bluuebunny/crossref_metadata_2025 huggingface dataset:
A Study of Subharmonic Excitation of Mechanically Coupled Microbeams for Filtration
Authors: Hammad Bashar K. , Nayfeh Ali H. , Abdel-Rahman Eihab M.
Published: August 2009

We study the feasibility of employing subharmonic resonance of order one-half to create a bandpass filter using two clamped-clamped microbeam resonators connected by a weak coupling beam. We discretize the distributed-parameter system using the Galerkin procedure to obtain a reduced-order model composed of two nonlinear coupled ODEs. It accounts for geometric and electric nonlinearities as well as the coupling between these two fields. Using the method of multiple scales, we determine four first-order nonlinear ODEs describing the amplitudes and phases of the modes. We use these equations to determine closed-form expressions for the static and dynamic deflections of the structure. The basis functions in the discretization are the linear undamped global mode shapes of the unactuated structure. We found that we can not produce a single-valued response for small excitation amplitudes. So that, it is impractical to use a single structure made of two mechanically coupled beams excited subharmonically in filtration. But we can use a pair of structures to build a bandpass filter by operating one in the softening domain and the other in the hardening domain and, more importantly, implementing processing logic and hardware schemes. However, the complications brought about by mechanically coupling of two microbeams can be avoided by using a pair of uncoupled beams. This makes the fabrication and modeling processes much easier. Using subharmonic excitation with mechanically uncoupled microbeams to realize bandpass filters is the subject of the next work.
Monitoring of the Machine Elements in Drilling Machine Using Vibration Signals by FEM
Authors: Naveen Prakash G. V. , Ravindra H. V.
Published: August 2009

Deterioration in the machine running conditions always produces a corresponding increase in the vibration level. By monitoring vibration level it is possible to obtain information about the machine condition. Here, drilling machine was considered for the analysis. Spindle bearings and gearbox are found to be the critical elements of the machine tools on which condition monitoring has to be concentrated. To analyze the condition of the existing machine elements, finite element method has been used. An attempt has been made by modeling drilling machine to find out the response of the structure for various defects in machine elements. The finite element model of the machine tool was developed by using finite element package ANSYS. Modal analysis has been carried out to determine the natural frequencies and mode shapes of the structure. Frequency response analysis was used to determine the response of the structure due to the unbalance forces. Transient response analysis was used to study the effect of assumed defects on the machine tool structure. A defect was assumed on the outer race of the spindle bearing and on the gear and responses were observed at the spindle bearings location. From the analysis for the assumed defect in the outer race of the bearing, it was observed that the vibration velocity increases with the increase in depth of defect and depends on location of the defect. From the vibration signature resulting due to assumed destructive pitting defect in all teeth of the driven gear, it was observed that the vibration velocity level decreases with increase in spindle speed. This is because, at lower speeds time taken by each tooth to mesh with its counterpart is more, and hence persistence of disturbing force due to defect in meshing gear is more at lower speeds. Experimentation was carried out on the drilling machine by using the instrument Machine Condition Tester T-30. The experimental data obtained were used to analyze the condition of the machine elements. The vibration velocity was measured on the spindle bearings location for different spindle speed. From the Experimental analysis it was observed that with the increase in spindle speed, the vibration velocity also increases. Finally, theoretical results were judged against the experimental results. Thus the present work shows that the FEM is a valuable tool in finding sources of undesirable vibrations from various defects present in the machine elements of the machine tool structure.
Nanomechanics of Silicon Nanowires via Symmetry-Adapted Tight-Binding and Classical Objective Molecular Dynamics
Authors: Dumitricaˇ Traian , Zhang Dong-Bo , Hua Ming
Published: August 2009

Stability and elastic response of the most promising ground state candidate Si nanowires with less than 10 nm in diameter are comparatively studied with objective molecular dynamics coupled with non-orthogonal tight-binding and classical potential models. The computationally-expensive tight-binding treatment becomes tractable due to the substantial simplifications introduced by the presented symmetry-adapted scheme. Quantitative differences regarding stability with the classical model description are noted. Using a Wulff energy decomposition approach it is revealed that these differences are caused by the inability of the classical potential to accurately describe the interaction of Si atoms on surfaces. Differences between the results of the two atomistic treatments are also noted in the elastic response in elongation.
Zero Dynamics Study of a Model Helicopter Considering the Effect of Control Point
Authors: Saffarian Mehdi , Fahimi Farbod
Published: August 2009

Zero dynamics of a helicopter system is modeled in this study with respect to the control point’s tracking path. The derivation is comprehensive and has been done for the most general flying maneuvers. The approach is based on a six Degree of Freedom (DoF) model of the helicopter’s body, the configuration of the aerodynamic traction, and the geometrical and inertial parameters of the helicopter. Considering the vast grows in the field of Autonomous Aerial Vehicle (UAV), this study can be utilized both for improving the design parameters of an aerial platform, deriving the feasible maneuvering scenarios and working regimes for available systems. Also, the study provides a platform to test the performance and stability of the control strategies for autonomous helicopter systems and other aerial vehicles.
Effect of Turbulator Width and Spacing on the Thermal Performance of Angled Ribs in a Rectangular Channel (AR = 3:1)
Authors: Wright Lesley M. , Gohardani Amir S.
Published: August 2009

The thermal performance is measured in a rectangular channel (AR = 3:1) with rib turbulators oriented at 45° to the mainstream flow. Ribs are placed on one of the wide walls, while heat transfer coefficients are also measured on a single smooth, narrow wall. The heat transfer enhancement is combined with the frictional losses to evaluate the benefit of turbulator width. Square ribs (w/e = 1) with a rib pitch–to–height (P/e) ratio of 8 serves as the baseline configuration. The rib width, w, is varied while the rib height, e, remains constant. Rib aspect ratios (w/e) of 1, 2, 3, and 4 are considered. In addition, the distance between the ribs is varied to consider the combined effect of rib width and rib spacing. As the width of the ribs is changing, the physical distance between the ribs, l, is varied, and four rib spacings are considered (l/e = 2.6, 6.6 [baseline corresponding to P/e = 8], 10.6, and 14.6). The thermal performance is measured in the 3:1 channel at Reynolds numbers of 10000, 30000, 50000, and 70000. Results indicate increasing the rib width is effective to increase the thermal performance of a cooling passage. However, the rib width and spacing must be varied in conjunction with one another to optimize the thermal performance.
Numerical and Experimental Study of Fire Whirl Generated in 15 × 15 Square Array Fires Placed in Cross Wind
Authors: Satoh Kohyu , Liu Naian , Liu Qiong , Yang K. T.
Published: August 2009

Fire whirls in large city fires and forest fires, which are highly dangerous and destructive, can cause substantial casualties and property damages. It is important to examine under what conditions of weather and geography such merging fires and fire whirls are generated. However, detailed physical characteristics about them are not fully clarified yet. Therefore, we have conducted preliminary studies about merging fires and swirling fires and found that they can enhance the fire spread. If sufficient knowledge can be obtained by relevant experiments and numerical computations, it may be possible to mitigate the damages due to merged fires and fire whirls. The objective of this study is to investigate the swirling conditions of fires in square arrays, applying wind at one corner, in laboratory experiments and also by CFD numerical simulations. Varying the inter-fire distance, heat release rate and mass flow rate by a wind fan, ‘swirling’ or ‘non-swirling’ in the array were judged. It has been found that the fire whirl generation is highly affected by the inter-fire distance in the array, the total heat release rate and also the mass flow rate by a fan. We obtained the conditions of swirling fire generation in 15 × 15 square array for (1) the ratio between the upward mass flow rate vs. applied mass flow rate in the upward swirling plume and (2) a non-dimensional relationship between the heat flow rate in the swirling plume and the applied mass flow rate.
Experimental Study of Inclination on Non-Boiling Regime Spray Cooling
Authors: Guo Yongxian , Jia Jianyuan , Wang Weidong , Zhou Shaorong
Published: August 2009

Based on the maximum CHF (critical heat flux) criterion, an optimal heat transfer criterion, which is called H criterion, was proposed. Experimental apparatuses were conducted. Distilled water was used as the working fluid. Three different DANFOSS nozzles with cone angles being 54°, 50° and 54° respectively were used. A 30×30mm2 square copper surface was used as the heated surface. Experimental results indicated that the volumetric fluxes were proportioned to P0.5, where P is the pressure drop across the nozzles. The optimal distance between the nozzles and the heated surface were derived. The results indicated that the optimal heat transfer appeared while the outside of the impellent thin spray film inscribed in the square heated surface. Based on the H criterion aforementioned, two DANFOSS nozzles of the three, with cone angles being 54° and 50° respectively, were used to study the temperature distribution of the heated surface while there were spray inclination angles during spray cooling experiments. Distilled water was also used impacting on the 30×30mm2 square copper surface aforementioned and a circular heated copper surface with diameters being 30mm respectively. The heat flux of the surface was kept in constant (about 26–35W/cm2). The inclination angles were 0°, 10°, 20°, 30°, 40° and 50° respectively. Three thermocouples imbedded in the heated surface were used to predict the grads of the temperature of the surface. Experimental results indicated that the temperature and the grads of the temperature of the surface increases first and then decreases with the increase of the inclination angle.
Modeling and Simulation of Push-Pull Type SMA Actuator System
Authors: Ren Bing-Yin
Published: August 2009

Shape Memory Alloy (SMA) actuators have broad application prospects in many fields, but due to the nonlinearity of inherent hysteresis of SMA, the precise position control has become the biggest obstacle for the wide application of SMA actuators in the fields of smart structures. Therefore, research on the control technology of push-pull type SMA actuators is rather important for extending the application of SMA actuators. A thermomechanical hysteresis model of push-pull type SMA actuators based on the one-dimensional constitutive laws developed by Tanaka-Liang et al. is presented. The Fuzzy-PID composite controller and the adaptive Fuzzy-tuned-PID controller are applied to the control of nonlinear hysteresis of push-pull type SMA actuators system. The movement characteristic and the control effect of push-pull type SMA actuators are simulated and the advantages and disadvantages of different controllers are analyzed. The results of simulation and analysis provide theoretical reference for the precise control of push-pull type SMA actuator systems.
A Measurement Method Using Bi-Metal Fixture for Non-Linear Property of Thin Layer Joint
Authors: Yamagiwa Masanori , Yu Qiang , Fujita Masato
Published: August 2009

Silicon Carbide Power (SiC) Devices which are operable under high temperature are focused, since the cooling system for the power modules can be miniaturized. In the conventional power devices, the thermal stress that is caused by the thermal expansion mismatch between the Si chip and the substrate can be absorbed by the deformation of solder joint. As a result, the thermal fatigue reliability of the conventional structures is secured. However, the solder materials cannot be used to mount the high temperature operable device like SiC because the operating temperature is higher than their melting temperature. In this study, a kind of Ag nanoparticle thin layer joint is proposed to the mount high temperature operable device. The feature of the Ag nanoparticle is to joint the chip on the substrate by low temperature sintering, and the melting point of the thin layer after mounting process is equal to the bulk Ag. To evaluate the reliability potential of proposed structure, the nonlinear material properties of the thin layer is required. However, it is difficult to measure these properties by the current method. Since it is considered the thin layer has different micro structure from that of the bulk Ag, and it is difficult to prepare a bulk specimen made of the Ag nanoparticle material. Therefore, it is necessary to measure the properties of Ag nanoparticle in the state of a thin layer. In this research, a new approach was proposed to measure the nonlinear properties in the state of thin layer by using a bi-metal fixture which is composed of two different materials whose CTEs are different. When the fixture is heated, micro displacement can be generated between two materials. The thin layer which is formed between the two metals in the fixture deformed in shear direction by the displacement. During the heating, the shear deformation of the thin layer is measured by a digital image correlation method. The load on the thin layer is measured by strain gauge attached at fixture. In this study, the nonlinear properties of Ag nanoparticle thin layer were measured by this method. In addition, properties of solder were measured by this method too as a reference, and the results were compared with the property of bulk solder to confirm the accuracy of the method using bi-metal fixture.
A New Design Concept of Highly-Loaded Axial Flow Compressor by Applying Boundary Layer Suction and 3D Blade Technique
Authors: Qiang Xiaoqing , Wang Songtao , Lin Weichun , Wang Zhongqi
Published: August 2009

A new design concept of highly-loaded axial flow compressor by applying boundary layer suction and 3D blade technique was proposed in this paper. The basic idea of this design concept was that low reaction was adopted as while as increasing the rotor’s geometry turning angle, so that the boundary layer separation of a rotor could be eliminated and the rotor was kept working in high efficiency. This design concept would greatly increase the stator’s geometry turning angle, so boundary layer suction on stator cascades was adopted in order to restrain the boundary layer separation. In some situations, 3D blade technique was also applied in order to control the boundary layer separation more efficiently. The advantages of the above design concept were: the compressor’s pressure ratio was increased remarkably; boundary layer suction was only adopted in stator cascades so as to reduce the complexity of boundary layer suction structure. The key techniques of the new design concept were also explained in this paper. In order to increase the compressor’s pressure ratio, the geometry turning angle of rotor was increased greatly, and the rotor inlet was prewhirled to reduce the rotor’s reaction so as to restrain the rotor’s boundary separation. Boundary layer suction was carried out in the stator cascades (mainly on suction side), hub and shroud in order to control the flow separation. 3D blade technique could be adopted if necessary. The limitation of the application of this design concept was also pointed out through the analysis of the Mach number at rotor inlet, the prewhirl angle of rotor, the work distribution along span wise and the control method of stator separation. Numerical simulation was carried out on a single low-reaction compressor stage with IGV in order to demonstrate the new design concept. By using boundary layer suction and 3D blade technique, the energy loss in stator cascades was greatly reduced and the whole stage’s isentropic efficiency was about 90%. The low-reaction stage’s aerodynamic load was double than conventional design. The boundary layer separation could be effectively controlled by proper combination of boundary layer suction and bowed or twisted blade. The numerical result proved that the new design concept was feasible and had a wide application area.
Stability of Self-Assembled Monolayers on Gold for MEMS/NEMS Applications
Authors: Ang X. F. , Lin A. T. , Li J. , Wei J. , Chen Z. , Wong C. C.
Published: August 2009

Stability of self-assembled monolayers on gold under various environmental conditions is a crucial component in many biological, chemical and mechanical surface-functionalizations. In this study, we investigate the effects of relative humidity, ambient conditions (air, nitrogen-purged) and temperature on the structural stability of alkanethiols on gold at different chain length using contact angle measurements and time-of-flight secondary ions mass spectroscopy (TOF-SIMS). The ability of self-assembled monolayers functioning under these conditions is critical in protecting gold metal surfaces especially, from surface contamination. This in turn, affects the bonding conditions required in wafer level bonding process which is a key fabrication step in microelectromechanical (MEMs) and nanoelectromechanical (NEMs) systems. Such findings are particularly important in bioMEMs or bioNEMs since gold is one of the most common microfabrication material used in MEMs drug delivery devices due to its superior biocompatibility and reduced biofouling.
Fast Multiphysics MEMS Simulation With Arnoldi Model Order Reduction
Authors: Binion David , Chen Xiaolin
Published: August 2009

Modeling and simulation of Micro Electro Mechanical Systems has become increasingly important as the complexity of MEMS devices increases. In particular, thermal effects on MEMS devices has become a growing topic of interest. Through the FEA, detailed solutions can be obtained to investigate the multiphysics coupling and the transient behavior of a MEMS device at the component level. For system-level integration and simulation, the FEA discretization often results in large full-scale models, which can be computationally demanding or even prohibitive to solve. Model order reduction (MOR) was investigated in this study to reduce problem size for complex dynamic system modeling. The Arnoldi method was implemented for MOR to improve the computational efficiency while preserving the input-output behavior of coupled MEMS simulation. Using this method, a low dimensional Krylov subspace was extracted from the full-scale system model. Reduced order solution of the transient temperature distributions was then determined by projecting the system onto the extracted Krylov subspace and solving the reduced system. An electro thermal MEMS actuator was studied for various inputs. To compare results, the full-scale analyses were performed using the commercial FEA program ANSYS. It was found that the computational time of MOR was only a fraction of the full-scale solution time, with the relative errors ranging from 1.1% to 4.5% at different positions on the actuator. Our results show that the reduced order modeling via Alnoldi can significantly decrease the transient analysis solution time without much loss in accuracy for coupled-field MEMS simulation.
Detecting Stable-Unstable Nonlinear Invariant Manifold and Homoclinic Orbits in Mechanical Systems
Authors: Lenci Stefano , Rega Giuseppe
Published: August 2009

We consider a four dimensional Hamiltonian system representing the reduced-order (two-mode) dynamics of a buckled beam. The system has a saddle-center equilibrium point, and we pay attention to the existence and detection of the stable-unstable nonlinear manifold and of homoclinic solutions, which are the sources of complex and chaotic dynamics observed in the system response. The system has also a coupling nonlinear parameter, which depends on the boundary conditions, and is zero, e.g., for the hinged-hinged beam and different from zero, e.g., for the fixed-fixed beam. The invariant manifold in the latter case is detected assuming that it can be represented as a graph over the plane spanned by the unstable (principal) variable and its velocity. We show by a series solution that the manifold exists but has a limited extension, not sufficient for the deployment of the homoclinic orbit. Thus, the homoclinic orbit is addressed directly, irrespective of its belonging to the invariant manifold. By means of the perturbation method it is shown that it exists only on some curves of the governing parameters space, which branch from a fundamental path. This shows that the homoclinic orbit is not generic. These results have been confirmed by numerical simulations and by a different analytical technique.
Intelligence and Constant Flow: Small Flow Piston Pump Based on Linear Expansion of Thermosensitive Materials and Area Effect Stroke Amplifying Mechanism
Authors: Su D. N. , Zhong K. M.
Published: August 2009

This paper elaborates on a small flow piston pump without high speed prime mover and intermediate mechanism. The pump is based on the thermal expansion and contraction property of many materials and quick cool-to-heat change technology of semiconductors. The minim linear elongation or contraction of the thermosensitive material, after an amplification of about 50 times by the area effect stroke amplifying mechanism based on the principle of fluid drive, is transformed into low reciprocating linear movement of the piston to realize the volumetric change needed by the pump. This new small flow piston pump has the following prominent strengths: (1) The structure of pump is very simple; (2) No noise pollution is generated absent of mechanism moving at a high speed; (3) It is very easy to seal the pump because of less joints of possible oil fluid leakage; (4) At any time, there is only one piston which is outputting oil fluid at a low speed, so it is very easy to make a small or micro flow pump; (5) Constant flow oil fluid can be output by parallelizing two pumps which are brought under intelligent control.
The Ultimate Experience in Learning Robotics: Building Robots in a Robotics Course
Authors: Barakat Nael
Published: August 2009

Most engineering schools currently include a curriculum component that introduces students to the field of robotics. Multiple methods and techniques are used by engineering educators to help students gain familiarity and interest in robotic systems and their applications. However, very rarely the students get the opportunity to gain the ultimate experience of applying acquired knowledge of the field through building an actual robot. This is because building a robot during a college course involves multiple challenges including robotic systems high complexity and the requirement of combining multiple knowledge bases. Students studying robotics end up, at the most, programming purchased robots, or simulating robots using software, but not actually going through the realities and challenges of putting the system together and making it functional to the point of experimenting with it. In this paper, a unique experience in learning robotic systems and building actual robots is presented. This experience is made available in an elective course on robotic systems engineering at Grand Valley State University (GVSU), School of Engineering (SOE). The produced robots are two or three jointed arm configuration robots, controlled by a programmable microcontroller and built based on classroom gained knowledge. In the classroom, the students learn the kinematics and simplified dynamics of robots, as well as other related topics. In the laboratory, the students are required to apply the learned concepts of kinematics and design in combination with control systems to build a robot that will help them understand and demonstrate these concepts. The course final projects include robotic systems that are built or integrated by teams of students. These projects provide a range of challenges that extends from mechanical design to control systems. The projects are taken up by teams of students having diversified interests and skill bases within the course. The final outcomes of the course are working robotic systems that can demonstrate the students’ knowledge and interest, which the students use significantly as a proof of their competence level when putting together their resumes to move into the next level of their careers. From an educational angle, the course provides the students with an opportunity to combine multiple knowledge sets, skills, and interest to gain the ultimate experience in education: producing a functional system to specifications.
Investigation of Vibration in Wet Clutch Systems With Paper-Based Friction Materials
Authors: Matsuo Masashi , Shiraishi Toshihiko , Morishita Shin , Sambongi Yuzuru
Published: August 2009

Friction has been made use of in various kinds of mechanical systems and sometimes induces unexpected vibration or noise such as “shudder” in clutch systems and “squeal” in brake systems in automobile applications. The studies to decrease vibration in wet friction have been performed mainly in the tribology field by developing lubricants filling sliding surfaces. Although the development of appropriate lubricants is very effective prevention of friction vibration, it may occur due to degradation of lubricants and be amplified according to structure of clutch systems. In addition, even a little vibration energy can induce loud noise when it transmits to thin elements in clutch systems and modes of out-of-plane vibration predominantly comes out. There are not so many studies of vibration in the structure of clutch systems as brake systems. In this paper, vibration in wet friction systems with paper-based materials as seen in wet clutches in automatic transmissions was investigated theoretically and experimentally. The experimental setup was designed simply and essentially in order to investigate vibration phenomena themselves due to friction on sliding surfaces filled with a lubricant. The experiments were conducted in detail under various conditions of lubricating oils, surface velocities and normal loads. It was shown that the vibration phenomena in this wet friction system depended greatly on the relationship of the friction force to the relative velocity characterizing lubricating oils. It was suggested that the vibration phenomena could be classified using the relationship of the relative velocity between the sliding surfaces to the surface velocity of one sliding surface. In addition, the actual vibration phenomena according to the actual structure of wet clutch system were investigated by modal analysis using a finite element method. As a result, some of the modes and natural frequencies to likely lead to noise were shown.
Finite Element Simulation of the Self-Piercing Riveting Process
Authors: Qu S. G. , Deng W. J.
Published: August 2009

This work is focused on the development of a numerical model with the help of the finite element method to predict the magnitude and distribution of deformation associated with the self-piercing riveting process. A 2D axisymmetric model of the self-piercing riveting process is presented using the commercial implicit finite element code MSC.Superform. The flow stress of the work-material is taken as a function of strain, strain-rate and temperature. The shape of the rivet joint and the stress, strain and damage in both of the rivet and workpiece sheets are determined. The information obtained from the process simulation, such as force, metal flow and details of die fill are discussed. The calculated punching forces and the shape of the rivet joint are compared with experimental data and found to be in good agreement. Defects in the riveting are analyzed and are categorized into penetration, necking and lap formation. The effects of workpiece temperature on punching force were also discussed.
Improved Robustness Through Closed-Loop Control for Aluminum Sheet Metal Stamp Forming
Authors: Emblom William J. , Weinmann Klaus J.
Published: August 2009

A stamp forming die, whose flexible blank holder was designed using FEA, was built. Tests were performed to evaluate the robustness of the die once closed-loop control was implemented. These results were compared to the results of open-loop tests presented earlier. The closed-loop tests were designed to determine the die and control system’s ability to reject process disturbances and demonstrate improved robustness in stamp forming when using a flexible blank holder and closed-loop control. Draw beads were used to control local punch forces and blank holder forces were used to control wrinkling. Experimental tests for the die demonstrated that closed-loop control of local punch forces using active draw beads improves robustness of the die. Two different lubricants and varying quantities of lubricant were evaluated for this study. Additionally, the ability to simultaneously use draw bead height to control local punch force and blank holder force to control wrinkles was demonstrated.
Influence of Patch Boundary Condition on the Vibration Characteristic of an Agricultural Tire
Authors: Fujita Katsuhide , Saito Takashi , Kaneko Mitsugu
Published: August 2009

Though it is well known that the vibration and the noise of agricultural machinery during running on a road are strongly influenced by the tire lug form, few studies have been carried out to clarify this mechanism, while many studies were done on the characteristics of automobile tire. In the previous studies for automobile tire, the tire is typically modeled as a thin, cylindrical beam on a continuously distributed elastic foundation representing the sidewall stiffness. However, this model cannot be directly applied to agricultural tire, because of non-uniform stiffness effect caused by tire lugs. In this research, natural frequencies and mode shapes of a non-rotating agricultural tire are assessed by the experimental modal analysis method for two boundary conditions: without the ground contact and with the ground contact. Then, the tire is modeled as a thin, cylindrical beam with multiple radial spring attachments, which represent tire lugs with non-uniform radial stiffness. A calculation procedure based on the receptance method for obtaining the natural frequencies of tire is formulated, then applied to the said two boundary conditions. Furthermore, the fundamental parameters of tire are identified from the measured natural frequencies using Downhill Simplex method. As a result, the influence of boundary conditions on the parameter is clarified.
Lead-Free, Fluxless Solder Joints to Synthetic Diamond
Authors: Kam Pascal , Coppage Aaron , Kam Calvin , Shafian Sharin , Chun Bong Steven , Rhee Jinny
Published: August 2009

With the recent trends towards smaller heat sources and higher heat fluxes, conduction spreading resistance can become a bottleneck to efficient heat dissipation from temperature-sensitive components such as advanced microelectronics and high power light-emitting diodes (LEDs). However, the use of a high thermal conductivity heat spreader such as a synthetic chemically vapor deposited (CVD) diamond results in an additional interface between two materials. The near elimination of thermal interface resistance at material boundaries is critical for this application to be viable from a thermal standpoint. A lead-free, fluxless soldering process for joining metal substrates to a CVD diamond heat spreader was sought in this study to achieve the low thermal interface resistance and Restruction of Hazardous Substances Directive (RoHS) compliancy desired for this application. A typical titanium-platinum-gold metallization was applied to the surfaces of the diamond to enable it to bond with metal solders. Both indium solder and a popular tin-silver-copper solder (SAC305) were examined in this work. The indium was cold-welded to the substrates under pressure. The SAC305 solder was reflowed in a nitrogen furnace with variable pressure at the joint. The resulting solder thicknesses and joint quality were assessed using a scanning electron microscope (SEM). Lastly, a prototype of high-heat flux source with a CVD diamond spreader and forced convection with air was built to illustrate the thermal advantages of properly incorporating a diamond spreader with a fluxless solder bond.
Numerical Study on Ventilation Effect in Complex Enclosed Structure
Authors: Kim Chul Hwan , Yoo Geun Jong , Choi Hoon Ki
Published: August 2009

Boiler building in power plant includes various types of different equipments. These equipments can be boiler itself and others delivering energy which are acting as heat sources. Moreover, complex piping system to deliver hot steam to turbine and other auxiliary components add additional heat sources and make internal arrangement even more complex. In this study, ventilation analysis is performed to find proper location of openings such as louvers and windows, which ensures desired heat transfer. Various openings provide air passage to reduce stagnation area of high temperature inside enclosed structure. Ventilation analysis is applied to entire internal space of the enclosed structure with standard k-ε model. Opening size of the louver determines amount of air flow which gives direct cooling effect. Different combinations of the louver locations are studied together with size variations to find optimum condition for better ventilation. The location of louver is found as important factor in the ventilation effect. Vertical location change, especially, results enhanced cooling effect which provides effective passive design concept. The opening size of louver is found to have proportional effect on cooling. From the analysis, it is also found that high local temperature can be removed effectively by lowering upper louver location.
Influence in Lubricant Oxidation in Wear of Metallic Surfaces
Authors: Hilerio Isaias , Jimenez Homero , Vazquez Benjamin
Published: August 2009

The lubricants are certain type of substances that are applied to the contact surfaces of machines to reduce friction among the mobile parts. This friction originates a heating in pieces and wear of superficial layers. This heating produces a bad operation in parts of machines. So, lubricant protects the metallic surfaces against the action of the corrosive agents. The main part of this work consists on determining as the oxidation of lubricant influences in rubbing of the pieces and its relationship with the produced wear and their results are better in operations normal conditions when is compared when the lubricant is oxidized. The lubricant can be natural or synthetic. Among the natural lubricants it is possible to mention organic oils and minerals, fats or graphite. Among synthetic lubricants are silicones and special products able to support very high temperatures as those characteristic of advanced motors diesel. They can be coatings that allow to the mobile parts to be lubricated itself, or oils degraded without produce traces after rubbing.
Quantification of Arterial Stiffness Reduced Effect of Vessel Geometry
Authors: Ota Shinichiro , Yasuda Toshitaka , Saito Takashi
Published: August 2009

Arteriosclerosis is such as phenomena hardening of arteries, with thickening and loss of elasticity. Previous indexes include effect of geometric and mechanical factors as the radius, the wall thickness and mechanical properties of arteries. In this study, we proposed viscoelasticity indexes formulated by thin cylindrical shell theory estimated dynamic strain, and this index was independent of wall thickness and radius of arterial vessels. To confirm the validity of these indexes, we evaluated the parameters of viscoelasticity using the latex tube with different wall thickness of blood vessel model. We measured a radius of the latex tube and an inner pressure maintained by a pulsatile pump in a mock circuit filled with the water. Estimating the parameters of elasticity using these measured values, we concluded that a proposal index was independent of the wall thickness of the artery.
A New Stable Operating Regime for Oxyfuel Combustion
Authors: Seepana Sivaji , Jayanti Sreenivas
Published: August 2009

In the present paper, the stability of the new oxyfuel combustion regime titled as Intermediate temperature Diluted Oxygen Combustion (INDOCS) has been demonstrated theoretically. The operating conditions for the INDOCS are different from those of conventional oxyfuel combustion: the concentration by mass of oxygen in the oxidant stream is between 16 to 20% by mass (as opposed to 24% by mass in conventional oxyfuel combustion) and the temperature of the oxidant at entry to the furnace is in the range of 600 to 850 K (as opposed to an ambient temperature of about 300 K in conventional oxyfuel combustion). The method relies on the well-established fact that the stability of the flame increases with preheating of the oxidant (as demonstrated in High Temperature Air Combustion (HITAC) and FLAMELESS combustion regimes). The attendant high peak temperature of the flame can be reduced, to minimize NOx formation, by diluting the oxygen concentration. The overall benefits of this method are stable combustion at diluted oxygen concentrations, lower NOx (if N2 is present due to incomplete separation of oxygen from air), higher concentration of carbondioxide in the flue gases for a more efficient carbon sequestration. Flame structure calculations using the flamelet model of combustion with 35-step methane-air simplified reaction mechanism are used to demonstrate the stability of the flame. Simulations have also been carried out for the geometry of the 300 kW IFRF burner test facility; these show that the decreasing concentration of H and OH radicals in the quarl zone with increasing dilution by CO2 is counteracted by increasing the temperature of the oxidant. One of the principal advantages of this method is that, unlike in the case of HiTAC, the preheat requirements are mild which can be achieved by mixing part of the flue gas with the oxygen separated from air. It can be therefore readily implemented as a retrofitting measure in existing coal-fired plants.
Study on Design Support Method Considering the Interaction Among Multi-Variables
Authors: Noda Junya , Yu Qiang
Published: August 2009

Recently, a remarkable shortening of the development and design period becomes possible by the development of CAE and the optimization technologies, and efficient improvement of design quality in the detailed design stage has been achieved. Nevertheless, it is thought that there is a limit to for this kind of improvement in the near future, no matter how much the upgrade of the detailed design stage will be attempted. Therefore, the technology requested in the next step should be a new approach that can improve the quality of design concept and the efficiency of the concept design processes. For the engineers to improve concept design efficiency, they are requested that they should have very good understanding about the physics of their objectives and special experience about know-how for forming the answers to a very complicated problems. Thus, it is necessary to know the complicated physical relation between the design factors and the evaluation characteristic values to upgrade the concept design stage. It is thought that it can make a further improvement on the efficiency of design process if the technique, which can help the engineers to grip this relation, is established. However, it is very difficult for the engineers to understand a real complicated problem by few experiences. There are a lot of reasons for this kind of problems. For example, there will be a various patterns of design factors that achieve the similar design results, if the design factors have strong interacting relation between each other. In this study, the authors proposed a design support method for extracting the relation between the design factors and the evaluation characteristic values by using the results obtained by simulation models, and it was applied to the vehicle design problems in considering the interaction among the multi-variables by using a hierarchical cluster analysis and a graphical model. It was shown that the results given by the proposed approach can help the engineers to find and understand the essence of the phenomena involved.
Design of Angular Position Control System for Fluid Drive Motor
Authors: Nakao Yohichi , Ishikawa Masanori
Published: August 2009

This paper describes the angular position control system for a fluid drive motor. The fluid drive motor has a similar driving principle with the fluid drive spindle that is designed for the spindle of precision machine tools. The fluid drive motor is driven by the water or oil flow power. In the present paper, the rotational speed controller is first discussed. In order to reduce the influence of external load torque on the rotational speed, a conventional disturbance observer is combined with the rotational speed control system. The angular position control system, which possesses the rotational speed controller as a minor feedback loop, is then discussed. Performances of the designed angular position control system are studied via simulations and experiments. It is verified that the influence of the external load torque on the rotational speed is successfully compensated. The angular position control system is tested through simulations and experiments, as well. Experimental result shows the designed angular position control system suppresses steady state positioning error less than 0.02 degree, even if external constant load torque acts on the motor.
Poiseuille Number Correlations of Gas Flow in Concentric Micro Annular Tubes
Authors: Hong Chungpyo , Asako Yutaka , Suzuki Koichi
Published: August 2009

Poiseuille number, the product of friction factor and Reynolds number (f · Re) for quasi-fully developed concentric micro annular tube flow was obtained for both no-slip and slip boundary conditions. The numerical methodology is based on the Arbitrary-Lagrangian-Eulerian (ALE) method. The compressible momentum and energy equations were solved for a wide range of Reynolds and Mach numbers for both isothermal flow and no heat conduction flow conditions. The detail of the incompressible slip Poiseuille number is kindly documented and its value defined as a function of r* and Kn is represented. The outer tube radius ranges from 50 to 150μm with the radius ratios of 0.2, 0.5 and 0.8 and selected tube length is 0.02m. The stagnation pressure, pstg is chosen in such away that the exit Mach number ranges from 0.1 to 0.7. The outlet pressure is fixed at the atmospheric pressure. In the case of fast flow, the value of f · Re is higher than that of incompressible slip flow theory due to the compressibility effect. However in the case of slow flow the value of f · Re is slightly lower than that of incompressible slip flow due to the rarefaction effect, even the flow is accelerated. The value of f · Re obtained for no-slip boundary conditions is compared with that of obtained for slip boundary conditions. The values of f · Re obtained for slip boundary conditions are predicted by f · Re correlations obtained for no-slip boundary conditions since rarefaction effect is relatively small for the fast flow.
Design of CNG Tank Supports on Vehicle for Crash Test Simulation
Authors: Asadi Garmaroudi M. , Mosayebi J. , Hojabri F.
Published: August 2009

Typical structural members in the automotive body have complex geometrical shapes and no standard size. Thus, generating crash behavior database for all possible dimensions of even single shape is an extremely expensive task. A remedy is to generate databases containing relatively few sizes of the structural members, then employ different methods to approximate the behavior of the structural members over the complete design domain of the dimensions. This paper simulates the behavior of the CNG tank and structural members to crash conditions by using Finite Element Method. According to standard ISO15500, these conditions are acceleration with: i)± 20g longitudinal direction, ii) ± 8g side direction and iii) 4.5g vertical direction [1]. Then, experimental tests were done to validate theoretical results.
Brownian Dynamics Simulations of Sedimentation Phenomena of Ferromagnetic Spherical Particles in a Colloidal Dispersion
Authors: Hayasaka Ryo , Satoh Akira
Published: August 2009

We have investigated sedimentation phenomena of a colloidal dispersion composed of ferromagnetic spherical particles in the gravity field, by means of Brownian dynamics simulations. In concrete, we have attempted to clarify the influences of the magnetic field strength, magnetic interactions between particles and volumetric fraction of particles on sedimentation phenomena of such magnetic particles. In order to discuss quantitatively the sedimentation process and the internal structures of particle aggregates after the sedimentation, we have concentrated our attention on the local radial distribution function of each layer. The main results obtained here are summarized as follows. For the case of a weak magnetic field and a weak magnetic force between particles, layered structures are formed. As the magnetic field increases, clusters are formed in upright formation along the gravity or the magnetic field direction. As magnetic particle-particle interactions increase, particles combine with each other to form aggregate in other directions, and new types of clusters are formed in the bottom area. In this situation, therefore, the upright-standing clusters come to disappear. For a dilute case, relatively small clusters are formed apart from each other in almost equal space. As the volumetric fraction increases from such a situation, clusters with voids in the center area of the clusters come to be observed, but such formation disappears and layered structures are formed with further increasing the volumetric fraction.
Influence of Slug Flow on Hydraulic Sand Dune Migration in Horizontal Pipelines
Authors: Goharzadeh Afshin , Rodgers Peter , Touati Chokri
Published: August 2009

This paper presents an experimental study of three phase flows (air-water-sand) inside a horizontal pipe. The results obtained aim to enhance the fundamental understanding of sand transportation due to saltation in the presence of slug flow. Sand dune pitch, height and front velocity were measured using high-speed video photography. Four flow compositions with differing gas ratios, including hydraulic conveying, were assessed for sand transportation, having the same mixture velocity. For the test conditions under analysis, it was found that the gas ratio did not affect the average dune front velocity. However, for slug flows, the sand bed was transported further downstream relative to hydraulic conveying. It was also observed that the slug body significantly influences sand particle mobility. The physical mechanism of sand transportation was found to be discontinuous with slug flows. The sand dune local velocity (inside the slug body) was measured to be three times higher than the averaged dune velocities.