bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Properties of 3D Printed Fiber Reinforced Thermoplastic
Authors: Sanei Seyed Hamid Reza , Lash Zack , Servey Josh , Gardone Frank , Nikhare Chetan P.
Published: January 2020

3D printed composites is a relatively new and untested market in the composites industry. 3D printing in general is becoming a widely used manufacturing method because of its ease, versatile capabilities, and consistency. Recent improvement in 3D printing enables 3D printing of composites fibers in any given direction. In this study, continuous carbon fiber onyx samples were manufactured using Markforged X7 3D printers. Samples with three different fiber orientations were manufactured to determine all elastic properties. The results show that while the properties are lower than high strength CFRPs, there is high potential for the use of 3D printed composites upon improving the matrix properties as well as the bonding between fiber and matrix.
Anisotropy Oriented Tolerance Analysis of Composite Assembly With T-Maps Method
Authors: Wang Hua , Yan Chen , Yu Junyang
Published: January 2020

Anisotropy is an outstanding characteristic of the composite parts, and should be considered during the course of the tolerance analysis. The paper presents a tolerance analysis method for composite elevator assembly using T-Maps method, mainly concerning the variations originated from the anisotropy of the composite materials. The composite elevator is composed of the forward spar, the skin panels, and the ribs. Variations of the composite forward spar and the composite panels in different directions are represented by the T-Maps. Mating clearances of the composite spar and the metallic joints are mapped to the hypothetical Euclidean space. Since the different axial deviations are represented in the same Euclidean point-space, anisotropy oriented tolerance analysis of the composite parts assembly could be conducted with more accurate results. This procedure is found to be effective for anisotropy oriented tolerance analysis. The assembly of the composite elevator is investigated intensively by the proposed method. The procedures outlined in the paper are quite general and can be used for tolerance analysis of any anisotropic parts assembly process.
In-Situ Fatigue Prediction of Direct Laser Deposition Parts Based on Thermal Profile
Authors: Seifi Seyyed Hadi , Tian Wenmeng , Yadollahi Aref , Doude Haley , Bian Linkan
Published: January 2020

Additive manufacturing (AM) is a novel fabrication technique which enables production of very complex designs that are not feasible through conventional manufacturing techniques. However, one major barrier against broader adoption of additive manufacturing processes is concerned with the quality of the final products, which can be measured as presence of internal defects, such as pores and cracks, affecting the mechanical properties of the fabricated parts. In this paper, a data-driven methodology is proposed to predict the size and location of porosities based on in-situ process signatures, i.e. thermal history. Size as well as location of pores highly affect the resulted fatigue life where near-surface and large pores, compared to inner or small pores, significantly reduces the fatigue life. Therefore, building a model to predict the porosity size and location will pave the way toward building an in-situ prediction model for fatigue life which would drastically influence the additive manufacturing community. The proposed model consists of two phases: in Phase I, a model is established to predict the occurrence and location of small and large pores based on the thermal history; and subsequently, a fatigue model is trained in Phase II to predict the fatigue life based on porosity features predicted from Phase I. The model proposed in Phase I is validated using a thin wall fabricated by a direct laser deposition process and the Phase II model is validated based on fatigue life simulations. Both models provide promising results that can be further studied for functional outcomes.
Design and Modeling of Semi Compliant Prosthetic Knee Joint
Authors: Warnix Trevor , Lin Hongkuan , Lowder M. Loraine , Tekes Coskun , Tekes Ayse
Published: January 2020

This paper presents the design phases and modeling of multi axial compliant prosthetic knee joint comprised of rigid and flexible members providing a better performance than traditional spring-loaded rigid multilink joints. Mechanism consists of monolithic compliant five bar incorporating large deflecting flexure hinges, two rigid body representing the upper and lower legs, translational spring and flexure joints simulating ankle motion. Dynamical modeling is studied by integrating pseudo rigid body modeling of small-length flexure hinge method and Lagrange equations under the assumption that link 2 (left base link) is fixed and link 3 is rotated quasi-statically at constant speed. Torsional stiffness of ankle springs is obtained by using MSC Adams simulations. Initial prototype is built by 3D printing the parts using polylactic acid (PLA) filament. Mechanism is potentially suitable for pediatric prosthetic knee systems due to its simple design, versatility and light weight.
High-Cycle Fatigue Behavior of Type 4340 Steel Pressurized Blocks Including Mean Stress Effect
Authors: Badr Elie A. , Ishak Joanne
Published: January 2020

Mean stress effects in pressurized steel blocks were examined under constant amplitude fatigue loading. The tests were performed to provide experimental data needed to study the effect of mean stress on fatigue lives of subject specimen, and to substantiate the use of analytical expressions to account for the mean stress. The mean stress was the result of subjecting the specimens to an autofrettage pressure which induced compressive residual stresses at the crossbore intersection of the specimens. Fatigue tests were carried out under both tensile and compressive mean stress levels. Test results were compared to several mean stress accounting relationships such as the Smith-Watson Topper, Bergmann and Seeger, modified Goodman, Gerber and Soderberg. Test results indicated that the modified Goodman equation is favorable in accounting for the effect of both tensile and compressive mean stresses on fatigue life (up to a compressive mean stress to ultimate stress ratio of −0.2). The behavior under compressive mean stress to ultimate stress ratio of less than −0.2 indicated that a linear correction relationship was required.
Optimization of Fixed PV Panel “Tilt” Angles for Maximal Energy Harvest Considering Year-Around Sky Coverage Conditions
Authors: Gwesha Ammar Omar , Alfulayyih Yasir Mohammed , Li Peiwen
Published: January 2020

In order to maximize the electrical energy harvested by photovoltaic panels in a setup with fixed angles, it is important to get the angle optimized. In the present work, sunlight availability or sky coverage conditions of year-long period based on ten years’ data are counted in the modeling to optimize the PV panel tilt angles targeting for the maximal energy in a year. The analysis uses precise sunray calculation models. The energy harvested in every 6 minutes by a PV panel is summated for the daily time period from sunrise to sunset when the sun elevation angles are above 5 degree, with the sky-coverage factor multiplied. The results show that the annual solar energy received by a PV solar panel tilted with a fixed angle equal to the local latitude (at Tucson AZ, USA) could reach 2297 kWh/m2 under 10-year averaged sky coverage conditions. However, the gain in the yearly solar energy harvest is expected to be about 4.28%, 7.06%, and 8.42% higher if a PV panel is inclined optimally according to two-season, four-season, and monthly adjustments, respectively, compared to the optimized life-long fixed angle.
Design of a Free Piston Stirling Engine Power Generator
Authors: Li Ruijie , Gao Yuan , Yanaga Koji , Qiu Songgang
Published: January 2020

Free Piston Stirling Engine is an external combustion engine, which can use diversified energy resources, such as solar energy, nuclear energy, geothermal energy, biomass, industrial waste heat etc. and is suitable for the remote area power generation due to the advantage of robustness, durability, reliability, and high efficiency. In this work, a Free Piston Stirling Engine has been designed based on the numerical simulation results and previous experimental experience. Direct Metal Laser Sintering method has been adopted for the manufacturing of the key components including the displacer cap, displacer body, piston housing, cold heat exchanger, and regenerator. One dimension analysis using Sage software has been conducted. The designed engine has a power output of 65W with the hot and cold end temperature is 650°C and 80°C respectively, and charge pressure is 1.35 MPa. Finite Element Method has been used to analyze the structural stress of the engine, which is operated at the high temperature and high pressure, to determine if it is able to tolerate the operating condition designed by the Sage according to the Section VIII Division 2 of the ASME Boiler and Pressure Vessel (BPV) Code.

In addition, Computational Fluid Dynamics (CFD) method has been used to investigate the flow distribution in heat exchangers (heat acceptor, regenerator, and heat rejecter), as the heat exchanger performance affect the engine performance greatly. Considering the large mesh number, a quarter of the heat exchangers have been investigated, in order to reduce the mesh numbers and accelerate the calculation speed.
A Methodology for Modelling Tugger Train Systems Using Modelica
Authors: Veiga João , Sousa João , Machado José , Silva João , Machado Toni , Silva Pedro
Published: January 2020

In this paper, the authors present a methodology to develop a modular model of a tugger train system using Modelica language. The presented system is composed by a tugger and three passive trolleys. The model allows to estimate the path of the trolleys relative to the path of the tugger vehicle and it can be used to estimate the maximum velocities when in a curve.

A review of common vehicle models from the literature is presented. Some concepts of the Modelica language are introduced in order to support the model of the shown system.

The presented model is a simplified representation of the system for planar motion developed in Modelica language using the Open Modelica OMEdit software2. The vehicle models are modelled by custom classes and linked with the aid of blocks from the Open Modelica standard library. This model was mainly used to understand the behavior of the vehicles during U-turns, estimate the minimum turning radius and maximum velocities during the turn.

The methodology allows a modular approach combining vehicle and multibody modelling.
Assessment of Eddy-Viscosity Turbulence Models on Flow in a Wheelhouse
Authors: Nabutola Kaloki L. , Boetcher Sandra K. S.
Published: January 2020

Six different turbulence models were used to simulate the flow within the wheelhouse of a simplified body. The performance of each model was evaluated by comparing the results to data collected from wind tunnel experiments. The performance of large eddy simulation (LES) and detached eddy simulation (DES) is largely dependent on the time step and grid size to accurately resolve turbulent eddies. The standard k–ω and k–ω SST models deviated the most from the experimental data. The standard k–ε model was found to produce the most consistent results which matched experimental data for the simplified body and wheel.
Drag Reduction of Ground Vehicles Using Air-Injected Wheel Deflectors
Authors: Nabutola Kaloki L. , Boetcher Sandra K. S.
Published: January 2020

Numerical simulations of flow modification devices on a simplified ground vehicle are conducted. A parametric study on the size and distance upstream of conventional wheel deflectors is conducted on a simplified body at a Reynolds number of 1.6 × 105 to observe the impact on drag coefficient. Results show that wheel drag is decreased as the height of the conventional wheel deflector is increased. Additionally, the further the conventional wheel deflector is from the wheelhouse, the more sensitive the wheel is to changes in drag coefficient. The conventional wheel deflectors are then replaced by air-jets which are used to manipulate the flow field in and near the wheelhouse to reduce the wheel drag of the simplified body. The air-jet successfully decreases the wheel drag and it is observed that the closer the air-jet is to the wheelhouse the less impact it has on the single wheel drag, but the greater the impact on the overall drag of the simplified body.
High-Power Fuel Cell Systems Fueled by Recycled Aluminum
Authors: Godart Peter , Fischman Jason , Hart Douglas
Published: January 2020

Presented here is a novel system that uses an aluminum-based fuel to continuously produce electrical power at the kW scale via a hydrogen fuel cell. This fuel has an energy density of 23.3 kWh/L and can be produced from abundant scrap aluminum via a minimal surface treatment of gallium and indium. These additional metals, which in total comprise 2.5% of the fuel’s mass, permeate the grain boundary network of the aluminum and disrupt its oxide layer, thereby enabling the fuel to react exothermically with water to produce hydrogen gas and aluminum oxyhydroxide, an inert and valuable byproduct. To generate electrical power using this fuel, the aluminum-water reaction is controlled via water input to a reaction vessel in order to produce a constant flow of hydrogen, which is then consumed in a fuel cell to produce electricity. As validation of this power system architecture, we present the design and implementation of two example systems that successfully demonstrate this approach. The first is a 3 kW emergency power supply and the second is a 10 kW power system integrated into a BWM i3 electric vehicle.
3D Printing and Stretching Effects on Alignment Microstructure in PDMS/CNT Nanocomposites
Authors: Herren Blake , Gu Tingting , Tang Qinggong , Saha Mrinal , Liu Yingtao
Published: January 2020

The alignment of high aspect ratio reinforcing nanoparticles within a polymer matrix can have significant effects on the mechanical, electrical, and thermal properties of the nanocomposite. Therefore, in order to tailor the properties of the composite, it is imperative to develop novel methods to control the alignment of these filler particles in various polymeric matrices. This paper reports a unique approach to alter the alignment of carbon nanotubes (CNT) within polydimethylsiloxane (PDMS) nanocomposites using 3D printing technology. A line of the reinforced PDMS resin is printed on a PDMS substrate using direct ink writing technology, which can produce alignment in the print direction depending on printing parameters, the loading of the reinforcing particle, and the rheology of the ink. Then, the substrate is stretched and placed in an oven to cure the printed nanocomposites line with increased alignment in the stretch direction. These two techniques have the advantage of simplicity over other techniques and can efficiently manufacture nanocomposites with the alignment of nanoparticles. Optical microscopy will be used to quantify the alignment within the printed line. Electrical and mechanical properties will be tested to determine the effects of the different alignments within the elastomer. The ability to control the alignment of elastomeric CNT composites is advantageous for the growing field of polymer-based electronics.
Highly Porous Shape Memory Nanocomposites for Applications in Biomedical Devices
Authors: Luo Jishan , Kunkel Robert , Wang Jingyu , Bohnstedt Bradley N. , Saha Mrinal , Liu Yingtao , Lee Chung-Hao
Published: January 2020

This paper presents the novel development of highly porous carbon nanotube (CNT)/shape memory polymer (SMP) nanocomposites for potential endovascular treatment of intracranial aneurysms (ICAs). Intracranial aneurysm is a cerebrovascular disorder that can significantly weaken the wall of a brain artery, resulting in a localized dilation of the blood vessel with risk of rupture and subarachnoid bleeding. Current therapeutic options include surgical clipping and endovascular coil embolization. Clipping of intracranial aneurysms is invasive, and, therefore, it has gradually been replaced by non-invasive endovascular embolization. Recent studies have shown that aneurysmal recanalization and incomplete occlusion are still emerging clinical challenges in endovascular coil embolization. Therefore, there is an urgent need to develop new medical devices and surgical procedure to treat intracranial aneurysms with improved long-term outcomes.

CNT/SMP nanocomposites are fabricated by directly coating CNTs on sugar particles before fabricating the sugar template for porous nanocomposites. Pristine SMP prepolymer is infiltrated into the pores of sugar template. All the sugar is dissolved in water after the fully curing of PDMS, resulting in SMP based nanocomposites with well dispersed CNTs. The porous nanocomposites are characterized to identify key parameters, such as electrical resistivity and shape memory capability. A resistive-heating mechanism is developed to trigger shape recovery of the nanocomposites. The results of this work will lay a solid foundation for our subsequent development of new personalized biomedical devices to treat ICAs using a catheter-based endovascular embolization procedure.
Computational Design of Microstructures With Stochastic Property Closures
Authors: Acar Pınar
Published: January 2020

The present work addresses a stochastic computational solution to define the property closures of polycrystalline materials under uncertainty. The uncertainty in material systems arises from the natural stochasticity of the microstructures and the variations in deformation processes, and impacts the performance of engineering components by causing unanticipated anisotropy in properties. We utilize an analytical uncertainty quantification algorithm to describe the microstructural stochasticity and model its propagation to the volume-averaged material properties. The stochastic solution will be integrated into linear programming to generate the property closure that shows all possible values of the volume-averaged material properties under the uncertainty. We demonstrate example applications for stiffness parameters of a-Titanium, and multi-physics parameters (stiffness, yield strength, magnetostrictive strain) of Galfenol. Significant differences observed between stochastic and deterministic closures imply the importance of considering the microstructural uncertainty when modeling and designing materials.
Effect of Phase Change Material on Temperature in a Room Fitted With a Windcatcher
Authors: Abdo Peter , Huynh B. Phuoc , Braytee Ali , Taghipour Rahil
Published: January 2020

Global warming and climate change have been considered as major challenges over the past few decades. Sustainable and renewable energy sources are nowadays needed to overcome the undesirable consequences of rapid development in the world. Phase change materials (PCM) are substances with high latent heat storage capacity which absorb or release the heat from or to the surrounding environment. They change from solid to liquid and vice versa. PCMs could be used as a passive cooling method which enhances energy efficiency in buildings. Integrating PCM with natural ventilation is investigated in this study by exploring the effect of phase change material on the temperature in a room fitted with a windcatcher. A chamber made of acrylic sheets fitted with a windcatcher is used to monitor the temperature variations. The dimensions of the chamber are 1250 × 1000 × 750 mm3. Phase change material is integrated respectively at the walls of the room, its floor and ceiling and within the windcatchers inlet channel. Temperature is measured at different locations inside the chamber. Wind is blown through the room using a fan with heating elements.
Remaining Useful Life Prediction Based on Spindle Load and Cutting Process Parameters in Machining
Authors: Krishna Ankur , Muhammed Bilal
Published: January 2020

Tool wear increases machining resistance, part dimensional inaccuracy and machining vibration. Tool wear monitoring and Remaining Useful Life (RUL) prediction of the tool during machining operation will assist a machine operator to provide tool wear compensation at the right time and plan the tool change activity. These aspects become significantly important for economical and quality production. This work focuses on a physics and data-based approach for monitoring cutting tool wear state and Remaining Useful Life (RUL) during a machining operation by adapting a well-known empirical wear-rate equation. The constants in the model are estimated based on machine heuristics which depends on the tool-machine-workpiece combination. The proposed model takes real-time spindle power and machining process parameters as inputs, which are obtained directly through querying the CNC controller. Therefore, it does not require the mounting of any external sensors on the CNC machine tool. Hence, the proposed method is a more economical and convenient way to predict tool wear and RUL in a machining shop floor. The model is validated from experimental data and it can capture the progression of tool wear and RUL of the tool at any point of time during a machining operation. Since the model captures the physics of tool wear and machining heuristics, it is more robust than a purely data-based model.
Semi-Analytical Approach for Derivation of an Equivalent Modal Friction-Damping Ratio and its Application in a Self-Excited Drilling System
Authors: Kulke Vincent , Ostermeyer Georg-Peter , Tergeist Mathias , Hohl Andreas
Published: January 2020

In this article, friction-based damping principles and their suitability for dampening self-excited torsional oscillations in drill strings are investigated. Analytical and semi-analytical solutions based on a modally reduced model are derived by approximating the dynamic behavior with the Harmonic Balance method. The results are validated through time-domain simulations, and limitations of the method are shown. The method enables consideration of the damper position that determines the local amplitudes experienced by the damper. In analytical solutions, the damper location is represented by the local value of the mass-normalized mode shape. The analytical approach can be used to calculate and optimize an equivalent damping ratio for every torsional mode based on the parameters and placement of the friction damper. The provided damping can then be used to estimate the stability of critical torsional modes.
Digital Twin: Concept of Hybrid Programming for Industrial Robots — Use Case
Authors: Kuts Vladimir , Sarkans Martinš , Otto Tauno , Tähemaa Toivo , Bondarenko Yevhen
Published: January 2020

Modern Industrial Robot (IR) programming process is mainly performed by using three different methods — manual, offline, and online programming. Each of these methods has various advantages and disadvantages. Prominent automotive industries often use a combination of them, as there is no way to avoid one or another form of programming on one factory. However, the use of a combination of different programming methods is time-consuming and demands the operator’s presence on site for reconfiguration of the IR. The primary goal of this study is to introduce and test the concept of a hybrid IR programming method, which combines both: offline and online robotic cell design, programming, and re-configuration methods. Testing of this method is based on fully synchronized robotic cell’s Digital Twin (DT), developed in Industrial Virtual and Augmented Laboratory of Tallinn University of Technology. Usage of the virtual replica allows to plan and program robotic cell on the means of telepresence and interfere with the predefined path of the robot by online programming method. Moreover, this approach reduces the time for robotic cell design and re-programming, enables to minimize downtime of the robotic cell on the factory shop floor. Included Virtual Reality (VR) environment allows simulating a full-scale operator presence on site. Thus, the proposed approach supports an immersive and safe environment for the IR and similar equipment programming purposes.
Development of a New Stoichiometric Equilibrium-Based Model for Wood Chips and Mixed Paper Wastes Gasification by ASPEN Plus
Authors: Safarianbana Sahar , Unnthorsson Runar , Richter Christiaan
Published: January 2020

Wood and paper residues are usually processed as wastes, but they can also be used to produce electrical and thermal energy through processes of thermochemical conversion of gasification. This study proposes a new steady state simulation model for down draft waste biomass gasification developed using the commercial software Aspen Plus for optimization of the gasifier performance. The model was validated by comparison with experimental data obtained from six different operation conditions. This model is used for analysis of gasification performance of wood chips and mixed paper wastes. The operating parameters of temperature and moisture content (MC) have been varied over wide range and their effect on the high heating value (HHV) of syngas and cold gas efficiency (CGE) were investigated. The results show that increasing the temperature improves the gasifier performance and it increases the production of CO and H2 which leads to higher LHV and CGE. However, an increase in moisture content reduces gasifier performance and results in low CGE.
Explosion Testing of Relief Valves for Underground Refuge Alternatives
Authors: Homer John , Whitson Ashley , Whisner Bruce , Yonkey Jeff , Yantek Dave
Published: January 2020

Federal regulations require refuge alternatives (RAs) to be installed in underground coal mines. RAs provide miners safe shelter from life-threatening environments during a mine emergency when escape is not possible. Built-in-place (BIP) RAs require ventilation systems that supply breathable air to occupants. Relief valves provide critical functions to the ventilation system by limiting pressure within the RA, allowing ventilation air to exit while preventing contamination ingress, and protecting occupants from external pressure due to mine explosions. As such, relief valves for BIP RAs must be developed and tested to ensure pressure relief, adequate airflow, and the ability to withstand a 103-kPa (15-psi) blast overpressure with a duration of 0.2 seconds.

The National Institute for Occupational Safety and Health (NIOSH) has published research on relief valve opening pressures and airflow rates. However, the ability of RA relief valves to withstand a survivable mine explosion must be demonstrated. As such, NIOSH researchers tested the ability of RA relief valves to withstand overpressure representative of a survivable mine explosion. For this, seven relief valves were subjected to 103-kPa (15-psi) target overpressure waveforms, produced using methane-air explosions within a fixed-volume enclosure. All seven relief valves survived the overpressure testing, maintained normal performance, and did not incur any critical component deformation. One instance of valve leakage was observed during the tests.

This paper presents the methodology and results of testing the ability of RA relief valves to withstand a survivable mine explosion. Information in this publication can be used for evaluating relief valve design and determining parameters critical to their ability to reliably withstand a survivable mine explosion and protect RA occupants. Research presented in this paper is applicable to testing and improving RA designs for underground coal mines, and could also be extended to similar applications and industries involving explosion testing.
Optimizing Process and Geometry Parameters in Bulging of Pipelines
Authors: Memon Shabbir , Mohammed Obaidur Rahman , Koppisetty D. V. Suresh , Lankarani Hamid M.
Published: January 2020

The objective of this work is to determine the optimum process and geometry parameters to attain maximum bulge height without necking / splitting failure. The effect of process parameters on strain path and its correlation with bulge height is also carried out., ANOVA is used to study the relative contribution of geometry properties, process parameters and tube thickness. It is found that the strain hardening exponent has the highest impact on bulging followed by plastic anisotropy and thickness of tube has a relatively lesser contribution to limit strains of tube bulging. The effects of process parameters, at a specific bulge height, are studied on effective strain distribution and thinning distribution, the homogeneity of which is expressed in the terms of real Kurtosis value. It is concluded that optimum process parameters not only gives less thinning and greater bulge height, it also gives more uniform deformation pattern (thinning and effective strain). The validation of optimum process parameters obtained through Taguchi is carried out using additive model and it is found that the observed value is well in agreement with the predicted value. It is also found that friction has a negative impact on bulge height as well as thinning. This is because higher friction resists the flow of material and causes the material to thin more rapidly at the critical area where necking is taking place. It is also found that bulge height is maximum at higher pressure and higher bulge length and thinning is minimum at lower pressure and higher bulge length.
Climbing Bloom’s Taxonomy With Jupyter Notebooks: Experiences in Mechanical Engineering
Authors: Weber Bryan W.
Published: January 2020

Active learning techniques are well known to improve student outcomes and shift their thinking higher on Bloom’s Taxonomy. In this paper, I will present experiences from my implementation of active learning in sophomore-level Mechanical Engineering thermodynamics classes using Jupyter Notebooks. Jupyter Notebooks are a web-based programming environment widely used in software and other industries that allows students to combine code with equations and explanations of their work. By using this software to solve open-ended design problems, students move from the Remember, Comprehend, and Apply steps of Bloom’s Taxonomy to the Analyze, Synthesize, and Evaluate stages. Successfully integrating Jupyter Notebooks with these classes has required a shift in the focus of contact hours, going from didactic presentation of material to active practice with problem-solving techniques; most class material has been moved online. This approach has been successfully implemented over several semesters, but there are nonetheless still improvements to be made, which are discussed at the end of the manuscript.
Application of a Hybrid RANS-LES Method to Free Shear Layers
Authors: Catalano P.
Published: January 2020

This paper presents the application of the XLES (eXtra Large Eddy Simulation) method to relevant test-cases. The mixing between two boundary layers and between a wake and a boundary layer are discussed. The first test case considers the mixing layer that forms at the end of a splitting plate. Two boundary layers with different free-stream velocities flow on the upper and lower side of a flat plate and join at the trailing edge forming a free shear layer. The second test case represents a mixing between the 2-D wake originating downstream an airfoil and the 2-D boundary layer developing over a flat plate placed beneath the airfoil. This application is representative of flows over multi-element configurations where the wake coming from the slat merges with the boundary layer of the main component. The method has shown to be effective reducing the modelled turbulence and providing resolved turbulence in the regions of the field treated in LES mode. The “grey-area” issue has been highlighted. This is likely connected to the stochastic character of the model.
Reliability-Based MDSDO for Co-Design of Stochastic Dynamic Systems
Authors: Azad Saeed , Alexander-Ramos Michael J.
Published: January 2020

Optimization of dynamic engineering systems requires an integrated approach that accounts for the coupling between embodiment design and control system design, simultaneously. Generally known as combined design and control (co-design) optimization, these methods offer superior system performance and reduced costs. Despite the widespread use of co-design approaches in the literature, not much work has been done to address the issue of uncertainty in co-design problem formulations. This is problematic as all engineering models contain some level of uncertainty that might negatively affect the systems performance, if overlooked. While in our previous study we developed a robust co-design approach, a more rigorous evaluation of probabilistic constraints is required to obtain the targeted reliability levels for probabilistic constraints. Therefore, we propose and implement a novel stochastic co-design approach based on the principles of reliability-based design optimization (RBDO). In particular, a reliability-based, multidisciplinary dynamic system design optimization (RB-MDSDO) formulation is developed using the sequential optimization and reliability assessment (SORA) algorithm, such that the dynamic equality constraints are satisfied at the mean values of random variables, as well as their most probable points (MPPs). The proposed approach is then implemented for two case studies to indicate the impact of including reliability measures in co-design formulations.
A Biomechanical Investigation of Collagen, Platelet-Rich Plasma, and Mesenchymal Stromal Cells on the Achilles Tendon in a Rat Model
Authors: Austin Brittany , Marie Hazel , Fagan Diana , Vanasdale Jared , Drew Stuart
Published: January 2020

This study aims to biomechanically compare four different treatment methods for repair enhancement in Achilles tendon rupture in rats: collagen, collagen and platelet-rich plasma (PRP), collagen and mesenchymal stromal cells (MSC), and a combination of collagen, platelet-rich plasma and mesenchymal stromal cells (CPM) at one and two week healing periods. This study included ninety Lewis rats weighing approximately 200–300 g. Ten rats were used as donors for MSC and PRP. For the remaining eighty rats, the right leg was completely transected 6 mm proximal to the calcaneus bone, suture repaired, wrapped in CollaTape (CoTa), and then closed. An injection of PRP, MSC, or PRP and MSC was given at the wound site to the applicable groups. After one or two weeks recovery time, the rats were sacrificed and both Achilles tendons were removed. The left tendons were used as virgin tissue controls. It was found that the maximum stress at failure, the total strain energy, the average modulus of elasticity, and the elastic strain energy all increase significantly from one week to two week recovery time. However, there was no statistical difference between treatment groups in any of the mechanical properties.
Interconnected Fluid-Filled Cells Design for Reduction of Linear Acceleration and Force Transfer to Prevent Concussion
Authors: Lindsay Alexandra R. , Chaudhary Usamah , Terry Taylor N. , Haghshenas-Jaryani Mahdi , Wijesundara Muthu B. J.
Published: January 2020

Regardless of efforts in improving helmet technologies, sport related concussions continue to be a problem. In an effort for advancing helmet liners, this research investigated a design comprised of interconnected fluid-filled cell structures that consist of a primary cell connecting to one or more secondary cells through a channel. When the primary cell undergoes impact, it deforms and pushes the fluid from the primary to secondary cells, which expand accordingly. This fluid motion absorbs the impact and dissipates energy, thereby reducing the force and acceleration transfer to a contacting body. Structures made with two hyper elastic polymers, silicone and polyurethane, were investigated in simulation and experimentation. For both materials, increasing the number of secondary cells in the structure will decrease the amount of force transfer and resulting acceleration. The optimized design, with one primary and two secondary cells, showed reduction of force by 25.2% and resulting acceleration of 80.7 m/s2 when using silicone, while cells made of polyurethane showed a 33.5% reduction of force and resulting acceleration of 72.5 m/s2. In comparison, a commercial liner (Vengeance DCT TPU Lateral Helmet Liner by Schutt® tested using the same test procedures, showed reduction in force by 24.3% and resulting acceleration of 87.0 m/s2.
Investigating the Purge Flow Rate in a Reactor Scale Simulation of an Atomic Layer Deposition Process
Authors: Nwanna Emeka Charles , Coetzee Rigardt Alfred Maarten , Jen Tien-Chien
Published: January 2020

This paper investigates the purge flow rate in a reactor scale simulation of an Atomic Layer Deposition (ALD) process. A three-dimensional numerical analysis approach was implemented in the ALD process to fabricate thin films of aluminium oxide (Al2O3). Despite the abundance of literature on the specific use of, and increase in deposited material through the process of ALD, limited studies exist on the physical and chemical processes that occur during the growth of ALD. Previous literature has indicated that purging has presented a major challenge in the effective deposition rate of the ALD process. The precise purge flow rate has also been greatly contended. The importance of the purge sequence within the ALD process cannot be overemphasized. The term purge sequence refers to the essential property that defines the ALD advanced nano-fabrication technique in producing ultra-thin film. Therefore, this study focused on the purge flow rate effects of the ALD process. The reactants employed in the simulation process were trimethyl-aluminium (TMA) and ozone (O3) as the metal and oxidant precursors, respectively, and inert argon as the purge gas. Numerical simulations were carried out at a stable operating pressure of 1 torr, with a substrate temperature of 200°C, and three purge flow rates of 20, 10 and 5 sccm, respectively. An extended ozone exposure is crucial to in providing an adequately oxidized substrate. It is discovered that the 5 sccm flow rate shows, superior mass fractions, unity surface coverage and a time extensive surface deposition rate. The 20 sccm, 10 sccm and 5 sccm purge flow rate growth obtained a 0.58, 0.92, and 1.6 Å/cycle, respectively. The findings revealed close similarities to experimental behaviours and recorded growth.
Structural Design and Performance Analysis of a Deployable Vehicle Shelter With Hybrid FRP Composites and Aluminum
Authors: Wang Jinxi , Sun Lingyu , Li Lijun , Duan Jianyu
Published: January 2020

As a movable workspace, a deployable vehicle shelter has the advantages of easy transportation, good environmental adaptability, convenient maneuverability and large expansion space. Therefore, it has been widely applied in engineering rescue, medical security, living reserve, building, tourism and other fields. This paper aims to design the structure of a lightweight shelter assembly whose deployable mechanism is proposed for multi-level deployable vehicle shelter and whose steel frame and outer panel are replaced by aluminum and Glass Fiber Reinforced Polymer (GFRP) composites to reduce the weight of shelter. Additionally, the structural strength and stiffness are analyzed by the finite element method (FEM) under typical operation loads, such as bending, torsion, hard brake, turn, as well as modal analysis. This study could contribute to the knowledge for the lightweight design and engineering application of deployable vehicle shelters.
Definition and Evaluation of Induced Geometry for Design
Authors: Fischer Bryan , Morse Edward
Published: January 2020

Certain classes of parts include geometry that is inadequately addressed in current product definition standards. In some cases, the form of this geometry needs to be specified independently from the surface details. Examples of this include formed screens and meshes, as well as “rigidized” sheet metal components, tubular structures, and additively manufactured lattices. In each of these cases, the important functional geometry is related to a series of contact points or mid-points that are intended to conform to the designed profile. This paper seeks to more carefully examine the challenges associated with this geometry and the specifications needed to define and control it, and it reviews existing tools and techniques that may be applicable in meeting these challenges.
The Effect of Mixing Promotors on Sweeping Gas Membrane Distillation System Performance
Authors: Alqsair Umar F. , Alwatban Anas M. , Alshwairekh Ahmed M. , Krysko Robert , Alghafis Abdullah A. , Oztekin Alparslan
Published: January 2020

Computational fluid dynamics simulations were conducted to model the effect of adding mixing promoters in sweeping gas membrane distillation modules. Net-type spacers of 45° are placed in the feed side while membrane corrugation is employed with the tips of the corrugation pointing towards the permeate side. The membrane corrugation is of chevron type. The membrane is considered as a functional surface, and the vapor flux through the membrane is modeled using the Dusty-Gas model. The vapor flux equation couples the vapor pressure variation across the membrane with the feed concentration. The flow inside the channels with mixing promoters is considered turbulent. The k–ω SST turbulent model is used to model the steady-state turbulent structures inside the channels. The flow rate in the feed side is fixed, and the flow rate in the permeate channel is varied so that Rep = 1000,1500, and 2000 are considered. The inlet feed and permeate temperatures, and the membrane properties are fixed. The results indicate that the presence of mixing promoters increases the vapor permeation through the membrane by alleviation of the concentration and temperature polarization effects. The mixing promoters are more effective at high flow rates in both channels.
Three-Dimensional Transient Heat Conduction Equation Solution for Accurate Quantification of Heat Transfer Coefficient in Transient Liquid Crystal Experiments
Authors: Ahmed Shoaib , Singh Prashant , Ekkad Srinath V.
Published: January 2020

Liquid crystal thermography and infrared thermography techniques are typically employed to measure detailed surface temperatures, where local heat transfer coefficient (HTC) values are calculated by employing suitable conduction models. One such practice, which is very popular and easy to use, is the transient liquid crystal thermography using one-dimensional semi-infinite conduction model. In these experiments, a test surface with low thermal conductivity and low thermal diffusivity (e.g. acrylic) is used where a step-change in coolant air temperature is induced and surface temperature response is recorded. An error minimization routine is then employed to guess heat transfer coefficients of each pixel, where wall temperature evolution is known through an analytical expression. The assumption that heat flow in the solid is essentially in one-dimension, often leads to errors in HTC determination and this error depends on true HTC, wall temperature evolution and HTC gradient. A representative case of array jet impingement under maximum crossflow condition has been considered here. This heat transfer enhancement concept is widely used in gas turbine leading edge and electronics cooling. Jet impingement is a popular cooling technique which results in high convective heat rates and has steep gradients in heat transfer coefficient distribution. In this paper, we have presented a procedure for solution of three-dimensional transient conduction equation using alternating direction implicit method and an error minimization routine to find accurate heat transfer coefficients at relatively lower computational cost. The HTC results obtained using 1D semi-infinite conduction model and 3D conduction model were compared and it was found that the heat transfer coefficient obtained using the 3D model was consistently higher than the conventional 1D model by 3–16%. Significant deviations, as high as 8–20% in local heat transfer at the stagnation points of the jets were observed between h1D and h3D.
Period-1 Motions in a Periodically Forced, Nonlinear, Machine-Tool System
Authors: Xing Siyuan , Luo Albert C. J.
Published: January 2020

In this paper, period-1 motions in a two-degree-of-freedom, nonlinear, machine-tool system are investigated by a semi-analytical method. The stability and bifurcations of the period-1 motions are discussed from the eigenvalue analysis. A condition is presented for the tool-and-workpiece separation in period-1 motions. Machine-tool vibrations varying with displacement disturbance from a workpiece are discussed. Numerical simulations of period-1 motions are completed from analytical predictions.
Control Simulations for a Stewart Platform Compensator Mounted on Moving Base
Authors: Ono Takeyuki , Eto Ryosuke , Yamakawa Junya , Murakami Hidenori
Published: January 2020

In this paper, utilizing the analytical equations of motion for a base-moving Stewart platform, we design an active wave compensation system for a surgery table installed on the top plate of a Stewart platform in a ship. In our medical application, the base plate of a Stewart platform moves with the motion of the ship. For a base-moving Stewart platform, we presented analytical equations of motion in matrix form in the paper: IMECE2018-87253. The objective of the platform is to compensate the pitching, rolling, and heaving motions of the ship (with respect to an inertial coordinate system).

As control methods for the nonlinear system, we employ a hybrid controller combining resolved acceleration control with H∞ control, and integral sliding mode control (ISMC). The ISMC with input time delay is also designed with a state predictor, which includes a ship motion predictor utilizing an autoregressive model.

Finally, to assess the control performance and robustness for the system with uncertainties, numerical simulations are presented. In addition, the simulation results of the predictor based ISMC for the system with input time delay are illustrated showing the effectiveness of the controller.
Design and Analysis of an Innovative Portable Water-Cooled Thermoelectric Generator Apparatus
Authors: Coday Eric , Parker Jordan , Johnson Randall , Duan Shawn
Published: January 2020

Thermoelectric generator technology can be utilized as a renewable energy source and has untapped potential. Thermoelectric generators (TEGs) have been used by industry experts to make some thermodynamic processes slightly more efficient. However, TEGs can be operated in a manner that allows for greater energy production at a higher efficiency and in a stand-alone setting. This paper presents design and analysis of an innovative portable water-cooled thermoelectric generator apparatus. The apparatus can create clean energy using optimal heat transfer through the device. To reduce the amount of power lost to internal heat resistance, the device is cooled by a large body of water. Solar irradiation is the primary heat source for the TEGs and is absorbed using copper foil and high emissive paint. The temperature differential predicted during device operation was modeled using ANSYS. The ANSYS heat transfer model revealed that heat absorption and subsequent transfer to a body of water was possible without exceeding the operating parameters of the TEGs. Experimental results revealed that a 120°C temperature difference across the TEGs produced 12.5 V of electricity. Analysis of the water-cooled TEG prototype performance revealed that power production is possible, and the design has numerous applications.