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2 2024

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Influence of diffusion angle on sediment concentration in front inflow forebay of pumping station

Fan Xinjian, Zhang Jiahui, Yao Wei, Dong Chunhai, Wang Lirong, Tian Hao

Ecological Chemistry and Engineering. S

2024

Vol. 31, nr 3

398--409

The numerical simulation and field investigation of solid-liquid two-phase flow are carried out in a large-scale forward intake forebay with various diffusion angles at the Jingtaichuan Pumping Irrigation Project in Gansu Province, China. The purpose is to investigate the properties of sediment deposition in the pumping station forebay. The results indicate that the low-sediment concentration area is in the forebay’s centre, whereas the high-sediment is near the two side walls flanks. The sediment concentration increases dramatically from the centre to the sides. Both the high-sediment concentration area and the sediment concentration increase with water depth. The forebay’s narrowing diffusion angle causes the high-concentration area to gradually decrease while the low-concentration area gradually increase. Furthermore, the amount of siltation and sediment deposition efficiency decrease, resulting in a large increase in forebay sediment concentration and sedimentation efficiency. The sediment concentration and water flow velocity reveal a quadratic polynomial relationship. This study can provide a guide and reference for the design and construction of comparable large-scale pumping station forebays.

Achieving high tensile properties and impact toughness in ultrahigh strength lean alloy steel by quenching and partitioning treatment

Wang Lirong, Liang Yilong, Zhao Fei, Xu Fahong, Lei Lei, Long Shaolei, Yang Ming, Jiang Yun

Archives of Civil and Mechanical Engineering

2024

Vol. 24, no. 1

art. no. e32, 2024

In this study, a desirable combination of strength, ductility, and toughness in low-carbon 30CrMnSiA steel is achieved by a hierarchical multiphase microstructural architecture subjected to one- and two-step quenching and partitioning (Q&P) processes. The microstructural constituents are studied by EBSD, x-ray diffraction, dilatometry, and TEM. Experimental results show that microstructural refinement occurs in the martensite and bainite at a lower quenching temperature, where more Bain groups form in one close-packed plane group. This causes random distribution between martensite and bainite blocks, enlarging the volume of high-angle grain boundaries. Such refined microstructure, particularly for the increased martensite with higher-density dislocations, causes an increased strength at a decreased quenching temperature. By comparison, increased quenching and partitioning temperature produces more stable film-like retained austenite (RA) and a low dislocation density in martensite/bainite (M/B); thus, it provides better deformation by accommodating with M/B laths and absorbing substantial energy due to the transformation-induced plasticity effect. The lower dislocation density, the higher volume fraction of RA, and the higher HAGBs improve the impact toughness and tensile properties of lean alloy steel through a moderate Q&P process.