Papers by Keyword: Nondestructive Evaluation

Abstract: This study investigates the effectiveness of a commercially available two-part fiberglass patching kit for repairing steel plates with cracks of varying sizes. The kit, produced by DuraPower Product Inc., includes a fiberglass patch, resin, and an activator, which serve as the adhesive for the repair. Four steel plates were tested: one without a crack and three with small (5 mm), medium (13 mm), and large (20 mm) cracks machined at the center. The repair process involved applying a fiberglass patch to each plate, and Non-Destructive Evaluation (NDE) using PZT-SLDV Lamb waves employed to assess the repaired specimens. The NDE results showed that the patching material significantly influenced wave energy transmission, with wave energy being more confined within the patch on the repaired surfaces. The study demonstrated that the repair process was effective in restoring the structural integrity of plates with varying crack sizes, successfully addressing defects of different lengths, and achieving good adhesion with minimal air bubble formation. This research provides valuable insights into the real-world applicability of the patching kit for repairing cracked steel surfaces.

Abstract: In-situ monitoring method of FRP (Fiber Reinforced Plastics) by built-in sensors is a key technology for developing future and high-reliable composite structures. The Rayleigh scattering-based distributed optical fiber sensor has high spatial resolution of 1mm and good embeddability into FRP and then it can be considered that the sensor is very suitable to in-situ monitoring of FRP. In the present paper, process monitoring and damage identification of FRP were conducted. In the process monitoring, flow-front of silicon oil impregnating into glass textile during VaRTM (Vacuum-assisted Resin Transfer Molding) process was measured. Comparing to visual observation results, it appeared that the maximum slope position of strain distribution showed flow-front position. In the health monitoring, damage identification of cross-ply GFRP laminates with delamination by the attached distribution optical fiber sensors was carried on. From the results, it was found that the strain varied largely on the delaminated section and then the delamination was detectable from the surface strain distribution measured by the optical fiber sensor.

Abstract: This paper deals with the design of an apparatus based on tensegrity structures for the transmission of special solitary waves with adjustable profile into a material or structure, and the detection of such waves from a material or structure. The advantages of using tensegrity building blocks in place of granular materials or different structural units for the fabrication of novel nondestructive evaluation and monitoring tools and acoustic lenses are illustrated.

Abstract: Eddy current testing and metal magnetic memory testing, cooperated with special testing devices, were applied to detect the superficial defects of old cylinder barrel. It was indicated that there were three types of the signals, which were non-defect signals, discontinuous peak signals and continuous peak signals. Non-defect signals indicated that there was no defect in cylinder barrel, and the discontinuous peak signals denoted that there was circumferential cracking, and the continuous peak signals showed that there was longitudinal cracking in the surface of cylinder barrel. The amplitude of eddy current testing signals characterizes the depth of cracking, and the gradient of magnetic signals descript the degree of stress concentration. The method mentioned above detects the cracking and stress concentration in the superficial coat of old cylinder barrel, which effectively guarantee the quality of automobile cylinder.

Abstract: In this paper, a new approach is proposed for nondestructive size determination of immersed and embedded cylindrical rods by inversion of acoustic scattering data. The normal mode expansion technique is used for modelling the scattered field. Also, the experimental backscattered field is measured using short pulse MIIR technique. The Genetic algorithm is the inversion technique used for measuring the diameters of the rods. The inversion technique matches the modelled and experimental scattered fields at resonance points, so the diameters of the rods can be estimated. The numerical results indicate that proper selection of resonance frequencies leads to accurate measurement of diameter. The proposed approach showed very good convergence and the results obtained were found to agree very well with available data.

Abstract: The tensile failure behavior of railway wheelset materials was studied with the aid of infrared thermography technology. The tensile specimens were prepared from the actual railway vehicle parts, which were used for over 20 years. Generally, the Lüders bands are appeared and observed in annealed soft steel like low-carbon steel, during yield point phenomenon due to the unbalance of strain. During the tensile testing, a high-speed infrared camera was employed to monitor surface temperature changes in specimen. During the tensile testing, the formation of Lüders bands was clearly observed. Moreover, the propagation of bands along the 45 degree direction of loading axis was also observed. In this investigation, the yield point phenomenon with Lüders band in railway wheelset materials was introduced, and the interpretation of tensile behavior was also discussed.

Abstract: Visualization of wavefield propagation has been evolving as one of the most significant nondestructive imaging methods for structural damage evaluation and shock analysis. Corresponding visualization systems that are commonly used are potentially affected by aliasing due to the nature of discrete sampling in spatial and temporal domains. This study was conducted to define the problem and produce a spatial sampling guideline for aliasing-free visualization. Experimental demonstration was given at various spatial sampling rates for comparison. The results verified that the guideline is valid and can be used for quick determination of aliasing-free spatial sampling rate prior to experiment. Special guideline for post-sampling optimization was also presented.

Abstract: In this paper, a nondestructive technique is used as a tool to control cracks and microcracks in materials. A simulation by a numerical approach such as the finite element method is employed to detect cracks and eventually; to study their propagation using a crucial parameter such as the stress intensity factor. This approach has been used in the aircraft industry to control cracks. Besides, it makes it possible to highlight the defects of parts while preserving the integrity of the controlled products. On the other side, it is proven that the reliability of the control of defects gives convincing results for the improvement of the quality and the safety of the material .

Abstract: Marine composite structures subject to dynamic loading typically incorporate more than one material type, and consist of laminate sections up to hundreds of millimetres in thickness. These solid hybrid laminates exhibit different behaviour in static and fatigue loading from thin aerospace composite laminates and sandwich structures. There is therefore a need to better understand the likely damage and degradation mechanisms that will occur in these thick structures and to concurrently develop nondestructive evaluation (NDE) technology to meet the consequent inspection problems. In this paper we present details of an ongoing fatigue program on marine composite blades. The challenges for ultrasonic NDE of thick composites, and emerging inspection methods using state-of-the-art inspection systems and analysis tools will be discussed.

Abstract: Nondestructive inspection and evaluation of welds is very important to ensure the safety of industrial products. In this study, the metal magnetic memory (MMM) and alternating current field measurement (ACFM) methods are utilized to characterize welding defects of a butt welded tubular specimen respectively. The results show that the MMM method has potentials in evaluating both early stress concentration and macro-defects but only qualitatively, while the ACFM method can provide crack depth sizing information quantitatively, suggesting that the two methods should be combined for nondestructive evaluation welding defects to improve the detection efficiency and accuracy.