bluuebunny/crossref_metadata_2025_split huggingface dataset:
Research on Soft Electrostatic Adsorption Unit Driven by SMA
Authors: Jiang Jing , Niu Chenxu 
Published: January 2022

Abstract
Soft executive unit of soft crawling robot or soft grabbing mechanism, compared with the traditional rigid executive unit, has unlimited degrees of freedom and continuous deformation ability. Accordingly, the work performance of robot can be improved. In this paper, the soft electrostatic adsorption unit driven by Shape Memory Alloy (SMA) is proposed to obtain more grasping force on the target surface. In order to achieve adhesion and away from the target surface, two layers of SMA wires are embedded in the silica gel to drive the soft unit bend in two opposite directions. The electric-thermal-strain multi energy field coupling model of SMA actuator is established. The comparison between theoretical and experimental results demonstrates that the established mathematical model is reasonable. The factors influencing the bending angle of the soft unit are explored to improve its performance. In order to increase the contact force between the soft unit and target surface, the electrostatic adsorption electrode is combined with the soft unit. piezoelectric boost modules and photovoltage generator PLZT, which are both small and light, were proposed respectively to drive the electrostatic-adsorption electrode. Finally, the application prospect of this soft electrostatic adsorption unit is presented by designing a wall climbing robot with feet made of this soft unit.
Demonstration of a Limited Scope Probabilistic Risk Assessment for Autonomous Warehouse Robots With OpenPRA
Authors: Grimmeisen Philipp , Karimov Artur , Diaconeasa Mihai A. , Morozov Andrey 
Published: January 2022

Abstract
Probabilistic Risk Assessment (PRA) is an indispensable technology to evaluate the risk, dependability, and resilience characteristics of safety-critical systems. Therefore, PRA uses widely adopted methods, such as classical event trees, fault trees, Markov chains, Bayesian networks, and their numerous combinations. To analyze challenging failure scenarios of modern, intelligent, autonomous, and highly dynamic Cyber-Physical Systems (CPS), the integration of multiple PRA methods is needed. This paper presents a PRA approach based on classical Event Tree Analysis (ETA) and Fault Tree Analysis (FTA) and provides the technical description of a new open-source software platform called OpenPRA. Besides, this paper describes a representative case study from the autonomous system domain, focusing on autonomous warehouse robots.
Introducing Engineering Codes and Standards Throughout the Curriculum of a Newly Established Mechanical Engineering Program
Authors: Seibi A. C. , Jaafar I. , Tolman S. , Amin A. 
Published: January 2022

Abstract
The purpose of this paper is to present the development of a framework that integrates standards and codes in design related courses throughout the curriculum of a newly established mechanical engineering program at Utah Valley University (UVU). This framework will be based on the results of recently conducted surveys by the authors on Junior and Senior students. The surveys were conducted over two consecutive semesters (Fall 2020 and Spring 2021). The aim of the surveys was to i) check the students’ level of awareness and knowledge of standards and codes ii) determine the level of improvement of their understanding of codes and standards in the subsequent semester by comparing results from the first and second survey. The results of the surveys were used to develop a framework that incorporates standards and codes in design related courses throughout the curriculum. Data analysis of both surveys revealed an improvement of students’ awareness and comprehension of standards and codes in the second semester where 2/3 of the students claimed that they were familiar with standards and codes as compared to 1/3 in the first run. This has been attributed to further emphasis of standards and codes application in the design process in some of the courses. The results were used by the mechanical engineering program as a catalyst to identify the proper courses throughout the curriculum, in which design standards and codes can be introduced. The paper also outlines a plan that the program is pursuing to fill in the gap of standards and codes usage in the design process in order to meet ABET requirements and to prepare students for industry. The paper explains the assessment methods used to fulfill ABET requirements related to standards/codes and concludes with some practical steps to adopt their usage in the curriculum.
Vibro-Acoustic Ultrasonic Resonant Behavior in Skull and Cranial Contents
Authors: Dumm Christopher M. , Hiers Anna C. , Maupin David B. , Cites Marianne E. , Klinzing George E. , Balaban Carey D. , Vipperman Jeffrey S. 
Published: January 2022

Abstract
High-frequency ensonification of the head has the potential to excite unusual and difficult-to-measure internal vibration behavior. The head is a complex, interconnected vibroacoustic volume filled with and bounded by air, fluids, soft tissue structures, and bone. A literature gap exists in assessment of how ultrasonic vibrations of relatively low frequency and low amplitude might propagate within the skull and cranial contents of humans and cynomolgus macaque monkeys. Ultrasonic emitters are ubiquitous in modern society, including uses in vehicular proximity sensing, room occupancy monitoring, pest control, and industrial cleaning. This investigation uses finite-element techniques to examine vibro-acoustic behaviors of the skull and structures within the cranial cavity in the context of excitation by ultrasonic signals. Previous analysis procedures designed for assessment of possible resonant phenomena in the auditory and vestibular systems are revised and extended to assessment of the skull and the contents of the cranial cavity of humans and macaques, including volumes of cerebrospinal fluid (CSF) and the brain. Results include identification of cranial regions that may experience high-amplitude vibrations in response to ultrasonic excitation. These methods and results are useful for assessing how a wide variety of devices, including communications equipment, might produce biological effects.
A Numerical Method for Calculating Nonlinear Resonance Response Surface Based on Nonlinear Modes
Authors: Gao Qian , Li Lin , Wu Yaguang , Fan Yu 
Published: January 2022

Abstract
Excessive vibration causes high cycle fatigue and seriously threatens the integrity of mechanical structures, especially when resonance occurs. The existence of nonlinearities such as large deformation and dry friction, makes it time consuming to predict the resonance response during parameter studies. In this paper, a numerical method is proposed for efficiently predicting the resonance response surface of nonlinear systems based on nonlinear modes. The resonance response surface is defined as the hypersurface formed by the resonance peaks under different combinations of excitation levels and nonlinear parameter values in this paper. The nonlinear modal analysis is carried out only once to obtain the resonance response surface. There are two core steps of this method. First, by using the extended energy balance method, we establish the relationship between the excitation force and the resonance amplitude. Next, the mapping between the nonlinear parameter value, the excitation level, and the resonance amplitude is analytically derived. A one-DoF Duffing vibrator and a lumped parameter model containing dry friction are tested to verify this method. High accuracy and efficiency have been proved. Compared with the steady-state response analyses, the maximum relative error is less than 0.1%.
Influencing the Mechanical Properties of Fused Filament Fabrication Parts by Non-Planar Material Extrusion
Authors: Edwards Rhys , Clemon Lee 
Published: January 2022

Abstract
Current applications of Fused Filament Fabrication in additive manufacturing tend to produce heavily anisotropic parts. This is largely due to the discretisation of heterogeneous planar layers, resulting in surface artefacts, stress concentrations and weak thermal fusion bonding that fundamentally limit the strength of end-use parts. In an effort to improve the mechanical properties of parts produced by Fused Filament Fabrication, this work developed a novel method by which to implement non-planar toolpath generation for a conventional three-axis machine. Utilising Boolean-based mesh approaches, arbitrary sinusoidal surfaces were used to generate non-planar tool-paths for the test specimens. To do so, a point cloud representing a non-planar surface was triangulated to form a surface mesh. A Boolean intersection between this non-planar surface mesh and the specimen mesh was then used to return the non-planar surface bounded by the geometry of the specimen; an edge traversal technique was then employed to obtain three-dimensional toolpaths. The frequency and amplitude of the non-planar sinusoidal surfaces were incrementally increased from the planar case until the geometric limits of the print-head were reached. Test specimens were then manufactured on a conventional three-axis machine and subject to a three-point bending test. There was a strong negative correlation between the flexural moduli of the specimens and the frequency and maximum tangential angle of their non-planar surfaces, while there was a strong positive correlation between the toughness of the specimens and the frequency of their non-planar surfaces. Non-planar specimens also exhibited more prominent yield points, and were better able to dissipate energy and resist crack propagation. A key finding was the significant increase in plastic strain exhibited by the non-planar samples; certain specimen types were able to withstand an average of 250% more strain in the plastic region, when compared to the planar samples, before significant progression of fracture. This is demonstrative of a notable improvement in ductility and reduction of brittleness. Non-planar samples also saw improvements in fracture toughness of up to 60%; however, this is perhaps not as significant as it could be, as greater tangential angles rotated the fibres away from their ideal colinearity with the normal stresses induced by bending. This work serves as a proof of concept for the feasibility of non-planar implementations of Fused Filament Fabrication, and provides a framework for future work aimed at non-planar alignment of material extrusion with stress tensors. It is anticipated that stress-vector fields will be used to generate non-planar surfaces, aligning material extrusion directions with principal stresses.
Conjugate Heat Transfer Analysis of Film Cooling With a Rib-Roughened Delivery Passage
Authors: Zhu Rui , Xie Gongnan , Li Shulei , Simon Terrence 
Published: January 2022

Abstract
Internal cooling and film cooling are two main cooling methods in modern gas turbines. They work together to protect the high-temperature components. This paper presents the results of a computational study on cooling performance for a flat plate with both film cooling and internal cooling using a conjugate heat transfer analysis. Three internal delivery channel geometries, smooth channel, channel roughened by square ribs, and channel roughened by crescent ribs, are studied with two film cooling geometries, cylindrical hole and sister holes. The respective conjugate cooling performances are compared. To help understand the interaction between film cooling and internal cooling, detailed flow and heat transfer characteristics are presented and discussed. Results show how overall cooling effectiveness is controlled by conjugate heat transfer of the two cooling schemes. Both film cooling effectiveness and internal cooling performance are influenced by the delivery channel geometry near the hole inlets. The sink flow effects of film cooling will enhance the heat transfer coefficient near the film cooling hole inlet, enhancing with stronger blowing ratio. At the same time, film cooling performance is affected by the internal channel as the flow inside the film cooling hole is influenced by the ribs near the hole inlets.
Investigation of Data-Driven Modeling in District Heating Substations
Authors: Feng Encheng , Wang Zaihua , Lin Xiaojie , Ying Guangyao 
Published: January 2022

Abstract
District heating system (DHS) is an important part of the urban energy system. But its large scale and numerous coupling variables bring many difficulties to its regulation and control. At present, rough regulation carried out by manual experience is hard to guarantee the quality of regulation, thus caused problems about heating comfort and efficiency. This paper proposes a data-driven temperature response prediction model to predict secondary loop supply temperature (SLST) considering the historical operating status of heating substation, valve opening, and weather conditions, etc. Non-time sequence models (MLP, XGBoost) and time sequence model (LSTM) prediction models established under different input and prediction lengths respectively are proposed and tested in this article. Results show that the prediction performance of the XGBoost model of 72 input steps and 12 prediction steps is best, with a root mean square error of 0.114°C. It reaches high prediction accuracy and can be used to guide the SLST control and primary loop valve opening (PLVO) regulation of heating substations.
Experimental and Computational Investigations of a Cylinder in Crossflow
Authors: Patterson Nathan J. , Venkateswaran Prabhakar 
Published: January 2022

Abstract
Engineers use three tools for analyzing fluid flows: analytical, experimental, and numerical. Thorough analyses involve all three tools to inform design decisions or postmortem investigations. However, few undergraduate fluid mechanics lab experiences expose students to the simultaneous application of these tools to a common problem. In this paper, we discuss a set of exercises and lab activities spanning multiple weeks to study a cylinder in a crossflow, providing students with their first experience in the use and comparison of analytical, experimental, and numerical tools for studying a fluid flow.
The analytical approach involves the solution derived for potential (inviscid) flow around a cylinder. While no novel examples or analytical approaches are used to teach this portion of the experience, this idealized flow solution is used as a comparison for experimental and numerical lab activities.
The experimental approach was initially designed to leverage low-cost microcontrollers and MEMS-based pressure sensors while reinforcing mechatronics and related programming content used in previous courses. Over four years of use and iteration, it has evolved from instructors supplying only a C++ library for the pressure sensors, a wiring diagram, and a rough programming framework to a simplified MATLAB interface that abstracts away many of the low-level commands required to complete the lab exercise. This range of interfaces and experiences allows instructors flexibility in their own implementation and lab goals. The latest iteration includes the use of a hot-wire anemometer, which must be calibrated by students, and allows for data capture and analysis of the resulting vortex street formation and Strouhal number.
The numerical approach uses a transient 2D planar analysis for flow around a cylinder and leverages a commercial computational fluid dynamics software, Ansys, for which there are free student versions. Students are provided with an instructor-built flow domain and mesh capable of providing a mesh-independent solution. Students choose solvers, set boundary conditions, run simulations, and process resulting data to compare with analytical and experimental results. A transient analysis is used to capture the effects of vortex formation on the coefficient of lift and to calculate and compare the system’s Strouhal number with that found from the physical experiment.
Students are challenged throughout the experience, from completing classic problems such as the lift force on a Quonset hut, to automating sensor positioning and data collection, to simulating a transient fluid flow. A concerted analysis of this relatively simple geometry affords students the opportunity to use analytical, experimental, and numerical tools to compare drag forces, pressure distributions, and transient flow behaviors.
Multi-Bolt Loosening Monitoring Using an Integrated Vibro-Acoustic Modulation Technique
Authors: Chen Minghao , Shen Yanfeng 
Published: January 2022

Abstract
This paper proposed an integrated vibro-acoustic modulation method (IVAM) for multi-bolt loosening monitoring. Numerical simulations and experiments of a single bolt model are initially conducted to illuminate the contact acoustic nonlinearity (CAN) and vibro-acoustic modulation (VAM) phenomenon. The finite element model considers the coupled field effects and the contact interface of the bolted joint. A pumping wave with a certain low frequency combined with a probing signal sweeping through the frequency range of 50 kHz to 100 kHz was implemented and verified to effectively trigger VAM on the bolted connection. A comprehensive damage index (CDI) associated with the linear energy and nonlinear CAN change due to the bolt looseness is then proposed to evaluate bolt looseness in a full life cycle. For further study, IVAM is applied on a complex multi-bolt connection part to locate and identify the loosened bolts. Several cases are investigated to analyze its performance. An intelligent self-verification mechanism is used to ensure the accuracy of the results. The proposed IVAM method with an outcome CDI matrix possesses great application potential for multi-bolt connection monitoring with high sensitivity and accuracy. This paper finishes with summary, concluding remarks, and suggestions for future work.
Phonon Scattering From Carbon Nanotube and Graphene Junction Under Mechanical Deformation
Authors: Durr Ian , Prates Matheus , Park Jungkyu 
Published: January 2022

Abstract
In the present study, we investigate single mode phonon scattering from a junction structure that is consisted of a (6,6) single walled carbon nanotube (SWCNT) and graphene under mechanical deformation using phonon wavepacket analysis. Longitudinal acoustic phonon mode is selected since it is the most important thermal energy carrier in carbon-based nanomaterials. The results show a large phonon scattering from the junction at all frequencies (0.5 ∼ 8 THz) and a significant amount of phonon energy (nearly 40%) is absorbed by the graphene floor between the SWCNT-graphene junctions. It is interesting to note that the phonon energy is better absorbed by the SWCNT-graphene junction while the amount of energy reflection is decreased when the structure is mechanically deformed. Additionally, the amount of energy reflection is higher at lower frequencies when the structure is mechanically deformed while the energy transmission becomes slightly higher at higher frequencies when the structure is deformed. Since high frequency phonons are populated more at high temperatures, it is expected that thermal transport through a deformed SWCNT-graphene junction becomes more efficient at high temperatures when compared to an undeformed SWCNT-graphene junction structure. However, thermal transport through a deformed junction is expected to be less efficient at low temperatures when compared to an undeformed junction structure since most of the phonons populated at low temperatures possess low frequencies (or long wavelengths). Group velocity is closely related to the energy absorption in the graphene floor between two SWCNT-graphene junctions; higher group velocity generally facilitates a better absorption by the graphene floor. The results obtained in the present research study will accelerate the development of futuristic electronics by providing a tool for synthesizing novel carbon nanostructures that ensure efficient thermal performance under mechanical deformation.
Production of Spherical Monodisperse Metal Powders by Means of the Plateau-Rayleigh Instability of a Liquid Metal Jet
Authors: Rehekampff Christoph , Rumschoettel Dominik , Schroeffer Andreas , Irlinger Franz , Lueth Tim C. 
Published: January 2022

Abstract
Additive Manufacturing is becoming increasingly important due to its possibilities. Processes such as selective laser melting, electron beam melting or binder jetting are used to manufacture industrial metal parts. The starting material for these techniques is metal powder with a particle size of approx. 30 to 100 microns, depending on the process.
Common processes for powder production are e.g. gas or water atomization. Disadvantages of these techniques are the non-spherical particles and the wide size distribution. Today’s Additive Manufacturing technologies require a high-quality, spherical powder with a narrow particle size distribution. After powder production, sieving or similar separation methods are required to sort the particles by size and achieve the desired size distribution. Particles that don’t have the desired size, have to be discarded. The high consumption of inert gas (argon) for gas atomization and the complex screening process result in high costs for the powder produced.
One alternative method for producing monodisperse and spherical particles from molten metal is droplet formation using Plateau-Rayleigh instability. This effect causes a liquid jet to break up into droplets of the same size. This breakup can be stimulated by modulating the jet velocity at a specific frequency. In free fall, the droplet shape becomes spherical due to the surface tension of the melt. In this way a monodisperse powder with spherical particles can be produced. The size of the generated particles depends on the modulation wavelength, while the instability has its greatest effect on a specific wavelength proportional to the jet diameter. By varying the modulation frequency during the process, precisely defined fractions of certain particle sizes can be generated. In this way, powders with tailor-made particle size distribution can be produced for specific applications.
In this work a droplet generator for molten solder (Sn 37%, Pb 63%) was designed, built and tested. Due to its temperature stability and mechanical properties, the body of the droplet generator was manufactured from the polymer PEEK (polyether ether ketone). The modulation was performed with a piezo stack actuator controlled by a waveform generator and an amplifier. A sapphire nozzle with a diameter of 200 microns was used for jet forming.
The droplet size, jet velocity and modulation frequencies were characterized and compared with theoretical calculations. Jet breakup and drop formation were investigated with a high-speed video camera. The generated particles were examined for size and shape by scanning electron microscopy. As a result, this work shows the potential of using this method to produce high quality powder for metal-based Additive Manufacturing technologies. Further work can be carried out to process metals with higher melting temperatures and to increase the throughput of the system.