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| 1 | On the heterogeneous microstructure development in the welded joint of 12MnNiVR pressure vessel steel subjected to high heat input electrogas welding显示文摘Microstructure features of 12 MnNiVR pressure vessel steel welded joint deposited by the high heat input electrogas welding have been systematically investigated. It is revealed that the welded joint is featured by a heterogeneous juxtaposition. The coarse grained heat-affected zone(CGHAZ) primarily consists of lath bainites and minor granular bainites. The fine grained heat-affected zone(FGHAZ) is dominated by polygonal ferrites, pearlites, and fine cementite particles. Moreover, electron backscatter diffraction results further demonstrate that the CGHAZ is populated by coarse prior austenite grains(PAGs) with high frequency(61.3%) of low angle grain boundaries(LAGBs). On the other hand, the FGHAZ is filled with fine PAGs with a lower frequency(19.6%) of LAGBs. Such microstructural differences may likely contribute to differed mechanical properties for samples tested at designed positions. | Yang Shen Ju Leng Cong Wang | 2019 | Journal of Materials Science & Technology2019，35，8： | 8 |
| 2 | A Parallel Computational Model for Three-Dimensional,Thermo-Mechanical Stokes Flow Simulations of Glaciers and Ice Sheets显示文摘This paper focuses on the development of an efficient,three-dimensional,thermo-mechanical,nonlinear-Stokes flow computational model for ice sheet simulation.The model is based on the parallel finite element model developed in[14]which features high-order accurate finite element discretizations on variable resolution grids.Here,we add an improved iterative solution method for treating the nonlinearity of the Stokes problem,a new high-order accurate finite element solver for the temperature equation,and a new conservative finite volume solver for handling mass conservation.The result is an accurate and efficient numerical model for thermo-mechanical glacier and ice-sheet simulations.We demonstrate the improved efficiency of the Stokes solver using the ISMIP-HOM Benchmark experiments and a realistic test case for the Greenland ice-sheet.We also apply our model to the EISMINT-II benchmark experiments and demonstrate stable thermo-mechanical ice sheet evolution on both structured and unstructured meshes.Notably,we find no evidence for the“cold spoke”instabilities observed for these same experiments when using finite difference,shallow-ice approximation models on structured grids. | Wei Leng Lili Ju Max Gunzburger Stephen Price | 2014 | Communications in Computational Physics2014，16，9： | 1 |
| 3 | A practical PID variable stiffness control and its enhancement for compliant force-tracking interactions with unknown environments显示文摘Compliant interaction control is a key technology for robots performing contact-rich manipulation tasks.The design of the compliant controller needs to consider the robot hardware because complex control algorithms may not be compatible with the hardware performance,especially for some industrial robots with low bandwidth sensors.This paper focuses on effective and easy-to-use compliant control algorithms for position/velocity-controlled robots.Inspired by human arm stiffness adaptation behavior,a novel variable target stiffness(NVTS)admittance control strategy is proposed for adaptive force tracking,in which a proportional integral derivative(PID)variable stiffness law is designed to update the stiffness coefficient of the admittance function by the force and position feedback.Meanwhile,its stability and force-tracking capability are theoretically proven.In addition,an impact compensator(Impc)is integrated into the NVTS controller to enhance its disturbance-suppression capability when the robot is subjected to strong vibration disturbances in complicated surface polishing tasks.The proposed controllers are validated through four groups of experimental tests using different robots and the corresponding results demonstrate that they have high-accuracy tracking capability and strong adaptability in unknown environments. | ZHANG Xin ZHOU Hao LIU JinGuo JU ZhaoJie LENG YuQuan YANG ChenGuang | 2023 | Science China(Technological Sciences)2023，66，10： | 0 |
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