Browsing by Subject "Nondestructive testing"
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Item Application of a non-invasive scheme to detect geometrical irregularities in pipelines(Texas Tech University, 2002-05) Aydin, Bumin KaanThe purpose of the experiments performed is to investigate a non-intrasive method to detect defects in metal pipelines. An ultrasonic echo detection scheme is used. A generator produces pressure pulses that move along the pipeline. A detector monitors the pulses moving on the pipeline. Both the generator and the detector are external to the pipe and they do not need to be in contact with the pipe. The generator is a coil wrapped around the pipe. The coil is excited with a short duration, high current pulse. The magnetic pulse generated by the current causes local compression of the pipe. This local radial compression travels along the pipe as a pulse. The detector is a capacitor formed by a copper cylinder and the pipe itself. The diameter of the pipe changes as the pressure pulse passes by. The change of the diameter of the pipe causes a voltage change of the charged capacitor, which is amplified and analyzed to find reflected waves from any discontinuities, i.e., defects due to corrosion in the pipe. The locations of the defects are found by measuring the delay of the reflected waves. Measurements have been conducted successfully and are presented.Item Evaluation of concrete structures affected by alkali-silica reaction and delayed ettringite formation(2012-08) Giannini, Eric Richard; Zhu, Jinying; Folliard, Kevin J.; Bayrak, Oguzhan; Fowler, David W.; Fournier, Benoit; Rivard, PatriceAlkali-silica reaction (ASR) and delayed ettringite formation (DEF) are expansive reactions that can lead to the premature deterioration of concrete structures. Both have been implicated in the deterioration of numerous structures around the world, including many transportation structures in Texas. As a result of considerable research advances, ASR and DEF are now avoidable in new construction, but evaluating and managing the existing stock of structures damaged by these mechanisms remains a challenge. While the published guidance for evaluating structures is very effective at diagnosing the presence of ASR and DEF, there remain significant weaknesses with respect to the evaluation of structural safety and serviceability and nondestructive testing (NDT) is a minor component of the evaluation process. The research described in this dissertation involved a wide range of tests on plain and reinforced concrete at multiple scales. This included small cylinders and prisms, larger plain and reinforced concrete specimens in outdoor exposure, full-scale reinforced concrete beams, and core samples from the outdoor exposure specimens and full-scale reinforced concrete beams. Nondestructive test methods were applied at all scales, and the full-scale beams were also tested in four-point flexure to determine the effects of ASR and DEF on flexural strength and serviceability. Severe expansions from ASR and DEF did not reduce the strength of the full-scale beams or result in excessive deflections under live loads, despite significant decreases in the compressive strength and elastic modulus measured from core samples. Most NDT methods were found to be effective at low expansions but had difficulty correlating to larger expansions. Two promising NDT methods have been identified for future research and development, and guidance regarding existing test methods is offered.Item Nondestructive evaluation of reinforced concrete structures affected by alkali-silica reaction and delayed ettringite formation(2011-08) Kreitman, Kerry Lynn; Zhu, Jinying; Folliard, Kevin J.Alkali-silica reaction (ASR) and delayed ettringite formation (DEF) deterioration have been a problem for the concrete infrastructure in the state of Texas and around the world in recent decades. A great deal of research into the causes and mechanisms of the deterioration has helped to prevent the formation of ASR and DEF in new construction, but the evaluation and maintenance of existing structures remains a problem. The goal of this research is to investigate the use of several nondestructive testing (NDT) methods to evaluate the level of ASR and DEF deterioration in a structural element. Based on the results, recommendations are made as to which NDT methods have the most potential to be incorporated into the evaluation process.Item Nondestructive Testing of Overhead Transmission Lines: Numerical and Experimental Investigation(2011-02-22) Kulkarni, Salil SubhashOverhead transmission lines are periodically inspected using both on-ground and helicopter-aided visual inspection. Factors including sun glare, cloud cover, close proximity to power lines and the rapidly changing visual circumstances make airborne inspection of power lines a particularly hazardous task. In this research, a finite element model is developed that can be used to create the theoretical dispersion curves of an overhead transmission line. The complex geometry of the overhead transmission line is the primary reason for absence of a theoretical solution to get the analytical dispersion curves. The numerical results are then verified with experimental tests using a non-contact and broadband laser detection technique. The methodology developed in this study can be further extended to a continuous monitoring system and be applied to other cable monitoring applications, such as bridge cable monitoring, which would otherwise put human inspectors at risk.Item Small fatigue crack detection using phased array technology(2012-05) Moore, Clayton; Rasty, Jahan; Ekwaro-Osire, Stephen; Chaudhuri, JharnaThe objective of this research was to investigate the applicability of a non-destructive testing (NDT) technique to detect fatigue crack initiation and propagation. A special area of interest was to determine the capabilities of ultrasonic phased array to detect small fatigue cracks under fastener heads in a two layered lap joint configuration. Mock aircraft fuselage panels were created by overlapping two 0.063 inch thick 2024-T3 aluminum plates with three rows of fasteners. These test specimens were then subjected to a cyclic tension-tension loading between 3,276 lb and 327 lb. These specimens were also inspected periodically for fatigue crack growth. It was determined that although small fatigue cracks could be detected underneath the fastener heads, their actual length could not be quantified. It was also found that small fatigue cracks could be detected only when the specimen was under a load, but when the load was removed, the cracks became undetectable with phased array inspection. This shows that phased array can be used to monitor the very early stages of fatigue crack initiation and growth underneath the fasteners of a mock aircraft fuselage lap joint.