三维表面粗糙度对18CrNiMo7-6钢旋转弯曲疲劳寿命的影响

目的探究固定载荷下三维表面粗糙度S_a对18CrNiMo7-6钢旋转弯曲疲劳寿命的影响。方法通过砂纸研磨制备不同表面粗糙度及纹理方向的18CrNiMo7-6钢旋转弯曲疲劳试样,测量所有试样的表面粗糙度参数S_a及三维表面形貌参数S_q、S_z、S_(sk)、S_(ku)。对试样进行旋转弯曲疲劳试验,分析疲劳寿命。结果在相同或相近粗糙度的情况下,轴向纹理疲劳试样疲劳寿命大于周向纹理疲劳试样疲劳寿命。相同纹理方向的情况下,表面三维粗糙度S_a越低,试样疲劳寿命越高。试样疲劳寿命次数与表面粗糙度参数S_a及三维表面形貌参数S_q、S_z、S_(sk)、S_(ku)均有明显的相关性。结论对于18CrNiMo7-6钢旋转弯曲疲劳试样,拥有平行于疲劳应力的机械加工纹理比垂直于疲劳应力的机械加工纹理具有更小的危害性。降低18CrNiMo7-6试样表面粗糙度,能够有效提高试样旋转弯曲疲劳寿命。纹理方向平行于疲劳应力方向的试样,表面偏斜度S_(sk)对零件疲劳寿命影响不明显。

Effect of Three-dimensional Surface Roughness on Rotating Bending Fatigue Life of 18CrNiMo7-6 Steel

The work aims to explore the effect of three-dimensional surface roughness Sa on the bending fatigue life of 18CrNiMo7-6 steel under the fixed load. 18CrNiMo7-6 steel rotating bending fatigue specimens with different surface roughness and texture path were prepared by sandpaper grinding. The surface roughness parameters Sa and three-dimensional surface topography parameters Sq, Sz, Ssk, and Sku of all specimens were measured. Rotational bending fatigue test was carried out on the specimen to analyze the fatigue life of the specimen. The fatigue life of axial textured specimens with the same or similar roughness was greater than that of circumferential textured specimens. Under the same texture direction, the lower the three- dimensional surface roughness was, the higher the fatigue life was. The fatigue life times of specimens were significantly correlated with Sa and Sq, Sz, Ssk, and Sku. For 18CrNiMo7-6 steel rotating bending fatigue specimens, machining grooves perpendicular to fatigue stress are more harmful than machining grooves parallel to fatigue stress. Reducing the surface roughness of the 18CrNiMo7-6 steel specimen can effectively improve the rotational bending fatigue life of the specimen. The surface skewness Ssk of the specimen with texture direction parallel to the fatigue stress direction has no obvious influence on the fatigue life of the part.