Nondestructive Detection Technique Research Articles

超電導ＭＲＩを用いた西瓜空洞判定

The possibility of utilizing MRI for the non-destructive quality evaluation of watermelons is described. MRI is a unique, non-destructive and non-invasive detection technique. Today it has become an important medical diagnostic modality. Recently several attempts have been made to utilize MRI for agricultural or industrial application. We have tried to apply MRI method to the detection of internal voids in watermelons. Our experimental apparatus consisted of a 0.5T superconducting magnet with a bore 68cm in diameter, an actively shielded gradient coil with highpower amplifiers and a PC-based spectrometer. From a practical point of view, it is not practical for the inspection of watermelons to take cross sectional images with two-dimensions, because it takes quite a long time. In order to increase measurement rate, we adopted a 1-D MRI. We have carried out void detection on 30 watermelons by this method and obtained convincing results.

Reflectance assessment of mite effects on apple trees

Abstract Reflectance measurements were conducted in field plots of Golden Smoothee 2038 apple cultivar subjected to different levels of mite attack (from 0 to 500 cumulative mite days) over a 2-year period. Chlorophyll concentration decreased and carotenoid/chlorophyll a ratio increased with increasing level of attack. Classical reflectance indices such as red edge wavelength or the Normalized Difference Vegetation Index were unable to distinguish among treatments. On the other hand, spectral indices based on carotenoid/chlorophyll a (SRPI R430/R680) and chlorophyll degradation (Normalized Phaeophytinization Index calculated as (R415-R435)/(R435 +R415)) were correlated with the level of attack. These reflectance indices show potential uses of visible reflectance as non-invasive, non-destructive techniques for detection of mite effects.

LASER-GENERATED LAMB WAVES TO DETECT HIDDEN INTERFACIAL CORROSION IN THIN-SKIN AIRCRAFT COMPONENTS

Abstract One of the major challenges in extending the life of ageing aircraft is to develop improved nondestructive inspection techniques for the rapid large-area detection of various types of hidden corrosion in aircraft components. In this paper, a new one-sided ultrasonic technique is proposed to solve the generic problem of detecting hidden corrosion in thin metallic aircraft skins, where the corrosion has originated at the interface between the skin and a second layer in an aircraft component. The technique involves the use of laser-generated ultrasonic Lamb modes whose attenuation in a thin skin is increased by the presence of corrosion. This paper presents a successful demonstration of the technique on a thin-skin elevator component. The potential of the Lamb wave technique for rapid large-area scanning for hidden corrosion is also described.

Microwave sensitivity maximization of disbond characterization in conductor backed dielectric composites

A swept frequency microwave nondestructive technique for detection of disbond in a dielectric composite backed by a conducting plate is discussed. The theoretical development is based on an incident plane wave illuminating such a medium, and then formulating the characteristics of the reflected wave. This way the effective reflection coefficient of the medium is found. The phase of this reflection coefficient changes in the presence of a disbonded medium. With the determination of an optimally sensitive frequency range using the theoretical model and the known properties of the composite dielectric material, it is shown that disbonds on the order of a few microns can be accurately detected at relatively low microwave frequencies. Several experimental results are also presented.

Cause, control and detection of hollow heart in potatoes: A review

A review of the literature was conducted on the causes, development, control and detection of hollow heart in potatoes. Hollow heart is a physiological disorder characterized by a cavity in the pith region of the tuber. Development of the disorder is often associated with rapid tuber growth that may be preceded by a period of moisture or nutritional stress. Two or more types of hollow heart may exist. They are differentiated by the cause of the disorder, the pattern of development, and the growth stage of the tuber when the disorder develops. Management can affect the incidence of hollow heart by such methods as choice of cultivar, plant spacing, rate and timing of fertilizer application, and control of soil moisture. Several attempts have been made to develop non-destructive techniques for detection of tubers with hollow heart cavities. The most reliable and practical procedure developed to date for the detection of hollow heart in whole tubers uses x-ray technology.

Thermographic nondestructive evaluation of steel-polypropylene laminates

The efficacy of passive thermography as a nondestructive evaluation technique for detection of voids and interlaminar flaws in steel-polypropylene laminates was investigated. Both analytical and experimental studies were conducted to assess the flaw resolution characteristics of the technique and to determine the effects of pertinent geometric and thermal parameters on resolution. The implications of the analytical and experimental results from the parametric studies are discussed in terms of their effects on flaw resolution and test technique optimization for development of on-line NDE for quality control monitoring.

Nondestructive detection of fatigue damage

This paper will discuss the various nondestructive techniques which have been used or which are potentially useful for detection of fatigue damage. The ideal nondestructive testing technique would permit very early detection of fatigue damage so that proper assessment of the severity and rate of severity increase of the structural damage leading to failure can be made. Thus, the most sensitive systems would be capable of detecting motion, pileup, and breakaway of dislocations; the next most sensitive systems would be capable of detecting microcracks; the least sensitive systems would only be capable of detecting macrocracks. It is practically expedient to have nondestructive techniques which can successfully detect fatigue damage in each of these regimes since some components can tolerate larger amounts of fatigue damage or larger crack sizes than others without serious concern for the structural integrity of the component. It will be shown that the best nondestructive technique for detecting and sizing of macrocracks is ultrasonics; the best nondestructive techniques for detection of microcrack formation and possible pre‐microcrack fatigue damage are ultrasonic attenuation and acoustic emission; a large number of nondestructive techniques for residual stress (strain) measurements are candidates for extremely early fatigue damage detection, with current interest primarily directed at ultrasonic wave velocity measurements.

Storing ions for collision studies

A static trap capable of storing ions for many hours—electrons for over a month—bids fair to bring the convenience of the chemist's reagent shelf to the study of ions and their interactions. The trap to store heavy ions developed at the Joint Institute of Laboratory Astrophysics, shown on the cover and in figure 1, is preferable for our work to its older cousin, the radiofrequency trap, in that it does not feed energy into the system it contains. Its usefulness is further enhanced by a nondestructive detection technique. Thus ends the era when our knowledge of ions and their interactions depended exclusively on analysis of plasmas, laboratory and natural, or the cleaner method of colliding beams.

Crack evaluation and growth during low cycle plastic fatigue—non-destructive techniques for detection

A study of the simulated reflection of a wideband ultrasound shear wave from the solid/viscous fluid interface is presented. Various parameters affecting reflection factors including the material properties of the solid, fluid properties like density and viscosity, and the operating frequency are discussed. Simulated ultrasonic response waveforms are compared with the experimentally obtained data for NIST traceable calibration standards of viscosity. A good agreement was observed between the simulated and experimental waveforms at various viscosities and for different solid substrates.