bluuebunny/crossref_metadata_2025 huggingface dataset:
Rotor-Blade Coupled Torsional Vibration Analysis Using Modal Parameters Based on FEM Analyses and Experiments
Authors: Okabe Akira , Shiohata Koki , Kudo Takeshi , Yoda Hideo , Sakurai Shigeo , Nakajima Daiki
Published: May 2012

The quasi-modal technique is used for rotor-blade coupled torsional vibration analysis due to its unique characteristics in providing a visually reduced model. Given the rapid advances in computation technology in recent years, the FEM method is now widely used as a standard product design tool in many industries, because it can reflect a more detailed structure quickly in the design process. In this paper we proposed the use of a commercially available FEM method program (ANSYS®) to calculate quasi-modal parameters of the bladed disk system. This program was applied to the model rotor of two disks with continuously coupled blades. Rotor-blade coupled torsional frequencies of the model rotor based on the FEM based quasi-modal technique were compared with a complete FEM analysis of the model rotor. Both methods gave results in good agreement. We also compared the frequencies measured through rotation testing of the model rotor to calculations. Finally, we presented the procedure for calibrating modal parameters based on the measured blade-disk frequencies. Quasi-modal modeling was judged practicable for feeding back test results to achieve higher accuracy.
Theoretical Design Consideration of a Small Scale Thermoplastic Waste Recycling Machine
Authors: Gbadam E. K. , Simons A. , Adzimah S. K. , Mborah C.
Published: May 2012

The use of plastics has increased over the past two to three decades especially in the areas of medicine, engineering and domestic application. Consequently, it consumption has generated increase in industrial and domestic waste. Since most plastics are not biodegradable they tend to have adverse short and long term effects on the environment, living organisms and the economy and the situation is not different in Ghana. Although some efforts are being made to reclaim the waste, it is very prudent that recycling of the collected waste is included in this scheme. This paper seeks to outline the design of a machine to recycle plastic waste. This will help keep the environment clean, safe, save energy and will also leads to resource recovery and the creation of jobs for the unemployed.
Open Production: A Scientific Framework for Co-Creative Product Realization
Authors: Redlich Tobias , Wulfsberg Jens , Bruhns Franz-Ludwig
Published: May 2012

Globalization and the use of technology call for an adaptation of value creation strategies. As the potential for rationalization and achieving flexibility within companies is to the greatest possible extent exhausted, approaches to the corporate reorganization of value creation are becoming increasingly important. In this process, the spread and further development of information and communication technology often provide the basis for a reorganization of cross-company value nets and lead to a redistribution of roles and tasks between the actors involved in value creation. While cooperative, decentralized and self-organizing value creation processes are in fact being promoted, the associated potential for development and production engineering is being underestimated and hence not implemented sufficiently. This contribution will first describe the emerging transformation in value creation taxonomy and then, on the basis of a case study, develop an adequate framework for value creation configuration.
Impact of Surface Roughness on Formation of Micro Cracks and Fatigue Performance
Authors: Abou-Hanna Jeries , Lozano Jose , Abuzaid Wael
Published: May 2012

Tungsten-doped diamond-like carbon (DLC) coatings have been magnetron sputtered with chromium and chromium/tungsten carbide dual interlayers onto 410 stainless steel rods. The surface finish (Ra) of the substrate before deposition was 0.10–0.25 μm for a set of rough rods and 0.05 to 0.10 μm for a set of smooth rods. SEM analyses revealed different kinds of flaws in the as-deposited films (virgin coating). Two samples, one from each set, were fatigue tested under uni-axial tension to determine the effect of the substrate surface roughness on the performance of the coating. Surface analysis revealed a different response between films deposited on rough and smooth substrates. Severe failure modes such as spalling and wide cracks developed from initial film flaws in the rough substrate sample. Cracks and film spalling were also observed in the smooth substrate sample but the severity, in terms of crack dimensions and density was considerably lower than the rough substrate sample.
X-Link Gel as Hydraulic Fracturing Material
Authors: Meng C. , Pater C. J. de
Published: May 2012

Hydraulic fracturing is a fracturing processes initiated from a pressurized open borehole section into solid formations. The process is characterized by solid-fluid interaction. On the solid side, the formation is deforming with the propagation of the fracture front and pressurization of the fracture face. At the same time the fluid is driven by the borehole pressure to flow into the narrow fracture cavity. At same time, the fluid may also infiltrate into the porous rock media. The fracture cavity is supported by the fluid pressure. In turn, the fluid distribution depends on the fracture conductivity related to the cavity width (aperture). The mass balance is maintained amongst the injection rate, fracture volume increment and leak-off A series of experiments have been performed to initiate fracture in a number of natural rock samples confined by a tri-axial cell. As the tight and shale gas and oil reservoirs are found global-wise, stimulation techniques such as polymer flooding and fracturing start to draw attention. We have employed X-link gel as the fracturing material in contrast with the Newtonian viscous fluid. From the results, we found that the ability to sustain certain yielding stress made the gel unlikely to infiltrate into the porous media as leak-off and likely to create a unanimous fracture. This paper is about the tests results and analysis that describe the gel behavior.
A Viscoplasticity Model for Solder Alloys
Authors: Lee Yongchang , Basaran Cemal
Published: May 2012

Demand for long-term reliability of electronic packaging has lead to a large number of studies on visco-plastic behavior of solder alloys. Various creep models for solder alloys have been proposed. They range from purely empirical to mechanism based models where dislocation motion and diffusion processes are taken into account. In this study, most commonly used creep models are compared with the test data and implemented in ABAQUS to compare their performance in cycling loading. Finally, a new creep model is proposed that combines best features of many models. It is also shown that, while two viscoplasticity models may describe the same material stress-strain rate curves equally well, however they may yield very different results when utilized for cycling loading. One interesting observation of this study is that the stress exponent, n, also depends on the grain size.
Crystallographic Texture of Nitinol and its Effects on Macrophage
Authors: Fonte Matthew , Saigal Anil
Published: May 2012

The use of Nitinol for medical purposes was first reported in the late 1960’s. Today Nitinol is commonly used for the manufacture of stents, which are primarily used in peripheral and coronary bypass graft interventions. The application of NiTi in orthopedics is an exciting prospect but one that has yet to be realized. Nitinol’s unique mechanical behavior is derived from the coordinated atomic movements manifesting in phase transformations from cubic austenite to monoclinic martensite. These phase transformations are solid-to-solid phase transformations that occur without diffusion or plasticity, potentially making them reversible. They involve changes in the crystalline structure that can be induced by changes in either temperature or stress. In addition to phase transformations, Nitinol’s mechanical strength is strongly dependent on the alloy composition and the method in which the material is processed, i.e. rolled, drawn, extruded, or forged. The mechanical work, combined with the intermediate heat treatment steps, contribute to modify microstructure, transformation temperatures and mechanical properties. These manufacturing processing steps lead to texturing (crystallographic alignment) of the material. Alignment of the atomic planes from texture in the polycrystalline material have a marked influence on the mechanical response by either limiting or promoting phase transformations and shape recovery strains. Nitinol is an established biomaterial, whose biocompatibility is heavily grounded on the inertness of titanium based oxides that usually dominate the surface exterior. Surfaces that vary significantly in their chemistry, topography and corrosion resistance have different degrees of biocompatibility. As such, a better understanding of the biological response of NiTi’s surfaces with different crystallographic textures in needed. In the present research, a macrophage study is performed whereby 6 plates that are highly textured NiTi with different surface finishes are incubated with cells for approximately 3 days and then tumor necrosis factor (TNF), a pro-inflammatory cytokine production and cellular proliferation are assessed.
A New Adaptive Generalized Predictive Control Algorithm for Nonlinear Processes
Authors: Abu-Ayyad Ma’moun , Dubay Rickey , Pramujati Bambang
Published: May 2012

This paper presents a unique method for improving the performance of the generalized predictive control (GPC) algorithm for controlling nonlinear systems. This method is termed adaptive generalized predictive control which uses a multi-dimensional surface of the nonlinear plant to recalculate the controller parameters every sampling instant. This results in a more accurate process prediction and improved closed-loop performance over the original GPC algorithm. The adaptive generalized predictive controller was tested in simulation and its control performance compared to GPC on several nonlinear plants with different degrees of nonlinearity. Practical testing and comparisons were performed on a steel cylinder temperature control system. Simulation and experimental results both demonstrate that the adaptive generalized predictive controller demonstrated improved closed-loop performance. The formulation of the nonlinear surface provides the mechanism for the adaptive approach to be readily applied to other advanced control strategies making the methodology generic.
Numerical Simulation of Blood Flow in the Presence of Embolizing Agents
Authors: Johnson Nessa , Abraham John , Helgeson Zach , Hennessey Mike
Published: May 2012

A numerical simulation has been performed on the blood flow patterns in a multi-branch artery during an embolization procedure. The procedure, performed with drug-eluting particulates is designed to occlude blood vessels which feed a tumor. As particulates are injected into the blood stream, they interfere with the flow patterns which previously had existed uninterrupted. This interference causes a maldistribution of flow down daughter artery branches. The patterns of maldistribution change as the embolizing particle travels down the artery toward the target or as particles begin to accumulate at the target. A consequence of the alterations of flow patterns is that future injections of particulates may be diverted from their intended targets and may, consequently, travel down non-targeted artery branches towards otherwise healthy tissue.
CFD and Acoustical Analyses for Coastal Highway Erosion
Authors: Zhang Ning , Li Zhuang , Klemetson Stanley , Yadagiri Saikiran
Published: May 2012

Highway 82 is located along the Gulf of Mexico and provides one of the barriers to flood damage from wave action that occurs normally along the coastal shoreline and as a result of wave surges during stormy weather and hurricanes. When the waves break over the top of Highway 82 form the south, significant erosion damage will occur on the north side of the road instead, often resulting in destruction of the shoulder and the roadway that it supports. This results in significant maintenance cost for the State of Louisiana, loss of vital access to the coastline, and destruction of the protective barrier necessary to protect the residences and uses of the land along the Gulf of Mexico. The CFD and acoustical analyses were performed to evaluate the erosion resistance of a design configuration. The CFD simulations were conducted to investigate the weather and wave conditions and the impact on the shoulder erosion. The in-situ pressure data were recorded at several locations on and downstream of the north-side shoulder, and acoustical analyses were conducted to investigate the acoustic characteristics associated with the weather and wave conditions.
CFD Modeling of Influence of Weak Catalytic Reactions on Pump Performance Parameters
Authors: Strongin Mikhail P.
Published: May 2012

In a large variety of areas, from aerospace technologies to food production, the mixing process plays an important role. Usually, a special mixer is used to help mixing. But often natural mixing process is used: liquids are set on the pump inlet without any mixer involvement, so the pump itself is used as a mixer.
Use of Numerical Techniques in the Diesel Engine Intake Manifold Optimization
Authors: Chitnis P. P. , Juttu S. , Deshmukh A. G. , Sampathkumar K. R. , Marathe N. V.
Published: May 2012

This paper is mainly focused on the design and optimization of intake manifold as regards plenum volume, shape and runner length to improve the breathing capacity of NA and TC diesel engines. The main aim of this work is to maximize volumetric efficiency of diesel engine intake manifolds in order to handle high EGR levels and ensure uniform distribution of charge to minimize cylinder-to-cylinder variation. The intake manifold is designed by using numerical techniques and analysis is carried out by employing 1D and 3D CFD simulation tools. The entire engines have been modeled in 1D-code using base manifold dimensions and validated with experimental data. Simulation result shows good agreement with the acquired real-time data of intake and exhaust manifold pressure characteristics particularly during overlap period. Also, basic engine performance, combustion pressure and NOx & Soot emissions predicted are found within 5–10% of the experimental data. This paper presents the work carried out on intake manifold design through case studies on one each NA and TC diesel engine, with and without EGR. The optimized manifold plenum volume for NA engine of approximately 75% (including runners) of swept volume and runner length of 97mm have shown considerable improvement in volumetric efficiency resulting in 2.5% improvement in bsfc. Whereas, plenum volume of 1.45 times engine displacement with same runner length shows more than 3% improvement in bsfc for TCI diesel engine. Further, transient simulation study is carried out using 3D CFD simulation tool for two complete cycles and it is observed that mass flow rate deviation between the runners is reduced to less than 5%. Shape of the runner is also modified to avoid any eddy formation in the flow path. The runner diameter is optimized. Optimization location for EGR entry and modification to runner design is also described in this paper demonstrating uniform EGR distribution with acceptable deviation.
Numerical Simulation of Heat Pipe Cooling in End Milling Operations: Part I—Thermal, Structural Static, and Dynamic Analyses
Authors: Zhu Lin , Jen Tien-Chien , Yen Yi-Hsin
Published: May 2012

In this paper, the feasibility and effectiveness of heat pipe cooling in end milling operations is investigated. A new embedded heat pipe technology was used to remove the heat generated at the tool-interface in the end milling process. Numerical studies were involved in four cases, including solid end-mill, solid end-mill with coolant, heat pipe end-mill and heat pipe end-mill with coolant. The thermal, static and dynamic characteristics of the end-mill were investigated using a numerical calculation with Fast Finite Element (FFE) plus solvers based on explicit finite element analysis software. The results indicate the heat pipe end-mill is most feasible and effective in the actual end milling processes.
Iterative Learning Control: A Comparison Study
Authors: Ouyang P. R. , Pipatpaibul Pong-in
Published: May 2012

Iterative Learning Control (ILC) is a technique of tracking control aiming at improving tracking performance for systems that work in a repetitive mode. ILC is a simple and effective control and can progressively reduce tracking errors and improve system performance from iteration to iteration. In this paper, we first classify the ILC schemes into three categories: offline learning scheme, online learning scheme, and online-offline learning scheme. In each scheme, P-type, D-type, PD-type, and switching gain learning control are discussed. The corresponding convergence conditions for each type of ILCs are presented. Then, different ILCs are applied to control a general nonlinear system with noise and disturbance. After that, various ILC schemes are tested under different test conditions to compare the effectiveness and robustness. It is demonstrated that the online-offline type ILCs can obtain the best tracking performance, and the switching gain learning control can provide the fastest convergence speed.
HVAC System Energy Minimization via Optimization of Lumped System Models
Authors: Wemhoff Aaron P.
Published: May 2012

Heating, ventilating, and air conditioning (HVAC) systems comprise nearly one third of annual household energy consumption in the United States. Energy savings can be gained by optimizing HVAC performance using a system of controls. This study applies a novel control method towards a system with an arbitrary steady-state load distribution. The new method applies multi-dimensional interpolation of optimized control configurations for various steady-state load distributions. These optimal configurations are derived using a lumped parameter simulation of the HVAC system. The new method is applied to a three-room HVAC system to demonstrate a power savings of 40% compared to an uncontrolled system. These savings compare favorably to predictions using the Variable-Air-Volume (VAV) method (37% power savings) and VAV with chiller control (33% power savings).
Prediction of Changes in System Vibration Response Using Empirical Sensitivity Functions
Authors: Yang Chulho , Adams Douglas E.
Published: May 2012

To improve noise, vibration, and harshness (NVH) performance in a mechanical system, engineers make changes in the mass, damping, or stiffness properties of components in the system. A system response prediction method using a sensitivity function is suggested to reduce the cost in the design modification process. Embedded sensitivity functions derived solely from empirical data have been applied to identify optimal design modifications for reducing vibration resonance problems. In this paper, those sensitivity functions are used to predict the changes in vibration behavior of a system with respect to the design parameter modification. The cost and time for building many prototypes and testing actual parts can be reduced by identifying the best parameters to be changed and determining the amount of modification in those design variables through the prediction of the system response before actual components are built. The method is applied to a single degree of freedom analytical model to study the accuracy of the predictions. Finite element analyses are then conducted on a three-story structure with modifications to the stiffness and mass distributions to demonstrate the feasibility of these predictions in applications to more complicated structural systems.
Electroactive Polymer (EAP) as Actuators for Biomimetic Applications
Authors: Bar-Cohen Y.
Published: May 2012

Many polymers are known to vary their shape or size when subjected to electric, chemical, pneumatic, optical, or magnetic field. Electrical excitation is one of the most attractive methods for causing elastic deformation. The convenience and practicality of electrical stimulation and the recent advances in electroactive polymers (EAP) make them the most preferred among the responsive polymers. An added benefit of some of the EAP materials is their having the reverse effect of converting mechanical strain to electrical signal making them useful for sensors and energy harvesting mechanisms. To bring these materials to use in daily use products will necessitate finding niche that addresses critical needs. One of the main applications that are being considered for biologically inspired capabilities, also known as biomimetics, which were previously imaginable only in science fiction concepts. Some of the applications that are considered include Refreshable Braille Display, Robotic Fish, Fish-like Blimp, Humanlike Robots and many others. In the paper, the latest development in EAP materials and their applications will be reviewed and discussed.
FEM Stress Analyses of the Contact Stress Distributions at the Bearing Surfaces in Bolted Joints Using Hexagon Bolts With Flanges
Authors: Morozumi Yukio , Okumura Masahiko , Sawa Toshiyuki , Kuwaki Kengo
Published: May 2012

In designing bolted joints, it is important to understand the contact stress distribution and permanent set at the bearing surface in the case of high initial axial tension. They are investigated using elasto-plastic FEM for hexagon bolts with flange. It is found that the difference in the contact stress distribution is large between elastic FEM and elasto-plastic FEM. Effects of the flange thickness and the flange slope angle on the contact stress distribution and permanent set are examined, and it is shown that they are substantially influential. In the experiments, hollow cylindrical specimens are compressed by the bolts with flange and permanent sets are measured at the bearing surface. The permanent sets are compared with permanent sets obtained from the elasto-plastic FEM and they are in a fairly good agreement. In addition, the equivalent length for the hexagon bolt with flange is proposed.
One Train per Ventilation Zone: Application and Innovation
Authors: Colino Mark P. , Rosenstein Elena B.
Published: May 2012

In recognition of paragraph 7.2.5 of the National Fire Protection Association (NFPA) Standard 130 for Fixed Guideway and Passenger Rail Systems, a major commuter railroad project design team has undertaken detailed coordination of its train signaling, traction power and tunnel ventilation systems. Per the writing of the Standard, the coordination effort was aimed at designing the systems to match the total number of trains that could be between ventilation shafts during an emergency, but also recognized that, the best protection to passengers is to allow no more than one train in a ventilation zone. The coordination of the train signaling, traction power and tunnel ventilation system designs per NFPA 130 paragraphs 7.2.5 and A.7.2.5 has permitted the project to achieve a reasonable degree of safety from fire and its related hazards, while at the same time: preserving the commuter railroad’s throughput requirements; reducing overall construction costs; and, minimizing civic/environmental impacts. In particular, the design coordination has permitted the project to forego tunnel fan installations within existing structures in one portion of the project, and an innovative fan plant design between two tunnels has precluded the need for an additional tunnel ventilation shaft in another portion of the project.
Effects of Solder Wetting on Self-Alignment Accuracy and Modeling for Optoelectronics Assembly
Authors: Kong Ming , Jeon Sungeun , Hwang Chiwon , Lee Y. C.
Published: May 2012

Solder self-alignment is one of the most important technologies for cost effective optoelectronics assembly. In this study, the wetting of Sn-rich solder to the metal pads of chip and substrate was identified as a critical factor significantly affecting self-alignment accuracy during the assembly. Insufficient wetting of solder to the metallization pads was responsible for large chip-to-substrate misalignment post-assembly, while fabrication deviations, such as solder volume variation and pad diameter deviation, only account for misalignments in the range of submicrons. To aid the design of flip-chip assemblies requiring high alignment accuracy, a force optimization model was developed and validated experimentally. With the input parameters of design and manufacturing process for optoelectronics flip-chip assembly using solders, such as insufficient solder metallurgical wetting areas, positions and diameters of metallization pads, volume of individual solder bump, coefficient of solder surface tension, mass of chip, external forces acting on chip, and initial pick-and-place position of chip before assembly, the model predicts the assembled position of the chip in terms of the misalignments in the X-Y planes and the rotation angles along the Z axis. The model further confirmed that insufficient wetting of solder is the most critical modulator among the undesirable factors affecting solder self-alignment accuracy.
Numerical Study of Oil Slug Mobilization in a Capillary Tube
Authors: Zhang Yihe , Dai Liming , Luo Junya
Published: May 2012

This research investigates the effects of pore dimensions and smoothness on the mobilization of residual oil trapped inside pore structures. A model of water-filled uniform capillary tube with an oil slug trapped inside is employed as a simplified model for numerical simulation study. Pressure difference between two ends of the tube is being measured. The influence of the inner surface shape of the tube is mostly considered in this research. Based on the measurements of the capillary tubes used in experiments, a sine curved shape is employed to represent the inner surface of the capillary tube. Series of results have been obtained from the simulation. According to the results, the pressure difference required to mobilize the oil slug is inversely proportional to the smoothness of the tube inner surface shape.
Keeping Net Cash Flow Alive for a Petroleum Exploration Project: Risk Analysis Approach
Authors: Belhaj Hadi , Haroun Mohamad , Lay Terry
Published: May 2012

Meaningful risk analysis can be a tedious task to perform for many reasons, yet extremely rewarding. Lack of information, uncertainty surrounding risk parameters and their distributions, failure to define proper correlations relating some risk parameters, inappropriate selection of risk analysis criterion and misinterpretation of results are among these reasons. Risking net cash flow (NCF), through traditionally approaches can be a leap of faith. Rather, NCF should be treated with more subjectivity and in-depth understanding of all risk parameters and their interrelationships. Current practice of risk management in the petroleum industry adopts schemes that aim at separating risk into two main categories to understand, simplify, analyze, and evaluate existing contingencies. Commonly, the first category is referred to as subsurface risk that includes resource size, production rate, and access cost. Category two is surface risk that demonstrates total expenditure, facilities delivery, delays, performance, oil/gas prices, etc. Risk analysis of each is normally performed alone. Our study shows that separating risks for an investment with a singular outcome is misleading and extremely dangerous. In this paper, we introduce comprehensive criteria for handling risk associated with oil and gas exploration as well as development of mature reservoirs through EOR and IOR that involves large cash expenditures for; in-fill drilling, waterflooding, gas injection, and thermal and chemical treatment of heavy oil recovery. Basically, one or a combined uncertainty of these elements may create “business risk” that may cause “business impact”. The impact can be positive leading to “business opportunity” or negative leading to “business threat”. Also, instead of risking NCF using risk parameters like gross revenue that consists of hydrocarbon in-place and unit price of oil and gas, and net expenditure (CAPEX and OPEX) by simply defining their risk distributions and parameters, our approach breaks down each risk parameter to sub-parameters, then risk components and finally risk fragments. This produces a break-down model of risk analysis approach by including all parameters with no stage separation that avoids risk of poor assumptions. Hence, risk parameters are simplified by evaluating specific distributions. Case study involving one major Gulf States oil reservoirs is used to demonstrate the approach presented in this paper. Results show great improvement of results as compared to the traditionally used method.
Structural Analysis and Loads Distribution in Motorbike Forks During the Braking Phase
Authors: Croccolo D. , De Agostinis M. , Vincenzi N.
Published: May 2012

This work deals with the development of an analytical model, which allows to describe the tensile state arising in single-disc motorcycle suspensions, during the brake. Stress and strain trends are computed as functions of some key parameters of the motorcycle (mass and centre of gravity location) and of the fork (lengths and diameters). A portal frame loaded out of its plane represents the suspension geometry, whose axisymmetric elements represent the pillars (legs) and the wheel pin is the transverse beam. Each of the three elements has material and inertia parameters variable along its axis depending on the actual mechanical properties of the component. Finally, the stress field of several fork models has been investigated both via FEA and via in field tests, in order to support the effectiveness of the proposed model.
The Mechanics of Perturbed Upper Limb Movement Control
Authors: Chen Kai , Foulds Richard A.
Published: May 2012

The dependence of muscle force on muscle length gives rise to a “spring - like” behavior which has been shown to play an important role during movement. This study extended this concept and incorporated the influential factors of the mechanical behavior of the neural, muscular and skeletal system on the control of elbow movement. A significant question in motor control is determining how information about movement is used to modify control signals to achieve desired performance. One theory proposed and supported by Feldman et. is the equilibrium point hypothesis (EPH). In it the central nervous system (CNS) reacts to movement as a shift of the limb’s equilibrium posture. The EPH drastically simplified the requisite computations for multi-joint movements and mechanical interactions with complex dynamic objects in the context. Because the neuromuscular system is spring-like, the instantaneous difference between the arm’s actual position and the equilibrium position specified by the neural activity can generate the requisite torques, avoiding the complex “inverse dynamic” of computing the torques at the joints. Moreover, this instantaneous difference serves as a potential source of movement control related to limb dynamics and associated movement-dependent torques when perturbations are added. In this paper, we have used an EPH model to examine changes to control signals for arm movements in the context of adding perturbations in format of forces or torques. The mechanical properties and reflex actions of muscles crossing the elbow joint were examined during a planned 1 radian voluntary elbow flexion movement. Brief unexpected torque/force pulses of identical magnitude and time duration (4.5 N flexion switching to 50 N extension within 120ms) were introduced at various points of a movement in randomly selected trials. Single perturbation was implemented in different trials during early, mid, stages of the movement by pre-programmed 6DOF robotic arm (MOOG FCS HapticMaster). Changes in movement trajectory induced by a torque/ force perturbation determined over the first 120 ms by a position prediction formulation, and then a modified and optimization K-B-I (stiffness-damping-inertia) model was fit to the responses for predicting both non-perturbed and perturbed movement of elbow. The stiffness and damping coefficients estimate during voluntary movements were compared to values recorded of different subjects during trials. A least square nonlinear optimization model was designed to help determine the optimized impedance a subject could generate, and the identified of adapted of K-B-I in perturbed upper limb movements confirmed our assumption.
Finite Element Stress Analysis and Strength Evaluation of Bonded Shrink Fitted Joints Under Impact Push-Off Loads
Authors: Liao Lijuan , Sawa Toshiyuki
Published: May 2012

Joints combining shrink fittings with anaerobic adhesives (bonded shrink fitted joints) have been appeared with advantages compared with those with shrink fittings only in light weight and high strength. This paper deals with the stress wave propagations and stress distributions of bonded shrink fitted joint in which a hollow cylinder is fitted at the middle part of a solid cylinder subjected to impact push-off loads with small strain rate. The stress stress wave propagations and stress distributions in bonded shrink fitted joint are analyzed in elastic and elasto-plastic deformation ranges using finite element method (FEM) as a four-body contact problem. The impact loads are applied to the joint by dropping a weight-hammer. The FEM code employed is ANSYS/LS-DYNA. The effects of the stiffness, the outside diameter and the height of hollow cylinder on the stress wave propagations at the interfaces are examined. The strength of the joint is clarified using the stress distributions obtained from numerical calculations. The normal stress near the upper edge of the outside interface of the adhesive layer increases as the rigidity and the outside diameter of the hollow cylinder decrease and the height of the hollow cylinder increases. The shear stress near the upper edge of the outside surface of the adhesive layer increases as the outside diameter and the height of the hollow cylinder increase; while it decreases as the rigidity of the hollow cylinder increases. The strength of bonded shrink fitted joint increases as the rigidity and the height of the hollow cylinder increase and the outside diameter of the hollow cylinder decreases. In addition, the characteristics of the joints subjected to impact loads are compared with those of the joints under static loads. It is observed that the characteristics of the joints subjected to impact loads are opposite to those subjected to static loads. Besides that, the attributes of the contact interface of shrink fitted joint under impact loads are compared with those of bonded shrink fitted joint under same external loads. It is found that opposite properties exist between of them. Furthermore, experiments are carried out to measure the strain response of bonded shrink fitted joints subjected to impact push-off loads. The numerical results are in a fairly good agreement with the experimental results and FEM results.
Including Assembly Fixture Repeatability in Rigid and Non-Rigid Variation Simulation
Authors: Wa¨rmefjord Kristina , So¨derberg Rikard , Carlson Johan S.
Published: May 2012

The repeatability of the assembly fixtures influences the geometrical outcome of an assembly. To control the fixtures, capability studies are conducted. Those studies give however just information about the variability in a number of inspection points. In this paper, a method for transforming the variation in inspection data to variation in the contacts between workpiece and locators is described. By doing this, the fault localizing of the fixture is facilitated. Further, the accuracy of the variation simulations used to evaluate different concepts and designs can be improved. Usually, when data from a repeatability study are used as input to a variation simulation, the tolerances are only applied in the points that actually were inspected. The suggested methodology makes it possible to transform the tolerances containing the repeatability of the fixture to tolerances on the locating scheme, and they are thereby affecting every point in the simulation model, not only the inspected ones. The method is tested on a case study and the effect of including fixture repeatability in a variation simulation is investigated.
A Distributed and Distance Learning Course “Fluid Flows in Nature”
Authors: Schetz Joseph A.
Published: May 2012

This course was originally designed and conventionally taught to build upon and broaden a basic, traditional engineering knowledge of fluid flows into new and stimulating areas concerning a wide variety of natural occurrences and phenomena that involve fluid motions in important ways. Topics covered include: continuity and consequences in nature, drag of sessile systems and motile animals; gliding and soaring; flying and swimming; internal flows in organisms; low Reynolds number flows; fluid-fluid interfaces and stratified flows; unsteady flows in nature; atmospheric flows and wind engineering; and environmental fluid mechanics. The course is intended for upper-level students in engineering and science and presumes a background in the fundamentals of fluid flows at the level of a first engineering course in fluid mechanics. It proved popular with students majoring in mechanical, civil, aerospace and ocean engineering with occasional students from mathematics and sciences for a typical enrollment of 80–100 students. An unexpected, but welcome and powerful, benefit occurs in the form of reinforcing and deepening student understanding of traditional topics in engineering fluid mechanics by contrast with the often very different situations encountered in nature. An OnLine version of the course was introduced for the Spring Semester of 2006. Enrollment promptly and steadily increased to the point where 230 students registered in the Spring Semester of 2010. It is felt that a course of this type where conventional instructional materials do not exist is particularly suited to the OnLine format.
Dry Adhesion Based on Electrospun Polymer Nanofibers
Authors: Shi Qiang , Wong Shing-Chung , Wan Kai-Tak , Blackledge Todd A. , Najem John
Published: May 2012

Dry Adhesion exists between polymer nano/microfibers. An elaborate experiment was performed to directly measure the adhesion between electrospun poly(ε-caprolactone) (PCL) microfibers using a nano force tensile tester. Electrospun nano/microfibers with radius ranging from 0.2 to 1.1 μm were investigated. It was found that the adhesion force depended on the fiber radius following a linear relationship, which complied with the classical Johnson-Kendall-Roberts (JKR) contact mechanics model. The force increased with temperature and decreased with relative humidity between two fibers positioned in orthogonal directions. Our data suggested the van der Waals’ (vdW) interactions are primarily operative between the micro-/nano-fibers.
Determination of the Critical Length of a Subsurface Crack in a Monobloc R7T Railway Wheel Using FEM Analysis
Authors: Jafari A. , Alizadeh K. J.
Published: May 2012

Based on the endeavors have been made to reduce the wear rate of the railway wheels surfaces, and increase in the axle loads and the velocity of the trains, rolling contact fatigue of the railway wheels is nowadays a considerable damage with regard to the railway wheels. The initiated cracks in the wheels are classified into surface and subsurface ones. The former are usually removed by wear, while the latter propagate gradually until reaching the critical crack length and then suddenly bring about dangerous fractures. So, in any maintenance process of a railway system, it is essential to have the critical crack length as a vital tool to determine the possibility of the critical condition occurrence in the case of identified cracks in wheels. The critical crack length is a residential value and should be determined for any railway systems. So, by using FEM, this paper models an Iranian Railways wheel having the diameter of 920mm, made of R7T material which has a subsurface crack. The wheel is in contact with UIC60 rail. After analysis of this model, rang of stress intensity factor of the crack has been calculated for the different rotation angles. Finally, the critical length of a subsurface crack in conformity with Iranian Railways has been determined based on the fracture mechanics and some approximate relations about mechanical properties. Results show that because of geometrical limitations of the wheel, a subsurface crack can cause the wheel fracture before reaching the critical length.
Nanostructure Dependence of the Electronic Conductivity of Carbon Nanotubes and Graphene Sheets
Authors: Ohnishi Masato , Ohsaki Katsuya , Suzuki Yusuke , Suzuki Ken , Miura Hideo
Published: May 2012

In this study, the change of the resistivity of the CNT-dispersed resin was analyzed by applying a quantum chemical molecular dynamics and the first principle calculation. Various combinations of double-walled carbon nanotube structures were modeled for the analysis. The change of the band structure was calculated by changing the amplitude of the applied strain. It was found in some cases that the band structure changes drastically from a metallic structure to a semiconductive structure, and this result clearly indicated that the electronic conductivity of this MWCNT decreased significantly under tensile strain. It was also found that further application of the strain made a band gap in the band structure. This result indicated that the metallic CNT changes a semiconductive CNT due to the applied strain. The effect of the diameter of the zigzag type CNT on the critical strain of buckling deformation was analyzed under a uni-axial strain. In this analysis, the aspect ratio of each structure was fixed at 10. It was found that the critical strain decreased monotonically with the increase of the diameter. This was because that the flexural rigidity of a cylinder decreased with the increase of its diameter when the thickness of the wall of the cylinder is fixed. It was found that the critical strain decreased drastically from about 5% to 0.5% when the aspect ratio was changed from 10 to 30. Since the typical aspect ratio of CNTs often exceeds 1000, most CNTs show buckling deformation when an axial compressive strain was applied to the CNTs. Finally, the shape of six-membered ring of the CNT was found to be the dominant factor that determines the electronic band structure of a CNT. Next, the change of the band structure of a graphene sheet was analyzed by applying the abinitio calculation (Density functional theory). It was found that the fluctuation of the atomic distance among the six-membered ring is the most dominant factor of the electronic band structure. When the fluctuation exceeded about 10%, band gap appeared in the deformed six-membered ring, and thus, the electronic conductivity of the graphene sheet changes from metallic one to semiconductive one. It is therefore, possible to predict the change of the electronic conductivity of a CNT by considering the local shape of a six-membered ring in the deformed CNT.
High Temperature Damages of Ni-Base-Superalloy Caused by the Change of Nanotexture Due to Strain-Induced Anisotropic Diffusion
Authors: Sasaki Yamato , Itoh Hiroyuki , Murata Naokazu , Suzuki Ken , Miura Hideo
Published: May 2012

In order to assure the reliability of advanced gas turbine systems, it is very important to evaluate the damage of high temperature materials such as Ni-base superalloys under creep and fatigue conditions quantitatively. Since the micro texture of the gamma-prime (γ′) phase was found to vary during the creep damage process, it is possible, therefore, to evaluate the creep damage of this material quantitatively by measuring the change of the micro texture. The mechanism of the directional coarsening of γ′ phases (rafting) of Ni-base superalloy under an uni-axial strain at high temperatures was analyzed by molecular dynamics (MD) analysis. The stress-induced anisotropic diffusion of Al atoms perpendicular to the initially finely dispersed γ/γ′ interface in the superalloy crystal was observed clearly in a Ni(001)/Ni3Al(001) interface structure. The stress-induced anisotropic diffusion was validated by experiment using the stacked thin films structures which consisted of the (001) face-centered cubic (FCC) interface. The reduction of the diffusion of Al atoms perpendicular to the interface is thus, effective for improving the creep and fatigue resistance of the alloy. It was also found by MD analysis that the dopant elements in the superalloy also affected the strain-induced diffusion of Al atoms. Palladium was one of the most effective elements which restrain Al atoms from moving around the interface under the applied stress.
Analysis of Enhanced Heat Transfer on a Turbine Blade Tip-Wall With and Without Guide Ribs
Authors: Xie Gongnan , Sunde´n Bengt , Zhang Weihong , Utriainen Esa , Wang Lieke
Published: May 2012

Cooling methods are needed for gas turbine blade tips that are exposed to high temperature gas. A common way to cool the blade and its tip is to design serpentine passages with 180-deg turn under the blade tip-cap inside the turbine blade. Improved internal convective cooling is therefore required to increase the blade tip lifetime. This paper presents numerical predictions of turbulent heat transfer through two-pass channels with and without guide ribs (guide vanes) placed in the turn regions using RANS turbulence modeling. The effects of adding guide ribs on the tip-wall heat transfer enhancement and the channel pressure drop have been analyzed. The inlet Reynolds numbers are ranging from 100,000 to 600,000, and the rib cross-section blockage ratio (rib height to channel height, 2e/H) is 0.182. The detailed fluid flow and heat transfer over the tip-wall are presented. The overall performances of three two-pass channels are evaluated and compared. It is found that the tip heat transfer coefficients of the channels with guide ribs are 20%∼50% higher than that of a channel without guide ribs. The presence of guide ribs could lead to an increased (about 15%) or decreased (up to about 12%) pressure drop, depending upon the geometry and placement of guide ribs. It is suggested that the usage of guide ribs is a suitable way to improve the flow structure and augment the blade tip heat transfer, but is not the most effective way to augment tip-wall heat transfer compared to the augmentation by surface modifications imposed on the tip directly.
PIV Measurements of Cavitation Bubble Collapse Flow Induced by Pressure Wave
Authors: Yang Sheng-Hsueh , Jaw Shenq-Yuh , Yeh Keh-Chia
Published: May 2012

In this study, a single cavitation bubble is generated by rotating a U-tube filled with water. A series of bubble collapse flows induced by pressure waves of different strengths are investigated by positioning the cavitation bubble at different stand-off distances to a solid boundary. Particle images of bubble collapse flow recorded by high speed CCD camera are analyzed by multi-grid, iterative particle image distortion method. Detail velocity variations of the transient bubble collapse flow are obtained. It is found that a Kelvin–Helmholtz vortex is formed when a liquid jet penetrates the bubble surface. If the bubble center to the solid boundary is within one to three times of the bubble radius, the liquid jet is able to impinge the solid boundary to form a stagnation ring. The fluid inside the stagnation ring will be squeezed toward the center of the ring to form a counter jet. At certain critical position, the bubble collapse flow will produce a Kelvin–Helmholtz vortex, the Richtmyer-Meshkov instability, or the generation of a counter jet flow, depending on the strengths of the pressure waves. If the bubble surface is in contact with the solid boundary, the liquid jet can only splash inside-out without producing the stagnation ring and the counter jet. The complex phenomenon of cavitation bubble collapse flows is clearly manifested in this study.