轧辊材料疲劳裂纹扩展理论计算与分析

辊面剥落是轧辊失效的主要形式之一。依据疲劳裂纹扩展理论,计算了轧辊材料裂纹扩展过程中裂纹扩展速率与应力强度因子幅的关系即da/d N—ΔK,分析了各因素对裂纹扩展速率的影响以及不同轧辊的裂纹扩展特征。结果表明,弹性模量、应力比、残余应力、晶粒度、断裂塑性、工作应力、断裂强度等对轧辊裂纹扩展速率的影响越来越不明显,弹性模量影响最大,而屈强比几乎没有影响;轧辊材料较高的弹性模量、较低的残余应力、较粗大的晶粒、较高的断裂塑性可以有效抑制轧辊裂纹的疲劳扩展;轧辊工作层比心部、支承辊比工作辊、锻钢辊比铸铁辊具有更高的耐裂纹扩展断裂能力。结果有助于分析轧辊失效机理并采取有效措施,防止轧辊剥落。

Calculation and analysis of fatigue crack propagation in roll material

Surface spalling is one of main forms of the roll failure .The crack propagation process d a/dN-ΔK was calculated for the roll material with the fatigue crack propagation theory . The effects of various parameters on the roll crack growth were analyzed , as well as the crack propagation characteristics of different rolls .The results showed that elastic modulus , stress ratio, residual stress , crystal size , fracture plastic , work stress and tensile strength had less and less effects on the crack propagation rate , elastic modulus was the most remarkable factor and tensile strength was the lest .Higher elastic modulus , lower residual stress , rougher crystal , and higher fracture plastic of the roll material could efficiently restrain fatigue crack propagation of rolls .Work layer had higher crack propagation resistance than centre of the roll , so as to the backup roll than the work roll and the forged roll than the cast roll .It was helpful to make clear the failure mechanism and take effective precautions against the roller ’ s spalling .