bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.