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- Bimaterial interface; Fracture mechanics; Fatigue crack growth; Cycle jump technique (1)
- Biomechanics (1)
- Control with constraints; Sliding modes; Hybrid systems; Aircraft engines; Selector systems (1)
- Failure; fatigue analysis; fatigue behavior; fuel cells; ionomers; mechanical properties; PFSA membrane (1)
- Laminates; Mechanical properties; Strength; Damage tolerance (1)
Articles 1 - 10 of 10
Full-Text Articles in Engineering
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 …
On The Opening Of A Class Of Fatigue Cracks Due To Thermo-Mechanical Fatigue Testing Of Thermal Barrier Coatings, M. T. Hernandez, D. Cojocaru, M. Bartsch, Anette M. Karlsson
On The Opening Of A Class Of Fatigue Cracks Due To Thermo-Mechanical Fatigue Testing Of Thermal Barrier Coatings, M. T. Hernandez, D. Cojocaru, M. Bartsch, Anette M. Karlsson
Mechanical Engineering Faculty Publications
The evolution of fatigue cracks observed in thermal barrier coatings (TBCs) subjected to an accelerated test scheme is investigated via numerical simulations. The TBC system consists of a NiCoCrAlY bond coat and partially yttria stabilized zirconia top coat with a thermally grown oxide (TGO) between these two coatings. The cracks of interest evolve in the bond coat parallel and near the interface with the TGO during thermo-mechanical fatigue testing. In their final stage, the cracks lead to partial spallation of the TBC. This study focuses on why the cracks open to their characteristic shape. To this end, finite element simulations …
Characterization Of Fracture Toughness G (Sub C) Of Pvc And Pes Foams, Elio E. Saenz, Leif A. Carlsson, Anette M. Karlsson
Characterization Of Fracture Toughness G (Sub C) Of Pvc And Pes Foams, Elio E. Saenz, Leif A. Carlsson, Anette M. Karlsson
Mechanical Engineering Faculty Publications
The fracture behavior of polyvinyl chloride (PVC) and polyethersulfone (PES) foams has been examined using the single-edge notch bend and the double cantilever beam (DCB) tests. PVC foam densities ranging from 45 to 100 kg/m3 and PES foam densities ranging from 60 to 130 kg/m3 were examined. The PVC foams failed in a linear elastic brittle manner, whereas the PES foams displayed much more ductility and substantially larger toughness at a comparable foam density. The cell wall thickness of the PES foams was almost twice the thickness of the PVC foams which may have contributed to the high …
Detecting Cracked Rotors Using Auxiliary Harmonic Excitation, Jerzy T. Sawicki, Michael I. Friswell, Zbigniew Kulesza, Adam C. Wroblewski, John D. Lekki
Detecting Cracked Rotors Using Auxiliary Harmonic Excitation, Jerzy T. Sawicki, Michael I. Friswell, Zbigniew Kulesza, Adam C. Wroblewski, John D. Lekki
Mechanical Engineering Faculty Publications
Cracked rotors are not only important from a practical and economic viewpoint, they also exhibit interesting dynamics. This paper investigates the modelling and analysis of machines with breathing cracks, which open and close due to the self-weight of the rotor, producing a parametric excitation. After reviewing the modelling of cracked rotors, the paper analyses the use of auxiliary excitation of the shaft, often implemented using active magnetic bearings to detect cracks. Applying a sinusoidal excitation generates response frequencies that are combinations of the rotor spin speed and excitation frequency. Previously this system was analysed using multiple scales analysis; this paper …
Mechanical Behavior Of Bio-Inspired Laminated Composites, Liang Cheng, Adam Thomas, James L. Glancey, Anette M. Karlsson
Mechanical Behavior Of Bio-Inspired Laminated Composites, Liang Cheng, Adam Thomas, James L. Glancey, Anette M. Karlsson
Mechanical Engineering Faculty Publications
To investigate if the relative high strength and stiffness of biological composites can be translated into man-made materials, innovative bio-inspired laminated composites with commercial materials (glass epoxy prepreg) were designed and manufactured by incorporating the distinctive helicoidal morphology observed in the exoskeletons of crustaceans. The helicoidal structure is characterized by a stacking sequence consisting of a gradual rotation of each lamina in the multi-layered laminated composites. Variations of the helicoidal structure were designed and produced to address some important issues encountered in the practical composites manufacturing process, including mid-plane symmetry. In addition, composite structures with a general quasi-isotropic configuration were …
Implicit Methods For Efficient Musculoskeletal Simulation And Optimal Control, Antonie J. Van Den Bogert, Dimitra Blana, Dieter Heinrich
Implicit Methods For Efficient Musculoskeletal Simulation And Optimal Control, Antonie J. Van Den Bogert, Dimitra Blana, Dieter Heinrich
Mechanical Engineering Faculty Publications
The ordinary differential equations for musculoskeletal dynamics are often numerically stiff and highly nonlinear. Consequently, simulations require small time steps, and optimal control problems are slow to solve and have poor convergence. In this paper, we present an implicit formulation of musculoskeletal dynamics, which leads to new numerical methods for simulation and optimal control, with the expectation that we can mitigate some of these problems. A first order Rosenbrock method was developed for solving forward dynamic problems using the implicit formulation. It was used to perform real-time dynamic simulation of a complex shoulder arm system with extreme dynamic stiffness. Simulations …