bluuebunny/crossref_metadata_2025 huggingface dataset:
Using Wireless Pasco Smart Carts to Demonstrate Vibration Principals
Authors: Hekman Keith
Published: January 2022

In a typical vibrations course, students learn mathematical models to predict the response of vibratory systems. Often, students have trouble visualizing what they are calculating with the equations. The goal is to have a visual example of the motions that are represented in the equations. Because of in-person meeting restrictions, demonstration experiments were recorded before class time, which allowed the analysis to be completed before class. A Pasco smart cart system was used to create the demonstrations. The carts are connected to the computer via Bluetooth and can measure force, position, and acceleration. Using the force sensor, the spring constant and magnetic damping coefficient are determined. Demonstrations were created for one and two degree of freedom systems. The response was shown for systems with and without magnetic damping. Free and forced responses were measured in all the cases. For single degree of freedom systems, higher-order components of the input were explored and using the convolution integral to calculate the response. At the end of the semester, students took a survey to learn of their experience. Overall, students strongly appreciated the visual representation of the modeling equations.
Parametric Evaluation of AM Enabled Sinusoidal Heat Transfer Surfaces Through Numerical Simulations
Authors: Duggirala Vyas , Reddy Venkateswara , Muley Arun , Stoia Michael , Ek Garrett
Published: January 2022

Heat transfer enhancement and design innovation of thermal devices are needed to accommodate growth in heat duty from avionics, electric propulsion, environmental control, and engine systems of current and future aircraft. Additive manufacturing (AM) technology enables exploration of new heat transfer surfaces and complex flow passage geometries to achieve the higher convective heat transfer rates, while minimizing pressure loss, and compactness needed for next generation thermal devices. Effective use of these innovative designs requires the development of new thermo-hydraulic design databases, which include variations in heat exchanger geometries due to the influence of AM processes. The present work deals with performance evaluation of AM-enabled sinusoidal wavy heat transfer surfaces by 3D conjugate heat transfer analysis using Computational Fluid Dynamics (CFD). Numerical simulations were carried out for two thermal boundary conditions consisting of constant wall temperature and constant heat flux in laminar and turbulent flows with a Reynolds number range of 300 to 5000 for varying fin geometry parameters. Numerical results are validated with available literature data and presented in terms of isothermal friction factors and Nusselt numbers. Variation in local heat transfer coefficients and temperatures are discussed to gain insights into the fluid flow and associated heat transfer mechanisms. The parametric study on channel waviness showed that a decrease in wavelength resulted in a relatively large increase in friction factor relative to growth in Nusselt number, which was addressed by rounding of the flow channel corners.
Influence Study on End-Face Quality of Square Billet in Plate Cross Wedge Rolling
Authors: Xia Yingxiang , Shu Xuedao , Chen Taizhu
Published: January 2022

Cross wedge rolling (CWR) is an advanced forming technology in which the billet is mainly cylindrical shape. It has the advantages of high efficiency, energy-saving and material saving. Due to the difficulty to obtain large-size cylindrical billet, the CWR is limited to form large parts to some extent. This paper breaks through the limitation of traditional cylindrical billets and innovates square billets for plate cross wedge rolling. Based on the movement model and rotation condition of plate cross wedge rolling, the finite element simulation of square billet is carried out to clarify the formation mechanism of shaft end concave heart. It is found that a retaining wedge added on the die with reasonably wedge parameters can obtain small concave heart and flat surface of the shaft, which effectively improve the end-face quality. And the concave is mainly caused by the inconsistent flow velocity between the surface metal and core metal. The process parameters are optimized by the four-factor three-level orthogonal experiment and the influence order of each parameter on the end-face quality is: L > β > α > θ. The optimal parameter combination for ensuring the end-face quality of square billet in plate cross wedge rolling is: forming angle 32°, spreading angle 8°, wedge angle 6.5°, wedge distance 8mm. A reasonable combination of process parameters can effectively control the end concavity and improve the end-face quality of the rolled product, which has important reference value and engineering significance for the realization of near-net forming of square billet in plate cross wedge rolling.
Statistical Energy Analysis of Vibrating Structures With Energy and Entropy
Authors: Hough Elise , Sotoudeh Zahra
Published: January 2022

We present a complete thermodynamic analogy of statistical energy analysis (SEA) using entropy and energy for both linear and nonlinear coupled systems. We will use Khinchin’s Entropy as our statistical entropy definition from statistical mechanics. This framework allows for the restrictive assumptions of linearity to be removed from this analysis method. We will use the classical definition of entropy to relate entropy to Vibrational Temperature. Using Khinchin’s statistical definition of entropy for a vibrating system, we will define a Vibrational Temperature as a function of energy. Hence, we will derive all that is necessary to construct the SEA power flow equation along with the transient coupling loss factors without any linearity assumption. With this method one can expand SEA to nonlinear transient coupled systems. We will verify our proposed method using Monte Carlo Simulation and published analytical closed form solutions.
Neural Differential Equations for Inverse Modeling in Model Combustors
Authors: Su Xingyu , Ji Weiqi , Zhang Long , Wu Wantong , Ren Zhuyin , Deng Sili
Published: January 2022

Monitoring the dynamics processes in combustors is crucial for safe and efficient operations. However, in practice, only limited data can be obtained due to limitations in the measurable quantities, visualization window, and temporal resolution. This work proposes an approach based on neural differential equations to approximate the unknown quantities from available sparse measurements. The approach tackles the challenges of nonlinearity and the curse of dimensionality in inverse modeling by representing the dynamic signal using neural network models. In addition, we augment physical models for combustion with neural differential equations to enable learning from sparse measurements. We demonstrated the inverse modeling approach in a model combustor system by simulating the oscillation of an industrial combustor with a perfectly stirred reactor. Given the sparse measurements of the temperature inside the combustor, upstream fluctuations in compositions and/or flow rates can be inferred. Various types of fluctuations in the upstream, as well as the responses in the combustor, were synthesized to train and validate the algorithm. The results demonstrated that the approach can efficiently and accurately infer the dynamics of the unknown inlet boundary conditions, even without assuming the types of fluctuations. Those demonstrations shall open a lot of opportunities in utilizing neural differential equations for fault diagnostics and model-based dynamic control of industrial power systems.
A Numerical Study of the Effect of Surface Coverage on the Filtration Performance of Hair Arrays
Authors: Tanikella Sri Savya , Jones Nathan D. , Dressaire Emilie
Published: January 2022

Biological filtration systems offer a sustainable alternative to existing engineered solutions. In this computational work, we seek to optimize the surface coverage by an array of hairs to capture particles in channels. A variety of aquatic organisms rely on arrays of hairs to interact with their fluidic environments. The hair functionality can vary from sensing to smelling, filtration to flow control depending on the species considered. Among those organisms are filter-feeders that rely on suspension-feeding, one of the most widespread feeding mechanisms and one of the oldest. Baleen whales are filter-feeders that catch their prey by using the baleen, a complex structure composed of plates and bristles in their mouth. The hairs are hollow cylindrical structures with a diameter of a few hundred micrometers that can extend over tens of centimeters. The baleen filters out the prey while letting the seawater through. The baleen is composed of flexible and elongated structures whose properties fit the feeding habits of the whale.

The porosity of the structure depends on the flow feature. Effectively, the flow can tune the filter properties, which sets biological filters apart from their engineered counterpart. Previous mechanical studies have shown that an array of hairs can either act as a sieve, allowing all the fluid to flow through it, or as a rake, forcing the fluid to flow around it instead. As the speed increases, the behavior shifts from rake to sieving for a given hair spacing. From a filtration perspective, the rake regime is not favorable as particles do not enter the array. For a fixed fluid velocity, the flow transitions from rake to sieve as the spacing between the hairs in the array increases. Our recent work has also demonstrated that the confinement of the channel influences the sieve to rake transition. The filtration mechanisms that filter-feeder organisms use to capture food particles exhibit complex fluid-structure interactions that have yet to be leveraged in engineered systems. To guide the development of hair-covered surfaces capable of trapping particles in channel flows, we investigate how different geometric factors affect the fluid transport and capture of particles by the array. In previous work, a small number of hairs, typically 25, were considered. Here, we vary the array geometry, the Reynolds number of the flow, and the surface coverage to study the transport through this confined porous structure. We compare arrays based on their optimal efficiency and the (sub-optimal) operating conditions which make the filter versatile.
Cell Behavior in Flow Passing Through Micro Machined Gap
Authors: Hashimoto Shigehiro , Uehara Shogo
Published: January 2022

Does each cell show specified behavior (deformation and alignment) as it passes through the micro-gap in the flow channel? A gap with a rectangular cross section (10 μm high, 0.4 mm wide, and length 0.1 mm long) was manufactured in the middle part of the flow path by photolithography technique. Myoblasts (C2C12: mouse myoblast cell line) sparsely suspended in the medium were used for the test. Deformation of each cell passing through the micro-gap was observed with an inverted phase contrast microscope. From the contour of the image of each cell passing through the gap, several parameters were analyzed: the two-dimensional projected area, the degree of deformation by ellipse approximation, and the alignment of the major axis of the deformed cell. The experimental results show that the alignment of each cell tends to deviate from the flow direction as the larger projected two-dimensional area.
Vibration Isolation in Continuous Beam Networks
Authors: Rai George , Rahn Christopher D. , Smith Edward , Marr Conor
Published: January 2022

This paper investigates antiresonance in continuous dynamic systems consisting of beam networks with inherent inertial coupling. An analytical non-dimensional transfer function model is developed to predict the isolation behavior of a cantilever beam with a tip mass. It is shown that beam network isolators exhibit a good degree of versatility at the design level. The static stiffness and the isolation forces are scalable at the design level, the dynamic stiffness can also be tuned to achieve any force reduction ratio in the absence of damping. Furthermore mutlifrequency isolation is possible due to the nature of continuous systems, thus, multi-mode isolation frequencies can be tuned closer to each other. Isolation frequency clustering is also possible by tuning the beam-mass components. As a proof of concept, the analytical results are validated with an experimental study whereby the shear force is recorded at the root of a cantilever beam with a tip mass that is subject to harmonic point force excitation. The experimental results show that the root shear response at the first isolation frequency is reduced by 78% after the addition of a tip mass equivalent to 230% of the beam mass.
Strain-Coupled Fluidlastic Circuits Inside Metal Additive Manufactured Structures
Authors: Saxena Ankit , Rai George , Lanari Valentin , Rahn Christopher D. , Manogharan Guhaprasanna
Published: January 2022

Fluidlastic dampers, isolators and absorbers are stand alone components used to reduce vibrations in many civil, mechanical and aerospace structures. This research demonstrates how additive manufacturing can integrate fluidlastic circuits inside a metal part. An example device with relatively simple monolithic construction consists of two chambers separated by a thin membrane that is connected to the upper chamber by a bridge compliant mechanism. The chambers are filled with fluid and are connected by a long thin channel inertia track that coils around their periphery. Elastic strain deflects the bridge causing the membrane to bulge into the upper chamber. This causes a pressure gradient that drives the fluid flow from the upper chamber to the lower chamber through the inertia track. Enabled by additive manufacturing, design parameters such as chamber dimensions, constitutive material, fluid viscosity, etc. can be easily tailored to provide targeted resonance over a desired frequency range. Experimental results provide evidence of fluid pumping at the membrane’s first resonant frequency.
Influence of Welding Sequence on Residual Stress Evolution in SUS304/Q235 Bimetallic Clad Plate Butt-Welded Joints
Authors: Zhu Min , Zhang Yansong , Zheng Qiao , Wu Wei , Qian Weifang , Wang Baosen
Published: January 2022

Residual stress prediction and controlling is important for structural integrity assessment of weldments. In current work, finite element and experimental methods were integrated to study the influence of welding sequence on the SUS304/Q235 bimetallic clad plate joints during multi-layer and multi-pass welding. The results show that the peak residual stress values on flyer plate surface are weakly affected by welding sequences but the width of high surficial longitudinal stress area of joint with base layer welded first is bigger. Meanwhile, welding sequence has a great influence on the longitudinal residual stress evolution law inside joints. When base seam layer is welded first, the highest stress concentration appears in the transition layer. However, it would be transferred into the first base seam layer due to martensite phase transformation when flyer seam layer is welded first. Residual stress controlling in the bimetallic clad plate joint should attract more attention from researchers.
A Time-Frequency Domain Adaptive Control Approach for Vibration of Active Magnetic Bearing System
Authors: Yao Xuan , Chen Zhaobo
Published: January 2022

Active magnetic bearings (AMBs) have several advantages such as non-contact and active control, and are getting more applications in rotating machinery. Various control strategies have been applied and designed for this nonlinear system with complex rotor dynamics. Most control schemes are in time domain, while the control in frequency domain, which is also essential for stability, is rarely considered. In this paper, a time-frequency domain control approach is proposed for AMB-rotor system. The control scheme is implemented using wavelet theory and deep learning theory. The controller consists of 2 main parts: a filter bank for discrete wavelet transform (DWT) to obtain time-frequency signal, and a deep neural network (DNN) for nonlinear adaptive control. A 4-DOF AMB-rotor system is analyzed and its model is established. The rotor dynamics are simulated and the results are compared. Simulation results demonstrate that the proposed approach has an obvious control effect in improving precision in time domain and stability in frequency domain. This research provides a new adaptive control approach for AMBs, and this approach can also be adopted in other multi-dimension vibration control, especially in multi-frequency applications.
Shock Wave Heating: A Novel Method for Low-Cost Hydrogen Production
Authors: Akbari Pejman , Copeland Colin D. , Tüchler Stefan , Davidson Mark , Mahmoodi-Jezeh Seyyed V.
Published: January 2022

This study introduces a new method of methane pyrolysis in a rotary chemical reactor using wave rotor technology. The patented technology has been developed by New Wave Hydrogen, Inc. (New Wave H2 or NWH2) . The concept introduces an efficient method of hydrogen production driven by shock wave gasdyanmics, with no direct CO2 emissions and no water use. The New Wave Reformer is based on wave rotor designs where unsteady shock waves are generated within channels arrayed around a rotating drum. As in a typical wave rotor wave cycle, a sharp pressure increase occurs behind a reflected shock wave, resulting in a proportional increase in gas temperature. This temperature amplification can be used to initiate a thermal decomposition reaction in gaseous constituents. Past studies have proven that a wave reformer with onboard reactions can reform heavy hydrocarbon gases into lighter hydrocarbon products. The current NWH2 study explores how a wave rotor can employ pressurized natural gas as a driver gas for compression heating of a low-pressure hydrocarbon fuel inside the channels of a wave reformer, resulting in the decomposition of methane into hydrogen and carbon black. This study first reviews past efforts ranging from conceptual patents to experimental studies utilizing different wave cycles for rapid heating of gases in gas-phase chemical reactions. Examples of such reactions include the formation of acetylene from methane and the formation of nitric oxide from air. In ongoing research, the authors introduce a wave cycle that uses a dual-stage gas compression process designed to prolong reaction time within the channels, addressing a key factor in high methane-to-hydrogen conversion. The process has been modeled numerically using a customized version of the Tüchler-Copeland experimentally-validated quasi-one-dimensional CFD code. The computational results provide data used in the prediction of flow fields inside the channels and at the inflow/outflow ports of the reactor.
Research on Soft Electrostatic Adsorption Unit Driven by SMA
Authors: Jiang Jing , Niu Chenxu
Published: January 2022

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

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

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

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

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

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

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

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

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

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

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

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.
Modeling and Simulation of Convective Heat Transfer Caused by a Rotating Disk
Authors: Ruiz David , Mueller Donald , Abu-Mulaweh Hosni
Published: January 2022

In this study, computational fluid dynamics (CFD) software is used to model and simulate a smooth disk rotating in a still fluid. The primary quantity of interest is the convective heat transfer coefficient. Laminar, transition, and turbulent flow regimes are considered. To ensure that the physical characteristics of the situation are properly captured, the velocity and temperature profiles of the fluid are qualitatively and quantitatively compared to results reported in the literature. By analyzing the velocity and temperature profiles, an estimate for the proper size of the computational domain within the CFD software is obtained. If the computational domain is too small, the velocity and temperature profiles are affected; hence, the calculation of the convective heat transfer coefficient is influenced by the size of the computational domain.

Two methods — the global rotation method (GRM) and the local rotation (or sliding) method (LRM) — are used to obtain results for the convective heat transfer coefficient. The global rotation method involves conversion of the specified angular velocity into a mass-distributed force. The local rotation method involves the creation of a secondary body that rotates. The secondary body can cause inaccuracies to appear when discretizing the domain. These inaccuracies cause the local rotation method to be less predictable than the global rotation method.

An extensive and systematic verification and validation study of the two methods is performed with validation achieved by comparing the calculated values to published correlations and measured results. Both methods demonstrate agreement with the expected heat transfer coefficient value by maintaining a difference of less than 3% for low angular velocities. At higher angular speeds, the global rotation method maintains less than a 3% difference, once an appropriate mesh is established and the turbulent parameters are set correctly.

Over the entire range of parameters considered, the global rotation method is best suited to model and simulate a singular disk rotating in still air. The global rotation method does not require the introduction of a secondary body and yields predictable and uniform convergence to published values as the mesh size is reduced.

Relationships between accuracy, grid size, and computational effort are reported. Recommended laminar and turbulent parameter settings are discussed. The results of this fundamental study provide insight and guidance into the proper modeling and simulation of both low-speed and high-speed rotating machinery and equipment.
Constitutive Modeling of Viscoelastic Photo-Adaptable Thermally Activated Shape Memory Polymers
Authors: Prasad Aayush , Moon Swapnil , Cui Fangda , Rao I. J.
Published: January 2022

Shape memory polymer (SMPs) are a class of smart materials that have the ability to retain multiple temporary shapes and recover original shapes as they exhibit deformation in response to external stimuli. The shape change in these polymers can be triggered using different stimuli like temperature, light, water, pH, magnetism, and their mechanisms can be easily altered. SMPs are capable of displaying multiple temporary and one permanent shape by either creating a multiphase system or by undergoing a very broad thermal transition. SMPs and their composites are also easy to manufacture, and complex structures can be 3D printed with multimaterials by controlling various geometric parameters. Their applications are diverse and found in various fields such as transportation, energy generation, deployable structures, clothing, healthcare, etc. It is therefore important to model the behavior of such a material. This work discusses the behavior of a thermally activated subclass of SMPs in which the temporary shape is fixed by a crystalline phase and a light activated subclass of SMPs in which the temporary shape is fixed by photo-reversible covalent crosslinks. Light activated SMPs (LASMPs) ease the temperature limitations faced by thermally activated SMPs while making remote activation possible, which opens an even wider range of applications. The thermo-mechanical behavior of such copolymers is simulated using a framework based on the theory of multiple natural configurations while incorporating the viscoelastic effects in a rate type model. The model is applied to different boundary value problems related to homogeneous deformations such as uniaxial extension of dual and triple shape memory polymers under controlled stress and strain conditions. The results are consistent with experimental observations and show how the complicated thermo-mechanical behavior and shape memory effect (SME) are influenced by parameters like temperature, external stress, crystallinity and bond formation.
High Strain Rate Impact on Carbon Nanostructures Using Molecular Dynamics Simulations
Authors: Prates Matheus , Durr Ian , Park Jungkyu , Espitia Giovanny , Peterson Braden
Published: January 2022

In the present study, we researched the behavior of graphene experiencing high strain rate impacts by employing molecular dynamics simulations. Graphene with various thicknesses are selected for the study. A silver particle is designed to impact these carbon nanostructures with pre-specified speeds. The amount of energy absorbed during impacting graphene is calculated from the change in the kinetic energy of the silver particle before and after the impact. Graphene is shown to have excellent flexibility and its structural integrity is retained under a high strain rate impact. At an impact velocity of 4 km/s, a single layer of graphene absorbed 6.5 keV without any damage in the structure. The impact energy used to fracture graphene is shown to increase linearly with an increase in the thickness of graphene; the absorbed energy during breaking seven layers of graphene was 23 keV when the impact velocity was 10 km/s. It was also found that temperature does not affect the impact energy required to break a graphene sheet. The results obtained in the present research study will be used to accelerate the development of futuristic strong light-weight materials for military applications.