Abstract: The present invention relates to methods for determining the existence and location of parasitic stress-inducing forces on a substantially cylindrical rod portion defined along a first axis and when this rod is made of a magnetostrictive material. The method according to the invention is essentially characterized in that it consists in magnetizing the wall of the rod portion in a pseudo-helix 10 centered on the first axis, in applying a forced stress between the two ends of the rod portion, in measuring, along the rod portion, the magnitude of the magnetic field created by the rod portion after it has been subjected to the forced stress, these measurements being taken in a direction substantially parallel to the first axis, and from these measurements, in deducing the existence and location of the parasitic stress-inducing forces on the rod portion. The invention also relates to a device for implementing this method.

Abstract: The invention concerns the methods for determining, relative to a point Po, the location of a fixing point Pf of a rod T located in an environment Mi wherein prevails a permanent magnetic field Ch. The inventive method is characterized in that it consists in studying the variations of the magnetic flux which passes through the windows F when the rod is and is not subjected to a torque about its axis A, said windows having substantially the same area and being connected to the rod T respectively in different points Px, Px+1, . . . located on the portion of the rod delimited by the assumed site of the fixing point Pf, and including the point Po, and having each a given position relative to the magnetic field lines of force when the rod is not subjected to the torque. The invention also concerns a device for implementing said method. The invention is advantageously applicable to determining the location of the sticking point of a string of hollow drill rods in an oil well.

Abstract: The invention concerns a probe for analysis of a collection of rods or tubes comprising an elongated casing which bears, at a first end, at least one first magnetometer and, at a position sufficiently remote from the magnetometer, a permanent magnet, the north-south axis of which is perpendicular to the axis of the rods.