bluuebunny/crossref_metadata_2025 huggingface dataset:
Digital Feed-Forward Gas Flow Rate Control With a Switched Nozzle Valve
Authors: Martin Christopher R. , Batzel Todd D. , Liebmann Ethan H.
Published: January 2022

This work presents the (SNV) approach for feed-forward gas flow rate control, the considerations included in the design of a prototype, and the results of its evaluation using a bell prover. The SNV uses a pulse-width modulation approach to provide inexpensive feed-forward gas flow rate control in contrast to closed-loop systems with thermal mass flow sensors. Attempts for feed-forward digital control of gas flow rate with throttling is usually frustrated by the difficulty of precisely and repeatably locating a throttle body to the precision required. The SNV uses a statically machined transonic nozzle to provide a mass flow rate insensitive to back-pressure for the on portion of the switching cycle. The severe pressure drop usually associated with sonic flow is almost entirely recovered by using a converging-diverging nozzle instead of a plain orifice, so that excellent metering can be achieved with drops as low as 11%.

Uncertainty in the actual delivered flow is found to be ±1% of full scale. Back-pressure insensitivity is found to be ±0.5% up to 88% of the supply pressure. The operator design predicted that operation would be possible up to 100Hz, but actual performance was limited to roughly 33Hz. Unexpected minor quadratic behavior in the valve calibration and a single errant data suggest that the degraded performance is due to migration of lubricant inside the assembly.
A Study of Flow in Atherosclerotic Arteries Using Virtual and In-Vitro Models and Its Implications Regarding Vessel Erosion
Authors: Salinas Manuel , Weber Evan , Veras De La Rocha Paula , Cox Caylee , Yanello Jonathon
Published: January 2022

Despite the prevalence of atherosclerosis in the western world, many questions have yet to be answered about the origin, development, and failure of atherosclerotic lesions. To better understand atherosclerotic events such as formation and vessel erosion, a bioreactor chamber was developed using similitude theory together with human coronary artery parameters for geometry and flow conditions. The chamber was virtually validated using Ansys CFX. Simulations were performed under laminar flow conditions, density = 1060 kg/m3, and viscosity = 3.5 centipoise. We applied a velocity waveform at the inlet modified through similitude theory to match that of a human coronary artery. Zero relative-pressure condition was set at the outlet. No slip boundary conditions were prescribed at the coronary artery walls. The results showed that the novel bioreactor can create flow disturbances like those observed in human atherosclerotic arteries. In our future work, we would like to include vessel compliance and experimental data utilizing porcine arterial tissue. Our overall goal is to delineate the entire repertoire of events that happen during vessel erosion.
Strength and Qualities of Mixed Additive Manufacturing Materials
Authors: Addeo Seth , Nowicki Margaret , McDonald Kenneth , Zander Nicole
Published: January 2022

Filament shredders and extruders greatly expand the additive manufacturing material selection. By using recycled filaments, waste and future costs can be efficiently cut while creating in-house, customizable, filaments. Testing mixed filaments is necessary to determine the physical and chemical benefits and costs of mixing filaments. This work aims to characterize mixtures of Polylactic Acid and Acrylonitrile Butadiene Styrene. Mixtures were characterized through tensile strength testing and differential scanning calorimetry of extruded filament samples. The tested mixed filaments were found to be comparable to purchased filaments, with drastic increases in elasticity and decreases in torsional strength and tensile strength. This study shows that while possible to produce mixed filaments, and in spite of their chemical similarities, mixtures are not comparable in physical strength to pure filaments.
A Micropolar Metabeam With Nonlocal Feedback Control Circuits
Authors: Wu Qian , Huang Guoliang
Published: January 2022

Active control schemes provide emergent wave properties and flexible tunability in mechanical systems. Here, we propose both analytically and numerically a non-Hermitian metamaterial system enabled by piezoelectric patches and electronic non-local feedback control. The metamaterial system is physically realized by a non-local microploar beam with non-local feedback control. Since the non-local feedback control breaks spatial reciprocity, the proposed metabeam supports not only non-reciprocal flexural wave amplification and attenuation, but also non-Hermitian skin effect featuring bulk localized eigenmodes in the finite structure. The non-reciprocal amplification and attenuation phenomena are quantitatively predicted by band structure analyses under both the continuum and discrete spring-mass representation, which can be attributed to the work exchange between mechanical and electric works. The non-Hermitian skin effect and the associated bulk localized eigenmodes are characterized by a topological invariant. In addition, direction-dependent bending stiffness is also demonstrated in the non-local micropolar piezoelectric metabeam with proper transfer functions. The electronically controllable non-Hermitian metabeam could pave the ways for designing future systems such as synthetic biofilaments and membranes with feed-back control schemes.
Development of a Topology-Optimized Structure for Electronics Cooling Under Natural Convection Conditions
Authors: See Yao Song , Ho Jin Yao , Leong Kai Choong , Wong Teck Neng
Published: January 2022

A topology-optimized structure for thermal management is developed. The topology optimization is performed based on the minimization of objective functions under natural convection in two-dimensional space. The Boussinesq approximation is included in the momentum equation to simulate natural convection. A RAMP-style function is applied to the thermal conductivity in the design domain so as to clearly define the solid and liquid regions. The solid region represents AlSi10Mg, a high thermal conductivity aluminum alloy that is used for additive manufacturing, while the liquid region represents the phase change material (PCM). The optimization was computed with COMSOL Multiphysics. The structure is successfully fabricated by Selective Laser Melting (SLM) using AlSi10Mg powder. Experimental investigations of this structure were performed together with two conventional designs fabricated with Al-6061; one with five longitudinal fins positioned radially from the heat source and the other with no surface enhancements. The PCM used in the experiments is RT44HC. The experiments involved allowing the PCM to completely melt at two heat rates of 27 and 48 W. All structures were placed in the horizontal orientation. Our preliminary experimental studies suggest that the topology-optimized structure has a lower rate of increase in base temperature during post-melting compared to the two conventional designs, primarily due to the efficient transfer of heat by natural convection.
Components Residual Stress and Deformation Reduction: An Integrated Process Design for Additive Manufacturing
Authors: Dalpadulo Enrico , Pini Fabio , Leali Francesco
Published: January 2022

Additive Manufacturing (AM) is a key technology in current industrial transformations thanks to the significant benefits that can bring to high-level sectors. Nevertheless, AM-based design approaches require improvements that are fundamental to exploit the potentials of the technology and reduce the lack of process consistency. This work focuses on integrated Design for Additive Manufacturing (DfAM) approaches for product-process design, to meet both functional and technological targets. The key aspects of process design and issues are summarized and the design method to perform metal AM process optimization is presented. The aim is therefore to minimize process-induced defects and flaws of AM-based manufacturing of metal products, such as residual stress and distortions. The approach consists of industrialization task improvement based on modelling optimization and build optimization sub-phases supported by numerical process simulation. Integration of CAD platforms allows embedding these steps to be performed downstream of the product design, which can be achieved through functional or multifunctional optimization techniques as well (e.g. topology optimization, latticing, graded structures/materials). The design method is finally applied to perform the industrialization phase of a high-performance automotive component. The case study is a formula SAE topology optimized brake caliper to be produced by Selective Laser Melting (SLM) process. Process simulation-driven studies on modelling and build preparation subphases (i.e. orientation definition, supports generation, model distortion compensation) are conducted to support the process design. The study demonstrates the part scale level method’s suitability to industrial context to improve industrialization in the redesign of components to be produced by metal AM.
Characterizing Potential Damage to Landers and Their Payloads Caused by Regolith Ejecta During Operations on or Near the Surface of the Moon, Mars, and Other Worlds
Authors: Roux Vincent , Duan Shawn
Published: January 2022

This research established methods of physical testing and analysis to characterize damage to a lander caused by rocket-propelled regolith during powered operations on or near the surface of the Moon, Mars, and other worlds. An emphasis was placed on using commonly available test materials to help lower cost.

Lift-off using different thrusts were conducted in atmosphere from simulated planetary regolith. Testing was conducted with a scale model of a recent commercial lander with functioning scale rocket analogues using compressed gas as a propellant. This enabled testing to be safer and more cost-effective compared to operating rockets that burned fuel.

Methods of quantifying and interpreting potential impact and abrasion damage and dust covering were established using crushable foam plates, adhesive coverings, and selective color processing of test result images.

This testing can be an important and valuable step in a wider testing program to identify key design revisions before incurring the expense and risk to equipment from testing rocket and regolith interactions in a vacuum facility. This testing requires an awareness of the effects of scale and the limits of testing in atmosphere compared to the lower pressure or vacuum at the intended landing site.
Development of Multilayer Insulation Blanket of Aerogel With Ultra-Low Thermal Conductivity
Authors: Li Xiaoyu , Chen Kai , Shen Chengcheng , Xu Zhao , Sheng Qiang , Zhao Haifeng
Published: January 2022

Multilayer insulation (MLI) blanket is one of the most reliable passive thermal-control materials for spacecraft. Existing MLIs are typically composed of layers of high-reflectivity thin films with low-thermal-conductivity polyester netting or fiberglass paper as spacers. However, conventional MLI loses most of its insulating capability at pressures greater than 10−6 Pa.

To solve this problem, a new kind of MLI was developed in this work with metalized polymer layers separated by silica aerogel sheets. Due to nanoporous structures of aerogel spacers, heat transfer is effectively suppressed inside MLI in gaseous environment. Its effective thermal conductivity keff was measured at different temperatures and pressures with the one-dimensional heat transfer method. Then the correlation of keff was developed. The result shows significant improvement in thermal insulation for the present MLI, which can provide broad prospects of application for non-vacuum scenarios and extreme environmental exposure conditions.
Application of Adaptive Neuro-Fuzzy Inference System Model on Traffic Flow of Vehicles at a Signalized Road Intersections
Authors: Olayode O. I. , Tartibu L. K. , Okwu M. O.
Published: January 2022

In recent years, most traffic accidents and congestions usually occur at road intersections in urban areas where the vehicle speed is high. This has necessitated the need for intelligent road transport systems and high-level algorithms to unravel the problem. In this study, the South Africa Road transportation system has been used as a case study to address traffic flow solutions at signalized road intersections using traffic flow variables such as traffic density, speed of vehicles, and traffic volume as decision variables. This paper focuses on using a hybrid creative algorithm based on signalized traffic flow to address the constant repetitive traffic congestion problem. The proposed hybrid algorithm is the adaptive neuro-fuzzy inference system (ANFIS). The speed of vehicles within the investigation period, the traffic density of the road network, and the traffic volume of vehicles on the road were used as input and output variables, respectively. Triangular membership function and Gaussian membership function were used for input and output variables, and rules were developed based on available traffic flow parameters. The result of the ANFIS model showed a training and testing performance of 0.8722 and 0.9370, respectively. This training and testing results showed that the ANFIS model is an effective model for optimizing traffic flow at signalized road intersections.
Design and Development of Pellets/Granules Extrusion System for Additive Manufacturing
Authors: Krishnanand  , Taufik Mohammad
Published: January 2022

Fused filament fabrication (FFF) is one of the state-of-art and most popular extrusion-based additive manufacturing technology. This technology is popular due to its affordability, simple design, and compact size. In FFF technology, a wire form polymer material called filament is pushed inside a heated chamber using an extruder motor and teethed wheel. In a heated chamber, this filament is converted into semi-solid form and extruded out of the nozzle to fabricate the part. Producing the wire from raw polymer increases the cost as well as limits the used material up to such polymers, which could form a thin and long, continuous, and uniform wire with certain rigidity and other mechanical properties. Hence, the use of filament increases the cost of FFF technology and available wire-based 3D printers are limited by their material availability in the form of wire. These limitations could be eliminated by using a screw-based extrusion mechanism, in which feed materials would be used in pellets or granules form. Since studies on the development of commercial 3D printers based on pellets/granules extrusion were usually neglected. Hence, in this study initial efforts have been made to design and develop a pellets/granules-extruder, which does accept a wide range of materials that are generally available in the market for conventional manufacturing processes. Further, flexible materials and the material which can’t be converted into filament could also be used as feed material in the form of pellets/granules by using the developed system to fabricate a part for different industrial applications.
Multiphysics Modeling of a Faulty Rod-End and Its Interaction With a Flight Control Actuator to Support PHM Activities
Authors: Bacci Alberto , Bertolino Antonio C. , De Martin Andrea , Sorli Massimo
Published: January 2022

Spherical joints, or rod-ends, are critical components employed in flight control systems to connect the actuator to the aerodynamic surface and to the airframe. As any mechanical component, rod-ends are subjected to a wide range of failure modes, which can cause catastrophic effects at the actuator level and hence at the aircraft level. Despite this criticality, they are often overlooked in studies concerning the definition of new Prognostics and Health Management systems for flight control actuators, mainly due to the lack of sensors to monitor their behavior. The definition of a physics-based model of the rod-ends is hence a required preliminary step to pursue the definition of novel Health Monitoring schemes able to detect the fault inception in these components and track their evolution in time up to failure conditions. In this paper, a model working under few simplifying assumptions is proposed, complete with a Finite-Difference Method solution for the behavior of the lubricating film. The proposed model is then applied to a pre-existing, experimentally validated model of the flight control actuators of an in-service, wide-body commercial aircraft in presence of excessive backlash. Comments on the rod-end model are presented and further work is laid out.
The Effect of Valve Closure Time on Water Hammer
Authors: Davies William , Wolf Malima , Barry Michael , O’Hern Sean , Morse Tim
Published: January 2022

Water hammer is a phenomenon that can cause failure in many different fluid systems, including residential water systems, municipal water distribution systems, oil and gas applications, power plants, and chemical processing systems. By understanding the magnitude of the pressure increase that may develop as a result of different system operating conditions, an engineer can better assess the risks of failure and/or the causes of a failure that has already occurred. In this study, an experimental setup at the scale of a residential water system is used to measure the pressure rise generated when varying the fluid velocity and duration of valve closure time. Comparisons are made between the measured pressure values and the estimated pressure values from existing classical models on fluid velocity and valve closure time with respect to water hammer. While the underlying trends of the classical theory are observed in the experiments, a discussion of the notable deviations from theory is presented, along with other considerations that are relevant to measurements in a specific physical system. This study also provides a comparison between the measured results and the standards and methods that are commonly relied upon for certification of plumbing fixtures as required by building codes such as the International Plumbing Code or Uniform Plumbing Code.
Wind Harvesting on Mars: Study and Approach (II)
Authors: Qomsiya Mohanad , Fletcher Robert W.
Published: January 2022

In previously presented work the authors provided a systematic approach for implementing sustainable energy harvesting projects on Mars. The proposed methodology serves to lay the infrastructure for future In-Situ Resource Utilization (ISRU) on the Martian planet. In this new and updated work the authors thoroughly investigate and report the results of selected site locations for possible future crewed missions. Moreover, it also sheds the light on the multiple wind turbine airfoil designs that would be appropriate for the Martian atmospheric parameters, including the outcomes of Computational Fluid Dynamic (CFD) studies.

In order to assure survival rate for a successful future habitation on Mars, multiple sites were studied and analyzed through the utilization of a General Circulation Model (GCM) simulation, Java Mission-planning and Analysis for Remote Sensing (JMARS) database, and other resources. One of the important factors that was considered during the evaluating of potential site locations is the availability of water resources, as it is crucial for the thriving of any possible human inhabitancy. The geographical location focus of this research work (including the two proposed site locations) is concentrated in the Northern Hemisphere. The two locations are in the Deuteronilus Mensae and Phlegra Montes.
Generative Design of a Novel Additively Manufactured Solar Array System for Powering Space Equipment on the Lunar Surface
Authors: Rios Jaime , Velazquez Carlos , Rakotomanana Teddy , Kabir Mehdi , Xu Jiajun
Published: January 2022

The moon poses harsh conditions including excessively cold 14-day nights in some locations. However, the South Pole of the moon receives sunlight 100% of the time in summer and 70% of the time in Winter. NASA is, therefore, seeking to land at the South Pole by 2024 under Artemis missions and deploy solar arrays to power landers, rovers, and other equipment in order to facilitate a sustainable presence on the moon. Artemis project also seeks to lay the groundwork for a crewed mission to the Mars. To meet the NASA needs for Artemis mission, the desired solar array system is required to cover a large surface area to maximize the capture of solar irradiance when the arrays are deployed 10 meters above the lunar terrain. Additionally, the design must be lightweight, capable of being redeployed and retracted with minimal human interaction, and can withstand lunar dust, radiation, and extreme temperatures. In the present study, a scale-down working model of the prototype (1:10th scale) is introduced with a particular emphasis on the mechanical mechanisms of telescopic boom, tower, and deployment/retraction of solar arrays. The solar arrays are encased in a cylinder that sits atop the telescopic boom and can be deployed irrespective of the boom height. This study attempts to use principles of Geometric Origami to create a novel structural design that allows for a large-diameter array to be rigid without a supporting skeletal structure. By removing the rigid supporting structure, the design becomes highly portable and easily packable and deployable. Once the design is finalized, Fusion360’s Generative Design Suite will be used to optimize the strength-to-weight ratio and manufacturability. Conducting topology optimization based on finite element modeling to meet the required criteria on the weight, strength, durability, and rigidity leads often to irregular geometries which are not possible to be fabricated using conventional manufacturing. However, additive manufacturing features the ability to develop and fabricate the proposed innovative design.
Problem-Based Learning: A Case Study Demonstrating the Benefits of a Post-Freshman Summer Invention Program on Thermal Fluid Sciences Engagement and Professional Development
Authors: Kim Andrew , Wootton David
Published: January 2022

Project-based learning (PBL) is a popular pedagogical strategy used in engineering education to improve students’ engagement, understanding, and soft skills. The thermal fluid sciences (TFS), including thermodynamics, fluid mechanics, and heat transfer, are infamously challenging core engineering subjects. TFS is traditionally taught through lectures, problem sets, and small projects starting in the second or third year of engineering curricula. However, pure PBL is often reserved for after students have completed the traditional courses. This case study follows a student who experienced a reversed pedagogy, wherein pure PBL instead of traditional lectures drove TFS education. In a summer invention program after the principal student’s first year, he invented a novel door fan that improved air circulation between adjacent rooms, even with the connecting door closed. He used computational fluid dynamics (CFD) to simulate his invention. He then enrolled in a formal CFD class in his second year without taking prerequisite TFS courses. Afterward, the student enhanced the CFD simulations of his invention and wrote a technical paper on his results. This case study analyzes the pros and cons of the reversed pedagogy and the early timing of pure PBL through the principal student’s experience.
Innovative Approaches to Enhance Awareness on Additive Manufacturing in Engineering Education Towards Competencies for Industry 4.0
Authors: Atatreh Saleh , Alyammahi Mozah , Susantyoko Rahmat Agung , Ismail Hesham , Mohammed Abdalla
Published: January 2022

Additive Manufacturing (AM) technologies offer numerous solutions to today’s challenges and a variety of applications. Since AM is a promising manufacturing route and is frequently involved with product development, the designing process for such products or parts involves multi-disciplinary teams, such as subject-matter experts and AM processing experts. Often, there is a gap in communication between the two sides occurs in such projects, leading to multiple avoidable iterations that can affect the project resources and outcomes. This study proposes an innovative approach to teach AM for engineers from multiple disciplines to be involved in future projects that integrate AM. The course was designed using three teaching strategies and approaches, which are Design with Additive Manufacturing, Project-Based Learning, and engineering facilitator. The proposed AM accelerated course has proven to be a practical approach that can facilitate the communication process during such projects, resulting in innovative and user-centered solutions. Moreover, the approach is expected to help explore new applications of AM and enhance the AM process workflow in large organizations for spare parts production or product development.
Improving the Performance of Ambulatory Gait Training System for Rehabilitation by Mechatronics and Design Simulation
Authors: Shetty Devdas , Thompson Lara , Sanchez Pablo , Campana Claudio
Published: January 2022

This paper addresses the design procedures and simulation results from the mechatronic model of the rehabilitation equipment, which can improve the functionality and precision of the ambulatory gait training system. The distinguishing feature of mechatronic systems is the achievement of system functionality through intensive integration. The paper demonstrates how the mechatronic design modeling has helped improve the design and performance of the new rehabilitation equipment built by the authors and is known as Navigaitor. The Navigaitor is designed to aid the patients who need to improve their balance and walk. The mechatronics aspects allow a better understanding of the dynamic behavior and interactions of the components. Depending on the severity of the patient’s injury (stroke survivor, Parkinson, etc.), the oscillatory motion can range from uniform to non-uniform. The motion needs to be converted from the oscillatory sinusoidal motion of the patient into linear motion that the system can follow the patient with minimum lag and maximum stability. The data acquired during the training stage showing a different rate of recovery and response assists the system designers and thereby provides input to fine-tune the system and upgrade the control requirements.
Humanoid Loco-Manipulation of Pushed Carts Utilizing Virtual Reality Teleoperation
Authors: Chagas Vaz Jean , Wallace Dylan , Oh Paul Y.
Published: January 2022

Material handling continues to be a large body of research for humanoid robots and loco-manipulation. Cart pushing remains a topic of interest in research and industry, yet attempts to automate a large range of different carts has proved difficult without advanced grasping techniques. To fill this gap, a method utilizing a VR interface for grasping of the cart is proposed. In contrast to previous techniques using a capture point control method, whole body inverse kinematics are used to compensate for additional cart dynamics, along with arm compliance for grasping the cart. Experiments include an operator attempting to grasp a cart that the robot has never encountered, and then walking and steering this cart using the DRC-Hubo humanoid robot. Results are presented analyzing the ZMP of the robot, as well as whole-body kinematics simulation and VR interface validation.
A Small-Scale Experimental Ocean Current Turbine Apparatus for Power Measurement
Authors: Rouhi S. , Xiros N. , Aktosun E. , Sultan C. , VanZwieten J. , Ioup J. , Sadeqi S.
Published: January 2022

The objective of this work is to propose an experimental apparatus setup for a small-scale three-bladed, horizontal-axis Ocean Current Turbine (OCT). This OCT model is under investigation using the University of New Orleans (UNO) towing tank to establish an electromechanical power takeoff system to produce sustainable renewable energy. The system is currently in the design phase. This paper describes the experimental apparatus design by considering sizing elements, bill of materials, schematics, and performance simulation for the expected system. The implementation of an actual experimental small-scale turbine complements the analytical and numerical investigations on turbine design characteristics achieved by ongoing research at UNO based on conformal mapping methods along with Blade Element Momentum Theory (BEM) for generated power prediction. The towing tank experimental approach is used to verify performance of the turbine.
Determinant Search Method for the Large Structural Systems With Small Bandwidth
Authors: Seena Abu
Published: January 2022

In a solution to large eigenvalue problems, the number of required eigenvalues and corresponding vectors is usually much smaller than the order of matrices. For small bandwidth problems, the determinant search method is very efficient and the oldest. Its from a family of nonlinear Eigen solution techniques also referred to as frequency scanning methods. By using the shift technique, it can also calculate the largest eigenvalues. This calculation process involves three steps: polynomial iteration, inverse iteration, and polynomial deflation. The polynomial iteration determines the eigenvalues of interest by looking at a plot of characteristic polynomial versus the eigenvalue λ, which involves evaluating the determinant |K–λM| at fine intervals of λ selected from accelerated secant iteration. The method was developed in the 1970s and was extensively used for only small-size problems due to its limitations. During that time, the memory available was very low for the in-core solver. Also, the numbers generated in polynomial iteration overflows the float point variables in a computer program. Of course, scaling was the obvious choice. However, the method still suffered the numerical scaling difficulties as a determinant of the matrix |K–λM| in structural problems is generally a very fast varying function. Despite different scaling, the number gets overflows after dozens of eigenvalues which made the technique unattractive. The variables type float, double and long double in a computer program can store values up to 1049, 10308, and 104932, respectively, which is not comparatively much smaller than the determinant of small size structural models. In the present paper, a power number representation is proposed in the polynomial iteration. The determinant |K–λM| can be stored in the power form ρD¯n, where prefactor ρ stores the determinant sign, n is the size of the matrix, and D¯ can be calculated and stored accordingly. The order analysis shows the storage of D¯ requires a variable of range 108 to 1010, which can be stored by float or double type variable. The determinant search method gets to be free from limitations and may easily estimate each large eigenpair at higher frequencies independently from all those previously calculated. The determinant search method can also estimate the clustered eigenvalues accurately. The models’ practical significance is in the FEA analysis of beams, frames, buckling analysis, and stress analysis of pipes in the industry. In the present work, the proposed approach has been applied to the piping model. The results show the determinant search algorithm can extract modes in a higher frequency range without any limitations. The modal analysis is the basis of dynamic analyses of structures such as Response spectrum analysis. The inclusion of higher modes ensures that more than 95% of modal mass has been included in the calculation.
Characterization of A325 Structural Bolts Subjected to Impulsive Loads
Authors: Warren Maria , Sanborn Marc , Stewart Lauren K.
Published: January 2022

Structural connections must maintain strength and ductility during and after impulsive loading to prevent widespread failure of a structure. However, a decrease in ductility in response to impulsive loads has been observed both experimentally and in situ. Further, experimental data on the residual capacity of steel structures is limited, especially the residual capacity of impulsively-damaged steel connections. To ensure the safe design of structures, it is necessary to characterize the dynamic and residual capacity of steel connections. To address the lack of data in this realm, an experimental method has been developed to determine the dynamic and residual behavior of A325 high-strength structural steel bolts in single-shear. A high-speed hydraulic actuator is employed for structure-scale experimentation, with impact energies varied from 760 J – 1370 J. Then, surviving bolts are quasi-statically loaded to failure to evaluate their residual capacity properties. Results demonstrate that, below a critical impact energy, A325 steel structural bolts have residual strength commensurate to undamaged bolts, but lessened residual ductility and energy absorption capacity. These data suggest that metrics other than residual strength should be explicitly included in residual capacity analyses. Further, above a critical impact energy, dynamic bolt fracture with a significant loss of ductility has been observed. A loss of deformation capacity at high impact energies (and thus, capacity to absorb energy through plasticity) may increase the susceptibility of a structure to progressive collapse. Therefore, these results prompted further investigation into the dynamic behavior of A325 bolts. Specifically, the sensitivity of material behavior to strain rate is studied using a Split-Hopkinson Pressure Bar (SHPB) testing apparatus. These results, in tandem with the single-shear bolt impulsive test data, are used to evaluate the role of strain hardening in the loss of ductility observed in A325 bolts at high impact energies.
Solid Particle Erosion Behavior of Electron Beam Melted (EBM) Ti6Al4V at Different Built Orientation
Authors: Bin Abdullah Mohammad Sayem , Alajmi Abdullah F. , Ramulu M.
Published: January 2022

The feasibility of the applications of additively manufactured, i.e., electron beam melted (EBM), titanium parts requires acceptable tribological properties alongside acceptable mechanical and fatigue properties. Investigations on the tribological properties of EBM titanium are very limited. This paper aims to study the erosion behavior of as-built and machined EBM Ti6Al4V at two built orientations, i.e., XZ (0°) and YZ (90°). EBM fabricated Ti6Al4V specimens were subjected to silica particle impingement at 30°, 60°, and 90° angle of attacks. The mass removal was recorded, and volumetric removal was measured using an optical profiler. The erosion scars generated on as-built and machined Ti6Al4V plate were inspected through scanning electron microscopy to study the erosion mechanism at these two built orientations. Experimental results show that the erosion behavior of EBM Ti6Al4V is significantly influenced by built orientation. XZ (0°) plates show more erosion resistance due to better solidification. The erosion mechanism is discussed in detail.
A Micro-Mechanical Constitutive Model to Predict Hygrothermal Aging of Cross-Linked Polymers
Authors: Bahrololoumi Amir , Ghaderi Aref , Shaafaey Mamoon , Dargazany Roozbeh
Published: January 2022

A multi-physics material model is presented to describe the effects of temperature, oxygen, and humidity on the constitutive response of cross-linked polymers. The effect of hygrothermal damage on the mechanical integrity of the polymer matrix can be considered as the result of damage accumulation of two independent aging mechanism namely, i) thermo-oxidative, and ii) hydrolytic aging. In order to capture the mutual effects of thermo-oxidative and hydrolytic aging, an assumption has been made that each of the aging phenomenon can be superposed to each other. In fact, each of them works independently and as a result, they can compete with each other. Utilizing the theory of network decomposition, all phenomena and their correlation were modeled and thus, the strain energy function of the polymer matrix is written with respect to four independent mechanisms, i) the shrinking original matrix that has neither been attacked by water nor oxygen, ii) conversion of the first network to two new network due to the reduction and formation of cross-links, and iii) energy loss from network degradation due to attack of the water molecules to polymer active agents. Moreover, the proposed model is micro-mechanically based and is mainly relevant on thin samples due to our underlying assumption of homogeneous diffusion of oxygen and water throughout the matrix. The model has been validated against extensive data-sets obtained from experiments we specifically designed for concept validation.
Hydrokinetic Turbine Performance and Wake Analysis Using a Data-Driven Actuator Line Model
Authors: Bowman J. , Bhushan S. , Burgreen G. , Dettwiller I.
Published: January 2022

A data-driven actuator line model was derived using a blade-resolved turbine DES simulation. Pressure and viscous forces were extracted from the blades and incorporated into an actuator line model framework implementation in OpenFOAM. The data-driven actuator line model attempts to address the limitations of the currently available actuator line model. The development of the data-driven actuator line model transformed the high-fidelity blade-resolved force data into force coefficients. The result is a finely tuned model that can replicate the turbine performance of the blade-resolved model for a fraction of the computational expense. The comparison between the data-driven actuator line model and the actuator line model reveals that at high tip speed ratios the actuator line model over predicts the thrust and power coefficient. The author discusses the limitations of the data-driven actuator line model in its current form and how the model will be advanced.
A Mixed-Mode Analysis of Two Parallel Non-Aligned Cracks in a Large Flat Plate Subjected to Remote Tension
Authors: Perl Mordechai , Levy Cesar , Ma Qin
Published: January 2022

The interaction of multiple cracks plays an important role in cracking behavior resulting from plant degradation, especially in the case of stress corrosion cracking (SCC) and fatigue. The Fitness-for-Service (FFS) standards require the characterization of multiple cracks to determine the structural integrity of cracked components using fracture mechanics concepts. Multiple cracks must first be classified as to whether they are located on the same cross-section plane for alignment purposes. Various codes and standards have been found to have differing crack alignment rules. Using these rules and standards, two parallel, non-aligned cracks have been previously simulated by various investigators in Fitness-for-Service evaluations based on Linear Elastic Fracture Mechanics (LEFM). However, all these studies focused on mode I fracture of cracks. The present study focuses on mixed-mode interaction between two parallel, non-aligned cracks subject to remote uniform tension. A parametric study of the dependence of the mixed-mode Stress Intensity Factors (SIFs), and the energy release rates (ERRs) of two parallel cracks on the intra-horizontal and vertical separation distances is conducted. The evaluation of the SIFs and ERRs was accomplished for a wide range of the normalized intra-vertical separation distances of H/2a1 = 0.4∼2, and normalized intra-horizontal separation distances of S/2a1 = −0.4∼2. It is found that for certain crack configurations mixed-mode analysis might be significant and should be carefully considered in the application of Fitness-for-Service rules.
Modeling the Effects of Surface Roughness Variations on Pressure Drop in Flow Minichannels
Authors: Alghamdi Abdulaziz , Alfaiz Suliman , Alsulami Marwan , Mortazavi Mehdi , Niknam Seyed A.
Published: January 2022

Research efforts are underway to understand the inherent surface roughness in additive manufacturing (AM) particularly in powder bed systems. It has been acknowledged that powder bed systems may suffer from layer variation due to sputtering effects or recoating mechanism. This lack of layer uniformity has negative effects on surface roughness. This research investigates the effect of layer variation on minichannels surfaces through which fluids flows for heat transfer applications. For this, a number of long stainless-steel flow channels with various cross sections were fabricated using selected laser melting technology. In addition, an experimental setup was developed to measure the pressure drop for different gas flow rates. This study provides insights into the relationship between surface roughness deviation along minichannels length and the pressure drop in the flow minichannels.
Virtual Surface Roughness Measurements From an ‘As-Built’ Virtual CAD Model for Bead Based Deposition Additive Manufactured Components
Authors: Kalami Hamed , Urbanic Jill
Published: January 2022

All additive manufacturing processes have a characteristic ‘staircase’ layering effect at the boundaries, as this process family fabricates components by stacking layers upon each other. This effect is noticeable at shallow angles and where there is significant surface curvature. Measuring the surface roughness from virtually modeled beads of an additive manufactured product helps to have an initial estimation of the surface quality during process planning. In this paper, three techniques are developed to measure the profile surface roughness from an ‘as-built’ CAD model generated from theoretical bead geometries. Two CAD files are needed as inputs: a model of the ideal part geometry and the model created based on the bead geometry, percent bead overlap, and the fill strategy. Developed solutions are projection, projection normal-line distance, and elongation method.

The results are verified by analytical calculations with less than one percent variation. The samples include flat faces, a curved surface, and an S shape (a double arc). Sensitivity studies for evaluation length are conducted as well.

Estimation of the surface roughness values before a component is being built will help designers to evaluate how much material stock is needed to be added if subsequent machining processes are required. Therefore, it is anticipated that this research will assist process planners in developing their desired build solutions for both AM and hybrid manufacturing.
Molecular Dynamic Simulation of Diffusion in the Melt Pool in Laser Additive Alloying Process of Co-Ni-Cr-Mn-Fe High Entropy Alloy
Authors: Farias Mathew , Hu Han , Zhang Shanshan , Li Jianzhi , Xu Ben
Published: January 2022

High entropy alloys (HEAs) can be manufactured in many conventional ways, but it becomes difficult of fabricating heterogeneous materials and structures. Selective Laser Melting (SLM) method generally melts pure elemental powders or prefabricated alloy powders without alloying process. In-situ alloying in SLM, which is also called Laser Additive Alloying (LAA), using pure elemental powders becomes a promising method for creating HEA with heterogeneous structures. However, the effect of the diffusion of elements in the molten pool on the formation of HEA remains unclear. In this paper, the well-discussed Cantor HEA was studied in an in-situ alloying situation, where pure elemental powders (Co, Cr, Mn, Ni, Fe) distributed on a powder bed were irradiated by laser and were subsequently allowed to cool back to room temperature. The diffusion of specific elements, with respect to their original clusters, was tracked via Mean Square Displacement (MSD) as well as the final composition of key locations. Our model was verified by showing a good agreement with the overall average diffusion rates of each element in the Cantor HEA qualitatively in other works from literature. Results initially showed that as the energy density increases, better diffusion was observed through a pixel overlay analysis about the mixing of different elements. The best-case scenario of diffusion from the pixel overlay map indicated a strong presence of 3 to 4 elements after the laser scanning. Given the conditions in the MD simulation, there was no apparent segregation of elements during the alloying process. In addition, we also conducted a simulation by implementing a 0.03 nm/ps laser scanning in a meander 2-track scan in order to completely melt the powder bed. After cooling and equilibration, Polyhedral Template Analysis was applied to analyze the crystal structure of the solidified powder bed in the presence of increasing components. When the powders of Cantor HEA were alloyed using LAA approach, all elements experienced a complex diffusion behavior, elements like Cr also experienced a relatively rapid diffusion compared to other elements. Despite this, Cr only diffused for a short period and diffused minimally during the in-situ alloying process. The analysis of element-specific behavior, such as diffusion, can provide a framework for the LAA production of HEA. This MD study provides a detailed analysis about the effect of diffusion on the formation of HEA system if in-situ alloying is adopted, the findings of this study can be used to guide the material design and the appropriate parameters for manufacturing process of new HEAs. This study can also be extended to analyze the effect of diffusion on the thermomechanical properties of HEAs.
Product Design Journey: Novel Tool Changer
Authors: Chagouri Tariq , Al-Darwish Fawziya , Sharif Abdulrahman , Al-Hamidi Yasser
Published: January 2022

This paper presents a product design journey for a group of undergraduate sophomore university students as part of their Geometrical Modeling for Mechanical Design course. The course project aimed to help students to use basic process of engineering design, use a computer aided design (CAD) tool to model their product, engineering analysis tools to evaluate their design, and understand the need for prototyping.

The students started their journey with ideas tournament to select an outstanding idea which would be of a great market value. After intensive consultation with the course instructor and implementing a stringent selection criterion, students chose to design a novel tool changer that incorporates two different grippers with varying performance specifications. The students followed a systematic approach that got them involved in doing very thorough literature review in which they classified most of the grippers and tool changers available in the market. They also sensed how their product could be demanded in industrial applications where the utilization of a single gripper would demonstrate inconvenience. Such industrial sectors would be surgical operations where the operator would require a gripper to hold the flesh and another for cutting or stitching or any other surgical tasks, another application would be welding where a gripper is required to hold the metallic parts and another for performing the welding task. The utilization of two grippers with various designs would also expands the range of tasks that could be accomplished, for instance, a lot of manufacturing facilities requires performing internal and external gripping operations as is the case in car manufacturing, the tool Cha design introduced in this paper would facilitate such tasks by enabling the capability of simultaneous utilization of an internal and an external gripper. This design will also be beneficial in the current global pandemic where human interaction would be a genuine menace.

The systematic approach helped the students also to establish target specifications for their product, decompose the product into different subsystems and explore the whole design space of each subsystem. All concept solutions (fragments) of all subsystems were then compiled in a combination table to select the product final concept and in turn finalize product specifications.

After selecting the preferred combination of concept solutions, a CAD model was established to run the necessary simulations prior to realizing it into a tangible product through either additive manufacturing (3d printing) or subtractive manufacturing (milling, turning, or EDM).

Realizing that many aspects of the product design journey cannot be covered in this course, the students were eager to see how other upcoming courses would help in letting them to carry out more sophisticated tasks in the product design process.