The State-of-the-Art Review on Applications of Intrusive Sensing,Image Processing Techniques,and Machine Learning Methods in Pavement Monitoring and Analysis

In modern transportation,pavement is one of the most important civil infrastructures for the movement of vehicles and pedestrians.Pavement service quality and service life are of great importance for civil engineers as they directly affect the regular service for the users.Therefore,monitoring the health status of pavement before irreversible damage occurs is essential for timely maintenance,which in turn ensures public transportation safety.Many pavement damages can be detected and analyzed by monitoring the structure dynamic responses and evaluating road surface conditions.Advanced technologies can be employed for the collection and analysis of such data,including various intrusive sensing techniques,image processing techniques,and machine learning methods.This review summarizes the state-ofthe-art of these three technologies in pavement engineering in recent years and suggests possible developments for future pavement monitoring and analysis based on these approaches.

微量镁对Incoloy825耐蚀合金力学性能的影响

Incoloy825合金作为一种耐蚀合金应用于海洋工程、石油气等行业,由于此类行业环境较为恶劣,不仅需要材料具有出色的耐蚀性能,对力学性能也有较高的要求。本工作利用25 kg真空感应炉冶炼4炉镁含量分别为0wt%,0.0012wt%,0.0030wt%和0.0065wt%的Incoloy825合金,使用金相显微镜、扫描电子显微镜和能谱仪,分别对合金中非金属夹杂物的尺寸、数量进行统计,对夹杂物的形貌和成分进行观察和分析,同时对组织和碳化物进行观察,并对合金进行室温拉伸实验和室温冲击实验,结合实验结果揭示了微量镁改善Incoloy825合金力学性能的机理。研究结果表明,镁的加入使合金中氧和硫的含量减少,夹杂物数量减少,夹杂物成分得到改善,合金洁净度提高,减小了夹杂物对力学性能的影响,同时,晶粒得到细化。合金的屈服强度、抗拉强度、断面收缩率和伸长率均有一定程度的提高,即夹杂物和组织的改善提高了合金的强度和塑性。研究还发现,镁的加入可以将Cr,Fe和Mo等元素从合金的晶界处驱逐,从而减少了晶界处硬脆性碳化物M23C6的析出,显著提高合金的冲击韧性。与未加入镁的合金相比,镁含量达到0.0065wt%时,合金的脱硫率为37.19%,脱氧率为15.71%,单位面积夹杂物数量由75降低至53,大尺寸块状的Al_(2)O_(3)转化为小尺寸的镁铝尖晶石和二维形貌为近圆形的MgO,合金的冲击功由262.5 J提升至384.7 J,提升幅度高达46.55%。杂质元素减少、夹杂物数量减少、晶粒细化、碳化物尺寸减小和晶界碳化物数量减少的综合作用提高了合金的力学性能。