基于应变诱导控制陶瓷预制裂纹的方法及断裂韧性评价

Precracking Method Based on Strain Induced Controlling of Ceramics and Fracture Toughness Evaluation

提出了一种简单通用的陶瓷预制裂纹新技术,在陶瓷样品上预先切出一个斜切口作为裂纹诱导源,将陶瓷与匡字型的金属梁紧密粘结在一起后进行三点弯曲加载,使样品受到下拉上压的弯曲载荷,利用金属变形对陶瓷裂纹扩展的应变约束,调整陶瓷受拉区高度可获得含不同裂纹长度的样品。对典型陶瓷Al2O3、SiC和Si3N4进行了预制裂纹试验,利用声发射技术(AE)监测陶瓷中裂纹的扩展过程,采用单边预裂纹梁法(SEPB)测量其断裂韧性。结果表明:该方法操作简便,预制裂纹成功率达到80%以上,测得的Al2O3、SiC和Si3N4断裂韧性分别为4.45±0.41 MPa·m^1/2、3.45±0.34 MPa·m^1/2和5.23±0.49 MPa·m^1/2。

A simple and feasible precracking method based on the strain government of ceramics to crack propagation was proposed. Three-point bending loading was carried out to prefabricate cracks in Al2O3, SiC and Si3N4 ceramic specimens by bonding the specimens with a triangular notch(crack initiation) on a metal beam to form a ductile-brittle composite beam. The specimens with different crack lengths can be controlled by adjusting the tensile zone height of ceramics. The fracture toughness of these three ceramics was measured by a single edge precracked beam method. The crack propagation process in the ceramic specimens was monitored by acoustic emission technology. The result show that this technology is easy to operate and the success rate of pre-cracking is >80%. The fracture toughness of Al2O3, SiC and Si3N4 measured is 4.45±0.41, 3.45±0.34 MPa·m^1/2 and 5.23±0.49 MPa·m^1/2, respectively.