Method and apparatus to compensate for lateral changes of a ferromagnetic body during magnetic testing

US4763070A · kind A · utility

Assignee

• Nukem, LLC · DE

Inventor

• Gerhard Huschelrath · Laufach, DE

Key dates

• Filing date: Sep 20, 1985
• Grant date: Aug 9, 1988
• Expiry date: Sep 20, 2005

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N27/82
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A method and a device for non-destructive testing of ferro-magnetic bodies for structural faults by means of magnetization. The structural faults cause changes in the magnetic field which are picked up by stationary magnetic field detectors arranged close to the surface of the body, which are arranged perpendicular to the direction of magnetization of the body. The outputs of the magnetic field detectors are connected in a time-division multiplex manner to an evaluation unit. Predetermined positions of the magnetic field detectors are assigned compensation values in relation to the position of the respective weld, the compensation values being subtracted with the correct sign from the measured values produced by the magnetic field detectors. The corrected measured values obtained in this manner are subjected to a threshold value test to determine if structural faults are present. Furthermore, a lateral deviation of the weld from its original position is monitored. The compensation values are reassigned in accordance with the actual position of the weld with regard to the magnetic field detectors before the values are offset once more against the measured values.