bluuebunny/crossref_metadata_2025 huggingface dataset:
Vibrational Analysis of Additively Manufactured 3D Printed Metal Beams With Multiple Void Defects
Authors: Shaheen Samaher , Lloyd-Harry Sam , O’Connor Dennis M.
Published: January 2025

Additive manufacturing (AM), also known as 3D printing, has transformed aerospace, automotive, and energy industries, enabling the production of specialized components that with traditional methods, would not be possible. In the oil and gas industry, AM provides transformative benefits, including designing unique parts with complex geometries, such as advanced turbines or valves, that increase efficiency and resilience, while reducing lead times and costs. Internal defects in 3D metal printing can compromise structural integrity, leading to equipment failure and operational disruptions. Therefore, it is crucial to identify internal defects in 3D metal printed parts. While these methods exist, there remain quality assurance challenges regarding the detection of internal defects.

This Study focuses on analyzing the vibrational response of 3D printed metal beams with multiple internal defects modeled as voids, using analytical and Finite Element Methods (FEM). The study aims to locate and characterize these internal voids and understand their impact on the structural integrity of beams. A key aspect of this analysis is using the Relative Frequency Shift (RFS) method, which examines the natural frequency changes in beams with voids to identify and understand the impact of the voids on the composition, structure, and mechanical properties of the beam. ANSYS software confirms the results of this method, simulating real-world conditions. This paper offers a comprehensive approach to detecting internal voids, ensuring structural integrity, and enhancing quality assurance of 3D printed metal parts.
Numerical Investigation of Wear Characteristics of Rollers in Hot Metal Spinning Process
Authors: Demirtunç Mehmet , Özaslan Emre , Yetgin Ali , Acar Bülent
Published: January 2025

In the hot metal forming industry, the estimation of roller lifespan is crucial as it directly impacts costs. When rollers are commercialized in the industry, it is necessary to specify the roller lifespan. One of the factors directly influencing roller lifespan is wear. Rollers are prone to wear due to repeated mechanical loads over long periods of time under high temperature.

In dry metal spinning processes with high rotation and advancement velocities, the wear of the rollers needs to be calculated. Therefore, the proposed framework delves into the assessment of wear quantities, a pivotal metric for estimating roller lifetime. Wear exhibits different behaviors based on temperature. In processes where rollers are exposed to high temperatures exceeding 400°C, adhesive wear predominates, resulting in the adherence of roller particles. Conversely, the focus shifts to abrasive wear in processes where roller temperature ranges between 27°C and 400°C, as is in this study. In spinning processes where the temperature of the workpiece attains 900°C, the temperature of the hot tool steel rollers does not exceed 400 degrees. Accordingly, warm wear equations are utilized in the examination of roller wear within processes up to 900°C. In this situation, the wear calculation utilizes the Archard wear model. Time-dependent contact pressure and sliding velocity values for rollers with high rotation and advancement velocities are calculated using the finite element model. However, the wear constant and hardness of the roller vary with temperature. Therefore, the model takes into account the variation of wear constant and hardness based on temperature. A coupled temperature-displacement model is established to capture the heat transfer between the roller and the workpiece. Subsequently, relationships between wear constant – temperature and hardness – temperature are established, enabling the execution of wear calculations. The workpiece and roller are modeled using solid elements, and wear is calculated based on points on a cross-sectional surface of the roller. The wear on the cross-section is generalized to the entire cylindrical solid model, and the wear profile on the cylindrical roller surface during the hot dry metal spinning process is examined. In this study, a novel method developed for wear prediction of cylindrical rollers in hot dry metal spinning processes is proposed. The developed method can be generalized for all calculation of wear for dry metal spinning and forging processes regardless of temperature. The future work includes experimental validation of the wear performances and profile of the Roller for Hot Dry Metal Spinning Process.
Numerical Simulation of a Supersonic Flow Over a Flat Plate
Authors: Banos Lemus Diego , Law Deify
Published: January 2025

Studying supersonic flow simulations over a flat plate serves as a foundation in understanding the complexity of several aerodynamic problems. This paper investigates such problems using Fluent to gain insights of the properties and characteristics of the fluid behaves when a flat plate is set under such flow. These insights are then applicable to the development, study and analysis of other simple aerodynamic shapes that later, help with the development and the design of high-speed vehicles, such as rockets, missiles, airfoils, and aircraft. The two-dimensional laminar flow simulation employs the complete Navier-Stokes equations alongside the Second Order Upwind scheme to achieve a steady-state solution using the density-based solver. The air is modeled as a perfect gas with a constant Prandtl number, and the viscosity being evaluated by Sutherland’s Law at Low Reynold Numbers. The obtained results are compared against analytical solutions and literature values to assess deeper understanding of how shock waves interact with the boundary layer in supersonic flows, with a specific focus on analyzing the velocity, pressure, and temperature fields in the created domain and at the trailing edge of the selected geometry. The structured mesh is employed in the first case, developing later a more refined mesh as a second case to optimize the cell numbers stacked on the flow domain for a better analysis and capturing of shockwaves. This initial approach provides a good defined foundation for future investigations with turbulence models and the study of different geometries found on high-speed vehicles Future work will involve extending the simulation with the turbulent flow models at different Mach numbers, investigating different variations in the flow field with a longer flat plate when there is a transition between laminar and turbulent flow.
Magnetorheological Finishing of 3D Printed Free-Form Aerofoiled Surface
Authors: Khatri Shubham , Singh Surya Pratap , Singh Anant Kumar
Published: January 2025

Polylactic acid (PLA) is popular in 3D printing due to its affordability, biodegradability, and user-friendly properties. Industries such as automotive, aerospace, and medical are increasingly integrating PLA-printed parts. In the present study, a 3D-printed aerofoil is taken as a 3D workpiece. The surface finish of aerofoil plays a crucial role in aviation and fluid dynamics. In aviation, it enhances efficiency in generating lift and stability. In fluid dynamics, it minimizes drag and reduces turbulence. The use of magnetorheological finishing (MRF) enhances the surface quality of aerofoils. MRF has controlled finishing forces to obtain the desired surface finish, coupled with tool rotation and swirling motion, which remove roughness peaks. MRF employs MR polishing (MRP) fluid containing abrasive and electrolyte iron particles suspended in a base fluid. Finite element analysis (FEA) determines the magnetic flux intensity for MRF. The parameters, like current, working gap, and tool rotation speed, are set at 2A, 0.6 mm, and 300 rpm. Initial surface roughness (Ra) of the 3D-printed aerofoil is measured as 9.13 μm, reduced to 0.21 μm through 15 minutes of grinding. MRF of 25 minutes reduced Ra to 0.03 μm. Scanning electron microscopy (SEM) is used to analyze the surface characteristics of aerofoil before and after MRF. The reduced Ra of the aerofoil can enhance the aerodynamic performance by reducing drag and increasing lift. Also, it promotes laminar flow and reduces turbulence. The MRF process on aerofoil proves the six-axis MRF setup is capable of removing the stair-stepping effect from the 3D printed workpiece and provides fine finishing for its better performance.
Experimental Testing of Hydrodynamic Tapered Land Fixed Geometry Thrust Bearing Under Dynamic Load
Authors: Ali Muhammad , Lutfullaeva Anbara , Yasko Isaiah
Published: January 2025

Hydrodynamic thrust bearings in rotary machines are affected by varying environmental conditions, necessitating a clear understanding of operating parameters like oil film pressure, thickness, and temperature. Measuring oil film pressure, especially under dynamic conditions, is challenging but crucial for proper design. This study presents experimental investigation of tapered land hydrodynamic thrust bearings under dynamic loading, filling a gap in published research. A custom dynamic loading system was designed and installed into a previously established static loading tapered land hydrodynamic thrust bearing testing apparatus. Here, the new dynamic loading system is used to measure film pressures under dynamic loads (2–10 Hz, 150 lbs, 350 lbs peak loads, and 1500 RPM) to a thrust bearing with 0.002” taper depth. Results are compared to static load tests with similar peak loads and show significant pressure reductions (up to 59.4%) with increasing load frequency. These findings offer insights into hydrodynamic thrust bearing performance under dynamic loads, aiding in design considerations.
A New Morphology Evaluation Method for 3d Printed Surfaces Based on GLCM
Authors: Chen Hua , Chen Shijie , Yang Can
Published: January 2025

3D printing is the primary processing technology of additive manufacturing, widely utilized in industries such as healthcare, aerospace, and automotive. Due to technical limitations, its surface exhibits quality defects, including laminar texture, warpage deformation, bubble holes, and cracks. Its unique processing principles result in a surface appearance distinct from subtractive manufacturing. Evaluating 3D printed surfaces using traditional subtractive manufacturing methods neglects local features, has limitations in quantification, lacks comprehensiveness, exhibits strong subjectivity, and has low evaluation efficiency. In this paper, a new method for quantitative analysis and evaluation of 3D printed surfaces had been proposed based on Gray Level Co-occurrence Matrix (GLCM). The method provides a more comprehensive evaluation of the surface quality in terms of four dimensions: contrast, energy, correlation and entropy by acquiring image data from the surface of different 3D printed samples and applying the GLCM to accurately analyze the surface texture. Firstly, the effects of step size, gray level, and orientation on the GLCM were investigated, and the surface topography of 3D printed workpieces was measured by using the GLCM with appropriate parameters. Subsequently, four feature parameters, i.e., contrast, energy, correlation, and entropy, were used to comprehensively evaluate the surface of the workpiece. This method provides a new idea for the evaluation and quality control of 3D printed complex surfaces.
Energy Absorbing Analysis and Deformation Mode Comparison of Traditional and Additively Manufactured Crush Tubes
Authors: Jenson Sean , Switzer Ian , Ali Muhammad , Wisner Brian
Published: January 2025

Thin-walled axial crushing members (or “crush tubes”) are often utilized for energy absorption due to their high strength-to-weight ratios. They are created by filling a homogenous outer “tube” with a filler “core” material. The addition of the core has been shown to provide multiple benefits, including an increased structural stability during deformation or collapse and an increase to the energy absorbed by the structure. The total energy that can be absorbed by these structures is dependent on the deformation modes present during compression as well as the material properties used for the tube and core. Common core geometries include graded honeycomb structures or similar support members. Additive manufacturing (AM), however, has created an opportunity for complex energy absorbing structures to be used instead. Specifically, laser powder bed fusion (LPBF) can be used to manufacture complex geometries from aluminum powder with material properties comparable to an extruded state. The present study aimed to compare AM and traditional axial crushing member cores with a graded cellular structure through a numerical approach using ABAQUS/Explicit dynamic modeling environment. Material properties were assigned to a traditional tube (A36 steel) with a standard cellular core (6061 Al) and to a traditional tube with an AM cellular core (AM Al), both with frictional loss penalties and general contact property definitions. Analysis was performed until densification of the structure was observed and numerical results were recorded for the crushing force, deformation mode(s), plateau stress, and total energy absorbed for each tube variation and the results compared. The results of this study found that the AM core had comparable performance to the extruded version, with the AM core presenting a 3.1% increase in total energy absorption over the extruded core.
Modeling of Nanoscale Characteristics of Carbon Nanotube Nanocomposites Through Experimental and Statistical Methods
Authors: Norkus Tyler , Yekani Fard Masoud
Published: January 2025

The versatility of polymer matrix fiber-reinforced composites enables a wide range of applications in industry. Carbon nanotubes (CNTs) can be used to reinforce polymer nanocomposites (PNCs), but as with other laminated composites, delamination remains a concern and influences the integrity of the composite system. This paper examines the ratio between CNT bundle size and interphase thickness through atomic force microscopy (AFM) and statistical analysis of nanoscale data in an effort to introduce a new parameter for the fracture toughness of CNT PNCs. Specifically, the authors characterized buckypaper, a composite made up of CNT networks in epoxy. AFM was used to collect 500 data sets for low-weight percentage CNT PNC and almost 190 sets for high-weight CNT PNC. The data sets included the distribution of CNT bundle size and interphase thickness; several Weibull models were used to analyze the stochastic data distribution and simulate the properties of CNT PNCs. Two-, three-, and four-parameter Weibull models were used, with initial results showing that the four-parameter model was most effective.
Rapid Prototyping of Protective Structures for Micro-Unmanned Aerial Systems Through Additive Manufacturing
Authors: Emerick Ludvig , Mcghee Evan , Murphy Nolan , Harkin Darragh , Aliperti Chris , Hoyer Brodie
Published: January 2025

Micro Unmanned Aerial Systems (mUAS) continue to gain prominence on the modern battlefield, providing an expedient and portable platform for conducting Intelligence, Surveillance, and Reconnaissance (ISR) to small, isolated combat units. The objective of this study is to develop a rapidly-deployable, intuitive, and low-cost means of preventing damage to mUAS rotor blades, enabling increased training hours at decreased potential cost and thereby increasing overall operator proficiency on the system. To that end, we concurrently pursued two possible solutions: (1) use of additive manufacturing to design and produce a low-cost, easily replaceable airfoil that could be used during training exercises in lieu of the high performance airfoil and (2) the use of additive manufacturing to create a protective structure around the existing rotor that could be easily affixed to the mUAS for training operations while reliably sheltering the rotors from potentially damaging impacts. While the replacement rotor blade revealed shortcomings in current additive manufacturing processes for this application, the protective barrier accomplished the goal of increasing survivability of the mUAS performance during training while not significantly impairing its performance. Through this design study, we succeeded in creating an adaptable, open source, easily distributed “press print” solution that will allow units across the Army to print, on an as-needed basis, rotor protection structures, easily and effectively increasing user proficiency on a key enabling technology.
Modeling and Simulation of Wellhead Installation Digital Position Sensing Measurement
Authors: Wang Yaou , Lim Haw Keat , Lee Yong Wee , Zhang Haitao , Battentier Amandine
Published: January 2025

Correct installation of the wellhead is crucial to drilling operations for the oil and gas industry. Installation is conventionally examined manually and visually with high potential risk of errors. A digital position sensing solution for wellhead installation was recently developed through combining ultrasonic nondestructive testing and machine learning methods. Training the machine learning model required extensive data through a large number of laboratory tests. This work applies the finite element method to simulate the ultrasonic nondestructive laboratory testing process. Simulation prediction showed identical echo waves and sensor signals as test measurements. The simulation method developed in this work generated physical mode-based predictions, which would help understand the sensing solution system and potentially provide it with supplemental training data. This would further the reliability of the sensing solution system.
Parylene Capping Layer for Embedded Liquid Mass for MEMS Packaging
Authors: Adhikari Rahul , Jackson Nathan
Published: January 2025

Microelectromechanical Systems (MEMS) packaging is over 80% of the cost of a typical MEMS device because there are no standard packaging methods, and each device requires unique packaging. Recently several MEMS devices have illustrated the desire to have a liquid filled cavity within the MEMS device for applications such as biomedical sensors, tunable energy harvesters, or liquid cooling microelectronics. However, embedded liquids in silicon pose a challenge when it comes to packaging. This paper illustrates a novel concept of using a conformal parylene coating to cap or encapsulate the liquid. The concept is validated using various liquids such as various viscosity silicone oils as well as Galinstan a Ga-based liquid metal. The study investigates the packaging reliability through a series of systematic accelerated life-time testing, elevated temperature testing, accelerated soak testing, and mechanical testing (shock and resonant frequency testing). Mass changes were monitored and compared to control (no capping), glass epoxy bonded packaging, and silicone spray coating encapsulation. The results demonstrate the superior mean-time-to-failure of the parylene capping method compared to the other methods. The results confirm that parylene can be used to package embedded liquids in silicon or 3D printed structures.
Lamb Wave-Based Inspection of Solar Cell Arrays
Authors: Green Mattie , Alsaffar Fadhel , Mal Ajit , Schaal Christoph
Published: January 2025

Solar arrays provide electricity to spacecraft by converting energy from the sun. Generally, solar arrays are made by adhering multiple solar cells to a substrate, usually with silicone based adhesives. They may be prone to disbond failures at the cell interface due to mismatch of the coefficients of thermal expansion. Manufacturing errors like voids in the adhesive layer can also occur. If disbonds are not detected and repaired, the electrical interconnects can fail due to cyclic thermal loads in space. This is significant because the failure of even one interconnect can cause power loss to a number of cells. This paper aims to evaluate the feasibility and sensitivity of inspecting bonded joints in solar arrays in space. One potential nondestructive evaluation technique relies on Lamb waves. These waves have been used for disbond detection in layered media. In this work, this methodology is extended to detecting disbonds between layers of different materials and sizes as in the case of a solar cell bonded to a larger substrate. Transient structural finite element analyses are conducted using Abaqus. For simplicity, a 2D representation is modeled of an isolated silicon solar cell bonded to a larger polymer substrate panel. Disbonds of varying size and location are studied and compared to a pristine case with no disbond between the cell and substrate. Several damage indices are defined and evaluated for effectiveness in indicating specific defect characteristics. Using these damage indices, almost all of the tested disbond cases are shown to be fully characterizable according to size and location, including disbonds as small as 1 mm. The results of this study could be applicable beyond the scope of this work to any layered medium with materials of highly dissimilar stiffness.
Development and Modeling of a Structural Health Monitoring Payload for Low Earth Orbit Experiment
Authors: Ellis Gage , Fawcett William , Garcia Chrstopher , Tapia Dylan , Zagrai Andrei
Published: January 2025

This contribution discusses aspects of mechanical design, fabrication, and modeling of a payload that supports Structural Health Monitoring (SHM) experiments aboard the International Space Station (ISS). As the space industry becomes more commercialized, the need for safe and long-lasting space assets has increased exponentially. Implementation of SHM to space structures has considerable potential to improve safety of operation, and controllability of spacecraft. In order to better understand the effects of the space environment on space structures, the New Mexico Institute of Mining and Technology (NMT) is sending a payload to the ISS to collect data representing the effects of the space environment on SHM methodology and hardware. This is an active payload designed to house several SHM experiments. SHM experiments include guided wave propagation in a metallic structure, monitoring of an imitated crack, assessment of a bolted joint, investigation of structural vibration via electromechanical impedance method, and acoustic emission monitoring. In addition, piezoelectric sensor self-assessment is realized using the impedance diagnostics.

The payload fits the Materials International Space Station Experiment (MISSE) module specifications and is designed to operate in LEO under vacuum, volatile orbital thermal cycles, and background radiation. In order to simulate the effects of the environment on the payload, two finite element models are performed for thermal analysis: an orbital heating model, and a quarter cycle heat distribution model. The orbital heating model predicts the external thermal loads on the payload at any point in an orbit, including solar radiation, albedo, radiation from the earth, and radiation to deep space. The quarter cycle model predicts the internal thermal loads as the payload travels from shade to sun and predicts the temperature at critical locations including computer location. The payload experimental data will serve as a baseline for environmental conditions and will aid design and modeling of future SHM systems. Measures to protect SHM systems are discussed. Predictive models and calculations of payload thermal performance obtained in laboratory tests are presented and discussed considering expected variations due to the LEO environment.
Semi-Customized Orthoses Designed With Adjustable Features to Facilitate Mass Production With Enhanced Fitting Performance
Authors: Mo Yaru , Johnson Shane
Published: January 2025

Orthoses are essential medical devices used in rehabilitation. A high degree of orthotic customization enhances the fitting performance. However, it generally necessitates higher cost and longer time for fabrication. This study proposes a semi-customized approach for orthotic design, aiming at reducing the time and cost related to the orthotic manufacturing while maintaining the fitting quality. Twelve semi-customized modular arm braces integrated with adjustable connectors were developed, and their adjustability and fitting performance were evaluated computationally and experimentally. It was shown that the connectors designed with special features can provide the required deformation range within [−9.2, +10.5] mm to accommodate intra-cluster variations. Computational analysis demonstrated the necessity of incorporating adjustable features in providing customized fitting. Additionally, the designed semi-customized modular braces exhibited the ability to conform to target surfaces, with 75% of regions showing a normal distance < 1.5 mm post-adjustment. As for the experiment, the participant provided positive feedback on fitting, further demonstrating the satisfactory performance of adjustable semi-customized designs. This proposed semi-customized methodology offers cost-effective and time-saving solutions for orthotic manufacturing without compromising fitting quality, which enables mass production of orthoses with enhanced comfort and advances the orthotic technology.
A Two-Level Optimization Approach for the Synthesis, Design and Operation of Multi-Energy Systems Integrated With Energy Networks
Authors: Dal Cin Enrico , Carraro Gianluca , Tsatsaronis George
Published: January 2025

Achieving decarbonization targets requires optimizing the synthesis, design, and operation of multi-energy systems that meet end-user demand for different forms of energy, with the goal of minimizing costs. This means contextually finding the number, type, location, size and operation conditions of the conversion and storage units that supply the required energy, as well as the topology and capacity of the networks that deliver it to the end users. However, this inherently integrated problem includes several nonlinearities and an extremely large number of continuous and binary decision variables, making it impractical to solve. Linearization allows the computational complexity to be drastically reduced. Nevertheless, the combinatorial nature of binary variables exponentially increases computational time. To simplify the problem while ensuring good accuracy of the results, this study presents an evolutionary algorithm that decomposes the overall problem into two levels: i) selection and placement of components to be included in the system (synthesis) and ii) sizing and scheduling of the included components (design and operation). This allows for a drastic decrease in combinatorial complexity and, in turn, in computational time. The proposed two-level algorithm is validated here against the traditional mixed integer linear programming (MILP) approach for solving the complete, non-decomposed problem. Finally, application examples considering electrical and heating networks coupled with both renewable and conventional energy conversion and storage systems show that decomposition reduces computational time by up to 70% and provides solutions to problems that otherwise cannot be solved in an acceptable time.
Closed Loop Vision Guided Control of Flyer Position for High-Throughput Laser Shock Experiments
Authors: Wang Heyun , Diamond Jacob M. , Bhattacharjee Anuruddha , Wanchoo Piyush , Mirzaei Ahmad , Li Liuchi , Nkansah-Mahaney T. Joseph , Ramesh Kaliat , Krieger Axel
Published: January 2025

In materials science, high-throughput material processing and testing are crucial for rapid materials design and discovery, but manual operations often create bottlenecks in terms of speed and accuracy. Automating the repetitive and labor-intensive aspects of material testing significantly increases throughput and consistency, facilitating a more efficient pathway to material innovation. This study demonstrates automated process control by integrating robotic automation in a high-throughput laser shock system using closed-loop “see-move-shoot” experiments. The system employs two automated linear stages to sequentially manipulate material specimens (flyers) under a laser for impact testing. Each experiment includes automatic target detection, sample centering, laser activation, impact verification, and progression to the next sample. For flyer detection, we developed a computer vision algorithm using a convolutional neural network (CNN) model based on EfficientNetB0. Trained on 16,000 labeled images under various lighting conditions, the model achieved a root mean square error (RMSE) of 0.038 mm in extreme testing conditions (i.e., under high exposure, low light, or blurry images) ensuring reliable and efficient real-time processing. In our “see-move-shoot” comparison study, manual operation took 30.6 seconds for a novice user and 19.2 seconds for an expert user per shot, while the CNN model required only 7.46 seconds. Consequently, the CNN model conducts experiments 4 times faster than the novice user and 2.5 times faster than the expert user.
Empowering Future Engineers: Integrating Scientific Literacy and Critical Analysis in the Study of Waste Treatment and Gaseous Effluents
Authors: Carvalho Violeta , Teixeira Senhorinha , Teixeira José C.
Published: January 2025

This study introduces a teamwork approach implemented in the “Treatment of waste and gaseous effluents” curricular unit (CU) within the Mechanical Engineering Master program at the University of Minho. Recognizing the importance of fostering critical thinking and scientific literacy skills, particularly for master dissertation development, this CU included teamwork where students had to prepare a short critical literature review about a separator technology selected by them using some scientific papers. Furthermore, a field visit to a company was organized and a seminar seeking to promote active learning strategies.

To equip students for teamwork, lessons covered effective scientific literature searching, reference management software utilization, and the critical review writing process. Initial feedback from students was obtained through the application of a short questionnaire and the results indicated a positive response to the teamwork activity, with reported improvements in literature search proficiency and critical analysis skills. The collaborative learning environment was appreciated, and students expressed enhanced confidence in evaluating research methodology and forming informed opinions.
Dynamic Fault Tree Games and Reinforcement Learning for System Reliability
Authors: Jha Mayank , Chulliyat Jose Amal , Grimstad Joachim , Morozov Andrey
Published: January 2025

This paper introduces a novel approach to analyzing the reliability of complex systems using model-based system engineering and adversarial multi-agent reinforcement learning. The merger of these approaches aims to identify the critical paths in a dynamic fault tree that may lead to system failure. Further, this study also explores the feasibility of leveraging transfer learning to train neural networks representing adversarial agents within a simulated gaming environment and craft fault-tolerant systems capable of adaptations in dynamic settings. The proposed methodology involves adversarial multi-agent reinforcement learning, where adversarial agents, labeled “red agent” and “blue agent,” compete in a zero-sum game environment to induce or avert system failure, respectively. Multiple games are played on different environment versions, reflecting changes introduced by dynamic fault tree adjustments. However, the extensive interactions between the agents and the environment pose challenges for complex, large-scale systems because of the many interactions involved. These interaction results must be stored for optimizing the policy later on, thus increasing the space and time complexities. To mitigate this challenge, transfer learning is introduced to enhance agent learning performance by transferring knowledge acquired from previous game environment versions instead of training them from scratch each time.
Comparison of Electrode Configuration for (0,2) Piezoelectric Micromachined Ultrasound Transducer
Authors: Popal Abdul Q. , Janardhana Ranjith D. , Akram Fazli , Jackson Nathan
Published: January 2025

Piezoelectric micromachined ultrasound transducers (PMUT) have been extensively used in numerous applications. Most PMUT applications operate in the first mode (0,1), and extensive investigation into the effects of the electrode design on performance have been previously investigated. However, specific applications such as atomizers or biosensors can operate in higher modes such as (0,2) and (0,3), but the effects of electrode configuration on these modes are limited. This study focuses on optimizing the electrode configuration of higher-order PMUT devices. The (0,2) and (0,3) modes are essential for vibrating mesh atomizers (VMA) as it has a high central force that allows liquid to be squeezed through the nozzles. The PMUT devices comprise two thin Pt electrodes, a lead zirconate titanate (PZT) piezoelectric layer sandwiched between the electrodes and a Si membrane. The Finite element modeling (FEM) study aims to determine an optimal electrode configuration to enhance displacement and velocity of the membrane. A 2D FEM was used to simulate the devices, and multiple electrode designs were compared in terms of membrane amplitude and velocity. The devices were operated at resonant frequency, with a constant AC voltage of 100 Vpp. The results showed that the electrode design significantly affects both displacement and velocity, and the optimal electrode configuration is based is based on nodal circles which is different from (0,1) mode. A single-layer circular electrode covering the entire membrane had the lowest displacement. In contrast, a multiple-ring configuration with the electrode rings located at a gap from the nodal circle locations gave the highest displacement and velocity.
Experimental Investigation on the Annular Drilling of Acute Angle Micro-Holes in Nickel Based Superalloy With Femtosecond Laser
Authors: Gonumakulapalle Lodi Samuel , Kumar Sunil
Published: January 2025

Micro holes play a pivotal role in enhancing the efficiency of aero engines. These micro holes necessitate precise drilling at acute angles with respect to plate surface to optimize cooling performance and enhance film cooling effectiveness. Inclined holes offer an advantage over those perpendicular to the surface by promoting more uniform airflow, thereby facilitating better dispersion of coolant. This study introduces femtosecond laser annular drilling with different scanning routes as a novel method for fabricating high quality acute-angle micro holes. Cylindrical micro holes with a diameter of 400 μm are drilled at angle of 30° from the surface of 0.68 mm thick IN718 plate. The influence of different processing parameters like laser fluence, laser spot overlap ratio and scanning speed on surface roughness, taper angle, and aperture circularity is thoroughly evaluated and discussed. The cross-section morphology analysis is conducted using scanning electron microscope (SEM) integrated with energy-dispersive spectroscope (EDS). Experiments have done using proposed drilling method with femtosecond laser. The diameters of entry and exit holes were assessed using a 3D microscope from Olympus, while the surface roughness of the sidewalls, characterized by Ra and Rq are 907.79 nm and 1.20 μm respectively. Experiments will aim to generate acute angle holes of superior quality, with the findings of this study opening up latest avenues for refining the femtosecond laser (fs) drilling method.
Reinforcement Learning-Based Identification of Failure Scenarios for Dynamic Risk Assessment of AI-Controlled Robotic Systems
Authors: Grimmeisen Philipp , Sautter Friedrich , Morozov Andrey
Published: January 2025

AI-controlled robotic systems can pose significant risks to both human workers and the environment due to their complex, autonomous operations. Traditional risk assessment methods fall short in adequately describe sophisticated failure scenarios of systems controlled by black-box policies. These traditional methods are applied manually and do not considering frequent software updates. Therefore, novel methods that enable a dynamic risk assessment for AI-controlled robotic systems are required.

In this paper, we present the concept of a new approach that enables the dynamic risk assessment of unknown or dynamically changing control policies. This includes AI-controlled robotic systems, especially those utilizing reinforcement learning. The new approach combines two key methods: (i) automated identification of failure modes and (ii) a reinforcement learning-based search for critical failure scenarios. Additionally, it incorporates an evaluation method that analyzes the detected sets of critical scenarios or events. This evaluation method creates dynamic high-level risk models and identifies vulnerabilities to specific failures.
Dynamic Analysis of Main Coolant Pump Based on Precise Integration Method
Authors: Zhu Bao , Feng Yang , Lei Ming-kai
Published: January 2025

The rotor-bearing system is an important part and core component of the main coolant pump. In this paper, the finite element modeling method of Timoshenko beam is used to carry out dynamic modeling of the rotor-bearing system of the main coolant pump. The stator and rotor in this model are constrained by the thrust bearing and the guide bearing in axial and radial directions. The difference between the radial and axial natural frequencies of the main coolant pump will cause the stiffness problem in numerical calculation. The precise integration method is used to calculate dynamic response of the rotor bearing system by overcoming the stiff problem. Our results show that, a very high-precision solution could be achieved in large time step by using the precise integration method. Based on the proposed model, the influence of operating condition parameters on dynamic response of the rotor-bearing system is investigated and discussed in details.
Effect of Surfactants on the Acoustic Patterning of Organic and Inorganic Microparticles in a Polymer Matrix
Authors: Shovon S. M. Abu Naser , Subedi Saroj , Ware Henry Oliver Tenadooah
Published: January 2025

Polymer matrix composites with acoustic-based filler orientations have multifunctional engineering applications, including sensors, flexible electronics, and embedded electrical wiring. In this work, we presented the effect of surfactants on controlling the patterning behavior of organic and inorganic microparticles in a liquid pre-polymer matrix using acoustic radiation forces created from Bulk Acoustic Waves (BAWs). A customized (30 × 22 mm2) chamber was utilized in this study. This chamber incorporated two piezoelectric transducers placed in a parallel orientation to efficiently align the embedded microparticles along the nodes of the acoustic pressure wave. In suspensions, Microparticles tend to have unwanted agglomeration when the suspension is at rest, and surfactants help to stabilize particle dispersion within the suspension. The effect of surfactants on the alignment of organic and inorganic microparticles has been analyzed at varying concentrations of particles (0.5 %, 2.5 %, 5 % w/w) in a low-viscosity liquid pre-polymer (PEGDA). Two different surfactants were studied to identify their compatibility on the suspension of particles in a ratio ranging from 1:0 to 1:1 (particle to surfactant ratio). In a 5 wt.% of organic particle concentration, the nodal distance of patterned particles was 670 μm with no surfactants (1:0), which was reduced to 470 μm when surfactants were used in a 1:1 ratio. Similarly, in 5 wt.% inorganic particles, the nodal distance was reduced from 715 μm (1:0) to 450 μm (1:1) utilizing the surfactants. Additionally, surfactants reduced the alignment time of organic and inorganic particles from 20 seconds (1:0) to 10 seconds (1:1) in 5 wt.% particle concentration. The proposed acoustic patterning method utilizing surfactants provides efficient patterning of microparticles to create high-performance polymer-polymer and polymer-metal composites towards multifunctional applications.
A Finite Element Framework for Studying Mechanical Aspects of Blast Load Induced Traumatic Brain Injury in Humans
Authors: Peterson Luke , Murphy Michael , Lee Nayeon , Sharma Gehendra , Johnson Daniel , Bakhtiarydavijani Amirhamed , Miralami Raheleh , Hammi Youssef
Published: January 2025

This work presents the generation and validation of a Finite Element (FE) simulation framework to study Traumatic Brain Injury (TBI) resulting from blast loading of the human head. The framework involves a multi-step modeling approach: first, reflected pressures are collected from discrete regions around a rigid head geometry (within a gaseous medium) in coupled Eulerian-Lagrangian blast simulations. Second, the obtained pressures are applied as region-specific discrete surface loads to the surface of a deformable FE human head model in separate Lagrangian simulations, allowing the blast effects to deform the brain geometry. This multi-step approach is used to generate shock tube loading simulations of two FE head and brain geometries featuring two classes of brain constitutive models (hyperelastic-viscoplastic Internal State Variable (ISV) model and Prony series viscoelastic model). Simulation results for coup and contrecoup brain pressures generally agree with documented intracranial pressure measurements from shock tube testing of human cadaver heads for model framework validation. Methods for obtaining and comparing brain mechanical state variable evolution to literature, documented material state metrics for TBI, and the implications and challenges for predicting blast induced TBI are discussed.
Manufacturing of a Cemented Carbide Coated Component on Design for Manufacturing Toward Combined Impact and Wear Resistance
Authors: Zhu X. P. , Wu G. J. , Shang Z. H. , Zhang S. J. , Lei M. K.
Published: January 2025

Manufacturing of components with hard, wear-resistant coatings to operate under impact service condition is a high-performance challenge for mechanical equipment in industry. On a new strategy of design for manufacturing with integrated design and processing toward desired performance, the manufacturing process optimization of WC-Ni cemented carbide coated components was implemented with a two-layer coating design onto a steel substrate, comprised of a WC-Ni outer layer and a Ni-based alloy interlayer. In the design phase, numerical analysis of impact stress and strain field evolution was carried out comparatively for the two-layer coating and the conventional single-layer coating design under an impact load of 10-kN order. The high stresses localized on the coating surface and interfaces under the impacts may cause surface integrity changes of the coated components, including surface cratering upon plastic deformation as well as cracking both in coating and at coating-substrate interface. Introducing the interlayer of material with intermediate elastic modulus and hardness in between the steel substrate and the outer layer, as well as of an appropriate thickness, can mitigate the surface integrity changes to cracking failure of coated components. The manufacturing processes of high velocity oxy-fuel spraying and/or high frequency induction cladding technologies were accordingly optimized with the two-layer design, in good agreement with the numerical analysis. The two-layer coated component showed a better impact resistance over the single-layer coating, with less plastic deformation, interlayer and/or interface cracks. A further improvement was achieved by synergistically optimized induction cladding in a process chain to enhance the interlayer cohesive and adhesive strengths metallurgically bonded to steel substrate.
Evolution of Band Gaps in the Nonlinear Dynamics of Metamaterials
Authors: Augello Riccardo , Salem Karim Abu , Carrera Erasmo
Published: January 2025

This paper proposes the study of the dynamic properties of thin-walled metamaterial structures under large displacements and rotations. The focus is given to the analysis of the vibration modes, and to their evolution as the equilibrium states change. The analysis of the evolution of the band gap, i.e. the frequency intervals between the different vibrational modes, is of main interest. The investigation of this characteristic, discussed in the paper for thin-walled structures composed of combinations of different materials, allows the design of metamaterial structures with specific and tailored physical properties. In this article, thin-wall structures consisting of repeating units are considered; these are used as benchmarks to support the theoretical discussion of the used models. Numerical simulations are conducted by means of a model based on the Carrera Unified Formulation (CUF). This formulation allows for nonlinear dynamic analysis in a more efficient computationally way compared to traditional methodologies based on 3D finite elements, yet guaranteeing the same level of accuracy. The use of CUF for nonlinear dynamic studies of thin-walled metamaterial structures, therefore, overcomes limitations related to the computational bottlenecks of more traditional FEM-based methodologies, opening up the effective exploration of the dynamic behaviour of metamaterials.
Hydrodynamics of Active Fin Control in Fish-Like Swimming
Authors: Guo Jiacheng , Dong Haibo
Published: January 2025

Median fins have been found to enhance the forward propulsion in fish-like swimming, by enhancing the caudal-fin (CF) thrust through fin-fin interaction and reducing trunk (TK) drag through body-fin interaction. For stability or performance reasons, many fish-like robots have adopted dorsal fins in their designs. There has also been growing interest in emulating the individual opening and closing of the median fins (fanning motion), observed in nature, in bio-inspired underwater vehicle designs. The current study analyzes the effect of periodic fanning of the dorsal fin (DF) on the performance of fish-like swimming, in terms of thrust production and power consumption. Using a trout-like model on which strong fin-fin interaction was discovered, periodic fanning motion of the DF has been introduced, and direct-numerical simulations (DNS) are conducted. An immersed-boundary method (IBM) is used to resolve the body shape and motion of the trout-like model. The fanning phase relative to the start of the undulating cycle is varied from 0 to 360° in increments of 60°. Regardless of the fanning phase, the hydrodynamic power is always saved compared to the absence of fanning motion. Given a fanning phase (ϕf) of 60°, the power is saved the most, though similarly forward force is reduced on the body as a whole. At ϕf = 240°, the forward force is improved compared to the no-fanning case, with a slightly reduced hydrodynamic power. It is found that at this ϕf, viscous drag on the DF is reduced given its periodic reduction of surface area, while its role as vortex generator is still fulfilled, so that the effectiveness of fin-fin interaction in enhancing CF thrust is preserved.
Effects of Flow Boiling on Mini Channels With Ultra-Thin Fins and Cavity Arrays
Authors: Nees Alexander , Carbajal Gerardo , Park Younggil , Romero Edwar
Published: January 2025

Flow boiling has numerous potential applications, including large-scale mechanisms of nuclear power plants and smaller-scale applications for electronic cooling. The heat transfer of flow boiling can be enhanced greatly by using fin arrays due to the increase in the surface area. Cavity arrays increase the heat transfer by propagating bubble formations at controlled locations. This study investigates the methods of enhancing heat transfer in flow boiling, specifically using protuberances, such as ultra-thin fins and cavities. An experimental setup was constructed, using specimen plates, fitted with fins, cavities, or just flat. They were placed upon a heated plate with different constant powers and volume flow rates. The power was left on for approximately until steady-state (SS) was achieved or a significant amount of time had passed. Then, the power was turned off and left to cool for 10 minutes. The results show that the fins were the most effective during single-phase flow. However, when the power brought both the cavities and the fins to flow boiling, they were almost equally effective. For comparison, the flat baseline specimen was unable to achieve SS during the experiments, exceeding temperatures of 200 °C and continuing to climb in several cases.