韧脆转变的一种细观随机模糊统计分析

对不同温度和应力状态下40Cr材料进行大子样宏观试验和细观观测,提出了一种新的材料断裂韧脆转变统计随机模糊模型。该模型认为,在统计意义上,材料的韧性断裂为空穴机制,临界空穴扩张比参数可以作为韧性断裂的判据;材料的脆性断裂可以用内嵌币状裂纹的脆性断裂模型来模拟,为此测量断裂特征长度,提出并具体计算了控制币状裂纹失稳扩张的细观临界应力强度因子;在韧脆转变区域内,这两种机理并存并相互竞争,为此提出了模糊准则。对模型参数进行了测量和统计分析,给出分布规律,给出了计算断裂特征的概率模型。计算了韧脆转变区域内的细观机制变化和宏观响应。结果表明,该模型及分析方法可以很好地模拟应力状态及温度对韧脆转变的影响。

Random-Fuzzy Model for the Ductile/Brittle Transition

A large sample of experiments was carried out to study influence of stress triaxiality and temperature on the growth of micro voids and the ductile/brittle transition(DBT)behavior of 40Cr steel.A random-fuzzy model was put forward for the transition.It is assumed that the ductile fracture is controlled by the micro void mechanism,and the critical void growth ratio can be used as the criterion of ductile fracture.The brittle fracture is modeled by an embedded penny crack.A micro stress intensity and the fracture characteristic length of the brittle fracture was then presented and calculated. The DBT is completed by the two mechanisms,which exists in the fracture of all specimens simultaneously.The distributions of model parameters were measured experimentally.A random model and a random-fuzzy model for DBT were presented.The comparison between the calculated and experimental results shows that the random-fuzzy model can model the DBT satisfactorily.