Livne Ariel, Bouchbinder Eran, Fineberg Jay
Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904, Israel.
Phys Rev Lett. 2008 Dec 31;101(26):264301. doi: 10.1103/PhysRevLett.101.264301.
We present high resolution measurements of the displacement and strain fields near the tip of a dynamic (mode I) crack. The experiments are performed on polyacrylamide gels, brittle elastomers whose fracture dynamics mirror those of typical brittle amorphous materials. Over a wide range of propagation velocities (0.2-0.8c(s)), we compare linear elastic fracture mechanics (LEFM) to the measured near-tip fields. We find that, sufficiently near the tip, the measured stress intensity factor appears to be nonunique, the crack tip significantly deviates from its predicted parabolic form, and the strains ahead of the tip are more singular than the r(-1/2) divergence predicted by LEFM. These results show how LEFM breaks down as the crack tip is approached.
我们展示了动态（I型）裂纹尖端附近位移和应变场的高分辨率测量结果。实验在聚丙烯酰胺凝胶上进行，聚丙烯酰胺凝胶是一种脆性弹性体，其断裂动力学反映了典型脆性非晶材料的断裂动力学。在很宽的传播速度范围（0.2 - 0.8c(s)）内，我们将线弹性断裂力学（LEFM）与测量得到的尖端附近场进行了比较。我们发现，在足够靠近尖端的位置，测量得到的应力强度因子似乎不唯一，裂纹尖端显著偏离其预测的抛物线形状，并且尖端前方的应变比LEFM预测的r(-1/2)发散更奇异。这些结果表明了随着接近裂纹尖端，LEFM是如何失效的。
