基于分形维数的预腐蚀铝合金疲劳寿命预测

Fatigue Life Prediction of Pre-corroded Aluminum Alloy Based on Fractal Dimension Method

通过数字图像处理技术对在质量分数为3.5%的NaCl溶液中预腐蚀处理不同时间的2xxx系铝合金试样表面腐蚀形貌进行分析,利用差分盒维数描述腐蚀三维形貌,分析了分形维数与腐蚀时间、疲劳寿命的关系,基于分形维数建立了疲劳寿命预测模型,并通过试验进行验证。结果表明:2xxx系铝合金的分形维数与腐蚀时间呈幂函数关系,与疲劳寿命呈线性关系;建立的寿命预测模型对低周疲劳寿命的预测结果较为保守,与试验值的相对误差在25%以内,对高周疲劳寿命的预测结果较为精准,与试验值的相对误差减小到15%以内;通过寿命预测模型计算得到的疲劳极限与试验值接近,相对误差在5%以内。

The surface corrosion morphology of 2xxx aluminum alloy specimens pre-corroded with 3.5% mass fraction NaCl solution for different times was analyzed by digital image processing technique. The three-dimensional corroded morphology was described by Differential Box-Counting method. The relationships between fractal dimension, corrosion time and fatigue life were analyzed, and the fatigue life prediction model based on fractal dimension was established and verified by experiments. The results show that the relationship between the fractal dimension and corrosion time was a power function, while the fractal dimension was linear with the fatigue life. The prediction results of the established life prediction model for low cycle fatigue lives were relatively conservative, and the relative error with the test result was within 25%. The prediction results for high cycle fatigue lives were relatively accurate, and the relative error of the test result was reduced to less than 15%. The fatigue limit calculated by life prediction model was close to the test value, and the relative error of less than 5%.