Papers by Keyword: NDE (Nondestructive Evaluation)

Abstract: Industries such as gas, oil, petrochemical, chemical, and electric power have generally employed for the operation and used to enlarge the equipment or structures that require a high capital investment. In order to meet these requirements, the industries are increasingly moved toward saving the experimental verifications and computer simulation. Therefore industries to reduce the maintenance costs without compromising operational safety have been forced on finding better and more efficient methods to inspect their equipment and structures. It was motivated to meet the industrial needs and to secure and maintain the institute's technical initiative and leadership in the development of this new and exciting technology. Also, the system with many sensors could be detected the weld defects, and was useful for real-time monitoring. This paper is focused on the development of the real-time non-contract monitoring system as an efficient tool for the experimental study of weld defects based on the relationship between the measured voltage and input parameters. The monitoring technology involves the use of Ms S (Magnetostrictive Sensors) for the generation and detection of the guided waves. The developed system was employed to the experimental study in order to fine the weld defects for steel object with artificial defects used in the welding field.

Abstract: Recently, a new ultrasonic CT system has been developed as the NDE method suitable for wood. In this system, several characteristics related to the ultrasound traveling in the woods such as the anisotropy of woods, existence of immature woods and ultrasound diffraction in the woods are considered during image composition process. In this study, we inspected the system that had been newly developed for the decayed wood specimen. We performed the ultrasound measurements to reconstruct the CT image. And then, we verified the distributions of each characteristic in the section by measuring the moisture content, specific gravity and compressive strength after cutting the measured specimen by small specimen again. The acquired results are compared with the CT image acquired in the same section. As a result, it is determined that it is possible to detect the locations and sizes of decayed parts in the wood by using the developed ultrasound CT system. In particular, the results show that the initial decays that the weight loss rate is less than 10% and the strength loss rate is less than 30% are also detectable.

Abstract: This research was carried out to grasp the factors influencing to the ultrasonic velocity to improve the efficiency of the ultrasonic wave test using as the method of NDE of wood. However, it was difficult to detect the defect of wood accurately, because ultrasonic velocity is influenced by various factors. So, some effect factors, which were not concerned with decay, were confirmed at first. Therefore, in this research, we tried to find the factors which affect on the natural characters and the ultrasonic velocity at decayed wood, additionally, we tried an anatomic experiment and analyze. As a result of research, the velocity at radial direction was faster than that at tangential direction and the ultrasonic velocity at immature wood and reaction wood was slower than that at normal wood. And the ultrasonic velocity was more the slower at bigger the length of decay and reduction of weight.

Abstract: NDE (Nondestructive Evaluation) of wood was performed using X-ray CT technique in order to determine the applicability of this technology to ancient wooden buildings in the field. Two main objectives were studied to consider applicability as well as accuracy. First, the most suitable number of radiographs for reconstructing proper X-ray CT images was determined. Secondly, X-ray CT images using SIRT were reconstructed using various numbers of radiographs in order to consider the possible effects of absent projection data in field applications. As a result of this study, 9 radiographs were determined to be the most suitable number for this application. Brown-rotted part in wood was also detected by X-ray CT images using 9 radiographs. It was concluded that even there exists some absent projection data, CT images can be reconstructed with high accuracy.

Abstract: A PC controlled food contaminant detection system for practical use was designed and constructed. The system we have developed is the High-Tc SQUID based system, which is covered with waterproof stainless steel plates and acceptable to HACCP (Hazard Analysis and Critical Control Point) program. The outer dimension of the system is 1500L mm x 477W mm x 1445H mm and the acceptable object size is 200W mm x 80H mm. This system employed a double-layered permeable metallic shield with thickness of 1 mm as a magnetically shielded box. The distribution of the magnetic field in the box was simulated by FEM; the gap between each shield layer was optimized before fabrication. Then the shielding factor of 732 in Z-component was achieved. This value is good enough to operate the system in a factory. As a result, we successfully detected a steel ball as small as 0.3 mm in diameter with a distance of 75 mm.

Abstract: Nondestructive evaluation of tightly closed small cracks in carbon steel has been investigated under no load conditions. The investigation has been carried out by using a new ultrasonic method of testing, which has the capability of dealing with smaller tight cracks sensitively. Tight closure of small fatigue cracks in carbon steel plates is realized when the measured responses are compared with the calculated responses of the identical open cracks. Highly sensitive characteristic of the present method is verified through the comparison of the results with those obtained by the standard ultrasonic method of testing.

Abstract: As cMUTs (capacitive Micromachined Ultrasonic Transducer) offer numerous advantages over traditional transducers in terms of efficiency, bandwidth, and cost, they are expected to replace piezoelectric transducers in many applications. In particular, 2D-array cMUTs have aroused great interest in the medical engineering society because of their ability to materialize a true volumetric ultrasonic image. In this study, single element cMUTs with 32 x 32 and 64 x 64 cells were successfully fabricated. The diameter and thickness of the membrane are 35
and 1000 nm, respectively, with a sacrificial layer thickness of 600 nm. The electric characteristics of the fabricated cMUT were measured. Tests on the efficiencies of the cMUT in terms of wave generation and in terms of detection according to the bias and pulse voltage were performed in an air atmosphere.

Abstract: Any NDE process may be considered to involve three systems, each having a unique set of parameters that define its characteristics viz. (a) The Input to the material, (b) The material itself, and (c) The output response measured by the NDE system. Traditionally, the input and the material parameters are assumed known and numerous Forward Models have been developed that predict or estimate the output response function. Over the years, forward models are very well established and serve the key purpose, for improved interpretation of the, as well as to optimize the input parameters to obtain the desired, output response. The other two scenarios i.e. if the output response function in the form of measured data is available, to obtain one of system parameters, i.e. either the input function or the material properties, while the other one is assumed to be known are classified as Inverse Problems. Due to the availability of computational resources, the inverse problem solutions are becoming increasingly feasible. Typical applications include measurement of material properties such as modulus, viscosity, temperature, hardness and stress profiles, etc. This paper will discuss the different techniques and the kinds of problems that have been successfully addressed in the area of NDE and their implications on the expanding horizons in NDE.