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Articles 1 - 12 of 12
Full-Text Articles in Engineering
Hybrid Transient-Parametric Method And System To Distinguish And Analyze Sources Of Acoustic Emission For Nondestructive Inspection And Structural, Health Monitoring, Yuris Dzenis
Department of Mechanical and Materials Engineering: Faculty Publications
A nondestructive evaluation (NDE) technique for inspecting or health monitoring of Structures and/or Specimens by analyzing acoustic emission (AE) signals emitted by the Structures and/or specimens. The method and System ana lyzes acoustic emission (AE) signals emitted by structures and/or Specimens. AE Signals emitted by the Structures and/or Specimens are parametrically filtered as a function of parametric filters corresponding to characteristic waveforms of transient AE classes of predefined AE signals. In para metric analysis, the filtering may be pre- or post-recording. In transient AE analysis, the filtering may be prior to transient recording of the transient signals.
Crash Attenuation System, John D. Reid, John R. Rohde, Dean L. Sicking
Crash Attenuation System, John D. Reid, John R. Rohde, Dean L. Sicking
Department of Mechanical and Materials Engineering: Faculty Publications
A crash attenuation system having an impact head, and energy absorption mechanism. The energy absorbing mechanism has a mandrel for rupturing thin-walled tubes in a controlled rupture to absorb impact forces from a colliding vehicle. A frame may be used to mount the system to a truck, trailer, guardrail, median barrier end treatment, or a crash cushion. Stress concentrators may be incorporated into the tubes and the mandrels to selectively control rupturing and energy dissipation.
A Time-Resolved Method For Nonlinear Ultrasonic Measurements, Stephen D. Holland, Wolfgang Sachse
A Time-Resolved Method For Nonlinear Ultrasonic Measurements, Stephen D. Holland, Wolfgang Sachse
Stephen D. Holland
We describe a time-resolved method for measuring nonlinear ultrasonic phenomena. Current approaches rely on a narrowband measurement of harmonic generation to identify and characterize nonlinearity. Concomitant with these techniques is poor time resolution. We address this limitation with a hybrid narrowband/broadband approach that provides simultaneous time resolution and harmonic isolation for the measurement of weak nonlinearites. We discuss applications and present demonstrative results showing harmonic generation both in water and at a dry contact aluminum-aluminum interface.
Delamination Resistant Composites Prepared By Small Diameter Fiber Reinforcement At Ply Interfaces, Youris A. Dzenis, Darrell H. Reneker
Delamination Resistant Composites Prepared By Small Diameter Fiber Reinforcement At Ply Interfaces, Youris A. Dzenis, Darrell H. Reneker
Department of Mechanical and Materials Engineering: Faculty Publications
A fiber reinforced composite material comprising a resin matrix and primary reinforcement fibers and further comprising secondary, smaller diameter, reinforcement fibers at one or more ply interfaces, or portion thereof, provides improved interlaminar toughness, strength, and delamination resistance and without substantial increase in weight. In one embodiment, the small fibers are attached to one side of a conventional prepreg prior to lamination. The small fibers are flexible and are expected to conform to the shape and distribution of the primary reinforcing fibers at the interface.
Energy Absorbing Breakaway Steel Guardrail Post, John R. Rohde, John D. Reid, Dean L. Sicking
Energy Absorbing Breakaway Steel Guardrail Post, John R. Rohde, John D. Reid, Dean L. Sicking
Department of Mechanical and Materials Engineering: Faculty Publications
An improved breakaway steel guardrail post for use in dissipation of impact energy upon impact of the post having an upper post member and a lower post member, a connecting joint, and a mechanism connected to the upper and lower post members for controlling the energy dissipation of the guardrail post about the connecting joint at a predetermined rate. A first embodiment utilizes a cable restraint lopped through openings in he guardrail posts. Other embodiments included straps and fasteners disigned to distort or fail at predetermined rates or strengths and combinations thereof.
Controlled Buckling Breakaway Cable Terminal, John D. Reid, John R. Rohde, Dean L. Sicking
Controlled Buckling Breakaway Cable Terminal, John D. Reid, John R. Rohde, Dean L. Sicking
Department of Mechanical and Materials Engineering: Faculty Publications
A crash attenuation apparatus for use with a guardrail system having rail posts and rail elements. An impact head has a buffer nose section and a rail post breaking beam system. The post breaking beam system has upper and lower breaking beams attached to the head. A guide tube is attached to the side of the head. A strut member extends from a first attachment point on the rail element to a second point downstream. Upon impact by a vehicle, the head breaks the first rail post, before impacting the strut and buckling the rail element downstream.
Factors Affecting The Quality Of Dry Shotcrete, El Rasheid Mohamed Abdalla El Khidir
Factors Affecting The Quality Of Dry Shotcrete, El Rasheid Mohamed Abdalla El Khidir
Archived Theses and Dissertations
No abstract provided.
Fatigue Response Of Thin Stiffened Aluminum Cracked Panels Repaired With Bonded Composite Patches, Jason B. Avram
Fatigue Response Of Thin Stiffened Aluminum Cracked Panels Repaired With Bonded Composite Patches, Jason B. Avram
Theses and Dissertations
This research investigated the fatigue response of precracked and patched 2024-T3 Aluminum panels with stiffeners. Patches were single-sided, unidirectional three ply boron/epoxy. Stiffeners were 2024-T3 aluminum and were riveted and bonded on. Disbonds were introduced into the repair bondline by inserting teflon strips. Three disbond configurations were investigated rack tip disbond (CTD) located at the edge of the patch in the path of crack propagation, full-width disbond (FWD) covering the entire crack, and end disbond (ED) located at each end of the patch and covering the full width. Each repaired panel was subjected to tension/tension cyclic fatigue with a maximum …
Modification Of Position And Attitude Determination Of A Test Article Through Photogrammetry To Account For Structural Deformation, Sean A. Krolikowski
Modification Of Position And Attitude Determination Of A Test Article Through Photogrammetry To Account For Structural Deformation, Sean A. Krolikowski
Theses and Dissertations
This study improved the current method of position and attitude determination to account for structural deformation of the wind tunnel test article due to aerodynamic loading. To account for deformation, parabolic bending and linear twisting coefficients were added into the Levenberg-Marquardt multi-parameter solver. By accounting for deformation, the accuracy of position and attitude determination was greatly improved. This study also takes a qualitative look at the optimum number of wind tunnel cameras and model targets. Optimal configuration was found to be around 50 targets and 2 cameras offset by 90 degrees.
The Development Of A Finite Element Program To Model High Cycle Fatigue In Isotropic Plates, William C. Shipman
The Development Of A Finite Element Program To Model High Cycle Fatigue In Isotropic Plates, William C. Shipman
Theses and Dissertations
As part of a joint AFRL/DAGSI turbine blade research effort, a computer program has been developed that uses a von Karman large-deflection two-dimensional finite element approximation to determine stress levels and patterns in isotropic thin plates. The dynamic loading of various plates has been carried out in order to model a high cycle fatigue situation. The research considered the various effects of mode shapes, resident frequency, non-linear cyclic effect, endurance limits, and stress variations within a high cycle fatigue environment. Two main initiatives were taken. First, a transient analysis tool was developed that calculates stress and displacement patterns over a …
Computational Investigation Of Aeromechanical Hcf Effects In A Compressor Rotor, Andrew L. White
Computational Investigation Of Aeromechanical Hcf Effects In A Compressor Rotor, Andrew L. White
Theses and Dissertations
High-Cycle Fatigue is a major problem facing the gas turbine industry today. It has been investigated by many researchers, using many different methods. Due to its highly complex nature, designers still do not have adequate tools to accurately predict the onset of high-cycle fatigue. A three-dimensional Navier-Stokes program was used to perform a study of the unsteady aerodynamics on a compressor rotor. The effect of aerodynamic detuning on the forced response of a rotor blade was compared to a baseline tuned rotor case. Detuning consisted of a ten percent decrease in circumferential spacing between alternate pairs of blades. The high-cycle …
Task Specific Uncertainty In Coordinate Measurement, R. G. Wilhelm, R. Hocken, H. Schwenke
Task Specific Uncertainty In Coordinate Measurement, R. G. Wilhelm, R. Hocken, H. Schwenke
Department of Mechanical and Materials Engineering: Faculty Publications
Task specific uncertainty is the measurement uncertainty associated with the measurement of a specific feature using a specific measurement plan. This paper surveys techniques developed to model and estimate task specific uncertainty for coordinate measuring systems, primarily coordinate measuring machines using contacting probes. Sources of uncertainty are also reviewed.