Principles
DPI is based upon capillary action, where low surface tension fluid penetrates into clean and dry surface-breaking discontinuities. Penetrant may be applied to the test component by dipping, spraying, or brushing. After adequate penetration time has been allowed, the excess penetrant is removed, a developer is applied. The developer helps to draw penetrant out of the flaw where an invisible indication becomes visible to the inspector. Inspection is performed under ultraviolet or white light, depending upon the type of dye used - fluorescent or nonfluorescent (visible).
Read more about this topic: Dye Penetrant Inspection
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“Magic is akin to science in that it always has a definite aim intimately associated with human instincts, needs, and pursuits. The magic art is directed towards the attainment of practical aims. Like other arts and crafts, it is also governed by a theory, by a system of principles which dictate the manner in which the act has to be performed in order to be effective.”
—Bronislaw Malinowski (1984–1942)
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“The principles of the good society call for a concern with an order of being—which cannot be proved existentially to the sense organs—where it matters supremely that the human person is inviolable, that reason shall regulate the will, that truth shall prevail over error.”
—Walter Lippmann (1889–1974)