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RISS 인기검색어
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- 저자 : Xianbin Ji (검색결과 3 건)
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3D implementation of push-out test in ABAQUS using the phase-field method
Xianbin Yu,Ronghui Wang,Chunguang Dong,Jianyi Ji,Xiaoxia Zhen 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.4
The phase-field method (PFM) localizes the damaged and broken material in concrete with a phase-field order parameter d, successfully avoiding the description of nonsmooth crack surfaces, as well as the pre-setting and tracking of complex crack extension paths. However, most works have focused on 2D and simple 3D problems of non-reinforced concrete due to the high computational cost. A 3D PFM is implemented in the commercial finite element code ABAQUS to model damage and quasi-brittle fractures in composite beam concretes. The damage problem is implemented in the user subroutines UMAT and HETVAL on account of the similarity between the evolution law of the order parameter and the heat transfer law. In addition, a FORTRAN file is used to define the relationships among the material properties. Through this approach, modeling, computational task submission, and post-processing are completed in the GUI of ABAQUS, and the internal nonlinear algorithms are adopted directly. The accuracy of the modeling method is verified by comparing with two classical experimental data in the literature, and the maximum load data and load-displacement curve are well fitted. Moreover, a 3D numerical model for the push-out test of the composite beam is developed. Simulation results are consistent with the test results, such as the trend of the loaddisplacement curve, the damage pattern of the concrete, and the stress condition of the shear bolts. The parametric analysis shows that the compressive and tensile strengths of the shear bonds can significantly affect the load bearing capacity of composite beams, whereas the material parameters of concrete have a limited influence, consistent with the previous experience. The PFM has proven its ability to handle complex quasi-brittle fracture of concrete, and the present work can provide a reference for modeling concrete cracks in engineering structures.
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Improved the hydrogen sorption properties of MgH2 by CeMnZr solid solution
Ying Cheng,Wei Zhang,Biqing Shi,Siqi Li,Bing Dong,Yulian Quan,Xianbin Ji 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.1
Magnesium hydride (MgH2) is one of the promising solid-state hydrogen storage materials because of its high capacity, abundant resource and excellent reversibility. However, the high dehydrogenation temperatures and sluggish kinetics restrict its practical application. It was found that doping catalysts could significantly improve the hydrogen storage properties of MgH2. The solid solution Ce0.8Mn0.1Zr0.1O2 (denoted as CeMnZr) with abundant oxygen vacancy was synthesized and its catalytic influence on the hydrogen sorption properties of MgH2 have been investigated. CeMnZr modified MgH2 composite showed a reduced initial decomposition temperature, almost 62 K lower than the pristine MgH2. At 473 K, MgH2-CeMnZr composite had an absorption capacity of 4.08 wt% hydrogen within 3,500 s, which was about twice better than the pure MgH2 at same condition. MgH2-CeMnZr sample could desorb 2.56 wt% of H2 within 3,500 s at 573 K compared to low desorption rate and 0.85 wt% H2 by as-milled MgH2. The activation energy (Ea) for CeMnZr codoped MgH2 sample is about 50kJ·mol−1 lower than the milled MgH2. Based on the characteration analysis, the in-situ generated MgO and CeH2.51 species as well as abundant oxygen vacancy is believed to play synergistic catalytic effects in enhancing the hydrogen storage properties of MgH2.
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Bing Lu,Chang-Hai Zhai,Shuang Li,Duofa Ji,Xianbin Lu 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.5
The existing push-out test results showed that the ultimate shear capacities and ultimate slips of tie-bars and studs under cyclic loading were signifi cantly lower than those under monotonic loading, which could signifi cantly aff ect the seismic performance of steel–plate concrete composite (SC) structures. The fl exural behavior of two SC beams subjected to cyclic loading was investigated. Specimen SCB1 using tie-bars was partial shear connection, and specimen SCB2 using tie-bars and studs was full shear connection. The failure modes, hysteresis curves, skeleton curves, equivalent lateral stiff ness, energy dissipation, interfacial slip distribution, interfacial shear distributions, and strain in steel plates were researched. The experimental results show that two SC specimens were brittle failure, which primarily resulted from premature shear fracture of shear connectors at the interfaces between steel plate and concrete. Finally, two existing codes for SC structures were used to analyze the bending moment and shear of SC beams as well as interfacial shear of tie-bars and studs. This indicates that due to the diff erence of shear connection ratio between two specimens, the interfacial shear distributions of two SC beams were signifi cantly diff erent.
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