考慮晶界效應(yīng)的近片層TiAl高溫動(dòng)態(tài)力學(xué)行為的數(shù)值模擬.pdf

1、中國(guó)科學(xué)技術(shù)大學(xué)碩士學(xué)位論文考慮晶界效應(yīng)的近片層TiAl高溫動(dòng)態(tài)力學(xué)行為的數(shù)值模擬姓名：盧山申請(qǐng)學(xué)位級(jí)別：碩士專業(yè)：固體力學(xué)指導(dǎo)教師：李子然2011-05ABSTRACT II ABSTRACT In this paper, a three-dimensional polycrystalline finite element model based on Voronoi arithmetic is built to simulate N

2、ear lamellar TiAl (hereinafter referred to as NL TiAl) containing the grain boundary effect, which further improves the work of NL TiAl numerical simulation. Based on rate-dependent crystal plasticity theory, by adding t

3、he constitutive model of grain boundary with the effect of slip and expansion, the constitutive model of this paper contains the effect of slip, twinning and grain boundary . Using the Voronoi arithmetic, a three-dimens

4、ional NL TiAl polycrystalline finite element model is built with randomly grain group size, shape, spatial orientation distribution, and shell elements is used to describe the grain boundaries at the junction of grain g

5、roups. Besides, the effects of model size and element number to the results of the simulation are investigated. In addition, the model is further improved by dividing each grain group into a number of grains and introduc

6、ing shell elements between grains to better reflect the real microstructure of NL TiAl. These two finite element models are used to simulate the elasto-plastic mechanical behavior of NL TiAl under temperatures of Room te

7、mperature, 500℃, 700℃ and tensile strain rates of 0.001, 320, 800 and1350/s. The conclusions drawn from those two simulations agree well with the experimental results. Besides, the effect of grain boundary on the mechani

8、cal behavior is investigated. The calculated result shows that the stress distribute of the grains has significant change after adding grain boundary shell elements, and certain stress concentration appears near the grai

9、n boundaries. In addition, the calculated also shows that the grain group boundaries obstruct the twinning, leading the volume ratio of deformation twin near the grain group boundaries smaller than the average value of d

10、eformation twin of the whole model. The summary of this paper and the prospect of future work are under presentation in the final part of this paper. Key words: near lamellar TiAl, Voronoi arithmetic, grain boundary, dyn