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To enhance the strength of metastable austenitic stainless steel (ASS) sheet components, a novel method was proposed for the strengthening of a metastable ASS dome by a newly designed bulging device under deep cryogenic conditions. The load curves, Vickers microhardness, thickness distribution, and deformation law of formed dome components at room temperature (RT) and cryogenic temperature (CT) were discussed in detail. The strengthening mechanism of metastable ASS domes was elucidated by phase transformation, and the evolutions of grain boundary and dislocation at RT and CT, respectively. It is found that the strength of metastable ASS domes at CT increases with increasing strain. The strengthening effect of the metastable ASS sheet under biaxial stress state is significantly enhanced. Less martensite is generated at a low plastic strain, and the stability of the austenite phase is noticeably decreased under a large strain at CT. The dislocation distribution at RT is relatively uniform and is not accumulated at grain boundaries, while numerous dislocations at CT are apparently distributed near grain boundaries. The forming of metastable ASS domes at deep cryogenic temperatures is accommodated by both dislocation slip and martensitic transformation. Hence, the strength of metastable ASS thin-walled domes is significantly improved. (1) A novel method was proposed for the strengthening of metastable austenitic stainless steel (ASS) sheet by a newly-designed bulging device under deep cryogenic conditions. (2) Based on the quasi-in situ EBSD observations, the strengthening mechanism of metastable ASS domes was elucidated by microstructural phase transformation, and the evolutions of grain boundary and dislocation at room temperature (RT) and cryogenic temperature (CT). (3) Under the condition of low temperature biaxial stress, the strengthening effect of the metastable ASS sheet is significantly enhanced. Compared to RT, the maximum force increases from 105 to 182 kN at CT. The Vickers hardness increases to 393 HV at CT for the 20 mm dome, which is 38.9% higher than that at RT. (4) The stability of the austenite phase at a large plastic strain is noticeably decreased at CT. Martensitic transformation induced by a great strain is drastic. (5) The forming of metastable ASS domes at low cryogenic temperatures is microstructurally accommodated by dislocation slip and martensitic transformation. [ABSTRACT FROM AUTHOR]

Due to the rapid advancement in processing efficiency, high-speed laser cladding has demonstrated significant potential in the repair and protection of various substrates. In this study, we established a comprehensive evaluation model for the coating quality of Fe-Cr-Ni-based alloy with high-speed laser cladding using the analytic hierarchy process and fuzzy comprehensive evaluation method (AHP-FCE). The weights obtained through the analytic hierarchy process for forming quality, microstructure, and surface performance are as follows: WB1 = 0.1365, WB2 = 0.2385, and WB3 = 0.625, respectively. During the fuzzy comprehensive evaluation step, an evaluation level was graded while quantifying the level range through membership function judgment. By combining subjective and objective evaluations, qualitative issues were transformed into quantitative assessment methods. Through comprehensive evaluation analysis, it was concluded that the scanning speed of high-speed laser cladding had a greater impact on coating thickness compared to powder feeding speed while significantly enhancing microstructure densification. The overlap rate exerted the most influence on dilution rate homogenization of near-surface dendrites. Simultaneously, the optimal preparation technology was determined: laser power 660 W, scanning speed 14,400 mm/min, overlap rate/min. This study transforms multi-objective quality evaluation of high-speed laser cladding coatings into a single objective problem by realizing comprehensive quality quantification and providing a new method for quantitative evaluation and visualization of coating quality. [ABSTRACT FROM AUTHOR]

Based on the two-lane highway traffic model with a work zone presented previously, a new traffic model with a work zone under the control of traffic lights is proposed. The length of the waiting area for vehicles before traffic lights is recommended cautiously after numerical simulation. The relationship between the vehicles' queuing time and the cycle of traffic lights is studied, and the cycle time of traffic lights is obtained also considering people's endurance to the red light. It is found that the traffic lights are effective to ease the traffic congestion in the work zone when the density is medium, and help to eliminate the inducement of traffic accidents. On the other hand, the simulation results show that traffic lights are not needed in the work zone when the traffic density is small. It indicates that the traffic flow in the work zone area can be optimized by using appropriate traffic management when the traffic density varies. [ABSTRACT FROM AUTHOR]

The deformation behaviors of FSW blank are complicated due to the incompatibility of the mechanical property and microstructure for the weld and base material. In order to improve the formability of friction stir welded (FSW) blanks, the weld and base material in this paper were subjected to preheating treatments of 250, 300, 350, 400, and 450 °C, plus a solution treatment of 535 °C. The deformation behavior of the AA2219 FSW blank was characterized using uniaxial tension, microhardness test, hydro-bulging test and electron backscattered diffraction to determine the relationship of the deformation property and microstructure for the FSW blanks. Full strain fields of the tensile and bulging specimens were used to analyze the deformation uniformity of the weld and base material under uniaxial tension and biaxial tension stress states. With the limiting bulging height under various preheating temperatures, the formability behavior of the weld and base material was analyzed during the whole bulging process. The optimum preheating temperature can increase the formability and refrain from abnormal grain growth of the weld on the premise of maintaining the weld strength. The limiting bulging height of FSW blank is obviously improved by the lower preheating temperature from 300 to 350 °C. Additionally, the weld position has a significant impact on the deformation of the whole FSW blanks. [ABSTRACT FROM AUTHOR]