Experimental Study Of Titanium Fatigue Monitoring Based On Weak Magnetic Methods

Titanium alloys has been widely used in many fields for its’ excellent performance, such as aviation, aerospace, shipbuilding, chemical industry, metallurgy,automobiles, medical equipment and others. During the service process, Titanium alloy is easily to cause fatigue fracture due to its’ fatigue characteristics. Recently,plane crash accident happened too often that the fatigue attracts people’s attention again. Therefore, it is of great importance to study an effective method to monitor the fatigue process of titanium alloys.The study is aimed to put forward a new method based on the technology of weak magnetic, to monitor the fatigue of titanium alloy component in real-time.Firstly, the fatigue process and fatigue properties of titanium alloy were introduced,the inherent physical mechanism of the titanium’s paramagnetic was also introduced briefly. Then, based on geomagnetic field and the principle of weak magnetic detecting technology, a new model of stress-magnetism was proposed to monitoring the fatigue of the titanium alloy components. Under dynamic stresses, the unit cell of materials will deform, while magnetic line of force traverse through the cell will change. According to the change of magnetic signal captured by transducers of high sensitivity and accuracy, the aim of fatigue monitoring and predictions of fatigue life can be achieved. Subsequently, the material selection and process of the fatigue sample were introduced, and a brief explanation of the composition of weak magnetic monitoring system and operation process was also presented. After selecting fatigue test parameters, the fatigue test of titanium alloy was experimented. It is resulted that the signal captured by the weak magnetic monitoring system was in accordance with the fatigue process, the feasibility of weak magnetic technology using in fatigue monitoring was proved.After the fatigue fracture of the titanium alloy sample, the lattice constant,magnetic susceptibility and the distribution of element were also measured by doing other experiments. It is found that the lattice constant c/a decreased after fatigue, the magnetic susceptibility decreasing and the testing magnetic signal was increased. The result is in coincide with the theory of weak magnetic testing, that the signal of paramagnetic material will increase when the magnetic susceptibilitydecreased.The validity of the weak magnetic monitoring method was proved.