bluuebunny/crossref_metadata_2025 huggingface dataset:
Automotive Lifts: Unrestrained vs. Restrained Swing Arms
Authors: Barnett Ralph L. , Glauber John B.
Published: July 2010

To perform automotive maintenance, there are many makeshift ways of lifting and holding a vehicle including the use of forklifts, overhead hoists and cranes, jacks of every kind, jack stands and various ramp systems. When automobiles fall from these devices, the causes are usually obvious and we disapprovingly tolerate the risk taking. On the other hand, when a vehicle falls from a dedicated automotive lift, the accident is entirely unacceptable. This paper examines several hidden dangers associated with a particular class of lifts that are “frame engaging.” Various styles of these lifts use four cantilevered arms to elevate and support vehicles on adapter pads positioned on the arms’ free ends. If the vehicle slides off of one or more pads, it usually falls catastrophically. The cantilevered arms, when raised, are supposed to be restrained against rotation in a horizontal plane. When restrained, the arms provide a robust structural system for resisting horizontal workplace forces that tend to slide vehicles off the pads. The arms maintain the horizontal locations of the adapters by developing bending and axial planar resistance. If, on the other hand, the arms are free to pivot due to sloth or poor design, their structural behavior is dramatically transformed. The planar bending resistance of the arms completely disappears and they become direct stress diagonal truss members; the vehicle itself unwittingly becomes the truss’ tension chord. The appearance of the fixed and pivoting systems is the same; however, the truss action magnifies the horizontal forces acting on the adapter pads increasing the slip probability. Indeed, depending on the orientation of the pivoting swing arms, any finite horizontal force applied to a vehicle may lead to an unbounded tangential “slide-out” force. This is, of course, a theoretical possibility, not a practical reality.
Non-Destructive Evaluation of Creep Damage in a Nickel Base Super-Alloy Turbine Bucket
Authors: Carreon Hector
Published: July 2010

Due to elevated temperatures, excessive stresses and severed corrosion conditions, turbine engine components are subject to creep processes that limit the components life such as a turbine bucket. The failure mechanism of a turbine bucket is related primarily to creep and corrosion and secondarily to thermal fatigue. As a result, it is desirable to assess the current condition of such turbine component. This study uses the eddy current (EC) nondestructive evaluation technique in an effort to monitor the creep damage in a nickel base super-alloy, 7FA stage 2 turbine bucket after service. The experimental results show significative electrical conductivity variations in eddy current images on the creep damage zone of nickel base super-alloy samples cut from a turbine bucket. Thermoelectric power (TEP) measurements were also conducted in order to obtain a direct correlation between the presence of material changes due to creep damage and the electrical conductivity measurements.
Safety Analysis and Child Testing of Residential Windows
Authors: Brickman Dennis B. , Grzetic Joseph F.
Published: July 2010

A three year old boy fell through a third floor apartment window resulting in fatality. An accident reconstruction was performed using live surrogate children under static and dynamic loading conditions. The failure modes and physical characteristics of tested window screens are presented. Accident prevention strategies are explored.
Vehicle Rollover Detection Index
Authors: Moshchuk Nikolai , Chen Shih-Ken
Published: July 2010

Vehicle rollover resistance can be enhanced using differential braking control, rear-wheel steering, front steering control, suspension damping control, or the combination of any of them. In each control action, the controller receives the vehicle dynamics information from various sensors, such as a yaw-velocity sensor, a lateral accelerometer, a roll-velocity sensor (if available), and suspension displacement sensors (if available), and determines a control action to be taken. A balance between controlling vehicle roll motion and vehicle yaw motion needs to be reached to achieve the optimal vehicle response. Therefore, detection of the current and impending vehicle situations, especially pertaining to the vehicle roll, is vital for the quality of control. Various methodologies have been developed in the past to detect vehicle situations that may lead to rollover. Generally, rollover detection is based on roll velocity sensor and roll angle estimation. In most of these methods, thresholds for roll velocity and roll angle are established to detect imminent rollover. Even though roll velocity and roll angle are the two most important elements in vehicle roll motion, they may not be sufficient to timely detect impending rollover. This paper proposes a vehicle rollover detection index that can be used in a control algorithm to enhance vehicle rollover resistance. It uses roll angle and velocity (measured or estimated), yaw velocity, vehicle speed, and lateral acceleration. Further enhancement to the proposed algorithm is then briefly discussed that includes the effect of vehicle lateral load transfer on the detection.
Novel Design of Polysilicon Microphone With Corrugated Diaphragm
Authors: Zhang Dan , Shi Qi , Tao Ye
Published: July 2010

This paper presents a novel design of poly-silicon corrugated diaphragm which can be used for micro-machined microphone. The microphone is built on a corrugated poly-silicon diaphragm with eight-leg supports. In order to reduce the residual stress, the diaphragm is designed with a corrugated ring. A theoretical calculation is presented to show the result of the new design; the FEM simulation results have shown that the eight-leg support diaphragm is the best compared to other two types. The eight-leg-support diaphragm has more deformation than the all-edge-support diaphragm. The fabrication process is also presented in order to confirm that the new design is possibly built by the new technology.
ANN for Tribological Applications
Authors: Tanzim Nasir , Nbhan Salih , Liew Tze Hui , Chin Chee Wen , Yousif B. F.
Published: July 2010

The current work is an attempt to investigate the possibility of using artificial neural network (ANN) modelling as a tool for friction coefficient prediction. The ANN model was trained at various configurations with different functions of training to develop the optimal ANN model. The experimental data was obtained from previous works. The results revealed that single layered model has reasonable accuracy in prediction when trained with TrainLM function. The results were acceptable especially in predicting steady-state friction coefficient, which proved ANN technology’s ability to predict the friction co-efficient.
On the Construction and Use of Surrogate Models for the Dynamic Analysis of Multibody Systems
Authors: Ardeh H. Ansari , Tupy M. , Negrut D.
Published: July 2010

This study outlines an approach for speeding up the simulation of the dynamic response of vehicle models that include hysteretic nonlinear tire components. The method proposed replaces the hysteretic nonlinear tire model with a surrogate model that emulates the dynamic response of the actual tire. The approach is demonstrated via a dynamic simulation of a quarter vehicle model. In the proposed methodology, training information generated with a reduced number of harmonic excitations is used to construct the tire hysteretic force emulator using a Neural Network (NN) element. The proposed approach has two stages: a learning stage, followed by an embedding of the learned model into the quarter car model. The learning related main challenge stems from the attempt to capture with the NN element the behavior of a hysteretic element whose response depends on its loading history. The methodology is demonstrated in conjunction with a simple nonlinear quarter vehicle system as well as an ADAMS based model that uses a complex tire element. The results obtained with the surrogate model prove to be accurate and are obtained at a fraction of the CPU time required to handle the original models. The approach proposed is anticipated to be useful for reducing the duration of vehicle simulations, or when a tire model is not available but experimental data can be used to generate a surrogate model.
About Terahertz Generation on the Superstructures Layers AIIIBIIICVI2 Crystals
Authors: Sardarly R. M. , Samedov O. A. , Bayramov A. A. , Abdullayev A. P. , Salmanov F. T.
Published: July 2010

In layered crystals of the AIIIBIIICVI2 family the presence of wide temperature ranges is indicated, in which on the primitive translation of the lattice of the initial phase superlattices with periods of 5–15 nm are superimposed. At that, the neutron-diffraction patterns show the presence of superstructural reflections: both reflections that are multiple of the initial translation of the lattice and incommensurable superstructural ones. Our research showed that layered crystals of the TlInS2 family are crystallized with the formation of both incommensurable and commensurate (of the initial translation) superlattices and could be used for the generation of Terahertz radiation.
Nanoengineering Polyaniline for Advanced Chemosensing Applications
Authors: Haynes A. , Gouma P.
Published: July 2010

The focus of this study is the development of polyaniline based hybrid systems for selective room temperature detection of NO2. The electrospinning technique has been employed to produce highly dispersed nanocomposites of leucoemeraldine base polyaniline (LEB-PANI) with cellulose acetate (CA) as a secondary component. The nanocomposites exhibit sensitivity and selectivity to NO2 down to 1 ppm with response time of 70s and recovery time of 155s. Spectroscopic analyses of the nanocomposites reveal that the molecular interactions between cellulose acetate and LEB-PANI yields enhanced sensitivity and selectivity to NO2. DC electrical resistance measurements of the composite during exposure to the analyte suggest that the response mechanism has some dependency on the humidity level in the gas chamber. This is found to be partly attributed to the byproduct of hydrolyzed CA: acetic acid. Infrared spectroscopy reveals that the acetate ions from the acid and polymer transforms base groups of LEB-PANI to higher oxidized states and affix to quinoid, benzenoid, and imine groups along polyaniline’s chain. These sites operate as additional reactions sites along the polymer backbone for increased ion mobility and aid in retaining the sensor’s stability and selectivity under varying gas atmospheres. This paper details the results from sensing experimentation and classical characterization techniques in an effort to develop a paradigm for chemical sensing with CA-PANI nanocomposites.
Extremely Stretchable Supercapacitors Based on Buckled Single-Walled Carbon Nanotube Macro-Films
Authors: Yu Cunjiang , Jiang Hanqing
Published: July 2010

Flexible and stretchable electronics have attracted extensive attention and research efforts recently. As an indispensible component, energy storage device that is able to bear large mechanical strain and be integrated with the stretchable electronics makes the whole system stretchable. Here we report reversibly stretchable supercapacitors using buckled single-walled carbon nanotube (SWNT) macro-films as the electrodes, which have controllable wavy geometries and show extremely high mechanical stretchability with the utility of polydimethylsiloxane (PDMS) as the elastomeric substrates. The stretchable supercapacitors exhibit very stable capacitance under cyclic stretching and releasing, and comparable energy and power densities with those using pristine SWNT macro-films as electrodes.
Nano-Manipulation Device With Parallel Kinematic Micro-Positioning Stage and Integrated Active Cantilever
Authors: Dong Jingyan , Ferreira Placid M.
Published: July 2010

This paper discusses the design, analysis, fabrication and characterization of a MEMS device for nano-manufacturing and nano-metrology applications. The device includes an active cantilever as its manipulator that is integrated with a high-bandwidth two degree-of-freedom translational (XY) micro positioning stage. The cantilever is actuated electrostatically through a separate electrode that is fabricated underneath the cantilever. Torsion bars that connect the cantilever to the rest of the structure provide the required compliance for cantilever’s out-of-plane rotation. The active cantilever is carried by a micro-positioning stage, which enables high-bandwidth scanning to allow manipulation in three dimensions. The design of the MEMS (Micro-Electro-Mechanical Systems) stage is based on a parallel kinematic mechanism (PKM). The PKM design decouples the motion in the X and Y directions and restricts rotations in the XY plane while allowing for an increased motion range with linear kinematics in the operating region (or workspace). The truss-like structure of the PKM also results in increased stiffness and reduced mass of the stage. The integrated cantilever device is fabricated on a Silicon-On-Insulator (SOI) wafer using surface micromachining and deep reactive ion etching (DRIE) processes. The actuation electrode of the cantilever is fabricated on the handle layer, while the cantilever and XY stage are at the device layer of the SOI wafer. Two sets of electrostatic linear comb drives are used to actuate the stage mechanism in X and Y directions. The cantilever provides an out-of-plane motion of 7 microns at 4.5V, while the XY stage provides a motion range of 24 microns in each direction at the driving voltage of 180V. The resonant frequency of the XY stage under ambient conditions is 2090 Hz. A high quality factor (∼210) is achieved from this parallel kinematics XY stage. The fabricated stages will be adapted as chip-scale manufacturing and metrology devices for nanomanufacturing and nano-metrology applications.
Protection High Speed Trains Against Lateral Wind Effects
Authors: Sanz Bobi Juan de Dios , Suarez Berta , Garzo´n Nu´n˜ez Jorge , Brunel Va´zquez Juan Andre´s
Published: July 2010

The present paper, describe how to carry out the study of the influence of strong cross winds on high-speed trains, and how to draw conclusions to mitigate these effects by means of analysis with computer fluid dynamics. Due to the high speed increase mileage in the railway traffic and the lightening of the axis weight, the effect of the aerodynamic loads on the trains due to strong cross winds are becoming more important. These winds have a negative effect on the stability of trains travelling at high-speed. They can disturb the normal operation, cause damages in the infrastructures or even accidents like derailment or overturning. The objective of this paper is to provide, to study and to evaluate solutions and countermeasures, such as wind breaking structures with different morphologies, that mitigate the effects of the aerodynamic loads produced by the cross wind. The study is focused on the geographical and operative conditions of a high-speed line in Spain, the Madrid–Barcelona high speed line. The most affected zones by the cross wind effects have been selected [1] and the two high-speed trains that operate in this line have been considered in the study (they can circulate up to 350km/h). Infrastructures on which the train runs have also been taken into account: bridges and ground tracks or embankment. With two-dimensional analysis and static models, the aerodynamic forces acting on these two vehicles, and the improvements achieved in preventing the harmful cross wind effects by means of wind fence have been measured. A commercial CFD software (Computer Fluid Dynamics) has been used for this purpose and deep analysis of the aerodynamic loads have been carried out. Different wind fence shapes have been studied, with different heights, bending angles on the top and porosities. This made possible to compare multiple solutions, and to adapt the characteristics of the new devices to the specific situations in which higher protection is required. The result is a quasi-ideal wind fence. These fences minimize the aerodynamic loads on the surface of train. The results obtained have been compared with the experimental information of other studies and projects. Cost estimation has also been made to assess the viability of these countermeasures.
Truss Disposition Optimization Using the Linear Extended Interior Penalty Function
Authors: Kuntjoro Wahyu , Azmi Azlin Mohd
Published: July 2010

This paper describes the development of truss optimization by finding its optimum topology (member disposition). The objective of this work is to obtain the truss with minimum weight that able to meet its design requirement (design constraints). Optimization is a mathematical technique used to find an optimum design, a design that minimize a certain objective function but still meet its design constraints. In this research, the objective function was the weight of the structure while the constraints were strength and displacement. Optimization was done by removing members which do not contribute to the load carrying capacity. Through conventional member size optimization non contributing members were identified and deleted. Linear Extended Interior Penalty Function was utilized to accomplish the mission. The truss structural responses were found by Finite Element Analysis coupled with an approximation procedure. Examples of a three-bar and six bar truss structures were demonstrated. Results showed that the truss topology could be optimized by members deletion strategy using the optimization procedure reported in this paper.
Rear Seated Child Injury Risk Experimental Measures Related to Vehicle Front Seat Performance in Rear Impacts
Authors: Saczalski Kenneth J. , Pozzi Mark C. , Burton Joseph Lawson
Published: July 2010

Recent field accident statistical studies dealing with injury risk assessment of rear seated children in rear impacts indicated a doubling of AIS 2+ injuries when front seats deformed, and a 61 percent increase in fatal injury for rear-seated children, as compared to front-seated children, in rear impacts. Several interrelated factors, which influence child injury risk in rear impacts, were not evaluated in these field accident statistical studies. These factors include: rear-impact severity levels; front occupant sizes; front seat strength variations and protection levels; vehicle type; (i.e. minivan, sedan, etc.); rear child sizes; and, rear child restraint types. This current study uses an experimental “multi-variable” crash test approach, and “inferred statistical” methodology, to scientifically evaluate the several key factors that effect rear child injury risk in rear impacts. This “multi-variable” methodology was previously utilized by the authors for study of front-seated adult injury risk assessment. Various sizes of rear child surrogates (i.e. 6 month-old up to the 6 year-old Hybrid III size), located behind different sizes of front adult surrogates (i.e. small 50kg female up to larger male surrogates ballasted to 110kg) seated in different strength front seats, were dynamically tested at rear-impact severity speed change levels ranging from about 20 to 50 kph. Both sled-body-buck and full vehicle crash tests were used in this study. Front seat strength levels ranged from the weaker 3.2kN level for single recliner (SR) seats, without belts attached to the seatback, up to the stronger belt-integrated seat (BIS) levels of about 14.7kN. The study results demonstrate that, even absent rear crush intrusion, the easily deforming SR front seats pose a high risk of injury to the rear child, regardless of vehicle type, in contrast to stronger and safer BIS designs.
An Algorithm for Reducing the Size of Finite Element Closed-Form Source Code Files
Authors: McCaslin Sara , Lawrence Kent
Published: July 2010

Closed-form solutions, as opposed to numerically integrated solutions, can now be obtained for many problems in engineering. In the area of finite element analysis, researchers have been able to demonstrate the efficiency of closed-form solutions when compared to numerical integration for elements such as straight-sided triangular [1] and tetrahedral elements [2, 3]. With higher order elements, however, the length of the resulting expressions is excessive. When these expressions are to be implemented in finite element applications as source code files, large source code files can be generated, resulting in line length/ line continuation limit issues with the compiler. This paper discusses a simple algorithm for the reduction of large source code files in which duplicate terms are replaced through the use of an adaptive dictionary. The importance of this algorithm lies in its ability to produce manageable source code files that can be used to improve efficiency in the element generation step of higher order finite element analysis. The algorithm is applied to Fortran files developed for the implementation of closed-form element stiffness and error estimator expressions for straight-sided tetrahedral finite elements through the fourth order. Reductions in individual source code file size by as much as 83% are demonstrated.
Hydraulic-Based Stability Analysis of a Tongue and Groove Joint Test
Authors: Manko David J. , Whitlow Jesse W.
Published: July 2010

A tongue and groove joint test is being conducted to quantify the stability characteristics for this class of leakage joint. The test hardware was designed to facilitate comprehensive reconfiguration of the joint geometry so that all parameters affecting joint stability can be evalauated. Excursive (static) and oscillatory (dynamic) instabilities are expected dependent on joint configuration and operational parameters. Hydraulic-based stability analyses were conducted on a pre-test basis to examine joint response. It is concluded from these analyses that physically damaging oscillatory instabilities are most likely to occur when the joint is configured with a movable groove. Physical reasoning for this conclusion is provided in the paper.
Seven Modules Risk Assessment System of Urban Gas Pipeline Network
Authors: You Qiuju , Zhu Wei , Men Yongsheng
Published: July 2010

The paper presents a complete risk assessment system of urban natural gas network from seven modules. Pipeline hazard scenarios are analyzed and the reasons for seven modules risk assessment system model are presented. Based on objective data of various pipeline sections, the assessment system also allows sections of pipeline to be ranked into a risk hierarchy by using advanced scientific mathematical treatment methods. The system is displayed in geographic information system (GIS) platform, in order to implement data resource sharing and visualization of assessment results. Therefore, the dynamic and safety management of gas pipeline network is achieved and the safe and reliable operation of urban gas pipeline network can be ensured. An application based on a real case study was undertaken so that the effectiveness of the assessment system could be verified.
Experimental Validation of a CORE Type Power Transformer
Authors: Almeida E. Emanuel , Mendes He´lder G. , Pinho A. Marques
Published: July 2010

The current paper presents the validation of a finite element (FEM) design methodology for a CORE type power transformer. Any new methodology can only be implemented when it generates significant added value. The application of FEM to the design of power transformers leads to lighter, more balanced mechanical structures that are more economical to manufacture. To be sure that the methodology is a good predictor of the stress and strain effectively encountered by the power transformer, it is necessary to measure stress and strain during loading and compare those measurement values with the original FEM predictions. The current paper begins by first presenting the FEM predictions for a CORE type power transformer. Secondly, by means of extensometry, the strains induced in the tank during loading were measured and the stresses present in the tank were estimated from basic stress-strain relationships. The feedback given by the strain measurements served as a validation tool for the FEM design predictions.
A Multiple-Beam Tuning-Fork Gyroscope With High Quality Factors
Authors: Wang Ren , Durgam Shiva Krishna , Hao Zhili , Vahala Linda
Published: July 2010

This paper reports on the design, fabrication, and testing of a multiple-beam tuning-fork gyroscope featuring high Quality factors (Q). A multiple-beam tuning-fork structure is designed to achieve high Qs in its drive mode and sense mode. The gyroscope is fabricated on a 30μm-thick SOI wafer using a one-mask fabrication process. The measured Qs of the fabricated gyroscope are 162,060 in the drive-mode and 85,168 in the sense mode at an operation frequency of 16.8kHz. Under a frequency split of 6Hz, the prototype device demonstrates a rate sensitivity of 0.02mV/°/sec.
Hybrid Power Systems for Construction Machinery: Aspects of System Design and Operability of Wheel Loaders
Authors: Filla Reno
Published: July 2010

This paper will examine the wheel loader as a system with two parallel energy conversion systems that show a complex interaction with each other and with the power source. Using a systematic design approach, several principle design solutions for hybridization can be found. Furthermore, the human operator with his/her control actions needs to be considered as part of the total system. This paper will therefore also connect to results from ongoing and previous research into operator workload and operability.
Measurement of Cohesive Laws and Related Problems
Authors: Stigh Ulf , Alfredsson K. Svante , Biel Anders
Published: July 2010

Cohesive modelling provides a simple method to introduce a process region in models of fracture. It is computationally attractive since it blends into the structure of finite element programmes for stress analysis. The development of computational methods and applications of cohesive modelling has accelerated during recent years. Methods to measure cohesive laws have also been developed. One class of such methods is based on the path-independence of the J-integral. By choosing a path encircling the cohesive zone, J can be shown to be given by the area under the traction-separation relation for the cohesive zone. Using an alternative path, J can in some cases be directly related to the applied load and deformation with relatively modest or no assumptions on the material behaviour. Thus, the cohesive law can be measured. Methods to measure cohesive laws for different specimen geometries are presented. The methods are used to measure the cohesive law in peel, shear and mixed-mode for an adhesive layer. A new method to measure cohesive laws in shear is presented. The method is shown to give accurate data with a much smaller test specimen than earlier methods.
Forced Vibration of an Initial Stressed Rectangular Composite Thick Plate With a Cylindrical Hole
Authors: Yahnioglu Nazmiye , Yesil Ulku Babuscu
Published: July 2010

Within the framework of the Three-Dimensional Linearized Theory of Elastic Waves in Initially Stressed Bodies, the influence is studied of the initial stretching of a composite thick plate containing a cylindrical hole on the stress concentration around a hole caused by the action of the additional uniformly distributed dynamic (time-harmonic) normal forces on the upper face of the plane. The corresponding problem formulation is presented and, in order to find the solution to this problem, the finite element method is employed. The numerical results on the concentration of the stress around the hole and the influence of the initial stretching on this concentration are presented. According to these results, in particular it is established that the stress distributions around the cylindrical hole changed significantly with the initial stretching force.
Dynamics and Rheology of Linear Entangled Polymer Nanocomposites
Authors: Kabanemi Kalonji K. , He´tu Jean-Franc¸ois
Published: July 2010

Polymers filled with nanoparticles have attracted considerable technological and scientific interest during the recent past, because of dramatic enhancements in physical, thermal, and mechanical properties observed experimentally. It is necessary to understand the rheological behavior of such mixtures so as to improve their manufacturing procedure.
Novel MEMS-Based Boiler Development for Low Temperature Applications
Authors: Prather K. , Hemphill H. , Pjescic I. , Tranter C. , Dorton J. , Elliott F. , Weiss L.
Published: July 2010

A novel MEMS-based boiler is fabricated and tested. The device is designed to operate from low-temperature heat sources using capillary action channels. The channels supply working fluid to the heated boiler surface, eliminating the need for traditional working fluid pumps. Two basic types of construction are evaluated. First, a more traditional silicon-based device is constructed and tested. Fabrication of the silicon boiler utilizes standard micro-fabrication practices. Second, a copper-based unit is fabricated and tested. Fabrication of the copper boiler focusses on low-cost techniques performed outside the scope of traditional micro-fab procedures. Results of these tests show the promise of non-traditional metals in low-temperature MEMS-based applications. The effectiveness of the copper boilers is shown to be 60% greater than their silicon counter parts. The copper-based prototypes exhibited a maximum evaporation rate for working fluid pumped across the boiling surface of 4.21 mg/sec.
A Cam-Based Electro-Hydraulic Variable Valve Timing System for Pneumatic Hybrid Engines
Authors: Pournazeri Mohammad , Fazeli Amir , Khajepour Amir
Published: July 2010

In this work, a new type of cam-based variable valve timing system has been proposed based on the “lost motion” principle. Using this mechanism, the problems with the valve transition time and control complexity which are still serious concerns for camless valve train systems are solved. This mechanism not only allows the engine to work at different modes of operation as an air hybrid engine but also enables it for continuous torque management. In this system, the control methodology utilizes a cam position feedback to control the valve opening timing. A combination of hydraulic and mechanical systems was utilized to offer high flexibility and robustness in the engine valve control system. A zero dimensional analysis is also conducted to evaluate the functionality and performance of the proposed system.
Dynamic Analysis of Tensile Preloaded Woven Composites Under Low Velocity Impact
Authors: Thatte Bhushan S. , Kelkar Ajit D.
Published: July 2010

In this paper, the effects of low-velocity impact on the E-Glass Epoxy woven composite laminates under tensile preload are presented. Due to the low-velocity impact loading, laminate suffers an extensive internal damage such as delaminations and the damage on the back face. The effect of preload can significantly change the impact behavior and progressive damage mechanics. Therefore the study of impact damage susceptibility of these woven composite laminates under tensile preload (corresponding to tensile strain) is increasingly important. While considerable experimental and analytical studies have been made on the low velocity impact phenomenon, very little work is reported in the area of effect of preloads on the damage mechanics for E-Glass Epoxy woven composite laminates subjected to low velocity impact. A detailed finite element mosaic model was developed using Virtual Proving Ground (VPG) software. Dynamic analysis was performed using LSDYNA® finite element software. A plate consisting of 10 layers of E-Glass/EPON 862-W (10EG) was modeled using three dimensional orthotropic elastic brick elements. Preload boundary conditions were simulated using in-plane displacement for three different incremental values (0.08% strain, 0.16% strain and 0.24% strain) representing realistic assembly conditions. The simulation results were compared for their maximum load carrying capacity. It was observed that with increase in preload, laminate looses its maximum load carrying capacity.
Biologically Inspired Robotic Microswimmers
Authors: Hesse William R. , Federici Matthew , Casale David M. , Fink Peter , Milton Basil , Kim Min Jun
Published: July 2010

Drug delivery systems have had a profound impact on several branches of medicine. Engineers and researchers alike have labored to create a controlled drug delivery device capable of regulated dosage release and a specific cell targeting mechanism. The growing field of biomimicry has inspired several of these drug systems, though success has been limited. The flagellated low Reynolds number propulsion system of Salmonella typhimurium has inspired this specific delivery complex. In this system, the helical flagellar filaments of S. typhimurium are isolated from the bacteria’s cell body and are bound to functionalized paramagnetic microspheres. As a magnetic field is applied to this device, the microsphere rotates, inducing rotation of the helical flagella. This motion creates a locomotive force and drives the device in a predestined direction.
Nanocrystalline FCC Thin Films Are More Prone to RT Creep Than What We Think
Authors: Karanjgaokar Nikhil , Chasiotis Ioannis
Published: July 2010

Although nanocrystalline (Nc) metallic thin films are excellent candidate materials for Microelectromechanical Systems (MEMS) and microelectronics due to their outstanding yield strength, serious reliability concerns arise from their increased room temperature creep rates. A comprehensive experimental investigation was carried out to extract the strain-rate dependent mechanical behavior of Au (38 nm grain size) and Ni (20 nm grain size) micron-thin films conducted for the very first time at strain rates in the broad range of 10−6 – 10 /s which spans time scales from ms to hours. Nc-Au films demonstrated a clear bi-linear change in their inelastic properties, i.e. the elastic limit and its yield strength, while the Nc-Ni films showed a linear increase in their inelastic properties over the same loading rates. This unexpected trend for the Au films emphasized the significant contribution of room temperature (RT) creep at strain rates between 10−6 – 10−4 /s, at which rate, larger grain size materials are not prone to creep at RT. This realization prompted a series of novel microscale creep experiments, the first of their kind, at time scales of 104–105 s. An important finding was that the first stage of creep, primary creep, proceeds at a very fast rate, of the order of 10−7 /s, lasting for 5–6 hours after the application of a stress. Furthermore, multi-stage creep experiments revealed that the primary creep rate decreased with the order of creep cycle, while the steady state creep response remained the same in all creep cycles. This creep response of nanocrystalline FCC films was modeled via a non-linear viscoelastic creep model that captured the effect of applied stress on both primary and steady-state creep regimes.
Optimization of Jacket Type Offshore-Tower Under Uncertainties
Authors: Togan V. , Karadeniz H. , Daloglu A. T.
Published: July 2010

In this work, economical design implementation of a jacket tower, which is subjected to some uncertainties associated with the loads, the material properties, and environmental data etc., is presented. In order to fulfill the defined task, reliability based design optimization (RBDO) concept combining the reliability analysis and optimization is performed with reliability constraints including stress, buckling, and the lowest natural frequency. The probabilistic constraints are evaluated by using Reliability Index Approach (RIA) and Performance Measure approach (PMA). The mass of the tower is considered as being the objective function; the thickness and diameter of the cross-section of the jacket members are taken as being design variables of the optimization.
Electrohydrodynamic Modeling for Microfluidic Devices
Authors: Zeng Jun
Published: July 2010

Since the inception of microfluidics, the electric force has been exploited as one of the leading mechanisms for driving and controlling the movement of the operating fluid (electrohydrodynamics) and the charged suspensions (electrokinetics). Electric force has an intrinsic advantage in miniaturized devices. Because the electrodes are placed cross a small distance, from sub-millimeter to a few microns, a very high electric field is rather easy to obtain. The electric force can be highly localized with its strength rapidly decaying away from the peak. This makes the electric force an ideal candidate for spatial precision control. The geometry and placement of the electrodes can be used to design electric fields of varying distributions, which can be readily realized by MEMS fabrication methods. In this paper we examine several electrically driven liquid handling operations. We discuss the theoretical treatment and related numerical methods. Modeling and simulations are used to unveil the associated electrohydrodynamic phenomena. The modeling based investigation is interwoven with examples of microfluidic devices to illustrate the applications. This paper focuses on detailed physical simulations of component-level operations. Since the components must be integrated to form a functional system in order to provide desired services, system-level complexities in both architecture and execution also need to be addressed. Compared to the state of the art of computer-aided design for microelectronics, the modeling aid for microfluidics systems design and integration is far less mature and presents a significant challenge, thus an opportunity for the microfluidics research community.
Effect of Low Field Magnetic Annealing on the Viscoleastic Behavior of a Structural Epoxy
Authors: Tehrani Mehran , Al-Haik Marwan , Garmestani Hamid , Li Dongsheng
Published: July 2010

In this study the effect of moderate magnetic fields on the microstructure of a structural epoxy system was investigated. The changes in the microstructure have been investigated quantitatively using wide angle x-ray diffraction (WAXD) and pole figure analysis. The mechanical properties (modulus, hardness) of the epoxy were probed using nanoindentation. Using the continuous complex compliance analysis, the effect of the low magnetic fields on the viscoelastic properties of the epoxy was investigated. The phase lag angle was measured for both neat and magnetically annealed polymer. The results of this investigation reveal that under low magnetic fields both the quasi-static mechanical properties together with the viscoelastic behavior of the epoxy have been improved.
Simulation of Phonon Transmission Through Graphene With a Green’s Function Method
Authors: Huang Zhen , Fisher Timothy , Murthy Jayathi
Published: July 2010

In this paper, phonon transmission through a graphene sheet is investigated using an atomistic Green’s function (AGF) method. Reported best-fit results from first-principles calculations using a 4th nearest neighbor force-constant (4NNFC) model are used to establish the matrices that describe the interactions among carbon atoms. Calculations reveal that graphene dispersion curves so obtained are in good agreement with experiments as well as other published first-principles calculations. The effect of carbon isotopes on thermal conductance is investigated, and the results reveal that isotopic doping moderately reduces both phonon transmission function and thermal conductance. The phonon transmission function of each vibrational branch in the heterogeneous interface is also calculated based on a method described in recent work, and comparisons indicate the major and minor channels of phonon transport through graphene. The results herein offer a useful reference and suggest directions for future research on thermal applications of this material.
Generalized Variational Principles of Electro-Magneto-Thermo-Elasto-Dynamics
Authors: Song Haiyan , Zhou Zhengong , Liang Lifu , Liu Zongmin
Published: July 2010

Based on coupled properties of electricity, magnetism, heat and force, it is hard to solve the material’s electric behavior, magnetic behavior, temperature field, stress distribution and deformation distribution under the action of all kinds of external fields in usual way. It is necessary that the problems are solved by numerical methods. However variational principle is the foundation of these numerical methods which were widely used. In this paper, the generalized variational principles of electro-magneto-thermo-elasto-dynamics are established by variational integral method. And these variational principles can be degenerated into variational principles of simple coupled properties materials, which offer theoretical support for numerical methods of coupled problems of electro-magneto-thermo-elasticity.
Thermographic Evaluation of SS 304 Material During Monotonic Loading
Authors: Prakash Raghu V. , Thiyagarajan Kathirvel , Chindam Chandraprakash , Balasubramaniam Krishnan
Published: July 2010

Infrared thermographic technique was employed for evaluating the temperature response in a Stainless steel grade 304 material subjected to different loading conditions such as monotonic tensile and compressive loading. In-situ temperature measurements were made from surface of the material by an infrared thermographic camera (JADE LWIR, Cedip Infrared Systems) while the material is being loaded. Cylindrical low cycle fatigue (LCF) samples were used in this study for monotonic tensile loading. Similarly, samples of aspect ratio 1.5 were used for analyzing monotonic compressive loading. As a material is subjected to tensile elastic loading, it undergoes cooling and when subjected to compressive loading, it undergoes heating. This phenomenon is called thermo-elastic effect. Based on our experimental observations, in case of monotonic tensile loading, the temperature of the material decreases till the material yields due to thermo-elastic effect and increases as the material plastically deforms, due to conversion of mechanical work done on the specimen into heat. But for the case of compressive loading, the temperature increases when the material is stressed in both cases of elastic as well as the elasto-plastic segment. This paper discusses the slope of the temperature response with respect to strain induced in the material and the effect of loading rate on the temperature measurements for the monotonic tensile and compressive loading. Comparison between the thermo-elastic slopes revealed that the thermo-elastic slope for the tensile loading is steeper than the slope from the compressive loading due to surface area contraction during the tensile loading and vice-versa. Experiments conducted at various loading rates ranging from 0.75 to 10 mm/min reveals that as the loading rate increases, temperature of the material increases.
Application of the Fast Multipole Boundary Element Method to Analysis of Sound Fields in Absorbing Materials
Authors: Cui Xiaobing , Ji Zhenlin
Published: July 2010

As an advanced boundary element method (BEM) employing the fast multipole algorithm, the fast multipole boundary element method (FMBEM) has been developed to realize fast computation and drastic memory saving for the large-scale problems. In the present study, The FMBEM is applied to analyze the interior sound fields that partially-filled with sound-absorbing material. The basic principle of FMBEM is introduced briefly, and the domain decomposition approach for FMBEM is investigated. The numerical errors in multipole expansions are analyzed in order to obtain the sufficient accuracy for the FMBEM computation of sound fields in sound-absorbing material. The sound pressures in a duct partially-filled with sound-absorbing material are calculated by using the present FMBEM and the conventional BEM, and then the computational accuracy and efficiency of FMBEM are discussed by comparing the results from the two methods. The numerical results showed that the FMBEM is capable to deal with the sound fields problems in sound-absorbing material, and can save computational time for the acoustic problems with large number of nodes.
Electrowetting of Room Temperature Ionic Liquids (RTILs) for Capillary Force Manipulation
Authors: Vasudev Abhay , Jagtiani Ashish , Du Li , Hu Jun , Gao Yanan , Zhe Jiang
Published: July 2010

The feasibility of using room temperature ionic liquids (RTILs) as the electrowetting liquid for capillary force microgrippers was studied. The non-volatility and thermal stability of ionic liquids make them suitable for droplet based microgripping application in high temperature and vacuum environments. Electrowetting on co-planar electrodes was utilized to dynamically change the contact angle of a 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF6) liquid bridge to control the capillary lifting forces. The lifting force generated by the liquid bridge was experimentally characterized. The maximum capillary force was 146μN. The dynamic response of the BmimPF6 liquid bridge was also characterized.
Design Arbitrary Shaped 2D Acoustic Cloak Without Singularity
Authors: Hu Jin , Zhou Xiaoming , Hu Gengkai
Published: July 2010

A method is proposed to design arbitrary shaped two dimensional (2D) isotropic-inertia acoustic cloaks without singularity. The method is based on the deformation view of the transformation method, where the transformation tensor A is identified as the deformation gradient tensor and the transformed material parameters can be expressed by the principal stretches in the principal system of the deformation. The infinite material parameters of a perfect 2D cloak is induced by an infinite principal stretch in one direction while the other two remains finite at the inner boundary during the transformation. To circumvent this difficulty, for a 2D cloak we can choose the principal stretch perpendicular to the cloak plane to be also infinite but in the same order as the infinite principal stretch in the cloak plane during the transformation, so the transformed material parameters may keep finite. To illustrate this idea, the analytical expressions of nonsingular material parameters for a cylindrical acoustic cloak are given. For the acoustic cloaks with irregular shapes, the numerical method is proposed to evaluate the principal stretches and in turn the nonsingular material parameters. The designed 2D cloaks are validated by numerical simulation.