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Numerical Simulation of Magnetorheological Liquid Sedimentation Character
Jun Qiu,YiPing Luo,Jiao Luo,Ying Wang,Hongyi Wang 한국자기학회 2020 Journal of Magnetics Vol.25 No.3
In this paper, numerical simulation is used to simulate the sedimentation process of magnetorheological fluid (MRF), and the sedimentation time of MR fluid is predicted by this method. Firstly, based on the existing literature simulation method and its improvement, a numerical simulation method is proposed to simulate the MR fluid sedimentation process. Finally, a variety of MR fluid samples are prepared to detect the accuracy of the simulation results of the constructed numerical simulation method. It can be proved by comparing the measured sedimentation time with the simulated sedimentation time, and the method constructed in this paper can predict the sedimentation time of the more complicated MR fluid well, which has good practicability.
Surface Mesh Generation in Parametric Space Using a Riemannian Surface Definition
Cui Dai,Zhaoxue Wang,Liang Dong,Yiping Chen,Junfeng Qiu 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.2
In order to solve the problem of generating distortion elements in the mapping from parameter space to real space, and the boundary coincidence of the mesh generated by the software quality, an approach for parametric surface mesh generation based on Riemannian metric, combined with Delaunay triangulation and AFT is proposed. In our algorithm, the boundary curves are discretized based on the proximity and curvature of the curves in the model after derivation the correlation of curve length between parametric space and real space. Background meshes of parametric space were generated by using improved AFT, and could improve the efficient of the algorithm and control element sizing and metric values. When background mesh of parametric space were refined, to counteract mapping distortion, the traditional Delaunay incremental insertion kernel is replaced by inserting the center of triangle circumscribed ellipse, and the algorithm for locating ellipse center and judging whether nodes within ellipse. In this paper, the details of the surface mesh generated by the algorithm are introduced in detail. The algorithm proposed in this paper has the characteristics of reliable algorithm, high mesh generation efficiency and mesh quality. Finally, the reliability of the proposed algorithm is verified by an example of surface mesh generation.
Modelling and Prediction of Stress Relaxation for Thermal Bonded Nonwoven Geotextiles
Shiyuan Sun,Xiaoping Gao,Chunhong Fu,Yudong Zhou,Xiaoying Wei,Jiaxin Li,Yiping Qiu 한국섬유공학회 2020 Fibers and polymers Vol.21 No.7
Stress relaxation experiments were performed on three types of thermal bonded nonwoven geotextiles in this studyto model and predict their stress relaxation behaviors. Four mechanical models, including the standard linear solid mechanicsmodel, Eyring’s model, the modified two-Maxwell-unit model and the modified three-Maxwell-unit model were used topredict stress values for 600 h based on 3 and 90 h experimental relaxation data. Results indicated that Eyring’s model and themodified three-Maxwell-unit model fitted the experimental results better than the other two. Estimation using modified three-Maxwell-unit model seemed to construct an upper bound while that using Eyring’s model form a lower bound for thecorresponding experimental data. In addition, predicted curves were much closer to the experimental curve when equationsof the two models were built with the 90 h experimental data than those data of 3 h. Thus, the prediction capability of the twomodels can be substantially improved by employing the data with longer time. In summary, the combination of the modifiedthree-Maxwell-unit model and Eyring’s model can well forcast the range of actual stress during stress relaxation experimentswith the longer term experimental data.
The influence of moisture on atmospheric pressure plasma etching of PA6 films
Zhiqiang Gao,Shujing Peng,Jie Sun,Lan Yao,Yiping Qiu 한국물리학회 2010 Current Applied Physics Vol.10 No.1
The moisture in the substrate material may have a potential influence on atmospheric pressure plasma treatment. In order to investigate how the existence of moisture affects atmospheric pressure plasma treatment, polyamide 6 (PA6) films were treated by helium, helium/oxygen (O2) plasmas using atmospheric pressure plasma jet (APPJ) at different moisture regain. The film surfaces were investigated using contact-angle measurements, atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) to characterize the surfaces. The exposure of PA6 film surfaces to the plasmas led to the etching process on the surfaces and changes in the topography of the surfaces. It was shown that the etching rate and the surface roughness were higher for the 9.33% moisture regain (relative humidity 100%) group than that of the 1.61% moisture regain (relative humidity 10%) group with the same plasma gas and power.