Q420钢管大气腐蚀后的抗侧撞性能

为研究大气腐蚀对Q420钢管构件服役期内耐撞性的影响，提出了计及腐蚀损伤的材料模型。引入损伤因子（ω）修正Voce模型，推导随腐蚀程度变化的低合金钢材本构方程，并通过加速腐蚀试验结果回归相应参数。利用ABAQUS软件定义构件材料特性，建立起受腐蚀的Q420钢管仿真模型，采用显式动力算法分析多种初始状态下，撞击体与不同腐蚀程度钢管的冲击响应规律。开展预腐蚀Q420钢管的落锤试验，将试验结果与数值计算结果进行对比，验证所建模型的合理性。结果表明:大气腐蚀导致材料名义强度降低，对Q420钢管抗撞击能力影响显著；随着腐蚀程度增加，冲击力峰值减小，撞击时间和深度增加；Q420钢管受腐蚀后抗冲击刚度减小，构件整体变形耗能增加，表明大气腐蚀使其抗冲击性能下降；同等动能增量下，增大撞击体初速度比增加初始质量获得的冲击力峰值增幅更大，而所得到的接触时间增幅更小。

Lateral impact resistance of Q420 steel tubes after atmospheric corrosion

Q420 circular steel tubes are widely used to build large-scale steel structures. Such buildings serving in mountain areas are subject to atmospheric corrosion and impact load. In order to study the effect of atmospheric corrosion on the crashworthiness of Q420 steel tube members during service, a material model considering corrosion damage was proposed which treated corrosion damage as a change in material parameters. Specifically, a damage factor ω was introduced to modify the Voce constitutive equation based on the one-dimensional damage theory. A constitutive equation for low alloy steel varied with the degree of corrosion was deduced, these model parameters were determined through accelerated corrosion test that used acidic solution to accelerate steel corrosion and used static force to stretch the specimens. Based on the proposed constitutive method, relevant material properties were defined by utilizing the ABAQUS software to establish the finite element model of the Q420 steel tubes. A number of 0.84 meters long Q420 steel tube member models within different degrees of corrosion were developed, and these pipes were impacted at their mid-span by a flat-headed impactor with a certain mass and initial velocity. An explicit dynamic algorithm has been used for the simulation to analyze impact response law of rigid impactor and corroded steel pipes under various initial conditions. In addition, a series of impact tests were conducted to compare the behaviour of pre-corroded Q420 steel tubes subjected to lateral impact by drop hammers falling through changing initial height. The weight loss of pipes respectively was 0%, 10%, 20%, 30% and 40%, and the speed of moving hammers was 4.00, 5.79 and 7.43 m/s. Steel tube specimens were subjected to a constant axial pressure, without considering the effect of the axial force on test results. Numerical results were compared with test results to verify the rationality of the established models. According to numerical and experimental results, it demonstrates that atmospheric corrosion leads to a decrease in the nominal strength of the materials, which has a significant effect on the impact resistance of Q420 steel tubes and causes variation in the time history curve of impact force. With increase of corrosion degree of specimens, the yield strength and ultimate tensile strength of Q420 steel materials show a downward trend. As weight loss of Q420 steel tube increases, peak value of impact force decreases and duration and depth of impact increases. It indicates the decline of lateral impact resistance of Q420 steel tubes affected by atmospheric corrosion that impact stiffness of Q420 steel tubes decreases and overall deformation energy consumption of these components increases after corroded. The initial conditions of impactor have different effects on collision process under same kinetic energy increment. Compared with the increase of the initial mass, increase in the peak value of impact force obtained by increasing the initial velocity of impactor is greater, while the increase of duration is smaller.