Lesiuk Grzegorz
Faculty of Mechanical Engineering, Department of Mechanics, Materials Science and Engineering, Wroclaw University of Science and Technology, PL-50370 Wrocław, Poland.
Materials (Basel). 2019 Feb 9;12(3):518. doi: 10.3390/ma12030518.
This paper presents the problem of the description of fatigue cracking development in metallic constructional materials. Fatigue crack growth models (mostly empirical) are usually constructed using a stress intensity factor Δ in linear-elastic fracture mechanics. Contrary to the kinetic fatigue fracture diagrams (KFFDs) based on stress intensity factor , new energy KFFDs show no sensitivity to mean stress effect expressed by the stress ratio . However, in the literature there is a lack of analytical description and interpretation of this parameter in order to promote this approach in engineering practice. Therefore, based on a dimensional analysis approach, Δ is replaced by elastic-plastic fracture mechanics parameter-the Δintegral range. In this case, the invariance from stress is not clear. Hence, the main goal of this paper is the application of the new averaged (geometrically) strain energy density parameter Δ based on the relationship of the maximal value of integral and its range Δ. The usefulness and invariance of this parameter have been confirmed for three different metallic materials, 10HNAP, 18G2A, and 19th century puddle iron from the Eiffel bridge.
本文提出了金属建筑材料中疲劳裂纹扩展描述的问题。疲劳裂纹扩展模型（大多为经验模型）通常是利用线弹性断裂力学中的应力强度因子Δ构建的。与基于应力强度因子的动态疲劳断裂图（KFFDs）不同，新的能量KFFDs对应力比所表示的平均应力效应不敏感。然而，为了在工程实践中推广这种方法，文献中缺乏对该参数的分析描述和解释。因此，基于量纲分析方法，用弹塑性断裂力学参数——Δ积分范围取代了Δ。在这种情况下，应力不变性并不明确。因此，本文的主要目标是基于积分最大值及其范围Δ的关系应用新的平均（几何）应变能密度参数Δ。该参数对三种不同的金属材料（10HNAP、18G2A以及埃菲尔铁塔的19世纪搅炼铁）的有效性和不变性已得到证实。
