bluuebunny/crossref_metadata_2025 huggingface dataset:
Vascular Model of Liver Fibrosis
Authors: Torres Rojas Aimee M. , Lorente Sylvie
Published: February 2024

The liver has a very peculiar blood circulatory system composed of two blood supply vascular trees (the hepatic artery and portal venous networks), microcirculation through small functional units called lobules, and a blood drainage vascular tree (the hepatic vein network). In the healthy liver, flow resistance at the microcirculation level is very low and the portal pressure is almost the same as the lobules pressure. On the other hand, vasculature changes due to fibrosis — located predominantly at the lobules level — lead to a marked increase in resistance to flow causing an increase in portal pressure (portal hypertension). Here, a rigid model of the entire liver vasculature is built, where hepatic networks are considered as tree-like fluidic networks and lobules as a porous medium. The model can provide the blood flow and pressure within their healthy physiological ranges at all points of the vasculature. To simulate liver fibrosis, the portal hypertension it causes is reproduced. The high portal pressure values reported for fibrotic patients are used to calculate the necessary lobules permeability resulting in these pressure values at the inlet of the lobules. The decrease in the permeability of the fibrotic lobules causes a redistribution of flow between the two blood supply networks. The alterations of microcirculation due to fibrosis are also analyzed: increases in blood flow through the non-fibrotic lobules and decreases in blood flow through the fibrotic ones are observed, relative to blood flow through the lobules in a healthy liver.
Review of the Reliability and Feasibility of Existing Databases for Automated Vehicle Safety
Authors: Kim Eun Young , Wijesekera Duminda , Kan Cing-Dao , Park Chung-Kyu
Published: February 2024

The objective of this study is to use the existing databases on road information, crash information, and automated vehicle information towards designing accident avoidance mechanisms for automated vehicles. We use two main methods. The first is text clustering analysis that is used for grouping data from the existing safety databases into different categories assigned automatically. The second is using text classification analysis that is used to identify categories in two different datasets: the data elements and the data frames from the SAE J2735 V2X Communication Message Set Dictionary.

Based on outputs of two analysis methods, an assessment was performed by comparing the categories from the existing databases and from the V2X dictionary. Firstly, the outputs of the text clustering analysis demonstrated data diversity with various categories evenly weighted. On the other hand, the outputs of the text classification analysis showed that one category with respect to automated vehicle driving is highly concentrated. Thus, an assumption can be drawn that the existing databases are valid to support a communication application of automated vehicles. Additionally, keywords used for identifying the categories in the text clustering analysis indicate that they are similar with words from the data elements and data frames in the V2X dictionary. It presumes that data attributes are comparable to utilize the existing database to automated vehicles. This research shows that the use of the existing safety databases would be reliable and feasible for automated vehicles with evidence of data diversity and data similarity.
Structural Rigidity Analysis of Inflatable Wing Designs Constructed With High-Performance Fabric Membranes
Authors: Song Yuyang , Cavallaro Paul V. , Sadegh Ali M.
Published: February 2024

This research investigates competing design concepts supporting the development of a large-scale inflatable aerial wing capable of providing wind energy harvesting, telecommunications, and meteorology tracking. High Performance Fabric (HPF) membrane designs coupled with inflatable technologies are utilized because of their combined structural advantages such as lightweight; high strengths; flexibility; elastic recovery from overloading events including wind gusts; high packing efficiencies; etc. A comparative study is presented for two different inflatable structures; one is the baffled inflatable airfoil, where we investigate a different number of internal baffles bonded within a single airfoil envelope, normally shaped with a NACA4315 profile. The other is a drop-stitch inflatable airfoil, also known as 3-D woven fabric. By using the same high-stiffness fabric materials, the structural rigidities, bending load capacities and weights of these two membrane airfoil designs are compared through finite element analysis (FEA) modeling. It is shown that the inflatable baffled airfoil design exhibits greater stiffness-to-weight ratios compared to the drop-stitch inflatable airfoil design. The number of baffles within the baffled airfoil plays a significant role for: (1) mitigating peel stresses in the bonds between the skins and baffles, increasing the load carrying capacities prior to wrinkling and (3) increasing the overall bending stiffness. This research identifies the advantages and limitations of competing inflatable airfoil concepts and serves to increase the knowledge base for future inflatable structures and their applications.
Experimental Research on Photo-Induced PLZT-Based Electrostatic Micro Gripper
Authors: Lv Zhen , Liu Zhicheng , Tang Yujuan , Wang Xinjie
Published: February 2024

Photo-induced actuators have arisen as a particularly attractive alternative among different actuators in these days. In contrast to traditional actuation mechanism (e.g., piezoelectric, electromagnetic, electrostatic effects), photo-induced actuators provide a clean, contactless actuation mechanism and require no external electrical power supply. In this paper, we report a strategy to realize rapid photo-induced actuation using a composite actuation mechanism, which combines photoelectric effect and electrostatic actuation mechanism. Photo-induced PLZT-based electrostatic actuator is then proposed towards micro gripper. Due to the nonlinear variation of electrostatic force, there is the electrostatic pull-in phenomenon enabling the gripper with rapid grabbing action. Micro grippers with sandwich-like multilayer structure arms are fabricated using a simplified photolithography process. A series of experiments are conducted to characterize the fundamental operation and performance of our gripper. The experimental results show that a higher light intensity leads to a more efficient grabbing action. For the light intensity of 300 mW/cm2, the grabbing action can be achieved about 1.5 s, while 10 s for the light intensity of 100 mW/cm2. The ability for grabbing objects of different materials is further investigated to demonstrate the versatility of the gripper. In summary, the developed gripper is rapidly and reliably driven by UV light, easy to fabricate, providing a great potential to facilitate the current research in photo-induced actuation applications.
Data-Informed Design Process for SME: A Streamlined Validation and Prediction Approach for Customer Perception of Innovative Material Prototypes
Authors: Quattelbaum Bastian , Steinem Christine , Neumann Marc
Published: February 2024

Designing innovative materials can be difficult and time-consuming. Small and medium-sized companies in particular struggle to validate their designs against customer opinions.

This paper presents an approach to validate customer perception with human senses of textile material prototypes and to predict this perception. The two most important factors for the customer’s product experience are the visual and the tactile sense. With haptics, a conscious sensation is realized when a customer strikes or touches the product. In times of short time-to-market goals and tight budgets, it is very difficult to realize this interaction with enough people.

A methodology is presented that displays the surface properties of designed materials only via a digital channel and is purely visually perceptible. The first step to product success is to gain insights into how customers perceive the newly designed products through digital channels. Furthermore, predicting the customer’s judgment on surface attributes as early as the design-prototype phase would further help to overcome the given limitations. Therefore, this paper examines whether and how specific surface measurements correlate with customer perceptions of different surface attributes. This offers the possibility to control customer-oriented design activities.

Finally, all collected data should be integrated into a data-informed design process to make informed product design decisions based on collected data. This goal is achieved as the methodology introduced makes the required data easily accessible and analyzable.
Global Modeling: Scaling Up Machine Learning Models for Predictive Maintenance
Authors: Morgenthal Allyson , Jain Akhilesh , Aman Michael , Gullikson Kevin , Egboga Nkem , Horton Marcus
Published: February 2024

Machine learning models based on Normal Behavior Modeling (NBM) have demonstrated effective anomaly detection for various equipment on Oil & Gas platforms such as compressors, pumps, separators, and level control valves. The NBM modeling approach uses autoencoder deep neural network architecture to learn the behavior of the equipment during normal operating periods and generates alerts when it encounters new or abnormal behavior. The autoencoder architecture outputs a risk score aggregated over the residuals from all input features. A Sequential Probability Ratio Test (SPRT) is performed on the risk score to determine abnormal regimes during operation to raise alerts. This approach has been very successful in identifying abnormal behavior with good performance on recall, precision, and lead time. However, scaling up these models to large volumes remains a challenge as an individual model is required for each piece of equipment of an asset type and requires years of data from normal operation for training. Our objective is to modify the original NBM workflow to create global models that generalize for all equipment of the same asset type and can be deployed across sites and platforms. A global modeling approach is applicable for equipment of the same asset type, having the same sensors, a consistent physical correlation between these sensors, and sufficient data during normal operation. Once these criteria are established for a set of equipment, a global model is created by training the model on a combined training set from the set of equipment. The combined training data is created by removing data with any downtime, failure events, and operational issues. A portion of this combined data is set aside for validation. Once the model is trained, new data is used for making predictions. We applied this workflow successfully on Uninterrupted Power Supply (UPS) units and Dry Gas Seals (DGS) for gas turbine compressors. This work is currently being expanded to Subsea Power and Communication Units (SPCUs) and Annulus Wells. The proposed approach allows for the quick deployment of a single global anomaly detection model to the entire asset type instead of having to build equipment-specific models. Global models are exposed to a more varied training dataset allowing for less retraining during operational shifts and can be deployed for equipment with no historical data.
Investigation of Annular Gas Seal Performance With Combined Cavity Patterns Using Computational Fluid Dynamics
Authors: Yildiz Saltuk , Untaroiu Alexandrina
Published: February 2024

Annular gas seals are crucial components in turbomachinery applications since they reduce leakage flow from high-pressure to low-pressure sections. However, the fluid-induced rotor instabilities that may be governed by these components result in reduced efficiency and even failure in rotating machines. Thus, the proper selection and design of annular seals are critical to ensuring the stability and reliability of rotating machinery. Minimization of leakage rate while improving rotordynamic performance can be achieved by using proper cavity geometries. In this aspect, this work investigates leakage and rotordynamic characteristics of combined hole-pattern annular gas seals composed of circular and hexagonal patterns using 3D computational fluid dynamics (CFD). In literature, annular gas seals with circular and hexagonal cavities are investigated depending on shape of the patterns. According to previous research, the rotordynamic and leakage performance can be improved with the parameterization-based design optimization of the cavity shapes such as hole depth, diameter, distancing etc. Most of the existing studies investigate the performance of annular gas seals using bulk-flow analysis. Although bulk-flow model is more efficient in terms of computation time, CFD is a more proper tool to analyze patterned seals which have geometric complexity in terms of accuracy. The main reason is that the 3D CFD model enables to perform more realistic assumptions which results in more accurate outputs especially for complex designs in comparison to bulk-flow analysis. The performance of proposed combined-pattern seals is investigated comparing with the performance of existing industrial regular circular and hexagonal (i.e., honeycomb) patterned annular gas seals. Computational models are verified through existing experimental data for the circular hole-pattern seal which is selected as the baseline model. This investigation performs optimal selection of combined-pattern cavity geometry selected from the pool of configurations considered and provides an insight for further optimization efforts on patterned annular gas seals.
Automatic Evaluation of Inline Surface Topology Measurement Data of Material Jetted Metal Parts for Closed Loop Control
Authors: Rehekampff Christoph , Huber Markus , Kirchebner Benedikt , Irlinger Franz , Lueth Tim C.
Published: February 2024

Additive Manufacturing is becoming increasingly important, which is demonstrated by its rapidly growing market volume. For processing metals, mainly powder based methods such as Powder Bed Fusion (e.g. Selective Laser Melting, Electron Beam Melting) or Direct Energy Deposition (e.g. Laser Metal Deposition) are used. The drawback of these methods is the raw material: Its price per weight is much higher than the raw material price, since powders with a narrow particle size distribution and spherical shape are required for these processes. Furthermore, the handling of the metal powder requires specific safety precautions due to the high risk of fire and negative health implications.

Material Jetting is an additive manufacturing method where the build material is deposited onto a platform as single droplets. The raw material can have almost any shape, as it is melted in a crucible. For printing a part, either the build platform or the printhead are moved along a predefined path while droplets are ejected to generate the desired part geometry. For polymers, there are multiple commercially available systems that operate this way. For metal printing however, the systems are still in an early stage of development due to the challenges of the process. Especially generating droplets of a certain size and depositing them at a precise position next to each other is challenging.

In this work, a method for a closed-loop layer height control based on inline surface measurement of the printed layers is described. For this, the determined measurement data needs to be automatically processed and compared to the desired layer height. An approach to compensate deviations by individually varying the size of single droplets is described.
Studying Reultrasonication Effects on the Suspension Stability of Stored Nanofuels Based on Optical Measurements
Authors: Mollick Rahat , Nagarkar Nitin , Loskill Ford , Ratner Albert
Published: February 2024

Suspensions of pure energetic nanomaterials in a liquid fuel, commonly termed as nanofuels, are desirable for their vastly different combustion properties compared to base fuels. Large scale, as well as lab scale, storage of such nanofuels is very challenging due to settling that occurs in these fuels over time. Various effects including high specific surface area (SSA) and high surface energy of nanoparticles facilitate nanomaterial agglomeration. The gradual agglomeration of the initially dispersed nanoparticles promotes their separation from the base fuel, followed by gravitational settling to the bottom due to the agglomerates growing in size. Reultrasonication of these stored colloidal suspensions has been taken to be the effective, and thus primarily employed, method to redisperse the settled nanomaterials in the base fuel. However, the settling behavior of these reultrasonicated samples can be significantly different from that of the initially prepared samples. This effect can introduce errors in determining important parameters such as burning rate, flame standoff ratio (FSR), and thus contributes to overall uncertainty in experimental results. To address this particular concern, the present research deploys a non-contact, non-invasive, quantitative, and simple experimental configuration to analyze suspension behavior. Soy Biodiesel, a promising renewable fuel was chosen as the base fuel and Acetylene Black was selected as the nanomaterial for the suspensions in this experimental study. Acetylene Black (AB) is both inexpensive and environmentally benign and has been previously employed as a carbon-based nanomaterial fuel additive. Surfactants are commonly used to help disperse nanomaterials, and they are included in this test protocol as well. To investigate the effect of such surfactants on the settling behavior, Span 80 (SP 80), a non-ionic surfactant with a Hydrophilic-lipophilic balance (HLB) value of 4.3, is tested and the effect of its concentration on the settling time of the samples is also recorded.
Hydrocarbon Condensation Heat Transfer Enhancement Using Silica Nanosprings and Slippery Liquid-Infused Porous Surfaces (SLIPS)
Authors: Vuth Adam Y. , Dillman Andrew R. , Conway Daniel F. , Chamberlin Joseph P. , Corti Giancarlo , Sommers Andrew D.
Published: February 2024

In this work, slippery liquid-infused porous surfaces (SLIPS) and fluorosilane coatings are applied to amorphous silica nanospring (SN) structures grown on the surface of aluminum tubes to promote dropwise condensation and to enhance heat transfer performance during methanol condensation. Initially, the fluorosilane coating (i.e. heptadecafluoro-1,1,2,2-tetrahydrodecyltrimeth oxysilane) and SLIPS were applied to flat aluminum samples containing SNs to measure coating performance. After determining the optimal coating parameters, round aluminum tubes were prepared using the same coating parameters. These tubes were then placed in a custom-built environmental chamber and subjected to saturated methanol vapor where Tsat = 21–22°C. The performance of the coating was quantified using static and advancing contact angle (CA) measurements and scanning electron microscope (SEM) imaging. Heat transfer data were collected at different subcooling degrees and cooling water volumetric flow rates to see how the condensation behavior changed with different operating conditions. Preliminary data with methanol have shown that SN mats functionalized with the fluorosilane and SLIPS coating have CAH values as low as 5.71°. Similarly, the CAH of SNs functionalized with the fluorosilane alone (no SLIPS) was shown to decrease from 50.5° to 28.0° following three repeated liquid immersion-based coatings in the 17F silane. Current work is focused on measuring the heat transfer performance of these SN coated aluminum tubes functionalized with the SLIPS and fluorosilane coatings to see what combination leads to the best heat transfer performance. This analysis should provide additional insight into how to improve condensation heat transfer performance of low-surface tension fluids like methanol and also highlight the use of SLIPS and fluorosilane coatings in these types of applications.
Determining the Physical Components of Resistance Acting on a Hydrofoil
Authors: Chernyshev Lev , Kabaliuk Natalia , Jermy Mark , Corkery Simon , Bernasconi Daniel
Published: February 2024

Hydrofoils have become a popular design addition to different kinds of waterborne vessels, particularly yachts and race boats. A prime example of this is the Americas Cup yacht regatta, where hydrofoils are now a mainstay of boat architecture. Hydrofoils permit vessels to lift their hulls above the water surface through the generation of lift. When in this “foiling” regime, the drag forces on the hull are drastically lower, permitting greater sailing speed. Predicting hydrodynamic forces produced from hydrofoils on race yachts remains challenging, due to a wide operating regime and complex hydrodynamical phenomena. The purpose of this study was to investigate methods of decomposing the total drag force of a hydrofoil from computational fluid dynamics (CFD) simulations into its physical components. A rectangular NACA4412 was simulated fully submerged at a depth of one chord. Viscous flow was simulated with the k-ω SST turbulence model in steady state; and the volume-of-fluid (VOF) model was used to capture free surface effects. Chord Froude numbers of 0.5, 1, 2 and 4 were investigated, corresponding to Reynolds numbers of 2.57 × 105, 5.15 × 105, 1.03 × 106 and 2.06 × 106. Force decomposition was performed using wave pattern analysis, Trefftz plane analysis and viscous wake surveys. These yielded the wave-pattern, induced, and viscous drag components respectively. Wave drag was seen to decrease with Froude number, while the induced drag increased. The sum of viscous and wave drag closely approximated the total drag computed using surface integration, supporting the Froude decomposition of drag force. Induced drag was seen to interact with the other drag components and became the dominant component at Froude numbers above unity.
Hydro-Structural Design Exploration of Floating Platform for Offshore Energy Systems
Authors: Cain Chandler S. , Lee Yong Hoon
Published: February 2024

This paper presents a comprehensive study on the hydro-structural design exploration of floating platforms for offshore energy systems. The study aims to develop a novel design method that optimizes the structure of the platform for stable dynamic responses to ocean waves, ensuring that the motion of the platform remains within acceptable acceleration ranges in all six degrees of freedom, while ensuring satisfactory of geometrical constraints. The study delves into the free-form design of the outer columns of the floating platform beyond conventional pre-defined shapes to enhance the overall performance of the system. The design utilizes a parameterization based on free-form spline interpolation for the outer shape of the hull and fixed-shaped pontoons to connect to the central structure where the energy-generating device (e.g. wind turbine) is installed. The study employs hydrostatic, hydrodynamic, and time-domain structural dynamic simulations within a monolithic multidisciplinary design optimization formulation to evaluate the overall dynamic responses of floating platforms. Overall, this study provides valuable insights into the hydro-structural design of the floating platforms for offshore energy systems. The optimal shape of the outer column suggests that the concave design enhances dynamic performance by effectively reducing the span-wise footprint of the platform. The results offer design considerations for floating platform hull developers to create robust designs that can withstand harsh metocean conditions. The findings obtained from the optimization solutions suggest the need for advanced design exploration and shape optimization of the floating platform hull, including the pontoons and the central structure for optimal performance. The study also suggests employing manufacturability constraints and wave loadings in all possible directions to reflect real-world operating conditions of floating platforms.
A Comparison of Motion Planning Methods for Autonomous Ground Vehicle Exploration and Search
Authors: Khairnar Apoorva , Sivashangaran Shathushan , Eskandarian Azim
Published: February 2024

Navigation of an Autonomous Ground Vehicle (AGV) is a major challenge for complex applications such as exploration of uncharted terrain, search and rescue (SAR) missions, and military assignments. An AGV is subjected to numerous uncertainties such as unexpected obstacles, uneven terrain, and hazardous regions. Motion planning algorithms are responsible for the safe, quick, and energy-efficient autonomous navigation of an AGV in the surrounding environment. In this paper, we compare the performances of conventional motion planning algorithms that include A*, RRT, RRT*, pRRT, and APF for exploration and search tasks. The comparison is carried out in a realistic environment simulated in AutoVRL, a high-fidelity simulator built using open-source tools. This study assumes the presence of a high-level planner that provides the algorithms with environmental information, and application-specific goal positions. The algorithms are compared on the basis of computation time, and efficiency of the generated trajectories, to navigate to goal positions determined by the high-level planner. The results indicate that A* and pRRT perform significantly better than the other tested algorithms, yielding the most efficient trajectories with the least computation time.
Higher Order Sensitivity Analysis for Elastic Problems Using the Multidual Finite Element Method
Authors: Avila David , Montoya Arturo , Millwater Harry
Published: February 2024

In this research study, the multidual finite element method (ZFEM) was assessed for its accuracy and efficiency in computing second-order derivatives of output variables with respect to input variables in elastic problems. The accuracy of multidual ZFEM in elastic problems was examined by comparing the multi-order derivatives of displacement and stress fields with respect to material, geometric, and loading parameters in a problem involving a thick-walled cylinder subjected to internal pressure. The findings revealed that higher-order derivatives with respect to material parameters exhibited greater accuracy compared to those associated with geometry, as measured by the L2 norm. This trend was also observed for mixed derivatives involving various types of input parameters, such as shape and material parameters. Overall, the multidual ZFEM demonstrated the ability to accurately compute higher order derivatives in elastic problems, regardless of the type of input parameter, within a single analysis. This stands in contrast to conventional numerical techniques like Finite Difference, which necessitate multiple analyses to determine the appropriate step size for perturbing the input variable. The higher-order derivatives provided by multidual ZFEM hold significant utility across different engineering domains, including uncertainty quantification.
A Reduced Order Model for Estimation of Fractional Flow Reserve (FFR) in Coronary Artery Disease: Assessing the Impact of Side Branches
Authors: Vila Arber , Ahmed Mohammad , Taebi Amirtaha , Dong Pengfei , Gu Linxia , Thibbotuwawa Gamage Peshala
Published: February 2024

Millions of people worldwide are affected by coronary artery disease (CAD), which is a major cause of morbidity and mortality. To plan effective treatment and stratify risk, it is crucial to evaluate the severity of CAD. Fractional flow reserve (FFR) is a vital parameter used in clinical practice to evaluate CAD severity, which measures the ratio of mean distal coronary pressure to mean aortic pressure during hyperemic conditions. Non-invasive methods for estimating FFR have gained popularity, but computational fluid dynamics (CFD), which is often used, is impractical for routine clinical use due to the time and resources required. To address this issue, a reduced order model is proposed that effectively captures hyperemic conditions and considers the impact of side branch flow on FFR. The model approximates artery sections and branches as Windkessel models and simulates the hyperemic condition by varying microvascular resistance. The study’s preliminary results reveal that the proposed model accurately captures hyperemic conditions and side branch flow’s impact on FFR, providing crucial insights for clinical decision-making. This approach presents a promising way to evaluate CAD severity more efficiently and accurately using non-invasive methods, paving the way for non-invasive assessment of CAD severity. Further studies are necessary to validate the model’s accuracy and potential for clinical translation.
Prediction of Pressure Distribution in a Magnetorheological Squeeze Film Damper With Short Bearing Approximation Under Slip Conditions
Authors: Gómez Juan R. , Escandón Juan P. , Vargas René O. , Jimenez Edson M.
Published: February 2024

The present work analyzes the pressure distribution in a magnetorheological squeeze film damper which is used to attenuate mechanical vibrations in rotating systems. In this study, the mathematical model that describes the movement of the fluid is formed by the continuity equation, the momentum equation, the Bingham rheological model and the slip boundary conditions on the walls. Here, Reynolds equation is derived to determine the pressure distribution in the system, assuming a short bearing approximation. Additionally, this study assumes that the velocity of the fluid at the top wall corresponds to the angular velocity of the journal, and the height of the channel depends on the relationship between the bearing clearance and the eccentricity. In the results, velocity profiles and pressure distribution are presented as a function of the dimensionless parameters arising from the dimensionless mathematical model. These parameters are the viscosity ratio, the yield stress, the hydrodynamic slip and the channel height associated with the angular movement of the journal. Therefore, the theoretical results are intended as a contribution to the understanding of magnetorheological squeeze film dampers for applications in rotating systems such as turbines, pumps, aeronautical engines, gyroscopes, among others.
Dynamics of Two Parallel Inverted Flags in Axial Flow
Authors: Wang Shaoguang , Legrand Mathias , Païdoussis Michael P.
Published: February 2024

Two identical thin flexible plates, referred to as “inverted flags”, in a side-by-side arrangement are investigated theoretically. A linear model is developed to predict the onset of instability. This linear model elucidates the mechanism of instability and the sensitivity of the critical flow velocity to the gap between the two flags. The dynamics of a single flag has been studied massively, but the coupling of multiple flags is seldom reported. The Euler-Bernoulli beam theory and incompressible potential flow theory are adopted in the model. The Galerkin method and Fourier transform technique are used to solve flag displacements and fluid potentials, respectively. As the flow velocity is increased, the first mode becomes unstable via a pitchfork bifurcation. At higher flow velocities, higher modes lose stability via Hopf bifurcations. Out-of-phase and in-phase motions are predicted for the two flags. It is found that the critical velocity is independent of the flag gap-to-length ratio when it is approximately greater than 1. When the ratio is reduced, the critical velocity becomes smaller. When the ratio is extremely small, flutter occurs to the first mode before static divergence.
Temperature Field Around a Space Vehicle Descending in Mars Atmosphere
Authors: Rhisat Fahad Nizam , Molki Majid
Published: February 2024

Descending a space vehicle in Mars’s atmosphere is challenging. The main challenge is the unusual heating while the descending spacecraft moves at hypersonic speeds. This paper presents a computational model of a hypersonic flow around a spacecraft descending into Mars’s atmosphere. The work focuses on aerodynamic heating and the thermal field around the vehicle at hypersonic speeds. The mathematical model considers a three-dimensional, compressible hypersonic flow with bow shock waves. OpenFOAM, an open-source CFD code, solves the governing equations of mass, momentum, and energy using a finite-volume approach. The solver is a density-based, shock-capturing approach based on the central-upwind schemes of Kurganov and Tadmor. In this investigation, the turbulence model is Spalart-Allmaras. A clustered mesh resolves the super-fine boundary layer near the walls where large gradients dominate. This study focuses on the range of hypersonic Mach numbers from 5 to 27. A grid refinement study and comparison with the analytical solution verifies the solution approach and validates the results. This work aims to present the temperature field on and about the vehicle. The paper presents regions of subsonic and supersonic flows over the vehicle, surface temperature, and the contribution of aerodynamic heating.
Novel Lockable Passive Joints for Joint Locking-Based Reconfigurable Mechanisms
Authors: Rosyid Abdur , El-Khasawneh Bashar
Published: February 2024

This paper presents a novel design of lockable passive prismatic, revolute, universal, and spherical joints that can be used in a joint locking-based reconfigurable mechanism. The proposed lockable joints offer several advantages, including 1) modularity, 2) small locking force/torque, 3) low-power active trigger, 4) no-slip, and 5) simplicity. All the lockable passive joints proposed in this work provide locking at one or multiple discrete positions, considering that it is the requirement. The modular design, in particular, provides a cost-effective solution for the manufacturing and maintenance of the joints. Designed to have one or more discrete locking positions, the proposed lockable joints have a self-aligning capability that increases the reliability of the locking action. The locking action can be triggered by a low-cost, low-power, short-stroke binary piston such as a solenoid. While the trigger only requires small power, the locking action provides strong locking provided by mechanical locking.
Asymmetrical Auxetic Structures for Impact Force Mitigation
Authors: Yang Chulho , Lee Dongchan , Worwag Ben
Published: February 2024

This research is aimed at proposing an enhanced re-entrant hexagonal structure and examining its auxetic behavior in compressive or tensile load conditions. Auxetic materials, also known as materials with negative Poisson’s ratio (NPR), have been designed and fabricated for diverse applications that utilized normal materials which follow Hooke’s law but still show the NPR properties. One of the major applications is body protection pads that are comfortable to wear and effective in protecting body parts by reducing impact force and preventing injuries in high-risk individuals such as elderly people, industry workers, law enforcement and military personnel, and sports players. Another application is soft robotics for which the auxetic structures are used as sensors and actuators while protecting the wearer in the event of falling or collision. It is important to develop a new garment that best combines each individual’s requirements for wearing comfort, ease of fitting, ensured protection, and cost-effectiveness. The garment would be made from multilayer materials and adaptive structures to achieve unique multifunctional properties such as high hardness, impact toughness, adjustable stiffness, lightweight, and excellent shock absorption.

This paper reports an integrated theoretical, computational (finite element analysis, FEA), and experimental investigation conducted for newly designed asymmetrical auxetic structures that exhibit the NPR effect and good impact force absorption or diversion capability. When an impact force is applied to a protective pad, especially right at the most vulnerable location of possible injury, absorption, and diversion of the impact force are the critical factor for the protection of the human body. For use in soft robotics, different patterns of deformations are also desirable for different motions of body parts and joints. Asymmetry along a longitudinal axis and lateral axis and also repetitive patterns in different directions were studied. Various combinations of auxetic cell patterns were modeled and investigated. 3D CAD models of auxetic structures were developed and their structural characteristics were evaluated through static analyses of FEA models. Through FEA, force and stress distribution on the bottom of the auxetic pads were examined while impact forces were applied on the top surface. The 3D-printed prototypes were then tested, and the results were compared with the computational prediction. Different profiles of stress and force distribution were observed for different patterns. The mitigation of impact forces was also observed. The simulation and test results showed that the asymmetrical auxetic material has high NPR and can be effective for absorbing or diverting impact forces.
Microgrid Partitioning: an Impact Assessment of Integrating a Photovoltaic System With Electrical Energy Storage Devices
Authors: Baniatta Ban , Azzam Ahmad , Abdelsalam Emad , Nawafah Hamza , Kafiah Feras , Qandil Hassan
Published: February 2024

This work assesses the impact of integrating a photovoltaic (PV) system with electrical energy storage devices at a business park in Jordan. The electrical grid of the business park was partitioned as a microgrid from the main national electrical grid. DigSILENT software was used to model the single-line diagram of the microgrid. A total of 0.5 MW PV system and a 0.5 MW Li-ion storage system were assessed in this study. Voltage loadings and frequency were among the measured simulation parameters to evaluate the impact of the integration on the distribution level. The results showed that the harmonic distortion did not exceed the 3% limit set by the IEEE standard for systems under 69 kV. The results also showed that the load flow analysis for the voltage profile was stable and was within the allowed limit of 0.95–1.05 p.u. Furthermore, the integration has resulted in a reduction of up to 1,247 Metric Tons of equivalent CO2 emissions annually.
Energy Harvesting by Vortex-Induced Vibrations of Structures With Different Cross-Sections
Authors: Ali Ussama , Islam Md. , Janajreh Isam
Published: February 2024

The shape of the structure plays a crucial role in determining its vibration characteristics, such as the amplitude and frequency of vibration. The purpose of this investigation is to explore how the flow-induced vibration behavior and energy harvesting potential are impacted by the cross-sectional shape of a structure. In this work, the cross-sectional shapes of the bluff body considered are circular, square, diamond, and triangle. The reduced velocity (Ur) is varied in the range of 2–12. The mass ratio is taken as 1.7, and the damping ratio as 0.016. The hydraulic diameter for all the shapes is kept constant, and the Reynolds number based on the hydraulic diameter is varied in the range of 1.7 × 104 to 10.3 × 104 to mimic the flow velocity of the water current in the ocean (0.19–1.14 m/s). In this work, water is considered as the flowing fluid, which is supposed to be incompressible and viscous. The flow dynamics of the fluid over a bluff body are described using the unsteady Reynolds Averaged Navier-Stokes equations, and the turbulence is modeled through the SST k-ω turbulence model. Based on the findings, it can be concluded that the shape of the bluff body has a significant impact on both the vibration characteristics, the output power, and the efficiency of energy harvesting. The analysis suggests that circular shapes are ideal for energy harvesting from flow-induced vibrations at low Ur, while diamond shapes are most suitable at high Ur. In this study, the maximum output power of 1.57 W was obtained with a diamond-shaped structure at Ur = 10. Whereas the maximum efficiency of 9.01% was obtained through the circular structure at Ur = 4.
Experimental Study of Monovalent Salt and Hydrochloric Acid Solution Effects on the Stability of Blank Oil-Water Dispersion in Batch Separators
Authors: Alanazi Khalid , Mohan R. , Kolla S. S. , Shoham O.
Published: February 2024

The effect of aqueous phase salinity and acidity on the stability of oil-water dispersion is poorly understood. This is because most research works use complex solutions of mixed monovalent and divalent salts to replicate the composition of brine solution in the aqueous phase of crude oil emulsion. Hence, the relevance of each form of ionic solution cannot be determined without isolating and analyzing a laboratory-created oil-water dispersion. Toward this objective, this study aims to investigate the impact of monovalent salt solution and acidic water on the stability of blank (emulsifier-free) oil-in-water (O/W) and water-in-oil (W/O) emulsion. Fluids were mixed at a constant stirrer speed (2,500 rpm) and time (5 minutes) for each investigated emulsion. Mineral oil (EXXSOL™ D110) and distilled water with density and viscosity ratios of 0.805 and 0.330, respectively, were chosen as the pure fluids. Sodium chloride (NaCl) was used to vary the concentration of monovalent salt (from 1 to 60 g/L) in the aqueous phase, whereas a 1.0 M hydrochloric acid solution was used to alter the acidity (pH = 4.80 to 1.88) of distilled water. Experiments ranging from less than a minute to several hours were conducted using four water cuts (WC = 25%, 50%, 75%, and 90%). The brine and acidic water phase had shown large impacts on the stability of O/W (90% and 75% WC) emulsions but had minor effects on W/O (25% and 50% WC) emulsions.
Experimental Investigation, Characterization, and Microstructural Enhancement of Laser Cladded Al-Si-Sn-Cu/Ti-6Al-4V Composite Coatings
Authors: Fatoba Olawale Samuel , Jen Tien-Chien
Published: February 2024

The manufacturing sector has not yet experienced a significant additive manufacturing (AM) effect. This is because there are a number of technical obstacles to be surmounted, such as a lack of process comprehension and in-situ process monitoring and quality control, particularly in metal AM systems. These factors can have a significant impact on the microstructure and the functionality of the manufactured coatings. AM processing parameters can be challenging to fine-tune. The process parameters can cause part deformation and microcracks, residual stresses that develop in the parts/coatings being made severely restrict their actual use. The study focuses on improving the mechanical and hardness properties of the titanium alloy (base metal) using quaternary (Al-Si-Sn-Cu) reinforcement coatings and direct laser metal deposition (DLMD) technique. The experimental work was carried out in South Africa at the National Laser Center (Pretoria) using a 3000 W Ytterbium Laser System (YLS). Multiple tracks were used, each measuring 65 mm in length, with a 2 mm spot diameter. For the purpose of characterizing the materials, standard method was used. The process factors were optimized using a L9 orthogonal design of experiment. Process variables included varying laser power, powder feed rate, and scan speed. According to the findings, the formation of titanium-aluminum (Ti3Al) led to a rise in copper weight percentage, which improved tensile strength, yield strength, and hardness properties. Additionally, copper atomic mobility during solidification led to the formation of the beta-titanium phase. The polished grains were created by adding layers, which resulted in the formation of the thin columnar and elongated grains. Increased scanning speed led to finer grains being created in the microstructure due to a faster cooling rate.
A Numerical and Experimental Investigation About Tensile Fracture in Epoxy Composite Grout Under Thermo-Mechanical Load
Authors: Waseetuddin Nahri S. , Abubakar Abba A.
Published: February 2024

Grouts are designed to provide high load-bearing capability and chemical/material compatibility in building structures’ crevices, cracks, and gaps. Much research has recently been conducted concerning replacing conventional cementitious grout with polymer-based materials. The present study investigates the fracture behavior of epoxy composite grout under flexural loads and different temperatures. The flexural fracture will be the primary fracture mechanism considered in this study. The XFEM, combined with experimentation, will be used to study the influence of thermo-mechanical flexural load on the fracture behavior of epoxy grout. The XFEM method simulates deformation, stresses, strains, and cracking behavior without needing re-meshing and any equation inputs. The numerical simulation is carried out for the epoxy and the cementitious samples at 25°C and 65°C. Experiments are performed for the benchmark flexural problem, and its results are further validated by comparing them with the XFEM simulation. The flexural strength of epoxy grout is much higher than that of the cementitious one at 25°C. Significant micro-cracking in cementitious grouts is observed, further decreasing its capacity to withstand high loads. The strength of the epoxy grout decreases with increasing temperature. The presence of voids increases with temperature, weakening the epoxy material structure under high temperatures. Selecting a more compatible filler material type, shape, and size can enhance the fracture toughness of epoxy composite grout.
Computational Modeling of Extreme Particles Deformation and Grain Refinement During Cold Spray Deposition
Authors: Abubakar Abba A. , Al-Athel Khaled S. , Akhtar Syed S.
Published: February 2024

When deposition parameters are carefully set, cold spraying can successfully deposit composite coatings with customized characteristics. To avoid conducting repeated experimental trials, numerical simulations are critically needed to optimize the cold spray deposition parameters. During cold spraying of the composite layer, extreme particle deformation and temperature rise occur due to the complex interactions among dissimilar particles; hence, the coating layer properties vary across the thickness. In the cold spray literature, particle grain refinement is not considered in numerical simulation studies. The present study uses a physics-based hybrid computational technique to simulate multi-material particle deformation during the cold spray deposition of Ni-Al2O3 coating utilized for wear applications. The hybrid approach effectively combines point cloud and finite element models to simulate particle deformation and interactions during the cold spray process. An attempt to predict the grain refinement due to extreme deformation and dynamic recrystallization of deformed particles is made for the first time using the phase field method (PFM). The strain field and temperature distribution are used to predict the grain size evolution in the deformed particles. The numerical simulation results are validated by comparing them with those of experiments. The results show that the softer Ni (matrix) particles undergo higher deformation, and their deformation pattern is strongly affected by the presence of neighboring Al2O3 particles. Due to higher plastic strain and strain rate, the particle’s deformation affects the grain size evolution, mainly in the Ni matrix material. The extremely deformed regions, such as Ni particle interfaces and edges, demonstrate the possibility for grain refinement according to simulation data on strain rate, temperature, and deformation among dissimilar particles. The current study aims to establish a reliable numerical methodology for the optimization and prediction of properties of composite made from cold spraying.