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Microstructure and impact behavior of Mg-4Al-5RE-xGd cast magnesium alloys

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Journal of Magnesium and Alloys 2024年第5期12卷 1799-1814页

作者： Jie Wei Qudong Wang Huisheng Cai Mahmoud Ebrahimi Chuan Lei national engineering research center of Light Alloy Net Forming and Key State Laboratory of Metal Matrix Composites School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China

This work investigated the microstructure and impact behavior of Mg-4Al-5RE-xGd(RE represents La-Ce mischmetal;x=0,0.2,0.7 wt.%)alloys cast by high-pressure die casting(HPDC),permanent mold casting(PMC),and sand casting(SC)*** results indicated that with increasing Gd content,the grain sizes of the HPDC alloy had a slight change,but the grains of the PMC and SC alloys were significantly ***,the acicular Al_(11)RE_(3)phase was modified into the short-rod shape under the three casting *** impact toughness of the studied alloy was mainly dominated by the absorbed energy during the crack *** increasing Gd content,the impact toughness of the studied alloy monotonically increased due to the lower tendency of the modified second phase toward crack *** impact stress was higher than the tensile stress,exhibiting a strain rate sensitivity for the mechanical response;however,the HPDC alloy had an inconsistent strain rate sensitivity during the impact event due to the transformation of the deformation mechanism from twinning to slip with increasing *** dimples covered the fracture surface of the fine-grained HPDC alloys,indicating a typical ductile ***,due to the deficient{1012}twinning activity and the suppressed grain boundary sliding during the impact event,the HPDC alloys showed insufficient plastic deformation capacity.

关键词： Mg-Al-RE alloy Gadolinium Microstructure Impact behavior

Analytical Solution of Thermo-Elastic-Plastic Deformation of the Combined Forging die

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Journal of Shanghai Jiaotong university(Science) 2023年第2期28卷 280-288页

作者：曹民业苗宏量胡成亮赵震 Institute of Forming Technology&Equipment School of Materials Science and EngineeringNational Engineering Research Center of Die and Mold CADShanghai Jiao Tong UniversityShanghai 200030China

On the multi-layer forging die used in daily life,stressed ring can strength the die structure within elastic deformation and the die material can be self-strengthened through uniform plastic deformation by autofrettage effect,whereas the thermal effect generated during forging process can directly influence the stress state and dimension of the forging die in *** this study,an analytical solution of the thermo-elastic-plastic deformation in the forging die is *** relationships between the radial and circumferential stresses and the temperature distribution,which are directly related to geometric parameters,material properties and working pressure,are *** helps to better understand the thermo-elastic-plastic deformation behavior of the die and design the combined forging die to achieve long service life and high accuracy product.

关键词： thermal deformation elastic deformation plastic deformation die temperature

New approach for modeling flow stress of aluminum alloy 6A10 considering temperature variation

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Transactions of Nonferrous Metals Society of China 2010年第8期20卷 1482-1487页

作者：李雪松伍来智陈军张鸿冰 national die and mold cad engineering research center Shanghai Jiao Tong University

The flow stress behavior of aluminum alloy 6A10 was studied by the hot compression tests at temperatures from 350°C to 550°C and strain rates from 0.1 s-1 to 10 s-1 with Gleeble-1500 thermo-mechanical *** result demonstrates that the temperatures of specimen differ from initial ones affected by deformation conditions,and that the softening mechanism is dynamic recovery.A new approach was proposed to analyze the flow stress character directly from actual stress,strain,temperature and strain rate data,without performing any previous flow stress correction caused by temperature *** between the experimental and predicted results confirm that the established flow stress model can give reasonable estimation,indicating that the mentioned approach can be used in flow stress model analysis of the materials that undergo only dynamic recovery based on the data obtained under variable deformation temperature.

关键词：温度变化流动应力铝合金建模流变应力应变率热模拟机变形条件

Forgeability of AZ31B magnesium alloy in warm forging

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中国有色金属学会会刊：英文版 2003年第3期13卷 632-635页

作者：张先宏阮雪榆 K.Osakada national die and mold cad engineering research center Division of Mechanical Science

To understand the forming behaviour of magnesium alloys, the upsetting test of Mg alloys at evaluated temperature was conducted. It is found that Mg alloys are brittle at temperatures below 200 ℃. When temperature is higher than 400 ℃, Mg alloy is not suitable for forging because of heavy oxidation. Mg alloy shows an excellent workability at temperatures from 250 to 400 ℃. Because in warm forging the flow stress decreases with increasing strain, which is so called work softening, no appropriate material formulation is available for Mg alloys. For the evaluation of flow stress of Mg alloys in warm forging processes, a formula is derived by analyzing the stress data measured at various temperatures in upsetting test. It is demonstrated that the formula fits the flow stress obtained from experiment.

关键词：镁合金可锻性锻造温锻动力学流动应力加工软化

Numerical simulation-driven optimization of sheet metal drawing part shape

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中国有色金属学会会刊：英文版 2003年第4期13卷 845-848页

作者：陈军石晓祥阮雪榆 national die and mold cad engineering research center engineering research center for Net Shape Manufacturing

Numerical simulation and perturbation method were coupled into the iteration process for optimizing the sheet metal part stamping quality, by minimizing the risk of rupture, wrinkle and unstretched area. The optimization of the sheet metal drawing part surface was realized by adjusting the FEM node/element perturbation vector directions and values. The sweeping simplex algorithm was modified to better control the optimization process, and one step simulation code was used to verify the new design formability. Finally, an autoauto fender drawing part shape optimization testified the proposed methods successfully.

关键词：薄板冲压数值模拟 FEM 优化塑性成型

Simulation of sheet metal extrusion processes with Arbitrary Lagrangian-Eulerian method

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中国有色金属学会会刊：英文版 2008年第5期18卷 1172-1176页

作者：庄新村赵震向华李从心 national engineering research center of die and mold cad Shanghai Jiao Tong University

An Arbitrary Lagrangian-Eulerian(ALE) method was employed to simulate the sheet metal extrusion process,aiming at avoiding mesh distortion and improving the computational *** method was implemented based on MSC/MARC by using a fractional step method,i.e.a Lagrangian step followed by an Euler *** Lagrangian step was a pure updated Lagrangian calculation and the Euler step was performed using mesh smoothing and remapping *** to the extreme distortion of deformation domain,it was almost impossible to complete the whole simulation with only one mesh ***,global remeshing combined with the ALE method was used in the simulation *** on the numerical model of the process,some deformation features of the sheet metal extrusion process,such as distribution of localized equivalent plastic strain,and shrinkage cavity,were ***,the differences between conventional extrusion and sheet metal extrusion process were also analyzed.

关键词：薄金属成型拉格朗日-欧拉方法挤压方法网孔滑度

DELAUNAY-BASED SURFACE RECONSTRUCTION ALGORITHM IN REVERSE engineering

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Chinese Journal of Mechanical engineering 2002年第3期15卷 238-242页

作者： Tian Xiaodong Zhou Xionghui Ruan Xueyunational die & Mould cad engineering research center, Shanghai Jiaotong University,Shanghai 200030, China Shanghai Jiaotong University National Die & Mold CAD Engineering Research Center 上海 200030 Shanghai Jiaotong University National Die & Mold CAD Engineering Research Center 北京 200030

Triangulation of scattered points is the first important section duringreverse engineering. New concepts of dynamic circle and closed point are put forward based oncurrent basic method. These new concepts can narrow the extent which triangulation process shouldseek through and optimize the triangles during producing them. Updating the searching edgesdynamically controls progress of triangulation. Intersection judgment between new triangle andproduced triangles is changed into intersection judgment between new triangle and searching *** illustrate superiorities of this new algorithm.

关键词： Reverse engineering Delaunay triangulation Dynamic circle Closed point

Theoretical study of void closure in nonlinear plastic materials

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Applied Mathematics and Mechanics(English Edition) 2009年第5期30卷 631-642页

作者：张效迅崔振山 national die and mold cad engineering research center Shanghai Jiao Tong University

Void closing from a spherical shape to a crack is investigated quantitatively in the present study. The constitutive relation of the Void-free matrix is assumed to obey the Norton power law. A representative volume element （RVE） which includes matrix and void is employed and a Rayleigh-Ritz procedure is developed to study the deformation-rates of a spherical void and a penny-shaped crack. Based on an approximate interpolation scheme, an analytical model for void closure in nonlinear plastic materials is established. It is found that the local plastic flows of the matrix material are the main mechanism of void deformation. It is also shown that the relative void volume during the deformation depends on the Norton exponent, on the far-field stress triaxiality, as well as on the far-field effective strain. The predictions of void closure using the present model are compared with the corresponding results in the literature, showing good agreement. The model for void closure provides a novel way for process design and optimization in terms of elimination of voids in billets because the model for void closure can easily be applied in the CAE analysis.

关键词： void closure RVE mesomechanics stress triaxiality CAE

Numerical Simulation of Microstructure Evolution for SA508-3 Steel during Inhomogeneous Hot Deformation Process

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Journal of Iron and Steel research(International) 2014年第11期21卷 1022-1029页

作者： Da-shan SUI Fei CHEN Pei-pei ZHANG Zhen-shan CUI national die & mold cad engineering research center Shanghai Jiao Tong University

Based on hot compression tests by a Gleeble-1500D thermo-mechanical simulator, the flow stress model and microstructure evolution model for SA508-3 steel were established through the classical theories on work hardening and softening. The developed models were integrated into 3D thermal-mechanical coupled rigid plastic finite element software DEFORM3D. The inhomogeneous hot deformation （IHD） experiments of SA508 3 steel were designed and carried out. Meanwhile, numerical simulation was implemented to investigate the effect of temperature, strain and strain rate on microstructure during IHD process through measuring grain sizes at given positions. The simulated grain sizes were basically in agreement with the experimental ones. The results of experiment and simulation demonstrated that temperature is the main factor for the initiation of dynamic recrystallization （DRX）, and higher temperature means lower critical strain so that DRX can be facilitated to obtain uniform fine microstructure.

关键词： SA508-3 steel inhomogeneous hot deformation microstructure evolution grain size numerical simulation