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Impact damage in thin carbon fiber reinforced polymer composites often results in a relatively small region of damage at the front surface, with increasing damage near the back surface. Conventional methods for reducing the pulsed thermographic responses of the composite tend to underestimate the size of the back surface damage, since the smaller near surface damage gives the largest thermographic indication. A method is presented for reducing the thermographic data to produce an estimated size for the impact damage that is much closer to the size of the damage estimated from other NDE techniques such as microfocus x-ray computed tomography and pulse echo ultrasonics. Examples of the application of the technique to experimental data acquired on specimens with impact damage are presented. The method is also applied to the results of thermographic simulations to investigate the limitations of the technique.

The paper presents a method for investigating the stress-induced changes in ultrasonic wave speeds at room temperature in rail steel. The pulse echo method is used to measure the wave speed accurately. All of the second-order and thirdorder elastic constants are calculated from the measured acoustoelastic data. A comparison of the strain-induced elastic constant at room temperature is also conducted with previous measurement results.

A passive wireless displacement sensor suitable for use in civil structural health monitoring applications is presented. The sensor is based on a resonant electromagnetic cavity with one end of the cavity formed by a flexible membrane. A rod attached to the membrane causes the dimensions of the cavity to change when the rod is displaced. The change in dimensions causes a shift the resonant frequency of the cavity that is directly related to the displacement of the rod. In the example shown the shift is 7 MHz per mm for a cavity with a resonant frequency of 2450 MHz. Using a pulse echo interrogation technique resonant shifts of 100 kHz are resolvable. In the laboratory, displacements of 0.014 mm were measurable, with the distance between the interrogator and the sensor of up to 4.5 m.

The time-dependent Mueller matrix solution of vector radiative transfer for inhomogeneous random media of non-spherical scatterers is presented. Co-polarized and cross-polarized bistatic scattering for a polarized pulse incidence are numerically simulated. Numerical results well demonstrate volumetric and surface scattering mechanism and depict the inhomogeneous fraction profile of random scatterers. Effective canopy height inverted from the pulse echo is discussed. Numerical simulation shows detection of anomalous scatters under inhomogeneous canopy.

Frequency dependent attenuation is a pronounced feature of ultrasound propagation in human tissues. A new technique for calculating that parameter from backscattered echoes is demonstrated, and it is shown how the information may be incorporated into a grey scale image. Analysis of the noisy nature of attenuation estimates from conventional backscattered echo signals suggests a new technique for producing less erratic estimates, by manipulating zeroes in the complex frequency domain. No signal averaging is needed, and the method lends itself to analysis of short data segments, thereby providing suitable input for attenuation imaging. Rf data is required. The new method is found to considerably reduce the variance of the attenuation estimates from short data segments. It is found that attenuation-weighted B-mode images are an informative way to show results. The method of zero manipulation, presented here, for producing less noisy pulse-echo attenuation estimates represents a powerful approach towards the problem.

Eliminate any doubt that the vessel condition is suitable for continued operation through a planned inspection program that can mitigate or avoid failure of a pressure vessel due to corrosion or erosion. Proper inspection and documentation help you in identifying the problem and confirming the actual thickness leading to properly correcting deficiencies. Proper inspection is the antidote for any inspection program. Vessel life can be extended, risk can be minimized and unscheduled downtime can be prevented by implementing and managing your inspection program. A successful program includes maintaining accurate records, conducting inspections in regular intervals, and taking proper action on deficiencies. Therefore, you will know what you have and the condition of your equipment. Pressure vessel inspections can be classified into two general categories: surface inspection and volumetric inspection. Surface techniques for vessels include two of the commonest types: dye-penetrant and magnetic particle testing. Board qualified inspectors are required to perform these two tests. Volumetric techniques for vessels include three common types: ultrasonic testing, eddy current testing, and radiography. At Abbott the use of advanced NDE (non destructive examination) techniques, ultrasonic b-scan, has provided us with the proper tools to obtain the above objectives. We have been applying ultrasonic b-scan utilizing a pulse echo pitch catch technique to provide us with essential data on each of our pressure vessels. This reduces equipment downtime because the nondestructive examination usually takes place while our vessels are in service. As inspections take place we are able to view a real time image of the defective discontinuities on a video monitor. This ultrasonic b-scan technique is allowing us to perform fast accurate examinations covering up to 96% of the surface area of each pressure vessel.

Many standard non destructive testing systems utilize ultrasonic pulse echo techniques to localize defects within structures. These techniques rely upon the scattering of acoustic energy by the defect and two or more acoustic detectors for localization. In this paper, an alternate method of structural damage detection and location is proposed. The technique involves the use of a leaky acoustic waveguide and a unidirectional acoustic waveguide attached to the structure of interest. Only one acoustic detector is required for defect location. An analysis of the concept is provided and experimental results are presented.

This paper reviews the results of research in imaging reported in the last two years approximately. The emphasis is placed on the high frequency applications of this subject and very little reference is made to sonar and none to geological applications. The subject is discussed under three main divisions, direct (pulse echo) imaging, holography and finally particular devices. Emphasis has been placed on the physical principles used. It is assumed the reader is conversant with the outlines of earlier work in the field.

The Standards Committee of the American Institute of Ultrasound in Medicine uum and the National Bureau of Standards (NBS) cosponsored a meeting on Pulse-Echo Ultrasonic Transducer Characterization at the NBS in Gaithersberg,Maryland, June 16, 1977. More than 100 people from both the medical ultrasound and non-destructive testing communities attended. Initiation of work on a standard for these transducers was the purpose of the meeting. A morning session of invited and contributed papers was followed by the organizational meeting of the ALUM Subcommittee on Pulse-Echo Transducer Characterization. The purpose of this paper is to discuss standardization problems of the transducer, a vitally important and often neglected portion of a diagnostic ultrasound system. A brief summary of the ideas discussed that day and the direction chosen by the committee is included.

Investigations were conducted regarding the use of the ultrasonic pulse echo and the infrared thermography nondestructive evaluation (NDE) methods for detecting voids and delaminations in adhesive-bonded seams of single-ply roofing membranes. Previous studies had indicated that these defects could be detected using the two NDE methods. In the present study, voids incorporated in 1.2 m (48 in.) long seam test specimens were located by the pulse-echo method using a wheel transducer to scan along the length of the seam. These results indicated that the ultrasonic pulse echo method using a wheel transducer can be useful as a field technique for assisting in the quality assessment of seams. When using the infrared thermography method to evaluate the seam specimens, it was found that, unlike previous studies, only sections of some voids were detected and that other voids were not detected at all. It was suggested that collapse of the voids due to the applied pressure during seam formation might have provided insufficient surface temperature differential between the bonded areas of the seam and the void areas of the seams during transient heat flow. The results raised concerns that the infrared thermography method may not be practical for the general detection of voids of seams in service.

The technique of ultrasonic pulse-echo visualisation for medical diagnosis is well known and has received widespread acceptance in clinical practice in many diagnostic areas. The main areas of application at present are the abdominal organs (Ref.l,2), pregnant uterus (Ref.3) and heart (Ref.4). Clinical evaluation studies are being carried out in the eye (Ref.5,6), thyroid (Ref.7), brain (Ref.8) and breast (Ref.9). As the instrumentation and resultant echogram quality have been improved, the range of regions and conditions in which the technique has found application have been greatly increased. It is the aim of this paper to review the assumptions and physical laws upon which the technique is based and to examine the relationship between the limitations set by these considerations and the performance obtained with present equipment.© (1975) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.