Method and apparatus for nondestructive testing of ferromagnetic articles,to determine the location,orientation and depth of defects in such articles utilizing the barkhausen effect

Abstract

Abstract METHODS OF AN SYSTEMS FOR USE IN ELECTROMAGNETICALLY ANALYZING FERROMAGNETIC ARTICLES WHEREN A MAGNETIC FIELD HAVING AN INTENSITY IN WHICH THE BARKHAUSEN EFFECT IS SUBSTANTIAL IS INDUCED IN THE ARTICLE TO BE ANALYZED, AND A LOWFREQUENCY ALTERNATING MAGNETIC FIELD IS APPLIED TO AN AREA OF INTEREST OF THE MANGETIZED ARTICLE CAUSING THE MAGNETIC DOMAIN TO MOVE. A DETECTOR-COIL ASSEMBLY DISPOSED IN THE VICINITY OF THE LOW-FREQUENCY ALTERNATING MAGNETIC FIELD DETECTS THE MAGNETIC INTENSITY INDUCED IN RESPONSE TO THE MAGNETIC FIELD AND ALTERNATING MAGNETIC FIELD. IT HAS BEEN FOUND THAT THE MAGNETIC INTENSITY IN THE VICINITY OF A DEFECTIVE AREA ISOF A DIFFERENT MAGNITUDE THAN IN THE VICINITY OF A SOUND AREA, AND THIS INFORMATION IS USEFUL IN DETERMINING VARIOUS PARAMETERS OF THE ARTICLE. ONE SYSTEM MAKES A QUICK SCAN INSPECTION OF PIPE OF DETERMINE THE PRESENCE AND GENERALLY LOCATION OF DEFECTS. INM SUCH SYSTEM, SEVERAL TRANSVERSELY SPACED RESONATOR-DETECTOR UNITS LONGITUDINALLY TRANVERSE THE PIPE AND A RECORD IS MADE FROM EACH UNIT. INM A SYSTEM FOR ANALYZING A DEFECT, A RESONATOR-DETECTOR UNIT LONGITUDINALLY TRAVERSES THE DEFECTIVE AREA IN STEPPED TRANSVERSE INCREMENTS, AND THE DETECTED MAGNETIC INTENSITY IS RECORDED AND LATER PLAYED BACK AND FED INTO AN OSCILLOSCOPE FOR PICTORIAL REPRESENTATION AND PHOTOGRAPHIC. IN A SYSTEM FOR ANALYZING WELDS, THERE ARE SEVERAL TRANSVERSELY SPACED DETECTORS WHOSE OUTPUT SIGNALS ARE SEQUENTIALLY SAMPLED AND RECORDED. THE RECORDING IS LATER FED INTO AN OSCILLOSCOPE AND PHOTOGRAPHED. IN A SYSTEM MEANSURING THE RELATIVE WALL THICKNESS OF AN ARTICLE, THE SIGNAL FROM AN ARTICLE OF UNKNOWN THICKNESS IS COMPARED WITH A SIGNAL FROM AN ARTICLE OF KNOWN WALL THICKNESS. THE GENERATED SIGNALS, WHEN PROCESSED AND FED INTO AN OSCILLOSPCOPE, ARE DETERMINATIVE OF RELATIVE THICKNESS. A SYSTEM FOR MAKING RELATIVE WALL THICKNESS MEASUREMENTS ON A CONTINUOUS BASIS IS ALSO DISCLOSED.

Inventors

• 👤 Donald Lloyd

Bibliographic Details