摘要
单边切口梁(SENB)法是测试脆性材料断裂韧性 K_(?)的最通用而简便的一种方法,但它在理论上还不够完善。本文分析了试样尺寸对 K_(lc)测试值的影响,导出了不同尺寸比例试件的 K_(lc)之间的关系式。并发现对应于临界尺寸下 K_(lc)测试值是最大值,约为真实值的1.2倍。对氧化铝和氮化硅两种工程陶瓷进行了尺寸效应的试验,得到的结果与理论分析完全一致。
Single-Edge-Notched-Beam(SENB)method is rather popular and simplefor measuring the fracture toughness of ceramic materials,but it is not perfect enough intheory.Experiments show that the toughness value measured by SENB method is relatednot only to the size of specimen and experimental condition but also to the calculating for-mula.In this paper,tbe formula was discussed and revised,the mean fracture stress in therupture origin zone was put forward to replace traditional fracture strength.It was pointedout that the specimen with different size must coincide in shape.The size effect of K_(lc)hasbeen studied and theoretical relation between K_(lc) value and size of specimen has been de-rived.The fracture tonghness of several sets of shecimen with different size wasmeasured,including Al2_O_3and hot-pressed Si_3N_4ceramic materials.The experimental resultswere utterly identical with theoreitical curve.Theoretically,the fracture toughness,K_(lc),is amaterial constant in any case,but the K_(lc)measured by specific method is under the influenceof the shape and size of sprcimen.Experimental and theoreitical analysis indicate that thereexists a critical size on which K_(lc)measured as maximum.
关键词
尺寸效应
断裂
韧性
陶瓷材料
测试
size effect
rupture origin zone
fracture toughness
