说明：  abaqus 中开发的哑节点单元，该单元能够模拟裂纹，并能够自动提取求解裂纹所需参数，避免了采用自带单元提取数据容易出现错的现象。简单方便。
(abaqus in the development of the dummy node unit, which can simulate the crack, and the ability to automatically extract the necessary parameters to solve the crack to avoid the use of own unit to extract data prone to error phenomenon. Simple and convenient.)