【摘要】 使用扫描电镜研究分析油淬火钢丝制弹簧及低温形变热处理钢丝制弹簧的疲劳断裂过程。指出油淬火簧属于Ⅰ型断裂,而形变簧属于Ⅲ→Ⅰ型断裂,即螺蜷弹簧在扭转疲劳载荷下,先按Ⅲ型方式断裂,至一定深度后,再转换为Ⅰ型方式断裂,这种断裂过程和反平面应变——Ⅲ型载荷断裂相一致。本文讨论了:(1)弹簧形成不同断裂类型的原因及形变簧产生Ⅲ→Ⅰ型断裂变化与裂纹扩展深度关系。(2)提出Ⅲ→Ⅰ型转变机理图。(3)指出不同热处理方法形成的显微组织对断裂过程的影响,认为织构是引起Ⅲ型断裂的原因。更多还原

【Abstract】 Fatigue fractography of valve springs made of oil tempered spring steel wire and low temperature thermomechanically treated spring steel wire was studied. Experimental results showed that the O. T springs were mode Ⅰ frature and the LTMT springs mode Ⅲ→ I frature, it means that the LTMT coiled springs under torsional fatigue loading fratured as mode Ⅲ at first and after crack propergated up to a certain depth fracture changed into mode Ⅰ. The fracture possessed itself of all the characters of anti plane shear mode fracture——mode Ⅲ fraeture. The formation reasons of different fracture modes and mode changes, the mechanism of mode changes and the influences of microstructures on fracture were discussed.更多还原