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Articles 1 - 6 of 6
Full-Text Articles in Engineering
Internal Damage Detection And Assessment In Beams Using Experimental Natural Frequencies, Frances K. Durham
Internal Damage Detection And Assessment In Beams Using Experimental Natural Frequencies, Frances K. Durham
Theses and Dissertations
This study investigated the frequency response of a cantilever beam with the intent of establishing a reliable nondestructive method of damage detection. The test specimens were 12 aluminum 2024 T3 beams, each identical except for a unique, eccentrically located notch, and one reference notchless beam. The machined notches varied in length and location to simulate varying degrees of damage. Laser doppler vibrometry enabled the data acquisition. The changes in natural frequencies were correlated to notch length and notch location. A comparison of eccentric and centered notch influence on the natural frequencies also is discussed.
Mechanical Behavior Of Cracked Panels Repaired With Bonded Composite Patch, Michael A. Hansen
Mechanical Behavior Of Cracked Panels Repaired With Bonded Composite Patch, Michael A. Hansen
Theses and Dissertations
This research focuses on investigating the mechanical behavior of cracked aluminum panels repaired with bonded boron/epoxy composite patches. The effects of crack initiation and growth on the residual strength of the repaired panels are characterized. This research establishes a correlation between damage modes, residual strength and evolution of strain within as well as outside the patch. Monotonic tensile tests on specimens with a perfectly bonded patch were used to determine the base line strength. Likewise, fatigue tests on specimens with a perfectly bonded patch served to establish baseline fatigue life. In addition, several specimens with a perfectly bonded patch were …
An Investigation Of A Simplified Gouging Model, Gregory S. Rickerd
An Investigation Of A Simplified Gouging Model, Gregory S. Rickerd
Theses and Dissertations
Gouging is a type of structural failure that becomes important when two metals slide against each other at velocities in the range of 1.5 kilometers per second. A computer model has previously been used to model the development of gouging at the Holloman High Speed Test Track. This model has not been experimentally verified to be correct, due to the complexity of the model. This research develops a simplified model that can be experimentally verified. The computer program utilized in this research was studied to determine the most appropriate options to use in simulations. This was accomplished by modeling a …
Fatigue Behavior Of A Functionally-Graded Titanium Matrix Composite, Scott R. Cunningham
Fatigue Behavior Of A Functionally-Graded Titanium Matrix Composite, Scott R. Cunningham
Theses and Dissertations
Functionally-graded Titanium Matrix Composites are an attempt to utilize the high-strength properties of a titanium matrix composite with a monolithic alloy having the more practical machining qualities. This work studied the mechanical characteristics of the joint region as a first step toward future evaluation of this material. The scope of this effort involved testing under monotonic tension and fatigue loading conditions. Mechanical properties and cyclic behavior were evaluated for the joint area and then compared to those of the parent materials. The results of this study found that the strength of the transition region was slightly higher than the unreinforced …
Analysis Of Computational Methods For The Treatment Of Material Interfaces, Minh C. Nguyen
Analysis Of Computational Methods For The Treatment Of Material Interfaces, Minh C. Nguyen
Theses and Dissertations
Rocket sled tests at the Air Force Research Laboratory's Holloman High Speed Test Track frequently approach velocities where gouging development becomes the limiting factor to achieving higher operating velocities. Direct observation of the gouging process is not possible so computational modeling is necessary to study the phenomenon. Since gouging development is dependent on the impact surface conditions, the method used to model material interfaces directly affects the accuracy of the solution. Three methods are available in the hydrocode CTH to handle material interfaces: 1) materials are joined at the interface, 2) a frictionless slide line is inserted, and 3) a …
Tensile Stress Rupture Behavior Of A Woven Ceramic Matrix Composite In Humid Environments At Intermediate Temperature, Kevin J. Larochelle
Tensile Stress Rupture Behavior Of A Woven Ceramic Matrix Composite In Humid Environments At Intermediate Temperature, Kevin J. Larochelle
Theses and Dissertations
Stress rupture tests on the SylramicTM fiber with an in-situ layer of boron nitride, boron nitride interphase, and SiC matrix ceramic matrix composite were performed at 550°C and 750°C with 0.0, 0.2, or 0.6 atm partial pressure of water vapor, pH2O. The 550°C, 100-hr strengths were 75%, 65% and 51% of the monotonic room temperature tensile strength, respectively. At 750°C, the strengths were 67%, 51%, and 49%, respectively. Field Emission Scanning Electron Microscopy analysis estimated the total embrittlement times for 550°C with 0.0, 0.2, and 0.6 atm pH2O were >63 hrs, >38 hrs, and between …