Grain size effect of thickness/average grain size on mechanical behaviour, fracture mechanism and constitutive model for phosphor bronze foil
Grain size effect of thickness/average grain size on mechanical behaviour, fracture mechanism and constitutive model for phosphor bronze foil
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DOI：
10.1007/s00170-015-6928-2
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发表时间：
2015-08-01
影响因子：
3.4
通讯作者：
Liu, Xianghua
中科院分区：
文献类型：
--
作者：
Fang, Zhi;Jiang, Zhengyi;Liu, Xianghua
尺寸效应在微成形过程中起着重要的作用，任何尺寸的变化都会对材料的力学性能产生很大的影响。本文以晶粒尺寸效应的形式，即材料厚度（T）与平均晶粒尺寸（D）之比，通过微拉伸试验，研究了荧光箔变形行为和断裂的尺寸效应。该比值分别设计为接近但大于、小于和等于1。结果表明，随着T/D比的减小，塑性变形量减小，表明晶粒尺寸对塑性变形起着重要作用，且随T/D比的变化，晶粒变形方式不同。结果表明，当T/D > 1时，材料倾向于韧性断裂，而当T/D <1时，材料倾向于脆性断裂。因此，T/D比值接近1时可以作为韧性断裂和脆性断裂的分界点。当T/D < 1时，在经典复合材料模型的基础上提出了一种新的本构模型。将模型计算结果与实验结果进行了比较，验证了模型的有效性。
Size effects play a significant role in microforming process, and any dimensional change can have a great impact on materials' mechanical properties. In this paper, the size effects on deformation behaviour and fracture of phosphor foil were investigated in the form of grain size effect: the ratio of materials' thickness (T) to average grain size (D) by micro tensile tests. The ratio was designed to be closed to but larger than, less than and equal to 1, respectively. The results show that the amount of plastic deformation decreases with the decrease of the ratio of T/D, which indicates that the grain size plays a significant role and grain deformation modes differ when the ratio changes. It is also found that their fractograph reflects different features in terms of micro-dimples and cleavage planes, further demonstrating that when T/D > 1, its materials have a tendency to fracture ductilely, while materials would like to conduct brittle fracture when T/D < 1. So the ratio of T/D which is close to 1 can be regarded as the divide of ductile fracture and brittle fracture. For T/D < 1, a new constitutive model is proposed based on the classic composite model. The model's results are compared with the experimental ones and the efficiency of the developed models is verified.