bluuebunny/crossref_metadata_2025_split huggingface dataset:
Euler-Lagrange Simulations of Bubble Cloud Dynamics Near a Wall
Authors: Ma Jingsen , Hsiao Chao-Tsung , Chahine Georges L. 
Published: April 2014

We present in this paper a two-way coupled Eulerian-Lagrangian model to study the dynamics of microbubble clouds exposed to incoming pressure waves and the resulting pressure loads on a nearby rigid wall. The model simulates the two-phase medium as a continuum and solves the N-S equations using Eulerian grids with a time and space varying density. The microbubbles are modeled as interacting spherical bubbles, which follow a modified Rayleigh-Plesset-Keller-Herring equation and are tracked in a Lagrangian fashion. A two-way coupling between the Euler and Lagrange components is realized through the local mixture density associated with the bubbles volume change and motion.
Using this numerical framework, simulations involving a large number of bubbles were conducted under driving pressures of different frequencies. The results show that the frequency of the driving pressure is critical in determining the overall dynamics: either a collective strongly coupled cluster behavior or non-synchronized weaker multiple bubble oscillations. The former creates extremely high pressures with peak values orders of magnitudes higher than that of the excitation pressures. This occurs when the driving frequency matches the natural frequency of the bubble cloud. The initial distance between the bubble cloud and the wall is also critical on the resulting pressure loads. A bubble cloud collapsing very close to the wall exhibits a cascading collapse with the bubbles farthest from the wall collapsing first and the nearest ones collapsing last, thus the energy accumulates and then results in very violent pressure peaks at the wall. Farther from the wall, the bubble cloud collapses quasi spherically with the cloud center collapsing last.
Requirements Analyses to Support a Material Information Model for Sustainability
Authors: Harinder Arvind , Witherell Paul , Morris K. C. 
Published: April 2014

Materials, and therefore material selections, influence the sustainable impact of a product from beginning to end-of-life. With improved access to material information, product designers can attain newfound insight into the sustainability implications of their design decisions. Insight to lifecycle tradeoffs requires access to both upstream and downstream information at design time. This access can be facilitated by information transparency between the different information representations assumed by a product throughout its lifecycle. A well-constructed Material Information Model (MIM) can provide the necessary access, and therefore the desired insight.
In this paper we present an initial set of requirements that a MIM for sustainability must support to provide the desired design-time information access. Using these requirements as guidelines, we then analyze several information representations currently available for information management at various stages of the lifecycle. We compare and contrast the extent to which these representations meet the information needs of the MIM, using example implementations as guidelines. We discuss the level to which information synthesis may be achieved given the varying degrees to which the MIM requirements are met. Finally, we introduce where synthesis challenges lie and the steps required to overcome them.
A Simple 2D Wheelchair Positioning: Correcting IMU’s Data Using One Encoder and Applying Kalman Filtering
Authors: Salimi Zohreh , Ferguson-Pell Martin W. 
Published: April 2014

Inertial Measurement Units (IMU) are widely used for spatial positioning. They are well known, however, for signal drift. A common way of overcoming the drift is to use Kalman Filtering. In this study, we have undertaken some experiments during wheelchair propulsion, recording data with an IMU, an Encoder (tachometer) and an Optotrak (motion analysis system). We then applied Kalman filtering (with two approaches) to IMU’s data. Eventually, in order to verify Kalman’s results, they were compared to Optotrak’s data.
As result of this study, 2D wheelchair tracking can be done with acceptable precision, using one IMU and one Encoder and applying Kalman filtering. Kalman filtering with approach B was a better predictor of subject’s spatial position than approach A. Kalman and even IMU’s results for rotation were of good accuracy; therefore IMU’s data can be used to find all angular characteristics of subject’s position, even without applying Kalman filtering, if the offsets are precisely found through a stationary test.
A Probabilistic Strength Distribution Model in Predicting Damage Evolution due to Thermo-Oxidation of Polymeric Matrix Composites
Authors: Liang Jianyong , Pochiraju Kishore 
Published: April 2014

Thermal oxidation growth and damage evolution are highly coupled as oxidative reactions produce thermal stress and weaker materials leading to crack growth, which in turn accelerates the penetration of oxide layers deeper into the structure. Oxygen diffusion-reaction model can predict the time-dependent oxidation state and evolution of oxide layers in unidirectional composites. With given oxidation state and presumed initial cracks, extend finite element method (XFEM) can be used to calculate the damage evolution due to oxidation-induced stress in the composites. These two models run iteratively to predict the oxidation degradation of polymer composites serving at high temperature.
A probabilistic strength distribution model is formulated in this research to represent the scatter of mechanical properties of composite materials and initiate discrete cracks with Hashin failure criteria. With initiated discrete cracks, damage evolution due to high-temperature thermal oxidation can be calculated. The oxidation growth and damage evolution predicted correlate well with experimental observations. The probabilistic strength distribution model enables crack initiation and damage evolution prediction of use-life and durability of composites structures operating at high temperatures.
Multi-Objective Optimal Control Design With the Simple Cell Mapping Method
Authors: Sardahi Yousef , Naranjani Yousef , Liang Wei , Sun Jian-Qiao , Hernandez Carlos , Schuetze Oliver 
Published: April 2014

Controls are often designed to meet different and conflicting goals. Consider the well-known LQR optimal control. The performance index contains a response measure and a control penalty, which are conflicting requirements. Proper linear or nonlinear combinations of the conflicting objective functions have led to single objective optimization problems. However, such a single objective optimization is dependent on the combination algorithm, and only provides a narrow window of all possible optimal solutions that a system may have.
Multi-objective optimization provides a set of optimal solutions, known as Pareto set. There have been many studies of search algorithms for Pareto sets of multi-objective optimization problems for complex dynamical systems. Recently, the simple cell mapping (SCM) method due to C.S. Hsu has been found to be a highly effective tool to compute Pareto sets. This paper applies the SCM method to several control design problems of linear and nonlinear dynamical systems. The results of the work are very exciting to report.
Effect of Externally Applied Stresses on the Moisture Diffusion Characteristics of Epoxy Glass Composites
Authors: Stoffels Mark T. , Miller David A. 
Published: April 2014

A model is proposed which relates externally applied tensile stresses to changes in absorption capacity as well as diffusion rate. The model postulates that changes seen in the diffusion process are the result of stress-dependent changes in the free volume of the epoxy resin. The free volume changes of the resin are calculated through laminate plate theory, which itself becomes a function of fiber angle as well as a host of elastic properties of the constituents. Consequently, according to the proposed model, changes in diffusion parameters are dependent upon the magnitude of applied stress, the loading angle, as well as elastic properties of the constituents.
Additionally, a finite element model is presented. The proposed finite element model establishes an analogy between thermal and mass diffusion for use in solving the moisture diffusion problems, both in free and stressed states. Input parameters for the FE model are found through use of the previously established mathematical diffusion model.
In order to experimentally verify the proposed models, a series of epoxy glass laminate samples were manufactured at varying fiber angles and immersed in a moist environment while subjected to varying levels of tensile loading. Weight gain measurements were recorded throughout the diffusion process until full saturation was achieved. The experimental values exhibited excellent agreement with both the suggested theoretical model and the finite element model.
Mechanical Properties of a Photopolymerizable Hydrogel for Intervertebral Disc Replacement
Authors: Schmocker Andreas , Khoushabi Azadeh , Pioletti Dominique P. , Bourban Pierre-Etienne , Manson Jan A. , Moser Christophe 
Published: April 2014

We report on the modeling and experimental validation of a photopolymerizable hydrogel for the replacement of the interior of the intervertebral disc (so called Nucleus Pulposus).
The hydrogel is initially injected in its liquid form and then photopolymerized inside via a small catheter. The light necessary for the photopolymerization is constrained to a small light guide to keep the surgical procedure as minimally invasive as possible.
During polymerization, the material’s absorption and scattering coefficients change and directly influence local polymerization rates and hence the mechanical properties. Quantitative scattering and absorption values as well as monomer conversion rates of the hydrogel sample were validated using a Monte Carlo model for photopolymerization. By controlling the input light pattern, local material properties can be engineered, such as elastic modulus and swelling ratio to match the set of requirements for the implant.
Experiments were conducted by polymerizing a hydrogel in a column-like volume using an optical fiber for light delivery. Quantitative scattering and absorption values as well as monomer conversion rates of the hydrogel sample were validated using a newly established Monte Carlo model for photopolymerization. The results were used to study and predict 3D polymerization patterns for different illumination configurations. Swelling ratio and elastic modulus were measured as a function of monomer conversion. Preliminary results on hydrogel fatigue tests in an in-vitro bovine disc will be shown.
Analytical Model for Estimating Knee Loads During Ladder Climbing
Authors: Giachetti Robert S. , Danek Kari A. 
Published: April 2014

We present a simple two-dimensional analytical model that estimates the knee joint loading during vertical ladder climbing. By developing a model with simplification assumptions, such as vertical ascent with no whole-body angular acceleration, we can grossly estimate knee loads under dynamic conditions using posture and whole-body acceleration. The model presented demonstrates that upward whole-body acceleration influences the knee load on the leading leg of the climber during ladder mounting and climbing.
In an effort to define the preferential departure acceleration during ladder ascent for use with the model presented, we also present preliminary data of the initial step onto a fixed ladder. These data are combined with the model at the moment of initial stance foot departure to generate preliminary knee loading estimates. Where appropriate and possible, the authors have attempted to compare and validate the analytical model with published knee loading.
Numerical Analysis on Nanofluid Mixed Convection in Triangular Ducts Heated by a Constant Heat Flux
Authors: Manca O. , Ricci D. , Tamburrino S. 
Published: April 2014

The enhancement of heat transfer represents a very important issue regarding several industrial heating or cooling equipments. This goal can be achieved by means of different techniques; for example, by adopting passive methods like changing flow geometries or by enhancing the thermal conductivity of the working fluids. Thus, an innovative way of improving the thermal conductivity of base fluids consists into introduce suspended small solid nanoparticles.
In this paper a numerical investigation on laminar mixed convection with Al2O3/water based nanofluids in a triangular channel is presented. Duct surfaces were heated by means of a constant and uniform heat flux. The analysis was performed in laminar steady state regime for particle size in nanofluids equal to 38 nm, by adopting a single-phase model approach. The base fluid was water and alumina (Al2O3) nanoparticles were dispersed at different concentrations. Different Richardson number values were considered in order to solve a 3-D model of triangular duct. Results are presented for the fully developed regime flow in terms of surface shear stress and heat transfer convective coefficient, Nusselt number and required pumping power profiles. Comparisons with results related to the fluid dynamic and thermal behaviors are carried out in order to evaluate the enhancement due to the presence of nanoparticles in terms of volumetric concentration. The increase of average convective heat transfer coefficients and Nusselt number values for increasing values of Richardson number and particle concentration is observed by analyzing the obtained results. However, also wall shear stress and required pumping power profiles increase as expected.
Experimental Vehicles Program Aides in Innovative Hands-On Learning Experiences
Authors: Foroudastan Saeed , Thompson Brigette 
Published: April 2014

The Experimental Vehicles Program (EVP) was created in 2004 as an umbrella program for five different undergraduate experimental vehicle design teams. These projects consist of the Solar Vehicle, Moonbuggy, Baja SAE, Formula SAE, and Solar Boat. The goal of the EVP is to foster undergraduate student development through hands-on construction of experimental vehicles with the guidance of faculty mentors and partnerships with both national and international industry leaders.
Each EVP project performs a vital function in the professional development of students. The projects provide a forgiving environment in which students can test their classroom knowledge in a real-world setting and learn important skills such as leadership, effective communication, and working as a team member. Furthermore, the students in the EVP develop highly versatile and qualified skill sets that will allow them to fill various positions within the workplace. In the past 90% of EVP graduates have been able to obtain highly regarded national and international positions upon graduation due to their real-world hands-on experience gained throughout their involvement in the EVP. Each year the EVP sponsors up to sixty interdisciplinary students that come together in peer-led teams to combine and expand upon their classroom knowledge in building innovative vehicles. The successes of the MTSU EVP have been recognized by becoming the national model for hands-on engineering education; helping engineering students take classroom knowledge and apply it to real-world situations. Students work in teams to annually design, construct, and test novel vehicle designs for participation in national and international competitions. Due to the competitive nature of each of the events, students must use cutting edge technology and design methods in order to create the best entries possible. Often times this means creating partnerships with industry leaders who help mentor the students from the design conception, the fabrication, through the manufacturing of each vehicle. These partnerships benefit both the students and the companies; students are able to create real-world contacts and gain a working knowledge of the industry that they cannot learn in the classroom. Furthermore, the students are able to use the contacts to garner equipment like solar panels and wheels. Likewise, the companies are able to receive recognition at national and international competition as program sponsors are advertised on the competition vehicles. Moreover the industries are able to build relationships with future employees who have real-world experience and who have become intimately involved with specialized technology such as “green energy”.
Optimisation of Conjugate Elliptical Cooling Channels With Internal Heat Generation
Authors: Olakoyejo Olabode Thomas , Bello-Ochende Tunde , Meyer Josua Petrus 
Published: April 2014

This paper presents the development of the three-dimensional flow architecture of conjugate cooling channels in forced convection with internal heat generation within the solid for an elliptical cooling channel configuration. The main objective was to optimise the configuration in such a way that the peak temperature was minimised subject to the constraint of the fixed global volume of solid material. The cooling fluid was driven through the channels by the pressure difference across the channel.
The structure had three degrees of freedom as design variables: elemental volume, channel hydraulic diameter and channel-to-channel spacing. The shape of the channel is allowed to morph to determine the best configuration that gave the lowest thermal resistance. A gradient-based optimisation algorithm was applied in order to search for the best optimal geometric configuration that improved thermal performance by minimising thermal resistance for a wide range of dimensionless pressure difference. The effect of porosities, applied pressure differences and heat generation rate on the optimal geometry was reported. There are unique optimal design variables for a given pressure difference. Results obtained show that the effects of dimensionless pressure drop on minimum thermal resistance were consistent with those obtained in the open literature.
On Development of a Semi-Mechanistic Wall Boiling Model
Authors: Das Saurish , Punekar Hemant 
Published: April 2014

In modern cooling systems the requirement of higher performance demands highest possible heat transfer rates, which can be achieved by controlled nucleate boiling. Boiling based cooling systems are gaining attention in several engineering applications as a potential replacement of conventional single-phase cooling system. Although the controlled nucleate boiling enhances the heat transfer, uncontrolled boiling may lead to Dry Out situation, adversely affecting the cooling performance and may also cause mechanical damage due to high thermal stresses. Designing boiling based cooling systems requires a modeling approach based on detailed fundamental understanding of this complex two-phase heat and mass transfer phenomenon. Such models can help analyze different cooling systems, detect potential design flaws and carry out design optimization.
In the present work a new semi-mechanistic wall boiling model is developed within commercial CFD solver ANSYS FLUENT. A phase change mechanism and wall heat transfer augmentation due to nucleate boiling are implemented in mixture multiphase flow framework. The phase change phenomenon is modeled using mechanistic evaporation-condensation model. Enhancement of wall heat transfer due to nucleate boiling is captured using 1D empirical correlation, modified for 3D CFD environment. A new method is proposed to calculate the local suppression of nucleate boiling based on the flow velocity, and hence this model can be applied to any complex shaped coolant passage. For different wall superheat, the wall heat fluxes predicted by the present model are validated against experimental data, in which 50-50 volume mixture of aqueous ethylene glycol (a typical anti-freeze coolant mixture) is used as working fluid. The validation study is performed in ducts of different sizes and shapes with different inlet velocities, inlet sub-cooling and operating pressures. The results are in good agreement with the experiments. This model is applied to a typical automobile Exhaust Gas Recirculation (EGR) system to study boiling heat transfer phenomenon and the results are presented.
Transition From Low Cycle to High Cycle in Uniaxial Fatigue
Authors: El-Sayed Mohamed E. M. 
Published: April 2014

Fatigue is the most critical failure mode of many mechanical component. Therefore, fatigue life assessment under fluctuating loads during component development is essential. The most important requirement for any fatigue life assessment is knowledge of the relationships between stresses, strains, and fatigue life for the material under consideration. These relationships, for any given material, are mostly unique and dependent on its fatigue behavior.
Since the work of Wöhler in the 1850’s, the uniaxial stress versus cycles to fatigue failure, which is known as the S-N curve, is typically utilized for high-cycle fatigue. In general, high cycle fatigue implies linear elastic behavior and causes failure after more than 104 or 105 cycles. However. the transition from low cycle fatigue to high cycle fatigue, which is unique for each material based on its properties, has not been well examined. In this paper, this transition is studied and a material dependent number of cycles for the transition is derived based on the material properties. Some implications of this derivation, on assessing and approximating the crack initiation fatigue life, are also discussed.
Driveline Configuration and Terrain Effect on Slippage and Efficiency of a 6×6/6×4 Truck
Authors: Vantsevich Vladimir V. , Murphy Dennis , Bortolin Gianantonio , Farley Blair , Judd Gabriel 
Published: April 2014

The power distribution between driving wheels has been shown to have a significant impact on vehicle energy efficiency, but there has only been limited research in this area. As shown in this paper, the wheel power distribution is largely dependent on the power dividing units (PDUs) which split/vector power between the driving wheels. The performance of a particular driveline system will also depend largely on the terrain conditions the vehicle encounters.
This paper presents an analysis of PDU configurations in 6×6/6×4 terrain trucks. The vehicle efficiency is evaluated in a wide variety of typical operating conditions including varying surface types, speeds and accelerations, and slope conditions. An analytical method is presented which can be used to determine the tire circumferential forces and slippages. Finally, an analysis of the effects of the driveline configuration, terrain, and surface type on truck transportation efficiency is presented for three PDU combinations.