Browsing by Author "Eric Klang, Committee Member"

Filter results by typing the first few letters
Now showing 1 - 6 of 6
  • No Thumbnail Available
    Design Optimization of MagneShock Magnetorheological Shock Absorbers and Development of Fuzzy Logic Control Algorithms for Semi-Active Vehicle Suspensions
    (2004-04-22) Craft, Michael Jacob; Gregory Buckner, Committee Chair; Eric Klang, Committee Member; Jeff Eischen, Committee Member
    Automotive ride quality and handling performance remain challenging design tradeoffs for modern, passive automobile suspension systems. Despite extensive published research outlining the benefits of active vehicle suspensions in addressing this tradeoff, the cost and complexity of these systems prohibit widespread commercial adoption. Semi-active suspensions offer reduced performance benefits over passive suspensions without the cost and complexity associated with fully active systems. This paper outlines the benefits of implementing real-time, fuzzy logic control (FLC) to a vehicle suspension equipped with commercially available magnetorheological (MR) shock absorbers, Carrera MagneShocks™. MagneShocks™ utilize controllable electromagnets to change the MR fluid viscosity and vary the damping characteristics of the shock. The application of FLC to these components, based on the expertise of experienced engineers from the racing industry, was first tested and refined in simulation, then applied experimentally, resulting in the significant improvement of vehicle performance. Results include 25% reductions in sprung-mass absorbed power (U.S. Army 6 Watt Absorbed Power Criterion) as compared with typical original equipment (OE) shock absorbers over urban terrains in both simulation and experimentation. RMS sprung-mass accelerations were also reduced by as much as 9%, but usually with an increase in total suspension travel over the passive systems. Nominal degradations in RMS tire normal forces were documented through computer simulations. When compared to fixed-current MagneShocks™, FLC resulted in 2-9% reductions in RMS sprung-mass accelerations and comparable absorbed powers. Possible means for improving the performance of this semi-active suspension include reducing the suspension spring stiffness and increasing the dynamic damping range of the MagneShock™
  • No Thumbnail Available
    Fixed Abrasive Diamond Wire Saw Slicing of Single Crystal SiC Wafers and Wood
    (2003-04-08) Hardin, Craig William; Albert Shih, Committee Chair; John Strenkowski, Committee Member; Eric Klang, Committee Member
    This study investigates the effects of process parameters on fixed abrasive diamond wire saw machining. The effects of wire speed, rock frequency, and downfeed rate on cutting forces and surface roughness are studied during diamond wire saw slicing of single crystal SiC wafers. This study also investigates the machining of wood with oscillatory and looped style wire saws. The effects of feed rate, wire speed, coolant, and grain orientation on the cutting forces and surface roughness are studied. The design of the cutting experiments using three different wire saws are presented. The first experiment uses a Diamond Wire Technology Millennium spool-to-spool rocking motion diamond wire saw to machine single crystal SiC wafers. The next experiments use a Murg looped wire saw and a Model 7243 oscillatory wire saw from Well Diamond Wire Saws to machine pine and oak. A data acquisition system was constructed to record cutting forces, and signal-processing techniques were developed for removing noise. The diamond wire performed well, and afterwards the machined surfaces of all materials were measured to determine their surface roughness. A scanning electron microscope was used to examine the SiC wafers. Finally, the results and the direction of future work in this area are discussed.
  • No Thumbnail Available
    Initiation and Evolution of Dynamic Failure Mechanisms in Woven Composite Systems
    (2002-08-21) Baucom, Jared Newton; Mohammed Zikry, Committee Chair; Harvey Charlton, Committee Member; Eric Klang, Committee Member; John Bailey, Committee Member; Yiping Qiu, Committee Member
    The unique reinforcement geometry of three-dimensional orthogonally woven fabric-reinforced composites offers the potential of improved penetration resistance, in comparison with other composite systems. However, there has been a lack of understanding of how dynamic energy dissipation and failure modes are affected by fiber orientation and distribution. The major objective of this investigation is to characterize damage progression in woven composites under transverse loading conditions at three distinct velocity regimes, ranging from 10 μm/s to 0.5 km/s. The investigated systems included two-dimensional plain woven laminates, three-dimensional orthogonally woven monoliths, and three-dimensional woven laminates. The three-dimensional structure has also been utilized with a matrix-cellularization technique to explore how porosity can be tailored for enhanced energy absorption. Quasi-static perforation experiments were conducted, where punch loads were recorded. Damage progression was monitored by backlit videography. The three-dimensional laminates required a higher punch force and absorbed more energy than the two-dimensional laminates and three-dimensional monoliths. Low-velocity impact damage progression was investigated with an instrumented drop-weight impactor. Measurements were obtained for impact force and energy dissipation for multiple strikes. The radial spread of damage was smallest for the two-dimensional laminates and largest for the three-dimensional woven composites, which also had the greatest resistance to penetration and dissipated the most total energy. High-velocity impact experiments were conducted to determine energy absorption and compare failure modes of two-dimensional and three-dimensional composite systems. Energy absorption was comparable for the various systems, but damage was more localized for the two-dimensional woven system. These results indicate that the three-dimensional laminates consistently had greater perforation resistance than the two-dimensional laminates and the three-dimensional monolithic composites. This is due to unique energy absorption mechanisms, which involve the crimped portion of z-tows in the three-dimensional composites. This implies that failure can be controlled by manipulation of the properties of the z-tows. Hence, three-dimensional architectures can provide both an inherent capability to dissipate energy over a large radial area and a greater perforation strength than comparable two-dimensional laminate and three-dimensional monolithic composites.
  • No Thumbnail Available
    Joint Construction and Seismic Performance of Concrete-filled Fiber Reinforced Polymer Tubes
    (2004-12-01) Zhu, Zhenyu; Amir Mirmiran, Committee Chair; Eric Klang, Committee Member; Sami Rizkalla, Committee Member; James Nau, Committee Member
    Extensive studies in the past decade have shown superior performance of concrete-filled fiber reinforced polymer (FRP) tube (CFFT) under axial compression, as the system utilized both high tensile strength of FRP tube and high compressive strength of concrete core. FRP provides lightweight formwork during construction and life-long protection for concrete in harsh environments. Despite significant advances in the research of CFFT, still for the system to be used in either bridge or building construction, appropriate connections need to be developed. Considering unique mechanical properties of FRP, connections of the CFFT members are considered critical components of the entire system. Four sets of experiments were carried out to better understand and improve CFFT joint performance. Analytical model were developed and verified with each set of test. Initially, two pilot CFFT pier cap frames were precast and assembled with five joint concepts. The pier caps were tested under two cases of loading, which simulated various bridge traffic patterns. The pier cap was modeled with a general finite element analysis software, ANSYS, to investigate the relationship between its performance and the joint stiffness. Subsequently, four CFFT beam splices were tested. Various joint methods were developed with different internal reinforcement or external socket. In general, rigid body rotation dominated the CFFT beam performance, since joint stiffness was significantly lower than the member itself. To verify axial confinement model for large scale CFFT columns with internal reinforcement, a total of six CFFT column stubs were tested under uni-axial compression. Test results confirmed the validity of Samaan's confinement model. Finally, a set of CFFT column-footing assemblies were prepared to investigate construction feasibility and performance of joint methods that were developed through the previous experiments. The CFFT columns were subjected to a constant axial load and reverse cyclic load in lateral direction. The CFFT columns exhibited significant improvement over traditional RC columns in both ultimate capacity and deformation. An open software, OpenSees, was used to model the CFFT columns. The analysis showed a close agreement with test results. A detailed parametric study was conducted to identify important design variables for CFFT columns. CFFT system, with its superior performance over its RC counterpart under both static and earthquake loads, proved to be compatible with the civil engineering practice both in construction methods and in structural analysis techniques.
  • No Thumbnail Available
    Sensor Network for In-Situ Failure Identification in Woven Composites after Impact Events.
    (2008-04-25) Garrett, Ryan Charles; Kara Peters, Committee Chair; Mohammed Zikry, Committee Member; Eric Klang, Committee Member
  • No Thumbnail Available
    Transient Waves from Acoustic Emission Sources in Isotropic Plates Using a Higher Order Extensional and Bending Theory.
    (2010-03-15) Bogert, Philip B.; Fuh-Gwo Yuan, Committee Chair; Eric Klang, Committee Member; Kara Peters, Committee Member; Yong Zhu, Committee Member
    This dissertation presents a derivation for the transient wave response of an infinite isotropic plate to a general acoustic emission (AE) point source discontinuity loading, based on third-order plate theory. The calculation of the wave response is facilitated by employing the concept of a seismic moment tensor (or derived “equivalent†body-forces) to describe the loading from highly localized displacement discontinuities on a fracture surface. Further, the body forces from 3-D elasticity are converted to plate loadings for use in the plate theory wave equations of motion. The transient wave response can be detected as AE signals using piezoelectric sensors. In particular, time-dependent surface strains can be readily obtained experimentally. Therefore the results emphasize the calculation of the surface strains for potential comparison with future experiments. The calculated transient response, which represents waves propagating from a general AE point source in the plate, is expressed in an explicit integral form. It is shown that the transient response, which is given by double inverse Fourier transforms, can be simplified into a finite series involving inverse Hankel transforms which only require one-dimensional inversions for an isotropic plate. Thus numerical evaluation of the transient wave is more robust and accurate than that generated using two-dimensional inverse transforms and also, asymptotic solutions can be readily obtained. Nine types of AE sources representing different micro-damage mechanisms and their corresponding plate loads are discussed. Numerical results for four types of AE point sources with a Heaviside time history loading are presented. The long-term goal of the development, having established a relationship between disturbance and response, is to monitor responses in a structure and be able to determine the source, i.e. damage, type and location by solving the inverse problem in real time. What is new and different from previous work upon which this is building is that the extensional formulation is evaluated for general AE loading, and a higher order bending theory is developed and evaluated. Additionally, the polar conversion reduction to a single variable spatial integration is implemented for both theories.