作者：
Zhiwen Liu;Luoxing Li;Guan Wang;Jingran Chen;Jie Yi
期刊：
International Journal of Advanced Manufacturing Technology,2020年109(1-2):1-13 ISSN：0268-3768
通讯作者：
Liu, Z.
作者机构：
[Chen J.] School of Mechanical Engineering, University of South China, Hengyang, 421001, China;Cooperative Innovation Center for Nuclear Fuel Cycle Technology and Equipment, University of South China, Hengyang, 421001, China;[Yi J.; Luoxing Li] State Key Laboratory of Advanced Design and Manufacture for Vehicle Body, Hunan University, Changsha, 410082, China;[Wang G.] College of Mechanical Engineering, Ningxia University, Yinchuan, 750021, China;[Liu Z.] School of Mechanical Engineering, University of South China, Hengyang, 421001, China, Cooperative Innovation Center for Nuclear Fuel Cycle Technology and Equipment, University of South China, Hengyang, 421001, China
通讯机构：
[Liu, Z.] S;School of Mechanical Engineering, China
摘要：
The entrance shape of spread die plays a crucial role in the quality control of large-scale aluminum panel production. The conventional design of spread die is generally based on the experience and expertise of the die designers or costly plant trials. Thus, it is difficult to guarantee the material flow through subsequent feeder die with the same velocity and ensure the die strength. In this work, the extrusion processes of three spread dies with different entrance shapes used generally in the real extrusion production for large-scale aluminum panel were investigated by FE simulations. Firstly, 3D-FE models for simulating the extrusion processes of the three spread dies were established by using HyperXtrude software based on ALE algorithm. Then, the effects of different die designs on the material flow behavior, extrusion load, temperature, residual stress distribution, and die deflection were synthetically studied by analyzing and comparing the simulated results. Finally, the optimal die was manufactured and corresponding extrusion experiment was carried out on a 2600-t extrusion press. The simulation and experimental results show that the die 2 with fan-shaped entrance was the optimum one among the three spread dies, where the minimum required extrusion load, uniform flow velocity at the die exit, minimum residual stress in extruded profile, and minimum die deflection were obtained. This study could provide effective guidance on the entrance shape design of spread extrusion die for the large-scale aluminum panel.
摘要：
Frequency response and their sensitivities analysis are of fundamental importance. Due to the fact that the mode truncation errors of frequency response functions (FRFs) are introduced for two times, the errors of frequency response sensitivities may be larger than other dynamic analysis. Many modal correction approaches (such as modal acceleration methods, dynamic correction methods, force derivation methods and accurate modal superposition methods) have been presented to eliminate the modal-truncation error. However, these approaches are just suitable to the case of un-damped or classically damped systems. The state-space equation based approaches can extend these approaches to non-classically damped systems, but it may be not only computationally expensive, but also lack physical insight provided by the superposition of the complex modes of the equation of motion with original space. This paper is aimed at dealing with the lower-higher-modal truncation problem of harmonic frequency response sensitivity of non-classically damped systems. Based on the Neumann expansion and the frequency shifting technique, the contribution of the truncated lower and higher modes to the harmonic frequency response sensitivity is explicitly expressed only by the available middle modes and system matrices. An extended hybrid expansion method (EHEM) is then proposed by expressing harmonic frequency response sensitivity as the explicit expression of the middle modes and system matrices. The EHEM maintains original-space without having to involve the state-space equation of motion such that it is efficient in computational effort and storage capacity. Finally, a rail specimen is used to illustrate the effectiveness of the proposed method. (C) 2016 Elsevier Ltd. All rights reserved.
摘要：
We report the fabrication of the 304 stainless steel by the laser rapid prototyping harmonized with high-frequency micro-forging and demonstrate that both microstructure and properties of the prepared samples can be enhanced significantly. Structurally, we find that the large regular dendritic microstructure can be broken into pieces and that the internal defects are to some extent eliminated. Moreover, grains are refined remarkably. As a consequence of such structural modification, mechanical properties are found to be enhanced considerably by demonstrating a much broader fluctuation in tensile strength, a marked increase in tensile and yielding strength, and a drastic enhancement in surface hardness by 76% after the micro-forging. Further calculations reveal that the defect region is shrunken substantially after micro-forging. Detailed analysis of fractures in the tensile samples provides convincing evidence that plastic properties can be improved as well by the micro-forging.
