Micromechanical modeling of grain boundary resistance to cleavage crack propagation in ferritic steels
Micromechanical modeling of grain boundary resistance to cleavage crack propagation in ferritic steels
复制标题
铁素体钢中晶界抗解理裂纹扩展的微观力学模型
DOI：
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
J. Faleskog
中科院分区：
文献类型：
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作者：
M. Stec;J. Faleskog
在铁素体钢中，解理微裂纹的扩展随着晶粒间的扩展而改变其扩展方向。这是由于相邻晶粒的解理面取向不同造成的。为了在新晶粒中达到解理面，微裂纹必须首先穿透晶界。因此，晶界在解理断裂中起天然屏障的作用。本文使用具有轴对称周期性的三维有限元模型，研究了晶界和解理面相关的取向错误对裂纹止裂的影响，该模型代表了两个解理面相对倾斜和扭曲的晶粒。铁素体的温度相关力学性能采用温度相关粘塑性响应模型。本文给出了微裂纹穿透晶界时裂纹前缘的发展过程。在与韧脆转变（DBT）区域相对应的温度范围内，研究了扭错取向对临界晶粒尺寸的影响。临界晶粒尺寸被定义为能够阻止快速扩展的微裂纹的最大晶粒尺寸。结果表明，当倾斜和扭转同时存在时，倾斜和扭转对裂纹扩展阻力的影响是可以解耦的。
In ferritic steels a propagating cleavage microcrack changes its propagation direction as it advances from grain to grain. This is due to differences in the orientation of the cleavage planes of two neighboring grains. In order to reach a cleavage plane in a new grain, a microcrack must first penetrate the grain boundary. Grain boundaries therefore act as natural barriers in cleavage fracture. The influence of a grain boundary and the associated misorientation in cleavage planes on crack arrest is here examined using a 3D finite element model with axisymmetric periodicity, representing two grains whose cleavage planes are tilted and twisted relative to each other. The temperature dependent mechanical properties of ferrite are modeled using a temperature dependent viscoplastic response. The development of the crack front as the microcrack penetrates through a grain boundary is here presented. The influence of the twist misorientation on the critical grain size, defined as the largest grain size that can arrest a rapidly propagating microcrack, is examined in a temperature range corresponding to the ductile to brittle transition (DBT) region. It is shown that when both tilt and twist misorientation are present, the influence of tilt and twist, respectively, on crack growth resistance can be decoupled.