Stress concentration occurs at the crack tip of a notched sample when loaded. The crack tip region has been recognized of consisting of two regions: the inner (or end) region, which is also called the fracture process zone, and the surrounding outer region where inelastic deformation occurs. The size of these regions is strongly related to the fatigue threshold and the toughness of the material, and has been extensively studied both experimentally and numerically. Here, we study the crack tip fields of highly stretchable elastomers by adopting the concept of essential work of fracture. In the experiments, double deep edge notched tension (DENT) specimens are loaded to rupture, during which the loading curves are recorded. By changing the ligament length, two length scales around the crack tip are identified: one is the size of the fracture process zone, and the other is that of the inelastic zone. Their experimental measurements are comparable with the fractocohesive length and fracto-dissipative length of the materials, respectively. Moreover, we find that the essential work of fracture $w_e$of a highly stretchable elastomer, obtained by extrapolating the specific work of fracture $w_f$ to zero ligament length, resembles the fatigue threshold$T\text{th}$ obtained by a separate fatigue test. Furthermore, we compare the fatigue threshold with those predicted by Lake-Thomas model and Wells model. The present work links the essential work of fracture to the fatigue threshold, and elucidates the physics embedded in the crack tip fields of highly stretchable materials.

加载时，缺口样品的裂纹尖端会出现应力集中。裂纹尖端区域已被认为由两个区域组成：内部（或末端）区域，也称为断裂过程区，以及发生非弹性变形的周围外部区域。这些区域的大小与材料的疲劳阈值和韧性密切相关，并且已经通过实验和数值进行了广泛的研究。在这里，我们通过采用断裂本质功的概念来研究高度可拉伸弹性体的裂纹尖端场。在实验中，双深边缘缺口张力 (DENT) 试样加载至断裂，在此期间记录加载曲线。通过改变韧带长度，裂纹尖端周围的两个长度尺度被识别：一个是断裂过程区的大小，另一个是非弹性区的大小。他们的实验测量值分别与材料的压裂内聚长度和压裂耗散长度相当。此外，我们发现断裂的基本功${瓦}_{\mathrm{电子}}$一种高度可拉伸的弹性体，通过推断特定的断裂功而获得 ${瓦}_F$ 到零韧带长度，类似于疲劳阈值$吨\text{日}$通过单独的疲劳试验获得。此外，我们将疲劳阈值与 Lake-Thomas 模型和 Wells 模型预测的阈值进行了比较。目前的工作将断裂的基本功与疲劳阈值联系起来，并阐明了嵌入在高度可拉伸材料裂纹尖端场中的物理学。