ISSN:0094-243X    

DOI:10.1063/1.1570114

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper presents an overview on current activities and results concerning NDE of material degradation by embrittlement and fatigue. In general we differentiate between NDT methods for the characterization of embrittlement and fatigue which are either microstructure or crack sensitive. At the present time there is no reliable NDE technique known which can be used on technical components to detect the onset of failure during the early stages of embrittlement and fatigue. Therefore, microstructure sensitive methods are required which have potential for detecting degradation during the early stages and for infield capability. Such methods are micro‐magnetic methods, eddy current methods and thermal methods. These techniques, however, have only been tested under laboratory conditions to date. The micro‐magnetic method will be discussed concerning embrittlement. Results on eddy current testing by using GMR and thermal methods are documented concerning fatigue characterization. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570115

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Guided waves are very attractive for the rapid inspection of large structures. However, until recently the number of practical applications has been limited. This is largely due to the presence of many possible wave modes, most of which are dispersive, which can lead to high levels of coherent noise. Techniques to manage this complexity are discussed and practical applications to pipes, railroad rail, plates and rock bolts are described. Areas for future research are then suggested. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570116

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper presents a method for 3D elastic wave scattering analysis by an obstacle in a thick plate. The method is a coupling method of the boundary element method (BEM) and the generalized ray theory (GRT). For computational efficiency,the free field displacement in a plate is calculated by the GRT, and the solution is used as an incident field in the successive BEM analysis. The displacements or the tractions on the surface of the scattering object are obtained by the BEM. The boundary values obtained thus are then substituted into the integral expression of the scattered waves, in which the Green’s functions are evaluated by the GRT to reduce computational cost further. As a numerical example, the scattering by a spherical cavity embedded in a plate is solved. The numerical results are shown for displacement waveforms as a function of time at points on the cavity and plate surface. Through the numerical example, benefit of the proposed method is discussed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570117

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper presents a new set of boundary conditions to be enforced on an elastodynamic wave interacting with a nonlinear interface. They are formulated within the framework of the quasi‐static approximation, and model the effect of defects on the interface properties by means of two distributions of nonlinear springs. The nonlinear terms are derived from the micromechanics of two rough surfaces in contact. Numerical results are presented both for normal and oblique incidence. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570118

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

It is of importance in ultrasonic NDE to know how crack roughness effects the quality of inspection. Rough crack face was modeled in the past as a mosaic of large triangles using the Kirchhoff approximation. On the other hand, until now rough crack edge was modeled only under assumption of small perturbation. In this paper, in the spirit of the triangular facet model we model rough crack edge as a polygonal line and then apply the Isakovich approach which was developed for scatter from rough surfaces and is also based on the Kirchhoff approximation. For simplicity, we deal with a planar crack. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570119

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The scattering of elastic waves by a rectangular crack in a half‐space of arbitrary anisotropy is considered. The scattering problem is formulated as a hypersingular integral equation for the crack‐opening‐displacement by means of the half‐space Green’s tensor, which is solved by expanding in a double series of Chebyshev functions. Models of transmitting and receiving transducers give a complete model of ultrasonic testing. A few numerical examples are given. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570120

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

In the present study, a 3D hybrid method, which couples the finite element region with guided elastic wave modes, is formulated to investigate the scattering by a non‐axisymmetric crack in a welded steel pipe. The algorithm is implemented on a parallel computing platform. Implementation is facilitated by the dynamic memory allocation capabilities of Fortran 90™ and the parallel processing directives of OpenMp™. The algorithm is validated against available numerical results. The agreement with a previous 2D hybrid model is excellent. Novel results are presented for the scattering of the first longitudinal mode from different non‐axisymmetric cracks. The trend of the new results is consistent with the previous findings for the axisymmetric case. The developed model has potential application in ultrasonic nondestructive evaluation of welded steel pipes. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570121

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

An ultrasonic wave propagating through a microscopically inhomogeneous medium, such as polycrystalline materials, is subject to scattering at the grain boundaries. The fraction of energy removed from the incident wave is responsible for important phenomenon like attenuation, dispersion, and background “noise” associated with a given ultrasonic inspection system. Since the backscattered signals tend to mask the signals from small and subtle defects, the estimation of probability of detection of such defects requires the quantitative description of these signals. Although considerable attention has been given to the understanding of mean propagation characteristics of an ultrasonic beam, until recently there have been relatively little efforts devoted towards rigorous treatments of backscattered signals. In this research, we attempt to include some degree of multiple scattering in the calculation of the backscattered signals by developing a formalism that relates mean wave propagation characteristics to the noise. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570122

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

A Multilevel Multipole method is presented for modeling elastic wave multiple scattering in fiber‐reinforced composites. Results are given for the case of an incident SH wave impinging on a bounded Ti/SiC composite region, the plane of propagation being orthogonal to the fibers’ axis. The scattering effects of a square and hexagonal arrangement for the fibers are compared. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1570123

出版商:AIP    

年代:1903

数据来源: AIP