Defect detection

Vagnhammar B., L.Ericsson, T. Stepinski and B. Grelsson, Improved defect detection in ultrasonic inspection of bonded structures. Report UPTEC 97 105R, Uppsala University, June, 1997... 

Representative set of weldments was examined site welds (with pearlitic type weld metal) and two types of site weld repair zones with different welding technologies using Cr-Ni filler metals and Ni-based alloy. Results of AUGUR 4.2 inspection were compared with manual ultrasonic inspection ones in terms of defect detection, characterization, positioning and sizing in order to estimate correlation between these data. 

All defects detected by manual inspection were detected by AUGUR 4.2 system. 

There were cases in which the extensive defect, detected by manual inspection, was cut into two or three isolated defects with small length by AUGUR 4.2 . 

The defects detection under the layer of any dielectric (varnish - colour, heat - insulation coating, sealant etc.) to 10 mm in thickness. 

Corrosive defects detection under the airframe skin and protective coatings. 

Inspection of load - carrying structures and mounting hardwares, the defects detection under side platings and dielectric shells in their attaching points to the load - carrying structures. 

Corrosive defects detection in the body load - carrying structures, engine parts, camshafts etc. 

Fourier transform is widely used for signal analysis purposes and is satisfactory when applied to signals where stationary features are of particular interest. However, it turns out to be very poor when dealing with defect detection, where it is the non stationary characteristics of the signal which has to be highlighted. The main reason is that in the Fourier analysis, the time parameter is discarded. 

Therefore, it seems natural to turn to time-frequency techniques in order to perform an efficient defect detection through the signal provided by the sensors. 

It can be observed from the Figure 1 that the sensitivity of I.I. system is quite low at lower thicknesses and improves as the thicknesses increase. Further the sensitivity is low in case of as observed images compared to processed images. This can be attributed to the quantum fluctuations in the number of photons received and also to the electronic and screen noise. Integration of the images reduces this noise by a factor of N where N is the number of frames. Another observation of interest from the experiment was that if the orientation of the wires was horizontal there was a decrease in the observed sensitivity. It can be observed from the contrast response curves that the response for defect detection is better in magnified modes compared to normal mode of the II tube. Further, it can be observed that the vertical resolution is better compared to horizontal which is in line with prediction by the sensitivity curves. 

In conclusion, segmentation reduces the huge amount of image information analysed, without loosing relevant details (defects). This work represents a preliminary decision assistance stage, that will facilitate the expert task in defect detection. 

The obtained results for the magnetic bench have allowed to note that defects situated at 12 mm of depth have been observed clearly. This is explained by the high power furnished by the bench, in addition its induction is double alternation rectified. Dimensions of the defect (height and width) are precisely estimated (figure 1). The defect detection at this depth is due to the application of a rectified field, so skin phenomenon is almost absent. 

Shear Horizontal (SH) waves generated by Electromagnetic Acoustic Transducer (EMAT) have been used for sizing fatigue cracks and machined notches in steels by Time-of-Flight Diffraction (TOED) method. The used EMATs have been Phased Array-Probes and have been operated by State-of-the-art PC based phased array systems. Test and system parameters have been optimised to maximise defect detection and signal processing methods have been applied to improve accuracy in the transit time measurements. 

As a result, the interference of the reflectional wave is shown the change for the position both the defects and the interfaces, and the size of the defect. And, the defect detection quantitatively clarified the change for the wave lengths, the reflection coefficient of sound pressure between materials and the reverse of phase. 

Wiberg, U Material Characterization and Defect Detection in Concrete by Quantitative Ultrasonics. Doctoral Thesis, KTH Stockholm. TRITA-BKN. Bulletin 7, 1993... 

Our near future improvements include automatic defect detection and reporting, and integration of reports into Word or Excel documents. On the long nin, automatic comparison with historical data will be possible, and if acquisition cards improve, acquisition may be perfomied by the analysis tools. 

Band gaps of semiconductors carrier lifetimes shallow impurity or defect detection sample quality and structure... 

Provide a form for conveying to the customer the results of any defects detected during receipt inspection, maintenance, or operational use. 

There are three phases in the evolution of most QC systems (1) defect detection where an army of inspectors tries to identify defects (2) defect prevention where the process is monitored, and statistical methods are used to control process variation, enabling adjust-... 

When using the defect-detection approach to quality control certain problems develop. Inspection does nothing to improve the process and is not very good at sorting good-from-bad. Also, sampling plans developed to support an acceptable quality level (AQL) of 5%, for example, say that a company is content to deliver or reject 5% defects. 

When the newborn population Is examined It Is found that between 2 and 4% of Individuals, depending on how the figures are calculated, have some type of birth defect which Is considered to be genetic In origin (8,9) The term "birth defect" Is used In a general sense and encompasses all types of structural, metabolic, and other abnormalities which derive from genetic or other prenatal causes. The birth defects detected postnatally represent only a small fraction of the totality of abnormalities which result from genetic aberrations, but most of the latter result In early spontaneous abortions... 

Defect detection on a wafer after CMP can be accomplished by a laser scanning technique and/or by a digital image comparison technique. Both types of tools are widely used in the industry. However, neither is sufficient... 

Another method of defect detection is digital image comparison. The tool works by comparing a pixel of one die to that of the preceding and... 

Black box testing is also known as functional testing, benchmark testing and, in the pharmaceutical community, as an operational qualification (OQ). It tests the functionality and correctness of a computer system by running the integrated software, and is performed for one of two reasons defect detection, and/or reliability estimation. It should cover all functions of the application software that the end-user will use, and will verily the completeness and accuracy of system requirements used to define the test cases. 

Most structural materials are susceptible to a wide range of defects. Any flaw alters the behavior of a structure, even if only minutely. The larger the flaw the more it reduces the useful properties of the material. One of the challenges in modem materials engineering is defect reduction. Defect reduction involves defect detection, defect source determination and mechanisms and defect elimination. There is no single method of detect review that can fully characterize every defect each defect classification method has its own strengths. 

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