bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design for Additive Manufacturing: Effectiveness of Unit Cell Design Guidelines As Ideation Tools
Authors: Boyd I’Shea , Fazelpour Mohammad 
Published: January 2020

Abstract
The periodic cellular materials are comprised of repeatable unit cells. Due to outstanding effective properties of the periodic cellular materials such as high flexibility or high stiffness at low relative density, they have a wide range of applications in lightweight structures, crushing energy absorption, compliant structures, among others. Advancement in additive manufacturing has led to opportunities for making complex unit cells. A recent approach introduced four unit cell design guidelines and verified them through numerical simulation and user studies. The unit cell design guidelines aim to guide designers to re-design the shape or topology of a unit cell for a desired structural behavior. While the guidelines were identified as ideation tools, the effectiveness of the guidelines as ideation tools has not been fully investigated. To evaluate the effectiveness of the guidelines as ideation tools, four objective metrics have been considered: novelty, variety, quality, and quantity. The results of this study reveal that the unit cell design guidelines can be considered as ideation tools. The guidelines are effective in aiding engineers in creating novel unit cells with improved shear flexibility while maintaining the effective shear modulus.
A Molecular Dynamic Study of Nano-Fracture of C3N
Authors: Shishir MD Imrul Reza , Tabarraei Alireza 
Published: January 2020

Abstract
The recently synthesized two–dimensional C3N is a graphene–like two–dimensional material with remarkable electronic, optoelectronic, thermal, mechanical and chemical properties. Molecular dynamics (MD) simulation is used to investigate the fracture properties of C3N. Cracks with different geometry and orientations are used to investigate how the crack tip configuration and orientation impact the fracture properties of C3N. The results show that regardless of their initial orientation, at microscale cracks always tend to propagate along a zigzag direction. The MD results are used to estimate the critical energy release rate of C3N. The critical energy release rate of both armchair and zigzag cracks increases with the decrease of crack length when the crack length is less than 7 nm. The critical energy release rate for armchair and zigzag cracks longer than 7 nm is respectively 10.16 J/m2 and 8.52 J/m2 which are significantly lower than those of graphene.
Effects of Curvature and Architecture on Ballistic Performance of UHMWPE Helmets
Authors: Zhang Timothy G. , Vargas-Gonzalez Lionel R. , Gurganus James C. , Satapathy Sikhanda S. 
Published: January 2020

Abstract
Ballistic impact experiments were conducted on three types of Ultra-high-molecular-weight polyethylene (UHMWPE) helmets. The three types of helmets had the same geometry, but different fiber orientations in the rear layers. The test data were used to evaluate the effects of architectures. Five impact locations were chosen to understand the effects of impact locations and curvatures. The experimental data from flat and cylindrically curved UHMWPE panels were also used to compare with the helmet test data.
High Thermo-Mechanical Stability in Polybenzoxazine Aerogels
Authors: Malakooti Sadeq , Qin Guoqiang , Mandal Chandana , Sotiriou-Leventis Chariklia , Leventis Nicholas , Lu Hongbing 
Published: January 2020

Abstract
Aerogels are three-dimensional networks of nanoparticles with high specific surface area and high porosity. Following the significant improvement on the mechanical strengths and ductility of traditional aerogels with polymer cross-linking (i.e., X-aerogels), the emergence of pure polymeric aerogels has enabled unprecedented aerogel applications such as ballistic armor protection, which is quite surprising for such low-density materials. However, generally low glass transition temperatures (Tg) of polymeric aerogels hinder their structural applicability at service temperatures above their Tg temperatures. Thereby, developing novel polymeric aerogels with high Tg temperatures is crucial for high-temperature structural applications. As phenolic resins, polybenzoxazines are heat-resistant and mechanically strong with high glass transition temperatures. In this study, polybenzoxazine aerogels have been successfully synthesized, and their mechanical properties at different densities and elevated temperatures have been investigated. High thermo-mechanical stability has been observed over the entire temperature range of interest (i.e., below 250 °C) for their quasi-static compressive properties such as Young’s modulus and compressive strength. Moreover, the storage and loss moduli in shear of the aerogels have been studied at different temperatures and frequencies. The strong mechanical performance of these aerogels at elevated temperatures makes them an important, inexpensive, and advanced material for high-temperature applications, competitive with significantly more expensive polyimides.
Curvature Change Analysis of SMART Fibers Used for Temperature Adaptive Insulation
Authors: Ripa Cameron , Latulippe Andrew , Sun Hongwei , Fossey Stephen , Drew Christopher 
Published: January 2020

Abstract
A new method of characterizing the curvature change in thermally adaptive fibers is introduced in this paper. Based on the same principle as bi-metallic strips commonly found in thermostats, multi-component polymer fibers can be created to change their geometrical form in response to a temperature change. This works by creating fibers from two or more materials that have a mismatched Coefficient of Thermal Expansion (CTE). A temperature change leads to a change in curvature of these fibers. When fibers interact in an insulation batting structure, a temperature change leads to a thickness change in the insulation. While these fibers have visually been observed to function, there was no method to quantitatively characterize their curvature performance. This paper introduces a method that can be used to quantify fiber performance by tracking change in curvature over a specific temperature range. This is accomplished by suspending fibers on the surface of a liquid bath and changing the bath temperature. Digital images of the fiber are taken at different temperatures and analyzed using software to determine the radius of curvature. Absolute change in curvature was found to be as high as 0.5% per degree °C from 20 to −20°C for certain samples. A trend was also noted between higher initial curvature and lower overall performance. Digital image correlation was further used to investigate the time-dependence relationship of fiber curvature. Future experiments can be performed with this setup to characterize and compare curvature change performance of different fibers accurately.
Investigation of Process Induced Variations in PolyJet Printing With Digital Polypropylene via Homogeneous 3D Tensile Test Coupon
Authors: Tomar Ravi Pratap Singh , Ulu Furkan I. , Kelkar Ajit , Mohan Ram V. 
Published: January 2020

Abstract
The capability of additive manufacturing (AM) of making the monolithic, multi-material structure allow the fabrication of complex parts with varying mechanical properties. Many AM processes and equipment utilize proprietary material stocks from equipment vendors. A better understanding of the digital material mixing behavior to form traditional material configurations during AM is critical.
Many jetting-based AM processes also have the capability to print different material gradient and build them layer by layer in a specific concentration of two or more base materials. This paper investigates the tensile strength and mechanical behavior of these digital materials formed by mixing or multi-material interfaces fabricated by material jetting.
Further, due to the flexibility of orientating the digital design in AM, a part can be created in any orientation; however, processing-induced variation affects the performance of parts, as the way AM forms part is different from traditional manufacturing that leads to many artifacts. These artifacts affect the mechanical properties and behavior of final parts formed in AM. To eliminate the process-induced effect that exits in traditional 2D test coupon, this paper evaluates a homogenized 3D configuration test coupon which reduces the geometric effects in AM, that we had recently proposed and investigated.
Development of 3-D Printed Optically Clear Rigid Anatomical Vessels for Particle Image Velocimetry Analysis in Cardiovascular Flow
Authors: Stanley Nicholas , Ciero Ashley , Timms William , Hewlin Rodward L. 
Published: January 2020

Abstract
In recent years, blood flow analysis of diseased arterial mock vessels using particle image velocimetry (PIV) has been hampered by the inability to fabricate optically clear anatomical vessel models that realistically replicate the complex morphology of arterial vessels and provide highly resolved flow images of flow tracer particles. The aim of the present work is to introduce an approach for producing optically clear rigid anatomical models that are suitable for PIV analysis using a common 3-D SLA inkjet printing process (using a Formlabs Form 2 3-D printer) and stock clear resin (RS-F2-GPCL-04). By matching the index of refraction (IOR) of the working fluid to the stock clear resin material, and by printing the part in a 45-degree print orientation, a clear anatomical model that allows clear visualization of flow tracer particles can be produced which yields highly resolved flow images for PIV analyses. However, a 45-degree print orientation increases the need for post processing due to an increased amount of printed support material. During post processing, the part must be wet sanded in several steps and surface finished with Novus Plastic Polish 3 Step System to achieve the final surface finish needed to yield high quality flow images. The fabrication methodology of the clear anatomical models is described in detail.
Cold Spray Deposition of Pure Titanium Coating Onto High Strength Substrate With Ultra-High Bond Strength
Authors: M. Jafarlou Davoud , Ferguson Gehn , Nardi Aaron , Champagne Victor , Grosse Ian R. 
Published: January 2020

Abstract
Cold spray (CS) is a relatively new spray coating technology which has opened up a new avenue for deposition of bulk coatings with a thickness in the millimeter range. The unique bonding mechanism of the CS process facilitates deposition of commercially pure titanium (CP-Ti) on a wide range of substrates including high strength alloys. In this paper we present a multi-stage bond coat deposition process using a mixture of ultra-hard ceramic beads and CP-Ti prior to the top CP-Ti coating deposition to produce a coating layer with promising bond strength. In addition, three combinations of the carrier gas temperature (450, 540, and 550 °C), and pressure (2.5 and 3.8 MPa) were considered for maximizing bond strength. The relationship between bond strength and surface roughness was also examined. The shear test results indicated a significant high bond strength of approximately 195 MPa for the gas pressure of 3.8 MPa and temperature of 450 °C owing to the newly introduced bond coat deposition method. The relatively high bond strength is explained by the beneficial effect of multi-stage bond coat prior to the deposition of the bond coat. The results also indicated a tradeoff between bond strength and obtained surface roughness.
Thermal Property Measurements of Si µ-Cantilever Beams Using the Suspended Thermoreflectance Technique
Authors: Sarkar Dipta , Oxandale Samuel W. , Hieber Tyler J. , Baboly M. G. , Leseman Zayd C. 
Published: January 2020

Abstract
Thermoreflectance is a common technique to measure thermal properties of micro/nano devices. Most thermoreflectance techniques use a pump-probe scheme with lasers to heat the sample and analyze the temperature. The limiting characteristics of most of these techniques are that they can probe the temperature at only one spot on the sample, assume a value for either heat capacity or thermal conductivity to find the other, and require a semi-infinite substrate. In this paper, a new technique is described, the Suspended ThermoReflectance (STR) technique, which allows measurement of thermal conductivity by probing multiple points along the length of a suspended micro/nano-scale sample. This technique involves a pump laser for heating the tip of a suspended μ-cantilever Si beam and a probe laser to scan the temperature along the μ-cantilever’s length. Thermal conductivity is obtained by applying the heat diffusion equation for the temperature gradient along the beam length. 2.9 μm thick Si μ-cantilever samples are tested over a range of temperatures from 20–300K. It is found that thermal conductivity of the silicon varies from 28 W/mK to 80 W/mK.
Structural Dynamic Testing Results for Air-Independent Proton Exchange Membrane (PEM) Fuel Cell Technologies for Space Applications
Authors: Gilligan Ryan P. , Jakupca Ian J. , Smith Phillip J. , Bennett William R. , Guzik Monica C. , Kacher Henry 
Published: January 2020

Abstract
In 2016, the National Aeronautics and Space Administration (NASA) Advanced Exploration Systems (AES) project office funded testing at the NASA Glenn Research Center to evaluate the maturity of the Proton Exchange Membrane (PEM) fuel cell technology and its viability for supporting launch vehicle and space applications. This technology evaluation included vibration, reactant purity, and vacuum exposure sensitivity testing. The evaluation process did not include microgravity testing. This paper discusses the vibration sensitivity testing of two air-independent fuel cell stacks provided by different vendors to assess the ability of currently available fuel cell stack hardware to survive the projected random vibrational environment that would be encountered in an upper stage launch vehicle. Baseline performance testing was utilized to quantify stack performance and overboard leak rate at standard atmospheric conditions in order to provide a reference for posttest comparison. Both fuel cell stacks were tested at a random vibration qualification level of 10.4 grms for five minutes in each axis. Low-level sinusoidal sweeps were conducted before and after each random vibration level run to see if any significant change in resonances were detected. Following vibration facility testing, the baseline performance testing was repeated. Test results demonstrated no measurable change in fuel cell electrochemical or mechanical performance, indicating that the two evaluated PEM fuel cell stacks may be suitable for space applications pending microgravity testing.
Numerical Study on the Interfacial Modification Effects of Soy Protein on Poly(Vinylidene Fluoride)
Authors: Zheng Zhuoyuan , Xin Chen , Li Yumeng 
Published: January 2020

Abstract
The application of bio-degradable green materials is a rising global trend during the past decades for the sake of environment protection and sustainable development. Soy protein-based biomaterial is a promising candidate to replace the petroleum-based synthetic materials and was proved to be an effective functional modifier for polymers from our previous studies. Molecular dynamic (MD) simulation is implemented in this study to provide insights in understanding the underlying mechanisms. 11S molecule is chosen as a representative of soy protein, and three different denaturation processes are applied, including heat denaturation at two temperatures and the breaking of disulfide bonds. It is observed that by controlling the denaturation conditions, the hydrophobicity of the protein molecule is manipulated: high temperature denaturation can increase the exposed area of hydrophilic residues; whereas, by breaking the disulfide bonds, the hydrophobic residues of the molecules can be largely exposed. Besides, the mechanisms of using protein as functional modifier to tune the structures of the hydrophobic Poly(vinylidene fluoride) (PVDF) polymer (amorphous and β-crystal phases) are studied. S-S debond protein is found to favor the formation of amorphous PVDF; whereas, high temperature denatured one has stronger interactions with β phase.
CFD Analysis of Flow Structures in a Mixing Chamber
Authors: Cândido Sílvio , Páscoa Marques José , Tomé António , Amorim António , Weber Stefan Karl 
Published: January 2020

Abstract
Special mixing chambers are usually used to perform scientific experiments or for routine industrial production processes. This is the case, typically, of fan mixers in a baffled tank. Mixing chambers comprise, among other alternative elements, two counter-rotating fans at the bottom and top. These will eventually allow a mixing effect on the chamber with an adequate level of uniformity. Herein a computational flow simulation is performed for the mixing conditions of air and SO2 inside the chamber used in the CLOUD experiment, by studying in detail the flow structures and uniformity inside the chamber. This Unsteady Navier-Stokes computation is performed using the kω-SST and SAS turbulence models. A first validation step is performed by using an experimental test case, comprising a T-junction geometry, that performs the mixing of air and N2. Following this validation step a detailed analysis of the flow structures inside the 3D chamber is conducted, and specific insights are given regarding the flow uniformity. A detailed analysis of the computed mixing flow structures for the SST and SAS turbulence models is also described. It is shown that the SAS model captures with more detail the macro and meso-mmixing process with an accuracy of, at most, 6%. This value can be further reduced to values around 2% by resorting to high density meshes, with the associated computational burden.
Experimental Investigation of Spiral Wound Module Under Pressure Retarded Osmosis Process
Authors: Vives Luis , Elsharqawy Mostafa H. , Quiñones-Bolaños Edgar 
Published: January 2020

Abstract
The performance of a spiral wound module operating under pressure retarded osmosis (PRO) is measured experimentally with a feed water back pressure. The module has a diameter of 0.1 m, a length of 1.02 m, and total membrane surface area of 7.45 m2 capsulated in a stainless-steel pressure vessel. The module is commercially designed for a reverse osmosis (RO) system however, a feed water outlet is added, and a back pressure is applied to adapt it for the PRO process. The experimental results of the spiral wound PRO module with a back pressure in the feed water side showed low power density values (about 0.35 W/m2) compared with those commonly found in the literature, demonstrating the geometric inefficiency of RO modules for the PRO process.
The Effect of Time Delay on 3D Printed Part Strength
Authors: Gay Jasmine , Moore Carl , Pollard Marquese , Dickens Tarik , Wang Hui 
Published: January 2020

Abstract
We are investigating the impact on 3D printed part strength when the extruder is positioned using articulated robotic arms in place of a traditional x-y gantry-style system. One of our printer designs is called the DeXter printer [1] which uses two selective compliance assembly robotic arms (SCARA) to position dual extruders. An advantage of using dual robotic arms is that two extruders can move independently drastically reducing build times, or the second arm can perform additional operations like segment stimulation during the build process [2]. In either case the arms require a collision avoidance process to prevent them from colliding in the part space. A possible drawback of the collision avoidance requirement is that it can result in a time delay along some sections of the layer which, due to cooling, could have adverse effects on the part strength. This research aims to determine how this cooling time will affect the strength of ABS extruded parts.
We performed tensile tests on 3D printed part samples for which we altered the g-code to produce a variable time delay during the printing process. Our control sample had a zero-dwell time, and as we increased dwell time we found that the ultimate tensile strength (UTS) did decrease.
Combining FEA and Field Measurement Techniques for Dynamic Machinery Foundation Design
Authors: Cunningham Seth , White Benjamin A. , Poerner Nathan W. 
Published: January 2020

Abstract
Proper foundation design is an essential component in the design process of many types of rotating machinery. Most foundations are designed for static loading, however dynamic foundation design is often overlooked or considered a secondary check. Failing to consider the dynamics of the foundation during the design phase can result in excessive machinery vibrations resulting in failures, forced shutdowns, and expensive in-situ repairs. Foundation dynamics are commonly assessed using finite element analysis (FEA) during the design phase with modal and forced response analyses; however the interactions of machinery, piping, foundation, and soil create a potentially nonlinear system with many degrees-of-freedom. In many applications, it is necessary to design the mechanical natural frequencies of the foundation to avoid excitation mechanisms of the machinery. With modern variable speed machines, accurate prediction of the mechanical natural frequencies is often required to place them in narrow frequency bands between operating orders. These systems are inherently difficult to accurately model, however combining FEA modeling with field measurement techniques allows the possibility of field “tunable” foundation designs. For example, pile foundations can be designed with alternative pile configurations to be connected during commissioning based on the results of modal testing. Modal and vibration data collected on-site can also be used to calibrate the frequencies and mode shapes predicted by the model. This calibrated model is then used to evaluate the effects of proposed changes to the skid and suggest modifications to fix or reduce the problems in existing machinery foundations.
On the Global Dynamics of Complex Networks
Authors: Yang Chun-Lin , Suh C. Steve 
Published: January 2020

Abstract
Complex networks are nonlinear dynamic systems. The dynamics of a complex network is the local dynamics of all ensemble at the microscopic level, coupled with the global dynamics at the macroscopic level. At the macroscopic level, the connections between each ensemble contain energy that couples the ensembles to evolve toward the state of consensus. Both the local and global dynamics are nonlinear and time-dependent. The level of coupling between each ensemble pair is affected by the energy that characterizes the connection of each ensemble pair. As the connection energy is time-dependent, consequently, the relation between each ensemble pair is dynamic as well. Since the energy of each connection can be different, the dynamic distribution of the connection energy is a key factor for defining the global dynamics of a complex network. While statistical entropy can be applied to define the distribution of energy among all connections, the global dynamics of a complex network can be defined by regulating the entropy of the connection energy distribution. As the global dynamics of a complex network can be defined by entropy, the correlation between statistical entropy and network dynamics is investigated.