Influence of inclusion size on S-N curve characteristics of high-strength steels in the giga-cycle fatigue regime
Influence of inclusion size on S-N curve characteristics of high-strength steels in the giga-cycle fatigue regime
复制标题
夹杂物尺寸对高强度钢十周疲劳状态S-N曲线特性的影响
DOI：
10.1111/j.1460-2695.2009.01370.x
复制
发表时间：
2009-08-01
影响因子：
3.7
通讯作者：
Shiozawa, K.
中科院分区：
文献类型：
--
作者：
Lu, L. T.;Zhang, J. W.;Shiozawa, K.
高强度钢的疲劳断裂通常是由材料表面的细小缺陷或材料表面以下区域的非金属夹杂物引起的。在旋转弯曲载荷下，高强度钢的S-N曲线由表面缺陷诱发断裂和内部夹杂物诱发断裂两条曲线组成。表面缺陷引起的断裂发生在高应力幅值和低循环下。然而，表面下夹杂物诱发的断裂发生在低应力幅值和超过 10(6) 个循环（千兆循环疲劳寿命）的高循环区域。旋转弯曲得到的S-N曲线存在一定的应力范围，裂纹萌生位置从表面到表面以下发生变化，形成阶梯式S-N曲线或双重S-N曲线。另一方面，在循环轴向载荷作用下，高强钢的S-N曲线呈现连续下降趋势，在整个振幅范围内都会发生表面缺陷或内部夹杂物诱发的断裂。本文针对高强度钢在十次疲劳状态下的旋转弯曲和循环轴向载荷，研究了影响高强度钢S-N曲线特性的因素，包括夹杂物尺寸和弯曲疲劳应力梯度。然后，根据 S-N 数据估计的表面下裂纹扩展速率，解释了夹杂物尺寸对疲劳寿命离散性的影响，并阐明了表面下夹杂物诱发断裂的 S-N 曲线形状取决于夹杂物尺寸。
Fatigue fracture of high-strength steels often occurs from small defect on the surface of a material or from non-metallic inclusion in the subsurface zone of a material. Under rotating bending loading, the S-N curve of high-strength steels consists of two curves corresponding to surface defect-induced fracture and internal inclusion-induced fracture. The surface defect-induced fracture occurs at high stress amplitude levels and low cycles. However, the subsurface inclusion-induced fracture occurs at low stress amplitude levels and high-cycle region of more than 10(6) cycles (giga-cycle fatigue life). There is a definite stress range in the S-N curve obtained from the rotating bending, where the crack initiation site changes from surface to subsurface, giving a stepwise S-N curve or a duplex S-N curve. On the other hand, under cyclic axial loading, the S-N curve of high-strength steels displays a continuous decline and surface defect-induced or internal inclusion-induced fracture occur in the whole range of amplitudes. In this paper, influence factors on S-N curve characteristics of high-strength steels, including size of inclusions and the stress gradient of bending fatigue, were investigated for rotating bending and cyclic axial loading in the giga-cycle fatigue regime. Then, based on the estimated subsurface crack growth rate from the S-N data, effect of inclusion size on the dispersion of fatigue life was explained, and it was clarified that the shape of S-N curve for subsurface inclusion-induced fracture depends on the inclusion size.