Ma Yafei, Wang Qiang, Guo Zhongzhao, Wang Guodong, Wang Lei, Zhang Jianren
School of Civil Engineering and Architecture, Changsha University of Science & Technology, Changsha 410114, China.
Materials (Basel). 2017 May 14;10(5):532. doi: 10.3390/ma10050532.
Pitting corrosion is one of the most common forms of localized corrosion. Corrosion pit results in a stress concentration and fatigue cracks usually initiate and propagate from these corrosion pits. Aging structures may fracture when the fatigue crack reaches a critical size. This paper experimentally simulates the effects of pitting morphologies on the static and fatigue behavior of steel bars. Four artificial notch shapes are considered: radial ellipse, axial ellipse, triangle and length-variable triangle. Each shape notch includes six sizes to simulate a variety of pitting corrosion morphologies. The stress-strain curves of steel bars with different notch shape and depth are obtained based on static tensile testing, and the stress concentration coefficients for various conditions are determined. It was determined that the triangular notch has the highest stress concentration coefficient, followed by length-variable triangle, radial ellipse and axial ellipse shaped notches. Subsequently, the effects of notch depth and notch aspect ratios on the fatigue life under three stress levels are investigated by fatigue testing, and the equations for stress range-fatigue life-notch depth are obtained. Several conclusions are drawn based on the proposed study. The established relationships provide an experimental reference for evaluating the fatigue life of concrete bridges.
点蚀是局部腐蚀最常见的形式之一。腐蚀坑会导致应力集中，疲劳裂纹通常从这些腐蚀坑处萌生并扩展。当疲劳裂纹达到临界尺寸时，老化结构可能会断裂。本文通过实验模拟了点蚀形态对钢筋静力学和疲劳性能的影响。考虑了四种人工缺口形状：径向椭圆、轴向椭圆、三角形和长度可变三角形。每种形状的缺口包括六种尺寸，以模拟各种点蚀形态。基于静态拉伸试验得到了不同缺口形状和深度的钢筋应力-应变曲线，并确定了各种条件下的应力集中系数。结果表明，三角形缺口的应力集中系数最高，其次是长度可变三角形、径向椭圆和轴向椭圆形状的缺口。随后，通过疲劳试验研究了缺口深度和缺口长宽比对三种应力水平下疲劳寿命的影响，并得到了应力范围-疲劳寿命-缺口深度的方程。基于所提出的研究得出了几个结论。所建立的关系为评估混凝土桥梁的疲劳寿命提供了实验参考。
