Research On The Influence Of Ultrasonic Rolling On The Bending Of Thin Wall Parts And Process Improvement

Most structures of aviation engines are composed of thin-walled components.Due to their frequent operation in harsh environments of high temperature and pressure,it is necessary to strengthen thin-walled components to increase the service life of aviation engines.Ultrasonic rolling surface strengthening can significantly improve the fatigue performance of materials.However,ultrasonic rolling can easily cause bending deformation of thin-walled parts after processing,thereby affecting their performance and leading to component failure.To study the deformation causes of thin-walled parts after ultrasonic rolling strengthening and reduce the deformation of thin-walled parts after strengthening through process improvement.The main research work is as follows:1.The existing ultrasonic rolling equipment has been improved to better meet the surface strengthening needs of thin-walled parts.The structure of the ultrasonic rolling tool head has been improved,reducing the contact radius of the tool head to ensure that it can achieve excellent surface modification results even under light load processing;Analyzed and determined that machining with relatively small amplitude relative to static pressure can maintain stable and controllable machining state.Under the constraint of tool head size,Abaqus and Matlab were used to jointly optimize the size of the amplitude transformer to achieve uniform and stable output;The overall structure of the ultrasonic rolling equipment has been optimized and the weight of the equipment has been reduced,thereby improving the flexibility of the processing equipment;A in-place installation method has been designed for machining the cutting head,so that the cutting head can be maintained in the same posture every time it is installed through the thread,improving installation efficiency.2.Through a single factor experiment of ultrasonic rolling machining on TA19 titanium alloy,the influence of different factors on surface integrity was analyzed;And based on the parameter selection method of rank sum ratio,the optimal processing parameters were selected by comprehensively considering the surface integrity processed by different parameter combinations,providing parameter selection for subsequent experiments.3.Proposed and validated the bending deformation theory and simulation model of ultrasonic rolling strengthening thin-walled parts.The relationship between residual stress field and bending deformation of thin-walled parts was derived based on elastic deformation theory and bending theory;Analyzed the deformation degree and trend of thin-walled parts under different static pressures,ultrasonic amplitudes,processing efficiency,roller head radius,and sheet thickness;Using the same processing parameters as the actual experiment,the residual stress field was simulated using a finite element model.In the simulation,the residual stress field was applied to a large area of the flat thin-walled specimen in the depth direction,and the bending process of the thin-walled specimen with the same trend as the actual change was obtained;In the model validation stage,the bending degree of thin-walled parts was calculated based on the measured residual stress field,and the theoretical value obtained had a small error compared to the actual value;Compare the simulated bending degree with the actual value,and the simulated value has a proportional change rate with a small error compared to the actual value.Proved the accuracy of the simulation model and the actual model.4.Based on the causes of bending deformation of thin-walled parts,the residual stress introduction and bending degree of thin-walled parts under different processing strategies were analyzed through simulation and actual experiments.Analyzed the influence of the machining methods of cantilever clamping and simply supported clamping on the bending degree of thin-walled parts;The bending degree of thin-walled parts after bilateral asynchronous machining and bilateral synchronous machining was compared,and the life verification of these two processes was carried out on fatigue test pieces.The results indicate that the bilateral synchronous strengthening method has more advantages in controlling the deformation degree and improving the fatigue life of thin-walled parts.