基于VB-SCSC岩石试样的动态断裂韧度测试方法研究

A method measuring dynamic fracture toughness of rock using VB-SCSC specimens

为了对扩展裂纹进行止裂,对SCSC构型试件进行改进,提出V型边界侧开单裂纹半孔板(V-shape boundary single cleavage semi circle specimen,VB-SCSC)构型试件,该试件具有V型的底部边界,在冲击载荷下产生倾斜向上的压缩波,该压缩波的水平分量对扩展裂纹具有压缩作用,进而对扩展裂纹进行止裂。实验采用中低速落锤冲击实验装置进行,利用裂纹扩展计(crack propagation gauge,CPG)测试裂纹的起裂及扩展时间,同时测试裂纹的扩展速度。采用3种V型底部的夹角,即120°,150°及180°(平的底部),进行实验研究,发现前2种试件均具有止裂功能,并用有限差分软件AUTODYN进行了模拟计算,其结果与实验结果基本一致。利用有限元软件ABAQUS计算裂纹的动态应力强度因子,并通过普适函数进行修正,最后通过裂纹起裂时间及扩展时间确定裂纹的动态断裂韧度。结果表明120°VB-SCSC构型试件具有较好的止裂功能,适合于裂纹动态扩展行为研究及动态断裂韧度的测试;动态扩展韧度与裂纹的扩展速度成反比。

In order to arrest the extending cracks,the specimen with SCSC configuration has been improved,and a new type of specimen with VB-SCSC configuration having a V-shaped boundary was thus proposed in this paper.Under the impacting loads,the compressive stress waves propagate towards the crack tips,and the compressive stress waves restrain the propagating of cracks.The experiments were performed by using the impact load of low medium speed and the crack propagation time and propagation speed were measured with the propagation gauges（CPGs）.The VB-SCSC specimens with three angles of V-shaped bottoms 120°,150° and 180°（straight bottom） were tested,and the former two specimens have the arrest function on the propagating cracks.The finite difference code AUTODYN was applied in the simulation of crack propagation behavior,and the results agree well with the test results.The finite element code ABAQUS was applied in the calculation of stress intensity factors,and Freund？s function was applied in the correction of stress intensity factors.Finally,the dynamic fracture toughness was determined by using the crack initiation time and propagation time.The results show that the 120 ° VB-SCSC specimens arrest the propagating cracks well and are recommended for the future experimental study.The dynamic fracture toughness is inversely proportional to the crack propagation speed.