Cac M. Dao

Interests

Teaching

Core Courses in Civil Engineering and Engineering Mechanics. Introduction in Engineering Design. Developing Civil Engineering program at American University in Phnom Penh, Cambodia under the University of Arizona Micro-Campus Network.

Research

Ultrasonic Wave Propagation.

Courses

Scholarly Contributions

Journals/Publications

• Amjad, U., Dao, C. M., Yadav, S. K., Kundu, T., Dao, K., & Amjad, U. (2016). Advanced signal processing technique for damage detection in steel tubes. Proceedings of SPIE, 9805. doi:10.1117/12.2219417
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  In recent years, ultrasonic guided waves gained attention for reliable testing and characterization of metals and composites. Guided wave modes are excited and detected by PZT (Lead Zirconate Titanate) transducers either in transmission or reflection mode. In this study guided waves are excited and detected in the transmission mode and the phase change of the propagating wave modes are recorded. In most of the other studies reported in the literature, the change in the received signal strength (amplitude) is investigated with varying degrees of damage while in this study the change in phase is correlated with the extent of damage. Feature extraction techniques are used for extracting phase and time-frequency information. The main advantage of this approach is that the bonding condition between the transducer and the specimen does not affect the phase while it can affect the strength of recorded signal. Therefore, if the specimen is not damaged but the transducer-specimen bonding is deteriorated then the received signal strength is altered but the phase remains same and thus false positive predictions for damage can be avoided.
• Dao, C. M., Kundu, T., Das, S., & Banerjee, S. (2009). Wave Propagation In A Fluid Wedge Over A Solid Half-Space Mesh-Free Analysis with Experimental Verification. International Journal of Solids and Structures, 46, 2486-2492.
• Dao, C. M., Kundu, T., Placko, D., Ehsan, K. R., & Yanagita, T. (2010). Ultrasonic Field Modeling: A Comparison between Analytical, Semi-Analytical and Numerical Techniques. IEEE Transactions on Ultrasonics, Ferroelectric and Frequency Control, 57, 2795-2807.
• Kundu, T., Placko, D., Rahani, E. K., Yanagita, T., & Dao, C. M. (2010). Ultrasonic field modeling: A comparison of analytical, semi-analytical, and numerical techniques. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 57(Issue 12). doi:10.1109/tuffc.2010.1753
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  Modeling ultrasonic fields in front of a transducer in the presence and absence of a scatterer is a fundamental problem that has been attempted by different techniques: analytical, semi-analytical, and numerical. However, a comprehensive comparison study among these techniques is currently missing in the literature. The objective of this paper is to make this comparison for different ultrasonic field modeling problems with various degrees of difficulty. Four fundamental problems are considered: a flat circular transducer, a flat square transducer, a circular concave transducer, and a point focused transducer (concave lens) in the presence of a cavity. The ultrasonic field in front of a finite-sized transducer can be obtained by Huygens-Fresnel superposition principle that integrates the contributions of several point sources distributed on the transducer face. This integral which is also known as the Rayleigh integral or Rayleigh-Sommerfeld integral (RSI) can be evaluated analytically for obtaining the pressure field variation along the central axis of the transducer for simple geometries, such as a flat circular transducer. The semi-analytical solution is a newly developed mesh-free technique called the distributed point source method (DPSM). The numerical solution is obtained from finite element analysis. Note that the first three problems study the effect of the transducer size and shape, whereas the fourth problem computes the field in presence of a scatterer. © 2010 IEEE.
• Dao, C. M., Das, S., Banerjee, S., & Kundu, T. (2009). Wave propagation in a fluid wedge over a solid half-space - Mesh-free analysis with experimental verification. International Journal of Solids and Structures, 46(Issue 11-12). doi:10.1016/j.ijsolstr.2009.01.035
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  Interaction between a bounded ultrasonic beam and a liquid wedge over a solid half-space is studied. A semi-analytical technique called distributed point source method (DPSM) is adopted for modeling the ultrasonic field in a wedge shaped fluid structure over a solid half space. This study is important for analyzing the ultrasonic waves used for the non-destructive inspections of partially immersed structures. It is also useful for studying the effect of underwater ultrasonic or acoustic wave experiments on marine lives near the shore. The problem geometry considers a bounded acoustic beam striking a fluid-solid interface between a fluid wedge and a solid half-space at steady-state. Solution of this problem is beyond the scope of the currently available analytical methods when the beam is bounded. Only numerical method (boundary element method (BEM) or finite element method (FEM)) based packages (e.g. PZFlex) are in principle capable of modeling ultrasonic fields in such structures. At high frequencies FEM and BEM based packages require huge amount of computation memory and time for their executions that DPSM technique can avoid. Effect of the angle of strike and the fluid wedge angle variation on the wave propagation characteristics is studied. Theoretical predictions are compared with some experimental results. © 2009 Elsevier Ltd. All rights reserved.
• Dao, C. M., Das, S., Das, S., Banerjee, S., Banerjee, S., Kundu, T., Dao, C. M., & Dao, C. M. (2007). Effect of a fluid wedge on the wave propagation along a fluid-solid interface: A modeling approach. The 6th Int. Workshop on Structural Health Monitoring.
• Dao, C. M., Kundu, T., Das, S., & Banerjee, S. (2007). DPSM Modeling for Studying Interaction between Bounded Ultrasonic Beams and Corrugated Plates. IEEE Transactions on Ultrasonics, Ferroelectric and Frequency Control, 54(9), 1860-1872.
• Das, S., Dao, C. M., Banerjee, S., & Kundu, T. (2007). DPSM modeling for studying interaction between bounded ultrasonic beams and corrugated plates with experimental verification. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 54(Issue 9). doi:10.1109/tuffc.2007.470
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  Periodically corrugated structures play an important role in the field of vibration control and for designing structures with desired acoustic band gaps. Analytical solutions for corrugated plates are available for well-defined, smooth corrugations, such as sinusoidal corrugations that are not very common in the real world. Often corrugated plates are fabricated by cutting grooves at regular intervals in a flat plate. No analytical solution is available to predict the wave propagation behavior in such a periodically corrugated plate in which the equation of the plate surface changes periodically between a planar flat surface and a nonplanar parabolic groove. This problem is solved here for steady-state case by a newly developed semianalytical technique called distributed point source method (DPSM), and the theoretical predictions are compared with the experimental results generated by reflecting a bounded 2.25 MHz ultrasonic beam by a fabricated corrugated plate. The main difference that is observed in the reflected beam profile from a flat plate and a corrugated plate is that the back-scattering effect is much stronger for the corrugated plate, and the forward reflection is stronger for the flat plate. The energy distribution inside the corrugated plate also shows backward propagation of the ultrasonic energy. © 2007 IEEE.

Proceedings Publications

• Dao, C. M., Kundu, T., Amjad, U., Blase, C., Alnuami, A., & Bereiter-Hahn, J. (2018, March 4-8). Effects of transducers on guided wave based structural health monitoring. In Health Monitoring of Structural and Biological Systems XII, Ed. T. Kundu, 10600.
• Dao, C. M., Kundu, T., Amjad, U., Yadav, S. K., & Dao, K. T. (2016, March 20-24). Advanced signal processing techniques for damage detection in steel tubes. In Health Monitoring of Structural and Biological Systems X, Ed. T. Kundu, 9805.
• Dao, C. M., Thompson, D. O., Kundu, T., Das, S., Chimenti, D. E., & Banerjee, S. (2008). BOUNDED ACOUSTIC BEAM IN A FLUID WEDGE OVER A SOLID HALF SPACE: A COMBINED THEORETICAL/EXPERIMENTAL INVESTIGATION. In AIP Conference Proceedings, 975, 115-122.
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  Interaction between a bounded acoustic beam and a fluid wedge over a solid half space is studied. Nondestructive evaluation of partially immersed solids requires such investigations. Solution of this problem is beyond the scope of the currently available analytical methods. FEM based numerical techniques are also not very efficient for solving high‐frequency ultrasonic problems. A newly developed semi‐analytical technique called Distributed Point Source Method is used to solve this problem. Theoretical predictions are experimentally verified.
• Kundu, T., Banerjee, S., Das, S., & Dao, C. M. (2008). Recent developments in theoretical and experimental investigations with ultrasonic sensors. In World Forum on Smart Materials and Smart Structures Technology, SMSST 07.
• Dao, C. M., Das, S., Banerjee, S., & Kundu, T. (2007, Sept. 11-13). Effect of a Fluid Wedge on the Wave Propagation along a Fluid-Solid Interface: A Modeling Approach. In Proceedings of the 6th Int. Workshop on Structural Health Monitoring, 1, 919-926.
• Dao, C. M., Kundu, T., Banerjee, S., & Das, S. (2007, May 22-27). Recent Developments in Theoretical and Experimental Investigations with Ultrasonic Sensors. In Proceedings of the World Forum on Smart Materials and Smart Structures Technology SMSST’07.

Reviews

• Dao, C. M., Kundu, T., Banerjee, S., & Das, S. (2007. Bounded Acoustic Beam in a Fluid Wedge Over a Solid Half Space: A Combined Theoretical/Experimental Investigation. Review of Progress in Quantitative Nondestructive Evaluation, Colorado School of Mines, Golden, CO.