Advances in applications of non-destructive testing (NDT): a review

Manufacturing defects and discontinuities in a product are anomalies which can lead to severe damages which may sometimes involve loss of life. These defects must be examined and corrected before the product goes into service. There are two methods of testing a product for defects and discontinuities viz. Destructive Testing and Non-Destructive Testing. Destructive Testing entails subjecting the product to conditions that leads to failure of the product whereas Non-Destructive Testing (NDT) is the process of examining the products for defects in a way in which it retains its usefulness for future service. This paper discusses various methods involved in NDT such as Visual Testing, Magnetic Particle Inspection, Penetrant Testing, Ultrasonic Testing, Radiographic Testing, Acoustic Emission and Eddy Current Testing with a major focus on  advances in the applications of NDT

Bridges Structural Health Monitoring and Deterioration Detection Synthesis of Knowledge and Technology

INE/AUTC 10.0

GPR investigations for the study and the restoration of the rose window of Troia Cathedral (southern Italy)

The development of cracks and distortions caused by past seismic events compromised the integrity of the rose window of Troia Cathedral, one of the most precious Romanesque monuments in southern Italy. Ground-penetrating radar (GPR) using high-frequency antennae (mainly 1500 MHz) was selected from among various non-destructive testing methods for its high-resolution imaging to scan the internal structure of the various architectural elements of the wheel window: the decimetre-diameter columns constituting the rays, the ring decorated with intersecting arched ribwork and the surrounding circular ashlar curb. GPR was employed in the classical continuous reflection mode, moving the antennae manually along the architectural elements and paying exceptional care in the acquisition and processing stages to avoid positioning errors. Indeed, the challenging aspects of this case study were the geometrical complexity and small dimensions of the structural elements, causing many logistic/coupling problems. In spite of this, through proper interpretation techniques, based on signal analysis (presence of reflections and diffractions, velocity and attenuation variations) and correlation with features detected by visual inspection of the external surfaces, the GPR survey provided useful information on the internal structure of the rose window, detecting fractures and the boundaries of previously restored parts and locating hidden metallic components connecting the architectural elements. Information on the internal structure and spatial distribution of metallic junctions was essential for gaining insight into building techniques in order to discriminate between restoration strategies which may require either total or partial dismantling of the rose window. GPR results provided crucial evidence in favour of one of the (conflicting) hypotheses about the original building techniques, leading to the selection of partial dismantling as the most suitable restoration strategy. Analysis of measurements revealed the potential of GPR in the field of cultural heritage restoration, even in those cases characterized by complex geometry, structural brittleness and logistic difficulties, such as that discussed in this paper

Part1: Masonry Arch Bridges

This textbook has been written to provide civil and structural engineering students and professionals with background information needed to test and assess masonry arch bridges with the help of non-destructive tools. This textbook focuses on methods of Non-Destructive Testing (NDT) for railway masonry arch bridges primarily but the methodology described can be used on highway structures as well. Various NDT methods are shown and compared considering several aspects such as cost efficiency, reliability of measured data, easiness of implementation, level of disturbance to traffic, etc. The principles of the methods and the required equipment for their use are briefly described. Results of field tests are discussed that were performed by the Structural Diagnostics and Analysis Research Group of the University of Pécs in co-operation with Eötvös Loránd Geophysical Institute and ORISOFT Engineering Consulting Ltd., Hungary. The text also includes descriptions of investigations and experiences gained by tests carried out at European railway administrations Special attention is given to and detailed guidance is provided in this document on the following methods: georadar, seismic tomography, infrared thermography and boroscopy. This textbook should be considered as an initial document, as it does not fully explore the full range of possibilities for non-destructive inspection of arch bridges. These techniques constitute a continuously developing topic that still require a great deal of research. It is also recommended therefore that students become thoroughly familiar with the most current recommended practices as well. The author hopes that this textbook will interest a new generation of young people in considering their careers in bridge engineering and non-destructive testing of historical structures

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

Review on Strain Monitoring of Aircraft Using Optical Fibre Sensor

Structural health monitoring of aircraft assures safety, integrity and reduces cost-related concerns by reducing the number of times maintenance is required. Under aerodynamic loading, aircraft is subjected to strain, in turn causing damage and breakdown. This paper presents a review of experimental works, which focuses on monitoring strain of various parts of aircraft using optical fibre sensors. In addition, this paper presents a discussion and review on different types of optical fibre sensors used for structural health monitoring (SHM) of aircraft. However, the focus of this paper is on fibre bragg gratings (FBGs) for strain monitoring.  Here, FBGs are discussed in detail because they have proved to be most viable and assuring technology in this field. In most cases of strain monitoring, load conditioning and management employs finite element method (FEM). However, more effort is still required in finding the accurate positions in real time where the sensors can be placed in the structure and responds under complex deformation

APPLICATION OF LASER SCANNING SURVEYING TO ROCK SLOPES RISK ASSESSMENT ANALYSIS

The methods for understanding rock instability mechanisms and for evaluating potential destructive scenarios are of great importance in risk assessment analysis dedicated to the establishment of appropriate prevention and mitigation actions. When the portion of the unstable rock mass is very large, effective actions to counteract the risks are complex and expensive. In these conditions, an optimal risk management cannot ignore procedures able to faster and accurately acquire i) geometrical data for modeling the geometry of the rock walls and implementing reliable forecasting models and ii) monitoring data able to describe the magnitude and the direction of deformation processes. These data contributes to the prediction of the behavior of a landslide if the measurements are acquired frequently and reliable numerical models can be implemented. Innovative geomatic techniques, based on GPS, Terrestrial Laser Scanning Surveying (TLS), automated total station and satellite and ground SAR Interferometry, have been recently applied to define the geometry and monitoring the displacements of unstable slopes. Among these, TLS is mainly adopted to generate detailed 3D models useful to reconstruct rock wall geometry by contributing to the estimation of geo-mechanical parameters, that is orientation, persistence and apparent spacing of rock discontinuities. Two examples of applications of TLS technique to the analysis of a large front in a quarry and of a rock shoulder of a dam are presented