Nondestructive Inspection System Research Articles

中性子／γ線複合型核検知システム開発の現状 IV

中性子／γ線複合型核検知システム開発の現状 IV

Impedance Measuring to Detect Fractures in Steel Frames Using Resonance Circuit on Fire Resistive Covering

In order to detect the presence or absence of fractures in constructional members for steel buildings caused by external forces such as earthquakes without the removal of any fire resistive covering materials, we are developing a new nondestructive inspection (NDI) system. This system detects the presence or absence of fractures in a steel frame by measuring the impedance of a coil which exposes the test material to a magnetic field. The system is easy to handle and detection takes only a short time. In this system, the coil is connected to a compensating capacitor with a series-resonant circuit to reduce the impedance and multiply the impedance change by increasing the quality factor. First, the rates of change of impedance and phase angles were measured with the impedance meter of the proposed NDI system. Two types of test samples were investigated. One type of sample had a fracture in the steel plate. The others imitated the beam to column connection with or without a fracture. In both types of samples, the differences in the rates of change of impedance and phase caused by the presence or absence of fractures were measured. Second, in order to confirm the experimental result and establish the design method for optimizing the arrangement and shape of the coil, we calculated the fractional deviation of inductance between presence or absence of the fracture in the steel frame for two types of test samples through a 3-D magnetic field analysis taking eddy current into account. Since the analyzed the fractional deviations of inductance were in good agreement with those measured, the validity of our analysis was confirmed.

研削焼けの非破壊検出技術の開発 —第２報：渦電流センサの外乱抑制—

研削焼けの非破壊検出技術の開発 —第２報：渦電流センサの外乱抑制—

研削焼けの非破壊検出技術の開発 —第１報：渦電流センサによる研削焼け検出方法—

研削焼けの非破壊検出技術の開発 —第１報：渦電流センサによる研削焼け検出方法—

Safe product design – the role of the NDT reliability analysis

Abstract In line with the damage tolerance design principles, an adequate non-destructive inspection system is needed to ensure structural integrity. Yet, when pushed to the limits of their detection capability, non-destructive evaluation systems do not produce consistent hit/miss indications. Their capability of detecting flaws is therefore expressed as a probability of detection. In the conventional signal response reliability analysis, the probability of detection is expressed as a function of the flaw size. The adequacy of the inspection system is verified by comparing the size of the flaw that is reliably detected with the maximum allowable flaw size, which will not undermine the structural integrity. Analyses of modern structures show that other parameters also determine the severity of the flaw for the structure. Within the multi-parameter reliability analysis, the probability of detection can be expressed as a function of diverse influencing parameters. When determining the adequacy of the non-destructive evaluation system, the capability of detecting a flaw has to be expressed and checked against the critical value of exactly that parameter that determines flaw severity for the structure. Failing to do so can lead to a rejection of the healthy, or acceptance of the bad part. The principle is demonstrated on the transmit-receive longitudinal ultrasonic inspection data of the iron cast component with surface, semi-elliptical, crack-like flaws.

A preliminary study on noncontact imaging inspection for internal defects of plate-type nuclear fuel by using an active laser interferometer

A non-contact optical imaging technique was preliminarily studied to detect internal defects of a plate-type nuclear fuel specimen by using an active laser interferometer. A sinusoidal and periodic thermal wave induced periodic micro deformation including internal defect information of the specimen. The laser interferometer acquired a micro deformation image for the specimen surface, the shape of which varied according to the energy of the thermal wave. An adopted flexible holder of the specimen increased the capability of defect detection by concentrating the strains at the defects. A real-time inspection image including internal defect information was produced after the signal processing to remove noises. As a nondestructive inspection system, the developed visual inspection technique using an active laser interferometer can be a valuable tool to detect the internal defects of plate-type nuclear fuel.

A Novel Laser-EMAT System for Noncontact Testing Metal Materials

Detection and characterization of defects in metal parts in industrial and commercial settings has typically been carried out by nondestructive ultrasonic inspection systems. The aim of present work is to propose a kind of non-contact nondestructive testing system based on the laser and electro-magnetic acoustic transducer (EMAT) techniques, which is suitable to inspect the defects in metal material. The maximum lift-off value (LOV) of the system is 10 mm. Wavelet threshold method (WTM) is employed to improve the signal to noise ratio (SNR), and the values of SNR increase to 67.42 dB and 64.66 dB for the case of LOV=0 mm and LOV=10 mm, respectively.

Development of a Thermographic NDI System for Service Damage Identification in Inaccessible Areas

The periodic inspection and evaluation of components and systems is paramount to ensure they stay reliable throughout their service life. These tests which occur during the operation of the equipment serve as a means of performance assessment, failure analysis and prevention, monitoring, reliability analysis or could be applied to life cycle prediction. This paper documents the methodology and findings of an MSc group project involved in developing a portable non-destructive inspection system for inaccessible areas using pulsed thermography. In addition to being a fast and inexpensive inspection technique it also allows sub surface inspection in a wide range of materials. The resulting system is capable of identifying service damages in metals and composites and will lead to time and cost savings through in-service inspection. It proves the feasibility of adapting pulsed thermography for inspection of inaccessible areas by integrating a mirror based system. The use of this system has been demonstrated in the inspection of a train axle. Possible sources of error have been identified and recommendations for future improvements have been made.

Guided Wave Inspection and Monitoring of Railway Track

Cost-effective NDE of the vast length of aging railway track around the world remains a challenge for the community. Continuously welded rail is installed in tension but temperature changes can result in rail buckling if the initial tension is insufficient or fatigue cracks and ultimately rail breaks if the initial tension is excessive. The NDE challenge therefore includes both the detection of defects and the measurement of axial stress. Since continuously welded railway lines may be thought of as one-dimensional elastic waveguides, they are natural candidates for guided wave ultrasound, which offers the potential to interrogate a large length of rail from a single position. Guided waves have been proposed as a means of detecting the axial stress in rails to prevent buckling and also as a means of detecting complete breakage and cracks prior to breakage. This paper reviews the approaches used and the modeling methods available to support the development of nondestructive inspection and monitoring systems. Possibilities for future systems are also discussed.

中性子／γ線複合型核検知システム開発の現状II (1)全体システムの設計の現状

中性子／γ線複合型核検知システム開発の現状II (1)全体システムの設計の現状

Design and development of automatic visual inspection system for PCB manufacturing

Inspection of solder joints has been a critical process in the electronic manufacturing industry to reduce manufacturing cost, improve yield, and ensure product quality and reliability. This paper proposes two inspection modules for an automatic solder joint classification system. The ''front-end'' inspection system includes illumination normalisation, localisation and segmentation. The ''back-end'' inspection involves the classification of solder joints using the Log-Gabor filter and classifier fusion. Five different levels of solder quality with respect to the amount of solder paste have been defined. The Log-Gabor filter has been demonstrated to achieve high recognition rates and is resistant to misalignment. This proposed system does not need any special illumination system, and the images are acquired by an ordinary digital camera. This system could contribute to the development of automated non-contact, non-destructive and low cost solder joint quality inspection systems.

Nondestructive System for Inspecting Steel Bars and Cables in Concrete : Experimental Results Using a Concrete Test Sample

We have developed a new system for nondestructive inspection (NDI) which enables accurate detection and easy handling at low cost. It works by measuring the impedance due to the change in inductance in a solenoid coil. This paper describes the validity of the method we used to design this NDI system. The change in impedance and phase difference were measured with an impedance meter. The fractional deviation in inductance L and impedance Z changes due to the magnetization induced with and without a steel bar. The reduction in inductance L due to the eddy currents of power cables was measured. The measurement also proved that this NDI system can distinguish steel bars from power cables by using the polarity of the phase difference similar to what occurs in real concrete walls and slabs.

Non-Destructive Inspection using X-ray System

This paper introduces three types of X-ray non-destructive inspection systems developed by the use of micro-focus X-ray technique. The micro-CT (Computed Tomography) system reconstructs not only one slice image but also multi-images by only one scan of a inspected sample by acquiring X-ray projection data from many circumferential directions, and it creates three dimensional images from its multiple ones. It is used for the non-destructive testing of small objects such as IC devices. The micro-Focus X-ray Fluoroscopic Inspection System has an advantage of high magnification ratio, which is often used for the inspection of the BGA (Ball Grid Array). The Oblique-CT (Lamino-CT) system has a mechanism that rotates a sample obliquely to X-ray axis, which can make a sample put closer to the X-ray source, resulting in high magnification ratio. The combination of the micro-Focus X-ray and the Lamino-CT contributes development and inspection of PCBs (Printed Circuit Board).

Application of optical coherence tomography (OCT) to nondestructive inspection of dentures

The porosity of denture base resins continues to be one of the undesirable characteristics of acrylic resins. It is commonly accepted that porosity of the denture not only often leads to denture fractures, but also may function as a reservoir of potential pathogens. The purpose of this study was to present the first OCT images of finished dentures using a new advanced-type OCT scanner we have developed, and to discuss the application of our new OCT system for nondestructive inspection of dentures. Ten newly fabricated full dentures of outpatient of the National Center for Geriatrics and Gerontology in Japan were selected for this study. Two types of denture base resins were used for inspection by OCT, which provided clear images of all the dentures examined. Internal structures, not visually detectable, inspection, can be observed using this OCT system. It is concluded that OCT can detect nonvisible internal structures in dentures, a finding not reported to date. OCT may, therefore, be an appropriate method for detecting interior defects in dentures nondestructively.

THz imaging techniques for nondestructive inspections

Abstract We have suggested a wide range of real-life applications using novel terahertz imaging techniques. A high-resolution terahertz tomography has been demonstrated by ultra short terahertz pulses using optical fiber and a nonlinear organic crystal. We also describe a nondestructive inspection system that can monitor the soot distribution in a ceramic filter using millimeter-to-terahertz wave computed tomography. Further, we report on the thickness measurement of very thin films using high-sensitivity metal mesh filter. These techniques are directly applicable to the nondestructive testing in industries.

Non-destructive Characterization of Soot in Exhaust Filters Using Millimeter-wave Imaging

It is necessary to monitor the distribution of the soot that accumulates in the soot removal filter of an internal combustion engine to design the highly efficient filtering structure and optimize the timing of the filter renewal. However, there is no non-destructive inspection technique at present. In this study, we describe a non-destructive inspection system that can monitor the distribution of soot that accumulates in the filter using combination of millimeter-to-terahertz wave imaging and computed tomography. The transmittance of the filter shows a strong dependence on the angle of incidence because of its two-dimensional periodical shape. We identified a frequency at which photonic band gaps did not occur, and measured the three-dimensional tomographic image of the filter in a non-destructive manner.

Impedance Measurement Using a Resonance Circuit for Detecting Steel Bars and Cables Inside Pliable Plastic Conduit Tubes Buried in Concrete Walls and Slabs

In order to detect steel bars and power cables inside pliable plastic conduit tubes buried in concrete walls and slabs during the renovation of old buildings, we have developed a new nondestructive inspection (NDI) system. This system, which enables high precision detection and easy handling at low cost, works by measuring the impedance due to the inductance change of a solenoid coil which exposes the test material to a magnetic field. In this system, the solenoid coil is connected to a compensating capacitor with a series-resonant circuit to reduce the impedance and multiply the impedance change by increasing the quality factor, Q, i.e., the ratio of the inductive reactance, ?L, to the coil resistance, R, which contributes to improving the signal-to-noise ratio for detection. This paper describes the validity of the design method of this NDI system. Firstly, the fractional deviation of inductance, ?, the inductance changes between with and without a steel bar and power cables were analyzed. The deviations due to the eddy currents and magnetization induced in the steel bars and power cables were computed through 3-D magnetic field analysis taking eddy currents at 5, 40 and 800 kHz into account. Secondly, the rates of change of impedance (RCIs) and phase angles were measured with the impedance meter of the newly developed NDI system. This system was designed so that the value of became roughly 200 and the resonance frequencies became about 5, 40 and 800 kHz. For steel bars, the predicted RCIs, which were calculated from the computed s multiplied by the designed Q factor, roughly matched those measured. In case of power cables, the tendency of predicted RCIs were roughly in accord with those measured. The validity of the design method's detecting system was verified. In addition, the analysis and measurement proved that this NDI system can distinguish steel bars from power cables by the polarity of the phase angle.

Laser ultrasonic technique for evaluating solder bump defects in flip chip packages using modal and signal analysis methods

Current techniques for nondestructive quality evaluation of solder bumps in microelectronic packages have their own limitations and are unsuitable for in-line inspection because of high cost and low throughput. In order to meet requirements of quality inspection of electronic packages, a nondestructive and noncontact solder bump inspection system is being developed using laser ultrasound and interferometer techniques. This system uses a pulsed Nd:YAG laser to induce ultrasound in electronic packages in the thermoelastic regime; it then measures the transient out-of-plane displacement responses with an ultrasonic arrival on the surface of the packages using laser interferometer technique. This paper presents a systematic study of defect detection in flip chip solder bumps using a combined modal and signal analysis method. The correlation between the finite element (FE) modal analysis and wavelet analysis of laser ultrasound signals has been studied. With the help of FE modal analysis, the modes of flip chip packages sensitive to open bumps were predicted for further signal processing before conducting any experiments. The decomposed signal components sensitive to specific defects were extracted and analyzed with discrete wavelet transform. The results show that wavelet analysis increases the measurement sensitivity of the flip chip solder bump inspection compared with existing methods.

Pulsed Eddy-Current Based Giant Magnetoresistive System for the Inspection of Aircraft Structures

Research in nondestructive evaluation is constantly increasing the sensitivity of detection of small cracks embedded deep in layered aircraft structures. Pulsed eddy-current (PEC) techniques using coil probes have shown considerable promise in detection and characterization of buried cracks in multilayered structures. In this paper, we describe the design and development of a nondestructive inspection system that uses pulse excitation of a planar multiline coil to generate a transient field that is detected via a giant magnetoresistive (GMR) field sensor. An analysis algorithm using features in time and frequency domain processes the experimentally measured signals for automatic detection of small cracks under fasteners in multilayered structures at a depth of up to 10 mm.

?Nondestructive Inspection System Using Optical Profiles and Laser Surface Waves to Detect a Surface Crack

?Nondestructive Inspection System Using Optical Profiles and Laser Surface Waves to Detect a Surface Crack