bluuebunny/crossref_metadata_2025_split huggingface dataset:
Wear Behavior of In-Situ Mg2Si/Al-Si Composite
Authors: Shanmugavel Balasivanandha Prabu , Mohan Vijayakumar 
Published: January 2020

Abstract
An in-situ Mg2Si/Al-Si composite was produced by the in-situ reaction approach. The in-situ Mg2Si particles were produced in an aluminum alloy (LM-6) melt due to the reaction between Potassium hexafluorotitanate (K2TiF6) and magnesium in the aluminium melt. The melt was maintained at 750°C for 30 minutes’ duration to complete the in-situ reaction. The microstructure examination revealed the homogeneous distribution of Mg2Si particles in the Al-Si matrix. The formation of the Mg2Si phase was confirmed by the X-Ray Diffraction technique. The Hardness measured on the composite is higher than that of the Aluminium alloy (LM-6). The wear behavior of both the materials was investigated using Pin-on-disk wear testing by considering parameters, such as loads (20N, 40N), sliding distance (1000m,1800m) and velocity (1.5m/s, 2m/s). The Signal to Noise (S/N) ratio was calculated to identify the parameters at which higher wear resistance was offered by both the materials. The experimental results show that the sliding distance and velocity are the major parameters influencing the wear rate in both the Al alloy and its composites. The presence of Mg2Si particles in the Al-Si matrix improved the wear resistance of the composites.
Numerical Verification of the Thermodynamic Determination of the Hydraulic Efficiency of Radial Fans
Authors: Epple Philipp , Fritsche Manuel , Reinker Felix , aus der Wiesche Stefan 
Published: January 2020

Abstract
For fans without cooling it is possible to determine the hydraulic efficiency measuring the pressure and the temperature rise through the fan. The shaft work can be determined according applying the first law of thermodynamics for an open system. Without any losses the change of state would be isotropic and the work done equal to the specific heat at constant pressure of the fluid times the isentropic temperature rise in the impeller. Due to the losses, however, the real temperature at the exit of the impeller will be higher than the isentropic temperature since the real process is polytropic. The isentropic temperature at the exit of the impeller can be computed by the isentropic relations with the inlet temperature and the pressure rise. The hydraulic efficiency can be computed as the ratio of the isentropic temperature rise divided by the real temperature rise.
In order to verify this thermodynamic approach for the determination of the hydraulic efficiency CFD simulations of a radial fan were performed. In the CFD simulation the hydraulic power, the shaft power, the pressure rise and the temperature rise can be read out and computed directly. In such a way the hydraulic efficiency computed by the ratio of the hydraulic power by the shaft power can be compared by the thermodynamically computed efficiency. In this work this comparison has been performed and the results and the precision of the thermodynamically predicted efficiency are presented and discussed in detail.
Modeling and Simulation of the Cooling and Heating Processes of Onions
Authors: T. G. Giorges Aklilu , Britton Doug 
Published: January 2020

Abstract
The shelf life of onions, or for that matter any food item, is defined as the time period where the produce has an acceptable quality and is safe to consume. For onion farmers and packers, the mode of determining the shelf life depends on the harvesting, drying, grading, packing, cooling, storing, and shipping processes and time. Quality loss can lead to economic loss as well as a decline in consumer confidence. Quality expectation should be maintained at an acceptable level for consumer purchase and consumption. In addition to post-harvest handling, the thermal history of the produce during storage and transportation plays a major part of shelf life and quality management. Due to the differences among onion varieties, some are more susceptible than others to damage resulting from temperature, high humidity, and other factors during processing. In general, the recommended storage temperatures range from 0 to 5 °C during cold storage and 20 to 30 °C during non-refrigerated storage. Both storage methods should have adequate air circulation of about 0.5 to 1.0 m3 of air per minute per 1.0 cubic meter of onions to maintain the temperature and prevent CO2 accumulation. In this study, the cooling and heating processes of different sizes of onions were conducted experimentally and numerically, and temperature readings were recorded. The cooling process was designed to simulate actual industry practice where cooling starts after the onions are placed in a cold storage room where the temperature is not constant. For the heating process, the experiment simulated industry practice where cold onions are transferred into a warm storage room where the temperature is uniform. These thermal environments are a common encounter during the storage and shipping of produce. Initially, the cooling and heating data were experimentally examined and used to estimate the cooling time as well as the cooling rate to gain an understanding of the heat transfer process. Furthermore, the data were used in evaluating the numerical simulation. In the case of small onions, the temperature changed from 21.1 to 4.4 °C after three and a half hours. However, in the case of large onions, a similar temperature change took nearly eight hours. The numerical simulation was conducted using 3D models and the thermal properties of the onions. This paper will discuss the experimental data and the CFD modeling and simulation. Based on this study, the thermal environment and critical time period that could cause changes in produce core temperature can be outlined and used to qualify thermal mishandling.
A Study of the Aerodynamics of a Helicopter Rotor Blade
Authors: Pulok Mohammad Khairul Habib , Chakravarty Uttam K. 
Published: January 2020

Abstract
In any congested area, where a fixed-wing aircraft cannot perform, rotary-wing counterparts are the best-suited option for its vertical take-off and landing capacity. The vibration induced by the rotor blade is a significant problem in helicopter performances. Rotor aerodynamic loading, rotor dynamics, and fuselage dynamics are the elements that contribute to the vibration of a helicopter. Among these elements, the key reason for the helicopter vibration is the aerodynamic loading. Determining aerodynamic loading is one of the most important criteria to design a rotor blade and to minimize vibration. Rotor harmonic airloads are generated from the rapid variation of flow around the rotor blade due to the vortex wake. A rapid drop in the circulation near the blade tip causes tip vortices which are the reason for the maximum lift at the tip of the blade. Consequently, tip vortices become the primary source of harmonic airloads. In this study, a specimen of Bo 105 helicopter rotor blade is considered to observe the aerodynamic characteristics under the external flow of air. The coefficients of lift and drag of the specimen for different angles of attack and azimuth angles are estimated. The resonance frequencies and the mode shapes are obtained. Computational results are validated by the experimental analyses of a small-scaled model of the rotor blade. From the study, the coefficient of lift is found to increase with the angle of attack up to a critical value. Similarly, the coefficient of drag increases with the angle of attack. The resonance frequencies significantly change with scaling the rotor blade.
Aeroelastic Modeling and Analysis of High Aspect Ratio Wings With Different Fidelity Structural Models
Authors: Çiçek Gökçen , Kayran Altan 
Published: January 2020

Abstract
This paper is concerned with the aeroelastic modeling and analysis of high aspect ratio wings with large torsional deflections with different fidelity structural models.
The approach for structural modeling presented here is based on linear and nonlinear theories. The linear theories are based on the slender-straight wing and bending-torsion beam finite element formulations. The nonlinear theory is based on the nonlinear finite element model with only a torsional rotation degree of freedom to study the static aeroelastic behavior. The aerodynamic theory used for aeroelastic coupling is ESDU 95010 [1], which uses steady lifting-surface theory based on Multhopp-Richardson’s solution to provide the spanwise loading of lifting surfaces with camber and twist.
Analyses are performed with three different structural models coupled with ESDU for simple plate-like wing models.
The results of linear structural models are verified with MSC NASTRAN® and the nonlinear structural model results are verified with the work of Trahair [2]. Linear aeroelastic models are compared with the MSC NASTRAN® solution performed by SOL144. Significant differences in torsional deflection of tip location are observed between the linear and the nonlinear solution methodologies. The linear theory is found to be conservative for the aeroelastic analysis of high aspect ratio wings.
Heat Transfer Characterization of 3D Printable Architected Heat Sinks
Authors: Hassan Ali Mohamed I. , Al-Ketan Oraib , Alhammadi Alya , Khalil Mohamad , Khan Kamran , Abu Al-Rub Rashid K. 
Published: January 2020

Abstract
The current developments in additive manufacturing (3D printing) overcome the limitations of traditional fabrication techniques such as milling, drilling and casting and allow to fabricate geometrically-complex heat sinks for which the topological features are capitalized upon to enhance the thermal performance. In this work, we propose new and novel 3D printable architected heat sinks with geometrically complex structures based on triply periodic minimal surfaces (TPMS). Their printability with laser-based metal additive manufacturing is assessed using electron microscopy techniques. Moreover, Computational fluid dynamics (CFD) modeling is used to assess the effect of geometry on the performance of the proposed TPMS-based heat sinks in active cooling using forced convection heat transfer environment. The convection heat transfer coefficient, surface temperature, pressure drop are predicted using CFD method. The results showed that the heat transfer performance does not depend on the architects porosity alone, but also depends on the heat sink solid-networks structure.
A Parallelized Generalized Method of Cells Framework for Multiscale Studies of Composite Materials
Authors: Rai Ashwin , Skinner Travis , Chattopadhyay Aditi 
Published: January 2020

Abstract
This paper presents a parallelized framework for a multi-scale material analysis method called the generalized method of cells (GMC) model which can be used to effectively homogenize or localize material properties over two different length scales. Parallelization is utlized at two instances: (a) for the solution of the governing linear equations, and (b) for the local analysis of each subcell. The governing linear equation is solved parallely using a parallel form of the Gaussian substitution method, and the subsequent local subcell analysis is performed parallely using a domain decomposition method wherein the lower length scale subcells are equally divided over available processors. The parellization algorithm takes advantage of a single program multiple data (SPMD) distributed memory architecture using the Message Passing Interface (MPI) standard, which permits scaling up of the analysis algorithm to any number of processors on a computing cluster. Results show significant decrease in solution time for the parallelized algorithm compared to serial algorithms, especially for denser microscale meshes. The consequent speed-up in processing time permits the analysis of complex length scale dependent phenomenon, nonlinear analysis, and uncertainty studies with multiscale effects which would otherwise be prohibitively expensive.
Fabrication, Modeling, and Testing of a Miniaturized Fast Neutron Detector
Authors: Oxandale Samuel W. , Stegeman Luke A. , Hieber Tyler J. , Sarkar Dipta , Bellinger Steven L. , Bahadori Amir A. , Leseman Zayd C. 
Published: January 2020

Abstract
This work outlines the positive-intrinsic-negative diode fabrication process for a Miniaturized Fast Neutron Detector and documents alpha source testing of a single positive-intrinsic-negative diode. The Miniaturized Fast Neutron Detector provides information about the kinetic energy distribution of neutrons with resolution up to 20 MeV and has 1–2% of the volume of comparable current state-of-the-art neutron spectrometers, namely Bonner Ball Neutron Detector sets and Capture-Gated Neutron Scintillator Detectors. The Miniaturized Fast Neutron Detector can be used to estimate neutron doses for heavy charged particle therapy patients improving the understanding of secondary cancer risks, monitor secondary neutron radiation more efficiently in therapy treatment facilities, and perform an important role in protecting astronauts from radiation.
Effects of Plate Curvature on Thermo-Mechanical Performance of U-10Mo Monolithic Fuel Plates
Authors: Ozaltun Hakan , Roh Hee Seok , Mohamed Walid 
Published: January 2020

Abstract
Monolithic fuel is a candidate fuel form being considered for the conversion of high-performance research reactors. This plate-type fuel consists of a high-density, U-Mo fuel in a monolithic form that is sandwiched between zirconium diffusion barriers, and encapsulated in an aluminum cladding. To date, large number of plates have been irradiated with satisfactory performance. The program is now moving into the qualification phase, a predecessor to the timely conversion of the target reactors. Since each reactor employs distinct fuel plate geometries for various consideration, resulting nearly 50 distinct plate geometries with unique plate design features, a single “generic” plate geometry capturing all of the extremities is not achievable. This limitation consequently requires much more cautious performance evaluations, as thermal and mechanical response of a plate with certain geometry may not be representative for a plate with a different geometry. To evaluate the performance of the plates for various geometric parameters, parametric sensitives studies have been employed. One of the important geometric parameters may have potential effects on the performance is the plate curvature. In this study, curved-plates were parametrically simulated to investigate if this geometric parameter has any effects on overall performance, In particular, radius of curvatures of the plates were varied between the bounding values, and the plates were simulated for comparable irradiation histories. The resulted temperature, deformation, stress-strain results were comparatively evaluated. The results have indicated that preferential deformations occur. This consequently caused shifting of plate centerline on curved plates. The magnitude of centerline shifts increased with increasing plate curvatures.
An Experimental Investigation of the Contribution of Different Carbonaceous Nanomaterials to Thermal Conductance of Thermal Interface Materials
Authors: Singh Prashant , Lee Seul-Yi , Mahajan Roop L. 
Published: January 2020

Abstract
With the increasing demand for higher performance and progressive miniaturization of electronic packages, power densities and the attendant thermal dissipation requirements are expected to escalate. One of the important strategies to ensure reliable operation at the device and die (chip) levels is the use of Thermal Interface Materials (TIMs) to reduce the thermal resistance between the chip and the heat sink. In this study, we have carried out an experimental investigation to characterize thermal conductance of TIMs composed of commercially available graphene (c-rGO), graphene nanoplatlets (GNPs) of different lateral sizes (5, 15 and 25 μm), and our in-house produced thermally reduced graphene oxide at 600°C (T-rGO-600). These additives were loaded in a silicone rubber matrix where their loading fraction was fixed at 2% by weight. Thermal conductance of the resulting TIMs was determined by measuring heat flow, in steady state, through a TIM sandwiched between two metal blocks. The thermal conductance values representing the combined resistance of the composite material and the contact resistances between the TIM and the metal blocks were measured at different heat flux levels across the TIM. The results show that the thermal conductance values were independent of the heat load across the TIM as well as the TIM temperature. Further, a detailed investigation of the surface functionality and structural properties has revealed that the in-house produced T-rGO-600 has superior thermal conductance when compared to the above-mentioned carbonaceous nanomaterials, which are considered as potential candidates for enhancing thermal performance of TIMs. The data demonstrates that this result is attributable to the formation of the surface functional groups and the associated morphological changes during the reduction of graphene oxide to the T-rGO-600. Among the different GNPs tested, the GNP-15 exhibited superior thermal performance compared to the GNP-5 and GNP-25 samples.
FDM 3D-Printed Thermoplastic Elastomers: Experiments, Modeling, and Influence of Process Parameters on Properties
Authors: Hripko Brad , Hoover Luke , Damodara Priyadarsini , Reissman Timothy , Lowe Robert 
Published: January 2020

Abstract
Soft, ultra-stretchable thermoplastic elastomers have recently became available for use with desktop, fused deposition modeling printers. However, the effects of additive manufacturing process parameters on final mechanical properties are presently not well-known for this class of materials, making predictive modeling and product design difficult. Here we perform a design of experiments investigation of an elastomeric material that the manufacturer claims to have up to 580% strain at fracture. Within the investigation, two factors, extrusion temperature and layer height, are selected as independent variables and mechanical properties are extracted as dependent variables based on quasi-static tension tests following ASTM D412. Primary statistical results, based on an Analysis of Variance, indicate that hotter extrusion temperatures exhibit higher Young’s moduli (at small strain), lower ultimate tensile strength, and higher fracture strain. Further, the layer thickness is not a factor unless evaluating performance at small strain, in which case it is significant and thicker layers will yield higher Young’s moduli. Several popular hyperelastic constitutive models are calibrated to our tensile data, and a preliminary finite-element simulation of a soft prosthetic finger is performed to demonstrate the potential role of predictive simulations in 3D-printed product design.
Experimental Study of Forced Convection Heat Transfer and Flow Friction of a Water-Cooled Inter-Connected Mini-Channel Heat Sink
Authors: Tikadar Amitav , K. Oudah Saad , Abdulrazzaq Nabeel M. , Paul Titan C. , Khan Jamil A. 
Published: January 2020

Abstract
Experimental investigations were performed to quantify the thermal and hydraulic performances of an inter-connected counter flow mini-channel heat sink under laminar flow regime. The aspect ratio (height/width) and the hydraulic diameter of the mini-channel were 0.33 and 750 μm respectively. Water was used as the working fluid, and a constant heat flux of 120000 W/m2 was applied on the bottom surface of the heat sink. To enable transverse flow between two counter flow streams by utilizing pressure difference, two inter-connectors were made on the middle wall. The height and width of both inter-connectors were the same as the mini-channel. Bottom surface temperature, Nusselt number (Nu), thermal resistance, and friction factor were calculated to address the effect of the inter-connectors on the overall thermal-hydraulic performance of the heat sink. The results showed that at low Reynolds number (Re), inter-connectors affect the heat transfer performance adversely while substantial heat transfer augmentation was achieved at high Re. Additionally, for all of the test range, a significant reduction of friction factor was achieved by employing transverse flow.
Miniature Hemispherical Bowl-Shaped Forming Using SLA Punch and Die: Modeling and Experimental Analysis
Authors: Mondal Debabrata , Morris Jeffrey David , Zhang Bin , Meng Wen , Chakravarty Uttam , Herrington Paul , Schilling Paul 
Published: January 2020

Abstract
Forming processes are a convenient means for bulk production of parts. These parts are used in a wide range of applications from automotive industries to micro-devices in bioengineering. Manufactured parts are required to be precise in their final dimension, and since the billet material undergoes significant plastic deformation during forming, billet material characterization and prediction of final form is essential. In this study, miniaturized bowl-shaped samples of 3003-H14 aluminum alloy were formed using a die and punch manufactured using the stereolithography (SLA) additive manufacturing method. Tensile testing was performed in order to characterize the material properties of the SLA resin. Using the SLA-created die and punch, hemispherical bowl-shaped forms were generated. In order to investigate possible small size effects, experimental load versus displacement results were obtained for billet plate thicknesses of 0.4–0.8 mm. A numerical finite element model was developed to predict the required punch load to manufacture various thickness bowl-shaped forms. A comparison was made between the load verses displacement curves for the different thicknesses, and the numerical model was validated by the experimental results. The validated computational model can then be used to predict the process parameters prior to starting bulk production. Finally, a model with grains was developed and simulated to show the virtual microstructural morphology of the circular plates before and after the forming operation.
Measurement Errors and Uncertainty Estimation of an Experimental Set Up Using a 2D PIV Technique
Authors: Barbosa Flávia V. , Costa Carlos A. P. , Teixeira Senhorinha F. C. F. , Teixeira José C. F. 
Published: January 2020

Abstract
The study of the flow interaction and the heat transfer between air jets and a surface is of paramount importance in industrial processes that apply multiple air jet impingement. To ensure a good performance of the process, high heat transfer rates and uniformization of the flow over the target plate are required. To perform this analysis, a PIV technique was implemented for the measurement of the velocity fields of the flow. However, as any real experiment, the values recorded by the PIV method are subjected to several errors that compromise the reliability and accuracy of the measurements. These errors can have different sources, from the installation and alignment to the particles seeding and calibration procedure. To determine an interval that contains the measurement error, the uncertainty quantification is crucial. In that sense, this paper focus on the identification of measurement errors and uncertainty quantification of an experimental set up specially built for the analysis of the interaction between a non-isothermal jets and non-flat surfaces moving perpendicularly to the jet axis. To ensure the reliability of the results, preliminary tests were performed to guarantee a uniform and stable flow and to determine the range and conditions of operation. In addition, this work presents an analysis of the system, and the source of errors are identified, quantified and, when possible, corrected. The particle seeding, which consists of olive oil droplets, is characterized and its efficiency for the flow tracking is analysed. The test facility was tested to fully characterize the flow field in terms of mean velocity profile and turbulence intensity over a wide range of Reynolds numbers and temperature. Several velocity fields are then measured until convergence of the flow quantities is reached. The combination of these measurements with high spatial resolution and low measurement errors allow to obtain accurate and precise measurement values.