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Articles 91 - 120 of 321
Full-Text Articles in Mechanical Engineering
In Situ Analysis Of Fatigue Crack Propagation In Polymer Foams, Elio E. Saenza, Leif A. Carlsson, Anette M. Karlsson
In Situ Analysis Of Fatigue Crack Propagation In Polymer Foams, Elio E. Saenza, Leif A. Carlsson, Anette M. Karlsson
Mechanical Engineering Faculty Publications
This paper presents an in situ SEM experimental study on cyclic crack propagation in closed-cell polymer foams. The microscopic failure mechanisms in precracked PVC and PES specimens of 60 and 90 kg/m3 densities were examined under low-cycle fatigue loading. In the PVC foam, crack propagation occurred incrementally by successive failure of cell boundaries in front of the crack tip. The crack occasionally jumped to cell boundaries above or below the main crack resulting in non-self similar growth. Crack propagation in the PES foam occurred incrementally by extensive plastic tearing and subsequent tensile failure of the cell edge in front …
Hybrid Position And Impedance Control Of A Forging Process, Derek Stake
Hybrid Position And Impedance Control Of A Forging Process, Derek Stake
ETD Archive
"Pick and place" robotic material handling has been a key to increase piece rates and reduced variability in forging processes. One of the drawbacks to current "pick and place" robotic material handling methods is the inability to locate the part after a forging operation and move it to the next position in a timely manner. If the billet changes position during the forging process, the manipulator will take longer to find the part and transfer it to the next station or the manipulator will be unable to move the part to the next position correctly which may cause scrap. Another …
Computational Study Of Savonius Wind Turbine, Asmita C. Chinchore
Computational Study Of Savonius Wind Turbine, Asmita C. Chinchore
ETD Archive
This project involves study of 2-Blade and 3-Blade Savonius vertical wind turbines positioned at different orientations. For a 2-Blade turbine the orientations considered were 0 degree, 45 degree, 90 degree and 135 degree in reference to the direction of the prevailing wind and for the 3-Blade turbine the orientations taken into account were 0 degree, 30 degree, 60 degree and 90 degree in reference to the direction of the prevailing wind. The basic aim of this thesis was to study how the two designs are different from each other and which design produces more power when applied with constant wind …
Vibration Analysis Of Anisotropic Plates, Special Case: Violin, Chaitanya J. Lomte
Vibration Analysis Of Anisotropic Plates, Special Case: Violin, Chaitanya J. Lomte
ETD Archive
This thesis presents vibration analysis of the top plate of Stradivari violin by creating a 3D model using SolidWorks and finding mode shapes and natural frequencies using SolidWorks simulation. The top plate was affixed to the bottom plate via a side wall following the contour of the violin plates. Assuming the input excitation is sinusoidal, it was applied at the location of bridge where the strings rest on it.. The static component of the force was calculated to be 83.17 N. The first five natural frequencies of the violin top plate are in the range of 150 to 450 Hertz. …
Aerodynamic Measurements Of A Variable-Speed Power-Turbine Blade Section In A Transonic Turbine Cascade, Ashlie B. Flegel
Aerodynamic Measurements Of A Variable-Speed Power-Turbine Blade Section In A Transonic Turbine Cascade, Ashlie B. Flegel
ETD Archive
The purpose of this thesis is to document the impact of incidence angle and Reynolds number variations on the 3-D flow field and midspan loss and turning of a 2-D section of a variable-speed power-turbine (VSPT) rotor blade. Aerodynamic measurements were obtained in a transonic linear cascade at NASA Glenn Research Center in Cleveland, OH. Steady-state data were obtained for ten incidence angles ranging from +15.8° to -51.0°. At each angle, data were acquired at five flow conditions with the exit Reynolds number (based on axial chord) varying over an order-of-magnitude from 2.12 ₉ 105 to 2.12 ₉ 106. Data …
Determining The Mechanical Properties Of Lattice Block Structures, Nathan Wilmoth
Determining The Mechanical Properties Of Lattice Block Structures, Nathan Wilmoth
ETD Archive
Lattice block structures and shape memory alloys possess several traits ideal for solving intriguing new engineering problems in industries such as aerospace, military, and transportation. Recent testing at the NASA Glenn Research Center has investigated the material properties of lattice block structures cast from a conventional aerospace titanium alloy as well as lattice block structures cast from nickel-titanium shape memory alloy. The lattice block structures for both materials were sectioned into smaller subelements for tension and compression testing. The results from the cast conventional titanium material showed that the expected mechanical properties were maintained. The shape memory alloy material was …
Biogeography-Based Optimization For Hydraulic Prosthetic Knee Control, Tim Wilmot, George Thomas, Berney Montavon, Rick Rarick, Antonie J. Van Den Bogert, Steve Szatmary, Daniel J. Simon, William Smith, Sergey Samorezov
Biogeography-Based Optimization For Hydraulic Prosthetic Knee Control, Tim Wilmot, George Thomas, Berney Montavon, Rick Rarick, Antonie J. Van Den Bogert, Steve Szatmary, Daniel J. Simon, William Smith, Sergey Samorezov
Electrical and Computer Engineering Faculty Publications
We discuss open-loop control development and simulation results for a newly-developed cyber-physical system (CPS) used as a semi-active, above-knee prosthesis. The control signal of our CPS consists of two hydraulic valve settings that control a linear cylinder actuator and provide torque to the prosthetic knee. We develop open-loop control using biogeography-based optimization (BBO), which is a recently developed evolutionary algorithm. The research contributes to the field of cyber-physical systems by showing that it is possible to find effective open-loop control signals for our newly proposed semi-active hydraulic knee prosthesis through a dual-system optimization process which includes both human and robot …
Separation Control On High Lift Low-Pressure Turbine Airfoils Using Pulsed Vortex Generator Jets, Ralph J. Volino, Mounir B. Ibrahim
Separation Control On High Lift Low-Pressure Turbine Airfoils Using Pulsed Vortex Generator Jets, Ralph J. Volino, Mounir B. Ibrahim
Mechanical Engineering Faculty Publications
Boundary layer separation control has been studied using vortex generator jets (VGJs) on a very high lift, low-pressure turbine airfoil. Experiments were done under low (0.6%) freestream turbulence conditions on a linear cascade in a low speed wind tunnel. Pressure surveys on the airfoil surface and downstream total pressure loss surveys were documented. Instantaneous velocity profile measurements were acquired in the suction surface boundary layer. Cases were considered at Reynolds numbers (based on the suction surface length and the nominal exit velocity from the cascade) of 25000 and 50000. Jet pulsing frequency and duty cycle were varied. In cases without …
Rotor Model Updating And Validation For An Active Magnetic Bearing Based High-Speed Machining Spindle, Adam C. Wroblewski, Jerzy T. Sawicki, Alexander H. Pesch
Rotor Model Updating And Validation For An Active Magnetic Bearing Based High-Speed Machining Spindle, Adam C. Wroblewski, Jerzy T. Sawicki, Alexander H. Pesch
Mechanical Engineering Faculty Publications
This paper presents an experimentally driven model updating approach to address the dynamic inaccuracy of the nominal finite element (FE) rotor model of a machining spindle supported on active magnetic bearings. Modeling error is minimized through the application of a numerical optimization algorithm to adjust appropriately selected FE model parameters. Minimizing the error of both resonance and antiresonance frequencies simultaneously accounts for rotor natural frequencies as well as for their mode shapes. Antiresonance frequencies, which are shown to heavily influence the model’s dynamic properties, are commonly disregarded in structural modeling. Evaluation of the updated rotor model is performed through comparison …
An Experimental Investigation Of Strain Rate, Temperature And Humidity Effects On The Mechanical Behavior Of A Perfluorosulfonic Acid Membrane, Zongwen Lu, Melissa Lugo, Michael H. Santare, Anette M. Karlsson, F. Colin Busby, Peter Walsh
An Experimental Investigation Of Strain Rate, Temperature And Humidity Effects On The Mechanical Behavior Of A Perfluorosulfonic Acid Membrane, Zongwen Lu, Melissa Lugo, Michael H. Santare, Anette M. Karlsson, F. Colin Busby, Peter Walsh
Mechanical Engineering Faculty Publications
The time-dependent hygro-thermal mechanical behavior of a perfluorosulfonic acid (PFSA) membrane (Nafion® 211 membrane) commonly used in Proton Exchange Membrane Fuel Cells (PEMFCs) is investigated at selected strain rates for a broad range of temperatures and humidities. Tensile tests and relaxation tests are conducted to determine Young’s modulus and proportional limit stress as functions of strain rate, temperature and humidity. The results show that Young’s modulus and proportional limit stress increase as the strain rate increases, and decrease as the temperature or humidity increases. The results also show that the mechanical response of Nafion® 211 membrane is more …
Effect Of Time-Dependent Material Properties On The Mechanical Behavior Of Pfsa Membranes Subjected To Humidity Cycling, Narinder S. Khattra, Anette M. Karlsson, Michael H. Santare, Peter Walsh, F. Colin Busby
Effect Of Time-Dependent Material Properties On The Mechanical Behavior Of Pfsa Membranes Subjected To Humidity Cycling, Narinder S. Khattra, Anette M. Karlsson, Michael H. Santare, Peter Walsh, F. Colin Busby
Mechanical Engineering Faculty Publications
A viscoelastic-plastic constitutive model is developed to characterize the time-dependent mechanical response of perfluorosulphonic acid (PFSA) membranes. This model is then used in finite element simulations of a representative fuel cell unit, (consisting of electrodes, gas diffusion layer and bipolar plates) subjected to standardized relative humidity (RH) cycling test conditions. The effects of hold times at constant RH, the feed rate of humidified air and sorption rate of water into the membrane on the stress response are investigated. While the longer hold times at high and low humidity lead to considerable redistribution of the stresses, the lower feed and sorption …
Controlled Deflection Approach For Rotor Crack Detection, Zbigniew Kulesza, Jerzy T. Sawicki
Controlled Deflection Approach For Rotor Crack Detection, Zbigniew Kulesza, Jerzy T. Sawicki
Mechanical Engineering Faculty Publications
Atransverse shaft crack is a serious malfunction that can occurdue to cyclic loading, creep, stress corrosion, and other mechanismsto which rotating machines are subjected. Though studied for manyyears, the problems of early crack detection and warning arestill in the limelight of many researchers. This is dueto the fact that the crack has subtle influence onthe dynamic response of the machine and still there areno widely accepted, reliable methods of its early detection. Thispaper presents a new approach to these problems. The methodutilizes the coupling mechanism between the bending and torsional vibrationsof the cracked, nonrotating shaft. By applying an external lateralforce …
Rigid Finite Element Model Of A Cracked Rotor, Zbigniew Kulesza, Jerzy T. Sawicki
Rigid Finite Element Model Of A Cracked Rotor, Zbigniew Kulesza, Jerzy T. Sawicki
Mechanical Engineering Faculty Publications
The article introduces a new mathematical model for the cracked rotating shaft. The model is based on the rigid finite element (RFE) method, which has previously been successfully applied for the dynamic analysis of many complicated, mechanical structures. In this article, the RFE method is extended and adopted for the modeling of rotating machines. An original concept of crack modeling utilizing the RFE method is developed. The crack is presented as a set of spring–damping elements of variable stiffness connecting two sections of the shaft. An alternative approach for approximating the breathing mechanism of the crack is introduced. The approach …
On Establishing Elastic–Plastic Properties Of A Sphere By Indentation Testing, J. K. Phadikar, T. A. Bogetti, Anette M. Karlsson
On Establishing Elastic–Plastic Properties Of A Sphere By Indentation Testing, J. K. Phadikar, T. A. Bogetti, Anette M. Karlsson
Mechanical Engineering Faculty Publications
Instrumented indentation is a popular technique for determining mechanical properties of materials. Currently, the evaluation techniques of instrumented indentation are mostly limited to a flat substrate being indented by various shaped indenters (e.g., conical or spherical). This work investigates the possibility of extending instrumented indentation to non-flat surfaces. To this end, conical indentation of a sphere is investigated where two methodologies for establishing mechanical properties are explored. In the first approach, a semi-analytical approach is employed to determine the elastic modulus of the sphere utilizing the elastic unloading response (the “unloading slope”). In the second method, reverse analysis based on …
Predictive Musculoskeletal Simulation Using Optimal Control: Effects Of Added Limb Mass On Energy Cost And Kinematics Of Walking And Running, Antonie J. Van Den Bogert, Maarten Hupperets, Heiko Schlarb, Berthold Krabbe
Predictive Musculoskeletal Simulation Using Optimal Control: Effects Of Added Limb Mass On Energy Cost And Kinematics Of Walking And Running, Antonie J. Van Den Bogert, Maarten Hupperets, Heiko Schlarb, Berthold Krabbe
Mechanical Engineering Faculty Publications
When designing sports equipment, it is often desirable to predict how certain design parameters will affect human performance. In many instances, this requires a consideration of human musculoskeletal mechanics and adaptive neuromuscular control. Current computational methods do not represent these mechanisms, and design optimization typically requires several iterations of prototyping and human testing. This paper introduces a computational method based on musculoskeletal modeling and optimal control, which has the capability to predict the effect of mechanical equipment properties on human performance. The underlying assumption is that users will adapt their neuromuscular control according to an optimality principle, which balances task …
A Double Cantilever Beam Specimen For Foam Core Fracture Characterization, Elio E. Saenz, Adrián Hernández-Pérez, Leif A. Carlsson, Anette M. Karlsson
A Double Cantilever Beam Specimen For Foam Core Fracture Characterization, Elio E. Saenz, Adrián Hernández-Pérez, Leif A. Carlsson, Anette M. Karlsson
Mechanical Engineering Faculty Publications
This article presents the analysis and test results for a new sandwich double cantilever beam specimen for foam fracture characterization. The foam is sandwiched between two stiff and strong aluminum adherends. The specimen is analyzed using a modified version of the classical Kanninen elastic foundation model. Finite element analysis is conducted to determine the stress state near the crack tip and compliance of the double cantilever beam sandwich specimen. Model predictions are compared to experimental compliance data and crack growth paths for double cantilever beam specimens with polyvinyl chloride and polyethersulfone foams. The elastic foundation model and finite element analysis …
Predictive Simulation Of Gait At Low Gravity Reveals Skipping As The Preferred Locomotion Strategy, Marko Ackermann, Antonie J. Van Den Bogert
Predictive Simulation Of Gait At Low Gravity Reveals Skipping As The Preferred Locomotion Strategy, Marko Ackermann, Antonie J. Van Den Bogert
Mechanical Engineering Faculty Publications
The investigation of gait strategies at low gravity environments gained momentum recently as manned missions to the Moon and to Mars are reconsidered. Although reports by astronauts of the Apollo missions indicate alternative gait strategies might be favored on the Moon, computational simulations and experimental investigations have been almost exclusively limited to the study of either walking or running, the locomotion modes preferred under Earth's gravity. In order to investigate the gait strategies likely to be favored at low gravity a series of predictive, computational simulations of gait are performed using a physiological model of the musculoskeletal system, without assuming …
A Three-Dimensional Inverse Finite Element Analysis Of The Heel Pad, Snehal Chokhandre, Jason P. Halloran, Antonie J. Van Den Bogert, Ahmet Erdemir
A Three-Dimensional Inverse Finite Element Analysis Of The Heel Pad, Snehal Chokhandre, Jason P. Halloran, Antonie J. Van Den Bogert, Ahmet Erdemir
Mechanical Engineering Faculty Publications
Quantification of plantar tissue behavior of the heel pad is essential in developing computational models for predictive analysis of preventive treatment options such as footwear for patients with diabetes. Simulation based studies in the past have generally adopted heel pad properties from the literature, in return using heel-specific geometry with material properties of a different heel. In exceptional cases, patient-specific material characterization was performed with simplified two-dimensional models, without further evaluation of a heel-specific response under different loading conditions. The aim of this study was to conduct an inverse finite element analysis of the heel in order to calculate heel-specific …
Cfd And Heat Transfer Models Of Baking Bread In A Tunnel Oven, Raymond Matthew Adamic
Cfd And Heat Transfer Models Of Baking Bread In A Tunnel Oven, Raymond Matthew Adamic
ETD Archive
The importance of efficiency in food processing cannot be overemphasized. It is important for an organization to remain consumer- and business-oriented in an increasingly competitive global market. This means producing goods that are popular, of high quality and low cost for the consumer. This research involves studying existing methods of baking bread in a common type of industrial oven - the single level bread baking tunnel oven. Simulations of the oven operating conditions and the conditions of the food moving through the oven are performed and analyzed using COMSOL, an engineering modeling, design and simulation software. The simulation results are …
Computational Analyses For Fluid Flow And Heat Transfer In Different Curved Geometries, Carlin Miller Lucente
Computational Analyses For Fluid Flow And Heat Transfer In Different Curved Geometries, Carlin Miller Lucente
ETD Archive
Three-dimensional Computational Fluid Dynamics (CFD) models were developed to simulate fluid flow and heat transfer in a variety of helical channel geometries: circular and elliptical. Laminar flow was observed for Reynolds number between 200 and 1000. Code validation was done for developing steady laminar flow in a circular curved channel. The CFD results were compared to previous numerical results to verify that the model was producing valid results. The curve of the channel has a centrifugal effect on the fluid flow creating secondary flow known as Dean cells. This secondary flow moves the location of the maximum axial velocity towards …
Finite Element Analysis Of Spur Gear Set, V.S.N. Karthik Bommisetty
Finite Element Analysis Of Spur Gear Set, V.S.N. Karthik Bommisetty
ETD Archive
A Finite Element procedure has been developed in this work to determine the load distribution factor, Km, of the AGMA formula for a set of spur gear. At first, a spur gear with perfect involute is modeled using a 3-D CAD software. The model is them is assembled with shafts having 1, 2, and 3 degree misalignments. The generated 3-D models were in turn imported to ANSYS workbench to calculate the maximum bending and contact stresses using finite element method. The results generated were then compared with the maximum bending stress results obtained for parallel shafts to estimate the Load …
Mathematical Modeling Of Dc Cardiac Ablation, Sowmya Reddy Narala
Mathematical Modeling Of Dc Cardiac Ablation, Sowmya Reddy Narala
ETD Archive
This thesis presents a mathematical modeling of the cardiac DC ablation procedure. The model treats the procedure as a one dimensional heat transfer phenomenon taking place across the thickness of the myocardium. The model further considers a constant 37 oC for one of the boundary condition of the affected tissue, and the temperature of the other boundary condition is set to be a time dependent square-pulse variations. The parameters defining this time dependent boundary condition is used to perform parametric studies to predict tissue temperature at different depth of the myocardium. The initial condition of the myocardium prior to the …
A Finite Element Approach To Stress Analysis Of Face Gears, Lokamanya Siva Manohar Rampilla
A Finite Element Approach To Stress Analysis Of Face Gears, Lokamanya Siva Manohar Rampilla
ETD Archive
Face Gears have alternative gear-teeth configuration compared to Bevel Gears. Face Gear have a standard spur pinion as opposed to a bevel Gear. This work concentrates on modeling of a Face-gear, Meshed with a spur gear, using CAD Software and Finite Elements Analysis. The bending stress developed at the gear teeth is determined. Numerical results are validated using the bending stress developed between two involute spur gears
Modeling, Simulation And Experimental Verification Of An Electric Bicycle With Regenerative Braking, Maulik Kalolia
Modeling, Simulation And Experimental Verification Of An Electric Bicycle With Regenerative Braking, Maulik Kalolia
ETD Archive
Electric bicycles are widely available in user markets. However their use as a daily commuting vehicle is limited due to the need for frequent recharging. This thesis focuses on the mathematical modeling of electrical bicycle with regenerative breaking. Basic bond graphs methods are discussed here to develop state space models for mechatronic systems. A bond graph based mathematical model of an electric bicycle with regeneration is developed in this thesis. Mathematical models are tested in simulation, generating different road scenarios. Parameters required for the simulation are calculated using an experimental setup. The thesis shows the capability of bond graphs to …
Free Convection Along A Vertical Wavy Surface In A Nanofluid, Deepak Ravipati
Free Convection Along A Vertical Wavy Surface In A Nanofluid, Deepak Ravipati
ETD Archive
The study of this paper is to introduce a boundary layer analysis for the fluid flow and heat transfer characteristics of an incompressible nanofluid along a vertical wavy surface in a nanofluid. The Resulting transformed governing equations are solved numerically by an implicit finite-difference scheme (Keller-Box method). The results are presented for the major parameters including the wave amplitude , buoyancy ratio parameter , Brownian motion parameter , Thermophoresis parameter and Lewis number. A systematic study on the effects of the various parameters of the local frication factor, surface heat transfer rate (Nusselt number) and mass transfer rate (Sherwood number) …
Accelerated Fatigue Crack Growth Simulation In A Bimaterial Interface, R. Moslemian, Anette M. Karlsson, C. Berggreen
Accelerated Fatigue Crack Growth Simulation In A Bimaterial Interface, R. Moslemian, Anette M. Karlsson, C. Berggreen
Mechanical Engineering Faculty Publications
A method for accelerated simulation of fatigue crack growth in a bimaterial interface (e.g. in a face/core sandwich interface) is proposed. To simulate fatigue crack growth, a routine is incorporated in the commercial finite element program ANSYS and a method to accelerate the simulation is implemented. The proposed method (the cycle jump technique) is based on conducting finite element analysis for a set of cycles to establish a trend line, extrapolating the trend line spanning many cycles, and use the extrapolated state as initial state for additional finite element simulations. A control criterion is utilized to ensure the accuracy of …
Aspects Of Fatigue Failure Mechanisms In Polymer Fuel Cell Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson
Aspects Of Fatigue Failure Mechanisms In Polymer Fuel Cell Membranes, Ahmet Kusoglu, Michael H. Santare, Anette M. Karlsson
Mechanical Engineering Faculty Publications
The swelling-driven fatigue behavior of polymer fuel cell membranes during relative humidity (RH) cycling is investigated. In particular, swelling-induced membrane stresses are obtained from a numerical model simulating fuel cell RH cycle tests, and compared to the lifetimes obtained experimentally from tests conducted in the absence of electrochemical effects. A strong correlation between the lifetimes of the membranes in the actual tests and model results is obtained. In general, higher RH (or swelling) amplitude results in larger stress amplitudes and shorter lifetime, that is, fewer cycles to failure. Tensile stresses are needed for forming local cavities in the membrane, which …
A Multi-Regulator Sliding Mode Control Strategy For Output-Constrained Systems, Hanz Richter
A Multi-Regulator Sliding Mode Control Strategy For Output-Constrained Systems, Hanz Richter
Mechanical Engineering Faculty Publications
This paper proposes a multi-regulator control scheme for single-input systems, where the setpoint of a regulated output must be changed under the constraint that a set of minimum-phase outputs remain within prescribed bounds. The strategy is based on a max–min selector system frequently used in the aerospace field. The regulators used for the regulated and limited outputs are of the sliding mode type, where the sliding variable is defined as the difference between an output and its allowable limit. The paper establishes overall asymptotic stability, as well as invariance properties leading to limit protection. The design methodology is illustrated with …
Exploration Of Nde Properties Of Amb Supported Rotors For Structural Damage Detection, Jerzy T. Sawicki, Dmitry L. Storozhev, John D. Lekki
Exploration Of Nde Properties Of Amb Supported Rotors For Structural Damage Detection, Jerzy T. Sawicki, Dmitry L. Storozhev, John D. Lekki
Mechanical Engineering Faculty Publications
Recent advancements in actuator technology, power electronics, sensors, and signal processing have created a rapid development of smart machine technologies for rotating machinery. Ranging from machine condition monitoring and diagnostics to full active control of machine behavior, the integration of electrical and computer systems has produced significant advances in machine performance and reliability. Magnetic bearings are a typical mechatronics product. The hardware is composed of mechanical components combined with electronic elements such as sensors and power amplifiers and an information processing part, usually in the form of a microprocessor. In addition, an increasingly important part is software, which specifies the …
In Situ Analysis Of Crack Propagation In Polymer Foams, Elio E. Saenz, Leif A. Carlsson, Anette M. Karlsson
In Situ Analysis Of Crack Propagation In Polymer Foams, Elio E. Saenz, Leif A. Carlsson, Anette M. Karlsson
Mechanical Engineering Faculty Publications
This article presents an experimental study on the microscopic mechanisms associated with crack propagation in closed cell polymer foams. A brittle, slightly cross-linked polyvinyl chloride (PVC) foam of density 60 kg/m3 and a ductile thermoplastic polyether sulfone (PES) foam of density 90 kg/m3 were examined. The PVC and PES foams have similar cell size (≈0.7 mm) but the cell edges of the PES foam were much thicker than those in the PVC foam. Overall, it was observed that the elements of both foams fractured in an extensional mode. Crack propagation in the PVC foam was inter-cellular, where agglomerates …