Influence Of Foreign Object Damage On Fatigue Limit Of TC4 Blade

During the take-off,landing or low-altitude taxiing phase of the aircraft,its engine inevitably sucks in foreign objects on the runway,such as stones,gravel,and tiny metal parts.These foreign objects are sucked into the engine along with the high-speed airflow,and its blades are likely to be damaged by impact,which is called foreign object damage(FOD).At this time,since the engine blades have been damaged by foreign objects,coupled with their high-speed rotation,high-cycle vibration loads will be generated,which will accelerate the damage of the engine blades.If the blade breaks during the flight of the aircraft,it will cause great hidden dangers to flight safety,and even flight accidents will occur.Therefore,it is extremely important to carry out research on the fatigue limit of aircraft engine blades caused by foreign object damage,and to master the methods that can predict the fatigue limit.The main research contents of this article are as follows:(1)The TC4 material is selected for the foreign object damage test,and the shape of the specimen is designed according to the test needs,and the foreign object damage test is carried out by using a self-designed and manufactured drop weight testing machine.The foreign object damage test under five test conditions was carried out respectively.After the impact test,the macroscopic observation of the notch morphology was carried out,and the difference and difference between the FOD notches caused by different impact forms were studied.(2)Using the VE-5150ST vibration table,the vibration fatigue test was carried out on the smooth specimen and the FOD specimen by the step-by-step method,and the fatigue limit of the blade under each impact test condition was studied.It is found that under the same angle impact,the blade fatigue limit decreases with the increase of the drop weight impact height;under the same drop weight impact height,the blade fatigue limit decreases with the increase of the drop weight impact angle;and the edge impact ratio is higher than the face center The impact on the blade caused more damage.(3)The fatigue limit of FOD blades is predicted by the Neuber-Kuhn expression and Peterson expression under the mean stress model.The results show that the prediction results of these two methods are dangerous,so the factors K_t andρare revised respectively.The results show that when the parameterρis corrected,the two expressions can reduce the error of the predicted value of the 0° edge impact;when the K_t is corrected,the prediction results of the Neuber-Kuhn expression are used for the edge impact specimen with an angle The errors are all below 20%,indicating that the prediction results of this method are relatively reliable.Compared with the traditional prediction method,the results are greatly improved,and it can solve practical engineering problems to a certain extent.In this thesis,the influence of foreign object damage on the blade is studied,and the fatigue limit of the FOD blade is studied by the method of vibration fatigue and its prediction method is revised,which can provide a reference for the tolerance design of the engine compressor blade,which is very important.engineering significance.