bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal-Fluid Behaviors and Morphology Evolution of Molten Pool During Selective Laser Sintering of Inconel 625
Authors: Xiao Bin , You Byoung Hee , Jin Tongdan
Published: February 2024

A two-dimensional multi-physics finite element model of the Selective laser sintering (SLS) process on Inconel 625 powders is developed. The model is validated through comparison with experimental data previously published in the literature. Thermal/fluid behaviors and morphological evolution of the molten pool are studied, considering phase transition, recoil pressure, surface tension, and the Marangoni force. The simulation outcomes exhibit the time-varying temperature distribution, fluid dynamics, and surface morphology during the SLS process under different conditions, which helps to identify the impacts of process parameters on the SLS process. The results demonstrate that during the SLS process, the morphology and thermal-fluid dynamics of the molten pool are primarily influenced by the Marangoni force and recoil pressure acting on its surface. Specifically, the recoil pressure at the leading edge of the laser spot plays a crucial role in determining the molten pool’s behavior. The recoil pressure increases exponentially as the temperature rises, causing the liquid metal to move downward and form a depression area at the head of the molten pool, and generates particles that are splashed from the rear edge of the molten pool. The backward Marangoni force, which causes high-temperature liquid at the head of the molten pool to flow towards the cooler liquid at the rear, results in the formation of a vortex that moves the molten pool in the rear region. This study analyzes process parameters such as laser intensity, scan speed, and spot size. The results indicate that increasing laser power and decreasing scanning speed and laser beam spot size can lead to an expansion in both the depth and width of the molten pool.
Understanding Surface Form Error: Beyond the GD&T Circularity/Roundness or Cylindricity Callout
Authors: Sahay Chittaranjan , Ghosh Suhash
Published: February 2024

One of the most important fundamental forms for engineering components is the circular cross-section. Circular forms arise in many applications, particularly in bearing surfaces such as rotating shafts and ball bearings. In manufacturing environments, variations on circular features may occur due to imperfect rotation, erratic cutting action, inadequate lubrication, tool wear, defective machine parts, chatter, misalignment of chuck jaws, etc. The importance of studying roundness form deviations of circular and cylindrical features is to avoid the excessive lateral or radial deviations of the rotating and reciprocating parts during dynamic operations. Hence, whether roundness error can be evaluated accurately and efficiently or not will directly influence the part assembly, product’s function/performance and life. For example, it is inferred that a rotational bearing whose components are not accurately round will tend to be noisy and is likely to fail prematurely. However, the current definition of roundness or circularity per ISO or ASME standards considers the surface’s radial deviations only. If these radial deviations are constrained within two concentric circles with minimum radial separation, this radial separation is defined as the roundness/circularity form error. It is, however, difficult to understand how this radial deviation alone can assure functionality while completely overlooking the circumferential variations/deviations on the surface. This paper is an attempt to investigate the form of circularity deviations along the circumference and whether it plays a significant role in the functionality of round machined parts. The investigation focuses on an accurate spindle and turntable type measuring instrument. On this instrument, the component is rotated on a highly accurate spindle which provides an imaginary circular datum. The workpiece axis is required to be aligned with the axis of the spindle by means of a centering and tilt adjustment leveling table. The polar trace obtained off the surface on a section perpendicular to the spindle axis is analyzed through a Fast Fourier Transformation (FFT). This reveals any periodic circumferential deviations in the corresponding amplitude spectrum of the different harmonics. It is intriguing to note that often only one or two amplitudes in the spectrum are significantly larger than the rest and affect the functionality the most. This paper explores how these multitudes of parameters are to be understood and be incorporated into Geometric Dimensioning and Tolerancing (GD&T) drawings, and further be infused in the undergraduate and graduate engineering curriculum, and be taught as an improved toolkit to the aspiring engineers, design & process engineers and quality control professionals.
Richardson-Zaki Exponents for Particles, Drops and Bubbles
Authors: Loth Eric
Published: February 2024

A broad range of experimental data and resolved-surface simulations were surveyed in terms of their Richardson-Zaki exponents for solid particles (spherical, ellipsoidal and irregular in shape) along with spherical drops and bubbles (both clean and contaminated). For these data sets, the Richardson-Zaki exponent often reasonably represents the volume fraction effect on group particle drag increase for moderate volumetric concentrations, ranging from 3% to 30%. A separable effects assumption was used to determine the influence of Reynolds number on the Richardson-Zaki exponent for spheres (including solid spherical particles as well as clean and contaminated spherical bubbles) based on a hydro-static pressure gradient for a homogeneous mixture of particles in a liquid, and this method compared well with experiments. A similar influence was found for non-spherical fluid particles with moderate deformations. However, highly deformed bubbles can cause a drag reduction at high concentrations, owing to deformations aligned with the flow, so a Richardson-Zaki exponent is no longer valid. In contrast, non-spherical solid particles introduce an additional complexity due to changes in particle orientation as volume fraction increases, especially at low Reynolds numbers, which instead accentuates the drag increase due to volume fraction.
Prediction of Heat Transfer During Condensation of Superheated Vapor Flowing Inside Channels
Authors: Shah Mirza Mohammed
Published: February 2024

Many condensers such as those used in refrigeration and in chemical processing involve condensation of superheated vapor inside channels. Several models have been proposed for the prediction of heat transfer under such conditions but there has not been a comparison of these models with all available data to determine which one to use. Several models have been evaluated in the research reported here. All data that could be found was first compared to four models using the measured single-phase and saturated vapor condensing heat transfer coefficients. This identified the best model. The best model was then compared with data using single-phase and saturated condensing heat transfer coefficients calculated by various correlations. The data analyzed included seven fluids (CO2 and six halocarbon refrigerants), reduced pressure 0.00252 to 0.9492, mass flux 45 to 250 kg/m2s, and superheat up to 42 K. A satisfactory method for the calculation of superheated vapor condensation heat transfer has been identified. The results of this research are presented and recommendations are made for design calculations.
Characteristics of Input Signal of a XY and YX Cut LiNbO3 SAW Using Finite Element Modeling
Authors: Janardhana Ranjith D. , Jackson Nathan
Published: February 2024

Surface Acoustic Wave (SAW) devices were traditionally designed for wireless and communication applications; however, their potential has been explored in various other fields. In recent years SAW devices have shown promising results in acoustofluidics. SAW devices operate at higher frequencies (100’s of MHz) which results in high propagation of mechanical waves on the surface which can be utilized in acoustofluidics applications such as cell separation and atomizer. Integration of SAW on acoustofluidics applications solely depends on the device’s ability to generate an acoustic wave with high magnitude to transfer high levels of energy through the liquid. Various factors such as the shape of wave form and amplitude of the input signal to a SAW can affect the formation of mechanical waves on the surface. Hence, the performance of acoustofluidics applications mainly depends on the selection of input signal to a SAW device. This paper analyzes the characteristics of input signals such as the shape of impulse, signal timing, frequency range, and amplitude by considering piezoelectric substrate XY and YX cut LiNbO3. The results were analyzed in relation to insertion loss which is an important parameter to determine the performance of the SAW device.
Experimental Investigation of Nicker Nut Shell Powder Filler Blended Epoxy-Based Biopolymer Composite
Authors: Pachiappan Arumugam , Velukkudi Santhanam Senthil Kumar
Published: February 2024

The need of biodegradable bio-composite materials has significantly increased in recent years for its uses including packaging, agriculture, medicine, sportswear, insulation, paint, etc. Both the environmental and the economical benefits are achieved from the use of natural fibers and natural fillers. Aeronautical and automotive industries use newly identified lightweight biodegradable composite materials because they are strong, light, and consume less energy. They are recognized for having exceptional properties, such as a high strength to weight ratio, a high stiffness to weight ratio, resistance to corrosion, resistance to water absorption, and high hardness. More and more natural fibers and filler materials are being employed in composite materials to lessen the need for the polymer matrix and enhance their chemical, physical, mechanical and thermal properties and so on. This current analysis is carried out experimentally on the impact of adding natural nicker nut shell powder as filler and epoxy resin as matrix on the fabricated biodegradable composites with different volume percentages (5, 10, 15, 20, 25, 30 and 35% so on). On the created biodegradable composites, the impacts of particle size and filler volume percentages on mechanical parameters like tensile strength, flexural strength, and impact strength have been experimentally assessed. Following the standard of American Society for Testing and materials, the specimens were prepared and tested. The mixture of 25% Nicker nut shell powder and 75% epoxy resin produced the highest tensile strength, which measured as 22.05 N/mm2. The blend of 75% epoxy resin and 25% nicker nut shell powder was discovered to have the maximum flexural strength, measuring 46.9 N/mm2. It has been shown that better interfacial adhesion between the filler and matrix allows for the storage of the largest amount of impact energy, 16.29 KJ/mm2, when the filler and matrix are 25% nicker nut shell powder and 75% matrix, respectively. SEM analysis was conducted to analyze the interfacial bonding between the matrix and filler particles with defects in the composites. SEM images are evidence to attribute better mechanical behavior of bio-composites.
Modeling and Analysis of Terrestrial Locomotion Dynamics of Helical Drive-Propelled Multi-Terrain Vehicles
Authors: Beknalkar Sumedh , Varanwal Aditya , Lynch Ryan , Bryant Matthew , Mazzoleni Andre
Published: February 2024

The diverse and heterogeneous terrains in the Arctic, consisting of snow, melting ice, permafrost, ice-covered lakes, sea ice and open ocean, pose serious challenges to locomotion and autonomous navigation capabilities of rovers deployed in the region for data collection and experimentation. The Multi-terrain Amphibious ARCtic explOrer or MAARCO rover is a proposed screw-propelled vehicle that uses helical drives (similar to Archimedes’ screws) to move seamlessly across the diverse terrains in the Arctic. The motion of a pair of helical drives operating in soft or fluid terrain is dictated by the response of the surrounding substrate to the stresses exerted by the rotating helical drives. If the substrate under the rover does not fail when it is moving in a straight line, the linear displacement of the rover (x) and the number of rotations of the helical drives (n) are related through x = P · n, where P is the pitch length of the helical drives. However, when the substrate fails, the linear displacement of the rover is less than P · n, i.e., x < P · n. Thus, “x = P · n” motion represents the optimal mode of operation for the rover when moving in a straight line. This paper represents the first ever attempt, to the best of author’s knowledge, to derive the conditions necessary for the application of the holonomic constraint x = P · n to the dynamics of a helical drives-based rover.
Response of Graphite to Dynamic Loading and Hypervelocity Jet Impacts
Authors: Huddleston Bradley D. , Mason Thomas A. , Gibson Cody , Angell Colter , Rasmussen Nikki
Published: February 2024

The compressive strengths of three varieties of high purity graphite, PCEA, NBG-18, and NBG-25, as well as the depth of penetration of small-scale charges into these materials was experimentally determined. These grades are similar in density, ranging from 1.80–1.85 g/cc, and nominal apparent porosity, ranging from 18% to 20%, but provide a wide range in maximum grain or particle size from 10s to 1000s of μm. Two very different manufacturing methods are also represented; PCEA is extruded while NBG-18 and NBG-25 are iso-molded. The quasistatic and dynamic strengths of each grade were determined on a load frame and split-Hopkinson pressure bar, respectively. The depth of penetration (DOP) of two small-scale shaped charges, the Teledyne RP-1 and RP-4, was determined against graphite. The global response of the RP-4 impacts was markedly different as the PCEA samples remained intact while all the NBG-25 samples split into 2 or 3 pieces after the jet penetration had completed. However, for all tests, the trusted DOPs fell within 2 cm. Preliminary hydrocode modeling of the penetration events used existing models that were not designed for graphite. The results can be tuned to reasonably reproduce the DOP, but the wound channel geometry is not reproduced well. A model designed for graphite would need to represent graphite’s non-linear and energy dissipation characteristics.
A Preliminary Study of Machining Characteristics of Lens Titanium Alloy (Ti-6Al-4V)
Authors: Polishetty Ashwin , Littlefair Guy
Published: February 2024

Titanium alloys are popular and used in a wide range of design applications in aerospace and biomedical industry due to their advantageous material properties. Titanium is categorised into various grades such as Cp Titanium, Titanium5553 and Titanium64. Grade 5 titanium (Ti6Al-4V) is used in this paper. This paper is a preliminary study of machining characteristics of Laser Engineered Net Shaping (LENS) Titanium alloy (Ti-6Al-4V) using face milling. With the advancement in Additive Manufacturing (AM) technologies, components can be easily and efficiently made into various parts with complex geometries that is not possible using traditional manufacturing methods. All materials processed using AM face the same critical problem that the manufactured part requires a post machining since AM produces relatively poor surface finish. This report presents a study of the machining characteristics of a LENS titanium alloy (Ti-6Al-4V) and its behaviour under a milling operation with a set combinations of machining parameters such as cutting speed, feed rate, depth of cut and wet/dry machining. This report also analysed the surface finish of each sample and its correlation to its wrought counterparts. LENS titanium complied with the notion of increasing cutting speed will result in lower cutting force. The cutting force in dry milling is lower than the force in wet milling. The tool wear in dry milling is higher than the wet milling.
Lightweight Design With Topology Optimization for Additive Manufacturing of Aircraft Components
Authors: Kim Tae-Uk
Published: February 2024

The topology optimization (TO) of a landing gear torque link is performed with the goal for making the part via additive manufacturing (AM). The AM is free from many limitations, which classical subtractive manufacturing intrinsically has, thus it can realize the TO results as near net shape. In this paper, two optimization processes are considered for weight reduction. At first, the conventional TO solutions are obtained for minimizing weight with constraints. And then, the lattice optimization process is applied to the solution in which the intermediate density elements are replaced with lattice structures and the member dimensions are optimized. In addition, as a previous stage for prototyping, the tensile test of additive manufactured coupons is conducted to find basic material properties and the results are adopted into the analysis model. For this, specimens are prepared using a titanium alloy Ti6AL4V with a DMLS (Direct Metal Laser Sintering) system. The optimal results show that a combination of TO with AM can be applied to various lightweight designs of aircraft structures.
Development of a Broadband Energy Harvesting Technique Utilizing Acoustic Metamaterials
Authors: Todd Andrew , Ahmed Hossain , Ahmed Riaz
Published: February 2024

A novel deterministic method to harvest energy within a broadband frequency (0 ∼ 25 kHz) from a mass-in-mass metamaterial is presented. Traditional metamaterials are composed of multiple materials (named as resonators and matrix) with different mechanical properties (e.g., stiffness, density). Typically, the mass-in-mass metamaterial consists of a core material, surrounded by an outer shell. The core material is usually made up of a material with higher density and stiffness, while the outer shell is composed of a less dense and lower stiff material. The subwavelength structures within the shell serve to redirect the acoustic waves, resulting in negative density. In this work, the stiffness of matrix materials is altered systematically to allow diversified property mismatch between the constituent components to introduce local resonance in the unit cell. During the material property manipulations, the properties of the resonator are kept unchanged. By manipulating the subwavelength structures in the outer shell, it is hypothesized to optimize the local resonance with higher density of states. A finite element based commercial solver COMSOL Multiphysics is used to develop the dispersion curve, and an in-house MATLAB code is developed to estimate the density of states at a series of eigen-frequencies. To illustrate the broad-band resonances and the energy harvesting at these frequencies, the dispersion relation, and corresponding DOS are used as a predictive tool. While local resonance leverages wave energy passing through the acoustic metamaterials trapped within the relatively soft matrix as dynamic strain energy, a strategic and deterministic methodology is investigated to obtain a broadband local resonance frequency. A correlation is established between the local resonance and the density of states. Using the proposed geometric configurations, the matrix properties are manipulated and a repeated higher density of states within a broadband frequency range is achieved. By predicting a higher density of states, the possibility of energy harvesting capability within this broadband frequency range is enhanced significantly. Hence, the frequency band is utilized to harvest the trapped energy by embedding a smart material inside the matrix which is capable of electromechanical transduction (e.g., lead zirconate titanate). A series of parametric frequency domain studies are carried out to estimate the power densities for a unit external displacement excitation. This concept has been proved numerically by harvesting energy at a broadband frequency with a power density of ∼ 10μW/in2. The harvested power can directly be utilized to power wireless network sensors, wearable devices, smart buildings, internet of things, and so on.
Numerical Methods for Improving the Optimization Efficiency of Textured Surfaces
Authors: Geng Yu , Chen Li , Liu Heng , Qi Shemiao , Liu Yi , Zhou Rui , Zhang Rongfeng , Fan Bowen , Chen Yinsi , Li Yuan
Published: February 2024

As an emerging tribological technology, surface texturing has been widely studied and applied. More and more scholars have committed to the theoretical optimization of textures. To improve the optimization efficiency of textured surfaces, a multiscale method combining the finite cell method with Fischer-Burmeister-Newton-Schur, named as FCM-FBNS, the Fourier Amplitude Sensitivity Test (FAST) and genetic algorithm (GA) were combined in this paper. The proposed methods can calculate the first-order sensitivity indices of texturing parameters to the tribological characteristics efficiently and fastly. Results show that the texture density is the most crucial geometric parameter; the effects of the cell size are negligible. In addition, the effects of texturing parameters have a close relationship with operating conditions and the same parameters may have different influences on different static characteristics. The parameters with higher sensitivity indices can be defined as the key ones and the GA method was applied to improve the tribological performance of textured surfaces by optimizing these texturing parameters. The results achieved by optimizing only the key parameters are similar to that of optimizing all parameters, but the time can be saving up to 30 percent. The methods not only can reduce the optimization difficulty and time, but also provide a novel perspective to understand the optimization problem by quantifing the influence of input on the output.
Development of a Control System Architecture for a Self-Driving Humanoid, HART
Authors: Sohn Kiwon , Wisdom Jordaine , Sharpe Ethan , Robinson James , Kumar Rahul , Tatoglu Akin
Published: February 2024

The control system architecture development for a full-sized humanoid, HART (Human Assistive RoboT), is presented in this paper. HART has been designed and built by ART (Assistive Robot Team) at University of Hartford since 2017. With its unique design feature, which is kinematic re-scalability, HART can manipulate various control inputs of off-the-shelf vehicles with different sizes and structures in the market. In this study, the control system upgrade that can enable the robot to drive autonomously in trained environments is mainly described. For this, the way-point based navigation capability is built for HART using its trinocular camera system and CNN (Convolutional Neural Network) based terrain classifier. Next, HART’s sensor head, which is also redesigned for advancement of its perception capability, and end-effectors that are upgraded for more efficient manipulation of vehicles’ control inputs are introduced in this paper. Lastly, HART with the upgraded control system is tested and evaluated in human-centered environments.
Experimental Investigation of Vortex Shedding Patterns Behind Tapered Cylinder Pairs
Authors: Barbera Christopher , Hanson Matthew R. , Vaccaro John C. , Rooney David M.
Published: February 2024

An experimental wind tunnel study was undertaken to examine wake flow structures behind solitary finite tapered cylinders and behind pairs of finite tapered cylinders mounted on a flat ground plane perpendicular to a steady uniform upstream flow. Both a straight cylinder and a tapered cylinder were studied. The straight cylinder had an aspect ratio of 24, while the tapered cylinder had an aspect ratio of 32 and a taper ratio of 48. Data were collected at a Reynolds number of 4200 based on base diameter. The cylinder pairs could be oriented at any angle α from 0° to 90° with respect to the oncoming flow. Two center-to-center distances (based on the base diameters) were examined at each incidence angle. It was found that tapered cylinder pairs produced wake interference patterns that were more complex than straight cylinder pairs because the relative spacing of the cylinders increased with spanwise position as the local diameters diminished. Increasing the spacing between two tapered cylinders at α = 0° increased the clarity of spanwise vortex shedding cells. Similarly, increasing the spacing produced two distinct frequencies near the free end of the tapered pair at α = 30°, while for the analogous straight pair, there was only a single shedding frequency recorded over the entire span.
Engineering a Cost-Effective Solution for Measuring Sea Turtles’ Responses to Hypoxia
Authors: Essassi Fatima Elzahra , Liu Yucheng
Published: February 2024

This study aimed to design a case for an accelerometer, a pressure transducer, and a battery to be attached to sea turtles in order to determine their reactions in hypoxic environments. Hypoxia, caused by fertilizer runoff from the Mississippi River into the Gulf of Mexico, represents a significant challenge to the marine ecosystem in the waters. The case design was expected to be waterproof, buoyant, 3D printable, secure for all components, able to withstand pressures at a depth of 500 feet, and resistant to the corrosiveness of salt water, all while being cost-effective. The study resulted in the creation of a dome-shaped case manufactured using ABS plus. This case could be attached to a turtle’s shell using an epoxy adhesive and implemented a nitrile rubber O-ring to ensure waterproofness. In addition, stainless steel fasteners were used to protect it against saltwater corrosion. Despite meeting all the design requirements, the study made recommendations for a more failsafe design. This work provides a valuable contribution to the field of marine biology by offering a cost-effective and reliable solution for monitoring sea turtle responses to hypoxia in oxygen-deficient environments. The developed case meets all the requirements and can be a useful tool for ocean ecology research.
Introducing OpenPRA: A Web-Based Framework for Collaborative Probabilistic Risk Assessment
Authors: Earthperson Arjun , Aras Egemen M. , Farag Asmaa S. , Diaconeasa Mihai A.
Published: February 2024

Probabilistic Risk Assessment (PRA) tools are crucial in the nuclear, aerospace, maritime, and chemical industries. This paper presents OpenPRA, an innovative, open-source, web-based platform designed to address the limitations of current Probabilistic Risk Assessment (PRA) tools. OpenPRA offers a collaborative and flexible environment that supports a wide array of risk models and quantification engines, thereby enhancing the adaptability and efficiency of risk assessment processes. The platform offers unique features including support for various risk models such as event trees, fault trees, Markov chains, Bayesian networks, and error propagation models. It also allows users to choose from a variety of existing quantification engines, enabling them to tailor their risk assessment process to their specific needs. The paper discusses the design, development, and potential of OpenPRA to transform the field of PRA. It also delves into the platform’s technical architecture, technology stack, and the OpenPRA Model Exchange Format. The paper concludes by outlining the current development status of OpenPRA and laying out the foundation for future work.
Fluid-Structure Interaction Model of a Wind Turbine Blade
Authors: Raihan Gazi Abu , Chakravarty Uttam K.
Published: February 2024

The continuous development of the wind turbine blades in expanding size and flexibility introduces significant aeroelastic effects, which are brought on by the fluid-structure interaction (FSI). These effects can lead to aeroelastic instability issues including edgewise instability and flutter, which may be fatal to the wind turbine’s blades. Therefore, designing large wind turbine blades, especially offshore wind turbine blades requires accurate FSI modeling of the wind turbine. In this study, a full-scale NREL 5MW wind turbine blade is used for modeling the coupling FSI behavior for wind turbine blades for different operating conditions. An FEA (finite element analysis) model implemented in the ANSYS Static Structural module is used to calculate the structural response under the dynamic load applied by the wind, and a CFD (computational fluid dynamics) model developed in ANSYS FLUENT is used to compute the flow behaviors of the wind on the variable cross-section of the wind turbine blade. In this simulation, the aerodynamic loads estimated from CFD modeling are translated to FEA modeling for different angles of attacks (AOA) and the wind speed as load boundary conditions at the interface between CFD and FEA. Five different operating conditions are considered where the maximum deflection of the blade is found to be in the rated operating condition. According to pertinent design requirements, maximum tensile/compressive stresses and tip deflections in each situation are found to be within the material and structural limits.
A Finite Element Modeling Approach to Dwell Time Optimized Maraging 250 Parts for Wire Arc Directed Energy Deposition
Authors: Register Matthew A. , Betts J. Logan , Priddy Matthew W.
Published: February 2024

Wire arc directed energy deposition (WA-DED) is a metal based additive manufacturing (AM) process which utilizes an electric arc welding source to melt wire in a layer-by-layer manner Continuous thermal expansion and contraction, associated with uneven cyclic heating and cooling, leads to mechanical property heterogeneity as well as the formation of residual stresses and distortion in wire fed DED built parts. To control the interpass temperature during deposition, process parameters such as print strategy, heat input, and dwell time are often tested through an extensive experimental process parameter examination; however, finite element (FE) modeling provides the ability to simulate a variety of process parameters quickly, saving time and money. FE modeling has been shown to improve final part quality by predicting the thermal and structural response in as-built parts based on a variety of wire fed DED process parameters. This work will present a method for determining reasonable part quality metrics based on the variance in simulated cooling rates, max temperatures, and interpass temperatures as a function of heat input, print strategy, and dwell time. A design of experiments will be performed in Abaqus 2019 for a 10-layer thin wall build with differing heat inputs, print strategies, and fixed dwell times. The FE simulated cooling rates, interpass temperatures, and max temperatures will be compared with known martensite and austenite phase transition temperatures of maraging grade 250 (M250) to determine the optimum welding parameters needed to improve the part quality. Using this approach, a resultant part can be made with optimum process parameters with tailored control of the max temperature, cooling rate, and interpass temperature. This framework utilizes an array of FE simulations to provide a process-structure relationship necessary for determining the performance success of wire fed DED builds.
Design and Development of a Geometric Dimensioning and Tolerancing Course
Authors: Kocharian Tikran , Burns Jeremy , Manoharan Sanjivan
Published: February 2024

Many institutes of higher education overlook a very important tool namely, Geometric Dimensioning and Tolerancing (GD&T). GD&T is the symbolic language used in manufacturing to communicate the design, production, and quality control requirements. Over the years, several employers have voiced concerns about the students’ lack of knowledge in identifying and applying GD&T concepts in engineering drawings. This has resulted in the employers spending time and money to bring the students up to company standards. Lack of GD&T knowledge adversely affects the design and engineering department, production line, and quality control and assurance department, three critical areas in every manufacturing company. In addition, senior level students typically encounter issues during their design/capstone project where they are unable properly define tolerances subsequently affecting manufacturing and jeopardizing deadlines. As part of continuous improvement, the mechanical engineering program decided to create and offer the GD&T course as an elective for the first time in Fall 2022. The three-credit elective consisted of a total of 14 sessions, and the culminating experience of the course was an extensive project which they completed over time. The project had students working in teams of four, and the requirement was making a gib and slide assembly which consisted of no more than 5 pieces. The course evaluations were highly positive, and the students described it as intellectually stimulating where they were able to finally learn techniques that they could implement at their workplace. A major recommendation was to improve organization such that students can break the final product into two or three subassemblies that are due during the midterms. Given the global importance of GD&T, it is recommended that such a course be made a prerequisite for students engaged in senior design projects.
Inflow Conditions and the Mass Transfer Behavior of a Non-Newtonian Biofluid in Separated Flows
Authors: Hammad Khaled J.
Published: February 2024

Influence of inflow conditions and the rheological model selection on the flow and mass transfer behavior of human blood in a separated and reattached flow region is investigated. Newtonian and non-Newtonian hemorheological models that account for the yield stress and shear-thinning characteristics of blood are used. The conservation of mass, momentum, and species equations as well as the Herschel-Bulkley constitutive equation are solved numerically using a finite-difference scheme. A parametric study is performed to reveal the impact of flow restriction and rheological modelling on blood-borne oxygen exchange with the confining walls for uniform and fully-developed inflow conditions. The wall mass transfer rates within the separated and reattached regions display a strong dependency on the inflow conditions and the used hemorheological model. Newtonian and non-Newtonian models result in a peak wall mass transfer rate within the recirculation region. However, non-Newtonian models that account for the yield stress and shear-thinning effects predict a substantial, highly localized, drop in the wall mass transfer rates of oxygen, at the reattachment point. A substantial impact of the inflow conditions on the wall heat transfer rates is observed. Uniform inflow conditions, in general, result in higher peak wall mass transfer rates, that appear closer to the expansion plane, within the recirculation region, in comparison with fully-developed inflow conditions.
Effect of Surfactants on Surface Wettability via Measurement of Droplet Contact Angle and Interfacial Tension
Authors: Saxena Kritik , Chen Yun
Published: February 2024

Liquid appears to behave differently when in contact with a solid surface under certain conditions. Shape of a liquid droplet over a solid surface, for instance, can be influenced by various parameters, such as wetting properties, surface roughness, viscosity, surface tension, and external forces. The wetting properties, in particular, termed as wettability, is one of the key parameters that affects the shape of droplets on a surface. Furthermore, the wetting properties of a surface can influence other parameters that affect the droplet shape and flow, such as surface roughness, viscosity, and surface tension. Wettability itself can be influenced by several parameters that affect the droplet shape. Surfactants, for instance, are molecules that can change the wettability of the solid surface when added in the liquid. Studies have found that surfactants addition to liquids can change the contact angle of surface droplets, which leads to changes in droplet shape. Furthermore, studies have shown a relation of surfactant concentration and temperature on the spreading kinetics and the final shape of droplet. Most studies have focused on the static interfacial tension and contact angle measurement but very few have focused on dynamic measurements. The goal of this paper is to experimentally investigate the temporal impact of surfactants on the surface wettability and how it affects the shape of the droplet.

The reduction in interfacial tension due to the addition of surfactants can lead to an increase in wettability, leading to the droplet spreading out more on the surface. The effect of surfactants on interfacial tension and wettability is not straightforward and depends on various factors, including surfactant type and concentration, solid surface chemistry, and liquid properties. In this paper, droplet contact angle and interfacial tension will be measured via Droplet Shape Analyzer given different types of surfactant and concentration. Furthermore, the temporal evolution of the contact angle and interfacial tension will be investigated to understand the transport behavior of the surfactant molecules. The expected results here will advance the fundamental understanding of the droplet flow behavior on a surface with various surfactant type and concentrations.
Modeling and Investigation of Spatial Operation Stiffness in Robotic Milling Process Considering Bidirectional Weak-Stiffness of Robot-Workpiece System
Authors: Gu Qunfei , Liu Shun , Jin Sun
Published: February 2024

Complex cylindrical light alloy structural castings are widely used in the aerospace industry due to the simple forming process and complex internal cavity structure. Robots can make up for the shortcomings of traditional thin-walled cylindrical parts machining because of the low cost, high flexibility and good space accessibility. This will lead to difficulties in controlling the deformation caused by milling processing. A bidirectional weak stiffness machining system is proposed in this paper. The multi-body small deformation theory and the deformation superposition principle are used to provide the operational stiffness model. Compared with the conventional robot stiffness model, the proposed bidirectional weak stiffness operating stiffness model takes into account the stiffness characteristics of both the machining end and the workpiece end, which is more practical and comprehensive. At the same time, a milling vector stiffness performance index for thin-walled cylindrical parts robot machining is proposed, which can reflect the influence of the system stiffness characteristics on the machining wall thickness accuracy more intuitively. The stiffness characteristics of the machining system are studied by finite element analysis, and the applicability of the proposed stiffness model and stiffness index is verified. This study can guide the subsequent robot machining trajectory planning and process parameter optimization.
Additive Manufacturing for Investment Casting: Economic Comparison Between Digital Light Processing and Wax Moulding
Authors: Mandolini Marco , Sartini Mikhailo , Favi Claudio , Germani Michele
Published: February 2024

Additive manufacturing (AM) is rapidly gaining popularity and is used to create finished goods or moulds (rapid tooling). AM is also frequently employed for generating patterns and moulds, often in conjunction with casting to produce massive metal components to overcome the drawbacks of casting techniques. Compared to wax injection, Rapid Investment Casting (RIC), which is the application of AM in Investment Casting, may guarantee a significant reduction in lead time. Given the innovative nature of this technology, the scientific literature lacks in providing techno-economic evaluations concerning adopting Digital Light Processing (DLP) technologies for RIC. This study examines the techno-economic implications of using additive manufacturing (i.e., DLP) to create wax or resin models. The article provides a decision-making tool to help stakeholders assess AM’s benefits for manufacturing wax patterns instead of wax injection. Analytical cost models are provided for estimating the manufacturing time and cost of the compared technologies. The study considered two production scenarios distinguished by the machine load factor for DLP (10% and 50%). Mainly, the technology comparisons are based on production costs and times. The study takes into account parts from the fashion and mechanical sectors. Results indicate that AM is faster and cheaper than injection moulding for production batches up to 10E2 (as an order of magnitude) for small-size components and 10E1 for large parts. This outcome derives from the avoided cost for the moulds required for the injection process. Regarding cost and time, the batch cross-over points decrease when the dimensions of components are increased.
Opportunities and Challenges in Biomimetic Robotic Simulation for In Vitro Testing of Chewable Drugs
Authors: Chen Bangxiang , Dhupia Jaspreet S. , Morgenstern Marco P. , Zhang Feng , Xu Weiliang
Published: February 2024

Robotic biomimicking devices are a novel approach to simulate in vivo processes such that the investigation of bioprocesses is more convenient, and the knowledge gained can be used to promote technologies to improve the quality of life. Chewing is one of the most complex bioprocesses, where the chewed object is comminuted, mixed with saliva, digested by enzymes, and eventually forms into a swallowable bolus. Researchers have been working for years toward in vitro chewing simulators to analyze oral processing and food properties, but little effort has been devoted to the analysis of drugs. Chewable drugs refer to an oral dosage form intended to be chewed by the users rather than swallowed as a whole. Chewing releases the pharmaceutical ingredients directly into the oral cavity and achieves the comminution of the dosage form to ease the swallow and digestion, resulting in a faster onset of the pharmaceutical ingredients. This paper discusses the demands and requirements of a chewing simulator to perform in vitro tests on chewable drugs. The state of the art of chewing simulators is reviewed, followed by the demands and requirements of biomimetic chewing on testing drugs, and the potential and conceptual improvements of an existing chewing simulator for drug testing is also covered.
Advancements in Assistive Devices for Para-Kayaking Sports
Authors: Walck Christine , Huayamave Victor , Garcia Monica , Diaz-Portela Paola , Hernandez Betsabe , Ray Erin , Le Din , Palmer James , Randall Weston
Published: February 2024

While mobility impairments resulting from spinal cord injuries are oftentimes permanent, the quality of life for these patients can be improved through para-sports, which use adaptive and assistive equipment. This study uses a novel assistive device design where the paddle’s stroke is controlled by a slotted arc which allows the user to mimic the motion path of a healthy forward stroke. The paddle stroke motion path was tested in SolidWorks using rigid body dynamics by overlaying the paddle’s motion path onto known paths from a healthy elite kayaker or what is thought to be a standard paddle path. The results showed that the motion path was similar in the vertical and frontal planes. These results were further investigated using two trials observed in a motion capture system with a 21-year-old male subject. The trials consisted of six forward strokes in a 1) controlled (without the device), and 2) experimental (with the device) setting. Shoulder, elbow, and wrist mechanics were analyzed using inverse kinematics statistical comparisons. Results from this study could help provide guidance for the future development of assistive technology for para-kayaking sports.
Oxide Growth Predictions During an Advanced Test Reactor (ATR) Powered Axial Locator Mechanism (PALM) Cycle
Authors: Barney Jason W. , Choe Dong O. , Kilby Seth M.
Published: February 2024

The Mini-Plate for Advanced Test Reactor (MP-ATR) experiment, designed for testing plate-type fuel, will be irradiated in the Advanced Test Reactor (ATR) at Idaho National Laboratory. This paper discusses the thermal analysis that was performed on the MP-ATR experiment, with the Pawel oxide growth correlation being applied to accurately predict oxide growth under powered axial locator mechanism (PALM) cycle conditions. These oxide growth predictions were attained through a slow-growth transient analysis with 24-hour time steps. The MP-ATR experiment will be irradiated for a total of 10 days during a high-power PALM cycle.

To date, oxide growth predictions for ATR drop-in experiments have mainly focused on normal ATR power cycles. Oxide growth predictions can carry a high level of uncertainty when high heat flux and surface temperatures with some correlations are involved. This study takes a quantitative approach to verifying and validating the existing correlations, identifying gaps, and providing recommendations to improve the correlations so as to enable better oxide growth predictions under ATR PALM cycle conditions.
Facilitating Water Droplet Removal From Wind Turbine Blades Using Surface Wettability Gradients
Authors: Bertelsen Jacob M. , Sommers Andrew D.
Published: February 2024

A new method is proposed to mitigate ice accretions on wind turbine blades via the creation of a microstructural gradient surface geometry that facilitates spontaneous water droplet motion along the surface. The wettability gradients are formed by laser etching 35μm wide by 35μm deep channels into aluminum to form a surface with a gradually increasing solid area fraction which results in one end of the gradient surface being superhydrophobic and the other end being hydrophilic. Different design permutations are proposed and systematically assessed on the merits of their performance with respect to a baseline flat homogeneous surface and with respect to each other. An analytical model is also derived based on a balance of hysteresis and drag forces to predict the critical airspeed necessary for droplet movement as a function of the droplet size and the intrinsic contact angle of the surface. To date, experimentation has validated the model for the baseline surface and has also demonstrated that, in certain cases, up to 70% lower critical airspeeds are required to initiate droplet motion on these microstructured surfaces as opposed to the homogeneous baseline samples.
Combustor Wall Heat Transfer and Emission Characteristics of Premixed Ammonia/Methane/Air Blends in a Swirl Stabilized Gas Turbine Combustor
Authors: Das Chaudhury Meghna , Sahoo Abinash , Ekkad Srinath V. , Narayanaswamy Venkateswaran
Published: February 2024

Energy demand and carbon emission levels are increasing globally at an alarming rate leading to growing interest worldwide towards renewable and clean energy resources. In this context, the present research work investigated the combustor wall heat transfer and emission characteristics of Ammonia/Methane blends as a low carbon, clean energy resource with application to gas turbine power generation. Different volume % of Ammonia/Methane (0–50 % Ammonia) blends were considered at an equivalence ratio = 0.6 and at Reynolds number ∼50000 with a 10% Methane pilot which was used to ignite and stabilize the main flame. A quartz, atmospheric pressure, swirl stabilized, can combustor (swirl number∼0.8) rig equipped with an industrial burner was used for the experimental work. The same set-up had been previously used for studying hydrocarbon based fuels and the aim here was to study the possibility of using a cleaner gas turbine fuel by keeping the essential system hardware the same. Infrared Thermography technique was employed for estimating the wall temperatures and heat flux along the optical combustor wall and, this wall temperature was then used in the simulation work using CONVERGE CFD software incorporating the RANS RNG k-ϵ and SAGE techniques for predicting NOX and carbon emission levels and for studying the overall flame. Additionally, a highspeed camera was also used to qualitatively study the flame characteristics and flame stability. Upon comparing the results with a pure Methane-Air case, reduction in heat flux ranging between 30 to 40 % was observed for various Ammonia/Methane cases. Differences in NOX emission values between adiabatic and non-adiabatic cases were also observed along with significant reduction in carbon emissions by a maximum of 62%.