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Application of distributed temperature sensing for cracking control of mass concrete
摘要： This paper presents a framework of cracking control for a mass concrete structure in a reservoir project, by taking advantage of Distributed Temperature Sensing (DTS) system. The DTS system in this project, mainly consisting of an Optical Backscatter Reflectometer (OBR) interrogation unit and a single fibre-optic cable, was deployed to measure and monitor concrete temperatures of an intake tower in block placement. The temperature measurements in concrete blocks were utilized as the fundamental data to determine the thermal properties of the cast-in-situ concretes, through the inverse analysis method based on temperature simulation. Based on thermal stress simulation using the thermal properties, cracking risks of each concrete block were predicted and evaluated under the modes of temperature control associated with the time-varying construction and ambient conditions, for appropriate modes before and after the concrete placement. The framework of cracking control, developed by integrating the DTS measurement with the temperature forecast and the cracking prediction based on thermal stress simulation and cracking risk evaluation, improves the efficiency of temperature regulation and cracking control in mass concrete construction, and can be further integrated into the intelligent construction management of concrete projects.
关键词： Cracking control,Fibre-optic,DTS,Mass concrete
更新于2025-09-23 15:21:21
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Cracking behavior and control of β-solidifying Ti-40Al-9V-0.5Y alloy produced by selective laser melting
摘要： A β-solidifying Ti-40Al-9V-0.5Y (at.%) alloy with a high cracking sensitivity has been successfully fabricated by selective laser melting (SLM) in this study. The influence factors for cracking sensitivity, cracking behavior and crack inhibition mechanism were investigated. The results show that the effects of process parameters on cracking sensitivity strongly depend on the cooling rate in molten pool with different heat transfer modes. The conduction mode with higher cooling rates exhibits a higher cracking sensitivity in comparison to the keyhole mode. Microstructure characteristics and phase transformations controlled by cooling rate determine the inherent ductility of β-solidifying γ-TiAl alloys during SLM. On this basis, the formation and inhibition mechanism of solidification and cold cracking are proposed. Finally, the crack-free Ti-40Al-9V-0.5Y sample with fine equiaxed microstructures and favorable mechanical properties (microhardness of 542±19 HV, yield strength of 1871±12 MPa, ultimate strength of 2106±13 MPa and ultimate compressive strain of 10.89±0.57 %) can be produced by SLM. The strengthening mechanism can be attributed to grain refinement and precipitation strengthening.
关键词： Phase transformation,Selective laser melting,Cracking behavior,Microstructure,β-solidifying γ-TiAl alloy,Cracking control
更新于2025-09-16 10:30:52