bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Study of the Pressure Drop in a Flame Arrestor Using a Porous Media Model
Authors: Farah Hoden A. , Lu Frank K. , Griffin Jim L. 
Published: February 2021

Abstract
A numerical study of the flow characteristics of a crimped flame arrestor element was conducted using a porous media model. The porous zone was modeled using the Forchheimer equation. The Forchheimer equation was incorporated into the governing conservation equations as a momentum sink. A small-scale crimped flame arrestor element was tested to determine the empirical coefficients in the Forchheimer equation. The numerical simulation result using this porous media model was verified using experimental data. The flow characteristics of a four-inch detonation flame arrestor with the same crimp design as the small-scale sample, was simulated using the porous media model. The numerical simulation flow data were compared against experimental values and agreed to within five percent. The method used to determine the Forchheimer coefficients and the experimental test setup are described in detail. The application of the Forchheimer equation into the governing flow equations is presented. The challenges and limitation of numerical studies in flame arrestors applications are discussed. The simplification gained by using the porous media model in flame arrestor numerical studies is presented.
Numerical Simulation of Detonation Propagation in Flame Arrestor Applications
Authors: Farah Hoden A. , Lu Frank K. , Griffin Jim L. 
Published: February 2021

Abstract
A detail numerical study of detonation propagation and interaction with a flame arrestor product was conducted. The simulation domain was based on the detonation flame arrestor validation test setup. The flame arrestor element was modeled as a porous zone using the Forchheimer equation. The coefficients of the Forchheimer equation were determined using experimental data. The Forchheimer equation was incorporated into the governing equations for axisymmetric reactive turbulent flow as a momentum sink. A 21-step elementary reaction mechanism with 10 species was used to model the stoichiometric oxyhydrogen detonation. Different cases of detonation propagation including inviscid, viscous adiabatic, and viscous with heat transfer and a porous zone were studied. A detail discussion of the detonation propagation and effect of the arrestor geometry, the heat transfer and the porous zone are presented. The inviscid numerical model solutions of the detonation propagation parameters are compared to one-dimensional analytical solution for verification. The viscous solutions are qualitatively compared to historical experimental data which shows very similar trend. The effect of the porous media parameters on shock transmission and re-initiation of detonation is presented.
Roller Trace Design in Multi-Pass Conventional Spinning Based on Cylindrical Part
Authors: Zixuan Li , Xuedao Shu , Bohai Ye , Jitai Wang 
Published: February 2021

Abstract
Conventional spinning is a kind of ancient revolving process which controls the product’s shape by roller trace design. It is also widely used in civil, military, automobile, aerospace and other fields. Unlike the power spinning process, the roller trace used in conventional spinning is complex. Both thickness uniformity and crack defects are affected by it. However, roller trace design is still based on experience without a solid theoretical basis. This paper simulated five different roller trace curves: involute curve, circular curve, Bezier curve, conchoids and line. Experiments using superalloy GH3030 were conducted in conjunction with a multi-pass conventional spinning simulation model. Blank thickness variations, mandrel and roller forces of different roller traces in the first pass are analyzed and assessed through the verification experiments. The results suggest that the curve trace parameters play a key role on the product thickness uniformity. And the distribution of Bezier and conchoid roller traces is more uniform than the other traces. The axial force of mandrel is a very important factor in the design of tool load capability. Larger roller feed ratio and proper roller traces can reduce the thinning which may avoid the cracks.
Dynamic Response Near Critical Build Heights in Ultrasonic Additive Manufacturing
Authors: Lyle Dennis M. , Gibert James M. 
Published: February 2021

Abstract
Previous ultrasonic additive manufacturing (UAM) models ignore higher-order modes or do not simulate the entire weld cycle when studying the dynamics near critical height-to-width ratios. A multi-modal model was developed to study the dynamics near critical build heights. The cause for the critical height-to-width ratio is dynamic interaction between the substrate and sonotrode. As the build height approaches the critical height-width-ratio, the current model predicts a local maxima in the transverse velocity response directly under the moving load (simulated sonotrode excitation). This is validated by experimental observations from previous studies. However, the current model predicts that as the height is further increased, a maximum in the transverse velocity response occurs at a height-to-width ratio of 1.2 due to resonance of higher-order modes. This result indicates that a single mode-approximation is insufficient to describe the dynamics near critical build heights. In studying the time response for an entire weld cycle (1.5 s), the amplitude of the velocity response in the transverse direction varies greatly. This indicates that assuming a quasi-static or analyzing a short time period in a model excludes potential dynamics during an entire weld cycle (on the order of 1 s).
Investigating CRAC Flow Distributions Using an Under-Floor Wind Turbine for Data Center Efficiency
Authors: Song Zhihang , Yue Qiang 
Published: February 2021

Abstract
The phenomena of over-cooling commonly exist in data center thermal environment, resulting in a substantial waste of energy. Previous study has proposed a solution that implementing a wind turbine in a raised-floor data center by which the over-provisioned airflow can be utilized. The impingement of the computer room air-conditioner (CRAC) flow on the plenum walls (e.g., the floor slab) may yield key causes of the energy losses. Therefore, studying the effects of the wind turbine on the CRAC flow in the data center is necessary. Here, the data center and wind turbine were simulated and modeled using Computational Fluid Dynamics (CFD) package. In this research, the numerical measure of the pressure distributed on the floor slab was numerically measured as key observations. The positioning and axial induction factors of the wind turbine were treated as the major research parameters. The consequence illustrates that implementing a wind turbine with well-tuned axial induction factor and operating height might be capable of effectively decreasing the CRAC flow impingement and increasing the turbine power efficiency. This research may provide meaningful references for effective wind turbine applications for data center energy efficiencies.
Dynamics Analysis of Truss Deployment Mechanism With Imperfect Joint Considering Input Fluctuation
Authors: Bai Zhengfeng , Zhao Jijun , Shi Xin 
Published: February 2021

Abstract
Modern spacecraft usually has large deployment structure, which consisting of plenty of joints could produce undesirable dynamic responses when considering clearances in joints and driving input fluctuation. However, in the dynamic performance analysis of space deployment mechanism, the clearances and input fluctuation are always ignored. In this study, the dynamic responses of a flexible planar scissor-like truss deployment mechanism with imperfect joint considering clearance and input fluctuation are investigated using computational methodology. First, the mathematic model of clearance joint is established. The revolute clearance joint is considered as force constraint and the joint components of an imperfect joint with clearance are modeled as contact bodies. The normal contact force model of clearance joint is established using a continuous contact force model considering energy loss. The friction effect is considered using a modified Coulomb friction model. Then, the dynamics performances of the flexible planar scissor-like truss deployment mechanism with imperfect joint considering clearance and input fluctuation are presented and discussed. Different case studies for the scissor-like truss deployment mechanism with clearance are investigated considering driving input fluctuation. The simulation results show that the dynamic characteristics of the mechanism with clearance joint are changed more obviously when considering driving input fluctuation. Therefore, investigation implies that dynamics responses of the truss deployment mechanism are much worse when considering clearance joint and input fluctuation, which indicates that driving input fluctuation leads to more obvious degradation of the dynamic performance of the truss deployment mechanism with imperfect joint.
Additive Manufacturing With Ceramics
Authors: Cline Kjetil , LaFlam Andrew , Smith Logan , Nowicki Margaret , Ku Nicholas 
Published: February 2021

Abstract
The purpose of this project is to design a device that improves the performance of a ceramic additive manufacturing (AM) 3D printer constructed by Army Research Labs (ARL). ARL modified a standard LulzBot Taz 6 3D printer to print a ceramic slurry mixture of Boron Carbide (B4C) and Silicon Carbide (SiC) instead of plastic filament. Since these compounds are often used in body armor, ARL has been observing the effects on properties when these components are 3D printed. The current printer utilizes an auger in the print head to receive and mix the B4C and SiC slurries and extrude the combined slurry out of the print nozzle. The current design is limited in its ability to thoroughly mix the slurries during the printing process. Therefore, team Concept Creators has designed an improved auger that will increase the mixedness of the slurries, thus increasing the print quality of the composite specimen.
Numerical Simulation of Moisture-Heat Coupling in the Drying Process of a Multi-Temperature Zone Belt Dryer
Authors: Jia Hepeng , Wu Kai , Wang Yu , Sun Yu 
Published: February 2021

Abstract
The multi-temperature zone distributed drying method solves the problem of uneven drying of the conventional belt dryer. Multi-temperature zone belt dryer is widely used in the drying of aquatic feed products. This paper presents a numerical simulation method for multi-temperature zone belt dryer. The computational fluid dynamics (CFD) was applied to simulate the drying process of materials in a multi-temperature zone belt dryer. The user-defined function (UDF) was used to study the moisture-heat coupling drying process to predict the airflow filed of the multi-temperature zone belt dryer. The results showed that there were vortexes in each drying chamber so that airflow velocity distribution of the material layer was not uniform. However, the multi-temperature zone distributed drying method can maximize the drying efficiency through the bilateral distribution of the air inlet. The temperature distribution in each temperature zone was relatively uniform, and the temperature difference between the two sides of the feed layer was massive. The moisture content of the materials in each temperature zone was very uniform, the drying unevenness was less than 1.0%, and the dryer has excellent moisture content uniformity.
Investigation of Drilling Temperature in Relation to Machining Conditions and Cutting Time
Authors: Seif Charbel Y. , Hage Ilige S. , Baydoun Ahmad M. R. , Hamade Ramsey F. 
Published: February 2021

Abstract
Controlling drilling temperature and thrust forces play a significant role in reducing tool wear and improving machining efficiency. In this work, drilling experiments are set up to measure flank surface temperature via thermocouple sensor wires passed through the coolant holes of 10mm twist drill and brazed to the drill flank surface. The testing setup is an inverted drilling jig where the workpiece (Aluminum 6061-T6 rod) is chucked into the spindle of a vertical machining center. Thrust forces are co-measured using Kistler type 3-component plate dynamometer attached to the table. A design of experiment (DOE) using JMP-SAS/STAT® was adopted for selecting combinations of cutting speed and feed values that cover a wide range.
Drilling temperature rise and thrust forces are found to correlate with cutting conditions of feed (f), maximum cutting speed (V), and drilling depth (Dp). Nonlinear regression analysis produced correlating equations of flank temperature rise and thrust forces to conditions and follow a mechanistic power law of the form a1fa2Va3Dpa4 where a1, a2, a3 and a4 are identified via regression fitting.
On Symmetric Periodic Motions With Different Excitation Periods in a Discontinuous System With a Hyperbolic Boundary
Authors: Luo Albert C. J. , Liu Chuanping 
Published: February 2021

Abstract
In this paper, symmetric periodic motions with different excitation periods in a discontinuous dynamic system with a hyperbolic boundary are presented analytically. The switchability conditions of flows at the hyperbolic boundaries are developed. Periodic motions with specific mapping structures are predicted analytically, and numerical simulations of periodic motions are carried out. The corresponding G-functions are presented for illustration of motion switchability at the hyperbolic boundaries.
Design and Construction of a Four-Stage Travelling-Wave Thermo-Acoustic System for Power Generation
Authors: Ngcukayitobi Miniyenkosi , Tartibu Lagouge , Gqibani Samuel 
Published: February 2021

Abstract
This work describes the design and construction of a four-stage traveling-wave thermo-acoustic system for electricity generation. The thermo-acoustic conversion consists of using a sound-wave for the transfer of heat from a low to high-temperature medium or the use of heat energy to generate a sound wave. Both the absence of moving parts and the simplicity of thermo-acoustic systems make the technology sustainable for converting low-grade waste heat into acoustic power. Many existing studies have pointed out the acoustic-to-electric potential of thermo-acoustic systems. Hence in this work, a thermo-acoustic system has been developed. The traveling-wave system has a total length of 3 560 mm. The distance between each thermo-acoustic engine is 640 mm. Each engine stage had four cartridge heaters used to generate the heat required. A commercial loudspeaker was used to convert sound into electricity. The minimum temperature difference necessary to induce a voltage at the terminals of the loudspeaker was approximately 200°C. The four-stage traveling-wave system generated the highest output voltage of 4.218 V.
Bayesian Optimization of Energy-Absorbing Lattice Structures for Additive Manufacturing
Authors: Hertlein Nathan , Vemaganti Kumar , Anand Sam 
Published: February 2021

Abstract
Additive manufacturing has enabled the production of intricate lattice structures that meet stringent design requirements with minimal mass. While many methods such as lattice-based topology optimization are being developed to design lightweight structures for static loading, there is a need for design tools for achieving dynamic loading requirements. Lattice structures have shown particular promise as low-mass energy absorbers, but the computational expense of nonlinear finite element analysis and the difficulty of obtaining objective gradient information has made their optimization for impact loading particularly challenging. This study proposes a Bayesian optimization framework to determine the lattice structure design that provides the best performance under a specified impact, while managing the structure’s mass. Considering nonlinear effects such as plasticity and strain rate sensitivity, a 2D explicit finite element (FE) model is constructed for two lattice unit cell types under impact, and parameterized with respect to geometric attributes such as height, width, and strut thickness. These parameters are considered design variables in a minimization problem with an objective function that balances part volume with a common injury metric, the head injury criterion (HIC). Penalty values are assigned to designs that fail to absorb the entire impact. Design for additive manufacturing (DFAM) constraints including minimum feature thickness and maximum overhang angle are applied to ensure that the optimal design can be manufactured without subsequent manual refinement or post-processing. The best optimizer hyperparameters are then carried over into larger optimization problems involving lattice structures. Future work could include expanding this framework to allow for lattice structure designs with arbitrary boundaries.
Periodic Motions and Bifurcations of a Periodically Forced Spring Pendulum Varying With Excitation Amplitude
Authors: Guo Yu , Luo Albert C. J. 
Published: February 2021

Abstract
In this paper, the semi-analytical method of implicit discrete maps is employed to investigate the nonlinear dynamical behavior of a nonlinear spring pendulum. The implicit discrete maps are developed through the midpoint scheme of the corresponding differential equations of a nonlinear spring pendulum system. Using discrete mapping structures, different periodic motions are obtained for the bifurcation trees. With varying excitation amplitude, a bifurcation tree of period-1 motion to chaos is achieved through the bifurcation tree of period-1 to period-2 motions. The corresponding stability and bifurcations are studied through eigenvalue analysis. Finally, numerical illustrations of periodic motions are obtained numerically and analytically.
Analytical Modeling of Outward Solidification With Convective Boundary in Cylindrical Coordinates
Authors: Xu Minghan , Akhtar Saad , Zueter Ahmad F. , Alzoubi Mahmoud A. , Sasmito Agus P. 
Published: February 2021

Abstract
Solidification consists of three stages at macroscale: subcooling, freezing and cooling. Classical two-phase Stefan problems describe freezing (or melting) phenomenon initially not at the fusion temperature. Since these problems only define subcooling and freezing stages, an extension to characterize the cooling stage is required to complete solidification. However, the moving boundary in solid-liquid interface is highly nonlinear, and thus exact solution is restricted to certain domains and boundary conditions. It is therefore vital to develop approximate analytical solutions based on physically tangible assumptions, like a small Stefan number. This paper proposes an asymptotic solution for a Stefan-like problem subject to a convective boundary for outward solidification in a hollow cylinder. By assuming a small Stefan number, three temporal regimes and four spatial layers are considered in the asymptotic analysis. The results are compared with numerical method. Further, effects of Biot numbers are also investigated regarding interface motion and temperature profile.
Failure Analysis of Coil Racks in a Batch Annealing Furnace Using Finite Element Methods
Authors: Walla Nicholas J. , You Hua , Zhu Xinyu , Zhou Chenn Q. , Liddick Matthew 
Published: February 2021

Abstract
In this work, a series of finite element method simulations were performed on cooling racks used for the loading and unloading of steel coils in a batch annealing furnace. Normal furnace operations were simulated using ANSYS Thermal FEA and ANSYS Mechanical FEA to reproduce the thermal and structural loads experienced by the racks, as well as additional lifting forces representing removal by forklift after annealing. In addition to warping found due to uneven heating from the radiative elements of the furnace, severe stress leading to failure was identified on the base of the racks from the lifting force. These results correspond with failures seen in the actual units. The simulation data was used for design adjustments to reduce the damage from the above sources.
Freeform 3D-Printing of Pure Ceramics
Authors: Mahmoudi Mohammadreza , Burlison Scott R. , Moreno Salvador , Minary Majid 
Published: February 2021

Abstract
Polymer derived ceramics (PDC’s) offer a unique opportunity to 3D-print ceramics; however, 3D printing of such polymers require it to be combined with specialized light-sensitive agents and layer-by-layer crosslinking using an optical beam due to their low viscosity. Here, three-dimensional printing of ceramics enabled by dispensing the preceramic polymer from a nozzle inside a yield stress fluid is being demonstrated. The printed parts are crosslinked in the same gel. After crosslinking process, the printed parts are taken out of the gel and prepared for high temperature pyrolysis process that converts the cured parts to ceramic. The specially designed gel was three orders of magnitude more viscous than the preceramic polymer at no shear, which provided a stable medium during the whole process for maintaining the shape of the printed material and prevented possible instabilities. The SEM images of the cross section of the specimens showed that the printed material was dense and without any apparent porosity or cracks. Statistical analysis on the mechanical properties of the printed preceramic polymer specimens revealed that the printed specimens had characteristic strength (∼257 MPa).
Damage Detection in Composite Structures via Scanning Laser Doppler Vibrometry Using Linear and Nonlinear Ultrasonic Wave Features
Authors: Cen Mingjing , Shen Yanfeng 
Published: February 2021

Abstract
This study presents the modeling and experimental investigation of damage detection and evaluation methods based on the linear and nonlinear features of ultrasonic guided waves while they interact with possible structural damage sites. Such wave damage interaction features are visualized via the full field imaging capability of SLDV. First, numerical modeling is conducted to develop an in-depth understanding of the mechanism behind the wave damage interactions. A coupled-filed transient dynamic finite element model is constructed with a simulated delamination area. The modeling of Contact Acoustic Nonlinearity (CAN) is realized by defining the contact surfaces at the delamination area. The linear ultrasonic features such as the trapped modes as well as the nonlinear features such as the mixed frequency response are illustrated using the numerical simulation. Based on the numerical study, experimental investigations are further conducted. Experiments are performed to explore linear ultrasonic technique for damage quantification. For the linear case, the detection utilizes a short tone burst in both spatial and temporal domain, generated by a Piezoelectric Wafer Active Sensor (PWAS); the trapped wave energy and a directional vector field technique are adopted to visualize an impact damage in a carbon fiber composite plate. The nonlinear detection methodology combines a continuous resonant low frequency harmonic pumping wave with a high frequency tone burst probing wave, simultaneously generated by two PWAS transducers on both sides of the specimen to take advantage of the mixed nonlinear interactions between the vibroacoustic waves and the structural damage. This study shows that both linear and nonlinear ultrasonic techniques possess great application potential for the damage detection and quantification in composite structures. The paper finishes with summary, concluding remarks, and suggestions for future work.