Abstract: The indentation fracture can be used widely in the areas including rock breakage and test of fracture toughness of materials．When an elastic half － plane substrate is subject to indentations by a rigid，flat － ended punch，a singular stress field and K － dominant region should arise adjacent to the punch edges．When the intensification of such singular stress fields reaches its critical value，fracture will take place on the surface of the contact boundary．The cracking of indentation is a new type of fracture problem．By using the energy release rate of boundary translation the fracture of indentation has been formulized and
critical load and critical cracking angle of the indentation have been found in the present paper．

Key words: Fracture mechanics , Contact mechanics , Stress intensity factors , Indentation fracture

摘要： 平面压痕的开裂在材料机械性能的研究、破岩机理的研究中有着广泛的应用。当刚性压头作用在半
平面弹性体的表面时，会产生一个平面压痕，该压痕的两端将出现I 型奇异压应力场，该奇异应力场的应力集中达到一定程度时，即达到临界条件时，该奇异应力场所在的边界将开裂。压痕边界的开裂问题是一个新型的断裂力学问题，通过边界移动的能量释放率的分析定量地给出了平面压痕边界开裂能量释放率数学表征，给出了边界开裂的极限临界载荷和临界开裂角。

关键词: 断裂力学 , 接触力学 , 应力强度因子, 压痕开裂