钢解理断裂应力的测量和物理意义

ON THE MEASUREMENT AND PHYSICAL MEANING OF THE CLEAVAGE FRACTURE STRESS IN STEEL

用二维平面应变有限元计算了不同尺寸四点弯曲 ( 4PB)缺口试样缺口前的应力分布。通过测量解理起裂源的位置 ,精确测定了一种钢的细观解理断裂应力σf 和宏观解理断裂应力σF。结果表明 ,σF 的测量比σf 更简单和方便 ,σf 的值可以用σF 估计。随试样尺寸的增加 ,σF和σf 的值基本不变 ,σF 的分散性小于σf。稳定的σF 和σf 的下限值可以用比Griffith Owen试样尺寸大的试样测得。σf 可精确用于细观解理断裂机理的分析 ,并表征了钢的本质韧性。建议σF作为一个潜在的工程参数 ,用于钢的解理断裂韧性评价和结构安全设计。

The two dimensional plain strain finite element models are used to analyze the stress distributions ahead of notches of four point bending(4PB) specimens with various sizes of a steel. By measuring the location of the cleavage initiation sites, the local cleavage fracture stress σ f and the macroscopic cleavage stress σ F are accurately measured. The results show that the measurement of σ F is more simple and convenient than that of σ f , and the σ f values could be predicted by the σ F .With increasing specimen sizes, the σ F and σ f remain nearly constant, and the scatter of σ F is lower than that of σ f . The stable lower boundary σ F and σ f values could be obtained by using notched specimens with sizes larger than the Griffith Owen specimen. The σ f could be accurately used for the analysis of fracture micromechanism, and it characterizes intrinsic toughness of steel. The σ F is suggested to be a potential engineering parameter which could be used to assess cleavage fracture toughness of steel and safety of structure design.