ISSN:1058-9759    

DOI:10.1080/10589759908952868

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1058-9759    

DOI:10.1080/10589759908952869

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Non-destructive inspection of concrete presents significant difficulties because of the presence of material inhomogeneities on a number of different scales. Many practitioners of ultrasonic testing view wave dispersion as noise when performing ultrasonic tests. However, significant information is present in the dispersion characteristics. Measurement of dispersion has the potential to separate the effects of inhomogeneities and damage because of differences in length scales. Wavelet decomposition makes it possible to measure dispersion using standard non–destructive testing equipment and a single receiving transducer. In this study two complex wavelet functions, the Paul and Morlet, are investigated. Unlike the Morlet wavelet, the Paul wavelet satisfies the admissibility conditions for a wavelet function with very few restrictions on the adjustment of wavelet parameters. The Paul wavelet may even be used to reproduce the MorJet wavelet scalograms. However, as a result of the broad admissibility, the Paul wavelet can also be adjusted for any required time–frequency resolution. The Paul wavelet can thus be "tuned" for a particular application to provide an optimal compromise between time and frequency resolution. Such tuning will be shown to be useful in the visualization of the dispersion due to damage in concrete.

ISSN:1058-9759    

DOI:10.1080/10589759908952870

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The assessment of the actual fatigue damage and thus the remaining lifetime of materials is a subject of enormous scientific and economical relevance. This paper describes investigations for the nondestructive characterization of microstructural changes of the metastable austenitic steel X6 CrNiTi 18 10 (AISI 321∥. Due to its good mechanical and technological properties, i.e. high toughness and corrosion resistance, AISI 321 is widely used in the chemical industry and power plant constructions. Experiments were carried out on sample batches fatigued at room temperature and T= 300°C. The nondestructive investigations and the interpretation of their results base on the knowledge of the cyclic deformation behaviour of the material. That is characterized by cyclic hardening and softening effects, which are strongly influenced by plasticity-induced martensite formation. Magnetic measurements with highly sensitive magnetometers on basis of HTC-SQUIDs yield good correlation with the actual fatigue state. The creation of martensite was found to be more significant as damage parameter than the dislocation density.

ISSN:1058-9759    

DOI:10.1080/10589759908952871

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Herein We Review Some Recent Progress In Delineating Quantitatively The Effects Of Crystallographic Texture On The Acoustoelastic Coefficients Of Polycrystals. A General Constitutive Equation In Acoustoelasticity Has Been Derived For Weakly-Textured Orthorhombic Aggregates Of Cubic Crystallites. Besides The Initial Stress, This Constitutive Equation Contains Seven Texture Coefficients And Twelve Material Constants. Two Micromechanical Models Are Currently Available To Estimate These Material Constants From The Second-Order And Third-Order Elastic Constants Of The Constituting Crystallites. The Predicted Values Of Two Rayleigh-Wave Acoustoelastic Coefficients Are InGood Agreement With The Results Of Measurements On Two Samples Of 6061-T6 Aluminum Alloy.

ISSN:1058-9759    

DOI:10.1080/10589759908952872

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Ultrasonics is being increasingly used for inspection of structural members to identify defects and material properties. Time-or-flight and velocity measurements are primarily used in these testing. While these measurements lead to a fair estimate of stiffness and flaw detection, the sensitivity of the measurements is not always adequate to detect flaws in their early stages. This paper proposes the use of power spectral analysis in conjunction with velocity measurements to identify defects in structural members. The conditions necessary to make repeatable amplitude measurements are described and the data analysis techniques suitable for flaw detection are also discussed. The advantages of using power spectral analysis are illustrated using examples of defective aluminum, wooden, and composite wrapped concrete members. The proposed measurement and analysis technique can be easily generalized to structural members made from other materials such as steel or reinforced concrete. Keywords: Ultrasonics; Amplitude measurements; Spectral analysis; Power spectral density; PSD

ISSN:1058-9759    

DOI:10.1080/10589759908952873

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The present paper was written with the aim of using the authors experience to provide a guideline for applying optical methods to the solution of mechanical problems, The question which this paper addresses is: when it is convenient to use optical methods and what kind of results must be expected? The aim is to write an easy to use handbook, hence the text differs from many scientific papers and will be introduced by a detailed flow-chart of the subject.

ISSN:1058-9759    

DOI:10.1080/10589759908952874

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The reflection of an axially incident plane longitudinal wave from a linear chain of identical spherical inclusions (glass or aluminum) embedded in a viscoelastic (polyester) matrix is measured. The reflection spectrum is characterized by a sequence of resonances corresponding to the kinematic condition, 2d= Nλ, where d is the interparticle distance, λ is the longitudinal wavelength, and N is a positive integer. The spectrum of a chain of inclusions of two different sizes arrayed in an alternating manner exhibits two sets of resonances.

ISSN:1058-9759    

DOI:10.1080/10589759908952875

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor