Development Of Non-destructive Testing Techniques Research Articles

Nanoscale Gd2O2S:Tb Scintillators for High-Resolution Fluorescent Imaging of Cold Neutrons

Cold neutron has a strong ability to penetrate metal materials and identify light elements, making it an ideal nondestructive testing technique for detecting cracks, bubbles, or other defects in metals. However, the low imaging resolution and detection efficiency of scintillators limit the application of cold neutron technology in imaging. The particle size and luminescence properties of scintillator materials have an important influence on the spatial resolution and detection efficiency of cold neutron radiography. Here, we report a series of NaF-doped Gd2O2S:Tb3+ (NaF-d-GOS:Tb) scintillators with adjustable particle size, which were prepared through a two-step method of solution precipitation followed by solid-phase vulcanization calcination. It was found that the NaF-d-GOS:Tb scintillators showed the highest quantum yield, reaching up to 62.94%. They were applied to fabricating cold neutron ultrathin screens. The resolution can reach 12 μm in the cold neutron imaging system. These NaF-d-GOS:Tb scintillators with excellent fluorescence facilitate the development of nondestructive testing techniques based on cold neutron imaging.

Development of nondestructive testing technique for adhesively bonded materials based on thermographic transient temperature measurement after pulse heating and data analysis

Currently, the automobile industry is promoting weight reduction of car bodies by using high-strength thin steel sheets to improve fuel efficiency. On the other hand, since the rigidity of high-strength steel sheets alone is reduced, the weld bond method is attracting attention as a way to compensate for this. The weld bond method is a joining method that uses both adhesives and spot welding to improve the rigidity of steel plates while keeping them lightweight. The weld bond method can improve the rigidity only when the adhesive is applied to the required area. In this study, a new non-destructive inspection method using infrared thermography is developed as a high efficiency and high quality inspection method. The adhesive section is detected by measuring the difference in temperature fluctuation between the adhesive and non-adhesive section that occurs after heating the inspection target. However, the adhesive cannot be detected clearly with the time-series infrared data measured by temperature fluctuation. To solve this problem, we proposed PCA processing for time-series infrared data. The PCA process extracts each of the feature values present in the data as independent variables, and the changes in the feature values can be confirmed by images. It was found that the adhesive section, which cannot be confirmed by the infrared temperature image, can be clearly detected by the PCA processing.

SOME RESULTS OF STUDIES OF THERMAL FIELDS OF CARBON YARNS

In the present work, a study of the thermal properties of a carbon yarn was carried out. Were obtained different thermal fields at different structures of the carbon yarn. It was found that thermal fields are highly heterogeneous in the presence of defects in the form of nodes. The novelty of the work is the synthesis of the structure of the cross-section of a carbon yarn using fractal geometry methods. The results of the work can be used in the development of non-destructive testing techniques and in the design of woven electric heaters

Non-destructive testing and evaluation of composite materials/structures: A state-of-the-art review

Composite materials/structures are advancing in product efficiency, cost-effectiveness and the development of superior specific properties. There are increasing demands in their applications to load-carrying structures in aerospace, wind turbines, transportation, medical equipment and so on. Thus, robust and reliable non-destructive testing of composites is essential to reduce safety concerns and maintenance costs. There have been various non-destructive testing methods built upon different principles for quality assurance during the whole lifecycle of a composite product. This article reviews the most established non-destructive testing techniques for detection and evaluation of defects/damage evolution in composites. These include acoustic emission, ultrasonic testing, infrared thermography, terahertz testing, shearography, digital image correlation, as well as X-ray and neutron imaging. For each non-destructive testing technique, we cover a brief historical background, principles, standard practices, equipment and facilities used for composite research. We also compare and discuss their benefits and limitations and further summarise their capabilities and applications to composite structures. Each non-destructive testing technique has its own potential and rarely achieves a full-scale diagnosis of structural integrity. Future development of non-destructive testing techniques for composites will be directed towards intelligent and automated inspection systems with high accuracy and efficient data processing capabilities.

A study on behavior of steel structures subjected to fire using non-destructive testing

Due to its earthquake resistant properties, most building structures are constructed with reinforced concrete on a steel structure. As the temperature of steel increases especially during a fire, it will reduce the strength of a structure. Since the properties of steel, such as the Young’s modulus and yielding strength, drop rapidly with increasing temperature, during a fire the load capacity of such structures will decline dramatically. However, it is important to evaluate the structural performance of steel frames after a fire for reuse and reconstruction due to the high cost of reconstructive building. This study is concerned with the development of nondestructive testing techniques to investigate the structural behavior of steel subjected to fire. The results of ultrasonic wave speed measurement show that heating up to 1000°C and cooling by water produces a large change in wave speed. Under metallurgical microscope observation, the texture could be seen to have changed into bainite and martensite. In the study, the properties of the structure became hard and brittle due to phase change.

Impact non-linear reverberation spectroscopy applied to non-destructive testing of building materials

The development of non-destructive testing techniques to detect early micro damage in concrete and other building materials is important for efficient maintenance and management of existing infrastructure. Nonlinear acoustic methods have shown potential for the identification of early damage in brittle materials such as concrete. Commonly, these methods evaluate relative nonlinearity parameters from multiple resonance tests at different amplitudes. We demonstrate a recently developed alternative method, Impact Nonlinear Reverberation Spectroscopy (INRS), where quantitative nonlinearity parameters are evaluated from a single impact resonance test. The recorded reverberation of the measured signal is matched to a synthetic nonlinear damped signal. The proposed model allows instantaneous true physical amplitude, frequency, and damping of each mode to be characterized as a function of time, allowing for quantitative information of the nonlinear parameters. The hysteretic material nonlinearity can be quantitatively characterized over a notably wider dynamic range compared to conventional methods. Two examples from the application to concrete and stabilized soil are presented. In addition quantitative values of the hysteretic nonlinear parameter from stabilized soil samples are compared with the measured ultimate compressive strength of each sample.

Developments in NDT for Detecting Imperfections in Friction Stir Welds in Aluminium Alloys

Friction stir welding (FSW) has dramatically changed how aluminium alloys can be welded. The quality of FS welds is usually excellent, but some imperfections periodically occur. The geometry, location, and microstructural nature of these imperfections bear no resemblance to the imperfections typically found in aluminium fusion welds. Consequently, it has been difficult to identify FS weld imperfections with common non-destructive testing (NDT) techniques. Therefore, further development of NDT techniques must be done to enable the detection of FS weld imperfections. This paper presents an integrated, on-line, NDT inspection system for FS welds, which employs a data fusion algorithm with fuzzy logic and fuzzy inference functions. It works by analyzing complementary and redundant data acquired from several NDT techniques (ultrasonic, Time of Flight Diffraction (ToFD), and eddy currents) to generate a synergistic effect that is used by the software to improve the confidence of detecting imperfections. The system was tested on friction stir welded AA5083-H111 specimens. The results indicate that by combining the output from various NDT processes, an improvement in finding imperfections can be obtained compared to using each NDT process individually. The methodology implemented in the QNDT_FSW system has given good results and improved reliability in the NDT of friction stir welds.

Development of Nondestructive Testing Technique for Concrete Structure Using Active Thermal Stimulation

Development of Nondestructive Testing Technique for Concrete Structure Using Active Thermal Stimulation

The effects of penetrating radiations on materials

This paper contains an elementary account of the changes produced in solids by irradiating them with fast particles. One aspect of this work is the investigation of the properties of various types of lattice defect produced by irradiation. An advance in understanding this subject will also help in the further development of non-destructive testing techniques.