Recent Advances in Non-stationary Thermal Non-destructive Characterization

Thermal wave imaging is one of the widely used non-destructive testing and evaluation (NDT&E) methods for detecting subsurface defects in most of the solids. Presently, three different active thermographic techniques are predominantly in use : Pulsed Thermography(PT), Lock-in Thermography(LT) and Pulsed Phase Thermography(PPT).To overcome some of the limitations of these widely used conventional thermographic techniques (requirement of high peak power and long experimentation time), present work focuses on recently proposed non-stationary thermal exci-tation technique for non destructive testing. This present paper highlights advantages and limitations of the prop-osed method by comparing with the conventional thermo-graphic methods

Applications of Infrared Thermography for Non-destructive Characterization of Concrete Structures

Usage of reinforced concrete structures has very long tradition in infrastructure industry due to their low cost, high strength, robustness, sustainability along with the easy availability of raw materials. However, they also have some drawbacks such as poor tensile strength and ductility, which leads to the formation of cracks in the structures. These cracks may cause penetration of chlorides, resulting into corrosion in the reinforcement. Quality control, maintenance and planning for the restoration of these structures demands a suitable non-destructive testing and evaluation method for wide-area monitoring to detect the hidden corrosion of the rebar at an early stage. Infrared thermal wave imaging has emerged as a viable technique for non-destructive testing and evaluation of reinforced concrete structures due to its full-field, remote, fast inspection capabilities to monitor the sub-surface rebar corrosion. Among the various thermal non-destructive testing techniques the present chapter proposes a novel aperiodic thermal wave imaging technique named as Gaussian windowed frequency modulated thermal wave imaging for testing and evaluation of rebar corrosion in concrete structures

Complementary Coded Thermal Wave Imaging Scheme for Thermal Non-Destructive Testing and Evaluation

Abstract Active InfraRed Thermography (IRT) is an emerging technique in the field of Non-Destructive Testing and Evaluation (NDT&E). In recent years, pulse compression supportive techniques and associated data processing schemes have been proposed by various research groups to enhance the inspection capabilities of these techniques as well as to make the experimentation simple and more reliable. This paper exploits a suitable complementary coded excitation for thermal NDT&E along with the associated pulse compression favorable data processing scheme. The proposed scheme has been implemented on a metallic sample in order to test its capabilities for subsurface defect detection and characterization

Frequency Modulated Infrared Imaging for Non-Destructive Testing of Steel Materials

Infrared non-destructive evaluation (IRNDE) is an emerging approach for non-contact inspection of various solid materials such as metals, composites and semi-conductors for industrial and research interest. This paper focuses on the inspection of plain carbon steel materials, which are widely used, particularly in the power and steel industries. This paper describes some appl-ications of recently proposed pulse compression based approach to the inspection of steel specimens. Present work highlights both phase and correlation based appro-aches for defect detection using frequency modulated thermal excitation scheme and comparison has been made on these proposed schemes

Coded Excitation for Infrared Non-destructive Testing of Steel Materials

Extensive use of steel materials in numerous applicat-ions necessitates reliable non destructive testing proc-edures for their thorough evaluation. Infrared therm- ography has been proved as a promising evaluation method for characterization of these materials due to its whole field, fast and remote inspection capabilities. But lower power distributed to high frequencies in pulsed thermo-graphy and long repetitive experimentation of lock-in thermography limits conventional thermographic methods, which demands an efficient processing methodology for detection of subsurface anomalies located at different depths with moderate peak power heat sources in limited span of experimentation time. This paper highlights the applicability of digitized frequency modulated thermal wave imaging for defect detection in mild steel materials and provides a theoretical insight for the proposed technique. In addition, detection capability of the tech-niques has been compared with conventional phase based approach by taking signa