NDTnet 1998 Aug, Vol.3 No.8

Abstract

General hydrodynamic theory for liquid penetrant testing (PT) has been worked out in [1,2]. Ibis theory enables, for example, to calculate the minimum crack's width that can be detected by prescribed product family (penetrant, excess penetrant remover and developer) when dry powder is used as the developer. One needs for that such characteristics as surface tension of penetrant and some characteristics of developer's layer: thickness h, effective radius of Pores R_e and porosity . One more characteristic is the residual depth of defect's filling with penetrant before the application of a developer.The methods for experimental determination of these characteristics were worked out in [3].But there are two physical phenomena that were not taken into account in the frame of the theory [ 1,2], although our last researches demonstrate its principal significance for liquid penetrant testing. The aim of this study is to investigate these phenomena and to determine the restrictions on theory applicability. The first phenomenon is a sedimentation of developer's particles in a zone impregnated with a penetrant. As a result the thickness of developer's layer h*, appearing in formulas, is smaller than the thickness of dry zone. Our experimental results shows that in some cases h* is 80% smaller than h. The pictures illustrating the sedimentation influence upon the values of thickness for various developers are obtained. The estimation of this influence upon calculated sensitivity is carried out.Another phenomenon is so called two-side filling of one-side closed conical capillaries with liquids [4]. On the one hand the more penetrant is trapped by the defect the wider indication will appear. Contrariwise it is almost impossible to extract a penetrant from the completely filled surface defects of width value R< 70 µm by dry developer [3]. In this study we propose the theory of the phenomenon. Besides experimental results of the investigation of two-sides filling with various penetrants of conical capillaries are presented. Practical recommendations to optimize liquid penetrant testing process are proposed.

REFERENCES
1.P.Prokhorenko, N.Migoun. Proc. 7th ECNDT, London, 1987, v.4, p.2774-2782.
2.P.Prokhorenko, N.Migoun. Introduction To Liquid Penetrant Testing Theory, Nlinsk,"Nauka i Tekhnikw" Publishers, 1988, 207 p.
3.P.Prokhorenko, N.Migoun. Proc. 14th WCNDT, New Delhi, 1996, v.3, p. 1235-123 8.
4.N.Migoun et al. Comp. Rend. Acad. Sci. Paris, t.320, Ser.IIb,p354-350.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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