摘要:

In the 2001 RPQNDE conference, a series of ultrasonic benchmark problems were compared using different model‐based approaches [1–5]. Here, an extended set of benchmark problems are considered. Paraxial beam models are used in conjunction with various measurement models to demonstrate the effects of various modeling assumptions on the waveforms predicted for these benchmark problems. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570344

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

In the present study, the radiation issues related to the ultrasonic benchmark problems of year 2002 are explored by adopting two ultrasonic measurement models based on 1) the multi‐Gaussian beams and 2) the Rayleigh‐Sommerfeld integral with high frequency approximation, while keeping the choice of scattering model (the plane wave far‐field scattering amplitude estimated by the Kirchhoff approximation) unchanged. The insonifying beam fields and flaw signals calculated by two models showed very good agreement in most of the cases. However, they showed significant difference at the near‐critical angle (which is corresponding to the cases of refracted S‐waves with the refracted angle of 30°) due to the rapid variation in the transmission coefficient in that region. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570345

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Using a point source superposition method, the signals from spherical, cylindrical and crack‐like reflectors observed in a pulse‐echo measurement are predicted. Normally incident longitudinal waves as well as obliquely incident transverse and longitudinal waves, generated by circular focused and unfocused transducers, respectively, of 5 MHz center frequency are assumed in an immersion geometry. Three sets of scattering objects are considered: spherical pores, cylindrical scatterers and circular cracks of various diameters. The problem addressed in this contribution is an extension of the 2001 UT Benchmark Problem [1]. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570346

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The Thompson‐Gray ultrasonic measurement model is applied to two benchmark problems. The first problem considers the ultrasonic reflection from spherical pores and side‐drilled holes (SDH) for normally incident longitudinal waves. The second problem examines refracted longitudinal and shear wave reflections from both SDH and spherical pores. Results are obtained for both planar and spherically focused transducers. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570347

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper discusses some practical configurations for finding flaws in well‐conducting materials using the eddy‐current non‐destructive method (NDT). In order to increase the sensitivity of impedance changes the optimisation of all properties of these systems e.g. design and dimensions of the coils, their positions, frequency and measuring system has been carried out. Based on these results some requests are formulated for the developer of NDT‐sensors. This project has been carried out as the World Federation Second Eddy Current Benchmark Problem. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570348

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper presents computational results of the second eddy current benchmark problem proposed by the World Federation of Nondestructive Evaluation Centers. The problem involves the prediction of the change in impedance of a pancake coil as it scans the inner surface of a metal tube along both the axial and circumferential directions for detection of flaws on the outer surface. A finite element scheme is carried. The real and imaginary part of the impedance is obtained by observing the total stored energy and the dissipated energy, respectively. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570349

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This experiment involves the measurement of the magnetic flux leaked from a rotating seamless steel tube with two machined notches. The signal measured is the radial component of the leaked field at a fixed point in space, as a function of the notch position, for four values of the liftoff and two notches. As the pipe tangential velocity was varied between 0.23 and 0.62 m/s, the sole observed effect was that of increasing the signal by a value that grows linearly with the velocity and is independent of the notch angular position. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570350

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Numerical results predicted by the finite element method based code are presented. The nonlinear magnetic time‐dependent benchmark problem proposed by the World Federation of Nondestructive Evaluation Centers, involves numerical prediction of normal (radial) component of the leaked field in the vicinity of two practically rectangular notches machined on a rotating steel pipe (with known nonlinear magnetic characteristic). One notch is located on external surface of pipe and other is on internal one, and both are oriented axially. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570351

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper examines the validity of statistical methods for determining nondestructive inspection probability of detection (POD) curves from relatively small hit/miss POD data sets. One method published in the literature is shown to be invalid for analysis of POD hit/miss data. Another standard method is shown to be valid only for data sets containing more than 200 observations. An improved method is proposed which allows robust lower 95&percent; confidence limit POD curves to be determined from data sets containing as few as 50 hit/miss observations. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570352

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Damage tolerance‐based operation and maintenance of aircraft components require the estimation of probability of detection (POD) of nondestructive inspection (NDI) techniques. The standard approach to estimate POD of an NDI process is to perform demonstration tests on simulated or real components. To generate a realistic POD, MIL‐HDBK‐1823 suggests that flaw sizes should be uniformly distributed on a log scale covering the expected range of the POD curve in the transition region. This paper presents an alternative approach that is based on Rayleigh distribution of flaw sizes on a log scale covering the expected range of flaws. This approach is only applicable to NDI methods that provide a signal response or “a⁁” for a given flaw size “a”. The use of this approach increases the accuracy of the POD estimate by optimizing the distribution of flaw sizes in the range of transition between very low and very high POD. The paper also presents a new three dimensional representation of POD versus the false call rate, defined by the relative operating characteristic (ROC). The 3D presentation makes it easier to visualize the change in POD and false call rate with the variation of decision threshold set for flaw detection. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570353

出版商:AIP    

年代:1903

数据来源: AIP