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- 저자 : Xiangdong Wu (검색결과 2 건)
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Xiangdong Kong,Kaixian Ba,Bin Yu,Yuan Cao,Liujie Wu,Lingxiao Quan 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.10
A Highly-integrated valve-controlled cylinder (HIVC) that has the advantage of large power weight ratio and fast response is widelyapplied in many fields. To ensure high performance of HIVC, control strategy selection and structure parameters optimization are essential;thus, performance-influenced main parameters and secondary parameters should be well-grasped to target control compensation andstructure optimization. Trajectory sensitivity analysis (TSA), a branch of sensitivity analysis, can be adapted to research on the effects ofcontrol and structure parameter variation on system performance; the analysis conclusions can be used to improve system performanceand the analysis has been applied in many applications in various fields. In this paper, based on the mathematical model of the First-ordertrajectory sensitivity analysis (FOTSA), the mathematical model of Second trajectory sensitivity analysis (SOTSA) is further derived; thegeneral expression of the second-order trajectory sensitivity equations and the special expression that is applicable to each system parametersensitivity analysis of HIVC are built respectively. Furthermore, based on the position control system of the nonlinear mathematicalmodel of HIVC involved with servo valve dynamic characteristics, flow-pressure nonlinearity, initial piston position of servocylinder, and friction nonlinearity, the coefficient items and the free items matrices of the special expression are calculated. Moreover, theFirst-order trajectory sensitivity function (FOTSF) and the Second trajectory sensitivity function (SOTSF) of the 17 main parameters inHIVC are computed on the MATLAB/Simulink platform under nine typical working conditions of the displacement step response. Then,the dynamic change rules and the differences and similarities of each parameter sensitivity analysis results are obtained through FOTSAand SOTSA under different working conditions with different parameter variations; each parameter sensitivity variation histogram basedon the two kinds of sensitivity indexes, including the maximum value of the percentage absolute value and the absolute value summationwithin the sampling time, are given. Furthermore, differences and similarities of each parameter sensitivity index change rule and valueare quantitatively analyzed. Finally, the sensitivity index change rules and values of the four parameters in the position control system ofHIVC, including system supply oil pressure, proportion gain, initial piston position of servo cylinder, and load are experimentally verified. All above studies indicate that each parameter SOTSA result of HIVC vary under different working conditions. When parametervariation is significant, the differences in certain parameter sensitivity analysis between FOSTA and SOTSA are relatively significant;and SOTSA results are more similar to the test results, which illustrates that SOTSA results are more accurate.
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Mesoscale Deformation Incompatibility Analysis of DP1180 Steel
Bingying Zhou,Yisheng Zhang,Xuexi Cui,Fei Han,Bobin Guan,Xiangdong Wu,Min Wan 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.10
Advanced high-strength steel (AHSS) is of great technological interest in automotive lightweight applications. The dualphase (DP) steel with a higher volume fraction of martensite has been rarely studied. In this work, the micromechanical deformation incompatibility of DP1180 steel was analyzed by a microstructure-based representative volume element (RVE) model. Via the electron-backscattered diffraction (EBSD) and the open-source software DREAM.3D, the statistically real microstructure-based RVE model was established. The flow curve of ferrite was obtained by the dislocation-based method. And the flow curve of martensite was obtained by the isostrain method (ISM) and the non-isostrain method (NISM). The simulation results showed good coincidence with the experiments. Furthermore, the ISM and the NISM were well clarified and improved. The microscale stress and strain in ferrite and martensite are approximately normal distributions due to the deformation incompatibility. The simulations verified that martensite carries much higher stress than ferrite. The mean value of strain in martensite is smaller than that in ferrite. And the strain variances of ferrite and martensite are similar. A larger variation range of stress triaxiality in ferrite indicates that the ferrite has gone through a more complex stress state. While the martensite has been approaching from the tension–compression state to the uniaxial-tension state. Consequently, the strain localization and damage initiation are predicted to be preferentially through ferrite compared to martensite, which is in good agreement with the results of the in situ tensile test. This paper provides a detailed analysis of the deformation incompatibility of the DP steel, especially in which the volume fraction of martensite is larger than that of ferrite. And it has theoretical significance for accurately predicting the micromechanical deformation behavior of multi-phase materials.
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