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对在700℃,迭加压力过载峰sp=-196MPa的复杂波形载荷作用下,试样的显微断口形貌进行了分析。由于Sp的作用使得疲劳条纹呈现有规律性的半圆弧形宽间距条纹,借助于它,测得疲劳裂纹扩展速率da/dN与△K的关系服从Paris公式;疲劳裂纹Ⅱ阶段与Ⅰ阶段扩展交替出现的形貌证实了:在大应力条件下,裂纹的扩展并不是长裂纹的延伸,而是短裂纹的“超前开动”及“跃迁式”连接过程。由于Sp的作用,断口上出现了三种不同形貌的“台阶”结构及宽条纹上的“挤入”、“挤出”、“二次裂纹”形貌,证实了疲劳条纹形成的滑移机制及形成上述形貌的晶体学位向关系。裂纹的疲劳蠕变混合形貌反映了高温下交互作用的影响。
The microscopic fracture morphology of the sample was analyzed under the condition of 700 ℃, complex pressure overload peak sp = -196MPa. Due to the action of Sp, the fatigue streak shows a regular semicircular arc wide stripe with which the relationship between the fatigue crack growth rate da / dN and △ K is obeyed by the Paris formula; the fatigue crack Ⅱ phase alternates with the phase Ⅰ expansion The appearance of the specimen confirms that under the condition of large stress, the propagation of the crack is not an extension of the long crack, but rather the “precession” and “transition” connection of the short crack. Due to the action of Sp, three different appearances of “step” structure and “crowding in”, “extruding” and “secondary crack” appearances on the wide stripes appear on the fracture surface, and the slip of the fatigue stripes is confirmed Mechanism and the formation of the topography of the crystal orientation relationship. Crack fatigue Creep morphology reflects the impact of high temperature interactions.