bluuebunny/crossref_metadata_2025 huggingface dataset:
Industry Based “Hands-On” Undergraduate Vibration Course for Engineering and Engineering Technology Students
Authors: Peter Geoffrey J.
Published: October 2013

Modern technology and manufacturing methods often require engineers who understand the fundamental principles of vibration theory and who are also skilled in vibration applications. Simply processing, remembering and applying the material learned from lectures and laboratory experiments with artificial criteria are inadequate.

Hands-on teaching techniques with real-world problems are needed to complete the engineering students’ education. This paper demonstrates how hands-on experiments performed in industry support and increase the students’ understanding of fundamental principles and skill in their applications. Graduates with both knowledge and skill are more competitive in today’s job market.

A one-quarter industry-based vibration course was developed and taught with a hands-on segment at the Manufacturing and Mechanical Engineering and Technology (MMET) program at Oregon Institute of Technology (OIT) - Portland Campus. This novel instructional approach provided students with the opportunity to immediately apply material, learned in class and laboratory, in real-world industry situations with real-world problems.

This instructional approach is applicable in many engineering fields and the author found the mechanical vibrations class particularly well suited for this instructional design style. The hands-on approach, grounded in the vibration course curriculum, provided a direct link to the fundamentals of vibration in industry.

Student comments are included to demonstrate the value perceived by the students. Although this curriculum experiment involved mechanical engineering technology students, it would benefit mechanical engineering students equally well.

In addition, the paper provides a brief description of the industries that participated in this project. Industries were selected because they use vibration based manufacturing, perform extreme testing or design their products to avoid failure due to vibrations.
Piezoelectric Vibration Energy Harvester: Design and Prototype
Authors: Cojocariu Bogdan , Hill Anthony , Escudero Alejandra , Xiao Han , Wang Xu
Published: October 2013

This paper proposes a new approach for vibration energy harvesting analysis. The research investigates and compares efficiencies of a vibration energy harvesting system with two different electric storage interface circuits. One of the interface circuits is the standard interface circuit comprised of four rectifier diodes connected in a classical single phase bridge. The other interface circuit is a newly proposed interface circuit integrated with a voltage multiplier, an impedance converter and an off shelf booster. To validate the effectiveness of the newly proposed interface circuit, a vibration energy harvesting beam system has been developed in connection with this proposed circuit. The harvested efficiency and harvested power output of the system with the two different electric storage interface circuits have been measured and compared.
Pre- and Post-Critical Heat Flux Analyses in a Saturated Refrigerant Flow Boiling System
Authors: Zhang TieJun , Catano Juan , Wang Evelyn N. , Jensen Michael K.
Published: October 2013

Vapor compression refrigeration (VCR) cooling has been identified as a promising solution to ensure the low-temperature sustainable operation of photonics, avionics and electronics in extreme hot weather. With the inherent benefits of saturated flow boiling in a direct VCR cooling cycle, uniform low surface temperature and low solid/liquid thermal resistances can be achieved. However, flow boiling heat transfer performance is limited by the relatively low critical heat flux (CHF) condition because the evaporator inlet flow is already a liquid/vapor mixture. Moreover, for the aforementioned applications, the dissipated heat loads are usually subject to large and transient changes, which could easily cause the evaporating flow to exceed the CHF point. Therefore, it is important to characterize boiling heat transfer in transient VCR evaporators under both pre-CHF and post-CHF conditions. Comprehensive experimental data are reported in this paper to describe the complete forced convection boiling hysteresis at the evaporator exit. Several well-known boiling heat transfer correlations and flow pattern criteria are used to help understand the physics of the hysteresis. An empirical model is developed to reveal the unstable nature of transition flow boiling dynamics. A probability distribution function model is further proposed to predict the droplet size in mist flow and vapor core of annular flow. This study provides more design and operating guidelines for the application of saturated flow boiling systems in renewable power generation and electronics/photonics/avionics cooling industries.
The Design of High Speed Planing Craft Using an Optimization Framework
Authors: Smith Warren F. , Ayob Ahmad F. Mohamad , Ray Tapabrata
Published: October 2013

High speed planing craft as a unique vessel type play key commercial roles in niche passenger ferrying and high value cargo transport. In addition, they are used to support several critical maritime activities such as coastal surveillance, reconnaissance, and life-saving operations and many recreational pursuits. Formal optimization frameworks, despite their significant use across a range of domains, have rarely been proposed and developed to deal with the design challenges of high speed planing craft. Highlighted in this paper is an optimization framework drawing on both domain dependent and domain independent elements for the conceptual and preliminary design of high speed planing craft. A summary of the principal components of the optimization framework are presented, followed by several case study examples. The solvers developed and employed are classified as being population based, evolutionary and stochastic in nature. These characteristics are well suited to design space exploration in all engineering and decision making contexts.

Within the case studies presented, the sample key performance indicators include calm water resistance, resistance in waves, seakeeping and manoeuvring. The concept of scenario-based hydrodynamic design optimization is introduced using an example of a small rescue craft operating in a predefined sea-state. Finally, a multi-objective optimization case study considering total resistance, steady turning diameter and vertical impact acceleration is presented to demonstrate the capability to explore trade-offs while at the same time providing an understanding of the design intent of a basis ship. This work has significant purpose and relevance in both ab-initio and reverse engineering contexts. It also has natural extensions in both depth of analysis and breadth of application.
Neurodynamical Control of the Heart of Freely Moving Animals Including Humans
Authors: Yazawa Toru , Shimoda Yukio , Shimizu Satoru , Katsuyama Tomoo
Published: October 2013

Two kinds of nerves, acceleratory and inhibitory cardio-regulator nerves, innervate the heart. They are known to discharge concurrently to maintain an equilibrium state of the body. The nerves are also known to change their frequency of discharge in a reflexive manner to meet the demand from the periphery; such as augmentation of oxygen supply or vice versa. Consequently, the heart exhibits dynamic change in its pumping rate and force of contraction. If the control system fails, the heart exhibits unhealthy state. However, assessment of healthy/unhealthy status is uneasy because we are not able to monitor the nerve activities by non-invasive methods. Therefore, we challenged to detect state of the heart without nerve-recordings. We used the detrended fluctuation analysis (DFA) applying to heartbeat interval time series because DFA has been believed that it can quantify the state of heart. We performed DFA on the EKGs (electrocardiograms) from various living organisms including humans. The objective of this research was to determine whether the analytical technology, DFA, could function as a useful method for the evaluation of the subject’s quality of cardiovascular-related illness and transition to and from a normal healthy state. We found that DFA could describe brain-heart interaction quantitatively: the scaling exponents of (1) healthy, (2) sick-type (such as stressful or arrhythmic states), and (3) unpredictable-death type (such as ischemic heart disease) were corresponded to individuals who exhibited, (1) nearly one, (2) less than one, and (3) greater than one, respectively. We conclude that scaling exponents could determine whether the subjects are under sick or healthy conditions on the basis of cardiac physiology.
Effects of Residual Stresses and the Post Weld Heat Treatments of TIG Welded Aluminum Alloy AA6061-T651
Authors: Dewan Mohammad W. , Liang Jiandong , Wahab M. A. , Okeil Ayman M.
Published: October 2013

Heat treatable AA-6061 T651 Aluminum alloys (Al-Mg-Si) have found considerable importance in various structural applications for their high strength to weight ratio and corrosion resistance properties. Weld defects, residual stresses, and microstructural changes are the key factors for the performance reduction as well as failure of welded structures. Tungsten inert gas (TIG/GTAW) welding was carried out on AA-6061 T651 Aluminum Alloy plates using Argon/Helium (50/50) as the shielding gas. Non-destructive phased array ultrasonic testing (PAUT) was applied for the detection and characterization of weld defects and characterization of the mechanical performances. In this study, ultrasonic technique was also used for the evaluation of post-weld residual stresses in welded components. The approach is based on the acoustoelastic effect, in which ultrasonic wave propagation speed is related to the magnitude of stresses present in the materials. To verify the estimated residual stresses by ultrasonic testing, hole-drilling technique was carried out and observed analogous results. The effects of post weld heat treatment (PWHT) on the residual stresses, grain size, micro hardness, and tensile properties were also studied. The grain size and micro hardness were studied through Heyn’s method and Vickers hardness test, respectively. Lower residual stresses were observed in post-weld heat-treated specimens, which also experienced from microstructure and micro hardness studies. The PWHT also resulted enhanced tensile properties for the redistribution of microstructures and residual stresses.
On Fatigue Strength Reduction Factor: State of the Art
Authors: Owolabi Gbadebo , Egboiyi Benedict , Whitworth Horace , Aluko Olanrewaju
Published: October 2013

Numerous theoretical models have been developed to predict the fatigue strength reduction factor (also known as fatigue notch factor), an important parameter in fatigue life prediction of notched components. These models include: the classical average stress method, the fracture mechanics method, the stress field intensity method, the strain energy method, and the weakest link method. However, most of these methods do not incorporate explicit sensitivity to materials microstructure. Accordingly, notch sensitivity remains a highly empirical subject in spite of significant advances in microstructure-sensitive modeling. This paper gives a detailed literature review of these methods and addresses their limitations. It also discusses a recently developed probabilistic method for microstructure-sensitive fatigue notch factor. The probabilistic method provides a very strong physical basis for fatigue strength reduction and associated notch sensitivity; thus it can be used to determine the effect of notches on reduction of fatigue resistance in a way that directly incorporates microstructure. The results obtained using the new probabilistic framework and other conventional methods are compared with experimental data for notched components. The probabilistic framework gives better correlation with experimental results for the notch sensitivity and notch size effect than the conventional approaches including the Neuber’s, the Peterson, and the fracture mechanics methods.
Modeling of Vehicle Magnetic Footprint in 3-D Space for Type Detection
Authors: Roussel Stephane , Porumamilla Hemanth , Birdsong Charles , Schuster Peter
Published: October 2013

This paper presents a modified multiple 3-D dipole model to capture the complex magnetic footprints created by different vehicles on the road. In this study, laboratory bench tests were carried out to record the magnetic behavior of single dipole magnets and road tests were then conducted to record the complex magnetic behavior of vehicles. A preliminary 2-D modified dipole model similar to literature was developed and then expanded to a high fidelity 3-D multiple dipole model. An exhaustive parametric study was conducted to identify relevant design parameters for model matching. The 2-D model helped corroborate the results of laboratory bench tests using magnets and showed that the magnetic sensor was capable of identifying different sized magnets based on their magnetic footprints. Similar conclusions were made when applying the 3-D multiple dipole model to the experimental road tests. Different analytical functions were developed to help distinguish vehicle types based on their magnetic footprint. The analytical and experimental study conducted showed that vehicle magnetic footprint could be captured by mathematical models and that the magnetic sensor could be used to identify vehicle types.
Experimental Study on Dynamic Behavior of a Rolling Agricultural Tire
Authors: Fujita Katsuhide , Saito Takashi , Yamazaki Toru
Published: October 2013

When agricultural machines are operated on pavements, the vibration and noise caused by the interaction between the tire lugs and the road surface are inevitable. In conventional studies, it is considered that the dynamic behavior of a rolling agricultural tire is influenced by the vibration characteristics of the tire. Resonance occurs when the lug excitation frequency of the tire, which is defined as the lug number multiplied by the number of revolutions of the tire, becomes equal to the natural frequency of the tire. In other words, the rolling tire shows large vibrations in the direction of the natural mode corresponding to the natural frequency of the tire. However, the vibration mode of the rolling tire in resonance state has not yet been clarified. In this study, it is confirmed that the dynamic behavior of the rolling tire can be evaluated by performing sound pressure measurements using closely located microphones to the tire. Further, the vibration mode in the resonance state is identified by performing simultaneous measurements of the sound pressure, and the vibration mode corresponds to the natural mode of the tire is confirmed as well.
Numerical Analysis of Flow and Thermal Performance of a Water-Cooled Wavy Microchannel Heat Sink
Authors: Xie Gongnan , Liu Jian , Zhang Weihong , Sundén Bengt
Published: October 2013

With the increasing output power of the integrated circuit chips, the heat flux involved is being accordingly increased. In such situation, the air has almost reached its limit of cooling capacity, and thus the liquid cooling technology incorporating microchannel heat sinks is desired to cool the electronic chips in order to remove more heat loads. However these microchannel heat sinks are often designed to be straight with rectangular cross section. In this study, on the basis of a straight microchannel having rectangular cross section, a kind of wavy microchannel is designed and then the laminar flow and heat transfer are investigated numerically. It is shown that for removing the identical load, the wavy microchannel has great potential to reduce pressure drop compared to the straight microchannel, especially for higher wave amplitude at the same Reynolds number, indicating the overall thermal performance of the wavy microchannel is superior to the traditional straight rectangular microchannel. It is suggested such wavy microchannel can be used to cool chips effectively with much smaller pressure drop penalty.
The Effect of Damage on the Bonding Strength of Hybrid T-Joint Structures
Authors: Yeh P. C. , Chang P. Y. , Yang J. M. , Kordonowy D.
Published: October 2013

Adhesively co-bonded and co-cured structural joints are attractive for aircraft applications due to the potential reduction in weight and part count as compared to traditional mechanical joints. In this research, a damage tolerant structure using co-bonded hybrid T-joints was designed and manufactured for structural application on a remotely piloted aircraft. The T-joint structure was constructed from GLAss fiber REinforced aluminum laminates (GLARE) 4-2/1 skin, carbon fiber composite web, and three-dimensional woven glass fiber fabric Pi-preform in a co-bonded/co-cured process. The goal of this research is to demonstrate the damage tolerance, structural capability, and ancillary benefits of the co-bonded T-joint.

In order to evaluate the structural design and investigate the strength of manufactured T-joint, experiments such as pull-out tests were performed. Additionally, the T-joint was manufactured and tested with defects inserted intentionally within the co-bonded interface between the GLARE and Pi-preform at two locations: a) underneath the vertical woven carbon composite web, and b) along the edge of the glass fiber Pi-preform and the GLARE flange. Pull-out tests showed the effect of intentionally inserted defects on the strength of the co-bonded T-joint structure. The benefit of co-bonded joints featuring damage tolerant skins and high strength composite webs has been demonstrated.
Effects of Various Types of Binary Cycles on Thermal and Exergy Efficiency of Combined Flash-Binary Power Plants
Authors: Vatani Mahshid , Ziabasharhagh Masoud , Amiri Shayan
Published: October 2013

With the progress of technologies, engineers try to evaluate new and applicable ways to get high possible amount of energy from renewable resources, especially in geothermal power plants. One of the newest techniques is combining different types of geothermal cycles to decrease wastage of the energy. In the present article, thermodynamic optimization of different flash-binary geothermal power plants is studied to get maximum efficiency. The cycles studied in this paper are single and double flash-binary geothermal power plants of basic Organic Rankine Cycle (ORC), regenerative ORC and ORC with an Internal Heat Exchanger (IHE). The main gain due to using various types of ORC cycles is to determine the best and efficient type of the Rankine cycle for combined flash-binary geothermal power plants. Furthermore, in binary cycles choosing the best and practical working fluid is an important factor. Hence three different types of working fluids have been used to find the best one that gives maximum thermal and exergy efficiency of combined flash-binary geothermal power plants. According to results, the maximum thermal and exergy efficiencies both achieved in ORC with an IHE and the effective working fluid is R123.
Design and Optimization of a Cylindrical Voice Coil Actuator for the Synchronized Segmentally Interchanging Pulley Transmission System (SSIPTS)
Authors: Mashatan Vahid , Zu Jean W.
Published: October 2013

This paper presents design, modeling, and optimization methodologies for an electromagnetic actuator for the synchronized segmentally interchanging pulley transmission system (SSIPTS). The overall design of SSIPTS and its principle of operation introduce very challenging and conflicting design requirements. The actuators must be very small in size and as light as possible while they need to produce very high force linearly along the stroke. Since no commercial actuator is able to meet all the design requirements of SSIPTS, a novel actuator must be designed for this application. Based on the prior state of the art and literature surveys on actuator technologies and the performance requirements, it has been concluded that voice coil actuator (VCA) technology is the best candidate. VCA is modeled for this application, and the key design parameters have been defined. Further, geometry mapping optimization and FEM analysis have been conducted to determine the optimized values for the key design parameters. Based on the simulation results and FEM analysis, the optimized VCA is shaped. This design of VCA meets the design requirements of SSIPTS.
Reliability Analysis of Reinforced Concrete (RC) Plates and Shells
Authors: Sitaram Pattabhi , Kaul Sudhir
Published: October 2013

The application of the principles of probabilistic techniques to structural design has been gaining widespread acceptance over the last two decades. However, the design of many engineering structures is still based on standard deterministic design codes that may not account for inherent design and material variability. Although design codes have been successfully used for many decades, the use of probabilistic design allows a designer to get a more holistic understanding of design variables and a clear assessment of uncertainties. This paper evaluates the reliability of plates and shells made from reinforced concrete (RC) that are commonly used in engineering structures. A modified Monte Carlo approach is used to capture variability in design parameters such as the spacing of the reinforcement, the diameter of the reinforcement and material thickness of the concrete as well as material properties of concrete. The ultimate load carrying capacity is used as the primary failure mode for reliability analysis and the onset of cracking and deflection are also monitored for all the runs that are made for computing reliability. A nonlinear finite element program is used for analysis and the results from the finite element program are used for computing reliability. A sensitivity analysis is performed to determine the most significant parameters influencing the reliability of plates and shells used in this study.
Influence of Viscosity on Forcespinning™ Dynamics
Authors: Padron Simon , Caruntu Dumitru I. , Lozano Karen
Published: October 2013

Forcespinning™ is a novel method that makes use of centrifugal forces to produce nanofibers rapidly and at high yields. A 2D computational Forcespinning™ viscous fluid dynamics model is developed, that improves on previous models. The fluid dynamics equations are solved using themethod of multiple scales along with the finite difference method, and including slender-jet theory assumptions. The effects that the Reynolds (Re) number has on the resulting fiber trajectory, radius, and tangential velocity are presented.
Analysis of the Bistable Piezoelectric Inertial Generator by the Harmonic Balance Method
Authors: Owens Benjamin A. M. , Stanton Samuel C. , Mann Brian P.
Published: October 2013

This paper analytically predicts the existence, stability, and changes due to parameter variations on the different oscillations of a bistable piezoelectric generator. Existing work on this type of system has assumed linear piezoelectric behavior and linear damping and has been confined to numerical studies and experimental explorations. This paper improves upon the previous work by incorporating nonlinear dissipation and cubic softening influences in the electroelastic laminates prior to analytical analysis. This analysis provides a framework for theoretical prediction of a variety of empirical observations including potential well escape and optimum impedance loading.
Reduced Order Model of Two Coupled MEMS Parallel Cantilever Resonators Under DC and AC Voltage Near Natural Frequency
Authors: Caruntu Dumitru I. , Taylor Kyle N.
Published: October 2013

This paper deals with a system of two coupled parallel identical MEMS cantilever resonators and a ground plate. Alternating Current (AC) and Direct Current (DC) voltages are applied between the first resonator and ground plate, and a DC voltage applied between the resonators. The AC voltage frequency is near natural frequency of the resonators. The electrostatic forces produced by voltages are nonlinear. System equations of motion are obtained using Lagrange equations, then nondimensionalized. The Method of Multiple Scales (MMS) is used to find the steady state frequency response. The Reduced Order Model (ROM) is used to validate MMS results. Matlab is used to find cantilever frequency response of the resonator tip. The DC voltage between resonators is showed to significantly influence the response of the first resonator.
Structural Damage Detection Based on Autoregressive Spectra Analysis of Time Series
Authors: Hu Ming-Hui , Cong Er-Ding , Tu Shan-Tung , Xuan Fu-Zhen , Zhou Shao-Ping , Xia Chun-Ming
Published: October 2013

In this paper, an autoregressive spectral analysis method is proposed for on-line structural damage detection. Firstly, the monitoring strain data are modeled as ARMA models. The power spectral density (PSD) value is directly determining by center-autocorrelation function and statistical autocorrelation function. Structural damage detection is conducted by comparing the values of PSD of the inspected structure. Two experimental applications to the detection of damage in industrial piping structure demonstrate the potential and effectiveness of the new damage detection technique.
Develop a Nonlinear Oscillating System to Harvest Vibration Energy
Authors: Xie Longhan , Yao Yupei , Du Ruxu
Published: October 2013

This work gives the design and analysis of a novel energy harvesting system that uses elastic strings to produce nonlinear oscillation with tunable resonance. The governing equation of the harvesting system is derived to show that the system has the property of the Duffing’s oscillator. Then the theoretical analysis is made to investigate the energy harvesting potential under external harmonic excitation. Power output is also estimated. The motivation of this work is that the nonlinear performance can be exploited to improve the effectiveness of the energy harvesting from environment vibration.
A Novel Integrated Sensing System (ISS) for Monitoring Motion Errors of a Precision Linear Slide
Authors: Fung Eric H. K. , Hou N. J. , Zhu M. , Wong W. O.
Published: October 2013

In order to improve the accuracy and reliability of scanning coordinate measure machines (CMM), the dynamic errors of the CMM axes have to be continuously monitored and compensated in the measurement process. This paper proposes a novel method and develops an Integrated Sensing System (ISS) to on-machine determine the three error components of a precision linear slide [1]: the straightness motion, the yaw and the roll under the effect of thermal distortion caused by friction and drive. The ISS is proposed for an illustrative model of a linear slide. It consist of eight distance sensors installed in a stationary stage, and five temperature sensors mounted at various parts of the working machine. The stationary stage is mounted opposite to the profile of the moving slide axis. The error separation algorithm of this novel method is based on Fourier series techniques. A pre-built thermal error model [2] based on thermal modal analysis [3] is used to obtain the deformations of different machine components. Then thermal looping [3] technique is used to estimate thermally-induced profile variations of the slide. The Fourier series technique is then applied to the pre-processed outputs of the distance sensors to obtain the profiles and the motion errors. Computer simulation confirmed the effectiveness of the ISS by comparing the calculated results with the pre-define inputs under thermal compensation [2] and no thermal compensation situations.
Finite Element Modeling and Analysis of Low Velocity Impact on Composite Structures Subject to Progressive Damage and Delamination
Authors: Ibrahim Ahmed H. , Yigit Ahmet S.
Published: October 2013

There has been growing interest to use composites in load carrying structures where high strength and light weight are of major concern, e.g., sports, automobiles and aircraft industries. Despite extensive research in the last two decades, mechanical behavior of composite structures subject to contact and impact loading is still not well understood. It is well known that composites are highly vulnerable to various modes of failure and damage due to impact/contact by foreign objects. Such impact/contact events are not only dependent on the material behavior but also on the dynamics of the structure. Although some of the currently available Finite Element (FE) packages are capable of simulating mechanical behavior of composite structures subject to impact, it requires extensive training and in-depth knowledge to obtain an adequate model with acceptable efficiency. Several nonlinear FE models have the ability to capture composite damage due to impact/contact including internal delamination or fiber/matrix failure. On the other hand, very few FE models are able to capture composite damage progression or material degradation. This work investigates different modeling techniques by analyzing their prediction of force-time history and force-indentation curve occurring in composite plates as a result of low velocity impact. The objective is to compare different techniques, both in model creation and impact response prediction, and to provide guidelines on selecting the most appropriate technique for a given impact situation.
Effect of the Stretch Rate During Uniaxial Testing on the Mechanical Properties of Prolene®
Authors: Bazi T. M. , Ammouri A. H. , Hamade R. F.
Published: October 2013

We assess the effects of stretch rate on the mechanical properties of Prolene® (Ethicon, Gynecare, Somerville, NJ, USA), a knitted polypropylene mesh. Prolene®, consisting of macroporous knitted polypropylene, is considered here as a suitable proxy to midurethral tape (MUT) as well as to many other prosthesis products used in surgery applications. Such products are utilized to treat urine incontinence, pelvic organ prolapse, as well as hernia in humans.

Of the mechanical properties of special significance are the following three properties: peak load (N), extension (%) at peak load, and linear stiffness (N/mm). Uniaxial tensile testing was performed on mesh samples on a universal testing machine and involved loading different samples at 5 cross-head speeds of: 1, 10, 50, 100, and 500 mm/min. The corresponding properties were measured under these 5 conditions. In order to minimize damage to the specimens at the jaws, special dual action pneumatically operated grips with rubber faced jaws were used to hold the samples in place. The effectiveness of these grips was illustrated by the fact that none of the failed samples broke at grips. Statistically significant findings suggest an increasing trend for Prolene® stiffness vs. stretch rate (R2 = 0.9679; two-tailed p value = 0.0025) where the stiffness increases 26.2% when increasing the displacement rate from 1 to 500 mm/min. For extension (%) at peak load, a decreasing trend was found vs. stretch rate (R2 = 0.81; two-tailed p value = 0.037) where increasing the displacement rate from 1 mm/min to 500 mm/min corresponds to a 22% decrease in the relative elongation of the mesh. No statistically significant dependence of peak load on stretch rate was found. These findings may help workers in the biomedical field develop suitable uniaxial tensile testing protocols of such materials.
Using Random Forests to Identify Factors of Student Motivation in a Project-Based Learning Course
Authors: Cooper Lauren , Kotys-Schwartz Daria , Reamon Derek
Published: October 2013

Grounded in motivation theory, the purpose of this research is to use random forest analysis to identify factors of motivation of students who participate in a project-based learning experience. Our research aims to answer: 1) How does project-based service learning affect students’ motivation as compared to conventional (non-service) project-based learning? 2) How are women affected differentially by project-based service-learning? The research, which began in 2011, was completed over a two-year period. The students and activities in Component Design, an existing junior-level course at the University of Colorado at Boulder served as the research focus. Specifically, project-based service-learning curriculum was implemented into a required design and build activity for Component Design students. Using a conventional design project as the control, how the context of project-based service learning affects aspects of student motivation was studied.

This paper discusses the research design, theoretical framework, data analysis methods, and random forest results. Our findings indicate that students’ initial non-technical skills were the most important predictor of motivation in the conventional project-based learning experience and that students’ perceived value of the course and the project were the most important predictors of motivation in the project-based service-learning experience.
Multiphase Flow Mal-Distribution in Pipe Manifolds
Authors: Kharoua N. , Khezzar L.
Published: October 2013

A computational fluid dynamics (CFD) study was conducted on the mal-distribution problem occurring within pairs of spheroids used in the oil industry as three-phase gravity separators. The simulations were performed using the Euler-Euler multiphase model combined with the k-ε turbulence model. Several oil production scenarios under different input conditions of flow rates and temperatures were investigated. Flow regime maps were used to determine the likely multiphase flow nature upstream of the T-junctions employed within the spheroids pipe network as splitters. The simulation results confirmed the mal-distribution phenomenon and showed interesting details of the multiphase flow behavior inside the piping network considered. A mal-distribution between the risers of each spheroid was, also, noticed. The relatively large number of T-junctions used as well as the structure of the downstream piping network employed led to complex multiphase flow behavior. Increased concentration of liquid phase reminiscent of accumulation was noticed in some parts of the piping network acting as an obstacle for the gas stream. The mal-distribution generated was in the range 12–20%. The symmetry of the piping networks and the arrangement of the T-junctions was found to be a key parameter among the causes of the mal-distribution.
Finite Element Modeling of Discharge Zone in Micro-EDM Process
Authors: Mathew Jose , Dilip Deepak G. , Joseph Mathew J. , Kuriachen Basil
Published: October 2013

Micro-EDM (μ-EDM) is a derived form of EDM process especially evolved to perform micro-machining. The μ-EDM process is based on the thermoelectric energy created between a work piece and an electrode submerged in a dielectric fluid. When the work piece and the electrode are separated by a specific small gap, a pulsed discharge occurs which removes material from the work piece through melting and evaporation. A thermo-electrical approach to model the temperature variation in the discharge gap using finite element method has been done so as to predict the temperature distribution in the discharge channel and find out the maximum temperatures acting on the work piece as well as the tool electrode and the subsequent material removal rate on the work piece. The temperature generated on the surface of the work piece depends upon the various properties of the conductor; as a result it varies depending on the conductor. An axi-symmetric two-dimensional model was used for modeling the region between the two electrodes. Tungsten and titanium alloy were the materials used for cathode and anode, respectively. A 60μm by 60μm region was taken for modeling the process. An uniform mesh of equal dimensions was made to carry out the modeling. The finite element results were compared with the results obtained by conducting experiments on titanium alloy using single spark generator device under the same discharge conditions that were given as input for the mathematical model. The MRR obtained agrees very well with the predicted MRR thus validating the model.
Optimization of Thermal Power Plants Operation in the German De-Regulated Electricity Market Using Dynamic Programming
Authors: Scarabello G. , Rech S. , Lazzaretto A. , Christidis A. , Tsatsaronis G.
Published: October 2013

The prospect of clean electrical energy generation has recently driven to massive investments on renewable energies, which in turn has affected operation and profits of existing traditional thermal power plants.

In this work several coal-fired and combined cycle power units are simulated under design and off-design conditions to adequately represent the behavior of all modern thermal units included in the German power system. A dynamic optimization problem is then solved to estimate the short-run profits obtained by these units using the spot prices of the German electricity market (EEX) in years 2007–2010. The optimization model is developed using a Mixed Integer Linear Programming approach to take the on-off status into account and reduce computational effort. New market scenarios with increasing renewable shares (and consequently different spot prices) are finally simulated to analyze the consequences of a larger capacity of renewable energies on the optimal operation of traditional thermal power plants.
Non-Newtonian Fluids Mixing Behavior Behind a Grid
Authors: Nguyen T. D. , Elhajem M. , Nguyen Q. , Simoëns S. , Delache A. , Balint J. L.
Published: October 2013

Numerous biological, biomedical or chemical engineering processes involve non-Newtonian fluids as shear-thinning or shear-thickening fluids. As early as 1969, Lumley [1] investigated the influence of the non-Newtonian characteristics on the Kolmogorov cascade. In 1986, De Gennes [2] revisited such point of view by considering more precisely elasticity and shear thinning properties. As of today, the correlation between elasticity and other flow properties is still unclear, recent numerical simulations attempted to clarify the issue with the use of FENE-P or other linear viscoelastic models. The goal of this experimental work is to further clarify these assumptions by using new optical tools (PIV, PLIF) to study non-Newtonian decaying isotropic homogeneous turbulence (IHT), using the approach and analysis of the 1971 work of Comte-Bellot and Corrsin [3] for Newtonian fluids, and more recently (2010, 2011) by Lenoir et al. [4]. The experimental set-up consists of a small, 1m long liquid channel, with a cross-section of 6.6 × 6.6 cm2, as in Simoëns and Ayrault [5]. In order to obtain best possible quasi-isotropic flow for sufficient large Reynolds numbers (see Comte-Bellot and Corrsin [6]), the grid was installed transversally upstream the flow, at the outlet of a contraction chamber; the grid squared mesh was 8mm wide. A PIV Lavision System with two synchronized pulsed YAG Lasers was used to obtain Instantaneous velocity maps on selected vertical plane crossing longitudinally the channel at its center. The flow was seeded with 10μm diameter fluorescent particles for PIV measurements. IHT experiments were done on a 1% carboxymethyl cellulose (CMC) aqueous solution (such dilute CMC solution is non-Newtonian as shown in the 2008 work of Benchabane and Bekkour [7]) and then compared to measurements in water at the same flow rate. To prevent molecular modification of the CMC fluid structure out of its natural shear stress, the flow was driven by gravity, not by a pump. For this study, the water flow Reynolds number was 1600; the flow regime was too low to reach a turbulent state. Frequent rheometer checks were performed during the CMC experiments to verify the preservation of the integral shear thinning properties of the fluids. For the CMC flow, the Reynolds number was determined locally, based on the local viscosity after a Carreau-Yasuda model of order 2, in which γ̇ is the rate of shear strain, η is the viscosity at iteration n, η0 is the viscosity at zero shear rate; λ is a constant with units of time, where 1/λ is the critical shear rate at which viscosity begins to decrease (see Nguyen et al. (2010, 2012) [8], [9]).
Thermodynamic Effects in Porous Media Saturated With Fluids: Application to Wellbore Thermometry
Authors: Valiullin Rim , Sharafutdinov Ramil , Ramazanov Ajrat , Akhatov Iskander
Published: October 2013

Recent years have seen an active research of thermal methods of monitoring the development of oil and gas fields. Among other reasons temperature changes in the oil reservoir are brought about by the manifestations of the adiabatic and Joule-Thomson effects. It may also alter due to degassing heat in case when pressure in the wellbore drops below the oil saturation pressure of the gas. The paper presents some results of experimental and theoretical study of the impact of the adiabatic and Joule-Thomson effects as well as the fluid degassing heat on the temperature field in the oil-gas reservoir. To calculate the formation temperature field in details one has to determine the thermodynamic coefficients for real formation fluids. For this end, the experimental set-up is built comprising a PVT cell to determine the Joule-Thomson and adiabatic coefficients as well as the heat of oil degassing. The experimentally obtained thermodynamic coefficients are used to calculate the evolution of temperature field in the porous medium and wellbore for various pressure gradients and gas contents. The results serve as a scientific background for development of thermal monitoring methods in oil and gas reservoirs. An example of practical application of thermal monitoring methods in oil industry is also presented.
The Improved Hybrid Discretization Model for the Discrete Topology Optimization of Compliant Mechanisms
Authors: Zhou Hong , Ahmed Nisar , Uttha Avinash
Published: October 2013

In the discrete topology optimization, material state is either solid or void and there is no topology uncertainty problem caused by any intermediate material state. In this paper, the improved hybrid discretization model is introduced for the discrete topology optimization of compliant mechanisms. The design domain is discretized into quadrilateral design cells and each quadrilateral design cell is further subdivided into triangular analysis cells. The dangling and redundant solid design cells are removed from topology solutions in the improved hybrid discretization model to promote the material utilization. To make the designed compliant mechanisms safe, the local stress constraint is directly imposed on each triangular analysis cell. To circumvent the geometrical bias against the vertical design cells, the binary bit-array genetic algorithm is used to search for the optimal topology. Two topology optimization examples of compliant mechanisms are solved based on the proposed improved hybrid discretization model to verify its effectiveness.
Optimized Cage Design for Increasing the Life of Solid Lubricated Roller Bearings
Authors: Marquart Matthias , Sauer Bernd
Published: October 2013

Roller bearings rank among the most used machine elements. Depending on the applications a lifetime of thousands of hours (e.g. machine tools: 15000h) can be realized as long as standard lubrications can be used. Nevertheless some applications only provide special environments, like high temperatures or vacuum, where oil or grease cannot be used. In these areas solid lubrication might be a choice. However solid lubricated roller bearing cannot offer similar lifetimes nor is a universally valid lifetime prediction available for such systems. Currently the friction work of a tribologically stressed surface offers a possibility for estimating the life. For doing so the paper gives an introduction. Further a test rig designed to examine roller bearings under high temperatures up to 300°C and high vacuum will be presented. In various experiments the influence of roller bearing cage design on its possible lifetime could be proven, especially if the cage has been used as a lubricant depot. On this basis a multibody simulation (mbs) model was built to get an understanding of the inner dynamics of roller bearings and its parts, e.g. rolling bodies and cage. While the geometry was built in commercial software the calculation of contacts, e.g. rolling body to raceway, and loads as well as friction is done in user written subroutines developed at the Institute of Machine Elements, Gears, and Transmissions at the University of Kaiserslautern. This model allows for an investigation of the effects resulting due to a parameter study of the geometry of the different parts a common roller bearing consists of: inner race, outer race, rolling bodies and cage. By using this tool the weak points in cage design could be determined as well as options for increasing the functionality of a cage as lubricant depot were shown. Combining experimental with simulated results, a new cage design for solid lubricated roller bearings could be developed. This new cage design increases the lifetime of the used test bearings from 2.5 million revolutions to more than 40 million revolutions. A further benefit of the new cage design is the ability to run at much higher rotational speeds than bearing systems that are available on the market nowadays.
FMM/GPU Accelerated Molecular Dynamics Simulation of Phase Transitions in Water-Nitrogen-Metal Systems
Authors: Moiseeva Elena , Mikhaylenko Constantin , Malyshev Victor , Maryin Dmitry , Gumerov Nail
Published: October 2013

To characterize the behavior of water with dissolved gas (nitrogen) near a solid metallic substrate, which is important for realistic modeling of flows in nanochannels, the method of molecular dynamics is used. High performance computing is achieved via the Fast Multipole Method (FMM) for the force evaluation and via utilization of heterogeneous architectures which consists of central processing units (CPUs) and graphics processing units (GPUs). The FMM allows one to speed up computations of the long-range interactions (Coulomb potential) due to the linear scaling of the algorithm with the problem size. Utilization of the GPU provides significant acceleration of computations. Realization of the FMM on GPUs allows one to perform computational experiments for very large systems. The paper shows that the described technique can be used for water dynamics simulations in a region of size up to 100 nanometers, or of the order 100 millions molecules on personal supercomputers equipped with several GPUs. Results of numerical experiments on structure formation on the contact interface of a water droplet and metal surface both for pure water and for water with dissolved air are reported.
Negative Index Phononic Crystals Made of Metal Based Microstructure
Authors: Hladky-Hennion Anne-Christine , Croënne Charles , Vasseur Jérôme , Dubus Bertrand , Norris Andrew
Published: October 2013

A Phononic Crystal (PC) based on a metal microstructure, is studied. At low frequency, it presents water like density and water like longitudinal velocity, and very small shear rigidity. At higher frequency, the band structure of the PC exhibits an isolated branch with a negative slope and a quasi-longitudinal behaviour that intercepts the water sound line. At the intersection point frequency, matching of the phase velocities in the PC and in the external medium is realized. Therefore, the structure is a potential candidate for the negative refraction of longitudinal waves when the structure is coupled to the external water medium. The paper presents the main numerical results. Experiments are under progress.