bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Analysis of Nonlinear Control Systems Using Singular Value Decomposition: Part II — Control of an Input-Constrained Thermal Process
Authors: Gwak Kwan-Woong , Masada Glenn Y.
Published: May 2008

In a Part I (Structural Analysis of Nonlinear Control System using Singular Value Decomposition: Part I—Approach), structural analysis algorithms for nonlinear control systems were developed applying singular value decomposition (SVD) on the linear algebraic equivalence of the nonlinear controller. In this paper, the proposed algorithms are applied to the temperature control of a thermal system which has control input constraints. Control input/output modes, weights of linear mode combination, colinearity, and mode truncation concepts introduced in Part I, are used to analyze and find the cause of input-constraint-violating-control of the nonlinear controller designed for the thermal system and to redesign the nonlinear controller to satisfy the input constraints and to reduce control effort.
Heat-Mass Transfer in Large Cell Suspensions (Cells in a Ternary Cryopreservation Medium: Water-NaCl-DMSO) During the Freezing Process
Authors: Luo Dawei , Gao Dayong , He Liqun , Cheng Shuxia
Published: May 2008

In this research, continuum theory (macroscopic enthalpy model) for multi-component phase change was applied to study the freezing process of bulk sample (cell suspension in a flat blood bag), coupled with the investigation of microscopic mass transfer across cell membrane. Numerical simulation results indicated that distributions of temperature and solute concentration inside the sample are not uniform during the cooling process. As a consequence, the degrees of cell dehydration are different at various locations.
Sensitivity Studies for the Shallow-Pocket Geometry of a Hydrostatic Thrust Bearing
Authors: Johnson Robert E. , Manring Noah D.
Published: May 2008

Hydrostatic thrust bearings have been the object of considerable research for many years. The attention that these bearings have received is primarily due to the important role they play in the design and operation of heavy equipment. In this role, the hydrostatic thrust bearing is often considered to be the “Achilles heel” of the total machine system as failures result in catastrophic difficulties and expensive repairs. The objectives of this research are to examine the nuances of designing a hydorstatic thrust bearing using a shallow pocket as opposed to the more traditional deep pocket design. By using a two-dimensional model for this geometry, the basic features of the shallow pocket design are extracted in closed-form and behaviors that would be expected in the three-dimensional setting are identified. In this research, a single dimensionless parameter is used to describe the influence of the bearing speed under laminar flow conditions. The principal results of this research are closed-form expression that describe the load carrying capcity of the bearing, the tilting moment exerted on the bearing by a skewed pressure distribution, and the volumetric leakage of the bearing. Sensitivity studies are conducted using these results and the influence of small perturbations of the pocket depth are identified for bearings with different pocket widths. These results are discussed and conclusions are itemized in the final section of the paper.
Electrothermal Liquid Motion in Microsystems Subjected to Alternating and Rotating Electric Fields
Authors: Gonza´lez Antonio , Ramos Antonio , Castellanos Antonio , Morgan Hywel , Green Nicolas G.
Published: May 2008

Electrothermal motion in an aqueous solution appears when an electric field is coupled with thermally-induced gradients of conductivity and permittivity in the fluid. The temperature field can be produced by external sources, such as strong illumination, or caused by the applied electric field through Joule heating. Electrothermal flow in microsystems is usually important at frequencies around 1 MHz and voltages around. 10 V. In this work, we consider first the two-dimensional problem of an aqueous solution placed on top of two co-planar electrodes that are subjected to an ac potenfial difference when there is either a vertical or horizontal temperature gradient. Secondly, we study the three-dimensional problem of an aqueous solution lying on four co-planar electrodes which produce a rotating field. This electric field when combined with a vertical temperature gradient rotates the liquid. The resulting electric field an liquid motion in these problems are characterised using self-similar solutions. Finally, these analytical solutions are compared with numerical and experimental results.
Nondimensional Analysis of Electrorheological and Magnetorheological Dampers Using a Herschel-Bulkley Constitutive Model
Authors: Wereley Norman M.
Published: May 2008

Quasisteady modeling of linear stroke flow mode magnetorheological (MR) and electrorheological (ER) dampers has focused primarily on the utilization of the Bingham-plastic constitutive model to assess performance metrics such as damping capacity. In such Bingham-plastic MR (or ER) flows, the yield stress of the fluid, τy, is activated by applying magnetic (or electric) field. The Bingham-plastic model assumes that the material is in either (1) a preyield condition where the local shear stress is less than the yield stress, τ < τy, or (2) a postyield condition, where the local shear stress is greater than the yield stress, τ > τy, so that the material flows with a constant postyield viscosity. The objective of this paper is to analyze the damping capacity of such a controllable MR or ER damper in the situation when the field dependent fluid exhibits postyield shear thinning or thickening behavior, that is, the postyield viscosity is a function of shear rate. A Herschel-Bulkley model with a field dependent yield stress is proposed, and the impact of shear rate dependent viscosity on damping capacity is assessed. Key analysis results—velocity profile, shear stress profile, and damping coefficient—are presented in a nondimensional formulation that is consistent with prior results for the Bingham-plastic analysis. The nondimensional analysis formulated here clearly establishes the Bingham number as the independent variable for assessing flow mode damper performance.
Function-Oriented Material Design for Next-Generation Ground Vehicles
Authors: Ma Zheng-Dong , Wang Hui , Kikuchi Noboru , Pierre Christophe , Raju Basavaraju
Published: May 2008

A systematic approach, referred to as function-oriented material design (FOMD), is presented in this paper, which can be used to design materials for the specific tasks demanded of structures in future ground vehicle systems. In order to carry out the FOMD process, first the functions of a structure in the vehicle system need to be explicitly defined in a systematic way. Then these functions must be quantified, so as to define the objective and constraint functions in the optimization process. Finally, an advanced optimization process needs to be carried out, and the material layout has to be finalized by the design engineer. Typically a number of constraints, such as manufacturing and cost constraints, need to be considered in the optimal material design process. A major objective of this research is to outline these constraints, as well as to find ways to ameliorate the optimization process to produce improved, cost-effective, and manufacturable engineered materials.
The Nanomechanics of Tetrahedral Amorphous Diamond-Like Carbon (ta-C) MEMS
Authors: Chasiotis I. , Cho S. W. , Friedmann T. A. , Sullivan J. P.
Published: May 2008

The mechanics of hydrogen-free tetrahedral amorphous diamond-like carbon (ta-C) MEMS structures have been investigated in connection with their elastic and failure properties. For this purpose, micro-tension specimens of thicknesses between 1.2 μm and 1.8 μm and gage widths of 10 μm or 50 μm have been fabricated by the Sandia National Laboratories (SNL). The mechanical characterization has been conducted via in situ AFM measurements and Digital Image Correlation (DIC) data strain analysis and the deformation fields of uniform tension specimens and internally notched specimens with acute notches (K=27) have been experimentally obtained. The elastic modulus and Poisson’s ratio were measured for the first time directly from the specimens averaging 750 GPa and ν=0.16 respectively, while the tensile strength was found to be very consistent averaging 7.0 GPa. Stressed material domains with smaller dimensions in the vicinity of micronotches exhibited even higher failure strength reaching an average of 11.5 GPa with about 10% scatter. AFM images of specimens under high tensile stresses have also indicated the possibility of an sp3 to sp2 phase transformation on the film surface at very high tensile stresses (>6 GPa).
Preliminary Mechanical Characterization of Reinforced Rigid Polyurethane Foams
Authors: Kasichainula Nagesh , Khanna Sanjeev K.
Published: May 2008

Rigid polyurethane foams are very widely used in a variety of structural and non-structural applications. For example, it may be used as an insulator, in sandwich layered composite panels, and as filler for improving the stiffness of lightweight components, such as thin metal tubes. Rigid foams do not show any recovery after impact and typically are crushed or crumble. They also tend to degrade over a period of time. Thus in this investigation, reinforced rigid polyurethane foams have been developed and characterized for their quasi-static mechanical properties. Rigid polyurethane foam was reinforced with short, 0.47 mm length, milled E-glass fibers. It has been observed that short glass fiber reinforcement helps in improving the mechanical properties, such as tensile modulus, breaking strength, and compression modulus, of the reinforced foam as compared to monolithic foam.
Damage Formation During Fracture of Polystyrene/Clay and Polystyrene/Nanoporous Silica Nanocomposites
Authors: Walter Mark E. , Zeng Changchun , Li Wenxia , Lannutti John J. , Lee L. Jim
Published: May 2008

Although clay-based polymer nanocomposites provide enhanced chemical properties, the mechanical properties and in particular, the effects of the nanoscale particles on mechanical properties, are not yet well understood. For this study, two types of raw polystyrene specimens, three polystyrene/clay nanocomposites, and one polystyrene/nanoporous silica nanocomposite were investigated. The nanocomposites differed in that one was produced through mechanical mixing, one through in situ polymerization, and one through exfoliation of the clay. All the clay composites had 5% particulate loading and tensile properties were similar. Standard three-point-bend fracture tests were performed to determine the fracture toughnesses of the different polystyrene nanocomposites and to investigate crack resistance curves. The process zone during crack propagation was observed in situ with an optical stereo microscope and with an optical profilometer. Post-test analysis of the microstructure and fracture surfaces was performed with electron microscopy. For the 5% particle loadings all composite polystyrene systems have lower toughnesses than the raw polystyrene.
An Education Program in Support of a Sustainable Future
Authors: Sutherland J. W. , Kumar V. , Crittenden J. C. , Durfee M. H. , Gershenson J. K. , Gorman H. , Hokanson D. R. , Hutzler N. J. , Michalek D. J. , Mihelcic J. R. , Shonnard D. R. , Solomon B. D. , Sorby S.
Published: May 2008

The historical evolution and current status of sustainability education at Michigan Technological University is described. The history considers the last 15 years, during which, the faculty of Michigan Tech have been collaborating on the development of environmental curricula and courses. This development effort initially focused on specialized offerings for the environmental/chemical engineering programs. With time, recognition of the importance of environmental issues (wastes, natural resources, energy, etc.) to other disciplines across the campus grew. For example, chemists, biologists, foresters, etc. each have a role in characterizing the behavior of ecological systems. Engineering disciplines that are focused on the design of products, processes, or systems influence long term societal sustainability. Social scientists must understand the relationship/linkages between the environment, industry, citizens, and government. Greener products, environmentally responsible processes, life cycle thinking, and environmental stewardship need to become part of the modern lexicon of globally aware students. Faculty from diverse disciplines across the campus are now collaborating to develop courses and modify curricula to educate students with respect to the triple bottom line (i.e., sustainable economic, societal, and environmental future). Problems associated with the traditional education paradigm are discussed. A new education model aimed at training students to create a sustainable future is proposed.
Investigations of Thermal Stresses and Deformations in Laser Microwelding Processes
Authors: Han Wei , Pryputniewicz Ryszard J.
Published: May 2008

Laser microwelding has become a significant industrial process, because there are many outstanding advantages in using laser welding as the bonding method over other widely used bonding technologies. As an alternative to the common adhesives or solders used for the joining process, laser welding offers a number of attractive features such as high weld strength to weld size ratio, reliability, and a minimal heat-affected zone (HAZ). These provide the benefits of low heat distortion, a non-contact process, repeatability, and ability to automate. Therefore, the applications of laser microwelding have been broadened, especially in the microelectronic and packaging industry, in recent past decades. Quality of the laser microwelding, however, depends on a number of parameters such as the characteristics of the laser beam, environmental conditions, and properties of the workpiece. Furthermore, the large temperature gradients occur during laser microwelding process leads to a high stress level, and might result in many undesirable phenomena such as the high level of residual stresses in the vicinity of the heat-affected zone (HAZ) that adversely affect the life time of the component. Numerous studies have been performed on the evaluation and prediction of the thermal stresses in laser microwelding process. However, it is very difficult to measure the thermal stresses, and to predict the magnitude and direction of thermal stress/deformation. Therefore, we develop an optical methodology, based on opto-electronic holography (OEH) technique, to measure and evaluate the thermal stresses/deformations non-destructively. In this paper, the system of OEH measurement of the thermal deformation of the laser welds will be described in details, and representative results will be included. In addition, analytical and computational models will also be developed to simulate the temperature field and thermal stresses/deformations in laser microwelding. Continued work will lead to novel measurement system for monitoring the thermal stresses/deformations during the process of laser microwelding, which will help optimizing efficient and effective laser micro-machining processes for applications in microelectronics and packaging.
Planar Waveguide Genetic Assay Readout Device
Authors: Wulfman David R. , Baas Tracey L. , McGlennen Ronald C.
Published: May 2008

A planar waveguide (PWG) device has been developed for the detection of fluorescently labeled nucleic acid sequences immobilized or hybridized to the surface of a planar waveguide. Unlike current technologies requiring image gathering and reading capabilities or specially textured waveguide surfaces, this instrument uses simple glass slide based arrays, providing a numerical output in proportion to the fluorescent intensity recorded. The system consists of an optical waveguide (a glass microscope slide), an excitation light source, a photo detector, filters for select fluorescent emissions and the positioning array cassette. A data analysis algorithm is presented for interpretation of two dimensionally organized arrays. Based on our experimental evaluations we conclude that this sensing system shows promise as a simple and effective means to read fluorescent microarrays.
Wafer-Level MEMS Package by Gold-Tin Bonding Method
Authors: Chen Sihai , Liu Sheng , Chen Mingxiang , Xiong Tao , Zhang Daming , Zhang Honghai , Yi Xinjian
Published: May 2008

This paper reports some results for an on-going program in wafer-level MEMS package Institute of Microsystems at Huazhong University of Science and Technology. The final goal was to come up with a method usable for various types of MEMS devices in wafer level so that the low cost and high reliability can be achieved at the same time. In this particular paper, three closed-loop microheaters of 5μm, 7μm and 9μm width were designed. By reactive ion sputtering technique, two classes of samples are presented. The first one was first co-sputtered with Ni/Cr and then sputtered with Au metal as heating with Ni/Cr and then sputtered with Au metal as heating material, the second one was sputtered with Cr, Sn and Au respectively as heating material. The bonding of the former sample based on the Ni/Cr and Au heating material failed. The eutectic bonding experiment of the later sample based on the Cr, Sn and Au heating material by global heating method was completed in annealing oven at temperature of about 400°C for 20 minutes and by local heating method was applyed current of 0.8 A into the microheater. The SEM testing result showed the eutectic bonding of Au-Sn by global heating was successful. More results will be reported during the conference presentation.
Buckling of the Composite Cracked Cylindrical Shells Subjected to Axial Load
Authors: Vaziri A. , Nayeb-Hashemi H. , Estekanchi H. E.
Published: May 2008

Cylindrical shells constitute the main structural components in pressure vessels and pipelines. Cylindrical shells made of fiber-reinforced composites are now being considered in the design of many components due to their high specific strength and stiffness. Buckling is one of the main failure considerations, when designing the cylindrical shells. The buckling behavior of the composite cylindrical shells can severely the compromised by introducing defect in the structure, due to high stress field generated around these defects. Defects could be generated during service due to cyclic loading or during manufacturing. A reliable operation of these structures require to understand the effects of these defects on the bucking of cylindrical shells. Finite Element Analyses are performed to study the buckling behaviour of composite cylindrical shells with and without a crack, under an axial compressive loading. The effects of the plies angle on the buckling loads and buckling mode shapes of the composite cylindrical shells are studied. Furthermore, the effects of the crack length and its orientation on the buckling loads of the composite cylindrical shells are investigated. The results indicate that the global buckling loads and mode shapes of the cracked composite shells are not significantly sensitive to the presence of the defect, for shells with a crack length less than a critical length. This critical crack length depends on the crack orientation, composite ply angles, ply sequence and the cylinder geometry. For shells with a crack longer than the critical length, the buckling load reduces and the local buckling mode at the crack tip prevail the buckling behavior of the composite cylindrical shell. The optimum ply angle for attaining the maximum buckling load is specified.
Failure Prediction for Textile Composites Via Micromechanics
Authors: Cox Brian , Yang Qingda
Published: May 2008

The question of failure criteria for textile composites is taken up, with reference to the micormechanics of known failure mechanisms in broad classes of 2D and 3D textile composites. Of primary importance is the definition of the measure of local stress or strain that should be compared against a putative material constant to predict local damage. In most prior work, some combination of strain or stress components evaluated at a single point has been used. Due to the complexity and inevitahle irregularity of textile composites, this approach is not favoured. Instead, micromechanical considreations recommend using strains averaged over gauge volumes whose dimensions are greater than or equal to approximately half the width dimensions of a single tow. Engineering tests that can be used for calibration are suggested but remain to be proven repeatable and consistent.
Numerical Simulation and Experimental Study of Suspension Flow With Deposition in Porous Media: Application to Sand Core Coating in Metalcasting Industry
Authors: Bakhtiyarov Sayavur I. , Overfelt Ruel A.
Published: May 2008

A diffusion flux principle of mass conservation was used for mathematical modeling of sand core coating process. A Galerkin method with linear axisymmetric square finite elements was used to solve the problem. It is shown that the coating thickness and the penetration depth increase with sand grain size. With increasing the apparent viscosity of the refractory coating slurry the coating thickness increase, but the penetration depth decreases linearly. A good agreement is found between the experimental data and numerical predictions.
Rotor Transverse Crack Detection and Diagnosis Using Embedded Modeling
Authors: McKee Kristoffer K. , Li C. James
Published: May 2008

This study proposes an embedded modeling methodology for identifying the crack-induced local stiffness reduction in a shaft from its horizontal and vertical vibrations. An embedded model integrating a dynamic model of the rotor system, and the unknown local stiffness reduction in the form of a universal function approximator i.e., neural network, is established. As a FEM model, it can describe rotors of complex geometry. A solution method is then established to identify the local stiffness reduction of the shaft due to a crack. Subsequently, a method is then used to find the location and size of the crack along the shaft. Simulated studies were conducted to demonstrate that the crack induced stiffness reduction of a Jeffcott rotor system can be identified, and the location, size and shape of the crack can be estimated by the proposed method with high level of accuracy.
Effect of Electrode Shape and Heat Loss Rates on Slag Flow and Heat Transfer
Authors: Xia J. L. , Ahokainen T. , Kankaanpa¨a¨ T.
Published: May 2008

Cylindrical electrode geometry was used in past studies, while practically the electrode is of conical shape. the present paper numerically simulates three-dimensional magnetohydro-dynamic flow in an electric furnace with three electrodes immersed into the slag by using an idealized cylindrical and an actual conical electrode shape. Calculations are also carried out for different heat loss rates along the free surface and teh furnace wall. Results show that the electrode shape has slight influence on slag flow behavior and the cylindrical electrode geometry may be used in case without information of actual electrode shape. It is important to correctly specify the boundary conditions at the free surface and the furnace wall in order to obtain reasonable prediction for the slag flow and heat transfer, and reasonable ranges of these conditions are obtained for the furnace considered.
Flow of Viscoplastic Fluids Through an Expansion Followed by a Contraction
Authors: Reis Luiz A. , Naccache Moˆnica F.
Published: May 2008

Flow of viscoplastic fluids through contractions and expansions are found in several industrial processes. Experimental results show that in this kind of flow a material fracture can occur in certain conditions. In this work, a numerical simulation of a viscoplastic fluid flows through an axysimetric expansion followed by a contraction is performed. One of the goals is to observe if the constitutive model used in the numerical simulation can predict this kind of pattern. The numerical solution of conservation equations of mass and momentum is obtained via finite volume method. In order to model the non-Newtonian behavior of the fluid, it is used the Generalized Newtonian Fluid constitutive equation, with the Carreau-Yasuda viscosity function. The results obtained show the influence of rheological and geometric parameters on flow patterns.
Development of Machine Tool Structure at the Early Stages of Design Process
Authors: Kushnir Emmanuil , Sheehan Terrence
Published: May 2008

The major task in the design process is to identify the optimal structural designs that would provide the best performance of the machine while minimizing the cost. It is known that eighty percent of the final cost and quality of a product are designed in during early stages of the design process. Design changes and optimization later in the design process can have only a limited impact on the final cost and quality. Thus it is critical that the right concept of the machine is selected in the early stages of the design. However, making informed decisions early in the design process is difficult because of time constraints and uncertainty. The analysis, which are performed during early stages of the design, typically have to work with information that is not clearly defined (sketches vs. drawings, all components or options are not included, developed duty cycles vs. actual cycles, unkown loads, etc.). Results of these preliminary analyses are rough and approximate but very effective where the level in precision required is less that the final design analysis. The timetable for these analysis is typically significantly shorter. The preliminary analyses of the machine concept and machine components have to provide sufficient data and criteria required to make sound decisions between concurrent designs. These considerations are important in the machine tool business, which have deal with large castings, expensive pattern costs and long lead-times. The machine tool specifications dictate the process of selection of the structural geometry, dimensions, and structural components. The selection process is constrained by geometrical limitations and functional requirements driven by the specifications. These constraints cannot be represented in all cases by obvious equality or inequality expressions and functions of a design stage. It is proposed to divide the early design process stage into three steps: - prepare sketches of acceptable conceptual designs with major components in place; - prepare sketches of major components and compare they as a individual parts to chose the bests for every concept; - implement these parts as simple conponents in the conceptual design and compare the conceptual designs by their major performance benefits. This approach allows comparing conceptual designs when the components for each design are prepared with the same knowledge of conditions and requirements, and are developed to similar level. The proposed conceptual approach is illustrated by design of nuemrical control machine tools.
Acoustic Radiation From Separated Boundary-Layer Flow Over a Rearward-Facing Step on a Flat Panel
Authors: Kargus Walter A. , Lauchle Gerald C.
Published: May 2008

The acoustic radiation from a turbulent boundary layer that occurs downstream of a rearward facing step discontinuity and reattaches to a flat plat is considred experimentally. The step is exposed ot a zero incidence, uniform subsonic flow. a quiet wall jet facility situated in an anechoic chamber is used for the studies. The “point” wall pressure spectra are measured by small, “pinhole” microphones located at various locations under the layer, including a point directly in the 90° corner of the step. The wall pressure fluctuations measured at the various locations are correlated with the signal detected by a far-field microphone. The measured cross-spectral densities are thus used to identify the relative contributions of the various flow regimes to the direct radiation. It is shown that the separation of the flow over the corner of the step is a dominant acoustic source, which is supported not only by the measured cross spectra, but also by the favorable comparison of the measured velocity power law to the theoretical value. Measurements made where the flow reattaches and at the turbulent boundary layer are less conclusive. This is because the pinhole tube attached to the microphone produced a sound due to a fluid-dynamic oscillation, which contaminated the measurement of the aeroacoustic sources.
Local Liquid Velocities in Horizontal, Annular Air/Water Flow
Authors: Kopplin Charles R.
Published: May 2008

A newly developed flow visualization method that utilizes a three color LED strobe has been used to study the axial and circumferential velocities of the liquid in horizontal, annular two-phase flow. This non-intrusive technique allows the tracking of naturally entertained air bubbles within the liquid film along the top, bottom, and sides of the tube. Sets of images have been obtained for multiple combinations of air and water flow rates ranging in quality from approximately 0.07 to 0.49. The bubble-tracking velocimetry measurement method is explained, and comparison of the current data with past results and their impact on annular flow modeling are discussed. The data do not support two of the four theories for liquid film distribution in annular, horizontal multiphase flow, while the two remaining theories cannot be directly examined using the three color LED strobe measurement technique.
LQG-Based Robust Control of Active Automobile Suspension
Authors: Porumamilla H. , Kelkar A. G.
Published: May 2008

This paper presents robust controller design for an active automobile suspension system using an interative LQG design technique. The main objective is to design an active feedback control for an automobile suspension system to ensure the ride comfort for passengers in the presence of unknown road disturbances. The control system designed is shown to be robust to uncertainties and parametric variations. The resulting interative LQG-based control design is shown to achieve a significant improvement in the performance, while maintaining a desired level of closed-loop stability that is robust to plant uncertainties and parametric variations. The controller design is also compared to some other active suspension designs published in the literature.
Analysis of Force Shape Characteristics and Detection of Depth-of-Cut Variations in End Milling
Authors: Yang Liuqing , DeVor Richard E. , Kapoor Shiv G.
Published: May 2008

This paper proposes an analytical approach to detect depth-of-cut variations based upon the cutting force shape characteristics in end milling. Cutting forces of a single-flute end mill are analyzed and classified into three types according to their shape characteristics. Cutting forces of a multiple-flute end mill are then classified by considering both the cutting types of the corresponding single-flute end mill and the degree of overlap of successive flutes in the cut. Force indices are extracted from the cutting forces and depth-of-cut variations are detected based upon the changes of the force shape characteristics via the force indices in an end-milling process. The detection methodology is validated through cutting experiments.
Simulation of Thermally Activated Metal Forming Process With Meso-Scale Crystal Plasticity
Authors: Wang Suhui , Xie Chunlei , Ye Le , Wu Xin
Published: May 2008

Under thermally activated deformation conditions many engineering metals (steels, aluminum and magnesium alloys) exhibit much enhanced formability; thus, thermal forming has received increasing interests by automotive industries. The thermally activated material constitutive behaviors are not only strain dependent, but also strain rate and temperature dependent, and it is sensitive to in-situ microstructure evolution. In addition, non-steady-state deformation at a high strain rate (in the order of 10−2s−1 or above) introduces additional challenges in forming simulation. In this case, von Mises based macroscopic plasticity are often not sufficient to describe material behaviors with complex thermomechanical history. In this paper, the rate-dependent crystal plasticity model [1] was applied to the high temperature and high strain rate deformation that is dominated by dislocation creep. A user material subroutine was developed and used for FEA metal forming simulation using commercial ABAQUS/Dynamic code. In the simulation, material behavior was computed based on crystal plasticity at each strain increment without using von-Mises equation or a look-up table of material testing data. By inputting different slip systems or their combinations, and by matching the predicted crystallographic textures with experimentally obtained ones, the active slip systems responsible for the deformation was identified. Then, the material parameters were best fitted to the tensile curves obtained at various strain rates and temperatures. The model was applied for more complex multi-axial metal forming processes. The material behavior, along with its crystallographic texture development, was obtained and validated. As a demonstration, this paper also provides an analysis of a newly developed thrmal forming process [2] with this meso-scale crystal plasticity approach. This forming process involves diameter expansion of a tubular workpiece under combined internal pressure and axial loading and at elevated temperatures.
Ammonia Condensation Heat Transfer in Air-Cooled Mesochannel Heat Exchangers
Authors: Chiriac Florea , Ilie Anica , Dumitrescu Rodica
Published: May 2008

A mathematical model is formulated in this paper for the prediction of the heat rejection rate, assuming that the total heat transfer area of the mesochannel condenser is made up of 2 different areas, corresponding to superheated vapor state and the two-phase flow state. Each of these areas is considered as an independent heat exchanger (Mamani et al., 1999). The tested mesochannel condenser, manufactured by a Romanian company for automotive air-conditioning systems, is made of aluminum, based on an extrusion process; an oven brazing process was used for the headers to tubes joints. Maximum heat rejection rate represents the criteria used in order to optimize the geometrical configuration of the condenser. This theoretical study resulted in an optimized geometrical configuration of the mesochannel condenser (Heun et al., 1996a; Heun et al., 1996b). Experimental research has been carried out using a mesochannel condenser of optimized geometrical configuration. In order to ensure a quasi-state operating regime, the air-cooled mesochannel condenser was mounted inside an air loop, having multiple regulating and control means for the following parameters: inlet air dry bulb temperature, inlet air wet bulb temperature, and inlet air flow rate. The authors of the present paper develop a comparative analysis of theoretical vs. experimental heat rejection rate and heat transfer coefficient for an ammonia air-cooled mesochannel condenser.
Case-Based Problem Solving Exercises for Engineering Education
Authors: Allada Venkat , Jose Vivas
Published: May 2008

This paper describes the development of a case-behind problem solving exercise that emphasizes the managerial and the engineering aspects of a real life project. Using the real life example of a quality initiative project that was completed at a laundry detergent plant of a international company, a series of modular exercises have been developed on topics such as organizational structure, process capability, six sigma, and Taguchi methods. The exercise modules have been developed by referring to the Bloom’s six levels of cognitive learning process. This paper provides some of the highlights of the exercise development process that may be useful to educators interested in developing their own case study-based exercises or adapting the available ones to suit their needs.
An Object-Oriented Framework for Mesoscopic Modeling of Microstructure Evolution in Materials Processing
Authors: Yu Qiang , Esche Sven K.
Published: May 2008

This paper addresses the design of a general-purpose, object-oriented simulation framework for mesoscopic modeling of microstructure evolution in material processing. Some new results obtained using a grain growth model, which was incorporated into this framework, are presented.
Transfer Enabling Device for the Physically Handicapped
Authors: Elliott Robert C. , Brew Matthew , Higgs David , Petrocelli Christopher , Ruby Derek , Thamire Chandrasekhar
Published: May 2008

The need for transferring a disabled individual from a wheelchair to another location and vice versa cannot be underemphasized, given the numerous day-to-day activities that may require relocation of the person and the psychological factors involved. While there are some devices currently available on the market that aid in transferring the handicapped individuals from one location to another, few are available for transferring them from a wheelchair to an automobile. Vehicular lifts, which is general require modification of the vehicle, and automobiles custom modified to accommodate wheelchairs are some examples of devices that facilitate transfer of individuals. However, these devices are in general suitable for one vehicle only and relatively expensive. This paper present the design of a device that will allow an individual to transfer himself/herself easily and safely from a wheelchair to automobile or another location and vice versa, with minimal assistance and at a relatively lower cost. Presented are the design and test results from a prototype. The results demonstrate that the intended specifications are satisfied and that this relatively low-cost design is likely to deliver a satisfactory performance and provide individuals in wheelchairs with more freedom to travel. Because of the easy usbility, less dependence on assistants, and ability for a larger range of vehicles to be used, the design may also provide feeling of independence.
How Bacteria Bind More Strongly Under Mechanical Force: The Catch-Bond FimH
Authors: Thomas Wendy E. , Sokurenko Evgeni V. , Vogel Viola
Published: May 2008

We study a protein that responds to mechanical force in most striking manner. We demonstrate that Escherichia coli bacteria need shear stress to bind to certain tissues and model surfaces; they bind strongest precisely when the body tries to wash them off. We have determined that the protein responsible for this behavior is FimH, a ubiquitous adhesion protein in intestinal bacteria that mediates adhesion to host cells via the carbohydrate mannose. Although mechanical force noramlly decreases bond lifetimes, we have shown that the bond betweeen FimH and simple mono-mannose receptors is s “catch-bond” that lasts longer under shear stress. In contrast, structural variations in either FimH or the receptor cause a stronger mode of adhesion in static conditions with little or no activation under force. We derive a structural for how mechanical force switches FimH to a strong binding mode by using steered molecular dynamics simulations, and validate the predictions with subsequent site-directed mutagenesis. The physiological consequences as well as the engineering principles suggested by the structural model will be discussed.
Application of Predictive Control for Autonomous Satellite Capture Using a Deployable Manipulator System
Authors: McCourt Richard , de Silva Clarence W.
Published: May 2008

Two prototypes of a robot known as the Multi-module Deployable Manipulator System (MDMS) have been developed in our laboratory. This manipulator is intended for carrying for research in space platform-based robotics. In the present paper, this manipulator is used in laboratory-simulated capture of an orbiting satellite. A model-based predictive controller is developed and implemented in the MDMS. Using the controlled manipulator, laboratory experiments are carried out to study autonomous capture of a free floating and spinning target. The objective is to evaluate the performance of the predictive controller for the capturing task. A planar prototype MDMS is used as the chaser robot in experiments, and the target statellite is simulated within the controller. The model of the target statelite assumes that it is free of any external torques and involves rotations within the plane of operation of the MDMS prototype. The predictions for the chaser robot are based on a model of the MDMS, linearized about the starting configuration of the task. An unconstrained predictive controller is used in the present experiments. The resluts from tracking various moving target are presented, with and without predictions of the target movement. The performance is shown to be quite satisfactory.
Passive Teleoperation of a Multi Degree of Freedom Hydraulic Backhoe Using Dynamic Passive Valve
Authors: Krishnaswamy Kailash , Li Perry Y.
Published: May 2008

Passive systems possess the beneficial properties of ease of human control, and stable interaction with arbitrary passive systems. Motivated by these properties, our research has been directed towards developing passive hydraulic systems. A novel hydraulic element called the apssive valve was first developed. The passive valve was used in single degree of freedm passive bilateral teleoperation of a hydraulic actuator. The teleoperation control ensured a) passive 2-port behavior of the teleoperator and b) bilateral between the human and the work environment with a power scaling vactor. Although passivity, coordination between the master and slave systems was ensured only when the teleoperator (and hence the passive valve) was manipulated at sufficiently low frequency. In this paper, we extend the previously proposed teleoperation control to multi-degree of freedom control of a hydraulic backhoe, and rectifies the previously imposed bandwidth limitation by accounting for the dynamics of the passive valve. The passivitiy property of the hydraulic backhoe ensures interaction stability with any human opperator and the work environment that could be modelled passive. The intrinically passive control ensures two-port, rigid coordinated behavior of the passive valve driven teleoperated backhoe.
Piezoelectric Energy Harvesting Using a Clamped Circular Plate: Experimental Study
Authors: Kim Sunghwan , Clark William W. , Wang Qing-Ming
Published: May 2008

Energy harvesting using piezoelectric material is not a new concept, but its small generation capability has not been attractive for mass energy generation. For this reason, little research has been done on the topic. Recently, wearable computer concepts, as well as small portable electrical devices, are a few motivations that have reignited the study of piezoelectric energy harvesting. The theory behind cantilever type piezoelectric elements is well known, but the transverse moving circular plate elements, which can be used in pressure type energy generation is not yet fully developed. The power generation in a circular plate depends on several factors. Among them, the poling direction and the stress distribution is important as shown in previous research. Specifically, it has been shown theoretically that grouping electrodes and repoling some of the regrouped segments can lead to optimized energy harvesting in a clamped circular plate structure. This paper provides experimental validation of those results. In this paper, three circular plate piezoelectric energy generators (PEG), one unmodified and two different regrouped unimorph PEGs, were used to support the regrouped PEG energy generation theory. The experimental results of regrouped PEGs will be presented with an eye toward guidelines for design of a useful energy harvesting structure.
Application of Continuum Damage Healing Mechanics to Self-Healing Composites
Authors: Barbero Ever J. , Lonetti Paolo
Published: May 2008

Contimuum Damage Healig Mechanics is an extension of CDM recently developed by the authors to model healing process in a variety of materials including rock salt, sinterized metals, ceramics, and polymer-matrix composties, bone and so. on. While the theoretical framework, of CDHM is general, parameter identification depends on the particular material being modeled and the specific material tests that are feasible to conduct for that class of materials. This presentation deals with the application of CDHM to the specific field of fiber-reinforced polymer-matrix composites. An overview of CDHM will be presented followed by a description of parameter identification. Results are shown in order in validate the numerical model of healing behavior of damaged polymeric matrix composite. Healed and not healed cases discussed in order show the model capability and to describe possible evoltution of the healed system.
The Impact of Steam Innovations on Ship Design: An Abbreviated History of Marine Engineering
Authors: Carr Matthew A.
Published: May 2008

The adaptation of steam engines for marine propulsion caused a dramatic shift in naval and commericial ship design during the 19th Century. The transition from sail to steam hastened the demise of several classes of ships and altered shippings routes from the trade winds to great circle routing. The conduct of naval warfare was always influenced by the limits of available propulsion technology. Throughout maritime history, innovative naval commanders sought ways to overrun, outmaneuver, and outlast their opponents. Coincident developments in armaments and armor, facilitated by this “new” propulsion technology, rendered the world’s sailing navies largely obsolete within a relatively brief period of the 19th Century. This presentation highlights the major technological advances in steam propulsion from the early combination of low-speed single-acting reciprocating engines driving paddle wheels through high-speed turbines and reduction gears driving multiple-blade variable-pitch propellers; and, boilers heated by hand-fed wood and coal through nuclear fission.
Hydraulic Driven Rotating Flexible Beam: Theoretical Modal Analysis and Proportional Servo Drive Parameter Influence
Authors: Freire Javier , Codina Esteve , Khamashta Munir
Published: May 2008

Understanding the behavior of system with flexible elements is increasingly important in modern day technology. Reducing the mass of machine elements leads to a remarkable improvement in dynamic performance. However, a loss of precision also occurs with such an increase in flexibility. In order to arrive at a better understanding of systems with flexible elements, we are investigating the particular behavior of a hydraulic servo driven rotating flexible beam with the aim of obtaining a methodology that could be applied to a real application. To investigate this behavior, a set of models has been developed. In this paper, a theoretical model, using classical modal analysis methodology, is presented. The flexible beam is modeled in a standard way and the hydraulic servo drive is modeled as a boundary condition. Only normal modes will be investigated. This approach allows considering the servo proportional constant and the cylinder mass. It will be show that the servo proportional constant has low influence in the system eigen frequencies. The theoretical model predictions are validated experimentally.