bluuebunny/crossref_metadata_2025 huggingface dataset:
Applied Machine Learning Method to Predict Crack Propagation Path in Polycrystalline Graphene Sheet
Authors: Elapolu Mohan S. R. , Shishir Md. Imrul Reza , Tabarraei Alireza
Published: January 2022

A machine learning model is developed to predict the crack propagation path in polycrystalline graphene sheets. The dataset used for training the machine learning (ML) model is obtained from the molecular dynamics (MD) simulations. A training set of 700 samples has been used to train the ML model. Each training sample consists of an input image which contains the information of the initial configuration of precracked polycrystalline graphene sheet and an output image which contains the information of crack path. After training, the ML model can predict the crack propagation path in polycrystalline graphene sheet instantaneously, thus avoiding the computational costs involved with MD simulations.
Stochastic Analysis of the Interphase Thickness and Modulus in Carbon Fiber Reinforced Polymer Matrix Composites
Authors: Yekani Fard Masoud , Raji Brian
Published: January 2022

Atomic Force Microscopy based Peak Force Quantitative Nanomechanics Mapping (PFQNM) technique with the high lateral resolution was used for the characterization of the interphase in polymer matrix composites (PMC) at the nanoscale. Details of the calibration parameters include probe stiffness, real spring constant, tip radius, tapping force, deformation level, synchronous distance, drive3 amplitude sensitivity (DDS3), and deflection sensitivity for heterogeneous PMC, were discussed. Reduced modulus, adhesion, and deformation results were used to examine the interphase zone thickness and properties. The symmetric composite laminate plates have a thickness of ∼8mm. Specimens from the subsurface (∼400 μm from the surface) and the depth (∼ 4mm from the surface) were considered. The polymer matrix composite samples have been exposed to heat and humidity. AFM Multimode 8, scanner type J with a maximum scanning window of 125μm × 125μm, was used. The Derjaguin, Muller, Toropov (DMT) equation was applied to the retract curve to calculate the elastic modulus. The Weibull model was used to examine material properties’ statistical distribution. The scale parameter and the Weibull modulus (shape parameter) of the distribution characterize the data’s scattering. A higher Weibull modulus means a steeper function and a lower dispersion. The Weibull analysis results illustrated the effects of the local moisture content on the interphase thickness and the reduced modulus.
Additive Manufacturing With Ceramics
Authors: Campanella Jesse , Figueroa-Cecco Ivan , Fujinaka Ian , Sasek Adam , Nowicki Margaret , Vargas-Gonzalez Lionel , Ku Nicholas
Published: January 2022

The purpose of this project was to modify and improve an off-the-shelf 3D printer, previously modified by Army Research Laboratory, to print a ceramic slurry of B4C and SiC. Initial iterations suggest improvement in mixedness of the ceramic composite is desirable to create a more homogenous blended microstructure. The initial design utilized a basic auger shape designed to move the slurry along, but it did not effectively mix the two slurries while printing. Various auger designs were also modeled in SolidWorks, matching the rheological properties of the ceramic slurries engaged in the print, to determine influence of geometric modifications on auger performance. Experimental augers were printed using a Formlabs 2 stereolithography printer, with clear photopolymer resin, and tested on the modified 3D printer. Modeling predictions were verified through the experimental print allowing for rapid analysis of geometric modifications without requiring an experimental print for each iteration. The group examined the homogeneity of the mixture under a 10x and then 40x microscope. A point counting method, like that used in traditional volume fraction analysis, was employed to evaluate mixedness.
Deriving Thermal Model From Data by Sparse Identification Based on Physical Laws
Authors: Suzuki Tomoyuki , Kano Akira , Hirohata Kenji
Published: January 2022

In this paper, we propose a method for creating a reduced-order model (ROM) for temperature prediction that can be applied to nonlinear time-variant systems. Our nonlinear time-variant ROM is an extension of sparse identification of nonlinear dynamical systems, first proposed in 2016. Three machine learning methods are developed for automatically deriving a thermal network model from time series data. Link relationships between temperature nodes and parameter settings, such as thermal resistance and heat capacity, are automatically inferred by machine learning. Because the proposed model targets phenomena that can be represented as a thermal network model, it can deal with forced convection with velocity as a variable. The model can also handle natural convection and radiation, where thermal resistance is a function of temperature. The model can be created using a very small amount of time series data. Unlike black-box AI, the proposed model is easy to interpret; in other words, it enables us to understand the heat transfer process. Furthermore, because it is based on a physical model, it has high prediction accuracy when extrapolated. The effectiveness of the proposed method is demonstrated using the results of thermo-fluid analysis for an air-cooled power module. In addition, because the proposed method can be created using a very small amount of time series data, has high extrapolation accuracy, and is easy to interpret, it is expected not only that design parameters can be fine-tuned and actual loads can be taken into account, but also that condition-based maintenance can be realized through real-time simulation.
Fluid-Structure Interaction of Slender Biofilaments at Low Reynolds Numbers
Authors: Mortazavi Mehrad , Ayyaswamy Venkattraman , Gopinath Arvind , Goyal Sachin
Published: January 2022

Active filamentous organelles such as cilia and flagella oscillate due to the interplay between activity, elasticity, and viscous hydrodynamic drag. The presence of no-slip boundaries also impacts the viscous drag forces on the filament. Recent efforts to develop low Reynolds numbers synthetic swimmers and mixers that mimic the ciliary dynamics have used effective elastic filaments that are animated. The instabilities underlying the spatiotemporal dynamics of such biomimetic filaments are dominated equally by elasticity and fluid-solid viscous interactions. Predicting ensuing patterns requires robust computational models that can capture both large-amplitude elastic deformation of the filaments and associated long-ranged hydrodynamic interactions. To address this coupled elastohydrodynamic problem, we develop a composite framework that combines a computational rod model valid for slender filaments and slender body theory (SBT) that accounts for hydrodynamic interactions. The presence of no-slip boundaries is accounted for by using a wall-corrected slender body theory (W-SBT). We analyze the accuracy of the slender body formulations and compare them to solutions obtained via computational fluid dynamic solvers. SBT and W-SBT are found to be computationally faster than other hydrodynamic models; however, they may not provide accurate solutions for small aspect ratio filaments. The fluid-structure interaction model we present here, provides a starting point to computationally investigate the movements of natural and biomimetic cilia and flagella in the vicinity of plane walls.
Research on the Application of Acoustic Emission Technology in the Health Monitoring of the Reducers on Amusement Devices
Authors: Zhang Junjiao , Shen Gongtian , Shen Yongna , Yuan Yilin , Zhang Wenjun , Li Juanjuan
Published: January 2022

The reducer is a very important mechanical part of large-scale rotating amusement devices such as the popular big pendulum. It constantly adjusts the speed during the operation of the device and bears different loads. Due to it is difficult to disassemble after its installation, there is no effective method for the detection or online monitoring. Acoustic emission (AE) technology is an effective tool for condition monitoring and fault diagnosis of rotating machinery. AE tests for the reducer were studied in the lab. The effects of speed change and load change on the AE signals of the reducer are respectively obtained. The filed test on reducers of a big pendulum in the amusement park was carried out. The AE characteristics of the reducer with the movement of the pendulum were analyzed. The results show that AE technology will play an important role in the health monitoring of the reducer on amusement devices.
Finite Element Analysis on Plastic Collapse Behavior of Topology-Optimized Cellular Structure Subject to Compressive Loading
Authors: Takase Yuta , Kawano Takahiro , Kojima Tomohisa , Tsuji Tomoaki
Published: January 2022

The cellular structure is an assembly of cells. It may have excellent properties such as lightweight, high rigidity, and high energy absorption capacity with artificially manufactured cellular structure. However, guidelines for designing cellular structures with desired properties have not been established. This study aims to present the design guidelines for cellular structures with high energy absorption capacity. The unit cell was designed by topology optimization with the objective function of stiffness maximization. The compressive behaviors of the topology-optimized cellular structure and BCC, FCC lattice structures were investigated by carrying out the compression analysis by finite element method (FEM). A full model and a simplified model with a reduced number of cells with periodic boundary conditions were built for the analysis. It was confirmed that the use of the simplified model could significantly reduce the analysis cost. From the analysis results, it was shown that the deformation modes of the struts of the cell were different in optimized structure and BCC, FCC lattice structures. Finally, the specific energy absorption and the specific strength of each structure were evaluated. The optimized shape had high energy absorption capacity and specific strength compared with the BCC and FCC lattice structures. Further study is necessary to examine the objective function and boundary conditions in topology optimization to design cellular structures with larger energy absorption capacity by controlling the stress-strain relationships.
Use of LiDAR for Negative Obstacle Detection: A Thorough Review
Authors: Guerrero-Bañales Luis Daniel , Hernández-Bautista Ignacio , López-Parra Marcelo , Ricardo-Torres Osiris
Published: January 2022

Negative obstacles for field autonomous land vehicles refer to potholes, ditches, cliffs, pits, or any type of obstacles that are on the road but not in a visible way, which bring risks both to the vehicles or potential passengers and even to the environments where autonomous land vehicles are moving along. These negative obstacles can cause severe damage to autonomous land vehicles, from damage to the vehicle’s suspension, rollovers, or even loss of the autonomous vehicle. Obstacle detection is the first step to avoid any risk, and it is extremely important to be able to warn of nearby obstacles, to avoid any type of danger that may arise. In recent years several articles have been published on the different types of hazards or obstacles and different methods of avoiding them. The authors report on ways to better understand the environment so that autonomous land vehicles stay out of harm’s way. Some of the dangers could be, the collision with another vehicle, hitting a pedestrian, not recognizing the traffic signs on the road, leaving the planned routes or lanes, or not braking when they detect an obstacle. The use of image recognition using different types of cameras, as well as the use of ultrasonic sensors and Light Detection and Ranging (LiDAR) sensors, or the combination of some or all of the sensors is widely used in the field of autonomous land vehicles. Most of this research work has been carried out in positive obstacle detection; that is, obstacles that are above the road. However, the detection of negative obstacles and their avoidance remains less explored. Due to this, an exhaustive review is made of the state of the art of use of LiDAR sensors in the detection of negative obstacles applied in autonomous land vehicles and the different techniques that have been used to recognize and classify the different types of potholes, ditches, pits.
Tolerance Analysis of Contacting Assembly Parts Based on Parametric Space Envelope
Authors: Nie Jiaqi , Luo Chen , Zhou Yijun
Published: January 2022

Tolerance is an important part of design and manufacturing. Applying right level of tolerance is vital for manufacturers to gain a competitive edge. This paper proposes a new method to analyze the geometric tolerance for two mating parts for compliant assembly. Under proposal, the two mating parts are represented in a purpose-built parametric space and the manufacturing deviation of the two parts is linked to movements of a compact set of control points. The contact state of the two parts is formulated as an optimization problem by minimizing the distance between the two parts under non-negative constraints (i.e. the two parts are not embedded during the assembly process). By solving the optimization problem, the translation distance along the assembly direction can be obtained to ensure that the two parts are in non-penetration contacts. The assembly tolerance is analyzed in the contact state with the idea of selective assembly. The effectiveness of the method is verified through a case study on assembling two plane metal sheets. The proposed method has significance on formulating geometric tolerances for compliant assembly.
Design and Energy Flow Management of Hybrid Renewable Energy System
Authors: Amini Reza , Davani Abbasali A. , Pourgol Mohamad Mohammad
Published: January 2022

Wind and solar energies are promising renewable energy technologies, in which hybrid renewable energy systems are gained much attention in remote area locations. The present study proposes the design and energy flow management of stand-alone hybrid wind and solar energy systems. Fuel cells and batteries are used as backup resources, so it ensures the load is unceasingly provided. An electrolyzer is used to generate hydrogen from excess energy requirements. First, Mathematical modeling of hybrid system components, including photovoltaics, wind turbines, fuel cells, batteries, and electrolyzers, is provided. Hence, we have developed a novel energy flow management algorithm, which intelligently controls the energy flow management system using a fuzzy logic control system. We have compared the performance of the novel energy management system with the conventional approach. Our novel approach will prevent these systems from being hit, and system upgrades will be enhanced during startup. In the conventional power management system, the voltage overshoot of the on-off controller is 425 V. At the same time, the fuzzy logic control reaches 405 V. The controller’s on-off time is 31.1 seconds, but this is 0.041 for the fuzzy logic controller, which is much more stable.
Fostering Student Engagement and Learning in Online and Flex Delivered Thermodynamics Courses via Two-Stage Concept Inventory Quizzes in Time of COVID
Authors: Sadeghizadeh Zahra
Published: January 2022

The COVID-19 pandemic has required many engineering programs to design and deliver their courses in more flexible formats, including courses that involve teaching students who are participating remotely and face-to-face at the same time (flex courses). However, in the meantime, it is essential to ensure that students are remaining actively engaged in the learning process and that their remote presence is not negatively affecting their conceptual understating of the course materials. The objective of this study was to use concept inventory in the format of a two-stage quiz to investigate how this format impacts students’ performance and engagement in both online and flex delivery modes. During two-stage quizzes, students first work on conceptual problems individually and then collaborates in groups that are remote or hybrid. This approach applied for two sections of an Engineering Thermodynamics class, one delivered in flex dual-mode format and one fully online. It was interesting to see how the level of confidence and students’ perception to answer conceptual questions including misconceptions, change as they interact in different forms of teams. The statistical analysis shows there is no significant difference between online and flex mode results, however students confidence level in answering concept-based questions increases significantly in group answers for both modalities. Additionally, an anonymous survey was developed to receive student’s perceptions and feedback about their learning experience.
Variable Stiff Revolute Joint for Compliant Robot
Authors: Sharma Manoj K. , Kitts Christopher
Published: January 2022

Over the past decades industrial robot manipulators have expanded throughout the automation landscape with their high degree of repeatability and accuracy. For safety reasons these robots are not allowed to share their workspace along with humans, which limits the various tasks that can be performed by a human-robot collaboration. To circumvent this limitation, a new kind of variable stiffness series elastic actuator is proposed as a joint actuator. This variable stiffness series elastic actuator has an ability to servo-control its joint stiffness, and provide a measure of the instantaneous joint torque. Soft joint intrinsically enhances safety by providing compliance in the event of an impact. These unique abilities play a crucial role in an intelligent robot control design that can scale down the risk factors in a field where humans and robots collaborate. This article presents the design of variable stiffness series elastic actuator, mathematical modeling, and calibration of the variable stiffness series elastic actuator.
Prediction of Hot Deformation Behaviors Under Multiaxial Loading Using Gurson-Tvergaard-Needleman Damage Model for Inconel 718 Alloy Thin Sheet
Authors: Mahalle Gauri , Kotkunde Nitin , Kumar Gupta Amit , Kumar Singh Swadesh , Nikhare Chetan P.
Published: January 2022

Inconel 718 is a high strength, precipitation-hardenable Ni-Fe-Cr-based superalloys, mostly used in nuclear and aerospace applications in extreme working conditions. In this work, hot deformation behavior of the Inconel 718 alloy sheet has been investigated at 700°C under multiaxial loading conditions. The forming behavior has been analyzed along three distinct deformation modes (biaxial stretch, plane strain, and uniaxial stress regions) and results were quantified using a Gurson-Tvergaard-Needleman (GTN) damage model. Firstly, uniaxial tensile tests have been performed at 700°C and quasi-static strain rates (0.0001–0.01 s−1) to identify the material constants of the damage model. Further, the standard Nakazima test has been conducted to describe the forming and fracture behavior along three deformation modes. Further, Marciniak-Kuczynski model using a GTN damage model with Barlat’89 anisotropic yield criteria have been used for theoretical prediction of failure strains for Inconel 718 alloy. This model shown a good prediction capability in terms of fracture strains. Subsequently, Finite element (FE) analysis of Nakazima test coupled with plastic and damage modeling has been carried out to predict failure behavior of the Inconel alloy. The FE predicted results showed good agreement with the experimental test in predicting the fracture behavior of the alloy. The presented results give a basis of optimal hot forming process of Inconel 718 alloy.
Analysis of Traction Electric Motors Used in Commercial HEV and BEV
Authors: Arriaga-Vigil Alfonso , Karamanis Eleftherios , Lopez-Parra Marcelo , Ricardo-Torres Osiris
Published: January 2022

The design of electric traction motors is a complex task since high-performance requirements must be met in terms of power and torque densities in the wide operation speed range, including volume and mass restrictions. Since the launch of the GM EV, in 1996, electrification has been increasing and hybrid and electric vehicle traction motors have incorporated constant improvements and very innovative designs. This paper reports on motor specifications of 16 of the most representative commercial hybrid and electric vehicles, additionally, presents a comparison of their special design features and performance. Although there are plenty of technical publications on electric traction motors and some of the commercial motors presented herein are very well known in detailed, the authors develop and present a finite element method and Ansys® Electronics Suite comparison, which is based on efficiency maps. The results show the chronological evolution of different mechanical configurations that have successfully been arranged to improve the performance of traction motors over the years. The main conclusion is that the geometry of the magnetic circuit is one of the most important characteristics and that high optimized designs are needed.
Optimal Interior Mounted Permanent Magnet Synchronous Motors MTPA and MPPA Control Based on Sliding Mode Approaches
Authors: Alnami Hashim , Pang Chengzong , Papineni Avinash , Wang Xin
Published: January 2022

This paper presents novel sliding mode control (SMC) approaches for Maximum Torque Per Ampere (MTPA) and Maximum Power Per Ampere (MPPA) of interior permanent magnet synchronous motors (IPMs). We first derive the first-order sliding mode control methods to improve the field oriented control’s resiliency against the external perturbations, extraneous noise and modeling uncertainties. And after that, we propose the higher-order sliding mode control to significantly reduce the chattering phenomenon which is inherent in the first order sliding mode control method. Based on the comparison studies, the conventional proportional-integral derivative based field oriented control shows sluggish response and is more sensitive to parameter perturbations and external torque disturbances. By introducing the novel sliding mode control methods, both of the speed and torque regulation performance of interior-mounted permanent magnet synchronous motor can be greatly improved. Computer simulation studies have shown the superior performance of the first-order and higher-order sliding mode controllers for interior permanent magnet synchronous motor speed and torque regulation applications.
A Comprehensive 3D FEM Model to Study Forces, Cutting Temperature and Residual Stresses During Vibration Assisted Hard Turning Considering Tool Cooling Cycle
Authors: Dutta Pranesh , Bartarya Gaurav
Published: January 2022

The use of hardened steel in the automotive industry has increased of late. For longevity of the component under fatigue loading, residual stresses play an important role. The fatigue life of a machined component improves when the nature of the residual stress profile generated is compressive. In the present work, the machining forces, tool tip temperature and the nature of the residual stress generated have been studied in Vibrating Assisted Machining (VAM) conditions where the tool vibrates at low amplitude and high frequency. The vibration makes the tool create a constant engagement and disengagement motion with the workpiece. A three-dimensional thermo-mechanical FEM model has been developed to study the effects of VAM on turning of hardened (62 HRC) AISI 52100 steels. The model predicted the radial forces with sufficient accuracy for continuous turning. The air cooling of the tool during disengagement from the workpiece, gives rise to convective heat transfer to the surrounding, resulting in efficient the cooling of the tool. The same has been verified by analysing the effect of vibrating velocity (Vv) on tool tip temperature. The intermittent nature of VAM decreased the average tool tip temperature. The residual stress generated at different cutting speeds under vibration (Vv) was also predicted. For larger Vv, the residual stress profile became more compressive compared to that generated in the conventional hard turning simulations.
Hardware-in-the-Loop Simulation for Large-Scale Applications
Authors: Krama Abdelbasset , Gharib Mohamed
Published: January 2022

The hardware-in-the-loop (HIL) testing methodology has recently gained wide acceptance from the scientific community worldwide, as it allows virtual or actual components of a complex system to be implemented and tested together with the controller in a real-time environment. In this paper, three different case studies are investigated to show the use of the HIL testing methodology in different disciplines. In the first case study, a shunt active power filter for power quality improvement in a distribution network is presented and investigated using the HIL methodology. In the first case study, a HIL platform for drill string system control has also been developed and its operational principle and hardware components are explained. In the third case study, a HIL testing platform was developed for high power induction motor driving drill string system, in which the drill string is studied together with the induction motor and a variable frequency drive to match real-world case scenarios. A variety of tests were performed to provide a comprehensive study on the effectiveness of the HIL testing platform on different applications that take advantage of state-of-the-art real-time simulators. The presented HIL infrastructure can be extended to accommodate different studies on other electromechanical systems.
Active Vibration Control of Piezoelectric Beam Using the PID Controller
Authors: Alnuaimi Mohammed , BuAbdulla Abdulaziz , Silva Tarcísio , Altamimi Sumaya , Lee Dong-Wook , Al Teneiji Mohamed
Published: January 2022

Vibration control using piezoelectric materials has been widely investigated over the past decades. Particularly, active controllers achieve greater vibration control over wider frequency ranges than other vibration control techniques. Active controllers make use of sensors, actuators, and control laws. While most researchers focus on improving the control law, investigations on the optimal placement of sensors and actuators remain much less explored. This work presents a simple and quick methodology to obtain the optimal placement of piezoelectric sensors and actuators on different electromechanically coupled systems, without using classical beam or plate structures or limiting assumptions (symmetrical bending, linear strain, etc.). Optimal placement of sensors and actuators is performed based upon two criteria: i) varying the number of piezoelectric layers used for sensing and actuation and ii) varying the position over the structure’s thickness. Each criterion (i and ii) is presented and discussed in a different study case. Results show that as the number of piezoelectric layers increases, vibrations are controlled more efficiently. However, stacking several piezoelectric materials is not easily feasible in practice, leading to a tradeoff between reducing vibrations (using more layers) and ease of assembly. As of criterion ii), optimal placement of piezoelectric sensors and actuators is the farthest possible from the neutral line since sensors generate larger signal output (increased sensor gain), and actuators apply larger momentum on the system reducing more vibrations.
Modular Design of Space Expandable Capsule Based on Origami-Inspired Structures and Stretchable Mechanism
Authors: Xiao Liping , Xu Zhao , Wang Ke , Kang Boqi , Wang Anping , Zhao Haifeng
Published: January 2022

The deployable structures based on origami have been widely utilized in the design of spacecraft structures. With the advantages of foldability and stowability, origami-inspired structures can be folded into a pre-designed shape to fit into the rocket envelope. In this study, a novel configuration of the modular expandable capsule was developed based on origami-inspired structures and stretchable mechanism. The whole capsule was composed of multiple identical units with origami structures. In each unit, the geometric parameters such as width and length were quantitatively designed, and their influence on the packaging ratio of each unit was discussed. The origami creases were treated as joints in the context of motion structures. Then, Denavit and Hartenberg (D-H) method was adopted to establish kinematic relation of capsule units. Through the theory of thick origami, motion characteristics of each unit with nonzero thickness panels can be constructed. Furthermore, stretchable mechanism with hyperelastic behavior was employed to resolve issues of geometric compatibilities during the process of folding and expanding. Finally, a prototype of origami-inspired capsule unit was fabricated to examine its motion behaviors. The results demonstrated the feasibility and effectiveness of such a design for potential space missions. This work can be treated as an innovative attempt to design large-scale space architectures, which can be assembled and constructed on orbit.
Interconnection of Renewable Resources, New Opportunity in the Rehabilitation of Old Small Hydropower Plant
Authors: Radulescu Bogdan Alexandru , Radulescu Victorita
Published: January 2022

In Romania, before 1990, numerous small hydroelectric power plants - SHP were realized for the electrification of isolated areas or small communities. Since 2007, a new concept concerning the operational parameters and yields has been implemented, and the functional SHPs have been re-evaluated. A massive environmental data monitoring campaign has started, creating an economically appropriate SHP database that can be associated with another renewable resource. This paper presents such a pilot station, the first realized in Romania near the Arges River, SHP Budeasa, interconnected with a wind power plant. Some local conditions and part of the realized database are briefly presented. Due to the increase in local demand for electricity, it was necessary to rehabilitate this SHP by associating it with 2 other power plants based on renewable sources. Each component of the pilot station is analyzed separately. After the commissioning of the wind farm an additional production of electricity was obtained, and the pilot station became profitable. From these benefits, the rehabilitation of SHP Budeasa started. The theoretical model, the essential steps in the physical realization and necessary conditions for interconnection are mentioned. The results obtained after seven months of operation and some economic aspects are finally mentioned.
A Case Study on the Effect of Uncertain Impacts of a Civil Aircraft Fuselage Section With Auxiliary Fuel Tank
Authors: Rayhan Saiaf Bin , Pu Xue
Published: January 2022

Crashworthiness studies the safety qualification of a vehicle (both airborne and road transports) to protect its occupants during an impact. For an aircraft, specific crashworthiness criteria like deformation pattern of the structure, absorbed kinetic energy profile, and acceleration responses experienced by the components and human body models must be met before it receives the transport certification. Therefore, in recent times, crashworthiness has emerged as a crucial field of study during the early design stages of aircraft along with other key parameters like weight reduction, load factor, and fatigue life estimation, etc. During the investigations of fuselage section crashworthiness, the solutions are mostly presented based on a perfect vertical impact without considering any effect of roll and pitch of the fuselage. However, in a practical situation, an abrupt event can be introduced with uncertain impact phenomena. Therefore, in this current research, a civil aircraft fuselage section with an onboard auxiliary fuel tank is studied based on five different uncertain impacts considering both different roll and pitch angles. A commercial explicit dynamic code Ansys Autodyn is adopted to investigate the virtual drop tests. Then the numerical outcomes are compared based on the seat trail acceleration responses, kinetic energy absorption of the components, and plastic deformation of the structure due to the investigated uncertain impacts. It is found that a minor change in roll and pitch angle has a significant effect on the acceleration responses of the accelerometers and the plastic deformation pattern of the fuselage section.
Multi-Working Conditions Topology Optimization of the Key Structure of the Climbable AGV Based on Level-Set Method
Authors: Fei Jiacheng , Zhou Yijun , Luo Chen
Published: January 2022

Compared with the traditional Automated Guided Vehicle (AGV), a climbable AGV is capable of moving on the flat ground and climbing vertically with the aid of the track. The mechanical condition of the supporting parts of the climbing AGV can change drastically in different working environments. Therefore, it is critical to optimize the structure of the key parts in a lightweight design. In this paper, the level-set topology optimization was conducted in order to achieve a better structure design of the key body parts. Under this proposal, mechanical analysis of the key body parts was carried out under typical working conditions. Various working conditions are taken into account during the optimization process through introducing weight coefficients computed by analytic hierarchy process (AHP) method. And the casting constraint was added to improve the manufacturability of the optimization result. Then the topology optimization model under multi-working conditions was established based on the level-set method. And the optimization result with a clear boundary was obtained. Finally, the optimization result was analyzed with the finite element method. Compared with the initial structure, the weight of the optimized structure is greatly reduced by 42.64% in the testing case while the mechanical properties of the optimized structure still meet the design demands. The same method can be extended to optimize other parts to reduce the total weight of the climbable AGV.
Emissions Reduction of a Direct Injection Diesel Marine Engine by Adding Hydrogen to the Inlet Manifold
Authors: Tealdo Carlos , Deutsch Jorge Alex
Published: January 2022

Global Warming is imminent. Emissions must be cut immediately. However, there are many challenges in reducing air pollution. It must be a cheap, abundant, efficient solution that occupies a small space and can be retrofitted to existing diesel engines.

The aim of this experiment is to explore the effect of adding Hydrogen to diesel engines. An experiment was conducted on a single-cylinder engine, under diverse running conditions with different flow rates of hydrogen.

The experiment is intended to prove that hydrogen injection adapts to engine operation without major modifications. Subsequently, various tests were conducted to measure the engine emissions.

This research made in diesel engines gradually blend hydrogen into it seeking for lower emissions in an effort to comply with new IMO regulations in old vessels engines, to increase their lifespan, it aims to be an alternative for scrubber, with the advantage of no sludge or waste is produced.
Nonlinear Vibrations of Rotor-Bearing Systems Supported by Squeeze Film Dampers Due to Unbalance Excitation
Authors: Sevencan Furkan , Cigeroglu Ender , Baran Özgür Uğraş
Published: January 2022

In this paper, nonlinear dynamic behaviors of a multi-mass flexible rotor-bearing system supported by short length Squeeze Film Damper (SFD) due to the unbalance excitation are presented. The rotordynamic model of the system is developed by using 1D Timoshenko beam elements for flexible shafts, lumped inertias for disks, linear springs and viscous dampers for bearings and structural damping for the system. The nonlinear SFD model is based on the analytical solution of Reynolds equation for open ends short length SFDs assuming circular-centered orbit motion. The SFD’s nonlinear damping coefficient matrix and mass coefficient matrix generated because of fluid inertia are obtained. In this model, rotor system matrices and nonlinear SFD coefficient matrices are incorporated to obtain the full system mass, gyroscopic, damping and stiffness matrices. Harmonic Balance Method (HBM) is used to represent the resulting nonlinear differential equations of motion as a set of nonlinear algebraic equations. Newton’s Method with arc-length continuation is utilized as the solution method for the set of nonlinear algebraic equations obtained. A rotor of a small turbojet engine, details of which is available in the literature, is considered as an example. Different nonlinear responses of the rotordynamic system are investigated in order to observe the effects of SFD’s diameter, clearance and length parameters and the amount of unbalance loadings and their locations.
Incorporation of Blade Twist and Non-Uniform Inflow Effects In Undergraduate Helicopter Aeronautics Whirl Stand Laboratory
Authors: Paquin Jeremy , Harris Evan , San Martin Emma , Kirby Dennis , Melnyk Richard , Humbert Nathan
Published: January 2022

Flight and aerodynamics laboratory experiences have supported the aeronautical engineering courses in the United States Military Academy’s mechanical engineering program for over 50 years. Whirl stands are the rotary-wing equivalent of wind tunnels; they are used to generate experimental data on small- or full-scale rotor systems. The helicopter whirl stand laboratory is a cornerstone event in the program’s Helicopter Aeronautics course, used to reinforce students’ understanding for predicting and calculating hover performance data. The experimental apparatus includes a remote control (RC) helicopter mounted to a static test stand, instrumented with load cells to measure lift and torque. The helicopter is capable of varied revolutions per minute (RPM) and collective blade pitch. Control of the apparatus and measurement readings occur from behind a protective wall with an observation window. The objective of the laboratory is to compare the results of predictive analyses, conducted using Blade Element Theory (BET) and Blade Element Momentum Theory (BEMT), to experimental data. Students calculate the coefficient of thrust based on collective pitch angles and atmospheric conditions using an iterative approach in numerical analysis software. A recent effort appreciably improved the lab by adding two experimental twisted-blade cases in addition to the original untwisted blades. The ability to change between the original and updated (twisted) blades offers insight into the advantages and disadvantages of each in hover. The upgraded blades were designed internally by students to match the original rotor diameter, outsourced for precision manufacturing, and tested for incorporation into the laboratory. Overall, the upgraded laboratory offers a relevant, comprehensive application to deepen students’ conceptual understanding of rotorcraft aerodynamics, laboratory procedures, and modeling principles taught in the course.
High-Damping Viscoelastic Material Monitoring Using Sub-Resonator Enhanced Electro-Mechanical Impedance Spectroscopy
Authors: Lu Runye , Shen Yanfeng
Published: January 2022

This paper presents the Electromechanical Impedance Spectroscopy (EMIS) method employing a novel piezoelectric wafer active sensor (PWAS) with sub-resonators, which can generate additional resonant peaks to enhance the impedance signature. In order to develop an in-depth understanding of the mechanism behind the sub-resonator effects, an analytical investigation is conducted first. The theoretical solution for the impedance of the new sub-resonator PWAS transducer is derived. Furthermore, numerical simulations are carried out to demonstrate the effectiveness of the new transducer to create additional resonant peaks. Harmonic analysis of coupled field finite element (FEM) models is conducted. Material degradations are modeled by altering the material properties like density and elastic modulus. Comparative investigations are carried out with both conventional PWAS transducers and sub-resonator PWAS transducers. EMI damage indices based on the spectral amplitude and frequency variation features are used to quantify the material degradation and simultaneously prove the superiority of the sub-resonator PWAS over the conventional PWAS. Additionally, a high-damping dog-bone specimen is employed to conduct the creep experiment lasting for twenty-four hours with a recording interval of two hours. The impedance spectra are obtained by the Bode-100 impedance analyzer. The experimental results further demonstrate the improved sensitivity of the sub-resonator transducer, which is in good agreement with the theoretical and numerical findings. The paper finishes with summary, concluding remarks, and suggestions for future work.
Analysis of Ice Propagation and Salt Diffusion in Freezing Desalination
Authors: Zhang Hongtao , Janajreh Isam
Published: January 2022

Freezing desalination (FD) is attractive and more sustainable option due to the low energy consumption and less maintenance. However, technical challenges such as low freezing rate and process complexity arising from the salt trapping in the produced ice hinder the commercialization of this method. In this work, freezing experiments of water-NaCl solution are carried out to investigate the ice propagation and its salinity distribution to understand the salt trapping phenomena. Results reveals subcooling followed by a homogenous temperature jump occurs in the solution at an early stage of freezing suggesting ice freezing happens to large solution bulk. The Ice-front in brine is also characterized with many sharp and disorderly ice tips and there are many channels filled with liquids inside the formed ice block. This heterogeneous growth of ice promotes salt trapping. The salt distribution in the formed ice reveals that the salinity gradient in that early freezing stage is quite small and it rises dramatically at the last several layers of ice. The salinity in the first 10% frozen ice is only half of initial salinity which suggests a suitable freezing fraction of initial solution in freezing desalination. Finally, the developed first principle model based on the obtained salinity gradient is proved to be reasonably accurate to predict the freezing time with acceptable discrepancies and less computation cost.
Increased Vehicle Intrusion as a Result of Vehicle Weight
Authors: Eichaker Lauren , Trepeck Cameron , Arnett Michael , Chen H. Fred , Wiechel John , Guenther Dennis
Published: January 2022

Vehicle accidents remain a leading contribution to accidental deaths in the United States. Recently, there has been increased interest on how differences in cargo loading affect crash kinematics. This paper demonstrates that at a particular speed, increases in the vehicle cargo weight can influence the magnitude of the vehicle deformation. Larger deformations may involve greater intrusion into the occupant space. This increased intrusion may adversely affect the injury potential for the occupant by reducing survivable space and overcoming safety features. Additionally, an accident reconstructionist may need to consider the difference in cargo loading and distribution when calculating specific accident characteristics in their analyses. For example, the kinetic energy change between loaded and unloaded conditions is a feature of interest during vehicle collisions. These concepts were validated using Engineering Dynamic Company’s (EDC) Human, Vehicle, Environment (HVE) accident reconstruction software. The HVE analysis included simulating impacts of vehicles with varying cargo loads; HVE was also used to visualize the concepts described above. The case studies will have approximately similar BEV’s, crash speeds and other vehicle characteristics.
Verification Study of the Nuclear PRA for the Mars 2020 Mission Following Accidental Orbital Re-Entry
Authors: Earthperson Arjun , Diaconeasa Mihai A.
Published: January 2022

Today, Probabilistic Risk Assessment (PRA) plays a vital role in assuring mission success for robotic and crewed missions alike. Current-day PRA techniques integrate multimodal, often black-box analyses to build comprehensive risk profiles. This paper describes a review and verification study of the “Nuclear Risk Assessment for the Mars 2020 Mission Environmental Impact Statement” (N-PRA)[1]. Sandia National Labs conducted the N-PRA for NASA’s Jet Propulsion Laboratory (JPL). More specifically, we have verified the source term calculations associated with the release of radionuclides from a Multi-Mission Radiothermoelectic Generator (MMRTG) power source for a limited set of accident scenarios in the case of an accidental re-entry into Earth Orbit with an Earth impacting trajectory.

We achieve this by using analytical methods[2] historically implemented for the Cassini Mission PRA[3] for a failed planetary swingby gravity-assist. Our results are within 28% to 56% of the referenced study. Limitations in our methodology are attributed to a lack of modern simulation-based tools and deterministic methods for modeling complex physical phenomena. The results are interpreted and compared with the values presented by the initial authors, along with comments for improving our current methodology.
Temperature-Dependent Impact Properties of ABS Polymer
Authors: Kratzok Max , Saigal Anil , Zimmerman Michael
Published: January 2022

Polymeric materials are composed of chains of molecules known as monomers which are held together by secondary bonds. Amorphous polymers have a glass transition temperature above which their behavior transitions from glassy to viscoelastic, meaning they act like both a viscous liquid and an elastic solid. This concept may seem familiar to anyone who has used Silly Putty®; bouncing a ball of Silly Putty causes the material to behave elastically whereas it will flow into a puddle if left on a table overnight.

Time temperature superposition (TTS) describes the dependence of viscoelastic mechanical properties on time and temperature. Repeating the Silly Putty experiment at a different temperature will change how long it takes to reach the same end mechanical property. The Williams-Landel-Ferry (WLF) equation empirically defines the relationship between a temperature shift and a shift in the timescale for a specific material property. It has been widely used for materials undergoing low rates of strain (e.g. creep, stress relaxation), but it applies to any property of viscoelastic behavior.

This paper examines modeling the temperature-dependent impact behavior of polymers based on the WLF equation. Although polymers experience viscoelastic behavior for an incredibly short time prior to fracture, the strong temperature dependence and past literature suggest the validity of the WLF equation to higher rates of strain as demonstrated herein for the energy absorption of acrylonitrile-butadiene-styrene (ABS) undergoing high-velocity multiaxial impact tests.