Delamination detection in composite plates by synthesizing time‐reversed Lamb waves and a modified damage imaging algorithm based on RAPID

The amount and variety of composite structures that need to be inspected for the presence of impact damage has grown significantly in the last few decades. In this paper, an application of a probabilistic ultrasonic guided wave imaging technique for impact damage detection in carbon fiber-reinforced polymers (CFRP) is presented. On the one hand, a linear, baseline-dependent, technique utilizing the well-known correlation-based RAPID method and an array of piezoelectric transducers is applied to detect impact-induced damage in plate-like composite structures. Furthermore, a baseline-independent nonlinear extension of the standard RAPID method is proposed, and its performance is demonstrated both numerically and experimentally. Compared to the conventional RAPID, the baseline-free version suffers from a somewhat lower imaging quality. However, this drawback is compensated by the fact that no damage-free (intact) baseline is necessary for successful imaging of damage.

https://www.mdpi.com/1996-1944/9/11/901/pdf

Linear and Nonlinear Guided Wave Imaging of Impact Damage in CFRP Using a Probabilistic Approach.

Ultrasonic guided waves have been proven as a promising tool for structure health monitoring due to their capability of interrogating a large structure from a single transducer position. This study presents the guided wave tomographic imaging in structural health monitoring for detecting cracks and visualization by reconstruction algorithm for the probabilistic inspection of damage. The variable shape factor is suggested for quantitative defect shape and sizing by reconstruction image. The defect of irregular boundary imaging with variable shape factor is precisely reconstructed by advanced RAPID algorithm with limited number of transducers. The particular application of interest is defect imaging of symmetric wave modes with irregular shape defect in plate-like structures. A preliminary study of tomographic imaging by guided waves in a plate-like structure provides guidelines for the quantitative defect imaging.

Quantitative tomographic visualization for irregular shape defects by guided wave long range inspection

Ultrasonic guided wave tomography provides an imaging potential over a hidden and inaccessible damage zone. The use of shear horizontal guided waves has been proposed as an attractive technique for surface defect characterization. In this study, the quantification and imaging of corrosion wall thinning in a plate are investigated by using shear horizontal guided waves. Simulations of shear horizontal wave propagation in the specimens using hybrid boundary element method are studied in this paper. Magnetostrictive patch transducers are designed to generate and measure the shear horizontal wave mode experimentally. The quantification via imaging of wall thinning is achieved by a modified reconstruction algorithm for the probabilistic inspection of damage tomography algorithm. The comparisons of the imaging obtained by modeling data and experimental ones of defects with different shapes in the specimens are presented in this paper. The results obtained by experimental tests are comparable with that produced by boundary elements method. The present approach provides an alternative tool, that can be applied to detecting, locating and imaging the wall thinning defects in plate-like structures.

Quantification and imaging of corrosion wall thinning using shear horizontal guided waves generated by magnetostrictive sensors

The utility of those waves propagating over a distance, called “guided waves,” provides abundant technical advantages in a variety of nondestructive evaluation (NDE) applications. In recent years, the field has rapidly grown as one of the most noticeable subjects in the NDE community, from not only the academic but also the practical standpoint, representing promising technological transfer. A number of commercialized inspection units and techniques are already available on the market. However, the principle of guided waves physics, which is crucial for proper usage and subsequent data analysis of the equipments has not been fully elucidated for field NDE engineers, and has mainly been set out for the purpose of simplifying the operation scheme. A simplified operation manual is necessary to bolster the market, but is quite often not sufficient to conduct the mission adequately. Do NDE engineers no longer need to understand guided wave physics? The knowledge on guided wave physics and advanced softwares are battling against the challenging task to turn the technique from magic to a reliable engineering tool. In this sense, the guided wave NDE technique now requires us to establish a firmer physical foundation, whereby its sophisticated features are understood, to enrich utility and correct the improper usage of field data; meanwhile, the instrumentation is rapidly being upgraded with more advanced functions. In this paper, the importance of a physical understanding of the characteristics of guided wave NDE is firstly addressed. Guided wave models can enhance NDE performance and alleviate the likelihood of a false call. Scattering of surface waves by a two-dimensional corrosion pit at the surface of a homogenous, isotropic, linearly elastic half-space is theoretically investigated in Sect. “A Guided Wave Measurement Model for Scattering of Surface Waves by a Corrosion Pit Based on the Use of the Elastodynamic Reciprocity”. In Sect. “Model-Based Visualization of Defects Using Tomography”, guided wave tomographic imaging of plate-like structures is presented using a probabilistic algorithm. Section “The Model-Based Guided Wave Focusing Technique to Improve Sensitivity” shows that the guided wave focusing technique can be used to focus energy in both the circumferential and axial directions in pipes. The unique nonlinear features among different guided wave modes, which can be used to choose a proper mode with better sensitivity for micro-damage detection, are reported in Sect. “Model-Based Nonlinear Guided Wave Techniques for Micro-Damage Detection”.

/pdf/model-based-guided-wave-nde-the-evolution-of-guided-wave-nde-3bdos634wf.pdf

Model-Based Guided Wave NDE: The Evolution of Guided Wave NDE from “Magic” to “Physically Based Engineering Tool”

A non-contact testing with laser generated ultrasonic transmitter and an air-coupled transducer is very attractive technique in guided wave inspection. It can be used for online inspection and structural health monitoring (SHM) where contact method with embedded sparse sensors can not be applied such as the case of high temperature application. In this paper, tomography based on probabilistic algorithm was employed in conjunction with the hybrid non-contact method. This present approach can be successfully used for detecting, locating and imaging multi-defect in plates. This algorithm is based on the use of signal difference coefficient of guided waves acquired for good and faulty conditions. The simplicity of this algorithm makes it suitable to be implemented to non-contact based online inspection scheme. [doi:10.2320/matertrans.I-M2011853]

Non-Contact Guided Waves Tomographic Imaging of Plate-Like Structures Using a Probabilistic Algorithm

A hybrid non‐contact testing with laser generated ultrasonic transmitter and an air‐coupled transducer is very attractive technique in guided wave inspection. It can be used for online inspection and structural health monitoring (SHM) where contact method using embedded sparse sensors can not be applied such as the case of high temperature application. In this study, a tomography based on probabilistic algorithm was employed in conjunction with the hybrid non‐contact method. This present approach can be successfully used for detecting, locating and imaging multi‐defect in plates. The probabilistic algorithm is principally based on the use of signal difference coefficient of guided waves acquired for good and faulty conditions. The simplicity of this algorithm makes it suitable to be implemented to non‐contact based online inspection scheme.

Hybrid non‐contact guided wave tomography for imaging of defects in plate‐like structure using a probabilistic algorithm

A failure analysis of ammonia converter which suffered hydrogen attack in two years since its initial operating time was presented. It is constructed from 2.25 Cr?1 Mo steel. Analysis showed that the failure on closing seam weld joint was due to local improper post weld heat treatment (PWHT). Improper PWHT can introduce high residual stresses in thick-walled pressure vessel. High residual stress level in weld joint is very prone to hydrogen attack for any components which are operating in hydrogen gas environment. The repair procedures based on the principle to decrease the residual stress then proposed. The repair was controlled very carefully by applying several nondestructive tests in the each stage of repair. To assure the successful of the proposed repair, after one year since repair time, high temperature ultrasonic and TOFD methods were applied on-stream to this equipment in order to evaluate its post repair condition. The two methods showed good results on the repaired area.

Farabirazy Albiruni

Papers

Non-Contact Guided Waves Tomographic Imaging of Plate-Like Structures Using a Probabilistic Algorithm

Hybrid non‐contact guided wave tomography for imaging of defects in plate‐like structure using a probabilistic algorithm

Failure of Ammonia Synthesis Converter Due to Hydrogen Attack and Its On-Stream Assessment Using ToFD Method