Penetration flaw detection profile

Penetration flaw detection profile 

Penetration flaw detection is a non-destructive detecting   method that takes advantage of capillarity to detect material    surface flaw.at the beginning of 20th century, the earliest use  of kerosene with penetration ability to check on the crack of   motorcycle parts,To the early 40s, Ms (R.C.S WITZER) Invented   the penetration flaw detection fluorescent penetrants.the penetrants was widely used to check on military aircraft light alloy     parts during the second world war , and since then it has been one of the main nondestructive testing methods , and be used widely。

Penetration flaw detection including fluorescence method    and  staining  method ，fluorescence method is coating the penetrants with fluorescent   material on the surface of detected workpiece and    permeate into surface flaw by capillary , then wash the  penetrants what on the surface, and keep the penetrants contained in  flaw。 

To display ,typical visualization method is spread average   white powder on the surface of detected workpiece,sucked penetrants out from defect and extend to the surface,at this time ,   using ultraviolet lamp irradiate the surface in the dark,bright   fluorescence is shining on the defect.staining method is similar to fluorescent method,but the penetratnts do not contain fluorescent substance,the colored dye is included,so it makes penetratnes more visible ,and can be chenked on both white light and daylight。in general, the sensitivity of fluorescence is above staining method,both  methods include four fundamental steps :penetration,cleaning, visualization and check。

According to the methods of cleaning penetrants from detected workpiece,the fluorescence method and staining method of penetration flaw detection can be divided into washed-type、    after the emulsion type and type solvent to remove 。

Commonly used penetration flaw detection methods includ staining penetration flaw detection、fluorescent penetrant flaw detection, washed-type penetration flaw detection、solvent to remove flaw detection、dry imaging penetration testing、wet imaging penetration testing,we used to combine with diverse solutions to apply when actual flaw detection。Such as washed-type、solvent remove ,not   only used dry imaging penetration but also use wet imaging penetration。

Penetration flaw detection is easy to operate，it doesn’t need   complicated equipment, low cost，directly display flaw,equipped    with relatively high sensitivity,and it can detect flaw which width is lower than 1μm ,this method doesn’t restricted by material microstructure and chemical components 。

So it is widely used for black and non-ferrous metal、forging 、weldment、machined parts as well as ceramic、glasses、plastic and so on surface flaw detection。It can detect flaw、cold shut、fold、air hole and so on;but it is not applicable to powder metallurgy parts and other multihole material with loose structure ,picture 1is thermal stress crack on the shell found by staining method;picture 2 is weld crack found by fluorescence method。