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为研究核级石墨(IG11)的断裂力学性能,对单边切口的石墨梁进行三点弯曲断裂试验,采用电子散斑干涉(ESPI)技术测量梁试件表面的场位移.试验结果表明,石墨的起裂荷载为680～838 N,峰值荷载为845～974 N;峰值荷载处,裂纹口张开位移为0.088～0.091 mm,裂纹尖端张开位移为0.016～0.018 mm,裂缝长度约为25 mm;参照混凝土双K模型及线弹性断裂力学,确定石墨的起裂断裂韧度为0.96～1.19MPa·m1/2,失稳断裂韧度为1.61～1.85 MPa·m1/2,弹性模量为10.22 GPa.不同加载步的包裹相位图表明,石墨断裂过程区接近正方形,在峰值荷载之前,边长不超过3mm;峰值荷载之后,边长在5～8 mm范围内变化.“,”Three-point bending tests were performed on the single-edge notched beams made of IG 11 graphite to investigate the fracture properties of nuclear graphite.Electronic speckle pattern interferometry (ESPI) technique was used to measure the displacement fields of the graphite beams.Experimental results indicated that the initiation fracture load of graphite beams was 680～838 N and peak load was 845～974 N.At the peak,crack mouth opening displacement was 0.088～0.091 mm,crack tip opening displacement was 0.016～0.018 mm and the crack length was about 25 mm.Furthermore,the initiation fracture toughness and unstable fracture toughness according to the double-K fracture model of concrete were determined as 0.96～1.19 MPa·m1/2 and 1.61～1.85 MPa·m1/2 respectively.Elastic modulus was evaluated as 10.22 GPa according to linear elastic fracture mechanics.By analyzing the phase maps at different loading stages,fracture process zone of graphite was identified as square.At the pre-peak stage,the length of the FPZ did not exceed 3 mm;and at the post-peak stage,the length of the FPZ was within 5-8 mm.