Estimating fatigue damage under variable amplitude multiaxial fatigue loading
Estimating fatigue damage under variable amplitude multiaxial fatigue loading
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DOI：
10.1111/j.1460-2695.2011.01594.x
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发表时间：
2011-12
影响因子：
3.7
通讯作者：
L. Susmel;R. Tovo
中科院分区：
文献类型：
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作者：
L. Susmel;R. Tovo
本文关注的是使用修改的Wohler曲线法（MWCM），以估计的寿命和高周疲劳强度的平原工程材料进行复杂的负载历史，在关键位置，在变幅（VA）多轴应力状态。更详细地，当用于解决恒定振幅（CA）问题时，MWCM假设疲劳损伤在经历最大剪切应力振幅的材料平面（即所谓的临界平面）上达到其最大值，疲劳强度取决于相对于临界平面本身的法向应力分量和剪切应力分量之间的比率。为了将上述准则的使用扩展到涉及VA载荷的情况，这里建议通过定义临界平面来应用MWCM，该临界平面通过经历分解剪应力的最大方差的方向。这样的方向也被用来执行循环计数：因为分解的剪应力是一个一维量，应力循环直接计数的经典雨流方法。在假设的临界点处的时变应力状态的多轴性和非比例性的程度被建议为通过适当的应力比来测量，该应力比考虑了垂直于临界平面的应力的平均值和方差以及沿沿着经历分解的剪应力的最大方差的方向分解的剪应力的方差。所提出的方法的准确性和可靠性进行了检查，使用几个实验结果从文献中。进行验证练习似乎强烈支持的想法，在本文中正式的方法是一个强大的工程工具，适合于估计疲劳损伤下VA多轴疲劳载荷，这不仅适用于中周期，但也在高周疲劳制度。
The present paper is concerned with the use of the modified Wohler curve method (MWCM) to estimate both lifetime and high-cycle fatigue strength of plain engineering materials subjected to complex load histories resulting, at critical locations, in variable amplitude (VA) multiaxial stress states. In more detail, when employed to address the constant amplitude (CA) problem, the MWCM postulates that fatigue damage reaches its maximum value on that material plane (i.e. the so-called critical plane) experiencing the maximum shear stress amplitude, fatigue strength depending on the ratio between the normal and shear stress components relative to the critical plane itself. To extend the use of the above criterion to those situations involving VA loadings, the MWCM is suggested here as being applied by defining the critical plane through that direction experiencing the maximum variance of the resolved shear stress. Such a direction is used also to perform the cycle counting: because the resolved shear stress is a monodimensional quantity, stress cycles are directly counted by the classical rain-flow method. The degree of multiaxiality and non-proportionality of the time-variable stress state at the assumed critical sites instead is suggested as being measured through a suitable stress ratio which accounts for the mean value and the variance of the stress perpendicular to the critical plane as well as for the variance of the shear stress resolved along the direction experiencing the maximum variance of the resolved shear stress. Accuracy and reliability of the proposed approach was checked by using several experimental results taken from the literature. The performed validation exercise seems to strongly support the idea that the approach formalized in the present paper is a powerful engineering tool suitable for estimating fatigue damage under VA multiaxial fatigue loading, and this holds true not only in the medium-cycle, but also in the high-cycle fatigue regime.