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Deposition and accumulation of marine aerosol and its penetration into concretes exposed to the marine atmospheric zone: an overview

Yuan Qiang, Zhang Jiajia, Huang Zhibin, Zhang Zhipeng, Wang Xiongbiao, Li Binbin

Archives of Civil and Mechanical Engineering

2023

Vol. 23, no. 1

art. no. e65, 2023

Marine aerosol, containing an enormous source of chloride, coupled with severe environmental conditions (e.g., high temperature, high relative humidity), poses a threat to the durability of concrete exposed to the marine atmospheric zone. The distribution of marine aerosol is spatial and temporal dependent, and thus, the deposition rate of airborne chlorides Ddep can vary a lot with geological and environmental factors. Chloride profile in concrete exposed to marine aerosol is a two-zone profile due to the wetting/drying action. The peak chloride concentration Cmax and depth of the convection zone Δx are largely affected by time, materials, environmental conditions which usually is less than 10 mm. Many models based on Fick’s law are developed to predict chloride transport in unsaturated concrete under wetting-drying cycles. However, the prediction of marine aerosol penetration into concrete is far from satisfactory, due to lack of enough experimental and theoretical researches.

Study on force reduction mechanism in ultrasonic assisted grinding based on single-grain scratching

He Yuhui, Zhang Jiajia, Zhou Weihua, Tang Jinyuan, Xu Yanbin, Zhang Yutong

Archives of Civil and Mechanical Engineering

2022

Vol. 22, no. 2

art. no. e80, 1--14

Ultrasonic vibration-assisted grinding (UAG) has been proven to be a promising grinding ability improvement technique due to the grinding force reduction. However, the reduction mechanism is still unclear due to the lack of knowledge on material softening and grain - work piece contact conditions in UAG. In this paper, we present a numerical and experimental study on ultrasonic vibration-assisted scratching (UAS) to understand the force reduction mechanism for UAG from a single-grain perspective. Based on crystal plasticity theory and dislocation density model, the constitutive model for ultrasonic-assisted deformation is established, in which the influence of vibration amplitude and strain rate is considered. To further study the acoustic softening effect, the ultrasonic assisted tensile test is conducted. The finite element model for UAS is developed with the kinematic analysis and the consideration of acoustic softening effect. The comparison between the simulated and experimental results indicates that the process force reduction under ultrasonic vibration can be attributed to (1) the reduction of contact area due to the path interference effect and (2) the yield stress reduction due to the acoustic softening effect. This research can deepen the understanding of the beneficial effect of ultrasonic vibration in UAG and offers new insight for studying other ultrasonic-assisted machining method.