| As the key component of aero-engine with high thrust-to-weight ratio,the production and manufacture of complex hollow turbine blades is a major technical problem.Affected by many factors such as its own complex structure and materials,the qualified rate of single crystal hollow turbine blades manufactured in China is relatively low.Hollow turbine blades are currently manufactured by precision casting technology.The shrinkage strain stemming from metal cooling and solidification during the precision casting provokes the dimension error of turbine blades,in that it is necessary to calculate the shrinkage of casting for die compensation.In traditional industry,dies are trail-produced with high cost and low efficiency,which demonstrates the significance of the study on the shrinkage mechanism related to structures as well as the deformation law and applying it in the mold design during precision casting.In this paper,a basic study on the shrinkage distribution of typical structures of hollow turbine blades and the optimization method of mold cavities is carried out to address the above problems.Numerical simulations and experimental verification were carried out to reveal the structure-related deformation mechanism during the investment casting of hollow turbine blades.The research results have theoretical guiding significance and engineering value for realizing high-performance precise solidification forming of hollow turbine blades.The main contents of this study are as follows:1.The factors affecting the dimensional accuracy of the casting during the investment casting process of turbine blades are analyzed,and the relationship between stress strain and deformation during the investment casting process is analyzed,and the calculation methods of the shrinkage rate of different turbine blades are discussed.2.The problem which the complex structure of hollow turbine blades lacks effective decomposition and identification means is discussed,according to the typical structural characteristics of hollow turbine blades,four simplified structures including resistance and non-resistance structures with structural mutations are established,and two different pouring process schemes and corresponding pouring systems were designed for investment casting and differential pressure casting.Numerical simulation of the designed structure is carried out,and the influence of different casting methods on casting deformation is analyzed.3.Based on the established simplified structure of the hollow turbine blade,the differential pressure casting process is used to carry out the hollow thin-wall structure precision casting experiment,the displacement field measurement and the calculation and analysis of the obtained casting are carried out,and the obtained results are compared with the numerical simulation to verify the simulation results.4.Several main factors affecting the shrinkage distribution of castings are analyzed,such as wall thickness,outer diameter,and resistance or non-resistance structure.Based on the BP neural network,a mapping model between the wall thickness,outer diameter,node coordinates and section height and the shrinkage rate is established,and the prediction effect of the mapping model is verified.5.The optimization method of the die cavity is discussed,and the method of numerical simulation is used to verify the iterative compensation of the deformation model. |
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