Browsing by Subject "NDT"

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Analysis of air-coupled system for exciting and sensing stress waves in concrete
(2014-05) Tsai, Yi-Te; Zhu, Jinying
Nondestructive testing (NDT) plays a more important role today in evaluating structural integrity of civil infrastructure. Impact-echo method (IE) is an effective stress wave based NDT method for locating defects in concrete structures. However, the contact requirement between sensor and concrete surface significantly limits the test speed and wide application of this method to large-scale structures such as bridges. Recent studies show the feasibility of air-coupled sensing, which eliminates the contact requirement and thus accelerates IE test. To further improve the test speed, a fully non-contact IE test using air-coupled sensing and excitation is investigated in this dissertation. This dissertation provides the theoretical basis required for developing an effective air-coupled IE method. For air-coupled sensing, 2D numerical simulations are first conducted to study the wave propagation in the air-solid system during IE tests. Visualized wavefield indicates that parabolic reflectors can effectively enhance the IE signal strength by focusing airborne IE waves to an air-coupled sensor. To maximize signal amplification, an analytical solution for the focused axial pressure response of a parabolic reflector with incident plane waves is derived. This solution is used to determine the reflector geometry that gives the highest focusing gain. For air-coupled excitation, a focused spark source with an ellipsoidal reflector is employed to excite stress waves in concrete. Numerical simulations and available nonlinear computer code (KZKTexas) are employed to investigate the reflector geometry that gives the highest stress wave excitation in solids. An acoustical muffler that works with the focused spark source is proposed to decrease the spark-induced noise level. The effect of source receiver spacing on received IE signals is studied. Simulated wavefield demonstrates that the mode shape of IE surface displacement distribution along the radial direction matches the Bessel function of the first kind (J0). Numerical 3D simulation results show the relation between focused IE signals and source receiver spacings, and indicate the spacing should be minimized to obtain better focused IE signal strength. Air-coupled IE test using through transmission setup is also investigated.
Controlling microstructure in nickel 200, titanium grade 2, and titanium grade 5 for the calibration of ultrasonic microstructure characterization
(2018-05) Schick, Matthew Brian; Taleff, Eric M.
Ultrasonic testing is a promising technique by which to nondestructively determine the subsurface material microstructure characteristics of metallic components. Development of this technique requires reference specimens of known microstructure by which to calibrate the ultrasonic signal response. Such reference specimens were produced in Nickel 200 (commercial-purity Ni or Ni 200), Titanium Grade 2 (commercial-purity Ti or TiGr2) and Titanium Grade 5 (Ti-6Al-4V or TiGr5) materials in the laboratory. The microstructures produced and methods of their production are presented and discussed. Particular attention is given to techniques appropriate in the general research laboratory environment. Recrystallized grain size is controlled across a wide range in the Ni 200, TiGr2, and TiGr5 materials by annealing after cold rolling. Heat treatments and hot compression further produced fully lamellar, duplex, and equiaxed (globular) microstructure forms in the TiGr5 material. The theory of ultrasonic signals interacting with grain boundaries and grain/phase interfaces will be discussed in light of the microstructures produced within these specimens
Development of a non-contact ndt system for stress wave sensing and excitation
(2014-12) Dai, Xiaowei; Zhu, Jinying
Non-destructive testing (NDT) plays an important role today in condition assessment of civil infrastructure. Among these NDT methods, the Impact-Echo (IE) method is widely used to determine the thickness of a plate structure and locate delaminations in concrete. The conventional IE test uses a contact impact source and a contact sensor, which limits the scanning speed. Recent studies show the feasibility of applying the air-coupled sensing technology to the IE test. With the contact requirement eliminated, a fully air-coupled NDT system can be realized to achieve rapid scanning on large scale structures. In this dissertation, the air-coupled IE test is first simulated using 2D finite element models. The numerical simulation results are validated by experimental measurements. It is shown that the airborne IE mode is a quasi-plane wave in air. A parabolic reflector is proposed to focus the airborne IE wave and amplify the air-coupled IE test signals. The focusing effect is validated by experimental results. By applying a parabolic reflector to the air-coupled sensor, it is found that large sensor lift-off height and source-receiver spacing can be used in the air-coupled IE test. The geometry of the parabolic reflector and source-receiver spacing are optimized using numerical simulations. A focused spark source is proposed as a non-contact source for the fully air-coupled test system. The spark source is first calibrated in an anechoic chamber. The feasibility of using the focused spark source for stress wave excitation is validated by experiments. A fully air-coupled testing system is realized by combining the air-coupled sensor and the air-coupled source. Experimental studies show that this system can measure surface wave and the IE mode. The fully air-coupled system is tested using a conventional IE test setup and a through transmission test setup. An acoustic muffler is introduced to suppress the acoustic noise from the spark source. Several advanced signal processing techniques to reduce the acoustic noises are also investigated. The air-coupled sensor has been adopted on a crawler NDT system for concrete inspection in a noisy field environment.
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, Patrice
Alkali-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.
Evaluation of crack depth in concrete using non-contact surface wave transmission measurement
(2011-05) Kee, Seong-Hoon; Jinying Zhu; Jirsa, James O.; Bayrak, Oguzhan; Folliard, Kevin J.; Stokoe II, Kenneth H.; Wilson, Clark R.
The purpose of this study is to develop a non-contact air-coupled NDT method to identify and characterize surface-breaking cracks in concrete structures using surface wave transmission measurements. It has been found that the surface wave transmission (SWT) across a surface-breaking crack is related to the crack depth. However, inconsistence was noticed in surface wave transmission measurements. In this dissertation, the author first summarized limitations of the current SWT method for application to concrete structures, which include inconsistent sensor coupling, near-field effect of sensors, effects of crack width, external loading effect on surface wave transmission coefficient, and lack of a repeatable source. In this dissertation, the author attempts to find solutions to the aforementioned problems. First, non-contact air-coupled sensors were applied to the SWT method to reduce experimental errors caused by inconsistent coupling condition of conventional contact sensors. Air-coupled sensing enables reliable and consistent results, and significantly improves test-speed. Results from laboratory and field tests demonstrate effectiveness of air-coupled sensors. Second, appropriate sensor-to-source configurations are proposed to reduce undesirable effects: (i) the near-field effect of sensors around a crack, and (ii) contribution of multiple modes in a plate-like structure with a finite thickness. Near-scattering of surface waves interacting with a surface-breaking crack was investigated using numerical simulations (finite element method) and experimental studies over a wide range of the normalized crack depth (h/λ: crack depth normalized by wavelength of surface waves) and the normalized frequency-thickness ratio (f-H/CR: frequency-thick normalized by Rayleigh wave speed). Third, effects of external loadings on transmission coefficient of surface waves in concrete were investigated through a series of experimental studies. In the research, variation of the transmission coefficient is presented as a function of crack mouth opening displacement (CMOD). This provides a guideline on minimum CMOD to which the SWT method can be reasonably applied. In addition, the author experimentally demonstrates that using low-cost piezoceramic sensors is effective in generating consistent stress waves in concrete. Finally, the author demonstrates that the air-coupled SWT method developed in this study is effective for in-situ estimates of a surface-breaking crack in large concrete structures.
Ultrasonic inspection of lithium-ion batteries for early detection of thermal runaway
(2022-05-02) Neath, Barrett James; Haberman, Michael R. (Michael Richard), 1977-; Ezekoye, Ofodike A.
As efforts to establish a clean, renewable energy infrastructure are growing, the demands for safe and reliable energy storage systems are growing as well. Despite their widespread application in low-power consumer electronics, lithium-ion batteries are struggling to match the performance needs required for high-power applications, including electric vehicles and grid energy storage. At the same time, traditional battery management systems (BMS) relying solely on voltage, current, and temperature measurements have failed to keep up with the dynamic needs of the industry, and, as a result, the electric vehicle market has been plagued by headlines of lithium-ion battery fires and explosions. Therefore, in order to ensure the safety and reliability of lithium-ion battery systems in high-power applications, accurate health monitoring for catastrophic failure prevention is of the utmost importance. This thesis explores the viability of ultrasonic inspection for early damage detection in cells undergoing thermal abuse. Specifically, initial studies are reported on the use of ultrasonic wave measurements for detection of cell damage while simultaneously monitoring voltage, current, temperature, and mechanical clamping force under varying electrical, mechanical, and thermal loading conditions. Time- and frequency-domain features of the acoustic signals are monitored for excitation frequencies of 0.1–1 MHz transmitted along two propagation paths. Correlations between changes in time of flight and signal amplitude with variations in electrical, mechanical, and thermal loading conditions are presented for cells subjected to electrochemical cycling and thermal abuse scenarios. Early ultrasonic indicators of damage evolution in the cells are presented, compared with traditional detection methods, and discussed with respect to excitation frequency, propagation path, and known damage mechanisms in lithium-ion batteries. The results presented in this work highlight the ability of ultrasonic waves to detect internal mechanical changes during battery operation and illustrate the predictive capability of ultrasonic inspection for damage detection up to thirty minutes in advance of cell rupture.