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提出测试I型断裂韧度的一类新型试样,包括边裂纹平台圆环、边裂纹平台半圆环、边裂纹平台半圆盘,以及它们没有平台的情况,一共6种构型。采用有限元方法标定这一类边裂纹平台(半)圆环(盘)的量纲一化的应力强度因子,分析其变化规律,并给出相应的曲线拟合公式。结果显示,边裂纹(平台)圆环试样量纲一化的应力强度因子–裂纹长度曲线具有先升后降的特殊性质,这使得它们的测试临界点容易从对应的载荷–位移曲线判断和确定,可以方便地测试材料的断裂韧度。边裂纹平台半圆盘也有类似的性质,但试样宜选取较大的平台角,而边裂纹半圆盘和边裂纹(平台)半圆环却没有这种性质。此外,经过初步试验,用边裂纹平台半圆盘和边裂纹平台半圆环试样测得砂岩的断裂韧度,与用国际岩石力学学会建议试样所测结果吻合。
A new type of specimen for testing type I fracture toughness is presented, including the edge cracked platform ring, the edge cracked platform semi-circular ring and the edge cracked plateau semi-circular plate, and their absence of platforms. There are totally 6 configurations. The finite element method is used to calibrate the dimensional stress intensity factor of the semi-circular ring (plate) of this type of cracked platform. The variation regularity is analyzed and the corresponding curve fitting formula is given. The results show that the stress intensity factor - crack length curve with the first sample of the ring specimen with edge crack (platform) has the special property of increasing first and then decreasing, which makes their test critical point easy to judge from the corresponding load-displacement curve OK, you can easily test the fracture toughness of the material. The semi-circular plate on the cracked plate also has similar properties, but the sample should have a larger plateau angle, while the semicircular ring on the semi-circular plate and the edge crack (plateau) do not have this property. In addition, the initial test shows that the fracture toughness of the sandstone measured by the semi-circular plate of the edge-cracked platform semi-circular disk and the edge-cracked platform coincides with the measured results of the proposed sample by the International Society for Rock Mechanics.