Research On Damage Identification Method Of Hydraulic Radial Gate Based On Strain Modal Parameters

Hydraulic gate plays an important role in hydraulic machinery and equipment,and its damage in service will directly affect the operation safety of hydropower facilities,people’s life and property safety.Therefore,it is of great practical significance to identify the damage of the gate.In this thesis,the hydraulic radial gate is taken as the research object,and the damage identification of the hydraulic radial gate arm is studied based on the strain modal parameters in view of the common arm damage problems in the failure of the gate.The feasibility of using strain mode in the damage identification of the hydraulic radial gate arm is verified through simulation analysis and engineering tests.The main research work is as follows:1.The finite element simulation model of the radial gate is established by the finite element software,and strain modal analysis is carried out on the gate without damage of the gate arms,which serves as the basis for subsequent simulation damage identification.At the same time,the modal information obtained when the gate is not damaged is imported into the program of the effective independent-drive point residual method.According to the calculation results,the sensor of the radial gate arm monitoring point is optimized to ensure that the sensor of the gate monitoring point can obtain relatively complete modal information,which is ready for the subsequent simulation and test.2.The damage of the gate arm is simulated in the simulation,and the modal analysis of the gate is carried out.The natural frequency,displacement mode,strain mode and strain mode difference obtained are used for damage identification.The results show that when structural damage occurs,the natural frequency decreases gradually with the deepening of the damage degree,and the damage can be determined,but it is difficult to locate the damage.The displacement mode is also difficult to identify the damage position of the gate arm.The strain mode and strain mode difference can better identify the damage location,and the strain mode difference can reflect the damage situation more clearly,and the sensitivity of the first three strain mode differences to the damage point is different.The first order strain modal difference can identify the damage on the gate wing and web,the second order strain modal difference is sensitive only to the damage on the wing,and the third order strain modal difference is sensitive only to the damage on the web.The overall damage of the gate arm can be judged by combining the first three steps.3.In the hydraulic experimental platform,the single-point damage and two-point damage of the gate arm were prefabricated by the method of additional mass,the structural strain was measured by strain gauge,the modal parameters of the gate strain were identified by the enhanced frequency-domain decomposition method,and the natural frequencies obtained from the gate simulation and the experiment were compared to verify the feasibility of the simulation modeling.At the same time,the strain modal difference obtained from the test is used to identify the damage of the radial gate arm.The experimental results show that the first order strain modal difference can completely identify the damage of the gate arm flap and web,the second and third order strain modal difference can identify the damage of the gate arm flap and web,respectively.The damage of gate arm can be judged by integrating the first three steps.The consistency of simulation and test results verifies the feasibility and effectiveness of strain modal difference in damage identification of gate arm,which lays a foundation for the establishment of damage prediction and monitoring digital twin system of hydraulic radial gate.