Papers by Keyword: Probability of Detection

Abstract: Ultrasonic tests of dissimilar metal welds require extremely sophisticated technology. The complexity of the test is caused by the grain orientation and difficult accessibility of the weld and it is therefore necessary to redound the examinations by simulation. This study details some application possibilities of CIVA software and presents an example of the evaluation of the procedure used for the given test method with probability of detection curves.

Abstract: The performance and reliability of Structural Health Monitoring (SHM) techniques remain largely unquantified. This is in contrast to the probability of detection (POD) and sensitivity of manual non destructive inspection methods which are well characterised. In this study factors influencing the rates of emission of Acoustic Emission (AE) signals from propagating fatigue cracks were investigated. Fatigue crack growth experiments were performed in 2014 T6 aluminium sheet to observe the effects of changes in crack length, loading spectrum and sample geometry on rates of emission and the probability of detecting and locating the fatigue crack. Significant variation was found in the rates of AE signal generation during crack progression from initiation to final failure. AE signals at any point in the failure process were found to result from different failure mechanisms operating at particular stages in the failure process.

Abstract: Many factors impact on the performance of SAR-GMTI system. Besides of minimum detectable velocity (MDV), the performance of SAR-GMTI system is involved in probability of detection and probability of false alarm when considering the interference factors (such as thermal noise, phase drift and unbalance between channels, etc.) and the stationary clutter. These three features of SAR-GMTI system are related to the values of the number of looks, CNR, SCR, the radial velocity of moving targets and so on. However, there is no paper described how these factors impact on the performance of SAR-GMTI system systematically which will strongly support the study of improving detection performance. This paper analyses influence factors and provides a group of reasonable value of them for simulation.

Abstract: This paper studies a method based on synchronized prefix improved method, use a synchronous frequency method related to the system time (TOD) to generate the synchronization frequency, each synchronous frequency changes over time in constantly changing, thus protecting synchronous frequency, and sent low frequency TOD Is calculated out of the high TOD, which increases the difficulty of deciphering. the results of Performance Analysis show that TOD self-synchronizing synchronizing time is quick, the synchronized probability is big, good randomness, has met the project design anticipated requirements.

Abstract: In this paper, we address the problem of automatic inspection complex surface using an ultrasonic technique and the reliability of inspection. First, an automatic ultrasonic inspection manipulator is introduced. Through ultrasonic inspection and defect analysis, the parameters of flaws can be calculated automatically. Then, a POD analysis method is provided to assess the reliability of inspection. Finally, Experiments are conducted and the POD curves with the sizes of flaws and the scanning gaps are obtained.

Abstract: A statistical assessment model for structural integrity of steam generator tubes with axial cracks at the top of the tubesheet was proposed using Monte Carlo method. In the model, a method for estimating the number of "real cracks" from in-situ inspection (ISI) data was used. Based on the estimated "real cracks", the number of newly detected cracks and growth of cracks during arbitrary operating period were simulated using the Monte Carlo method. The flaw growth rate used in the simulation was statistically calculated from the periodic in-service non-destructive inspection data. The number of cracks, the probabilistic distribution of crack sizes at the end of next operating interval and the probability of burst during operation were calculated from numerously repeated simulations using the proposed model.

Abstract: Over the past two and a half decades there has been considerable progress made in the modeling of ultrasonic nondestructive evaluation (NDE) inspections. These models have also been combined with models of the noise and variability present in an inspection to estimate probability of detection (POD) versus flaw size curves. An overview will be given of the past and present accomplishments made in ultrasonic NDE modeling, POD modeling, and the relationship of those advances to reliability modeling that incorporates explicitly the results of inspections. A brief look into the future of this modeling technology will also be given.

Abstract: It is important to estimate the intensity distribution of a magnetic field as a possible magnetic method in an industrial nondestructive evaluation application. A magnetic camera provides the distribution of a quantitative magnetic field with homogeneous lift-off and same spatial resolution. Magnetic flux leakage near a crack on the specimen can be amplified by using a 3- dimensional magnetic fluid, that is to say a magnetic lens. This study introduces the experimental consideration of the effects of magnetic lenses for concentrating of magnetic flux. The experimental results showed that the magnetic fluid has a sufficient lens effect for magnetic camera and effect of improvement in probability of detection.