摘要:

A broad overview of the field of laser‐ultrasonics is presented. This overview draws from developments at the Industrial Materials Institute of the National Research Council of Canada as well as elsewhere. The principles of generation and detection are presented, stressing a few key characteristics of laser‐ultrasonics: the material is actually the emitting transducer and transduction is made by light, thus eliminating any contact. These features carry both advantages and limitations that are explained. Another feature, which has been an impediment, is actually the complexity of the “laser‐ultrasonic transducer”, but in spite of this complexity, it can be made very reliable for use in severe industrial environments. It also can be very cost effective for a number of applications. Three applications that are now used in industry are presented: the inspection of polymer matrix composites used in aerospace, the measurement of thin layers in microelectronics and the thickness gauging of hot steel tubing in production. Technological aspects, such as interferometer design, detection lasers and others are also discussed. As an overall conclusion, laser‐ultrasonics that was for a long time a laboratory curiosity has definitely now made its transition to industry. Nevertheless, developments should continue to improve performance, to make it well adapted to specific inspection or characterization tasks and more affordable. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711602

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

This paper describes the challenges associated with the application of non‐destructive evaluation techniques to the civil engineering infrastructure. Significant inspection tasks and structural defect types are first defined. Theoretical bases and experimental requirements of several current NDE techniques are then described, where case studies of application of the described techniques to specific structures are highlighted. Limitations of the current technology in achieving the inspection goals are identified. Finally, discussion about future directions of civil structure NDE, in terms of newly developed and promising NDE techniques, is presented. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711603

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The elastodynamic boundary element method (BEM) is applied to the visualization of the scattered wave field through a fluid‐solid interface. In the formulation of BEM, the multigaussian beam model is introduced in order to express the incident wave field radiated from the immersion transducer. The unknown quantities on the crack boundary are determined by the BEM, then the wave field around the crack in solid is visualized with the integral representation of the scattered wave. To obtain the scattered waveforms in fluid, a far‐field expression of the Green’s function for a fluid‐solid coupling medium is adopted in this study. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711604

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A multi‐Gaussian beam model is described where the velocity field on the face of an ultrasonic immersion transducer is represented in terms of a large number of localized Gaussians. The versatility of this approach is demonstrated by using this type of model to represent both focused and planar probes, rectangular and circular probe shapes, and piston as well as non‐piston behavior. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711605

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Based on a simple second‐order thin layer asymptotic expansion for the transfer matrix, an explicit asymptotic solution for the stiffness matrix for a generally anisotropic piezoelectric thin layer is obtained. The total transfer/stiffness matrix for thick layers or multilayers is calculated with arbitrary precision by subdividing these layers into thin sublayers and combining recursively the thin layer transfer/stiffness matrices. It is shown that these methods converge to the exact solution and a hybrid transfer‐stiffness matrix combination provides the smallest computational error. The new method is computationally stable, efficient and easy to implement. To solve by this method the wave propagation in a semi‐space, the concept of a perfectly matched attenuating layer is introduced. The advantage of the method is that one does not need to compute the exact wave propagation solution for each anisotropic layer of the system and only the elastic constants of the layers are required. Examples are given for wave propagation in multidirectional composites and layered piezoelectric media. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711606

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Previous studies had shown that the mass‐spring lattice model (MSLM) is capable of accurately simulating two‐dimensional propagation, reflection, refraction, and scattering of ultrasonic waves. In the present work, models of ultrasonic probes were developed, and they were combined with the MSLM to develop a complete simulator of ultrasonic testing (UT). Several problems of typical ultrasonic testing were simulated using the developed UT simulator to demonstrate its capability to predict the waveform in ultrasonic tests. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711607

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A hybrid model is developed combining advantages of both semi‐analytical and numerical methods. Most of the propagation is computed semi‐analytically (pencil method, code Civa), while wave — defect interaction is computed numerically (FEM, code Athena) in a small region surrounding the defect. Both codes exchange results required to predict responses from defects through an integral formula extending Auld’s principle to the transient case. The theory and its implementation are discussed. Examples illustrate its interest in UT simulations involving complicated interactions. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711608

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Thick‐walled anisotropic components appear in some applications, e.g. in the nuclear power industry. The modeling of defects in such components is thus of practical importance. Hypersingular integral equations are here used to compute the scattering by rectangular and strip‐like internal cracks in a component of arbitrary anisotropy. The scattering is combined with models of transmitting and receiving contact probes. Numerical results are given comparing some rectangular and strip‐like cracks. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711609

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Measurements using laser interferometry have been performed to study the displacement response of Rayleigh waves in close proximity to a surface‐breaking crack. To gain a better understanding, numerical models for both infinite and finite crack cases were developed. Regions of intensification and decay were found to be highly localized around the crack site, and offer an advanced NDE technique for flaw characterization. Potential near‐field measures were proposed and evaluated with respect to variation in crack depth and angle. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711610

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

We develop measurement models and scattering models that allow us to predict the ultrasonic response from a side‐drilled hole (SDH). The scattering models considered include an explicit model based on the Kirchhoff approximation, as well as an “exact” separation of variables solution. Two measurement models are also derived. One allows for the variation of the incident fields over the cross‐section of the SDH while a simpler model neglects those variations. The predicted responses are compared with experimental signals. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711611

出版商:AIP    

年代:1904

数据来源: AIP