Computational physics has become an essential research and interpretation tool in many fields. Particularly in reservoir geophysics, ultrasonic and seismic modeling in porous media is used to study the properties of rocks and to characterize the seismic response of geologic formations. We provide a review of the most common numerical methods used to solve the partial differential equations describing wave propagation in fluid-saturated rocks, i.e., finite-difference, pseudospectral, and finite-element methods, including the spectral-element technique. The modeling is based on Biot-type theories of dynamic poroelasticity, which constitute a general framework to describe the physics of wave propagation. We explain the various techniques and discuss numerical implementation aspects for application to seismic modeling and rock physics, as, for instance, the role of the Biot diffusion wave as a loss mechanism and interface waves in porous media.

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Computational poroelasticity — A review

Accelerated finite element elastodynamic simulations using the GPU

This report reviews the current state of the art of prognostics and health management (PHM) for nuclear power systems and related technology currently applied in field or under development in other technological application areas, as well as key research needs and technical gaps for increased use of PHM in nuclear power systems. The historical approach to monitoring and maintenance in nuclear power plants (NPPs), including the Maintenance Rule for active components and Aging Management Plans for passive components, are reviewed. An outline is given for the technical and economic challenges that make PHM attractive for both legacy plants through Light Water Reactor Sustainability (LWRS) and new plant designs. There is a general introduction to PHM systems for monitoring, fault detection and diagnostics, and prognostics in other, non-nuclear fields. The state of the art for health monitoring in nuclear power systems is reviewed. A discussion of related technologies that support the application of PHM systems in NPPs, including digital instrumentation and control systems, wired and wireless sensor technology, and PHM software architectures is provided. Appropriate codes and standards for PHM are discussed, along with a description of the ongoing work in developing additional necessary standards. Finally, an outline of key researchmore » needs and opportunities that must be addressed in order to support the application of PHM in legacy and new NPPs is presented.« less

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Prognostics and Health Management in Nuclear Power Plants: A Review of Technologies and Applications

Simulation of ultrasonic phased array technique for imaging and sizing of defects using longitudinal waves

The detection of defects in materials and components using ultrasonic nondestructive testing and evaluation techniques is of interest in many industrial areas. Reliable defect detection requires defined and reproducible scanning of the probes along the surface of the components. For post-processing of the recorded rf-data the Synthetic Aperture Focusing Technique SAFT has been successfully applied to improve the performance of ultrasonic testing. For specific defect and component configurations, the Time-of-Flight Diffraction technique TOFD has also been successfully applied for quantitative evaluation of crack sizes. This contribution reviews developments and applications of SAFT and TOFD with reference to representative examples from the past and the present.

Synthetic Aperture Focusing and Time-of-Flight Diffraction Ultrasonic Imaging—Past and Present

Ultrasonic time of flight diffraction (TOFD) for sizing defects is based on the time of flight of the diffracted echo that is generated when a longitudinal wave is incident on a crack tip. This technique has the limitation during near-surface inspection due to signal superposition. Here, this limitation is overcome by using the shear wave-diffracted signal (instead of longitudinal wave) and hence called S-TOFD. Experiments were conducted on samples with defect tip closer to the surface of a flat plate sample to illustrate the utility of the S-TOFD technique. An increase in the flaw sizing accuracy, by using the shear wave-diffracted echoes from the tip and through the application of a signal processing technique (ESIT), was demonstrated.

Shear-wave time of flight diffraction (S-TOFD) technique

The ultrasonic Time-of-Flight Diffraction (TOFD) technique is a well developed technique for sizing defects in thick sections (thickness >10 mm). Attempt has been made here to extend this technique for thin sections (6-10mm). An automated defect sizing algorithm using the Embedded Signal Identification Technique (ESIT) was developed for separating partially superimposed signals often encountered in thin sections and the results were compared with the manual sizing method. Both EDM notches and more realistic fatigue cracks in thin section were used to evaluate the proposed technique.

Ultrasonic TOFD flaw sizing and imaging in thin plates using embedded signal identification technique (ESIT)

The ultrasonic Time-of-Flight Diffraction (TOFD) technique is a well-known technique for defect sizing. This technique has been applied to thick sections (>15 mm). The application of the TOFD technique to thin sections like pressure vessels and piping requires simulation of this technique. Simulation gives ideas about the expected results from experiments where real experiments are not possible or are difficult to conduct. Further, simulation helps us to derive the optimum choice of experimental parameters. This paper discusses the application of the finite element technique to simulate the ultrasonic time-of-flight diffraction (TOFD) technique. The diffracted and reflected signals in TOFD techniques for vertical and inclined defects were simulated using plane strain elements. The simulated results are compared with the experimental observations. FEM simulation of wave propagation in complex joints such as a T-joint with embedded flaws is also discussed.

Simulation of the TOFD technique using the finite element method

It is necessary to size the cracklike defects accurately in order to extend the life of thin-walled (<10 mm) components (such as pressure vessels) particularly for aerospace applications. This paper discusses the successful application of ray techniques to simulate the ultrasonic time-of-flight diffraction experiments for platelike structures. For the simulation, the diffraction coefficients are computed using the geometric diffraction theory. The A and B scans are simulated in near real time and the different experimental parameters can be interactively controlled due to the computational efficiency of the ray technique. The simulated results are applied to (1) defect signal identification for vertical defects, (2) inspection of inclined defects, and (3) study the effect of pulse width or probe frequency on experimental results. The simulated results are compared with laboratory scale experimental results.

Ray based model for the ultrasonic time-of-flight diffraction simulation of thin walled structure inspection

It is necessary to size the cracklike defects accurately in order to extend the life of thin-walled 10 mm components (such as pressure vessels) particularly for aerospace applications. This paper discusses the successful application of ray techniques to simulate the ultrasonic time-of-flight diffraction experiments for platelike structures. For the simulation, the diffraction coefficients are computed using the geometric diffraction theory. The A and B scans are simulated in near real time and the different experimental parameters can be interactively controlled due to the computational efficiency of the ray technique. The simulated results are applied to (1) defect signal identification for vertical defects, (2) inspection of inclined defects, and (3) study the effect of pulse width or probe frequency on experimental results. The simulated results are compared with laboratory scale experimental results. DOI: 10.1115/1.1989353

G. Baskaran

Papers

Shear-wave time of flight diffraction (S-TOFD) technique

Ultrasonic TOFD flaw sizing and imaging in thin plates using embedded signal identification technique (ESIT)

Simulation of the TOFD technique using the finite element method

Ray based model for the ultrasonic time-of-flight diffraction simulation of thin walled structure inspection

for the Ultrasonic Time-of-Flight Diffraction Simulation of Thin Walled Structure Inspection