Method for diagnosing defects in solid materials and a diagnostic device

A device for characterizing a solid material by vibration, the solid material being in a rotation symmetry for an angle of rotation around a longitudinal axis of the solid material, preferably in a cylindrical shape, the device comprising:

• a vibration exciting tool configured to cause a vibration of the solid material by providing an excitation force to the solid material substantially in a radial direction, namely in a direction substantially intersecting with the longitudinal axis with a substantially orthogonal angle;
• a pair of transducers configured to be attached to the surface of the solid material and to detect the vibration and output a pair of sensor signals;
• an adder configured to add the pair of sensor signals and to output a summed output of the pair of transducers to constitute an electrical output signal;
• an analyzing unit configured to receive the electrical output signal, process the electrical output signal and to output a frequency spectrum of a characteristic transfer function of the solid material, the analyzing unit further comprising a processor, a memory, and a human interface,
• wherein the pair of transducers are configured to be aligned at opposing positions diametrically symmetric, namely, symmetric for a 180-degree rotation around the longitudinal axis of the solid material, and at an angle between a line connecting the pair of transducers and the direction of the excitation force being orthogonal.