Browsing by Subject "infrared thermography"
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Item An Examination of Configurations for Using Infrared to Measure Boundary Layer Transition(2012-10-19) Freels, Justin ReedInfrared transition location estimates can be fast and useful measurements in wind tunnel and flight tests. Because turbulent boundary layers have a much higher rate of convective heat transfer than laminar boundary layers, a difference in surface temperature can be observed between turbulent and laminar regions of an airfoil at a different temperature than the free stream air temperature. Various implementations of this technique are examined in a wind tunnel. These include using a heat lamp as an external source and circulating fluid inside of the airfoil. Furthermore, ABS plastic and aluminum airfoils are tested with and without coatings such as black paint and surface wraps. The results show that thermal conduction within the model and surface reflections are the driving issues in designing an IR system for detecting transition. Aluminum has a high thermal diffusivity so is a poor choice for this method. However, its performance can be improved using an insulating layer. Internal fluid circulation was far more successful than the heat lamp because it eliminates the reflected IR due to the heat lamp. However, using smooth surface wraps can mitigate reflection issues caused by the heat lamps by reducing the scatter within the reflection, producing an IR image with fewer contaminating reflections.Item Non-Destructive Evaluation of Bridge Stay Cable and External Post-Tensioning Systems(2014-10-09) McCoy, Katlyn MaeNon-destructive evaluation (NDE) of bridge stay cable and external post-tensioning (PT) systems is an essential tool to thorough bridge inspections and also eliminates any necessary repair of destructions made during evaluation. Conditions such as corrosion, steel strand and wire breakage, tendon section loss, voids in the grout, water infiltration, and other undesired grout conditions can go undetected in nontransparent stay cable and external PT ducts without proper inspection. In this research, sounding, ultrasonic tomography, infrared thermography, and ground penetrating radar are evaluated for their applicability to identify selected conditions in a mock-up specimen representative of both a stay cable system and an external PT system. A borescope is also used to collect ground truth data for comparison with the NDE results. The conditions are fabricated in the mock-up specimen to closely represent conditions in the field so that the NDE results are directly applicable to bridge construction quality control and in-service bridge inspections. Locations of corrosion, breakage, and section loss are established prior to grouting. These conditions are combined with both foam void locations and an air-filled void in the grout along the top of the duct. The sounding method was extremely applicable in accurately detecting air voids in the grout and the sounding results matched closely with the ground truth data of the air void extent collected by the use of a borescope. This research concludes that the infrared thermography and ground penetrating radar devices used did not identify any of the corrosion, section loss, or breakage locations within the specimen. However, both of these methods identified air voids and foam voids in the duct free span during both the quality control testing period and inspection testing period, although GPR did not provide accurate void depth. In addition, infrared thermography was able to identify air voids within the grout caps at each anchorage end. The ultrasonic tomograph used in this research, designed for use on concrete rather than stay cables and external PT, produced inconsistent results when used on the specimen. In future research, a different means of ultrasonic tomography testing may be applicable to identifying voids in the grout.