Hardness, case depths and crack testing of critical automotive components with eddy current

Quality differences such as hardness and case depths at metallic materials can be evaluated non-destructively by measuring the different magnetic and/or electrical properties of such components. The separation of good hardened and bad hardened parts is demonstrated for ball studs, gear wheels and crown gears. A technical highlight of the test equipment in use is the induction of strong current intensity which enables the stimulation of higher harmonics. This technique has following significant advantages: Minimizing the noise levels caused by different temperatures, minimizing the noise levels caused by different geometries and minimizing the noise levels caused by a variation of the positioning of the test pieces. Due to the use of such higher harmonics an excellent sensitivity can be achieved. Furthermore the test equipment can operate with frequencies up to 128 kHz. This means both a high inspection speed and a high test quality can simultaneously be obtained.Critical automotive components have convex or concave surface geometries. A crack inspection on such shaped geometries requires that an eddy current probe has to be guided by a robot. A flexible eddy current probe consists of an array between 4 and 20 small sensors and it scans areas between 0.5 cm2 and 3cm2. Such a flexible probe fits very well on a shaped geometry. The requirements for a mechanical handling system are therefore less and the inspection costs are reduced. An application with a flexible probe is presented at a gear test system.induction of strong current intensity, minimizing the noise, variation of the positioning of the test pieces, high inspection speed, a high test quality, eddy current probe, gear test system