Patent ID: 8933693
Filing Date: 2015-01-13
Classification: E21B

Abstract:
1. A device to determine existence and location of parasitic stress forces on a rod portion, the rod portion made of a magnetostrictive material and having a hollow tube, the device comprising: an envelope made of a non-magnetic material, the envelope being laid out in such a way as to be able to penetrate into a portion of the hollow tube of the rod portion and to translate along the portion of the hollow tube, the hollow tube having a first axis, the envelope having an inside; a magnetic field source, disposed inside the envelope, to generate a magnetic field, the magnetic field source having a second axis, the second axis being a magnetization axis; a motor to set the magnetic field source in rotational motion on the inside of the envelope about a third axis roughly parallel to the first axis of the hollow tube; and a sensor to measure a value of the magnetic field and to deliver a signal representative of the value of the magnetic field.