摘要:

Laser‐generated ultrasound combined with either a confocal Fabry‐Pe´rot interferometer (CFPI), a Mach‐Zehnder interferometer, or a capacitive air‐coupled transducer was used to locate both embedded and surface discontinuities in moving bulky steel specimens. The aim was to find an optimal remote sensor. Requirements imply single‐sided access and minimal surface damages. Performed tests in an industrial environment demonstrate perceptible advantages of the CFPI detector permitting stable single‐shot measurements at speeds up to 10–15 m/s. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711792

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Ultrasonic compression wave spectrometers have potential for monitoring colloidal and emulsion materials contained in optically opaque pipework or vessels. This paper considers the underlying physics for such systems and the design issues associated with the physical constraints of process pipework and the noise performance of associated electronic equipment. The paper concludes with a design protocol that would enable rapid development of a process instrument. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711793

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Ultrasonic and dielectric cure monitoring techniques have been used to characterize the cure of a typical epoxy‐amine adhesive over a range of different cure conditions. The time‐temperature‐transformation (TTT) diagram has been used as a generic representation of the data to facilitate comparison between the two techniques. This paper discusses the similarities between the evolving dielectric and ultrasonic properties of the thermoset by investigating the dielectric and ultrasonic loss tangents and the relaxation phenomena observed in each case. Both techniques are shown to be sensitive to variations in cure temperature although for a fixed test frequency the dielectric technique seems to be more sensitive to changes in the early stages of cure whereas at the same frequency the ultrasonic technique appears to be more sensitive to the final stages of the process. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711794

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

The mechanical properties of thermoset adhesive layers depend greatly on the cure conditions, such as cure temperature and duration. Ultrasonic measurements of the cure state of thermosets have been shown to be very sensitive to variations in these process conditions. In this paper a further parameter affecting the cure state of thermoset layers is considered. The thickness of an adhesive layer is shown to have a significant effect on the final properties of the thermoset. We suggest that the exothermic nature of the cure reaction is causing significant temperature gradients to occur within adhesives layers during cure leading to a variation in properties across the layer together with the possibility of decreased bondline strength. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711795

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

As NDE simulation tools begin to find more widespread use in critical engineering applications, it is becoming increasingly important to quantify their accuracy. The long‐range goal of simulator development is to develop a suite of tools that can be used throughout the world to predict the results of NDE measurements. However, in many simulations, various approximations are made to speed the computations or increase flexibility and user friendliness. It is therefore necessary to define the range of conditions over which particular models can be used with confidence. This paper summarizes an ultrasonic model benchmarking activity that is being conducted by the World Federation of NDE Centers. The first two phases of this activity involved the comparison of the predictions of a series of models for a set of benchmark problems involving well‐defined experimental geometries and input signals. Those results will be reviewed. In many cases, the models were found to be in good agreement. However, regions were identified that require further attention. Lessons learned will be summarized and actions that have been taken will be discussed. The final step in qualifying a simulation tool for industrial use is a validation against experimental data. Plans for a set of validation experiments, to be conducted during coming years, will be summarized. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711796

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

A review is given of the primary modeling strategies that have been used to model ultrasonic NDE systems in a recent series of ultrasonic benchmark studies. Ultrasonic beam models, flaw scattering models, and ultrasonic system measurement are all discussed. Some of the main characteristics of those models are described as well as their advantages and disadvantages. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711797

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

Measurements and numerical experiments are reported for a sub‐set of the problems defined as the Ultrasonic Benchmark 2002 by the World Federation of Nondestructive Evaluation Centers. The backscatter from cylindrical voids of 0.125, 0.5, 1.0, 2.0, and 4 mm radii in an Aluminum block for an incident plane longitudinal elastic wave has been numerically evaluated using one exact and one approximate solution and compared. The exact solution is based on the separation of variables method. The approximate solution is based on Kirchoff’s approximation. Within the Thomson‐Gray measurement model and the paraxial approximation for the transducer beam, the peak‐to‐peak voltage is computed as a function of void radius using the exact and approximate backscatter solutions. Using a prescribed reference RF signal waveform, the backscattered RF flaw signals are predicted. Within the Kirchoff’s approximation, the backscatter from partially illuminated cylindrical voids is evaluated as a function of the fractional area illuminated. RF signal waveforms were measured for cylindrical voids of 0.5, 1.0, 2,0 and 4.0 mm radii in an Aluminum block under a normal incidence immersion method. The RF signals were also measured, as the transducer was scanned perpendicular to the cylindrical void axis. Measurements were also carried out to obtain the backscatter from solid cylinders of various radii immersed in water. Comparisons between predicted peak‐to‐peak voltages and measurements are made. Attention is drawn to the transition from 2D backscatter to 3D backscatter encountered when seeking comparisons between predictions and measurements. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711798

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

This paper presents results obtained by simulating the second magnetic flux leakage benchmark problem proposed by the World Federation of NDE Centers. The geometry consists of notches machined on the internal and external surfaces of a rotating steel pipe that is placed between two yokes that are part of a magnetic circuit energized by an electromagnet. The model calculates the radial component of the leaked field at specific positions. The nonlinear material property of the ferromagnetic pipe is taken into account in simulating the problem. The velocity effect caused by the rotation of the pipe is, however, ignored for reasons of simplicity. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711799

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

This work presents numerical results obtained by simulating the first eddy current benchmark problem proposed by the World Federation of Nondestructive Evaluation Centers (WFNDEC) as part of an international effort. The problem involves prediction of responses generated by eddy current coil sensors scanning an inconel tube containing a defect. A variety of defect geometries are considered both in the presence as well as absence of a ferromagnetic support plate. The simulations involved the use of A‐V formulation based finite element method (FEM). © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711800

出版商:AIP    

年代:1904

数据来源: AIP

摘要:

In this paper a third eddy current benchmark problem is considered. The objective of the eddy current benchmark problem is to determine optimal operating frequency and size of the pancake coil designated for testing tubes made of Inconel. The problem considered in this paper is a true three‐dimensional one and should be modeled using numerical methods, e.g. finite element method, however, because the solution times involved are very large, we present a simplified analytical approach. Moreover, analytical solutions are useful for determining the efficiency of numerical methods and for a qualitative presentation of the role of various system parameters. © 2004 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1711801

出版商:AIP    

年代:1904

数据来源: AIP