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为了检验2024-T351和7005-T6351等两种中强度铝合金J_(1c)的几何相关性,进行了三支点弯曲试验。用氧化着色法显示出载荷一挠度曲线上选定部位处的裂纹增长量。为了便于确定初始裂纹扩展时的J_(1c)值,建立了J-裂纹增长量的阻力曲线。确定了7.6厘米厚的7005铝合金厚板的断裂韧性在全厚度范围内的变化,并使其与断口金相和金相观察建立关系。本文还把从7005铝合金小试样测得的现今风行的J_(1c)值与以前用全厚度线弹性试样测得的特征参数K_(1c)作了比较。
In order to test the geometric dependence of J_ (1c), two medium strength alloys, 2024-T351 and 7005-T6351, three-point bending test was carried out. Oxidation staining shows the amount of crack growth at a selected location on the load-deflection curve. In order to determine the value of J_ (1c) at initial crack growth, a resistance curve of J-crack growth was established. The change of the fracture toughness of the 7.6 cm thick 7005 aluminum alloy plate in the whole thickness range was confirmed and the relationship was established with the fracture metallography and the metallographic observation. In this paper, the current prevailing value of J_ (1c) measured from a small sample of 7005 aluminum alloy is also compared with the characteristic parameter K_ (1c) previously measured with a full thickness linear elastic specimen.