Abstract The identification and quantification of toughening mechanisms in materials is a difficult task which is often made more difficult by the presence of several mechanisms operating at different scales. The hypothesis behind the present work was that the length scales at which these mechanisms operate might be deduced by analysing data from fracture tests conducted on samples containing notches of different root radii. A two stage approach was adopted. Firstly, theoretical models were created using imaginary model materials with well-known toughening mechanisms. In those models having toughening mechanisms on two different scales (known as Dual materials) it was found that the larger-scale mechanism controlled the measured fracture toughness (Kcm) for cracks and sharp notches, whilst the smaller-scale mechanism controlled the behaviour of blunter notches. This change in control created a distinct “kink” in the curve of Kcm as a function of notch root radius. Secondly, experimental data from the literature were examined. Similar kinks were found to be present in the results for some materials, implying Dual behaviour. A method of prediction known as the Theory of Critical Distances (TCD) was applied to the data to estimate the relevant length scales, which in some cases coincided with those of well-known toughening mechanisms. This type of analysis may prove useful for identifying the scale, and relative importance, of toughening mechanisms in a wide variety of materials. It also provides a more accurate way to use the TCD approach to predict the effect of cracks and notches when more than one toughening mechanism is present.

中文翻译：

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缺口试样的断裂数据分析可以提供有关多尺度增韧机制的信息

摘要 材料中增韧机制的识别和量化是一项艰巨的任务，由于存在多种在不同尺度上运行的机制，因此通常会变得更加困难。目前工作背后的假设是，这些机制运作的长度尺度可以通过分析对包含不同根半径的缺口的样品进行的断裂试验数据来推断。采用了两阶段方法。首先，使用具有众所周知的增韧机制的假想模型材料创建理论模型。在那些具有两种不同尺度（称为双材料）增韧机制的模型中，发现更大规模的机制控制了裂纹和尖锐缺口的测量断裂韧性 (Kcm)，而较小规模的机制控制了钝口的行为。这种控制变化在 Kcm 曲线中产生了一个明显的“扭结”，作为凹口根部半径的函数。其次，研究了文献中的实验数据。在某些材料的结果中发现了类似的扭结，这意味着双重行为。将一种称为临界距离理论 (TCD) 的预测方法应用于数据以估计相关的长度尺度，在某些情况下，这与众所周知的增韧机制的长度尺度一致。这种类型的分析可能有助于确定各种材料中增韧机制的规模和相对重要性。