bluuebunny/crossref_metadata_2025 huggingface dataset:
Important Educational Factors for Computational Fluid Dynamics When Teaching New Users How to Apply Commonly Employed Initial Set-Up Configuration Parameters for Airfoils
Authors: Al-Qarishey Hussein , Fletcher Robert
Published: January 2020

Inflowing turbulence influences aerodynamic behaviors of the impacted geometries, and are important considerations for systems such as sailing vessels, wind turbines, ground vehicles, and aircraft. It is important to understand and evaluate the characteristic nature of this turbulence. Computational Fluid Dynamics (CFD) is now a foundational analytical instructional tool used to help educate both undergraduate and graduate engineering students on how predict and describe both boundary layer behavior and the resulting downstream turbulence. Increasing the predication accuracy of turbulence models, particularly at higher Reynolds number regimes remains a fundamental consideration in CFD analysis.

The work discussed here focuses on understanding how CFD simulations can be impacted by basic CFD approaches and configurations. Commonly use unstructured grids and incremental positive angles of attack around the well-studied NACA0012 airfoil were used to assess how these basic set-up parameters can influence CFD turbulence results. Navier-Stokes equations were solved for incompressible flow to assess downstream turbulence using the SST k-ω (two equation) turbulence model within ANSYS Fluent (SIMPLE solution method). Two airfoil configurations with respect to angle of attack (α) were of interested and studied, with one configuration defined as “fixed-position” and the second configuration defined as “changed-position”. Fixed-position refers to a single common airfoil/grid configuration and changing incoming Ux, Vy velocity vectors to yield different angle of attack (α) values. Changed-position refers to a utilizing a single Ux velocity vector and physically rotating the impacted airfoil in the computational field to yield different angles of attack.

A two-dimensional unsteady state SST k-ω turbulence model was used at a Reynolds number of 3.0 × 106. The resulting data from the system setup models studied here (fixed and changed-positions) were successfully validated by comparing the computed lift and drag coefficients at these varying α values to common values found in literature. Downstream pressure contours, along with Ux and Vy net-velocity contours at various distances from 1.5 cord lengths up to 12.0 cord lengths from the leading edge of the airfoil at incremental angles of attack were studied. The authors review how such variations in rudimentary approaches can impact the CFD downstream output results.
Integration of Vibration Absorbers in Milling Chucks
Authors: Joshi Mihir , Weigold Matthias , Schoell Michael
Published: January 2020

The use of cutting tool systems with a high slenderness ratio is encountered in the machining of deep cavities in the mechanical engineering industry, especially in the manufacturing of tools and dies. Cutting tool systems with a large slenderness ratio, owing to their dynamic compliance, are prone to vibrations during machining processes. These vibrations affect the quality of the machining process and the life of machine components. Integration of a vibration absorber in the cutting tool system helps in the reduction of machining vibrations. The reduction in vibrations is due to a shift in the resonance frequency of the modified system. This experimental study presents the identification of design possibilities of a vibration absorber for integration in the cutting tool system. The mass and geometry of the vibration absorber are varied and its integration in the milling chuck is explored. Firstly, experimental modal analysis is conducted to determine the effects of the dynamic vibration absorber on the frequency response function of the modified cutting tool system. Secondly, the effects of the dynamic vibration absorber on the machining process for a range of technology parameters are illustrated. During the machining process, the cutting forces are measured using a three-component dynamometer in time domain. Finally, the results are evaluated based on process quality, i.e. surface roughness and analysis of cutting force signal in the frequency domain. This study provides an understanding of the relationship between the mass and the geometry of the vibration absorber integrated in the cutting tool system and their influence on process stability.
Gas Turbine Combustor Liner Wall Heat Load Characterization for Different Gaseous Fuels
Authors: Ramakrishnan Kishore Ranganath , Ahmed Shoaib , Wahls Benjamin , Singh Prashant , Aleman Maria A. , Granlund Kenneth , Ekkad Srinath , Liberatore Federico , Ho Yin-Hsiang
Published: January 2020

The knowledge of detailed distribution of heat load on swirl stabilized combustor liner wall is imperative in the development of liner-specific cooling arrangements, aimed towards maintaining uniform liner wall temperatures for reduced thermal stress levels. Heat transfer and fluid flow experiments have been conducted on a swirl stabilized lean premixed combustor to understand the behavior of Methane-, Propane-, and Butane-based flames. These fuels were compared at different equivalence ratios for a matching adiabatic flame temperature of Methane at 0.65 equivalence ratio. Above experiments were carried out a fixed Reynolds number (based on the combustor diameter) of 12000, where the pre-heated air temperature was approximately 373K. Combustor liner in this setup was made from 4 mm thick quartz tube. An infrared camera was used to record the inner and outer temperatures of liner wall, and two-dimensional heat conduction model was used to find the wall heat flux at a quasi-steady state condition. Flow field in the combustor was measured through Particle Image Velocimetry. The variation of peak heat flux on the liner wall, position of peak heat flux and heat transfer, and position of impingement of flame on the liner have been presented in this study. For all three gaseous fuels studied, the major swirl stabilized flame features such as corner recirculation zone, central recirculation zone and shear layers have been observed to be similar. Liner wall and exhaust temperature for Butane was highest among the fuel tested in this study which was expected as the heat released from combustion of Butane is higher than that of Methane and Propane.
Joining of Q235 Low-Carbon Steel Plates by Friction Stir Welding With AA2A12 Strip As an Auxiliary Solder
Authors: Zhang Peng , Zhao Shengdun , Dong Peng , Wang Yongfei , Chen Chao , Meng Dean
Published: January 2020

This article proposed a novel friction stir welding process to weld high melting point alloy plates with low melting point alloy strip as auxiliary solder to reduce the wear of the friction stir welding tool and extend its service life, and feasibility of this process was evaluated. An AA2A12 strip was clamped to the gap between two Q235 low-carbon steel plates as an auxiliary solder before welding, then a joint with excellent surface quality and smooth weld edge transition was obtained by friction stir welding process in which the tool was made of low-cost material tungsten-carbide. Macrostructure, microstructure and fracture surface of the joints were investigated by optical microscope and scanning electron microscope. The tensile tests were conducted to evaluate the mechanical properties of the joint at rotational speed of 800 r/min, traverse speed of 50 mm/min, with plunge depth and probe offset of 0.1 mm. The tensile strength of the joint was 108.9 MPa at room temperature what proved the feasibility of the novel way we proposed. The micro-hardness value of the cross section of the welded joint is M-shaped from the AS to the RS, and gradually decrease from the top plane to the bottom plane. There is a certain relationship between the welding process parameters and the macroscopic morphology, micro-hardness and mechanical properties of the welded joint. Hence, the method we proposed has high innovation, and economy, high value of scientific research and industrial application, and provides a new idea about friction stir welding of high melting point alloys.
A Compared Approach on How Deep Learning May Support Reverse Engineering for Tolerance Inspection
Authors: Bici Michele , Mohammadi Saber Seyed , Campana Francesca
Published: January 2020

Reverse Engineering (RE) may help tolerance inspection during production by digitalization of analyzed components and their comparison with design requirements. RE techniques are already applied for geometrical and tolerance shape control. Plastic injection molding is one of the fields where it may be applied, in particular for die set-up of multi-cavities, since no severe accuracy is required for the acquisition system. In this field, RE techniques integrated with Computer-Aided tools for tolerancing and inspection may contribute to the so-called “Smart Manufacturing”. Their integration with PLM and suppliers’ incoming components may set the information necessary to evaluate each component and die.

Intensive application of shape digitalization has to front several issues: accuracy of data acquisition hardware and software; automation of experimental and post-processing steps; update of industrial protocol and workers knowledge among others. Concerning post-processing automation, many advantages arise from computer vision, considering that it is based on the same concepts developed in a RE post-processing (detection, segmentation and classification). Recently, deep learning has been applied to classify point clouds, considering object and/or feature recognition. This can be made in two ways: with a 3D voxel grid, increasing regularity, before feeding data to a deep net architecture; or acting directly on point cloud. Literature data demonstrate high accuracy according to net training quality.

In this paper, a preliminary study about CNN for 3D points segmentation is provided. Their characteristics have been compared to an automatic approach that has been already implemented by the authors in the past. VoxNet and PointNet architectures have been compared according to the specific task of feature recognition for tolerance inspection and some investigations on test cases are discussed to understand their performance.
Consideration and Impact Assessment of Measurement Uncertainty in the Context of Tolerance Analysis
Authors: Heling Björn , Müller Andreas Michael , Schleich Benjamin , Hausotte Tino , Wartzack Sandro
Published: January 2020

Virtual product validation ensures that products fulfil their function under different varying conditions. Within the framework of virtual product validation, variation simulation represents the specific area that deals with the consequences of geometric part variations on functional key characteristics. In addition to the nominal geometry of the parts, the permissible part deviations in the form of tolerances, the joining sequence and process variations during assembly are required to simulate the effects of geometrical part deviations on assembly or product key characteristics. If the required quality targets are not achieved, the part tolerances usually have to be tightened, which goes hand in hand with increased production costs.

The achievable part tolerances depend, among other things, on the material used, the workpiece dimensions, the manufacturing process, but also on the interaction between these factors. Therefore, the prediction of specific manufacturing process dependent deviations is hardly possible. However, if predictions should be made as exactly as possible, there is also the possibility to integrate measurement data directly or indirectly into the tolerance analysis. This has the advantage that material- and production-specific deviations can be considered in the best possible way for a certain part geometry. However, if measurement data is integrated into tolerance analysis, the problem arises that, in addition to the actual component deviation, the measurement uncertainty as part of the measurement result, must be implicitly determined in order to also be taken into account. Conversely, the tolerance analysis results are also influenced by the measurement uncertainty.

To tackle this issue a novel procedure is presented which allows the quantification of the influence of the measurement uncertainty on the result of the tolerance analysis. In addition, it is shown how the measurement uncertainty is determined, whereby in particular the single point measurement uncertainty is dealt with. Since the measurement uncertainty can be different for each measuring point, Skin Model Shapes are used for tolerance analysis in order to have the possibility for defining point specific information.

The developed procedure is then applied to a suitable case-study. CT measurements are used as the measurement method for determination of the single point measurement uncertainties. Finally, different scenarios for the tolerance analysis are compared in order to quantify the influence of the measurement uncertainty in the best possible way.
Mechanical Properties of Interlocking Cell Structure for Soft Exoskeleton Suits
Authors: Lee Dongchan , Yang Chulho
Published: January 2020

This paper presents design considerations of an adjustable flexible auxetic structure used in soft wearable suits with a Cross Chiral Honeycomb (CCH) structure. In order to design a macro-auxetic structure with elastic flexibilities in the soft wearable suit, it is important to develop an auxetic unit cell with adjustability of stiffness. Airbag inflation and deflation mechanisms on the adjustable stiffness pads with auxetic foam play key roles in either the protection of the human body or the assistance of human motion through the reversible configurations of the structure. Periodic cellular structures used in auxetic foam were first considered in the field of lightweight construction due to their high specific stiffness, damping, and energy absorbing properties. The development of new manufacturing processes, especially the development of modern 3D-printers, has allowed the creation of 3D auxetic structures. Experiments of several specimens were conducted to verify mechanical structural characteristics of a CCH structure. Through this approach, valid geometric parameters of the macro-auxetic structure used in the soft wearable suit could be designated.
Adaptive Mesh Refinement of the Solidification Front in Continuous Caster Simulations
Authors: Zhou Xiang , Moore Matthew T. , Ma Haibo , Silaen Armin K. , Zhou Chenn Q.
Published: January 2020

A better understanding of the complex phenomena that occur along the solidification front in a continuous casting process is a fundamental necessity for reliably evaluating whether specific casting conditions inherently influence defect generation rates. Due to the intrinsic nature of the casting process, engineers are restricted in their ability to obtain accurate measurements of the shell development during casting operations. Through the end of the 20th century and up to the present, significant progress has been made in overcoming these limitations through the development of numerical models capable of accurately replicating the behavior of targeted phenomena that occur during the casting process. Continual revisions to these models have produced notable results; however, these approaches have primarily implemented predefined mesh representations of a system for simulation. The mesh utilized in any numerical simulation directly influences the results the model can generate. Developing an appropriate mesh capable of replicating the complex behavior of a system can require significant consideration of various factors involved in the construction of the mesh, the physics of the process being modeled, along with the solvers utilized in evaluating the system. Inadequate mesh construction may yield insufficient refinement for capturing desired aspects of a system or generating large areas of unneeded refinement. This article discusses characteristic behaviors and limitations of a select grouping of meshing algorithms currently available, as well as potential methods for avoiding mesh-driven solutions when simulating the solidification process in a continuous caster. Particular emphasis is placed on incorporating adaptive mesh refinement to lessen the potential for mesh-driven solutions and to reduce unnecessarily high cell-counts of the mesh through the restructuring of the mesh in accordance with the active simulation results. A numerical model was developed using the Simcenter™ STAR-CCM+™ software, and using Eulerian multiphase VOF melting and solidification models for steady-state simulations. Casting conditions and measurement data (provided by an industrial collaborator) were employed in defining boundary conditions, as well as for the model validation. The predicted shell profiles demonstrated good agreement with shell-thickness measurements obtained from the quarter-mold location of a recovered break-out shell segment.
Influence of the Applied Load on the Creep Behaviour of Tin-Silver-Copper Solder
Authors: Soares Delfim F. , Ribeiro Pedro E. , Capela Pauline , Barros Daniel A. , Cerqueira Maria F. , Teixeira Senhorinha , Macedo Francisco , Teixeira José C.
Published: January 2020

During the life cycle of an electronic printed circuit boards (PCBs), the cold solder joints formation between the component and PCB are a failure mode that happen commonly. This phenomenon is related to solder joint fatigue and is attributed mainly to the mismatch of the coefficients of thermal expansion (CTE) of component-solder-PCB assembly. With today’s solder joint thickness decreasing and increasing working temperatures, among others, the stresses and strains due to temperature changes are growing, leading to limited fatigue life of the products. In this way, once as fatigue life decreases with increasing plastic strain, it is important to study creep occurrence, especially during thermal cycles.

In this work, a dynamic mechanical analyser (DMA) was used to study the influence of different applied load and temperature on the creep behaviour of the solder during a sequence of cycles. For these tests, different SAC405 alloy samples were produced, all in the same processing conditions. Creep tests were made on three-point-bending clamp configuration, isothermally at 303, 323 and 348 K, under three separate applied load of 3, 5 and 9 MPa.

The results show that creep rate has an important decrease from the 1st to the following applied creep cycles. This behaviour occurs for all the tested loads and temperatures. Results, also, show that the main creep mechanisms changes, from a diffusion base type, for low load and different temperatures, to a dislocation glide-climb type for an applied load of 9 MPa and temperatures from 303 to 348 K. Experimental determined n exponent for the tested conditions allows the correlation between creep mechanisms and experimental parameters (applied load and temperature).
Improving Temperature Probe Calibration Accuracy in Constant Temperature Baths With a Novel Data Processing Method
Authors: Koz Mustafa , Visalli Thomas
Published: January 2020

The accuracy of temperature probe calibration in a constant temperature bath is governed by the stability and uniformity of the bath. In the available literature, there have been efforts in designing baths with better stability and uniformity. This work is distinguished from the previous efforts by presenting a novel data processing method that improves the calibration performance without the need to improve the inherent qualities of the bath. The stability limitation is addressed by filtering out the time dependent components of temperature readings, and then the resulting calibration performance becomes limited only by the uniformity. This work provides the theory and guidelines for filtering the time dependent signal components such as sampling rate and duration based on the stability of the bath. The method is experimentally validated by applying it to a baseline bath and the results are compared to those from a high-end bath. As a figure of merit, the probability of obtaining a calibration value within ±0.75 mK of the high-end bath is reported. In a calibration scenario in which the uncertainty is predominantly governed by the stability, only 10% of the calibration values are within the aforementioned limits with the conventional method. With the application of the novel method, all of the calibration data meets the criterion.
Simulation and Experimental Investigation of Scallop Removal Using Friction Stir Processing and Complex Toolpath
Authors: Grimm Tyler J. , Mears Laine
Published: January 2020

Machining of complex geometries is conventionally accomplished through the use of a ball-end mill and a helical toolpath which follows along the contours of the geometry at incremental depths. While effective for the majority of geometries, this method produces scallops which result from the ball-end mill radius and the step size of the toolpath. The size of these scallops, which degrades the surface finish, can be minimized by utilizing a relatively small step size. However, this results in increased machining time.

A novel method of scallop removal is simulated and experimentally tested herein on 6061-T6511 aluminum. This method applies a friction stir processing effect to the workpiece by rotating a ball-end mill tool in reverse over the surface of the material subsequent to ball-end mill cutting passes. Additionally, the path constructed for scallop removal was a self-intersecting epicycloid which plastically deforms the scallops in order to reduce the surface roughness and impart favorable compressive surface stress. In this study, the surface variability produced from this process is reported for several different tool paths, determined experimentally and through simulation. Future studies will investigate the microstructural effects of this process, as well as the resulting microhardness and residual stress profile.
Stirling Engine Robust Foil Regenerator Efficiency
Authors: Yanaga Koji , Gao Yuan , Li Ruijie , Qiu Songgang
Published: January 2020

Combined Heat and Power (CHP) systems are one of the solutions to save energy by utilizing waste heat for addressing global warming and the global energy crisis. In many CHP technologies, the Stirling engine is outstanding since it has the advantage of various energy sources such as solar, geothermal, and industrial heat waste. The regenerator plays a key role in building a high efficiency Stirling Engine. Since it works as an energy storage component in the Stirling engine, its performance directly affects the Stirling engine efficiency. In the previous research, a new regenerator called the robust foil regenerator was designed to improve the performance of the regenerator. The regenerator was manufactured through the method of additive manufacturing techniques since the thickness of each flow channel is 0.3mm. In this research, a test bench was designed and manufactured to reveal the characteristics of the regenerator experimentally. By measuring the pressure drop and the temperature difference through the regenerator, the friction coefficient and the Nusselt number correlations were derived respectively. These correlations were compared to the published friction factor and Nusselt number correlations. In addition, to evaluate the geometrical configuration of the regenerator, the NPH/NTU ratio was calculated using the derived friction coefficient and Nusselt number.
A Simple Control Strategy for Increasing the Soft Bending Actuator Performance by Using a Pressure Boost
Authors: Pinto Brian Alphonse , Schiller Lars , Seibel Arthur
Published: January 2020

High-speed actuation of soft actuators requires high source pressure to transfer air as quickly as possible into the actuator. Allowing high source pressure and having the deformation angle as the only control input may allow faster actuation, but there is a risk of bursting when the actuator is prevented from reaching the desired angle, for example, due to an obstacle. The other option to control the actuator’s deformation is based on controlling the pressure. In this paper, we present a simple control strategy that uses an initial pressure boost in a pressure-based PID controller showing the same performance as in angle-based PID control. The performance improvement is demonstrated experimentally on a standard soft bending actuator and a gecko-inspired, climbing soft robot.
Three-Dimensional Printing of Carbon Nanostructures
Authors: Resnick Alex , Park Jungkyu , Haile Biya , Farfán Eduardo B.
Published: January 2020

Multi-layered carbon nanostructures are the next leap for many advanced consumer and industrial applications that require both high strength and uniquely high electrical and thermal properties. Applications of three-dimensional (3D) carbon nanostructures have already been theorized to include wearable technology, processor chip heat transfer material, and flexible electronics. 3D carbon nanostructures appear in the form of carbon nanotubes (CNTs) and layered graphene tiers, however, many structures previously examined have been limited to one or two graphene layers or non-repeatable structured patterns. Many of the electrical and thermal properties of CNTs are still being investigated, but the initial studies demonstrate promising results such as the thermal conductivity ranging in the thousands W/m-K. Developing new ways to fabricate these structures at a reasonable cost has become a primary focus for graphene-based research. In this study, 3D carbon nanostructure samples are 3D printed using laser lithography, then a series of high temperature furnace burns and Nickel Chemical Vapor Deposition (CVD) is utilized to leave a previously multi-species structure as a solely carbon-species structure with mostly carbon sp-2 bonds. CVD has proven to be a leading method for forming graphene due to the ability to control graphene nucleation across larger surfaces and structures. Nanoscale 3D printing of carbon structures also allows for a great degree of freedom towards the creation of repeatable patterns or structures that are currently trying to be achieved in other studies. This study employs the use of controlled cleanroom environments with cutting edge technology and machines to fabricate the 3D carbon nanostructures.
Evaluating the Effect of Number of Spans on Heat Transfer in Greenhouses
Authors: Kruger S. , Pretorius L.
Published: January 2020

The present study concerns convective flows in the empty volume above the plant canopy in a confined greenhouse. The purpose of this paper is to numerically investigate the effect of the number of spans on the convective heat transfer in closed greenhouses. The initial greenhouse CFD model cavity is validated against experimental results found in the literature. Thermal convection is induced by heating the bottom of the cavity. The numerical model is then modified to represent two-l greenhouse cavities with different numbers of spans. The computational fluid dynamic (CFD) software is then used to analyze mainly the natural convective heat transfer, velocity and temperature distributions for the single span greenhouse, as well as multi-span greenhouses (containing two and three spans). The greenhouse CFD model floor is heated, and the walls are adiabatic, corresponding to Rayleigh-Bénard convection. A mesh sensitivity analysis was conducted to determine a suitable size for the mesh. Results show that adding additional spans to the initial single-span cavity has a pronounced effect on the Nusselt-number distribution on the floor of the cavity. The temperature and velocity distributions were also significantly influenced. The four-span cavity showed three convective cells instead of four as for the lowest Rayleigh number.
On Increasing Productivity of Micro-Friction Stir Welding With Aid of Tool Shoulder Micro-Features
Authors: Ahmed Shuja , Mukhopadhyay Akash , Saha Probir
Published: January 2020

Prior investigations on micro-friction stir welding (micro-FSW) of 0.5 mm thick aluminium alloy 6061-T6 sheets have shown that increasing the tool travel speed above 200 mm/min, at a fixed tool rotational speed (1900 rpm) and shoulder penetration (0.10 mm), results in lack of penetration defect in the welds. This limits the production rate and may distract the interest of industries which aim at utilizing micro-FSW for joining of micro-mechanical components. The present work investigates the utilization of micro-features on tool shoulder face to solve this issue. A spiral shape of micro-feature having a unique cross-section was employed on the tool shoulder and welding was performed at a tool travel speed of 1000 mm/min at two plunge depths (0.10 and 0.14 mm). The forces, temperature and material distribution ‘during welding’ and the surface finish, microstructure, microhardness and tensile property of the weld obtained ‘post welding’ were analyzed and compared with that of the welds obtained with featureless tool shoulder. It was found that low temperature welding with better surface finish and tensile property could be achieved with micro-featured tool shoulder at 0.14 mm plunge depth even at high tool travel speed of 1000 mm/min.
CFD Modeling of the Hydrogen Fast Filling Process for Type 3 Cylinders and Cylinders Lined With Phase Change Material
Authors: Liszka Miroslaw , Fridlyand Aleksandr , Jayaraman Ambalavanan , Bonnema Michael , Sishtla Chakravarthy
Published: January 2020

A simulation of the fast filling of a 195-liter type 3 tank with hydrogen was completed with ANSYS Fluent as a baseline case for developing a CFD model capable of accurately modeling the hydrogen cylinder filling process. 141-second profiles of mass flow and temperature of the incoming hydrogen flow into the cylinder were prescribed from experimental data previously collected at the Gas Technology Institute (GTI) in Des Plaines, IL. All the simulations were completed with the coupled pressure based algorithm with the K-Omega SST turbulence model and real gas NIST properties (REFPROP) to capture the effects of compressibility of hydrogen during the filling process. Gravity was enabled in the axial direction of the cylinder. The initial pressure and temperature in the cylinder were 124 bar and 292.3 K, respectively, with a target, experimental pressure of 383 bar at the end of the filling.

For the initial case, the walls of the cylinder were modelled as adiabatic to reduce the computational effort. The final pressure and temperature of the adiabatic wall case matched the experimental pressure and temperature within approximately 30 bar and 6 degrees, respectively. The overall pressure and temperature profiles over the course of the filling process also provided a good match between the simulation results and experimental data. A conjugate heat transfer case with the aluminum liner as part of the domain and an adiabatic outer wall was attempted in order to capture the heat transfer to the liner. The conjugate heat transfer case provided promising results but was taxing in the computational time needed to simulate the entire filling process.

A User Defined Function (UDF) for a simple lumped heat capacitance model was applied at the wall to model the wall temperature and capture the heat transfer occurring to the wall while reducing the time needed to complete the simulation. The final pressure prediction for this case was excellent, within 3 bar of the experimental value, and matched it accurately for the duration of the fill process. The final temperature prediction worsened and exceeded the experimental value by 16 degrees Celsius. The UDF model also allowed the ability to easily explore more exotic liners such as Phase Change Materials (PCM) which were also simulated in this work.
Development of the Control and Acquisition System for a Natural-Gas Spark-Ignition Engine Test Bench
Authors: Gasbarro Lorenzo , Liu Jinlong , Ulishney Christopher , Dumitrescu Cosmin E. , Ambrogi Luca , Battistoni Michele
Published: January 2020

Investigations using laboratory test benches are the most common way to find the technological solutions that will increase the efficiency of internal combustion engines and curtail their emissions. In addition, the collected experimental data are used by the CFD community to develop engine models that reduce the time-to-market. This paper describes the steps made to increase the reliability of engine experiments performed in a heavy-duty natural-gas spark-ignition engine test-cell such as the design of the control and data acquisition system based on Modbus TCP communication protocol. Specifically, new sensors and a new dynamometer controller were installed. The operation of the improved test bench was investigated at several operating conditions, with data obtained at both high- and low-sampling rates. The results indicated a stable test bench operation.
Optimization of a Manifold Microchannel Heat Sink Using an Improved Version of the Augmented Epsilon Constraint Method
Authors: Tartibu L. K. , Okwu M. O.
Published: January 2020

The increase of heat generated in integrated circuit because of the miniaturization of electronic components requires more aggressive cooling solutions in order to minimize this high heat flux and address the temperature non-uniformity. In this paper, a manifold microchannel heat sinks has been investigated. In order to enhance the heat transfer performance of the microchannel, an improved version of the augmented epsilon constraint method is adopted for the optimization of the device. Four non-dimensional design variables have been used to describe the geometry of the manifold microchannel heat sinks. The thermal performance and the pumping power have been incorporated in the mathematical programming formulation as indicators of the thermal performance. A surrogate-based approximation based on the Response Surface Approximation has been utilized to evaluate these two objectives. This new mathematical approach has been implemented in the General Algebraic Modelling Systems (GAMS). Details about single and multi-objective optimization formulation of the problem will be disclosed. Optimal solutions describing the best geometrical configuration of the device will be computed. The implications of the geometrical configuration on the performance the manifold microchannel heat sinks will form part of the main contribution of this study.
A Study on the Fluid Flow and Heat Transfer for a Porous Architected Heat Sink Using the Idea of CFD Modelling
Authors: Hassan Ali Mohamed I. , Al-Ketan Oraib , Baobaid Nada , Khan Kamran , Abu Al-Rub Rashid K.
Published: January 2020

The drive for small and compact electronic components with higher processing capabilities is limited by their ability to dissipate the associated heat generated during operations. Therefore, these components are equipped with heat sinks to facilitate the dissipation of thermal energy. The emergence of additive manufacturing (AM) allowed for new degrees of freedom in terms of design and eliminated the need for excessive tooling that is associated with the conventional manufacturing processes. As such, AM facilitated the development of geometrically complex heat sinks that are capable of capitalizing on topological aspects to enhance their performance. The main objective of this study is to propose and develop architected heat sinks. We propose the use of heat sinks with topologies based on triply periodic minimal surfaces (TPMS). 3D CFD models are developed using Starccm+ platform for three architected heat sinks to study the heat transfer coefficient and surface temperature in free convection heat transfer domains. The heat dissipation versus the input heat sources as well as the heat transfer coefficient will be used for measuring the heat sink performance. The required fluid flow rate and pressure drop will be used to measure the required cooling power for the proposed heat sinks.
Modelling, System Identification and Position Control Based on LQR Formulation for an Electro-Hydraulic Servo System
Authors: Borrás Pinilla Carlos , Sarmiento José Luis , Guiza Rubén Darío
Published: January 2020

This study presents the mathematical modelling, system identification using grey-box model estimation and position-tracking control for an electro-hydraulic servo system (EHSS) using four control strategies based on LQR formulation: Linear quadratic regulator (LQR) approach for servo systems, linear quadratic integral (LQI), linear quadratic tracking (LQT) and a variation of LQT named here LQTβ. First, the nonlinear model of the electro-hydraulic servo system was obtained using differential equations based on hydraulic theory and physical laws.

The model was then linearized and its parameters were estimated using grey-box method when the open-loop system was excited with a chirp signal from 0 to 30 [Hz]. The estimated model was verified with experimental data of the open-loop system response for square wave and continuous step inputs of different amplitudes and frequencies. For the position-tracking four control strategies based on LQR formulation were proposed. The main difference among them is the conception of the cost function that is minimized: the LQR includes all the system’s states and the control signal, the LQI includes all system’s states, the tracking error and the control signal, the LQT includes only the tracking error and the LQTβ the tracking error and its derivative. The four control strategies were simulated in MATLAB Simulink and initially tuned using Bryson’s rule, then were implemented in the real system and finely tuned by trial and error until the best performance is achieved.

They all were tested using step, square wave and sine wave inputs, and were analyzed in terms of settling time, rising time, peak time, overshoot margin, steady-state error, energy consumption and repeatability against a conventional PID controller. The experimental results showed better tracking, better repeatability and less energy consumption using the LQR based techniques than using the PID control, specifically the LQR and the LQTβ showed the fastest response and smallest steady-state error among the LQR based strategies. This study was carried out with the electro-hydraulic servo system (EHSS) of the seismic shaker table of the Dynamics and Structural Control Lab at Universidad Industrial de Santander.

The seismic shaker table is composed of a Parker double rod dynamic hydraulic cylinder commanded by an MTS 252.24G-04 servo valve and powered by an MTS 505.11 hydraulic power unit. Cylinder’s position was measured using an integrated Trans-Teck LVDT. The control system was build and implemented in MATLAB Simulink using Quanser Q8-USB card.
Plasma Actuators Optimization Using Stair Shaped Dielectric Layers
Authors: Rodrigues F. F. , Pascoa Marques J. , Trancossi M.
Published: January 2020

Plasma actuators are very simple devices which have been shown to be effective in a wide variety of applications, such as separation control, wake control, aircraft noise reduction, modification of velocity fluctuations and boundary layer control. More recently, it has been also proved their ability for applications within the heat transfer field, such as film cooling of turbine blades or ice accumulation prevention. These simple devices are inexpensive, present robustness, low weight and are fully electronic. Considering the importance of these devices, the improvement of their efficiency is a subject of great interest for worldwide scientific community. It is known that, by reducing the plasma actuator dielectric thickness, the induced flow velocity increases. However, it is also known that, thin plasma actuators present short lifetime and quick dielectric layer degradation. Till now, only actuators with constant dielectric thickness have been studied. In the present work, a new concept of plasma actuator is studied: The stair shaped dielectric barrier discharge plasma actuator. This new device present a dielectric layer which provides a decrease of the dielectric thickness along the covered electrode width. This lead to an extended plasma discharge and an increase of the induced flow velocity and efficiency. In addition, the plasma discharge is weakened on the onset of plasma formation which prevents the quick degradation of the dielectric layer and leads to an increased actuator lifetime.
Design for Additive Manufacturing: Effectiveness of Unit Cell Design Guidelines As Ideation Tools
Authors: Boyd I’Shea , Fazelpour Mohammad
Published: January 2020

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

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

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

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

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.