跨高比对混凝土双K断裂参数的影响(英文)

The Influence of Span/Depth Ratio on the Double-K Fracture Parameters of Concrete

实验中经常采用标准三点弯曲梁测试材料的双K断裂参数 :起裂韧度KiniIc和失稳断裂韧度KunIc 而在实际工程中 ,跨高比并不总是等于 4 ,为得到材料实际且准确的断裂韧度 ,有必要研究跨高比对双K断裂参数的影响 文章通过数值模拟三点弯曲梁试件 (跨高比范围 3～ 8)来探究双K断裂参数随跨高比的的变化趋势 同时 ,数值实验模拟了材料强度及试件高度双K断裂参数的影响 结果表明 ,失稳断裂韧度KunIc 与跨高比无关 ,是材料内在性能 ,对混凝土材料而言 ,可以作为预测材料不稳定扩展的一个准则 ;而起裂韧度KiniIc 不仅随着材料的强度变化 ,就试件的高度和跨高比而言 ,也呈现出一定的尺寸效应 。

Standard three point bending beams are often used in labs to measure the double K fracture toughness: the initiation fracture toughness K ini Ic and the unstable fracture toughness K un Ic In practice, however, the span/depth ratio covers a large range, not always equals to 4. So the study of influence of span/depth ratio on double K fracture parameters is becoming necessary for evaluating the true fracture toughness of material. In this paper, numerical experiments, with span/depth ratio ranging from 3 to 8, are simulated on specimens of general three point bending concrete beams , with a main view to make clear whether the double K fracture parameters vary along with the change in the span/depth ratio. At the same time, the effects of the depth and the strength upon double K fracture parameters are investigated by means of numerical experiments. The experimental evidence shows that the unstable fracture parameter K un Ic is independent of span/depth ratio and only property dependent of material, and it can be treated as a criterion to predict the crack unstable propagation for concrete. While the initiation fracture toughness K ini Ic not only varies with the strength of material, but also presents size effects in terms of span/depth ratio and the depth of specimens, which require a further theoretical investigation.