Optics: measuring and testing – Inspection of flaws or impurities – Having predetermined light transmission regions
Patent
1995-07-26
1997-02-25
Gonzalez, Frank
Optics: measuring and testing
Inspection of flaws or impurities
Having predetermined light transmission regions
356388, 356392, 356394, G01N 2100
Patent
active
056064101
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for controlling or checking the surface state of one face of a solid. It also relates to a device for performing this method and intended both for equipment assisting an operator and for an automatic control installation.
BACKGROUND OF THE INVENTION
For various reasons, it is often necessary to control, inspect or check the surface state of one or more faces of a solid and this is more particularly the case with laminated nuclear fuel.
One variety of nuclear fuel for experimental reactors is constituted by aluminium sandwich plates with a core made from a mixture of uranium and aluminium. The production process of said plates consists of laminating together four components, namely a compacted aluminium and uranium core mounted in a frame and covered by two plates forming a cover.
Although highly industrial, this production process requires several manual operations and know-how, so that there are variations in the quality of manufacture. However, as these products are particularly sensitive, they require very precise characteristics imposed by the users. These requirements concerning quality give rise to internal and external controls of the fuel plates.
The internal control takes place by special machines using ultrasonics or X-rays. The control takes place automatically and gives rise to reports combining quantitative and calibrated measurements.
The external control has hitherto been performed visually by qualified operators. The procedure involves observing two surfaces of a plate under glancing light, whilst manipulating the plate and locating or pinpointing surface defects. The latter are holes or scratches, whose depth must not exceed 100 .mu.m. When a surface defect appears suspect to the operator, he places the plate beneath the objective of a microscope and evaluates the maximum depth of the hole or scratch previously located. Plates having characteristics falling outside the standard are disposed of as waste. Certain users have particularly strict requirements, which requires a supplementary control performed by another team.
This external control, which is entirely the responsibility of human evaluation, suffers from a number of disadvantages. It is fastidious and tiring due to the concentration and acuity required. Its reliability is dependent on the state of vigilance, which varies in time and between individual operators. In the case of a second control, when the quality tends towards 100%, it remains virtually impossible to maintain the necessary vigilance for detecting the very rare defect or objectively impose acceptance limits. In addition, visual measurements offer no quantitative and objective basis for the support of a control or inspection report.
The invention makes it possible to improve the control of surface states and is applicable both to equipment used by an operator and to an automatic control installation. The observation conditions are improved by photographing the surfaces to be controlled, said photographs either being presented on a video screen at a control station, or are digitally processed in the case of an automatic control installation. The use of an optoelectronic probe makes it possible to obtain objective and quantitative depth measurements, which can be recorded.
SUMMARY OF THE INVENTION
The invention therefore relates to a method for controlling the surface state of one face of a solid for locating shape defects liable to be located there and comprising: constitute defects, limit size implying the existence of a defect, if said areas are or are not defects, place by measurement using an optoelectronic probe.
The observation of the face of the solid advantageously takes place under glancing, multidirectional illumination.
Preferably, photography or filming takes place by video and in two successive stages, a first or so-called large field analysis stage makes it possible to rapidly pinpoint all the areas liable to constitute defects and a second or so-called small field analysis stage, which only applies to the ar
REFERENCES:
patent: 3864564 (1975-02-01), Adkins
patent: 4451929 (1984-05-01), Yoshida
patent: 4733963 (1988-03-01), Date et al.
"Mikromechanische Strukturen Optisch Messen", Feinwerktechnik & Messtechnik, vol. 100, No. 6, Jun. 1992, pp. 255-258.
Laurent Pierre
Peclier Roger
Piquard Jean-Fran.cedilla.ois
Compagnie Generale des Matieres Nucleaires
Gonzalez Frank
Ratliff Reginald A.
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