of the system and minimal power consumption allows its integration into wearable robotic systems.
Active Vibration Control of Aerospace Structural Systems for Specified Damping
Authors: Hanagud Sathya
Published: January 2022

Active vibration control is essential in several aerospace structural systems, such as large space structures, twin tailed high performance aircraft operating at high angles of attack and helicopters. Goh and Caughey did show that vibration controller designs can significantly benefit from the use of second order systems, in the controller design. In this paper, the subject of the design of active vibration control of buffet induced vibrations in high performance twin tailed aircraft is discussed using a combination of acceleration feedback and positive position feedback in second order systems. The goal is to design controllers to increase the closed loop damping ratio of the structural dynamic system to a specified level that would reduce the vibrations to the required level within a time frame of interest. The approach of Fanson and Caughey needed an iterative approach to design the controller parameters. They had more unknowns and fewer equations. In this paper, the problem is now formulated differently to obtain closed form solutions. This is accomplished by developing a procedure to design second order controllers to obtain the desired closed loop damping while maintaining the stability of the closed loop structural dynamic system. The design procedure starts with an objective to design control parameters that result in coincident closed loop frequencies for each mode. This is followed by a perturbation procedure to seek optimum solutions. The design procedure also yields the needed control authority that should be provided by actuators on the structure. An option to obtain the needed control authority by using offset piezoceramic stack actuator assemblies are discussed. The designed controllers are applied to control buffet induced vibrations of a high-performance aircraft at high angles of attack. This example also illustrates the control authority of the offset piezoceramic stack structural assembly.
Thermal Transport in Carbon Nanocomposites Under Mechanical Strain
Authors: Park Jungkyu , Kinports Nick , Kudsy Jihad
Published: January 2022

In the present research study, we employ molecular dynamics simulations to investigate strain effect on the thermal conductivity of the polymer composites of carbon nanotubes (CNTs). The results show that the composite exhibits higher thermal conductivity than polymers. The thermal conductivity of polyethylene is only 0.45 W/m-K while the thermal conductivity of the composite reaches 0.57 W/m-K by being combined with a (10,0) single-walled CNT (SWCNT). It is observed that the thermal conductivity of the composite increases up to 1.01 W/m-K with an increase in strain until C-C bonds in CNTs start to break. Strain rate is found to be related to the thermal conductivity of the composite; lower strain rate improves the thermal conductivity of the composite more efficiently by straightening the polymer chains better. By stretching polymer chains while leaving CNTs unstretched, however, we found that phonon scattering between polymer chains and CNTs is increased because of the increased surface contact between the polymer chains and the CNTs, impacting the thermal conductivity of the composite negatively. The results obtained in the present research study will be used to tailer the polymer composites of carbon nanostructures to have a better thermal performance under mechanical deformation, accelerating the development of futuristic flexible electronics and wearable devices.
Design, Modeling, Simulation, and Testing of Flexible Joint
Authors: Munguia Maria , Shibata Gabriella , Castro Osvaldo , Miesner Spencer , Asadi Sufi , De Leon Anthony , Hernandez Allan , Molina Christopher , Bell Jered , Lytle Madison , Wolk Kieran , Roberts Scott , Furst Benjamin , Sunada Eric , Bellardo John , Daimaru Takuro , Kuo Jim
Published: January 2022

Metal materials are used widely in industry for piping, as they provide desirable material properties for use in harsh environments. In this work, we explore different flexible pipe joint designs that enable fluid transport in flexible heat transfer devices. Flexible joints would allow heat transfer devices to fit in variable cooling areas. The proposed flexible joints will be 3D printed in metal with the goal of maximizing their bending angles, while minimizing volume. The objective of this research is to develop flexible pipes to connect parts involving fluid flow, and we propose three types of flexible joint designs: 1) helical coil spring, 2) torsional coil spring, and 3) serpentine structure. Then, we introduce a low-cost design process to improve these joint designs.

Metal 3D printing offers increased design flexibility in comparison to traditional metal manufacturing methods. However, metal 3D printing can be labor intensive and costly, thus the number of design iterations using metal printing should be minimized during the design process. To reduce the frequency of metal prototyping, we used plastic 3D prints for rapid prototyping and evaluation.

The flexible joint design considered the effects of pipe shape, pipe size, pipe diameter, free length, and total pipe length. Although mathematical models exist for the three types of flexible designs, they tend to be complex, difficult to implement, and specific to certain types of boundary conditions. In our experience, it is faster and more meaningful to perform experimental parametric studies using plastic prints due to accessibility and cost-effectiveness of plastic 3D printers. However, analytical models do offer significant insights during the design process. Thus, we developed simple analytical models for each of the three types of flexible joint designs which can be used in the initial design phase.

Tests were performed to characterize the designs. Then, finite element simulations were performed for plastic prints and these simulations were validated against experimental data. We show that the results from analytical models, finite element simulations, and testing results for plastic prints are consistent, and these tools can be used to predict performance. In this paper, we discuss the following findings: 1) development of simple analytical models, including successes, limitations, and challenges; 2) the role of finite element simulations in the design process; 3) testing results from the three types of joint design; 4) quantification, interpretation, and discussion of testing results.
A Deep Convolutional Neural Network-Based Method to Predict Accurate Fracture Strength of Poly-Crystalline Graphene
Authors: Shishir Md. Imrul Reza , Elapolu Mohan Surya Raja , Tabarraei Alireza
Published: January 2022

A data-driven deep convolution neural network model is used to predict the fracture properties of polycrystalline graphene from the atomic resolution image. A large dataset is prepared using molecular dynamic simulations and atomic resolution image of polycrystalline graphene. The results show that our model after training can predict the fracture properties of polycrystalline graphene with high accuracy.
Morphological Markers and Determinants of Left Ventricular Systolic Dysfunction in Repaired Tetralogy of Fallot
Authors: Govil Sachin , Forsch Nickolas , Salehyar Sara , Gilbert Kathleen , Suinesiaputra Avan , Hegde Sanjeet , Perry James C. , Young Alistair A. , Omens Jeffrey H. , McCulloch Andrew D.
Published: January 2022

Patients with repaired tetralogy of Fallot (rTOF) are at risk of long-term left ventricular (LV) dysfunction associated with poor outcomes. In this study, we examined the association of LV end-diastolic (ED) shape with components of systolic wall motion (SWM) that contribute to global systolic dysfunction in an rTOF patient cohort. Features of LV shape associated with conicity and septal wall curvature correlated with components of SWM. The effect of ED shape perturbations on SWM were examined in a finite element analysis of systolic ventricular mechanics. Variations in the combination of ED shape and myocardial contractility were able to match predicted measures of SWM. From these results, we hypothesize that greater LV conicity and a flatter septal wall are markers of reduced global myocardial contractility and should be examined further for clinical prognostic utility to improve patient outcomes.
Experimental Investigation of the Combustion Behavior of Jet-A/Water Emulsified Fuel and Ethanol-Blended Jet-A/Water Emulsified Fuel Droplets
Authors: Parveg A. S. M. Sazzad , Hentges Nicholas , Ratner Albert
Published: January 2022

The demanding emission requirements must be satisfied by the modern aero-engines which led the researchers into exploration and development of environment-friendly, and sustainable aviation fuels. Water emulsification in fuels is a proven mechanism to reduce nitrogen oxide (NOX) and pollutant emissions. Furthermore, water addition in liquid fuel can improve the combustion performance and fuel economy by micro-explosions and puffing phenomenon due to the volatility difference between liquid fuels and water. These micro-explosions and puffing result in the breaking of fuel droplets into smaller droplets which promotes secondary atomization of the liquid fuels. The secondary atomization contributes to a higher combustion rate, improves fuel-air mixing, and thus improves fuel economy. Also, with the depletion of fossil-fuel sources, the scientific community is exploring renewable sources which can be both reliable and better substitutes for conventional fossil fuels. Blending biofuel with fossil fuel is an interesting way to a sustainable solution for green energy production and carbon footprint reduction of conventional aviation fuels. In these contexts, the present study reports an experimental investigation on the combustion characteristics of water emulsified Jet-A and water emulsified ethanol-blended Jet-A fuels. The Ultrasonication method is used to prepare homogenized fuel emulsions with three different water concentrations (2.5%, 5% & 10% by weight) for both Jet-A and ethanol-blended Jet-A fuels. Blended Jet-A fuels are prepared for different ethanol concentrations (2.5%, 5% & 10% by weight). Combustion characteristics such as ignition delay, combustion rate, and droplet burning time data are generated for each emulsified fuel. The results are compared for both Jet-A, and ethanol-blended Jet-A fuel emulsions. It is found that there is a general decrease in combustion rate and droplet burning time for all the emulsions. This decrease is higher with higher content of water and ethanol. There is also a general increase in ignition delay. Again, this increase is higher for emulsions with higher water concentration. Hopefully, the outcomes of the present study will increase further interest in combustion characteristics modification of conventional aviation fuels by emulsification. In addition, the findings of the present study will provide experimental data which can be applied for future computational modeling of the combustion process of emulsified fuel.
Tool Remaining Useful Life Prediction in Robotic Machining of Composite Materials Based on Mechanical Vibrations
Authors: Savazzi José Otávio , Shiki Sidney Bruce , Barbosa Gustavo Franco , Guerra-Zubiaga David
Published: January 2022

The development of materials and methods used in the aircraft manufacturing industry has been advancing in order to provide a reliable and light aircraft. The use of composite materials becomes indispensable, meanwhile, the processing of this kind of material must be studied to obtain the higher manufacturing efficiency and the best quality of the final product. Industry 4.0 concepts as internet of things, cloud computing and others can be used to fulfil these demands. In this sense, this study aims to create a remaining useful life prediction model for the tools used on the machining of composite materials with robotic manipulators. This task is performed by monitoring and analyzing the mechanical vibrations of the motor assembly and the cutting tool, then reducing the consumption of this material and ensuring the quality and surface integrity of the finished parts. The self-awareness of the process is improved by combining signal processing algorithms and statistical techniques to assist the constant monitoring of the tool wear. In this sense, a digital model is constantly updated aiming the optimization of the cutting process. In the conclusions of the paper, the advantages and drawbacks of the proposed methodology are presented.
Research on Control Strategy of Automobile Simulate Sound Based on Harmonic Algorithm
Authors: Liu Zhien , Qin Rongpei , Xie Liping , Liu Kai
Published: January 2022

In order to optimize the control strategy of the electric vehicle active voice (ASG) system and improve the authenticity of the simulation sound. This paper presents a sound control method for vehicle simulation based on harmonic algorithm. In this paper, based on the harmonic algorithm, starting from the virtual rotation rate (rpm) input by ASG system, according to the data collected from the actual internal combustion engine car, design control strategy and add shift point in the system. Determine the actual rotation rate of internal combustion engine car and the shift point of throttle opening, and through the python simulation curve. In this paper, using the offset proportional series algorithm to calculate the gear transmission ratio and optimize and simulate it. Since there is no shift or rotation rate mutation in electric vehicle, using quadratic function fitting to optimize the virtual rotation rate. Complete the “virtual rotation rate” transformation of ASG system based on real-time rotation rate of electric vehicle. Finally, the whole optimization system takes the “virtual rotation rate” of the real-time rotation rate of the actual electric vehicle as the input, and takes stm32f7 Series MCU as the hardware carrier. Organize engineers and students with sound quality experience to evaluate the simulated sound quality of internal combustion engine car. The results show that the control strategy proposed in this paper can realize the sound simulation of internal combustion engine car in the electric vehicle cab, and the optimized ASG system can better meet the majority of drivers’ preference for sound than the original ASG system.
Application of Micromechanics to Static Failure Analysis of Graphene Reinforced Epoxy Nanocomposites
Authors: Aluko O. , Li M. , Zhu N.
Published: January 2022

The effect of tensile loadings and proportions of carbon fiber on the allowable stress calculations and static failure analysis of carbon fiber epoxy composites were investigated under uniaxial tensile loadings. Micromechanical modeling analysis was applied to model the failures of composites at the continuum length scale. The results obtained from molecular dynamics analysis of graphene and epoxy, were utilized as inputs in the MAC/GMC micromechanics software to model and evaluate the allowable stress values and static failures of carbon fiber reinforced epoxy composites.

The computed results for composite elastic allowable stress estimation for the average materials and the static failure analysis were compared and these results were in agreement. The study has added to the understanding of the failure mechanism of the carbon fiber reinforce epoxy composites as well as the interactions of the constituents at failure.
Heated Circular Cylinder Subjected to Forced Spanwise Oscillations
Authors: Ali Ussama , Islam Md , Janajreh Isam
Published: January 2022

The influence of spanwise vibrations coupled with various levels of heating, on the lift and drag coefficients, is numerically studied in this work. The flow domain consists of a circular region of 64D surrounding the circular cylinder of diameter D. Transient analysis is conducted to solve URANS using Ansys/Fluent for laminar flow at Reynolds number of 100. Spanwise forced oscillations are carried out using user-defined-functions to mimic the flow induced vibrations. Amplitude of oscillation is kept fixed at 0.1D and frequency of oscillation is varied according to the frequency ratios (f/fn) of 0, 0.5, 1, 1.5, and 2, where 0 means the cylinder is stationary. Four levels of heating is applied, ΔT = 0 for isothermal, and ΔT = 300, 600, 900 K for non-isothermal flow, where ΔT is the temperature difference between the cylinder wall and the oncoming fluid. Air is taken as the fluid and temperature dependent properties of air are considered as the properties change significantly in the given temperature range. Mesh sensitivity is done initially to gain good fidelity of the discretized flow domain and the model is validated using the experimental results from the literature. The non-dimensional natural vortex shedding frequency of the stationary cylinder for isothermal flow is found to be 0.165 marking its Strouhal number. It is observed that heating the cylinder decreases the natural vortex shedding frequency. Increasing ΔT to 300 and 600 K decreased the natural vortex shedding frequency by 14.29% and 28.03%, respectively. It is observed that vortex shedding stops at ΔT of 900 K for stationary cylinder and for forced oscillating cylinder only one peak is seen in Fast Fourier Transform (FFT) corresponding to the forcing frequency. It is observed that the rms of the lift coefficient increases with an increase in the frequency ratio at all values of temperatures. FFT of the lift coefficient revealed only one frequency for frequency ratio of 0 and 1 at the natural frequency of the cylinder whereas for other values of frequency ratio, two peaks are observed, one for the natural frequency and the other for the forcing frequency. Lock-in phenomena is observed at the frequency ratio of 1 for isothermal cylinder where a large increase in the average drag coefficient occurred. For all values of frequency ratio, an increase in the temperature difference results in decrease in the lift and increase in the drag coefficient. Increasing ΔT to 300, 600, and 900 K, increases drag by 7.33%, 11.65%, and 16.52%, respectively, for stationary cylinder and a similar trend in observed for the oscillating cylinder. These results show that heating the cylinder decreases the lift coefficient and the natural vortex shedding frequency of the cylinder, whereas it increases the drag coefficient.
An IDS Investigation of the Instability Features Within Jet Flows
Authors: Gao Yang , Feng Dehua , Thompson Larry , Ferguson Frederick
Published: January 2022

Under-expanded jets are typically formed when the high-pressure fuel is injected into the combustion chamber under ambient conditions. In the case of rocket engines, under-expanded jets are the primary cause of the traveling shock wave formations immediately outside of the nozzle exit. The formulations of these unsteady flow structures, and its development into fully turbulent steady state flows are of interest to designers. Many PLIF experiments on the temporal development of jet flows revealed the existence of highly under-expanded flow, moderately under-expanded and subsonic flow regions, during ‘the injection process’. The under-expanded flow field features consist of the main vortex pair, the vortex-induced shock waves, shock-vortex interactions, and Kelvin-Helmholtz type-structures, their evolution and their interactions until the flow transforms into a fully developed turbulent profile [1–2]. However, these visualization experiments revealed limited or no information of the instability features of the jet, and methods of enhancing their influence. The instabilities within the jets are directly responsible for the turbulence transition process. Further, these instabilities lead directly to the development of fully turbulent flows, the much-needed mixing process within the combustion chamber. The ‘Integro-Differential Scheme’ (IDS) investigation conducted herein, investigated the detailed unsteady flow structures within these jet flows. Further, this numerical study revealed the existing of the Kelvin-Helmholtz instability structures, their evolutions, and their interactions. Further, the IDS unsteady simulations were compared to existing LES and PLIF studies, and they were found to reproduce all the expected flow field features. In the process of investigating the under-expanded jet flow, the IDS numeral method demonstrated that it is capable of fully reproducing the fundamental flow physics within the under-expanded jets. The next step in this study is the manipulation of the flow physics in efforts of enhance mixing.
A One-Dimensional Mechanistic Model for Tracking Unsteady Slug Flow
Authors: Padrino Juan C. , Srinil Narakorn , Kurushina Victoria , Swailes David , Pain Christopher C. , Matar Omar K.
Published: January 2022

A novel one-dimensional slug tracking mechanistic model for unsteady, upward gas-liquid slug flow in inclined pipes is presented. The model stems from the first principles of mass and momentum conservation applied to a slug unit cell consisting of a slug body of liquid and a region of stratified flow containing an elongated bubble and a liquid film. The slug body front and rear are treated as surfaces of discontinuity where mass and momentum balances or “jump laws” are prescribed. The former is commonly applied in mechanistic models for slug flow, whereas the latter is typically overlooked, thereby leading to the assumption of a continuous pressure profile at these points or to the adoption of a pressure drop due to the fluid acceleration on a heuristic basis. Our analysis shows that this pressure change arises formally from the momentum jump law at the slug body front. The flow is assumed to be isothermal, the gas is compressible, the pressure drop in the elongated bubble region is accounted for, the film thickness is considered uniform, and weight effects in the pressure from the interface level are included. Besides specifying momentum jump laws at both borders of the slug body, another novel feature of the present model is that we avoid adopting the quasi-steady approximation for the elongated bubble-liquid film region, and thus the unsteady terms in the mass and momentum balances are kept. The present model requires empirical correlations for the slug body length and the elongated bubble nose velocity. The non-linear equations are discretized and solved simultaneously for all the slug unit cells filling the pipe. Time-space variation of the slug body and film lengths, liquid holdup and void fraction, and pressures, among other quantities, can be predicted, and model performance is evaluated by comparing with data in the literature.
A Model Experiment of Aortic Valve Stenosis to Correlate Narrowness With the Acoustic Spectrum
Authors: Zukowski Hannah , Rupp Marco , Mollel Winrose , Ning Taikang , Byers Clayton P.
Published: January 2022

A model experiment is used to investigate the relationship between a narrowing in a pulsatile flow and the relative energy contained in the measured acoustic spectrum. Inspired by studies of aortic stenosis, this experiment models increasingly severe narrowings in an internal flow with a semi-triangular opening to mimic the shape of an open tricuspid valve. A baseline case is attained through use of dynamic similarity to the average flow through an unrestricted aortic valve. Normalized spectra for each case provides an indication of relative energy in each frequency band which shows how the distribution of energy changes with each restriction. Increasing narrowness of the model valve opening results in enhanced energy content across all frequency bands up to 400Hz. Frequency bands identified as relevant to more extreme cases of stenosis in actual heart valves, such as the 40Hz–80Hz band, show significantly increased overall energy in these model cases. While all restricted cases demonstrate a nominal amount of increased energy, there appears to be more significant changes when the narrowing exceeds an area reduction of 40%.
Enhancing University Persistence of Diverse Mechanical Engineering Students
Authors: Fertig Jan , Kumpaty Subha
Published: January 2022

This paper is the third in a series of efforts to address the troublesome departure of promising college students, most notably women and minorities, from the field of mechanical engineering and similar disciplines. Despite widespread and largely successful efforts to increase the numbers of women and minorities in engineering education, their numbers continue to shrink at a time when they should be expanding. Our first inquiry (IMECE 2017-72597) proposed a mismatch between the empathizing tendency of many students and a climate that discourages professional outlets for such tendencies; as well as incongruencies between professional and engineering identities. We argued that female students were deterred from their engineering aspirations by a climate that included engineering stereotypes, a traditional male-style hierarchy, and differential treatment. Our second endeavor (IMECE 2020-23679) showcased findings from a subsequent STEMpathy study we conducted at our own institution that inspired a persistence model that placed social responsibility goals, or the desire to pursue a career for the betterment of humanity, as well as treatment of students, front and center in the effort to better understand female and minority persistence. Surrounding that goal orientation are categories of factors that deter women and minorities that can be categorized as: 1) Cultural ideological forces; 2) Social structural factors; and 3) the Organizational culture of mechanical engineering. The current undertaking advances empirically based recommendations on ways to: 1) foster a more inclusive engineering culture; 2) enhance the curriculum; and 3) improve public perception of mechanical engineering with the aim of boosting students’ desire to embrace and persist in mechanical engineering. Persistence data from our study informs a five-year NSF grant: S-STEM: The Mechanical Engineering Retention, Academic Success and Career Pathway Program (NSF: DUE-2027632).