基于定长裂缝试件的脆性材料尺寸效应实验方法

EXPERIMENTAL DESCRIPTION OF SIZE EFFECT FOR BRITTLE MATERIALS USING SPECIMENS WITH FIXED CRACK LENGTH

由于脆性或准脆性材料内各类微缺陷的影响，材料的力学性能，如名义破坏应力， 刚度以及断裂韧性等随试件的大小而改变，具有明显的尺寸效应。通常情况下，描述材料尺寸效应的Ｂａｚａｎｔ尺寸效应律是建立在一系列相似试件的基础上通过实验方法确定的。 本文提出了一种新的用含固定长度裂缝试件测定断裂韧性和有效断裂过程区大小的实验方法和计算公式。与相似试件测定方法相比，实验结果吻合很好。根据本文提出的定长裂缝试件实验方法，在保证与相似试件相同脆性指数范围的前提下，可以用小试件进行测量。

Due to the existence of various micro-defects in brittle or quasi-brittle materials, the mechanical behavior, such as the nominal failure stress, stiffness and fracture toughness etc., varies with the dimension of specimens. This is defined as the size effect of such materials. In general, the Bazant size effect law is established experimentally using a series of similar specimens. In this paper, a new experimental procedure by which the fracture toughness and effective fracture process zone length are measured using the specimens with fixed crack length is proposed, and the associated formulas are also presented. Under the condition that identical brittleness numbers must be ensured for both the proposed and commonly-used similar specimen method, relatively small specimens can be used under laboratory conditions. It is shown that and good agreement is reached in comparison with the results of the commonly-used similar specimen method.