Longitudinal, Inclined and Transversal Crack Detection of Bars and Billets with Magnetic Cross Coil Application Method

Magnetic Particle Testing is one of the most used techniques for the detection of surface cracks. Often it is necessary to detect defects in longitudinal as well as transversal directions in very large objects. This might be achieved by using the current flow or yoke magnetizations. By rotation of the work piece and appropriate manipulation cracks with different directions can be identified. The disadvantages of these magnetization methods are: Burning in by non-uniform contact, necessity of several magnetization currents, manifold manipulations of the component under investigation, high investment costs. In order to avoid these disadvantages, we designed the system described in the following. The magnetic particle inspection system consists of a cross coil with a magnetic field phase shift of 90° relative to each other. With this arrangement magnetic fields allow the detection of transversal as well as longitudinal and inclined surface cracks. Objects of very large dimensions can be tested for surface defects in transversal and longitudinal directions during one operation. Various realizations of this system with cross coils in operation are discussed and compared with other magnetizing methods.