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Numerical simulation and experimental study for rheo-forged component using direct and indirect die system

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Transactions of Nonferrous Metals Society of China 2010年第9期20卷 1799-1804页

作者： H.H.KIM C.g.kang Precision Manufacturing Systems Division Pusan National University School of Mechanical Engineering Pusan National University

Sand casting and die casting processes have been used widely for complex automotive products such as knuckle, arm, ***, a part fabricated by casting has limited strength due to manufacturing defects such as the dendrite structure, segregation and *** an attempt to offer a solution to these problems, forging has been used as an alternative ***, the forging process provides limited formability for complex shape ***-forging of metal offers not only superior mechanical strength but also requires significantly lower machine loads than solid forming *** order to produce semi-solid materials of the desired microstructure, a stirring process is applied during solidification of molten *** results of an A356 aluminum alloy sample, which are obtained by experiment and by simulation using DEFORM 3D, are present.

关键词： rheo-forging A356 alloy formability forming defects

grain Size Control of Semisolid A356 Alloy Manufactured by Electromagnetic Stirring

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Journal of Materials Science & Technology 2005年第2期21卷 219-225页

作者： P.K.Seo C.g.kang National Research Lab of Thixo-Rheo FormingSchool of Mechanical Engineering Pusan National University Pusan 609-735 KoreaNational Research Lab of Thixo-Rheo FormingSchool of Mechanical Engineering Pusan National University Pusan 609-735 Korea

To investigate the possibility of substituting the mechanical stirring system with electromagnetic stirring (EMS) system for aluminum rheo die-casting, the EMS under the different stirring cooling conditions was carried out. It was found that in the early period of solidification, the dendrite breakages led to a fine primary phase. When dendrites grew coarsely, the effect of ripening on grain size overwhelmed that of dendrite breakage. It was also found that the high cooling rate favored large nucleation rate, and led to a fine primary phase. But high cooling rate also made the growth rate of the dendrite arm, which prevented the dendrite arm from being sheared off. Therefore there were a suitable stirring time and suitable cooling rate to obtain the best rheo die-casting structure. Qualified semisolid A356 aluminum alloy was successfully manufactured with short time EMS.

关键词： Semisolid metal process Electromagnetic stirring Rheo die-casting grain size control

Computational Analysis of the Compressible Flow Driven by a Piston in a Ballistic Range

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Journal of Thermal Science 2007年第4期16卷 360-369页

作者： g.Rajesh R.Mishra H.g.kang H.D.Kim School of Mechanical Engineering Andong National University388Songcheon-DongAndong-760 749Korea

The ballistic range has long been employed in a variety of engineering fields such as high-velocity impact engineering, projectile aerodynamics and aeroballistics, since it can create an extremely high-pressure state in very short time. Since the operation of the ballistic range includes many complicated phenomena, each process should be understood in detail for the performance enhancement of the device. One of the main processes which have significant influence on the device performance is the compression process of the driver gas. Most of the studies available in this field hardly discuss this phenomenon in detail and thus lack a proper understanding of its effect on the whole system performance. In the present study, a computational analysis has been made to investigate the fluid dynamic aspects of the compression process in the pump tube of a ballistic range and to assess how it affects the performance of the ballistic range. The results obtained are validated with the available experimental data. In order to evaluate the system performance, several performance parameters are defined. Effect of a shock tube added in between the pump tube and launch tube on the performance of the ballistic range is also studied analytically. Performance of the ballistic range could be significantly improved by the proper selection of the pump tube and high-pressure tube parameters and the addition of the shock tube.

关键词： Ballistic range compressible flow piston shock tube chimera mesh

Dynamic Deformation of Frozen Soil at a High Strain Rate:Experiments and Damage-Coupled Constitutive Model

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Acta Mechanica Solida Sinica 2021年第6期34卷 895-910页

作者： Z.W.Zhu W.R.Tang g.Z.kang Applied Mechanics and Structural Safety Key Laboratory of Sichuan Province School of Mechanics and EngineeringSouthwest Jiaotong UniversityChengdu610036China Northwest institute of Eco-Environment and Resources State Key Laboratory of Frozen Soil EngineeringChinese Academy of SciencesLanzhou730000China

The dynamic compressive deformation of frozen soil was investigated by conducting the split-Hopkinson pressure bar(SHPB)experiments at three temperatures and different high strain rates,and the dynamic stress–strain responses and failure modes of the frozen soil were *** experimental results demonstrate that the frozen soil exhibits evident dependence on the strain rate and temperature under the dynamic loading *** dynamic compressive stress–strain curve of the frozen soil was divided into three parts:the linear,nonlinear rising,and strain softening *** nonlinear rising and strain softening parts were both caused by the damage attributed to the debonding between the ice particles and soil matrix,from which a rate-dependent damage evolution equation was ***,a damage-coupled dynamic viscoelastic constitutive model of frozen soil at high strain rate was derived.A comparison between the theoretically predicted results and the experimental ones showed that the developed dynamic viscoelastic model could well describe the dynamic mechanical behavior of frozen soil at high strain rate.

关键词： Frozen soil Dynamic compression High strain rate Damage Constitutive model

VISCO-PLASTIC CONSTITUTIVE MODEL FOR UNIAXIAL AND MULTIAXIAL RATCHETINg AT ELEVATED TEMPERATURES

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Acta Metallurgica Sinica(English Letters) 2004年第4期17卷 431-436页

作者： g.Z.kang Q.gao J.Zhang Dept. of Applied Mechanics and Engineering Southwest Jiaotong University Chengdu 610031 ChinaDept. of Applied Mechanics and Engineering Southwest Jiaotong University Chengdu 610031 ChinaDept. of Applied Mechanics and Engineering Southwest Jiaotong University Chengdu 610031 China

Based on the experimental results of the ratcheting for SS304 stainless steel, a new visco-plastic cyclic constitutive model was established to describe the uniaxial and multiaxial ratcheting of the material at room and elevated temperatures within the framework of unified visco-plasticity. In the model, the temperature dependence of the ratcheting was emphasized, and the dynamic strain aging occurred in the temperature range of 4 00-600℃ for the material was taken into account particularly. Finally, the prediction capability of the developed model was checked by comparing to the corresponding experimental results.

关键词： constitutive model ratcheting elevated temperature multiaxial loading

Effect of Injection Velocity on Structure Part Characteristic in AZ50 Die Casting Process with High Vacuum System

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Journal of Materials Science & Technology 2008年第1期24卷 75-79页

作者： S.M.Lee P.K.Seo C.g.kang Korea School of Mechanical Engineering Pusan National University Busan 609-735

When diecasting large and thin Mg alloy parts,material defects occur,which include porosity,nonuniform mechanical properties,irregular surfaces,and incomplete *** resolve these problems,it is necessary to have uniform injection velocities and temperatures as well as control the *** study investigated the feasibility of producing large and thin components using a die caster by attaching a high vacuum *** particular,the effects of injection velocity on surface quality and the mechanical properties of the products were ***,an injection velocity scheme and a die structure capable of casting in a vacuum were *** a result,it was found that the critical low injection velocity was 0.2 m/s to produce large thin Mg alloy structures having good mechanical properties.

关键词： Mg die casting Injection velocity Vacuum system

Effect of Injection Velocity on Structure Part Characteristic in A50 Die Casting Process with High Vacuum System

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Journal of Materials Science & Technology 2008年第1期24卷 75-79页

作者： S.M.Lee P.K.Seo C.g.kang School of Mechanical Engineering Pusan National University Busan 609-735 Korea

关键词： Mg die casting Injection velocity Vacuum system

THE STRAIN CYCLIC CHARACTERISTICS AND RATCHETINg OF U71Mn RAIL STEEL UNDER UNIAXIAL LOADINg

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Acta Metallurgica Sinica(English Letters) 2000年第3期13卷 893-900页

作者： g.Z. kang Q. gao, X.J.Yang and Y.F. Sun(Department of Applied Mechanics and Engineering, Southwest Jiaotong University, Chengdu 610031, China) Southwest Jiaotong Univ Chengdu China

An experimental study was carried out of the cyclic behavior of U71Mn rail steel subjected to uniaxial strain and stress. The effects of cyclic struin amplitude, mean struin,strain loading rate and their histories on the strain cyclic characteristics were *** the asymmetrical stress cycling, the effects of stress amplitude, mean stress,stress loading rate and their histories on the ratcheting were analyzed. The interaction between strain cycling and stress cycling was also discussed. It is shown that either the cyclic characteristics under strain cycling or the ratcheting under asymmetrical stress cycling depends not only on the cumnt loading state, but also on the previous loading history. Some significant results are obtained.

关键词： cyclic plasticity ratcheting U71Mn rail steel uniaxial loading

AN EXPERIMENTAL STUDY ON THE KINEMATIC HARDENINg RULES FOR NONPROPORTIONAL CYCLIC PLASTICITY

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Acta Metallurgica Sinica(English Letters) 1999年第6期12卷 0-0,0-0+0-0+0-0+0-0页

作者： Q. gao X.J. Yang and g.Z. kang(Department of Applied Mechanics and Engineering, Southwest Jiaotong University, Chengdu 610031 ,China )

An experimental investigation was cawted out of the cyclic saturated kinematic hardening of the solution treatment stainless steel 316L subjected to cyclic loading for seveml strain paths, such as uniaxial cycling, cireulan elliPtic, diamond, rectangular shapes. The evoluting tndectories of back stresses in deviatoric stress space were obtained, and the evolution of back stress mtes during cyclic saturuted loading was analyzed under the assumption that the yield sudece rudius at cyclic saturation is constant and the direction of plastic stmin rute coincides with the one of the out normal vector Of the yield sudece. Some significant results were obtained.

关键词： stainless steel 316L nonproportional cyclic plasticity kinematic hardening