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Influence of Slope and Slenderness Ratio on the Non-Column Volume in Skew Rolling

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Journal of Materials Science & Technology 2003年第z1期19卷 192-194页

作者： Yongqiang KANG Zhenghuan HU Jinping LIU Cuiping YANG Huiping DU Mechanical Engineering School University of Science and Technology Beijing Beijing 100083 China Mechanical Engineering School University of Science and Technology Beijing Beijing 100083 China Mechanical Engineering School University of Science and Technology Beijing Beijing 100083 China Mechanical Engineering School University of Science and Technology Beijing Beijing 100083 China Mechanical Engineering School University of Science and Technology Beijing Beijing 100083 China

A definition of non-column volume ratio (NCVR) is brought forward by the authors. It is influenced greatly by the slendernessratio of the cylindrical billet and the slope of the wedge on the tool of skew rolling. Using the numerical simulation, the lawof variation in NCVR during the forming process is found out. At the same time experiments have been carried out underdifferent conditions, the result of which are found to be in good agreement with the theoretical predictions.

关键词： Skew rolling, fem, Non-column volume

3D Rigid-Plastic Finite Element Analysis for Skew Rolling Process of the Stepped Part

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Journal of Materials Science & Technology 2003年第z1期19卷 38-40页

作者： Gang FANG Pan ZENG Department of Mechanical Engineering Tsinghua University Beijing 100084 China Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Based on rigid-plastic finite element method, a skew rolling process of stepped part is simulated. Considering nodesaving and effective remeshing, the tetrahedron solid elements are used to discrete workpiece. The workpiece material adopts rigid-plastic model, where the flow stress is function of effective strain, effective strain rate and *** thermomechanical coupling is considered in the simulation. To model the spinning workpiece undergoing plastic deformation, a novel solution is presented and applied in this paper. The stress state in the workpiece and forming characteristic of skew rolling are analyzed. The forming load, including roller torque and forces in three directions are predicted. The above analyses are helpful to understanding of forming mechanisms and improving of process and die design.

关键词： fem, Skew rolling, Stepped part, Spinning part, Fracture

A New Ductile Fracture Criterion and Its Application to the Prediction of Forming Limit in Deep Drawing

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Journal of Materials Science & Technology 2003年第z1期19卷 217-219页

作者： Yuying YANG Zhongqi YU Xuechun LI Zhenzhong SUN School of Materials Sci. & Eng. Harbin Institute of Technology Harbin 150001 China School of Materials Sci. & Eng. Harbin Institute of Technology Harbin 150001 China School of Materials Sci. & Eng. Harbin Institute of Technology Harbin 150001 China School of Materials Sci. & Eng. Harbin Institute of Technology Harbin 150001 China

With considering the influence of equivalent plastic strain on void-damage and taking Lemaitre damage equivalent stress as plastic potential, based on continuous damage mechanics theory, a new criterion for ductile fracture is derived. The two key material constants in the criterion are determined by the combination of tension tests with FE (finite element) simulation. On the basis of the values of stress and strain calculated from commercial finite element software, the forming limit in cylindrical deep drawing of annealed aluminum alloy LY12(M) is predicted by means of the new ductile fracture criterion. Experiments verify that the predicted results are in agreement with the experimental ones. Hence, it is reliable to predict the forming limit in deep drawing by means of the new ductile fracture criterion.

关键词： Sheet metal forming, Ductile fracture criterion, fem, Forming limit

Numerical simulation of bistatic scattering from a target at low altitude above rough sea surface under an EM wave incidence at low grazing angle by using the finite element method

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Science China(Technological Sciences) 2004年第3期47卷 293-304页

作者： LIU Peng JIN Yaqiu The Key Laboratory of Wave Scattering and Remote Sensing Information Ministry of Education Fudan University Shanghai 200433 China The Key Laboratory of Wave Scattering and Remote Sensing Information Ministry of Education Fudan University Shanghai 200433 China

To study bistatic scattering from a target at low altitude above two- dimensional (2D) randomly rough sea surface under an electromagnetic (EM) wave incidence at low grazing angle (LGA), a numerical approach of the finite element method (fem) is developed. The conformal perfectly matched layer (PML), as the truncation boundary of the fem, is employed to reduce the reflection error of planar PML in conventional fem. Numerical code of our fem is examined by available solution of the forward backward iterative (FBM) method. Bistatic and back-scattering from composite model of a target above random rough sea surface generated by Monte Carlo realization, and functional dependence upon the sea surface wind speed, target altitude, incident and scattering angles, etc. are numerically simulated and discussed. This paper presents a numerical description of the observation principle and physical insight associated with the coupling interactions of a complex volumetric target and random rough sea surface.

关键词： rough surface, low altitude target, EM scattering, LGA, fem, PML.