Considering high risk, long construction period, high construction and maintenance costs, bridge management is asynchronous, unintelligent and inefficient. The purpose of this research is to investigate a new approach with its supporting building information modelling (BIM) and Internet of Things (IoT) tool to enhance the smart management in bridge life cycle. BIM provides detailed geometric and semantic information and IoT contains the management and analysis of the actual condition of the bridge. An example of a super bridge under construction in Xinjiang is used to illustrate the developed system. Results show that the developed system can significantly grasp the quality of the bridge in time, reduce the construction risk and construction period. The developed BIM/IoT-based system is also effective and practical in the quality and risk management among multiple locations, such as smart buildings, smart tunnels, and even smart cities.
Nonisothermal forging is an efficient plastic forming method for titanium alloys, but at the same time, it can produce large and uneven residual stress, which seriously affects the service life of components. In order to quantitatively analyze the influence of forging process parameters on the residual stress of Ti-6Al-4V alloy forgings, a numerical model was first established and optimized in combination with experiments. Then, the effects of deformation temperature, deformation degree, and deformation speed on the residual stress of forgings were analyzed by orthogonal test, and the optimal combination of forging process parameters was obtained. Finally, the multiple regression analysis was employed to propose multivariate regression models for the prediction of the average equivalent residual stress. Results show that the prediction model can be used for predicting the residual stress of Ti-6Al-4V alloy forgings with a higher reliability.
Smooth surfaces are conducive to improving the lubrication of gears in mechanical systems. In this study, chemical mechanical polishing (CMP) was used to process 18CrNiMo7-6 case hardening steel, a typical material for gears. The results reveal that compared with formic acid and oxalic acid, citric acid can be used as a suitable complexing agent without causing apparent corrosion, probably due to the fact of its relatively stable adsorption. A synergistic effect exists between citric acid and H2O2. At pH 3, with 0.067 M citric acid and 1 wt% H2O2, a satisfactory CMP performance (i.e., a 514 nm/min material removal rate (MRR) and a 0.85 nm surface roughness Sa) was achieved. After polishing, no observable defects were found on the surface, and no discernible processing damage occurred to the substrate. In terms of the CMP’s mechanism, iron is first oxidized to Fe2+ and Fe3+, which then react with citric acid to form complexes. On the one hand, most of the complexes may stay on the surface to prevent further corrosion and, thus, the surface quality is excellent. On the other hand, the complexes may reduce the surface integrity and, thus, the MRR is high. The findings open new avenues for attaining ultra-smooth steel surfaces with CMP through controlling corrosive wear.
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