Radiographs

Nondestructive testing techniques for welded joints usually include visual, radiographic, magnetic particle, liquid penetrant, and ultrasonic testing methods. Of interest in this paper is the radiographic testing (RT) technique. 

It allows to save the radiographic film in computer for an eventual digital processing. In our case welded joints radiographic films are digitized in 256 gray levels. 

We present in this paper an invariant pattern recognition method, applied to radiographic images of welded joints for the extraction of feature vectors of the weld defects and their classification so that they will be recognized automatically by the inspection system. 

Radiographic inspection is performed to reach a decision about the acceptability of the component or product being tested. Before any evaluation can be made, the interpreter must be certain that the images are satisfactory. In addition, the interpreter must have a solid understanding of the following in order to be successful with the interpretation of the radiographic film for welding quality. 

We present in table 1 and table 2 the results of the application of tlie DHT on two edge images of two welded Joints radiographic films containing a lack of penetration in the first and a... 

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. 

Figure 3 A radiographic image of a welded joint (defect lack of penetration), a Original image, b Edge image (only the defect is maintained).

The draft standard was then developed so that it was possible to classify both types of film in separate groups. The first being a Classical film, the second a Wide Latitude film. The density range of the standard covered from D=2.0 to D=4.0. A radiographer would expect the contrast to be higher at D=4.0 than the contrast at D=2.0. 

The paper presents the results from systematic comparisons of contrast and resolution obtained with different types of radiation sources on steel thicknesses from 5 to 40 mm. These results have been taken into account with the definitions of the European standard for radiographic inspection of weldments (EN 1435) that is approved since 1997. Conclusions from practical investigations on pipe line sites, in petrochcemical plants and in nuclear power stations will be discussed as well. Furthermore, the presentation will stipulate a variety of advantages obtained from the new source in terras of coUimation and radiation protection. 

The results undoubtedly show a significant improvement of eontrast of Selenium radiographs compared to Iridium in the eomplete range of wall thicknesses as can be foreseen by the difiference in radiation energies. 

Introducing the Selenium for gammagraphic weld inspection at significantly improved quality levels of the radiographs we have also designed an exposure unit for Selenium. This unit is fuUy compatible with both models, M6 and Ml8. Different from the exposure units for iridium, which are Type B(U) containers, the Source Projector M-SE for Selenium is a Type A container with a maximum loading of 3 TBq (80Ci) Selenium. 

The efficiency of gas turbines is limited by the maximum allowable turbine inlet temperature (TIT). The TIT may be increased by cooling of the blades and vanes of the high pressure turbine. Cooling channels can be casted into the components or may be drilled afterwards. Non-conventional processes like EDM, ECD or Laser are used for drilling. Radiographic examination of the drilled components is part of the inspection procedure. Traditional X-Ray film technique has been used. The consumable costs, the waste disposal and the limited capacity of the two film units lead to the decision to investigate the alternative of Real-Time X-Ray. 

Crack Detection in Digitized Radiographs with Neuronal Methods. 

The radiographs were made from austenitic (titanium- or niobium-stabilised nickel chromium steels) welds that were double-wall penetrateted by x-rays of 130kV. The wall thiekness is in the range of 8 to 12 mm. 

Undercuts and cracks are represented in the digitised radiograph as local greyvalue minima (see Fig. 2). This motivates the application of edge-detecting operators. 

As described above 2314 ROIs were cut out of several radiographs of austenitic welds and the accessory feamres were calculated. The true data for each radiograph is known by destructive testing and evaluation. The ROIs represent the following dataset ... 

Fig. 7 Radiograph with indication marks set by a neuronal network...

Imaging plates are exposed similar to radiographic films. They are read out by a LASER-scanner to a digital image without any developing process. After optical erasing of the virtual picture the same IP can be used cyclic up to more than 1000 times. The life time is limited by the mechanical stability of the IP s. An IP consists of a flexible polymer carrier which is coated with the sensitive layer. This layer is covered with a thin transparent protective foil. 

A 3D summation tomographic image is generated and layers in any direction may be viewed. Image quality is improved by filters. The method has been proved satisfactory on a high radiographic contrast cylindrical object and on more complex items. 

Performance Synthesis in Digitizing and Processing Radiographic Inspection. 

For safety reasons, the main components of industrial installations must undergo NDT so as to guarantee the functional capacities of equipment by verifying the integrity of the materials. This paper presents the EDF project to improve the quality for detection, localization and characterization of incoming faults inside materials, and to increase the performance of X or y radiographic analysis. 

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