摘要
通过四点弯曲试样进行不同加载复合比的Ⅰ＋Ⅱ型的断裂试验。考察了硬铝合金ＬＹ１２ＣＺ在不同复合比下的断裂过程及断口的宏微观特征。结果表明，材料在不同的复合比下，其损伤与断裂的机理将发生质的变化。该材料在近Ⅱ型时损伤和破坏不敏感于复合比的变化，其断口微观形貌表明，韧窝体积小且数量少，形状多呈椭球形，属剪切断裂所致。而近Ⅰ型断口的显微分析则显示韧窝体积大且多呈球形，属正断所致。在近Ⅰ型与近Ⅱ型载荷下的断裂的微观机理不同。在应力状态由纯Ⅰ型渐变到纯Ⅱ型的过程中，断裂机理转变的临界点既受应力状态的影响，也取决于材料的结构特征及环境因素。材料的结构特征在此可能起主导作用，在讨论弹塑性复合型断裂判据时不应忽略材料的特征参量。
Mixed mode elastic plastic fracture tests of LY12CZ aluminum alloy were carried out by using four point bend type specimens. K Ⅰ/K Ⅱ ratios were varied from 0(mode Ⅱ) to ∞(mode Ⅰ) by employing a special loading device.The characteristics of fracture processing and SEM fractographic were investigated.The results show that:there are two types of fracture micromechanism.With increasing mode Ⅱ component,cracks due to shear type fracture initiated and extented unsteadablely in direction of 76°.The character of fracture is no sensitive to the ratio of K Ⅰ/K Ⅱ .While under mode Ⅰ and near mode Ⅰ loading,cracks due to dimple type fracture initiated and extendent steadably in crack direction.It is found that the transition of fracture mechanism is depended mainly on the microstructure of material.
出处
《机械强度》
CAS
CSCD
北大核心
1997年第1期62-65,共4页
Journal of Mechanical Strength
基金
国家自然科学基金
关键词
复合型
韧性断裂
断裂机理
mixed mode,ductile fracture,fracture mechanism
