Prospects of the application of nondestructive testing to the diagnostics of nano- and microstructural materials

This paper covers some aspects of the application of nondestructive testing methods to the diagnostics of nano- and microstructural materials. The questions of improving the resolution of the experimental techniques for the visualization and analysis of nano- and microstructural objects are discussed. The potentials of acoustic methods used to gain information on nano- and microheterogeneities in inspected objects are demonstrated.     

Increasing the reliability of the detection of flaws in complex structures by integrating the information of multiparametric nondestructive testing

The basic principles and methods for integrating information from multiparametric nondestructive testing for the purpose of detecting anomalies, flaws, and damage in different objects and structures are considered. Some experimental data and the results of the development of algorithms for the integration of nondestructive testing techniques that are aimed at solving formulated problems on the basis of telescoping-effect estimation methods and the construction of the multidimensional analogues of inverse probability methods are cited.     

An efficient approach to approximation and practical application of DGS diagrams

A nonstandard experimental and mathematical approach to the development of analytical and numerical multidimensional approximations for DGS diagrams is proposed. This method features sufficiently high accuracy, versatility, and reliability for different types of piezoelectric probes (PPs) and test objects (TOs). The efficiency of the approach is demonstrated by a test example and is also checked in its implementation in software for the UD4-S device based on standard specimens simulating flaws. Issues related to the solution of the direct and inverse problems of ultrasonic nondestructive testing are discussed.Translated from Defektoskopiya, Vol. 40, No. 10, 2004, pp. 49–61.Original Russian Text Copyright © 2004 by Sviridov, Gaburov, Veremeenko, Pokladov.     

On the principles of optimizing the technologies of acoustic-emission strength control of industrial objects

Expansion of the application domain and heightened requirements for the accuracy of acoustic-emission (AE) testing have necessitated the optimization of AE-based nondestructive strength-testing techniques. Current trends in the development of these techniques are provided and general principles for improving their efficiency are stated. Examples of the implementations of AE testing on various objects are illustrated.     

How to Test Better

Practical examples for optimization of nondestructive testing of various objects are presented.     

Application of the acoustoelasticity phenomenon in studying stress states in technological pipelines

The capabilities of the nondestructive ultrasonic method for evaluating stresses are demonstrated by an example of measuring non-design axial stresses in technological pipelines. The results of applying the acoustoelasticity effect, which was implemented in an IN-5101A device, obtained in direct in situ measurements of mechanical stresses in piping structures of the main equipment of compressor stations are presented. The features of applying the acoustoelasticity method for measuring stresses in these objects and its prospects for solving the problem of periodic testing of a stressed state of pipeline systems are considered.     

What to teach in measurement and instrumentation

The paper presents its authors' views on the scope of education and training in measurement and instrumentation. It concerns mainly the basic level of teaching engineers. Great advances in instrumentation and the proliferation of measurement needs made impossible the creation of new training schemes by the simple addition of new topics to the traditional ones. There is necessarily a completely new training scheme aimed at the general principles of measurement techniques and the measurement art which, when mastered by a student, should enable him to solve measurement tasks connected with investigation of some given objects.     

Determining Geometric-Acoustic Properties of a Weld as a Solution to the Inverse Coefficient Problem for a Scalar Wave Equation

Russian Journal of Nondestructive Testing - Ultrasonic tomographic methods of nondestructive testing of objects have been developed in order to determine the geometry of a weld and to estimate the...     

Nondestructive Permittivity Profile Retrieval of Non-Planar Objects by Free Space Microwave Techniques

In this paper, a nondestructive method for the non-contact characterization of non-planar dielectric objects is presented. Traditionally, this kind of measurement is achieved by using spot-focused antennas associated to a vector network analyzer. In this study, we propose a free space measurement system, fitted out with a classical horn antenna, which demonstrates its usefulness in many practical cases. The permittivity has been computed from the measurement of the reflection coefficient of metal-backed samples of different shapes at 2.45 GHz. Signal processing tools, based on deconvolution techniques, are developed to enhance the accuracy of the permittivity measurement.     

Thermal nondestructive testing of materials and products: a review

The history of thermal nondestructive testing and infrared thermography is briefly reviewed. The state-of-the art of thermal testing with a focus on its applications to testing of composite materials in aerospace industry is described.     

Improved immunity to lift-off effect in pulsed eddy current testing with two-stage differential probes

Pulse eddy current (PEC) testing is broadly used as an effective nondestructive testing technique especially for the defect detection of multiple layer and irregular surface objects. PEC testing’s adoption of repeated pulses as excitation provides for the penetration of many frequency components into the piece being tested and returns more information from various depths. As the lift-off height will inevitably change during detection, the lift-off effect serves as a significant obstacle to implement effective nondestructive testing and further evaluations. This paper concentrates on improving the probe’s immunity to the lift-off effect and proposes two-stage PEC differential probes. Physical experiments are addressed in this paper. Experimental results demonstrate that two-stage differential PEC probes are able to suppress lift-off effects. The text was submitted by the authors in English.     

A remote scanning Raman spectrometer for in situ measurements of works of art

In conservation science, one of the main concerns is to extract information from an artistic surface without damaging it. Raman spectroscopy has emerged in recent years as a reliable tool for the non-destructive analysis of a wide range of inorganic and organic materials in works of art and archaeological objects. Nevertheless, the technique is still mainly limited to the analysis of micro-samples taken from artistic surfaces. The development of an instrument able to perform non-contact analysis of an area of a few square centimeters aims to further increase the employment of this technique. This paper describes the development of a prototype Raman scanning spectrometer based on a diode laser, a 2D scanning mirror stage and a custom optical system, which can map a surface of 6 cm in diameter at a working distance of 20 cm. The device exhibits collecting optics with a depth of field close to 6 cm, which makes the Raman system suitable for the analysis of non-flat surfaces and three-dimensional objects. In addition, the overall dimensions and weight of the instrument have been limited in order to make the device transportable and, in principle, usable for in situ measurements. Details on the design of the device, with particular emphasis on the collecting optical system, and on results of the characterization tests carried out to assess its performances are reported. Finally, an example of an application involving the identification of pigments from a model painting is presented.     

A spatiotemporal picture of the acoustic field of elastic-wave diffraction at the edge of a crack

With a Doppler ultrasonic laser interferometer, we have visualized the features of the spatiotemporal structure of the acoustic field near a crack with a small width of opening and a spatial location not allowing its detection by traditional techniques of acoustic nondestructive testing. The obtained result can be used in development of new techniques to detect cracks and microcracks of different kinds by nondestructive testing of products and units.     

Applying Laser-Ultrasonic and Acoustic-Emission Methods to Nondestructive Testing at Different Stages of Deformation Formation in Friction Stir Welding

Russian Journal of Nondestructive Testing - The results of applying laser-ultrasonic and acoustic-emission nondestructive testing techniques to study the processes of deformation and fracture of...     

Identification of materials in X-Ray inspections of objects by the dual-energy method

The state-of-the-art, application experience, and trends in further perfection of the dualenergy method as used in digital-radiography and X-ray computed-tomography systems intended for nondestructive testing and screening of objects are reviewed.     

An H∞ deconvolution filter and its application to ultrasonic nondestructive evaluation of materials

Deconvolution can be a valuable technique for interpreting results of ultrasonic nondestructive evaluation (NDE) tests of materials. This is especially true for state of the art hybrid materials. In this paper, a new H_∞ deconvolution filter is presented. The filter is applied to typical ultrasonic NDE data, including through-transmission data for aluminum and composite samples. The results are compared to those obtained from a Wiener deconvolution filter. The performance of the H_∞ filter is as good or better than the performance of the Wiener filter.     

Some Possibilities of Enhancing the Efficiency of Penetrant Inspection

Some possibilities of enhancing the efficiency of penetrant inspection under autumn-winter conditions are studied and confirmed experimentally. The role of the viscosity of a penetrant in the choice of materials for the nondestructive inspection of the corresponding objects is established.     

Automated inspection of PCB components using a genetic algorithm template-matching approach

Automated inspection of surface mount PCB boards is a requirement to assure quality and to reduce manufacturing scrap costs and rework. This paper investigates methodologies for locating and identifying multiple objects in images used for surface mount device inspection. One of the main challenges for surface mount device inspection is component placement inspection. Component placement errors such as missing, misaligned or incorrectly rotated components are a major cause of defects and need to be detected before and after the solder reflow process. This paper focuses on automated object-recognition techniques for locating multiple objects using grey-model fitting for producing a generalised template for a set of components. The work uses the normalised cross correlation (NCC) template-matching approach and examines a method for constraining the search space to reduce computational calculations. The search for template positions has been performed exhaustively and by using a genetic algorithm. Experimental results using a typical PCB image are reported.     

Method of Finite Differences in Time Domain. Calculating Echo Signals in Anisotropic Inhomogeneous Materials,Pattern Noise

When developing ultrasonic testing techniques for such complex objects as composite welds, the method of finite differences in time domain (FDTD) can be used to calculate echo signals in numerical experiments. Since the FDTD method is based on explicit numerical solution of the wave equation for an elastic medium, it can be used to take account of such effects as the emergence of a run round wave on a volume reflector, the transformation of a longitudinal wave into a lateral one under scattering of ultrasound by a crack, and the rescattering of pulses between reflectors and test-object boundaries. Applying the FDTD method to modeling the propagation of ultrasound in the sample with a high pattern noise and in the samples made of anisotropic inhomogeneous materials is substantiated. The FDTD calculation of the direct problem of propagation of elastic vibrations in a solid may prove useful when solving the inverse problem of ultrasonic nondestructive testing.     

State-of-the art and development prospects of digital radiography systems for nondestructive testing,evaluation, and inspection of objects: a review

A review of modern state and practical applications of various digital radiography systems that are intended for nondestructive testing, evaluation, and inspection of objects is presented. The mainstream trends of development are described.