Nondestructive Evaluation of BSCC Artificial Heart Valves

The subject of investigation is a set of four artificial heart valves made of electrically conductive material, namely the alloy Ti-6Al-4V. Notches of defined geometry with gradually increasing depth were formed on these BSCC (Bjork-Shiley Convexo-Concave) valves. These defects are created on the so-called output strut, which serves as a support mechanism for the controlled movement of the so-called occluder disc and they have been investigated. The method which was used is ultrasonic infrared thermography, where the object was excited by the UTVIS EDEVIS ultrasonic system and the response was detected by the FLIR SC 7200 infrared camera. The postulate for the use of this method is that the excitation signal may be periodically pulsate or in any other way modulated by certain amplitude frequencies, called "lock-in frequency". Lock-in thermography is a type of active lock-in method. The results of damage detection on these relatively complicated objects are compared and discussed.