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Showing papers in "Ndt International in 1978"



Journal ArticleDOI
TL;DR: In this article, a mathematical method is developed which allows the location of sources on a spherical surface by using a system of coordinates which is easily applied to an industrial vessel, where the radius of the sphere is inceased to infinity.
Abstract: Using the differences in time of arrival from an acoustic emission source to several sensors, the position of the source may be calculated. A mathematical method is developed which allows the location of sources on a spherical surface by using a system of coordinates which is easily applied to an industrial vessel. If the radius of the sphere is inceased to infinity, the formulae can be used for the location of sources on a plane surface. A brief discussion of the results is given, keeping in mind the industrial aspect of the technique.

26 citations


Journal ArticleDOI
TL;DR: In this paper, the magnetic saturation method is proposed as the arbitrary, standard method of calibrating non-destructive ferrite content measuring devices, and the results of work carried out in the USSR on the chemical composition and saturation magnetization of δ-ferrite, on the FC-2 ferrite contents measuring device, and on the correlation of the USSR δ -ferrite percent and the USA ferrite number are reported.
Abstract: The need for a well-founded and fundamental method of determining the δ-ferrite content in austenitic stainless steel weld metal is discussed in the context of solving the problem of determining an internationally agreed procedure for non-destructive ferritometers; the work of the International Institute of Welding on this topic is discussed. The results of work carried out in the USSR on the chemical composition and saturation magnetization of δ-ferrite, on the FC-2 ferrite content measuring device, and on the correlation of the USSR δ-ferrite percent and the USA ferrite number are reported. The magnetic saturation method is proposed as the arbitrary, standard method of calibrating non-destructive ferrite content measuring devices.

24 citations


Journal ArticleDOI
TL;DR: In this article, three successful applications of thermography to different industries are described, and the authors describe three successful application cases of the technique in different industries and describe the application of the method to different process plants.
Abstract: Thermography techniques are used to monitor both the temperature and the temperature pattern of equipment in operation. This information, together with data on the physical construction of the component and the thermodynamic state of the equipment is used to evaluate the degree of deterioration of an item of process plant. Three successful applications of thermography to different industries are described.

14 citations


Journal ArticleDOI
TL;DR: The relatively new SHRIMP® method of ndt is discussed in this article, where a sinusoidal force is applied to a point on the structure and responses at other points are measured; if a part is faulty, the response of that part will be anomolous compared to the norm.
Abstract: The relatively new SHRIMP® method of ndt is discussed; the method is shown to be capable, when coupled with appropriate analyses, of assessing the structural integrity of a composite structure, before and after repair. In the SHRIMP® method, a sinusoidal force is applied to a point on the structure and responses at other points are measured; if a part is faulty, the response of that part will be anomolous compared to the norm, as will its influence on neighbouring parts. A test programme is described in which reinforced concrete beams were tested using SHRIMP®, cracked, repaired using injection of an epoxide resin, and then retested.

11 citations


Journal ArticleDOI
TL;DR: In this article, the path taken by transverse ultrasonic waves through an austenitic stainless steel specimen embodying a butt-weld was traced by repeatedly shaving the surface of the specimen and scanning at each stage the newly uncovered surface with a dynamic sensor to obtain a C-scan of the through-transmission pattern of the beam penetrating through the surface.
Abstract: A study has been made into the causes of the false indications sometimes observed upon ultrasonic inspection of austenitic stainless steel welds. The path taken by transverse ultrasonic waves through an austenitic stainless steel specimen embodying a butt-weld was traced by repeatedly shaving the surface of the specimen and scanning at each stage the newly uncovered surface with a dynamic sensor to obtain a C-scan of the through-transmission pattern of the beam penetrating through the surface. This showed that the false indications are back reflections, from the metal surface, of waves that have propagated along dendritic crystal formations developed in the weld metal. The present work provides evidence that certain indications obtained on austenitic stainless steel welds are in fact spurious, and should not be ascribed to defects in the weld.

11 citations


Journal ArticleDOI
TL;DR: In this article, an instrument for detecting blockages and holes in tubes is described, which is based on a pulse echo technique using sound waves propagating through the air inside the tube, where the combined transmitter and receiver are connected to an open end of the tube and any foreign material, discontinuity (such as a change in tube diameter or a bad weld) or hole, produces an echo which is displayed showing its position.
Abstract: An instrument for detecting blockages and holes in tubes is described. The operation is based on a pulse echo technique using sound waves propagating through the air inside the tube. The combined transmitter and receiver is connected to an open end of the tube and any foreign material, discontinuity (such as a change in tube diameter or a bad weld) or hole, produces an echo which is displayed showing its position. At present the sensitivity is such that, for example, 4 mm diameter objects and 1 2 mm diameter holes can be located up to a distance of 30 metres in 25 mm diameter tubes, while larger objects can be found up to 100 metres. The equipment is simple and easy to use and in general is unaffected by bends. Where tubes are readily accessible, as at tube plates, surveys at a rate of 800 tubes or more an hour are possible.

10 citations


Journal ArticleDOI
TL;DR: In this paper, the principles of stress measurement and analysis using X-ray methods are given, followed by a description of the two main techniques currently available, which are based on either a camera, which is readily portable and requires short testing times, or a diffractometer which although bulky and of higher initial cost, is more accurate.
Abstract: The principles of stress measurement and analysis using X-ray methods is given, followed by a description of the two main techniques currently available. These are based on either a camera, which is readily portable and requires short testing times, or a diffractometer which although bulky and of higher initial cost, is more accurate.

8 citations


Journal ArticleDOI
TL;DR: A review of the philosophy of wear debris-based condition monitoring and the methods available can be found in this paper, where a recently developed technique, ferrography, which separates wear debris and contaminant particles from a lubricant and arranges them according to size on a transparent substrate for examination.
Abstract: Separation and study of wear particles can provide a powerful basis for condition monitoring of machinery. This article briefly reviews the philosophy of wear debris-based condition monitoring and the methods available. Greater emphasis is given to a recently developed technique, ferrography, which separates wear debris and contaminant particles from a lubricant and arranges them according to size on a transparent substrate for examination.

7 citations


Journal ArticleDOI
TL;DR: In this article, a simple low-cost method is described for the measurement of absolute signal to noise ratio in response to white noise excitation energy as produced by a jet of helium gas.
Abstract: Inability to determine the absolute sensitivity of acoustic emission transducing systems has long presented a problem for workers in this field. A simple, low cost method is described for the measurement of absolute signal to noise ratio in response to white noise excitation energy as produced by a jet of helium gas. This method facilitates the direct comparison of system sensitivity, in the range 0–1.0 MHz, regardless of the type of signal conditioning used.

5 citations


Journal ArticleDOI
TL;DR: The use of the C-scan technique is described for qualitative measurement of void content, for determining deviation in thickness and fibre content, and for detecting fibre misorientations, delaminations and bond failures as mentioned in this paper.
Abstract: The use of the C-scan technique is described for qualitative measurement of void content, for determining deviation in thickness and fibre content, and for detecting fibre misorientations, delaminations and bond failures. The interpretation of C-scan grey tone pattern is described and it is found that these can be misleading in certain circumstances.

Journal ArticleDOI
TL;DR: In this paper, the authors introduce acoustic emission and outline the various ways in which it is used to interrogate materials, including material selection, process monitoring and control, component testing and quality control, and structural testing.
Abstract: This paper introduces acoustic emission and outlines the various ways in which it is used to interrogate materials. The approach to using acoustic emission techniques in a range of industrial situations is described in conjunction with examples from material selection; process monitoring and control; component testing and quality control; and structural testing. The relation of acoustic emission to other ndt techniques is briefly discussed together with the future development of the instrumentation.

Journal ArticleDOI
TL;DR: The value of corrosion monitoring both to monitor and to control plant operation is discussed in this article, where a review of the corrosion monitoring techniques available is given together with descriptions of their main applications.
Abstract: The value of corrosion monitoring both to monitor and to control plant operation is discussed. A review of the corrosion monitoring techniques available is given together with descriptions of their main applications.

Journal ArticleDOI
TL;DR: In this paper, the authors used three ultrasonic techniques: an end-wise scan, a near end-low angle scan and a high angle shear wave scan to test the whole axle.
Abstract: Axles of traction and rolling stock in use by British Rail are subjected to in-service ndt using three mandatory ultrasonic techniques; these are an end-wise scan, a near end-low angle scan and a high angle shear wave scan. The use of these three scans ensures that the whole axle is tested, not just the traditional cracking zones.

Journal ArticleDOI
TL;DR: In this article, a simple correlation has been discovered between an empirical expression for the ductility of a sample containing a single void and the backscattered ultrasonic power derived from scattering theory.
Abstract: Results are presented on the scattering of ultrasonic waves from defects embedded in metals and on the influence of these defects on the mechanical properties. A simple correlation has been discovered between an empirical expression for the ductility of a sample containing a single void and the back-scattered ultrasonic power derived from scattering theory. An expression is derived which relates the ductility (reduction in cross-sectional area at tensile fracture) with the high-frequency (15 MHz) back-scattered ultrasonic signal in an approximately linear fashion. The data obtained on diffusion bonded Ti-alloy samples are in good agreement with the predictions. These results open the door to the prediction of ductility from ultrasonic measurements.

Journal ArticleDOI
F.H. Chang1, J.R. Bell1
TL;DR: In this article, the authors present the results of a study of the propagation of ultrasonic waves incident normally on a five-region model consisting of water/ aluminium/adhesive/aluminium/water layers.
Abstract: This paper presents the results of a study of the propagation of ultrasonic waves incident normally on a five-region model consisting of water/ aluminium/adhesive/aluminium/water layers. The ultrasonic signal power reflected from various interfaces in the multi-layered structure was calculated using the energy partition principle; the ultrasonic attenuation in the various media was taken into account in the study. The phase relationship between the incident and reflected portions of each ultrasonic pulse was followed in detailed calculation. Results of the analysis show excellent correlation with experimental results obtained by pulsing ultrasound at a three-layered structure immersed in water.

Journal ArticleDOI
TL;DR: In this article, a portable backscatter Mossbauer spectroscopy has been used for the quantitative measurement of the ratio of ferrite to austenite in stainless steels in a rapid, non-destructive, inexpensive and reproducible manner.
Abstract: Modified back-scatter Mossbauer spectroscopy has been used for the quantitative measurement of the ratio of ferrite to austenite in stainless steels in a rapid, non-destructive, inexpensive and reproducible manner. By using only zero and infinite velocities, it has been possible to remove the need for the multichannel analyser, sophisticated drive, strong source, large counting times and computer, all of which are normally required for Mossbauer spectroscopy. Some important design aspects of a portable ferritometer are discussed.

Journal ArticleDOI
TL;DR: In this paper, a combination of low mass, high compliance piezoelectric polymer transducers, a synchronized method for exciting the sample, and a small minicomputer capable of making digital Fourier transforms which convert the complicated, oscillatory, decaying signal from the transducers into the intensities and frequencies of normal modes is presented.
Abstract: The normal mode vibrational spectrum of a particular object contains a wealth of information about the mechanical integrity of the object. The non-destructive evaluation of objects by observation of their vibrational spectra is facilitated by the combination of recently developed low mass, high compliance piezoelectric polymer transducers; a synchronized method for exciting the sample; and a small minicomputer capable of making digital Fourier transforms which convert the complicated, oscillatory, decaying signal from the transducer into the intensities and frequencies of normal modes.

Journal ArticleDOI
TL;DR: The helium gas jet calibration technique has been shown by a number of workers in the field of acoustic emission to be a potentially powerful tool in the area of spectral analysis of acoustic emissions events as discussed by the authors.
Abstract: The helium gas jet calibration technique has been shown by a number of workers in the field of acoustic emission to be a potentially powerful tool in the area of spectral analysis of acoustic emission events. This paper outlines the work carried out to date at the Royal Aircraft Establishment, Farnborough and at the Admiralty Marine Technology Establishement, Poole, England in establishing a working procedure for this technique and the equipment used to performed the simple manipulation of spectra that is required. Test results are shown in order to demonstrate the ability of this technique to provide data which are directly comparable with those of other workers using the technique.

Journal ArticleDOI
TL;DR: In this paper, the effect of a pre-pressurization of 1100 MN/m 2 on the acoustic emission (AE) characteristics of a commercial low carbon steel has been investigated.
Abstract: The effect of a pre-pressurization of 1100 MN/m 2 on the acoustic emission (AE) characteristics of a commercial low carbon steel has been investigated. The results show that the pressurization decreases the AE intensity during the entire tensile test. A tendency for the upper and lower yield stress to be decreased is also noticed. This is probably caused by the formation of pressure-induced mobile dislocations and active dislocation sources at second phase particles.

Journal ArticleDOI
TL;DR: In this paper, an operational 150 kV microfocus rod anode X-ray system was described, which has ultra-high radiographic resolution and a focal spot size of less than 0.1 mm.
Abstract: This paper describes an operational 150 kV microfocus rod anode X-ray system which has ultra-high radiographic resolution and a focal spot size of less than 0.1 mm. Radiographic sensitivities of better than 1% through 3 mm of steel have been reported with film focal distances of the order of 8 mm. Long rod anodes are now possible with lengths up to 1 m or more and with diameters as small as 9 mm using mini-magnetic lens technology. This permits panoramic inspections; the system has been successfully applied to steam generator and heat exchanger tube-to-tubesheet weldments and also has applications where high reliability requirements, such as in marine and aircraft jet engine inspection, indicate the use of an ultra-sensitive radiographic technique.

Journal ArticleDOI
TL;DR: In this paper, two ultrasonic methods have been used to rate the cleanliness of steel plate, one based on the standard ASTM method, but with a modified counting system; the second, developed by the Centro Sperimentale Metallurgico (CSM), permits fullscale mapping of the flaws in a selected layer of the sample, i.e., sonography.
Abstract: Two different ultrasonic methods have been used to rate the cleanliness of steel plate. One in based on the standard ASTM method, but with a modified counting system; the second, developed by the Centro Sperimentale Metallurgico (CSM) permits fullscale mapping of the flaws in a selected layer of the sample, ie sonography. Using these sonographs a scale of macroflaws has been established; the CSM method also provides the possibility of obtaining sonographs which show the nature of flaws as well as their size and position. Computerized statistical analysis has shown significant correlations between the cleanliness rating and impact strength and the percentage of elements in the steel composition.