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Male, born in 1973, Professor, Doctor of engineering, Doctoral supervisor. His research focuses on the digital studies of casting process. His academic research has led to the publication of more than 45 papers. ith the development of the aviation industry, the turbine blade, as the most critical component of the aero-engine, has received more and more attention. At present, most turbine blades are made of superalloy material and produced by the Directional Solidification (DS) technology [1][2][3][4] . In recent years, computer simulation technology has played a more and more important role in the DS process, including the simulation of macroscopic physical fields [5][6][7][8][9][10] and microstructure [11][12][13][14] . In the field of numerical simulation in the DS process, the Finite Difference Method (FDM) [15] and Finite Element Method (FEM) [16] are two of the most common numerical methods. FEM is suitable for unstructured mesh. Hong et al. [17,18] simulated the temperature field in the DS process by ProCAST software (ESI Group, Paris, France), which is based on tetrahedral mesh, but the computation efficiency was low. In order to improve the calculation efficiency, Cui et al. [19,20] Carlo ray tracing approach to calculate radiation heat transfer, but the mesh solution couldn't accurately match with the irregular shuttering by FDM. Considering that the irregular shell boundary and radiation heat transfer need to be handled in numerical simulation of the DS process, an improved Monte Carlo ray tracing approach is used to calculate radiation heat transfer, and a radiation heat transfer model based on FEM is explained. The key technologies, such as distinguishing boundaries automatically, local matrix and lumped heat capacity matrix, are also expounded. Through the work above, a temperaturefield numerical simulative program of DS based on the FEM is developed. By calculating the temperature fields of a superalloy turbine blade in HRS process with different withdrawing rates [21,22] , the effects of different withdrawing rates on the DS process, such as temperature gradient, cooling rate and solidification rate, are analyzed, and the HRS technology is also optimized.

N ear net shape ( N N S ) manu f actu ri ng has show n promi se f or the f u tu re of f ou nd ry i nd u stry , d ecreasi ng machi ni ng allow ance and i ncreasi ng the ef f i ci ency of prod u cti on d ramati cally . T he i mpact of thermal stress during casting solidification on the defects and d ef ormati on i s of g reat concern. E ng i neers and researchers make great efforts to try to precisely control the d ef ormati on of casti ng s [ 1 ] , b u t the d ef ormati on of castings is still a difficult puzzle. Numerical simulation of thermal stress i n casti ng i s an ef f ecti ve approach to pred i ct the d i stri b u ti on of thermal stress and the d ef ormati on of casti ng s, assessi ng the sou nd ness of prod u cts [ 2 ] . B ased on the resu lts of nu meri cal si mu lati on, the process d esi g ner can mod i f y the shape of the ori g i nal casti ng s so as to compensate f or the d ef ormati on d u ri ng soli d i f i cati on w hi le preservi ng the sou nd ness of the casti ng s [ 3 ] .M any stu d i es have b een mad e on the d ef ormati on resu lti ng f rom thermal stress. W ang Y u epi ng [ 4 ] u sed P roC A S T sof tw are to si mu late the casti ng process of tu rb i ne b lad es mad e of N i -b ased su peralloy . H e compared the resu lts of nu meri cal si mu lati on and the measu rements tak en i n the ex peri ments, provi d i ng Abstract: Deformation of casting during the solidification process has puzzled many engineers and scientists for years. In order to attain the goal of near-net forming by casting, numerical simulation is a powerful tool. Traditional methods compute the thermal stress of both the casting and the mold. This method suffers the problem of massive calculation and failure of convergence. This paper proposes an improved Mold Surface Element Method, the main idea of which is to use the surface elements instead of body elements to express the interactions between the casting and the mold. The proposed method shows a high computation efficiency and provides satisfactory precision for engineering. Two practical casting products were used to verify the proposed method. The simulated results agree well with those observed in practical products. The proposed method is believed to benefit production practice and to provide theoretical guidance.Key words: mold surface element method; thermal stress simulation of casting; casting deformation suggestions for process optimization so as to reduce the resi d u al stress and i mprove the g eometri cal preci si on and stab i li ty . B y apply i ng A N S Y S to the thermal stress si mu lati on, C heng J i ang u o, et al. [ 5 ] ob tai ned the distribution of displacement differences in the casting. T hey chang ed the g eometry of the casti ng accord i ng to the ref erence poi nts and achi eved the d esi red shape w i th d ef ormati on su pplements. L i H u i , et al. [ 6 ] u sed ProCAST to simulate the casting process, analyzing the i nf lu ences of pou ri ng temperatu re and mold -shak i ng temperatu re on the resi d u al stress and d ef ormati on of...