Research On Blade Dynamic Strain Inversion Method Based On Blade Tip Timing And Sparse Reconstruction

The blades of turbofan engines operating under severe conditions are prone to vibration,and the resulting dynamic stress may lead to fatigue failure.It is necessary to accurately obtain the stress distribution of important parts of the blade to monitor its working status.Stress and strain exist together,and the non-contact measurement of blade dynamic strain based on Blade Tip-Timing(BTT)is an advanced technology.However,there is few research on torsional vibration in the BTT field,and it is necessary to establish a high-precision finite element model(FEM)for accurate inversion of dynamic strain.Therefore,the research on blade torsional vibration measurement method and blade FEM updating method is carried out.The main work of the dissertation is as follows:(1)Based on the Timoshenko beam theory and the finite element theory,the vibration characteristics of the blade are analyzed,and the mapping relationship between the blade tip displacement and the blade strain is deduced according to the transfer ratio theory,which provides a theoretical basis for the following research.(2)The characteristics of blade torsional vibration are studied,and the measurement method of blade torsional vibration and the corresponding dynamic strain inversion method are proposed.The test results verify the effectiveness of the proposed methods.(3)In order to obtain a high-precision transfer ratio,a blade FEM updating method based on First-Order optimization is proposed.The test results verify the effectiveness of the method.(4)The vibration signals of the blade are measured through the BTT measurement system and strain gauges on the high-speed rotating blade test bench,and the initial FEM of the blade is updated based on the real natural frequency.The results show that the dynamic strain of high-speed rotating blades can be inverted based on BTT and sparse reconstruction,and the accuracy can be improved after the model is updated.