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die design for cold precision forging of bevel gear based on finite element method

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Journal of Central South University 2009年第4期16卷 546-551页

作者：金俊松夏巨谌王新云胡国安刘华 State Key Laboratory of Material Process and die & Mould Technology Huazhong University of Science and Technology Metal Forming Division Zhengzhou Research Institute of Mechanical Engineering

The finite element analysis （FEA） software Ansys was employed to study the stress state of the dies of both plane and non-plane parting face structures with uniform interference and the die of plane parting face structure with non-uniform interference. Considering the symmetry of the die, a half gear tooth model of the two-ring assembled die with 2.5 GPa inner pressure was constructed. Four paths were defined to investigate the stress state at the bottom comer of the die where stress concentration was serious. FEA results show that the change of parting face from non-plane to plane can greatly reduce the stress at the teeth tips of the die so that the tip fracture is avoided. The interference structure of the die is the most important influencing factor for the stress concentration at the bottom comer. When non-uniform interference is adopted the first principal stress at the comer on the defined paths of the die is much lower than that with uniform interference. The bottom hole radius is another important influencing factor for the comer stress concentration. The first principal stress at the comer of the plane parting face die with non-uniform interference is reduced from 2.3 to 1.9 GPa when the hole radius increases from 12.5 to 16.0 mm. The optimization of the die structure increases the life of the die from 100 to 6 000 hits.

关键词： die gear precision forging finite element analysis optimized design

Reduction of die roll height in duplex gears through a sheet-bulk metal forming method

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Advances in Manufacturing 2019年第1期7卷 42-51页

作者： Xiao-Long Sun Xin-Cun Zhuang Feng-Chun Yang Zhen Zhao Institute of Forming Technology and Equipment School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai 200030 People's Republic of China National Engineering Research Center of die & Mold CAD Shanghai Jiao Tong University Shanghai 200030 People's Republic of China

In the existing shearing processes for fabricating parts such as duplex gears, die roll is difficult to avoid. Accordingly, a method based on sheet-bulk metal forming for fabricating a duplex gear with extremely small die roll in one stroke is proposed in the current work. The process could be divided into three stages according to the forming features: upsetting and shearing stage, lateral extrusion stage, and local filling stage. The die roll appeared in the shearing stage, which could be reduced in the subsequent extrusion and local filling stages. To reveal the underground mechanism, material flows under two situations, as a key factor to influence the forming quality, were compared and investigated. The results revealed that by controlling material flow, one could avoid the defects and reduce the die roll.

关键词： die roll Duplex gear part Sheet-bulk metal forming Lateral extrusion Material flow

Characterization of high-pressure die-cast hypereutectic Al-Si alloys based on microstructural distribution and fracture morphology

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Journal of Materials Science & Technology 2019年第6期35卷 1099-1107页

作者： X.Y. Jiao J. Wang C.F. Liu Z.P. Guo G.D. Tong S.L. Ma Y. Bi Y.F. Zhang S.M. Xiong School of Materials Science and Engineering Tsinghua University Beijing 100084 China State Key Laboratory of Automobile Safety and Energy Tsinghua University Beijing China China FAW Foundry Co. Ltd. Changchun 130011. China

The fracture behavior of high-pressure die-cast hypereutectic(HPDC) Al-Si alloys was investigated using a high-resolution laboratory CT and synchrotron X-ray tomography with a particular focus on the influence of HPDC microstructure. Results showed that microstructure of the alloy was mainly comprised of primary silicon particles(PSPs), Al dendrites, Cu-rich phases and pores. Most of the coarse PSPs, Cu-rich phases and pores were located in the center of the specimen. The rapid solidification of HPDC led to a heterogeneous microstructural feature. Elemental Cu was enriched in the frontiers of solid-liquid interface, causing the formation of large size dendritic arms. The pores were formed in the interdendrites which endured high stress intensity under high applied stress. Microcracks were originated from pores and further connected Cu-rich phases causing intergranular fracture. PSPs worked as obstacles causing piling-up dislocations in the phase interface. In the regions where large size of PSPs enriched in, PSPs ruptured rather than debonded from matrix, indicating transgranular fractures of PSPs. Microcracks originated around pores and PSPs tended to converge on the main cracks to decrease the energy required for crack propagation.

关键词： Hypereutectic Al-Si alloy Primary silicon particles Porosity Fracture morphology High pressure die casting

Heat shock behavior of permanent die during non-solid near-net forming process

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中国有色金属学会会刊：英文版 2009年第S3期19卷 795-801页

作者：张密兰单忠德邢书明姜超许应 State Key Laboratory of Advanced Forming Technologyand Equipment Advanced Manufacture Technology CenterChina Academy of Machinery Science and Technology School of Mechanical and Engineering University of Science and Technology Beijing State Key Laboratory of Advanced Forming Technology and Equipment Advanced Manufacture Technology CenterChina Academy of Machinery Science and Technology School of Mechanical Electronic and Control EngineeringBeijing Jiaotong University State Key Laboratory of Advanced Forming Technology and Equipment Advanced Manufacture Technology CenterChina Academy of Machinery Scienceand Technology

Heat shocks caused by alloy melt and coat spraying are the main reason of die plastic deformation and early fracture. Based on theoretical analysis of heat shock phenomenon, two characteristic parameters of die damage caused by heat shock were proposed, which are heat shock plastic deformation index (HSPI) and heat shock crack index (HSCI). The effect of heat shock on die plastic deformation and fracture behaviors was described quantitatively by these two parameters. HSPI represents approaching of heat shock stress to die yield stress. Plastic deformation will happen on a die if this index reaches 1. HSCI represents approaching of heat shock stress to die tensile strength. die fracture will happen if this index reaches 1. According to theoretical analysis of heat transfer, theoretical models of HSPI and HSCI were established. It is found that, the smaller the interfacial thermal resistance (ITR) is, the higher the pouring temperature and die temperature are before heat shock, and the greater the HSPI and HSCI are, which can be fitted as exponential curves, linear and cubic curves.

关键词： non-solid near-net forming die heat shock heat shock plastic deformation index heat shock crack index

Tempering stability of Fe–Cr–Mo–W–V hot forging die steels

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International Journal of Minerals,Metallurgy and Materials 2017年第10期24卷 1145-1157页

作者： Yuan-ji Shi Xiao-chun Wu Jun-wan Li Na Min School of Materials Science and Engineering Shanghai University Shanghai 200072 China

The tempering stability of three Fe–Cr–Mo–W–V hot forging die steels(DM, H21, and H13) was investigated through hardness measurements and transmission electron microscopy(TEM) observations. Both dilatometer tests and TEM observations revealed that DM steel has a higher tempering stability than H21 and H13 steels because of its substantial amount of M_2C(M represents metallic element) carbide precipitations. The activation energies of the M_2C carbide precipitation processes in DM, H21, and H13 steels are 236.4, 212.0, and 228.9 kJ/mol, respectively. Furthermore, the results indicated that vanadium atoms both increase the activation energy and affect the evolution of M_2C carbides, resulting in gradual dissolution rather than over-aging during tempering.

关键词： tempering stability hot forging die steels carbide precipitation

Influence of die geometry on self-piercing riveting of aluminum alloy AA6061-T6 to mild steel SPFC340 sheets

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Advances in Manufacturing 2019年第2期7卷 209-220页

作者： Jiang-Hua Deng Feng Lyu Ru-Ming Chen Zhi-Song Fan School of Mechanical Engineering and Automation Fuzhou University Fuzhou 350116 People's Republic of China

The self-piercing riveting (SPR) process was used to join 2.0-mm-thick aluminum alloy 6061-T6 and 1.2-mm-thick mild steel SPFC340 sheets. SPR joints produced with a conventional flat-bottom die and conicalsection dies were investigated both experimentally and numerically. Lap shear tests were conducted under quasistatic conditions to evaluate the load-carrying capability of these SPR joints. The effect of variation in die geometry (such as variation in the die groove shape, cone height, and die radius) on the main mechanical response of the joints, namely the peak load and energy absorption, was discussed. The results showed that SPR joints produced with the conical-section dies exhibited a failure mode similar to those produced with a conventional die. All the joints failed by tearing of the top steel sheet. Cracks that occurred in the bottom aluminum alloy 6061-T6 sheet around the rivet leg were a result of tangential tensile stress. The cone height of a conical-section die is the most important parameter affecting the surface quality of Al/steel SPR joints. Conical-section dies with a moderate convex can ensure a good surface quality during the SPR process. In addition, SPR joints with single conical-section die allow higher tensile strength and energy absorption compared to those with double conical-section die.

关键词： Self-piercing riveting (SPR) Aluminum/steel dissimilar sheet Conical-section die Lap shear test

Skin layer of A380 aluminium alloy die castings and its blistering during solution treatment

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Journal of Materials Science & Technology 2019年第9期35卷 1906-1916页

作者： Zihao Yuan Zhipeng Guo S.M.Xionga School of Materials Science and Engineering Tsinghua UniversityBeijing100084China State Key Laboratory of Automobile Safety and Energy Tsinghua UniversityBeijing100084China

Skin layer is a characteristic microstructure of aluminium die castings, which would effect the surface blistering during solution treatment. In this study, the microstructures of skin layer were investigated by the methods of optical microscope (OM), scanning electron microscope (SEM) and electron probe microanalyzer (EPMA). High resolution X-ray CT was used to compare the skin layer with normal surface before and after solution treatment. With the aid of computational fluid dynamics (CFD), the formation mechanism of the skin layer was discussed based on microstructure distribution, solute segregation, porosity distribution and surface blistering. The results suggested that the skin layer is related to a succession of complex processes before the filling process finished. Pore clusters or laminar defects would be formed in skin layers during solution treatm ent and cause severe surface blistering.

关键词： Skin layer die castings Solution treatment Blistering

Effect of Cu addition on microstructures and tensile properties of high-pressure die-casting Al-5.5Mg-0.7Mn alloy

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Journal of Materials Science & Technology 2019年第6期35卷 1017-1026页

作者： Lingyang Yuan Liming Peng Jingyu Han Baoliang Liu Yujuan Wu Juan Chen National Engineering Research Center of Light Alloy Net Forming and Key State Laboratory of Metal Matrix Composites School of Materials Science and Engineering Shanghai Jiaotong Univerisity Shanghai 200240 China Shanghai Light Alloy Net Forming National Engineering Research Center Co. Ltd. Shanghai 201615 China

In this study, Cu was added into the high-pressure die-casting Al-5.5 Mg-0.7 Mn(wt%) alloy to improve the tensile properties. The effects of Cu addition on the microstructures, mechanical properties of the Al-5.5 Mg-0.7 Mn alloys under both as-cast and T5 treatment conditions have been investigated. Additions of 0.5 wt%, 0.8 wt% and 1.5 wt% Cu can lead to the formation of irregular-shaped Al2 CuMg particles distributed along the grain boundaries in the as-cast alloys. Furthermore, the rest of Cu can dissolve into the matrixes. The lath-shaped Al2 CuMg precipitates with a size of 15–20 nm × 2–4 nm were generated in the T5-treated Al-5.5 Mg-0.7 Mn-x Cu(x = 0.5, 0.8, 1.5 wt%) alloys. The room temperature tensile and yield strengths of alloys increase with increasing the content of Cu. Increasing Cu content results in more Al2 CuMg phase formation along the grain boundaries, which causes more cracks during tensile deformation and lower ductility. Al-5.5 Mg-0.7 Mn-0.8 Cu alloy exhibits excellent comprehensive tensile properties under both as-cast and T5-treated conditions. The yield strength of 179 MPa, the ultimate tensile strength of 303 MPa and the elongation of 8.7% were achieved in the as-cast Al-5.5 Mg-0.7 Mn-0.8 Cu alloy, while the yield strength significantly was improved to 198 MPa after T5 treatment.

关键词： die casting Al-Mg alloys Cu addition Al2CuMg phase Tensile properties

THEORETICAL ANALYSES ON DESIGN OF SHEAR EXTRUSION die

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中国有色金属学会会刊：英文版 1997年第3期7卷 81-86页

作者： Yuan, Xi Central South Univ of Technology Changsha China

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关键词： shape extrusion die design element deformation analysis method