脆性的定量化和冲击模量

QUANTIZATION OF BRITTLENESS AND IMPACT MODULUS

定义脆性材料的冲击阻力为抵抗瞬态破坏的能力，它主要依赖于材料的极限应变和裂纹扩展速率．冲击阻力的倒数为脆性．提出了相对脆性的计算方法．并定义材料的抗冲击性能为强度与脆性之比，称为冲击模量．测试计算了１１种材料的相对脆性和冲击模量．讨论了脆性和冲击模量的物理意义．

Impact resistance was defined as the buffering capacity of materials, it mainly depends on two kinds of material behaviour. The first is crack-extension speed, the lower the speed, the higher the impact resistance. The second is limit strain of materials. which is in proportion to impact resistance. According to the points mentioned above, an expression of impact resistance was derived as R=A(KIC /σt,)2σt/E.Brittleness of solid was defined as the reciprocal of impact resistance, it represents the brittle degree of materials ie. B=1/ R. Impact resistance or brittleness does not reflect the ability to resist impact force. Impact modulus (IM) was presented to describe the ability, it is impact resistance multiplied by strength. IM= R·σt=AK/ E=σt/B. In fact, IM represents the impact fracture energy in general process zone, it is a most important parameter for the reliability of brittle components.It is emphased that the brittle degree of solid depends not only on the value of fracture toughness, but on the ratio of toughness to strength and elastic modulus. The brittleness and impact modulus for different materials can be evaluated by using relative brittleness. The criteria for brittleness improvement of materials can be expressed as followes: if α2>b.c brittleness decrease, if α2=b.c no change for brittleness, if a2<b.c brittleness increase. in which,α=toughness/ original toughness; b=strength/original strength, c=elastic modulus/original elastic molulus. The criteria for improvement of impact modulus is: if a2>c impact modulus increase, if a2<c impact modulus decrease.The brittleness, impact reSistance and impact modulus of eleven kinds of materials were measured and calculated.