摘要:

Delamination can occur in composite materials either at the manufacturing level or during in-service applications. Such defects may be due to interlaminar shear stresses greater than a threshold stress value and may reduce the compressive strength and fatigue life of a composite. Furthermore, delamination may grow under service load and induce a loss in the residual strength of a structure. Thus, understanding the process of delamination growth may help in understanding the failure mechanisms involved in composite Materials and improve safety limits. Therefore, a non-destructive inspection technique capable of accurately detecting and quantifying delamination is required. In this article, it is demonstrated that a commercial eddy current instrument could be used to accurately detect and quantify delamination in a carbon fibre reinforced composite sample. The feasibility of monitoring delamination growth in such materials is also shown.

ISSN:1058-9759    

DOI:10.1080/10589759908952865

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In the present investigation, an optical corrosion-meter has been developed for materials testing and evaluation of different corrosion phenomena. The idea of the optical corrosion-meter was established based on principles of 3D-holographic interferometry for measuring rnicrosurface dissolution, i.e, mass loss, and on those of electrochemistry for measuring the bulk electronic current, i.e, corrosion current of metallic samples in aqueous solutions. In the present work, an early stage of pitting corrosion of a stainless steel and a carbon steel in seawater was monitored in situ by the optical corrosion-meter during the cyclic polarization test. The observations of pitting were basically interferometric perturbations detected only on the surface of the stainless steel in seawater. The interferometric perturbations interpreted as a localized corrosion in a form of early pittings, of a depth 0.3 to several urn.Consequently, results of the present work indicate that holo-graphic interferometry is very useful technique as a 3D-interferometric microscope for monitoring pittings at the initiation stage of the phenomenon for different metallic samples in aqueous solutions.

ISSN:1058-9759    

DOI:10.1080/10589759908952866

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The electrical conductivity σ and the magnetic permeability μ are the basic material properties that describe the interaction between an eddy-current sensor and a sample, They are connected strongly to technologically relevant quantities and thus have to be determined for a complete characterization of the material. This work presents a method to evaluate conductivity and permeability by eddy-current measurements. Since appropriate calibration samples are not available, the necessary calibration procedure is performed by simulation of the measurement. The nonlinear magnetic effects, which are small but not completely avoidable. afford an approximation that leads to the definition of an effective permeability μeff. The comparison of the eddy-current results with reference values, which are obtained by other techniques, reveals a deviation less than 9% in σ and less than 14% in μeff.

ISSN:1058-9759    

DOI:10.1080/10589759908952867

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor