Defects/flaws

Fehler, m. error fault, defect, flaw mistake, -ausglekhung, /. equalization or compensation of errors. 

Ultrasonic waves have frequencies which are beyond human hearing. These wave are able to penetrate matter to some extent and the rest is reflected. The E modulus and the density of the material both determine at which speed the waves move through the material. The intensity of the penetrated or reflected beam is measured. The method is for instance used to track defects/ flaws in the material and to measure the E modulus. 

Tensile strength (Fig. 6), and strain (Fig. 7), continuously decrease with the increase in 0. This is a well known effect premature fracture occurs due to the amount of defects (flaws) which is directly related to the filler fraction. 

Selection of the NDE method(s) depends on the specific type of material, the type of defect/flaw to be analyzed, the environment of the evaluation, the effectiveness of the evaluation method, the size and thickness of the product, and other factors. The selection should also include the economic consequences of structural failure. However, there are always increasing demands for more accurate characterization of the size and shape of defects that may require available advanced techniques and procedures, and may involve the use of more than one method. 

This is also referred to as the ultimate tensile strength (UTS) and is expressed in psi or MPa. It is a maximum stress on the engineering stress-strain curve. It is an index of the quality of a material that is, it is a good indication of defects, flaws, or harmful inclusions present in the material. 

The main goal of ultrasonic grain noise suppression in material flaw detection is to improve the perceptual possibilities of the operator to observe defect echoes. The suppression is defined as perceptually ideal when a received signal (or image) which contains echoes buried in noise is filtered to yield nonzero values only at the positions of the defect echoes. 

Blind test data was classified 100% correctly between flawless and defect samples. Layer containing flaw was determined correctly in 97.2% of the cases (see Table 2 for details). 

We present a novel method, called VIGRAL, to size and position the reflecting surface of a flaw. The method operates on standard B-scan recorded with traditional transducers, to extract Time-of-Flight (ToF) information which is then back-projected to reconstruct the reflecting surface of the flaw and characterize its radiation pattern. The VIGRAL method locates and sizes flaws to within k/2, and differentiates between flat and volumetric defects. 

An invariant pattern recognition method, based on the Hartley transform, and applied to radiographic images, containing different types of weld defects, is presented. Practical results show that this method is capable to describe weld flaws into a small feature vectors, allowing their recognition automatically by the inspection system we are realizing. 

AUQUR 4.2 revealed a number of small-size defects with the height of about 2 mm did not detected by manual inspection. These flaws were located near the boundaries of cut-off zone of repaired welds and likely had originated after near-boundary passes of repair welding [3]. 

Anumber of defects with manual inspection indications clarified by AUGUR 4.2 records have been accepted for further operation in 1996 with prescription of next year AUGUR 4 2 inspection. Based on two consecutive inspections (1996-97 years) comparative analysis of AUGUR 4.2 data was executed. It was shown that the flaw configurations, reproduced by AUGUR 4.2 are stable and the small differences are conditioned only by system thresholds of linear coordinate and signal amplitude as well as variations in local conditions of in-site inspection. 

Information supplied by flaw visualization systems has decisive influence on fracture assessment of the defect. Results of expert ultrasonic examination show that in order to take advantage of AUGUR4.2 potentialities in full measure advanced methods of defect assessment should be applied using computer modelling, in-site data of material mechanical properties and load monitoring [4]. 

Using flaw visuahzation system data the strength and fracture mechanics estimations are carried out in accordance with defect assessment regulatory procedure M-02-91 [5]. Recently, the additions had been included in the procedure, concerning interpretation of expert flaw visualization sysf em data, computer modelling, residual stresses, in-site properties of metal, methods of fracture analysis. 

Now, we can make the comparison beween the real defect signal and the simulated one which have been computed by solving the linearized direct problem. The measurements were made at 300,150,50 kHz. The flaw is a notch of 8mm length, 1mm width, and 1mm depth. Representative data (300 kHz) for the notch-shaped flaw are shown in Fig. 3. 

Usually all the flaw detectors in service have two channels to detect defects of a rope the LMA and LF channels. The inspection information is recorded by a chart recorder or by a tape recorder. 

The Zond VD - 96 portable eddy-current flaw detector-tester is an original Russian development possessing heightened sensitivity for the surface defects and high inspection capacity. (Russia patent Xs 2063025. All-Union state standard certificate of Russian Federation JVa 2846 of 14. 07. 97)... 

The beam-defect interaction is modelled using Kirchhoff s diffraction theory applied to elastodynamics. This theory (see [10] for the scattering by cracks and [11] for the scattering by volumetric flaws) gives the amplitude of the scattered wave in the fonn of coefficients after interaction with defects and takes account of the possible mode-conversion that may occur. 

Manual ultrasonic testing offers the advantages of low equipment cost combined with the flexibility of the human operator to provide good access and complex scanning capability. However, a total reliance on the capabilities of the ultrasonic technician to visualise the physical situation leads to a number of drawbacks, including lack of accuracy and consistency of defect size and location measurements, lack of verification that the required scan coverage has been fully achieved, and lack of consistency in flaw classification. A further disadvantage is that the ultrasonic data is not permanently recorded there is therefore no opportunity for the data to be re-examined at a later date if required. 

In this paper, the following aspects have been studied (A) Flaw detection can be made directly on the surface of the pipes, (B) The defects within the range of wall thickness can be tested out, that is to say, the ultrasonic testing without dead zone for the pipe wall can be realized and (C) Testing the defects of FBH as our testing. Objects, we may make the testing... 

With the reference block method the distance law of a model reflector is established experimentally prior to each ultrasonic test. The reference reflectors, mostly bore holes, are drilled into the reference block at different distances, e.g. ASME block. Prior to the test, the reference reflectors are scanned, and their maximised echo amplitudes are marked on the screen of the flaw detector. Finally all amplitude points are connected by a curve. This Distance Amplitude Curve (DAC) serves as the registration level and exactly shows the amplitude-over-distance behaviour" of the reference reflector for the probe in use. Also the individual characteristics of the material are automatically considered. However, this curve may only be applied for defect evaluation, in case the reference block and the test object are made of the same material and have undergone the same heat treatment. As with the DGS-Method, the value of any defect evaluation does not consider the shape and orientation of the defect. The reference block method is safe and easy to apply, and the operator need not to have a deep understanding about the theory of distance laws. 

From polarization curves the protectiveness of a passive film in a certain environment can be estimated from the passive current density in figure C2.8.4 which reflects the layer s resistance to ion transport tlirough the film, and chemical dissolution of the film. It is clear that a variety of factors can influence ion transport tlirough the film, such as the film s chemical composition, stmcture, number of grain boundaries and the extent of flaws and pores. The protectiveness and stability of passive films has, for instance, been based on percolation arguments [67, 681, stmctural arguments [69], ion/defect mobility [56, 57] and charge distribution [70, 71]. 

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