bluuebunny/crossref_metadata_2025 huggingface dataset:
High Porosity and High Pore Density Thin Copper Foams for Compact Electronics Cooling
Authors: Panse Sanskar S. , Singh Prashant , Ekkad Srinath V.
Published: January 2019

Porous media like open celled metal foams inherently provide a high heat transfer area per unit volume due to their interconnected cellular structure and are lightweight. High pore density metal foam because of its small overall dimensions and micro feature size shows promise in thermal packaging of compact electronics. An experimental study was carried out to evaluate thermal performance of high porosity (95%) and high pore density (90 PPI) copper foam of size 20 mm × 20 mm × 3 mm in buoyancy induced flow conditions and compared with a baseline smooth surface. The enhanced surface showed about 15% enhancement in average heat transfer coefficient over the baseline case. To optimize the performance further, the foam sample was cut into strips of 20 mm × 5 mm × 3 mm and attached symmetrically on the central 20 mm2 base surface area with inter-spacing of 2.5 mm. This new configuration led to further 15% enhancement in heat transfer even with 25% lesser heat transfer area. This is significant as heat transfer is seen as a strong function of permeability to flow through the structure over heat conduction through it. To test this hypothesis, a third configuration was tested in which the strips were further cut into blocks of 4 mm × 4 mm × 3 mm and attached in a 3 × 3 array on to the base surface. Here, only 36% of the central 20 mm2 base surface area was covered with foam. The heat transfer performance was found to be within ± 10% of the initial metal foam configuration, thereby, supporting the hypothesis. Performance was seen to decrease with increase in inclination from 0° to 30° to 90° with respect to the vertical.
Cubic Formula for Determination of the Drop Size During Atomization of Liquid Jets in Co- and Cross-Flow of Air
Authors: Lee T.-W. , Park Jung Eun , Kurose Ryoichi
Published: January 2019

Using the integral formulation of the conservation equations as in our previous work, we can determine the drop size and its distributions in liquid sprays in co- and cross flow of air. The energy balance dictates that the initial kinetic energy of the gas and injected liquid be distributed into the final surface tension energy, kinetic energy of the gas and droplets, and viscous dissipation incurred. The mass and energy balance for the spray flows render to an expression that relates the drop size to all of the relevant parameters, including the gas- and liquid-phase properties and velocities. The results agree well with experimental data and correlations for the drop size. The solution also provides for drop size-velocity cross-correlation, leading to drop size distributions based on the gas-phase velocity distributions. These aspects can be used in estimating the drop size for practical applications, in synthesizing the data as a function of relevant variables, and also in integration into CFD for atomization algorithm.
Development of Test Rigs to Investigate Fluid Flow and Heat Transfer in a Stirling Engine Heater Head
Authors: Yadav Pawan Kumar , Qiu Songgang , Yanaga Koji
Published: January 2019

To study the fluid flow and heat transfer in a Stirling Engine Heater Head (HH), two benchtop test rigs were designed and manufactured. One is to evaluate flow loss in oscillating flow conditions and another is to evaluate heat transfer in unidirectional flow conditions. The main test section-heater head, is additively manufactured; the test section also consists of an additively manufactured regenerator and a heat rejecter. For fluid flow test rig, a linear actuator from Parker generates and maintains the oscillating flow by driving a piston in sinusoidal motion. The piston is sealed against the charged fluid using Trelleborg seals. At room temperature, by varying the charge pressure, frequency, and stroke length, multiple test conditions can be achieved. For heat transfer test rig, a Gast’s high-flow, low-pressure compressed air blower is used to deliver the flow. The data acquisition (DAQ) is comprised of National Instruments’ cDAQ and modules to measure the piston’s motion in real time, pressure with Kistler’s pressure transducers, and the temperatures with OMEGA’s thermocouples, located at both the inlet and outlet of the heater head. Presented also are the testing procedures, some expected results, and the Sage outputs that will be used to check against the measured data from the test rigs, including some preliminary results. Based on the preliminary results, pressure and position curves were sinusoidal, which is expected of oscillating motions, meaning the test rig is operating well.
Estimation Method of 3D Position of Guidewire in Endovascular Treatment
Authors: Yamamoto Hirohito , Mori Koji , Saito Takashi , Kadowaki Hiroko
Published: January 2019

Intravascular treatment is known as one of effective treatment methods for cerebral aneurysms. One problem of this therapy is that an intravascular treatment device unexpectedly moves and a tip of the device strongly contacts on a vessel wall. This unexpected movement of the device causes vascular injury. In actual treatment, 2D X-ray image is used. It is difficult for an operator to estimate 3D position of the device from the 2D X-ray image. In this study, we propose estimation methods for 3D position of devices using a X-ray image and a 3D blood vessel model.

At the first step of estimation procedure, a 3D position of X-ray image, a 3D blood vessel model and X-ray source (Xs) are determined by 2D/3D registration method. The actual 3D position of the device tip (P) is placed on the straight line between Xs and P. Moreover, its position is limited within the 3D vessel model. From characteristics, the 3D position of the device tip is estimated. In this study, two methods to estimate the 3D position of the device are proposed. First: A closest point to the straight line from the center line of the blood vessel model is defined as the position in 3D space of the guidewire (one-point estimation method). Second: A mean value of points on the straight line inside the blood vessel model is defined as the position in 3D space of the guidewire (average estimation method). The accuracy of estimation methods depends on angle of X-ray irradiation. In this study, the relationship between the accuracy of estimation methods and the angle of X-ray irradiation. The estimation accuracy was investigated using numerical calculation.

In the case of a simple blood vessel shape, the error of the estimation was proportional to the angular difference between an ideal and an actual. The errors of the estimated arc length parameter at the ideal angle of X-ray irradiation were 0.002 mm and 0.078 mm, respectively. This result shows that this method is effective for simple blood vessel shape. In future work, other factors to affect the accuracy are also investigated.
Rese_Q: UGV for Rescue Tasks Functional Design
Authors: Quaglia Giuseppe , Cavallone Paride
Published: January 2019

The aim of this paper is to show the functional design of the prototype called Rese_Q01. The characteristics required for this prototype are defined by the competition “RoboCup Rescue”. The competition evaluates robot’s capabilities in four suites: Maneuverability, Mobility, Dexterity and Exploration. In add, the final step of the challenge is the readiness check of system sensors in order to locate victims and dangerous situations. A snake-like architecture, using a modular approach, inspires the prototype Rese_Q01. The robot is composed by a variable number of modules interconnect by multi degree of freedom joints. The modular approach allows configuring the robot in the best way for specific tasks. A specific module can be equipped with different sensors and with a hand effector for specific tasks. Moreover, the modular approach is also employed for the joints. The paper presents the design requirements resulting from the use in post-disaster monitoring operations, the mechanical synthesis procedure and the functional design of the mobile robot. Furthermore, the traction system and the trajectory control are shown.
The Mechanistic Process Comparison Between a Novel Slotted Injection Manifold Versus the Multiple Injection Manifold of a Low Pressure Square Type Atomic Layer Deposition Reactor
Authors: Coetzee Rigardt Alfred Maarten , Jen Tien-Chien
Published: January 2019

Advanced manufacturing techniques have obtained global interest, especially fabricating nanotechnology products. One such technique called atomic layer deposition (ALD) has without doubt manifested itself as an attractive key-enabling nanotechnology that is able to deposit ultrathin, uniform, conformal and pinhole-free nano-films on complex topography. It is utilized in fabrication of superconductors, solar cells, fuel cells, microelectronics, and medical equipment, among other applications. Nonetheless, the ALD process properties and thermal, chemical and flow behaviors are still not well enough understood to provide detailed information, resulting in numerous impasses. In this study, a novel slotted inlet manifold is designed and analyzed in comparison to that of the standard spliced eight-inlet manifold that is currently adopted in a Gemstar 6 reactor. By means of computational fluid dynamics (CFD) the study is centered in observing the impact on the deposition rate due to the different flow patterns of the two ALD reactor designs. The film material of interest is Al2O3 fabricated by the sequential injection of TMA and O3 precursors with argon gas as the purge substance in the ALD reactors. The numerical model adopts the governing laws of the conservation of mass, momentum, energy, species, and kinetic chemical reactions to analyze the behavior in a reactor scale domain. These equations are solved by using the software ANSYS Fluent and ChemkinPro. The end results are validated by available literature.
Effect of Hold-Time Interspersed With Cyclic Loading on Corrosion Fatigue Crack Growth Rate of a Steel in Sodium Chloride Solution
Authors: Prakash Raghu V. , Sampath Dhinakaran
Published: January 2019

Corrosion fatigue growth behavior of structural steels at low cyclic frequency is characterized by an increase in crack growth rate in the threshold and Paris regions, due to the simultaneous action of cyclic mechanical load (fatigue) and corrosive environment. Knowledge on the effect of load sequence on corrosion fatigue crack growth is important to set out the realistic design and prognosis criteria for components operating under corrosive environments.

In this study, the corrosion fatigue crack growth rate under the effect of hold-time (1000s), at a maximum stress intensity factor (Kmax), interspersed during cyclic load on was studied experimentally on a Mn-Ni-Cr steel under 3.5% NaCl solution at a constant stress intensity factor range (ΔK) of 15 MPa √m; the corrosion crack growth rate was evaluated for three different frequencies of: 0.01, 0.1 and 1 Hz. As a result of hold time at the peak load, the exposure time for the crack-tip to interact with the environment increased, which could enhance the corrosion crack growth rates. To verify if this corrosion effect can be contained, electrode potential of (−) 850 mV and (−) 950 mV SCE was applied to the specimen to reduce the extent of corrosion contribution to crack growth rate.

The fatigue crack growth rate (da/dN) increased when the frequency was decreased from 1 to 0.01 Hz at all electrode potentials. However, the crack growth rate at 0.01 Hz increased by an order of magnitude with a tensile hold at Kmax for 1000 s compared with the crack growth rate during continuous cyclic load for a given electrode potential. The crack growth rate reduced when the electrode potential was decreased to −950 mV SCE. The enhancement of corrosion fatigue crack growth rate with the introduction of a hold-time is explained using crack-tip strain rate assisted anodic dissolution.
Localized Fatigue Response Evaluation of Weld Regions Through Cyclic Indentation Studies
Authors: Prakash Raghu V. , Madhavan Krishna , Prakash Anirudh R. , Dhaka Pankaj
Published: January 2019

An experimental investigation of the fatigue response of commonly used structural stainless steel — SS 304 L(N) and SS 316 L(N) — and its weld was carried out through automated cyclic ball indentation (ABI). A Tungsten Carbide (WC) spherical ball indenter of 1.57 mm diameter was used for compression-compression fatigue testing of the specimen under load control at a low frequency of loading (typically 0.1 Hz to 1 Hz). The force-displacement response during fatigue loading was logged continuously during fatigue test and the data was analyzed to extract details such as variations in: total depth of penetration, loading and unloading slopes, loading/unloading intercept, displacement range as a function of number of cycles. From the results, one could identify an unsteady response of material during cyclic loading after some cycles of fatigue loading — typical of failure; this input was used to compare the fatigue response of different zones of the weld.

Even though the applied frequency of loading is relatively less (∼ 1 Hz), due to the high levels of plastic deformation that is developed during the indentation process, one could expect an effect of strain rate on the fatigue response during cyclic ball indentation. To verify this, experiments were carried out at three distinct frequencies of 0.1 Hz, 0.5 Hz and 1 Hz for a given loading condition. Further, it was observed that the material response in weld region is the best, followed by the base metal. This can be corroborated with the weld microstructure that is obtained as a consequence of processing. Frequency of loading did not have significant influence on the fatigue failure life.

Numerical simulation of cyclic ball indentation was carried out to extract some relevant parameters for failure life such as mean stress and local stress ratio. This will serve as input to correlation of failure life data obtained from conventional specimens.
Dynamic Modeling System to Determine Stopping Distances of Mobile Underground Coal Equipment
Authors: Jobes Christopher C. , Carr Jacob
Published: January 2019

In underground coal mines, miners face the hazard of being struck or pinned by a piece of mobile mining machinery. Proximity detection systems have been developed and are used by the industry to protect miners around these machines by detecting the presence of the miners and automatically issuing warnings or disabling machine motion when a miner is in potentially dangerous proximity. These systems were originally developed for continuous mining machines, slow-moving machines that move on bulldozer-style tracks, and are now mandated by the Mine Safety and Health Administration (MSHA) to be used on continuous mining machines. These systems are now being adapted to other underground vehicles, such as shuttle cars, scoops, and battery haulers — vehicles that move on rubber tires at much higher speeds. There are concerns that the detection range of these systems may not provide for an adequate stopping distance on these faster moving machines. To address these concerns, researchers have developed a dynamic modeling system to determine the stopping distance of mobile underground coal equipment. This model can be used in conjunction with worker escapability data and/or information on interaction with other vehicles to provide insight into whether or not proximity detection systems will be adequate for the underground mining workplace. This paper details the background, development, and operation of the resulting application software, focusing on the utility of the graphical user interface to visualize the generated data. The refined data developed by this process can then be utilized by mine operators and proximity detection system manufacturers to more accurately determine the detection range needed to provide effective protection for miners working in an underground mining environment.
Heat Transfer Enhancement in Wavy Micro-Channels Through Multiharmonic Surfaces
Authors: Moon Justin , Pacheco J. Rafael , Pacheco-Vega Arturo
Published: January 2019

In this study, three-dimensional numerical simulations are performed to investigate heat transfer enhancement in multi-harmonic micro-scale wavy channels. The focus is on the influence of channel surface-topography, modeled as multi-harmonic sinusoidal waves of square cross-sectional area, on the enhancing mechanisms. A single-wave device of 0.5 mm × 0.5 mm × 20 mm length, is used as baseline, and new designs are built with harmonic-type surfaces. The channel is enclosed by a solid block, with the bottom surface within the sinusoidal region being exposed to a 47 W/cm2 heat flux. The numerical solutions of the governing equations for an incompressible laminar flow and conjugate heat transfer are obtained via finite elements. By using the ratio of the Nusselt number for wavy to straight channels, a parametric analysis — for a set of cold-water flowrates (Re = 50, 100, and 150) — shows that the addition of harmonic surfaces enhances the transfer of energy and that such ratio achieves the highest value with wave harmonic numbers of n = ±2. Use of a performance factor (PF), defined as the ratio of the Nusselt number to the pressure drop, shows that, surprisingly, the proposed wavy multi-harmonic channels are not as efficient as the single-wave geometries. This outcome is thought to be, primarily, due to the uncertainty associated with the definition of the Nusselt number used in this study, and establishes a direction to investigate the development of a more accurate definition.
Natural Convection Heat Transfer With Horizontal Rectangular Fin Array Using Straight Knurling Patterns on Fins: An Experimental Study
Authors: Chikurde R. C. , Kothavale B. S. , Sane N. K.
Published: January 2019

Natural Convection heat transfer from horizontal rectangular fin array with various knurling patterns is studied experimentally to find the effect of varying surface roughness on the heat transfer rate. The experimental parametric study is performed to investigate the effect of knurl produced surface roughness of fin on heat transfer rate. The parameters like knurling height from base, knurling depth and fin spacing might affect the flow characteristics and hence it is investigated to find the effect on heat transfer coefficient. The knurling is usually accomplished using one or more very hard rollers that contain the reverse of the pattern to be imposed. The result of this study shows that there are some important geometric factors related to knurling affecting the design of fin arrays and also heat transfer augmentation of natural convection heat transfer is observed.
Additive Manufacturing Bead Deposition Based Rotary Tool Path Applications
Authors: Urbanic Ruth Jill , Hedrick Bob
Published: January 2019

Additive manufacturing layer-based solution approaches have been applied for several technologies and systems. Process planning solutions are being developed for planar applications, but rotary applications can benefit from an additive manufacturing ‘rotary layering’ strategy as well. There are systems that have been developed to coat pipes and other rotationally symmetric components, and there are multi-axis applications that would require rotary-like tool paths. Developing and exploring additive rotary tool path applications is the focus of this research. These initial solutions will be applicable for direct energy deposition and thermal spraying models. AM rotary proof of concept tool paths are developed using a commercial CAD/CAM software, and a software development kit (SDK). Selected case studies are presented, with varying levels of geometric complexity.
Feasibility Analysis of Distributed Generation System for Large University Campus
Authors: Allen Amy , Krarti Moncef
Published: January 2019

Distributed electric generation systems are increasingly considered to offset energy costs and carbon emissions of large building complexes. College campuses, with their physical compactness, and diversity in building loads, present a common application for distributed generation systems. This paper presents the analysis approach and the main results of a feasibility study of a distributed generation system to supply electric and thermal energy for a large university campus, incorporating energy efficiency measures, to reduce carbon emissions at minimal life cycle cost.

The presented study uses a load profile developed based on calibrated detailed simulation energy models for prototypical campus buildings. The calibration analysis is carried out using measured energy consumption data, at the individual building level, and the whole-campus level. Several combinations of distributed generation options are evaluated, using an hourly optimization analysis tool, to meet the entire campus hourly electrical and thermal loads. Proposed efficiency measures and distributed generation options are evaluated using different indicators, including life cycle cost and carbon emissions.

The analysis results indicate that implementing energy efficiency measures to reduce electrical and thermal loads before implementing distributed generation options is the most cost-effective approach to reducing the campus’s energy-related carbon emissions. The results of the study are summarized to guide college campuses and managers of other urban districts as they adapt to a changing energy landscape.
Service Robot Design for Uses in Human Centered Environments
Authors: Sohn Kiwon , Morris Ethan , Ulebor Obioma , Currier Thomas , Merrill Shaun
Published: January 2019

This paper presents the development of a service robot platform for various assistive tasks in human-centered environment. The main design objective is to enable the robot to safely navigate indoor areas and to provide cross-platform accessibility to human-users. To accomplish the goal, two technical design requirements which include the rough-terrain locomotive mechanism and the web-server based operating system are addressed and explored in this study. First, the overall control system architecture of the robot which consists of three different layers (human-interaction, environment-interaction and movement) is presented. Then, the mechanical and electronic specification of the robot’s dual drive system and the power management system are described with their design process. The robot’s software platform (which consists of the server, client and real time controller) is also provided for the selected service task. Last, the built platform is tested and evaluated through experimentations in the real world settings.
Thermal Analysis of a High-Temperature Heat Pipe-Assisted Thermal Energy Storage System With Nano-Enhanced Phase Change Material
Authors: Tiari Saeed , Mahdavi Mahboobe , Thakore Viren , Joseph Stacy
Published: January 2019

In this study, the thermal characteristics of a high-temperature latent heat thermal energy storage system assisted by highly conductive nanoparticles and finned heat pipes are investigated numerically. A transient two-dimensional model is developed using the commercial CFD package of ANSYS-FLUENT18.2 to analyze the thermal performance of the storage unit during the charging process. Copper oxide (CuO) and aluminum oxide (Al2O3) are the nanoparticles introduced to enhance the thermal conductivity of the phase change material (PCM) which is potassium nitrate (KNO3) with melting temperature of 335°C. The effects of different types and volume fractions of nanoparticles, as well as the quantities of embedded heat pipes have been studied. The results revealed that increasing the volume fraction of nanoparticles leads to the increase of the melting rate and input heat flux of the system. It was also found that the dispersion of aluminum oxide in the PCM provides a faster charging process in comparison to the case with copper oxide nanoparticles. In addition, the results showed that the quantity of heat pipes has a significant impact on the thermal performance of the storage unit.
Effect of Nozzle-to-Target Spacing on Fin Effectiveness and Convective Heat Transfer Coefficient for Array Jet Impingement Onto Novel Micro-Roughness Structures
Authors: Singh Prashant , Zhang Mingyang , Ahmed Shoaib , Ekkad Srinath V.
Published: January 2019

With recent advancements in the field of additive manufacturing, the design domain for development of complicated cooling configurations has significantly expanded. The motivation of the present study is to develop high-performance impingement cooling designs catered towards application’s requiring high rates of heat removal, e.g. gas turbine blade leading edge and double-wall cooling, air-cooled electronic devices etc. Jet impingement is a popular cooling technique which results in high convective heat rates. In the present study, jet impingement is combined with strategic roughening of the target surface, such that a combined effect of impingement-based and curved-surface area based enhancement in heat transfer coefficient could be achieved. Traditionally, for surface roughening, cylindrical and cubic elements are used. We have demonstrated, through our steady-state experiments, a novel “concentric” shaped roughness element design which has resulted in about 20–60% higher effectiveness compared to smooth target jet impingement, for jet-to-target spacing of one jet diameter. The cubic shaped roughened target yielded about 20% to 40% enhancement in effectiveness, and the cylindrical shaped roughened target yielded 10% to 30% enhancement. Through the plenum pressure measurements, it was found that the addition of the micro-roughness elements does not result in a discernable increment in pressure losses, compared to the standard impingement on the smooth target surface. Hence, the demonstrated configuration with the highest heat transfer coefficient also resulted in the highest thermal hydraulic performance.
Hydrodynamic Recruitment of Leukocytes Is Influenced by Adherent Cell Morphology
Authors: Subramaniam Dhananjay Radhakrishnan , Gee David J.
Published: January 2019

Innate immunity depends on the coordinated activity of multiple leukocytes at or near the site of tissue injury. Previous numerical studies have shown that an adherent leukocyte can hydrodynamically recruit a free-stream leukocyte towards the endothelial surface. Using a computer model we created, we numerically investigated the hydrodynamic recruitment of circulating cells due to the presence of a nearby adherent deformed cell. For circulating cells positioned one diameter or more above the reactive surface and subsequently involved in a glancing (out-of-plane) collision with an adherent cell, the simulation indicated that the free-stream cell could be driven closer to the surface. This behavior was seen to depend, in part, on the offset glancing distance. Furthermore, for a deformed adherent cell a similar effect was observed, but beginning at smaller offset glancing distances. We also examined the binary interaction for a free-stream cell initially less than one diameter above the surface. For fixed offset glancing distances, the binary interaction with a more significantly deformed adherent cell resulted in enhanced recruiting effectiveness, as quantified by the time needed for the cell to descend to a height where receptor-ligand interactions were possible.
Method of Fundamental Solution in Thermoelasticity of Random Structure Matrix Composites
Authors: Buryachenko Valeriy A.
Published: January 2019

One considers linear thermoelastic composite media, which consist of a homogeneous matrix containing a statistically homogeneous random set of aligned homogeneous heterogeneities of non-canonical (i.e. non-ellipsoidal) shape. The representations of the effective properties (effective moduli, thermal expansion, and stored energy) are expressed through the statistical averages of the interface polarization tensors (generalizing the initial concepts, see e.g. [1] and [2]) introduced apparently for the first time. The new general integral equations connecting the stress and strain fields in the point being considered with the stress and strain fields in the surrounding points are obtained for the random fields of heterogeneities. The method is based on a recently developed centering procedure where the notion of a perturbator is introduced in terms of boundary interface integrals estimated by the method of fundamental solution for a single inclusion inside the infinite matrix. This enables one to reconsider basic concepts of micromechanics such as effective field hypothesis, quasi-crystalline approximation, and the hypothesis of ellipsoidal symmetry. The results of this reconsideration are quantitatively estimated for some modeled composite reinforced by aligned homogeneous heterogeneities of non canonical shape. Some new effects are detected that are impossible in the framework of a classical background of micromechanics.
Experimental and Numerical Studies on Dynamic Mechanical Properties of Metal-Polymer Hybrid Materials
Authors: Zhang Yiben , Sun Lingyu , Li Lijun , Wang Taikun , Wang Yantao
Published: January 2019

Metal-polymer hybrid (MPH) materials can integrate the excellent mechanical properties of metal and complex geometry formability of polymer into a single component, which has become an effective way of reducing the weight of automotive semi-structural components. For example, the hybrid steel/thermoplastic polymer has been applied in automotive front-end modules, bumper cross-beams and B-pillars due to its light weight, excellent strength and stiffness, good corrosion resistance and recycling, high integration and reasonable cost. These components are usually subjected to impact or crash loads and the strain rate effect should be taken into account.

This paper aims to experimentally and numerically study the dynamic behavior of MPH materials at different strain rates and provide an accurate and efficient numerical model for crash simulation of vehicles with MPH components.

Firstly, MPH specimens with high strength steel (HSS) and glass fiber-reinforced thermoplastic polymer (GFRTP) were fabricated by direct injection molding adhesion (DIMA) process. Then, the dynamic mechanical properties of MPH specimens under strain rates from 800 s−1 to 2000 s−1 were investigated by Split Hopkinson Pressure Bar (SHPB) experiments. Finally, a strain rate-dependent numerical model was established in ABAQUS software to simulate the dynamic behavior of MPH specimens and validated by experimental results. Three numerical approaches for modeling the interface between the two discrete material phases were considered and compared to examine the level of interaction between two constitute materials. Cohesive zone modeling technique at the interface which saved modeling and characterization time and showed adequate predictive capability proved to be generally applicable to the evaluation of structural concepts in an early vehicle development stage.

This study provides a foundation for the future engineering application of HSS/GFRP hybrid materials and numerical models for automotive crash simulation.
A Path-Generating Motion Control Scheme for a Mobile Robot in the Environment of Obstacles
Authors: Lee Ho-Hoon
Published: January 2019

In this paper, a path-generating motion control scheme is proposed for a unicycle-type wheeled mobile robot navigating through multiple obstacles. The proposed motion control scheme computes the driving force and rotational torque of the robot in real time that drive the robot to a given goal position while avoiding multiple obstacles. The nonholonomic constraints as well as the dynamic equations of the mobile robot are used in the design of the motion control scheme, where a repulsive potential function is used for obstacle avoidance. In the control design, the Lyapunov stability theorem is used as a mathematical design tool. Under certain conditions, the proposed control guarantees asymptotic stability while keeping all internal signals bounded. The effectiveness of the proposed control method has been shown with realistic computer simulations.
3D Numerical Model for Prediction of Percolation Threshold and Piezoresistive Characteristics of Conductive Polymer Filled With CNT
Authors: Han Jun , Sun Lingyu , Li Lijun , Huang Bincheng , Yang Xudong , Wang Taikun
Published: January 2019

As a kind of functional materials, conductive polymer matrix composites filled with carbon nanotube (CNT) has potential application in structural health monitoring. A good formula should have a low percolation threshold and high piezoresistive strain sensitivity, which are always being sought by costly and time-consuming experimental method. Up to date, there is still a lack of numerical models to predict the sharp transition moment in electrical conductivity and mechanical resistance characteristics. This paper aims to establish a three-dimensional (3D) numerical model to observe the conductive network formation, predict the percolation threshold and investigate the piezoresistive characteristics of CNT-filled polymer matrix composites. Additionally, the influence of filler size, filler shape and filler volume fraction on the percolation threshold and piezoresistive characteristics would be investigated. The modeling and numerical simulation method can not only provide theoretical guidance for such a functional composite material, but also could be used in the future study on design and preparation of other conductive composites with two fillers added to improve the piezoresistive strain sensitivity and to decrease the percolation threshold.
Damage Characterization of Carbon and Glass Fiber Composite Plates Subjected to Low-Velocity Impact Using Thermography
Authors: Al-Athel Khaled S. , Alomari Ahmed , Arif Abul Fazal M.
Published: January 2019

Composites are prone to delamination damage when impacted by low velocity projectiles because of the poor through-thickness strength. Therefore, some of the problems with composites are their poor impact damage resistance, weak post-impact mechanical properties, and the difficulty to inspect the impacted area by nondestructive means. Damage characterization of composite materials requires a scientific methodology, knowledge of polymeric materials, and direct field experience. In this work, low-velocity impact response of composite laminates was experimentally studied using drop-tower to determine the energy absorption. Three types of composites were used: carbon fiber, glass fiber, and mixed fiber composite laminates. In addition, these composites were characterized using thermography to quantify their post impact damage. It was found with the 3D temperature distribution that a strong correlation can be determined between the measured temperatures at the impact region with the quantification of the damage using thermal imaging with advanced mid-wave camera.
Calculation of Evaporation From Fukushima NPP Spent Fuel Pools
Authors: Shah Mirza M.
Published: January 2019

Prediction of evaporation rates from spent fuel pools of nuclear power plants in normal and post-accident conditions is of great importance for the design of safety systems. A severe accident in 2011 Fukushima nuclear power plant caused failure of cooling systems of its spent fuel pools. The post-accident evaporation from the spent fuel pools of Fukushima units 2 and 4 is compared to a model based on analogy between heat and mass transfer which has been validated with a wide range of data from many water pools including a spent fuel pool. Calculations are done with two published estimates of fuel decay heat, one 25 % lower than the other. The model predictions are close to the evaporation using the lower estimate of decay heat. Other relevant test data are also analyzed and found in good agreement with the model.
Wet Gas Compressor Operation and Performance
Authors: Bakken Martin , Bjørge Tor , Bakken Lars E.
Published: January 2019

The continuous demand for oil and gas forces the petroleum industry to develop new and cost-effective technologies to increase recovery from new fields and enhance extraction from existing fields. Subsea wet gas compression stands out as a promising solution for increasing production capacity, utilizing remote regions and reducing costs.

A prerequisite for successful oil and gas production utilizing subsea wet gas compressors is operability. This includes the system’s ability to cope with operational changes, without having to shut down. One of the fundamental operational changes is the liquid content in the inlet pipe, which may fluctuate considerably at certain time intervals. The current study investigates how changes in liquid content impacts compressor performance.

An experimental test campaign has been performed at the Norwegian University of Science and Technology (NTNU). The test facility is an open loop configuration consisting of a single shrouded centrifugal impeller, a vaneless diffuser and a symmetrical circular volute.

The main objectives were to document how the presence of liquid impacts the compressor characteristics and further, how the operating point moves within the characteristics when solely subjected to an increase of liquid content. The compressor was exposed to liquid contents ranging from gas mass fraction 1.0 to 0.60. The test reveals that the compressor pressure ratio at wet conditions is higher in comparison to dry conditions. Care should be taken when analysing stability and surge margins at variations in fluid liquid content. Further, the compressor behaves in a predictable manner, revealing several linear trends, when subjected to stepwise changes in liquid content from a fixed operating point.
Multi-Physics Modeling of Laser Interaction With Surface in Powder Bed Melting Process
Authors: Ahsan Faiyaz , Razmi Jafar , Ladani Leila
Published: January 2019

Powder bed metal additive manufacturing process using laser or electron beam heat source is gaining increasing popularity due to its ability to create complex shaped metallic components. The process is a complex multi-physics process where multiple phases of material exist and laser interacts through multiple physical mechanisms with the surface of these materials and phases. The power absorption depends on optical and thermos-physical properties of the surface and laser type and wavelength. Most of the work conducted in the past have modeled the laser using a moving heat source. These studies typically assume a certain absorption without actual calculation of this power absorption. This study focuses on modeling the process in a more comprehensive manner including the laser physics and evaluating how this physics affects the temperature distribution and build outcome. The results are compared with the conventional techniques where simple Gaussian distribution was used for the power source. The temperature profile obtained with this study was lower than the Gaussian beam.
Numerical Investigation of Internal Forces During Carbon Nanotube Forest Self-Assembly
Authors: Hajilounezhad Taher , Maschmann Matthew R.
Published: January 2019

A time-resolved two-dimensional finite element simulation is developed to model the forces generated during the self-assembly of actively growing CNT populations with distributed properties and growth characteristics. CNTs are simulated as interconnected frame elements that undergo the base growth mechanism. Mechanical equilibrium at each computational node is determined at each time step using the Updated Lagrangian method. Emphasis is placed on the transmission of force to the growth substrate, where catalyst particles reside. The simulated CNT forest structural morphology is similar to that of physical CNT forests, and results indicate that stresses on the order of GPa are transmitted to catalyst particles. The force transmitted to a given catalyst particle is correlated to the rate at which the CNT grows relative to the population averaged growth rate. The effect of diameter-dependent CNT growth rates and the persistence of vdW bonds are also examined relative to the forces generated during forest self-assembly. Results from this study may be applied to the study of CNT forest self-assembly, resultant ensemble forest properties, and force-modulated CNT growth kinetics.
A Method for Constructing Standard Involute Gear Tooth Profile
Authors: Osakue Edward E. , Anetor Lucky
Published: January 2019

A simple but accurate combined computationaland graphical method for creating drawings and solid models of standard involute gears is presented. The method is predicated on the fact that the gear tooth angle at the base circle is fixed for a gear of specified module or size. As the contact point moves along the involute curve from the base circle point through the pitch point to the addendum circle point; the involute and gear tooth contact angles change continuously but their sum is fixed at the value it was at the base circle. This allows the coordinates of points on the involute curve to be generated analytically without employing the roll angle as current available methods. The generated data can be implemented in any computer design drafting (CDD) package platform to create an accurate gear tooth profile. The computations are done with Microsoft Excel which generates the graphical data for the gear tooth profile that are used in the CDD package. The required inputs to the Excel spreadsheet are the gear module size, the pressure angle, the number of teeth and the radial number of steps. A gearset example is considered and created with this method. The solid model of the example gearset in mesh and 2D drawing of the pinion are presented.
Air Flow Velocity Field Validation and Turbulence Studies on a Single Rack Model in Data Centers
Authors: Phan Long , Hu Beichao , Lin Cheng-Xian
Published: January 2019

Due to the rapid growth in IT demands over the past few decades, the market for data centers also increases dramatically. However, thermal management remains a big issue in the design of large-scale data centers. Although best practices are deployed to utilize perforated tiles together with the hot and cold aisles configuration to improve the thermal management, thermal hotspots are inevitable in IT racks, which causes equipment failures and signal interruptions. Thermal hotspots in air-cooled data centers are due to many factors such as insufficient cold air supply from the raised-floor plenum, air recirculation from hot aisle into cold aisle, airflow non-uniformity at the perforated tiles, etc. One of the ways to mitigate such issues is to uniformly distribute the cold air by properly controlling the airflow rate through perforated tiles. In this study, a validation study of the tile airflow and the rack airflow rate ratio of 20% is carried out using an adopted tile model. Also, several turbulence models are thoroughly investigated, and recommendations are provided for the most accurate and less time-consuming turbulence model when applying to a single rack model.
Rattlebacks for Undergraduate Engineers: Modelling Complex Behavior Using Introductory Dynamics and Numerical Methods
Authors: Jones Simon , Kern Kirby
Published: January 2019

Rattlebacks are semi-ellipsoidal tops that have a preferred direction of spin. If spun in, say, the clockwise direction, the rattleback will exhibit stable rotary motion. If spun in the counter-clockwise direction, the rattleback’s rotary motion will transition to a rattling motion, and then reverse its spin resulting in clockwise rotation. This counter-intuitive dynamic behavior has long been a favored subject of study in graduate-level dynamics classes.

Previous literature on rattleback dynamics offer insight into a myriad of advanced topics, including three-dimensional motion, sliding and rolling friction models, stability regions, nondimensionalization, etc. However, it is the current authors’ view that focusing on these advanced topics clouds the students’ understanding of the fundamental kinetics of the body. The goal of this paper is to demonstrate that accurately simulating rattleback behavior need not be complicated; undergraduate engineering students can accurately model the behavior using concepts from introductory dynamics and numerical methods.

The current paper develops an accurate dynamic model of a rattleback from first principles. All necessary steps are discussed in detail, including computing the mass moment of inertia, choice of reference frame, conservation of momenta equations, and application of kinematic constraints. Basic numerical techniques like Gaussian quadrature, Newton-Raphson root-finding, and Runge-Kutta time-stepping are employed to solve the necessary integrals, nonlinear algebraic equations, and ordinary differential equations.

Since not all undergraduate engineering students are familiar with 3D dynamics, a simpler 2D rocking semi-ellipse example is first introduced to develop the transformation matrix between an inertial reference frame and a body-fixed reference frame. This provides the framework to transition seamlessly into 3D dynamics using roll, pitch, and yaw angles, concepts that are widely understood by engineering students. In fact, when written in vector notation, the governing equations for the rocking ellipse and the spin-biased rattleback are shown to be the same, enforcing the concept that 3D dynamics need not be intimidating.

The purpose of this paper is to guide a typical undergraduate engineering student through a complex dynamic simulation, and to demonstrate that he or she already has the tools necessary to simulate complex dynamic behavior. Conservation of momenta will account for the dynamics, intimidating integrals and differentials can be tackled numerically, and classic time-stepping approaches make light work of nonlinear differential equations.
Method to Reduce Drag Coefficient for Fuel Efficiency in Semi-Truck Trailer and Trailer Stability
Authors: Nair Anu R. , Barez Fred , Thurlow Ernie , Ozen Metin
Published: January 2019

Heavy commercial vehicles due to their un-streamlined body shapes are aerodynamically inefficient due to higher fuel consumption as compared to passenger vehicles. The rising demand and use of fossil fuel escalate the amount of carbon dioxide emitted to the environment, thus more efficient tractor-trailer design becomes necessary to be developed. Fuel consumption can be reduced by either improving the driveline losses or by reducing the external forces acting on the truck. These external forces include rolling resistance and aerodynamic drag. When driving at most of the fuel is used to overcome the drag force, thus aerodynamic drag proves an area of interest to study to develop an efficient tractor-trailer design. Tractor-trailers are equipped with standard add-on components such as roof defectors, boat tails and side skirts. Modification of these components helps reduce drag coefficient and improve fuel efficiency. The objective of this study is to determine the most effective geometry of trailer add-on devices in semi-truck trailer design to reduce the drag coefficient to improve fuel efficiency and vehicle stability.

The methodology consisted of CFD analysis on Mercedes Benz Actros using ANSYS FLUENT. The simulation was performed on the tractor-trailer at a speed of 30m/s. The analysis was performed with various types of add-on devices such as side skirts, boat tail and vortex generators. From the simulation results, it was observed that addition of tractor-trailer add-on devices proved beneficial over modifying trailer geometry. Combination of add-on devices in the trailer underbody, rear and front sections was more beneficial in reducing drag coefficient as compared to their individual application. Improving fuel efficiency by 17.74%. Stability of the tractor-trailer is improved due to the add-on devices creating a streamlined body and reducing the low-pressure region at the rear end of the trailer.