Corrosion fatigue crack growth mechanisms in welded joints of marine steel structures

This paper presents a model of fatigue crack growth in a welded joint and a two-dimensional model of anodic dissolution based on Donahue model and anodic dissolution mechanism,respectively.In addition,a model for predicting the corrosion fatigue crack growth rate in welded joints of steel marine structures is established and crack growth mechanisms are analyzed.The results show that during early stages of crack growth,corrosion fatigue crack growth rate in welded joints is mainly controlled by corrosion action,whereas cyclic loading becomes more influential during the later stage of crack propagation.Loading frequency and effective stress ratio can affect rupture period of protective film at the corrosion fatigue crack tip and the length of corrosion crack increment,respectively,which changes the influence of corrosion action on crack growth rate.However,the impact of stress amplitude on crack growth rate is only significant when crack propagation is caused by cyclic loading.Welding residual stress not only improves the effective stress ratio of cyclic loading,but also promotes crack closure and increases corrosion fatigue crack growth rate in welded joints.Compared to corrosion action,welding residual stress has a more significant influence on crack growth caused by cyclic loading.

基于“互联网+”的课程思政教学探索与实践——以“土质学与土力学”课程为例

为了培养德智体美劳全面发展的高素质军事人才,促进专业课与思想政治教育的有机融合势在必行。基于“互联网+”的时代发展背景,以“土质学与土力学”课程为依托,运用信息技术手段优化课程教学模式,从课程教学内容重构、教学方法改进、思政元素挖掘、考核评价机制改革等方面对课程思政进行了初步探索。开展“互联网+”课程思政,能够激发学员的学习兴趣,提高学员的学习主动性,增强学员的专业素养和思想觉悟,有利于实现为党育才、为国育人的宏伟目标。

Mechanism of corrosion fatigue fracture of friction stir welding joints of 7075 aluminium alloy in 3.5% NaCl solution

The corrosion fatigue fracture mechanism of friction stir welding(FSW) joints of 7075 aluminium alloy in3.5% NaCl solution is investigated. The corrosion fatigue crack source originates from the junction of nugget zone(NZ)and thermo-mechanical affected zone(TMAZ). Multiple crack sources are developed at the same time, and they merge into large cracks along the boundary line of NZ and TMAZ during the propagation stage. Furthermore, a mutual reinforcement coupling always exists between corrosion and cyclic loading during the initiation and propagation of corrosion fatigue crack. It is necessary to consider the effect of welding residual stress for understanding the mechanism of corrosion fatigue fracture of FSW joints.

《道路工程材料》课程教学方法的初步探讨

《道路工程材料》课程是我校道路桥梁与渡河工程专业一门重要的专业基础课。然而,该课程具有内容复杂,概念多,术语多,偏重叙述性等特点,学员在学这门课时往往感觉枯燥无味。对此,笔者结合自己的教学经验,就该课程的教学方法进行了初步探讨,以求获得良好的教学效果。

课时大幅压缩条件下探索如何上好“道路工程”这门课

“道路工程”这门课是我校道路桥梁与渡河工程专业的一门专业背景课程,在新的培养方案下,该课程的学时大幅度压缩,在这样的条件下,如何将繁多的教学内容完整有效地传授给学员,作者结合自己的教学经验,提出了几点个人的做法,以期与同行进行交流。