In Tribute and Memory of Dr. Aleksander Pilarski

A dear friend and colleague to many of us in the Nondestructive Testing Community, Dr. Aleksander Pilarski, passed away on January 6, 1994. “Olek” as he was known to us, has made many contributions to QNDE in the past decade. A brief review and highlights of his life and professional career are outlined in this brief tribute

Computer Simulation of Ultrasonic Scattering and Texture in B-Mode Images

Diagnostic ultrasound has been widely used in clinical applications, such as soft tissue abnormality detection and blood flow detection. However, due to the complexity of ultrasonic wave propagation and scattering in biological tissues which generally involves wave reflection, refraction, scattering, absorption and other wave phenomena, it has always been a rather difficult task to interpret the wave mechanics through the received scattering signals

A Scoping Study of United States Extension Professional Competencies

This scoping study aimed to answer the question: What is known from existing research studies about the major competencies required of Extension professionals? Scoping studies are characterized by searching the literature to summarize major concepts on a research topic, and they are valuable as they show evidence for the major concepts. This study was limited to research studies of United States’ Extension professionals. The major conclusion from the scoping study is that existing research studies have yielded a rich literature base regarding Extension professional competencies. This scoping study identified 15 Extension professional competency domains: communication, diversity and cultural competence, flexibility, interpersonal relations, knowledge of Extension, leadership, professionalism, program planning and evaluation, resource management, subject matter competence, teaching methodology and delivery, technology, thinking and problem-solving, understanding community needs, and volunteer management. It is recommended that the results inform Extension professional job descriptions and professional learning programs

Acousto-Ultrasonic Source Influence in an Anisotropic Layer

The current work addresses ultrasonic wave interaction within an orthotropic layer with two disk transducers in an acousto-ultrasonic mode. Earlier works have focused on studies of the influence of a rectangular transducer [1,2]. Acousto-ultrasonic techniques are useful in many cases where there is access to one side only. The different wave modes set-up in the layer are sensitive to many parameters such as source size, frequency, direction, etc. Computation of the wave structure within this layer of finite thickness is necessary to acquire quantitative information about material characterization and discontinuities. An attempt is made here to characterize the number and velocity of propagation modes with respect to direction and frequency. A special case of a composite is considered with particular values for azimuthal angle and frequency. Amplitude and velocity values for piston and parabolic source distributions have been calculated

A New Approach for the Analysis of Impact-Echo Data

The recently developed impact-echo (IE) method, which utilizes an impact and subsequent displacement monitoring of the concrete surface, appears promising for the inspection of concrete structures. IE has been shown to be particularly suitable for void, delamination, and cracking detection in hardened concrete structures including bridge decks since deep penetration into the structure and one-sided accessibility are obtained. For this method to be reliable, however, accurate measurements of peak frequencies in the magnitude spectrum of the frequency domain must be made. In addition, the interpretation of confusing spectrums may be required. The first part of this paper reviews the existing impact echo technique, including typical signal generation and capture possibilities as well as the accepted signal processing. Next, an alternative approach to signal processing is developed; this approach is based on a brief literature review and laboratory experiments. It is proposed that this approach, based on the spacing of peaks in the magnitude spectrum may reduce the uncertainty of impact echo signal analysis

Generation of guided waves in hollow cylinders by wedge and comb type transducers

It was shown by Denos C. Gazis in 19591 that in linearly elastic hollow circular cylinders there exists an infinite number of “normal modes”, each of which has its own propagation characteristics such as phase and group velocity as well as their own displacement and stress distributions throughout the cross section of the cylinder. It was also shown that, even for a given mode, these characteristics changed with changing frequency. In general, when such a cylinder is loaded by external forces, all of the modes of the structure will be excited in varying strengths determined by the characteristics of the applied loading. From a nondestructive evaluation (NDE) point of view, however, there are some modes which, due to their unique characteristics, are more sensitive to the quantities being measured or the defects being sought. It would be advantageous, therefore, to modify the applied loading so as to excite with appreciable amplitude only those modes which are found to be sensitive to the quantity being measured. In order to do this however, the relationship between the applied loading and the amplitudes of the generated modes must be understood. In this paper, the general problem of determining the amplitudes with which each propagating mode is generated due to the application of specific types of separable, time harmonic loading is investigated. (The more general problem of non-separable loading can be found in a recent paper2). The general results for separable loading are then specialized to two types of transducers commonly used in NDE to determine how the parameters of these two types of sources affect the amplitudes of the generated modes

The Influence of Finite-size Sources in Acousto-ultrasonics

This work explores the effects that the finite normal axisymmetric traction loading of an infinite isotropic plate has on wave propagation in acousto-ultrasonics (AU), in which guided waves are created using two normal incidence transducers. Although the work also addresses the effects of the transducer pressure distribution and pulse shape, this thesis concentrates on two main questions: how does the transducer's diameter control the phase velocity and frequency spectrum of the response, and how does the plate thickness relate to the plate's excitability? The mathematics of the time-harmonic solution and the physical principles and the practical considerations for AU wave generation are explained. Transient sources are modeled by the linear superposition of the time-harmonic solutions found using the Hankel transform and they are then compared to experimental data to provide insight into the relation between the size of the transducer and the preferred phase velocity

Ultrasonics Guided Waves for Piping Inspection

An ultrasonic guided wave system for pipe inspection is proposed. Using guided wave experience to date on a variety of different tubing problems, feasibility experiments have already been conducted on piping under insulation in both a laboratory and chemical processing facility field environment. Several guided wave techniques are introduced, one using a broad banded variable angle beam transducer on a curved shoe, and one on a newly developed pipe comb system. Discussion on both axisymmetric and non-axisymmetric wave propagation is presented

Finite Size and Speciment Thickness Influence in Acousto-Ultrasonic NDE

Acousto-ultrasonics (AU) uses a pair of transducers to characterize distributed damage in composite plates. A transducer placed normal to the surface creates resonances which propagate as plate waves. Once the receiving transducer picks up the signal, simple analysis techniques, such as the zeroth or first moment of the power spectrum, are applied to create a Stress Wave Factor (SWF). The SWF is then used to quantify the damage state of the composite once the system has been properly trained