脆性膨胀环动态拉伸碎裂实验研究

Experimental study for dynamic fragmentation of brittle expansion rings

发展了一种液压冲击脆性膨胀环实验技术,通过可升降的凸台对脆性膨胀环进行精确的对心定位安置,避免偏心膨胀带来的弯曲断裂,通过膨胀环试件上的半导体应变片测量其在拉伸碎裂过程中的应变时程曲线;对典型脆性材料碳化硅(SiC)陶瓷进行了膨胀拉伸碎裂实验研究,获得了其动态拉伸断裂强度和碎片平均尺寸及分布。实验结果表明:(1)液压冲击膨胀环实验能较好地实现脆性膨胀环的拉伸碎裂,在应变率101 s^−1量级下,SiC陶瓷拉伸断裂应变为3.7×10^−4~7.4×10^−4,平均拉伸断裂应力为206 MPa;(2)SiC陶瓷无量纲化平均碎片尺寸落于多种脆性碎裂预测模型的合理区间内,随着加载应变率的提高,SiC陶瓷的平均碎片尺寸减小;(3)SiC陶瓷拉伸碎裂的碎片分布基本符合Rayleigh分布,但是在细小尺寸上和大尺寸碎片分布上存在一定偏差。

A liquid-driving brittle expansion ring test technique has been developed.The precise centering of the brittle ring was realized by means of a liftable convex platform to avoid the bending fracture caused by eccentric expansion.The strain vs time curves in the process of tensile fracture were measured by the semiconductor strain gauges on the expansion ring.Then expansion tensile fracture experiments of silicon carbide(SiC)ceramics were carried out,and their dynamic tensile fracture strength and average size and distribution of fragments were obtained.The experimental results show as follows.(1)The liquid-driving expansion ring experiment can better achieve the tensile fracture of the ceramic material.At a strain rate of 101 s^−1,the tensile fracture strain of SiC ceramic is 3.7×10^−4−7.4×10^−4,and the average tensile fracture stress is 206 MPa.(2)The dimensionless average fragment size of SiC ceramic falls within the reasonable interval of various brittle fracture prediction models.With the increase of loading strain rate,the average fragment size of SiC ceramic decreases.(3)The fragment distribution of SiC ceramic tensile fracture basically conforms to the Rayleigh distribution,but there are some deviations in the fine size and large size fragment distribution.