Method and apparatus for measuring and precisely locating internal tensile stresses in hardened regions of components by measuring coercive field strength and barkhausen noise amplitude

US4881030A · kind A · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Erwin Stuecker · Oberhausen, DE
• Gerhard Hofer · Königsee, DE
• Dietmar Koch · Gummersbach, DE
• Uenal Guenes · Erlangen, DE

Key dates

• Filing date: Apr 18, 1988
• Grant date: Nov 14, 1989
• Expiry date: Apr 18, 2008

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N27/725
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A method and apparatus for ascertaining internal stresses in a hardened region to be tested for a component made of a predetermined material includes measuring coercive field strength and amplitude of magnetic Barkhausen noise as a function of mechanical stress and hardness in calibration samples of a predetermined material of known hardness and known internal stress. Calibration functions are ascertained from the measured values indicating the dependency of the hardness and the amplitude of the magnetic Barkhausen noise as functions of the hardness and mechanical stress. The coercive field strength and the amplitude of the magnetic Barkhausen noise is measured in a location-dependent manner over the region of the component to be tested. The measured values of the coercive field strength and the amplitude of the magnetic Barkhausen noise are converted in the region to be tested into location-dependent hardness and into location-dependent mechanical stress using the ascertained calibration functions. The location-dependent mechanical stress and the location-dependent hardness in the region to be tested are present independently of one another and are available for further processing…