共查询到20条相似文献,搜索用时 31 毫秒
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Hongsheng Liu Chengxi Lei Zhongwen Xing 《The International Journal of Advanced Manufacturing Technology》2013,69(1-4):211-223
The innovative hot stamping press of quenchable steel mainly includes two stages: hot forming of blank at elevated temperature and quenching of hot stamped part in closed water-cooled tools. Crucial stage in hot stamping process is quenching of hot formed part in water-cooled tool to achieve final high ultimate tensile strength. In quenching stage, cooling rate of hot stamped part has a significant effect on final mechanical properties of hot stamped part. Hence, in this paper, a new method is proposed to optimize cooling system to improve effectiveness of quenching and thus final mechanical properties of hot stamped part. In this method, cooling channel is introduced in tools, and hot stamping experiments are combined with corresponding finite element numerical simulations to optimize cooling system. According to cooling system optimization, two different sets of tools used to manufacture square-box-shaped part and B pillar of automobile are manufactured using drilling method and pre-embedding method, respectively. Hot stamping experiments and corresponding simulations are performed to verify the effectiveness of optimized cooling system. 相似文献
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Yong-Phil Jeon Hyung-Yoon Seo Jong-Deok Kim Chung-Gil Kang 《The International Journal of Advanced Manufacturing Technology》2013,67(5-8):1693-1700
The utilization of high-strength steel for automotive structural parts has increased since the oil crisis in the 1970s owing to its high strength and potential for weight reduction. Because of the limited formability of high-strength steels, automotive components are increasingly produced through hot press forming. In some instances, high-strength steel sheets are coated with an Al–Si layer in order to prevent scaling of components during hot press forming, and this can increase their reliability with a view to the dimensional accuracy and stress distribution when they are in service. In this contribution, the coating degradation mechanisms of Al–Si-coated boron steel after the hot bending process are reported. The issues related to coating degradation during hot press forming are critically reviewed at different positions on a part that was subject to hot bending. In addition, the hardness and friction coefficient were tested by a nano-indenter at various positions. The relationship between the experimental parameters and coating layer properties is also reported. It is concluded that the bending deformation affected the coating layer behavior the most. 相似文献
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J.F. Caseiro J.A. Oliveira A. Andrade-Campos 《International Journal of Mechanical Sciences》2011,53(9):720-733
In multiphase steels, heat treatments such as quenching are usually applied to achieve a desired metallurgical composition to attain the expected mechanical properties. In these processes, residual thermal stresses arise during the cooling of the material which may induce a permanent deformation leading to dimensional instability. This deformation can be increased by the existence of phase transformations in the steel which should not be overlooked.In the current work, the thermomechanical modelling of multiphase materials is discussed. Firstly, a multiphase thermo-elasto-plastic-viscoplastic model is presented and applied to simulate several quenching heat treatments in a high carbon steel. The model uses the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation to describe the diffusion transformation and the Koistinen-Marburger model to characterise the diffusionless martensitic transformation in non-isothermal kinetics. This allows the observation of the evolution of the different steel phases (austenite, ferrite, pearlite, bainite and martinsite) during the cooling process. However, it is not possible to determine the residual stresses that arise in the intersection of the different phases.In the second part, the model that considers generalised multiphase transformation being compared with a multiphase homogenisation model for the case of a dual-phase steel during cooling and subsequent forming. The homogenisation micro-model operates over a periodic Representative Unit-Cell (RUC), detailing the heterogeneous material distribution due to the different metal phases. Therefore, it is possible to determine the residual stress fields in the intersection of the different phases. On the other hand, this model does not allow to reproduce the transformation process from austenite during cooling. Continuous cooling processes are studied in both parts. Following the heat treatment, tensile and shear test curves are presented and compared with experimental results for the second part. 相似文献
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随着器件集成度的不断提高,电子设备机箱内板卡的热耗越来越大,不同板卡间热耗差异增大,对机箱的冷却设计提出了更高的要求.传统的冷却方式(如:常规风冷,常规液冷等)不能满足机箱新的冷却需求;若采用空调风冷则需要增大设备体积,不满足结构紧凑的要求.文中提出了利用热电制冷技术来解决此类机箱的冷却问题.通过仿真优化设计了一种一体化高效冷却机箱,并对机箱的冷却效果进行了实验验证.结果表明:该一体化高效冷却机箱满足结构和冷却需求,为未来的电子设备机箱冷却设计提供了一种新的思路. 相似文献
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基于DYNAFORM软件热冲压模块,研究了由B1500HS钢制成的某型轿车车门防撞梁热成形过程。通过引入H13模具钢热物性参数,并将相变潜热因素考虑在内,利用多步差分法得到了温度场单元体变分公式;依据车门防撞梁结构特征进行工艺分析,建立了车门防撞梁的两种热力相耦合模型。通过对比分析两种方案下整体及典型M形截面应力场、温度场和厚度分布结果发现:带压料板式方案所得产品热成形及淬火后应力场、温度场及厚度分布均匀,更适合热冲压成形。最后依据压料板式方案进行了成形试制,得到车门防撞梁的显微组织均为马氏体,底部与顶部的马氏体板条更为细小,维氏硬度超过450HV,符合热冲压零件性能标准。 相似文献
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Jun Zhao Shan-Ming Luo Feng-Qiang Li Chen-Bing Xu 《Journal of Mechanical Science and Technology》2017,31(7):3249-3254
Failure analysis shows that increased die temperature caused by severe plastic deformation of material and heat conduction between hot billet and cavity significantly affects the distortion of gear cavity in steel synchronizer ring forging process. The forging process of steel synchronizer ring and die temperature distribution under different forging conditions are analyzed through finite element method. Simulation results show that severe plastic deformation occurs in the gear cavity. The improvement of lubrication condition results in decreased die temperature. When the initial billet temperature is high, the die temperature is also high. Increasing forging speed in a certain range facilitates the die temperature decrease. The distribution of die temperature in synthetic forming technology is more reasonable than that of one step forging. The synthetic forming technology is adopted in production to reduce the effects of severe plastic deformation caused by die temperature. The ejection mechanism and control system of the double disc friction press are improved to reduce the contact time between the hot billet and cavity. Experimental results show that synthetic forming technology is reasonable, and that the die service life is prolonged. 相似文献
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《机械工程学报(英文版)》2019,32(3)
In order to control the ferrite and austenite percentage in duplex stainless steel welding, many researchers try to change the laser welding parameters and cooling medium, but ignore to study the influence of heat sink e ect on weld strength. In this work, the e ect of aluminium heat sink and varying cooling medium on the laser welding of duplex stainless steel(DSS) 2205 is studied. The 2 mm thick DSS sheets welded with pulsed Nd: YAG laser welding machine by varying the cooling medium(air and oil) and an aluminium plate used as a heat sink. The welded specimens tested for tensile strength, micro-hardness, distortion, microstructure and radiography analysis. The faster cooling rate in the oil quenching process enhances the ferrite percentage compared with air-cooled samples. But the faster cooling rate in oil quenching leads to more distortion and using aluminium as a heat sink influenced positively the distortion to a small extent. The lower cooling rate in air quenching leads to a higher tensile strength of the welded specimen. The objective of this work is to analyse experimentally the e ect of cooling medium and heat sink in the mechanical and metallurgical properties of laser welded duplex stainless steel. 相似文献
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Selection of tool materials and surface treatments for improved galling performance in sheet metal forming 总被引:1,自引:0,他引:1
Yingke Hou Weigang Zhang Zhongqi Yu Shuhui Li 《The International Journal of Advanced Manufacturing Technology》2009,43(9-10):1010-1017
Galling is a known failure mechanism in automotive stamping. It results in increased cost of die maintenance and scrap rate of products. In this study, rectangular pan and U-channel stamping experiments are used to (1) investigate the effect of stress states on galling performance in sheet metal forming, (2) select proper tool materials and surface treatments for improved galling properties, and (3) differentiate galling performances of bare and coated steel sheets. The results indicate that problems with galling are of major interest at the regions where sheet materials deform under the action of compressive stress. For the four investigated tool materials, Mo–Cr alloy cast iron shows the best galling performance. A combination of hardening, surface polishing, and Cr coating is suggested as the optimum tool treatment in the forming of bare high-strength steel. Hot-dip galvanized steel shows better galling behaviors than galvannealed and bare steel sheets. Galling performances of hot-dip galvanized and bare steels are improved with increased hardness of the forming tool. However, galvannealed steel results in severe galling when the hardness of the forming tool is very high. 相似文献
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Development of application technique of aluminum sandwich sheets for automotive hood 总被引:2,自引:0,他引:2
Kee Joo Kim Meung Ho Rhee Byung-Ik Choi Cheol-Woong Kim Chang-Won Sung Chang-Pyung Han Ki-Weon Kang Si-Tae Won 《International Journal of Precision Engineering and Manufacturing》2009,10(4):71-75
Objective of this study was to develop basic techniques in order to apply aluminum sandwich sheets for an automotive hood
part. The aluminum sandwich sheet is the material fabricated by adhering two aluminum skins to one polypropylene core. When
it has the same bending stiffness as a steel sheet, it is 65% lighter than the steel sheet and 30% lighter than an aluminum
alloy sheet. Therefore, it is notified exclusively as good substitutive materials for a steel body to improve the fuel efficiency.
Through aluminum sandwich sheet, however, it has relatively lower formability than that of the steel sheet for automotive
application. In this study, we developed application techniques of the aluminum sandwich sheet for automotive hood. The various
formability evaluations were carried out in order to secure the fundamental data for the measurement of sheet metal forming
and the establishment of optimum application conditions of the sandwich sheet. From these results, it was found that the sandwich
sheet could reduce the weight and maintain the flexural rigidity simultaneously comparing to the steel sheet. 相似文献
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提出一种新的思路解决热冲压过程的传热耦合模拟。板料和模具之间的界面传热系数借助圆柱形冲压试验数据并通过有限元优化反算的方法获得,将获得的界面传热系数(Interfacial heat transfer coefficient, IHTC)引入到ABAQUS的U形冲压模型中,进行单次热冲压模拟,得到一个冲压周期内模具表面任意节点的热流密度曲线。通过调用SAS程序求得模面任意节点对应的时均热流密度,将每个节点的时均热流密度和笛卡儿坐标系下的空间坐标对应关系引入到STAR-CCM+中作为模具淬火传热模拟的第二类边界条件。接着通过网格数据映射将稳态淬火模拟得到的模具温度场,水道壁表面传热系数(Film heat transfer coefficient, FHTC)和壁面冷却水温度重新导入到ABAQUS的冲压模型中进行新的热冲压模拟,此时的热冲压过程即同时实现板料-模具的界面传热和模具-水流的表面传热的稳态模拟。设计并制造仿真中使用的U形模具进行连续热冲压试验,采集特征点的稳态温度,与仿真结果进行对比。结果表明:耦合后的板料和模具的最大温度和未耦合的单次冲压相比升高近一倍,温度分布沿着水道进口向出口方向发生迁移。耦合后的板料和模具特征点温度与达到稳态的试验采集温度误差均小于10%。 相似文献
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Seong-Chan Heo Young-Ho Seo Tae-Wan Ku Beom-Soo Kang 《Journal of Mechanical Science and Technology》2011,25(2):429-439
Exhaust gas recirculation (EGR) cooler consists of a number of heat transfer tubes that have relatively larger net area than
that of flat type tubes. The surface of the tubes is made up with lots of grooves and protrusions for enlarging the net heat
transfer area. Most tubes are manufactured through forming processes, such as bending, spinning, roll forming, stamping and
so on. Therefore, a series of fracture or defect can occur during the various forming processes. In this study, the manufacturing
process of a dimple-type rectangular heat transfer tube used for an EGR cooler system is investigated based on the numerical
simulation and the experimental approach. A prototype of the tube is designed and modified to a newly designed tube considering
the conservation of the net heat transfer area based on the numerical and analytical approach. Formability evaluation of the
tube sheet is carried out by using forming limit curves based on the plastic instability conditions. Strain- and stress-based
forming limit curves are utilized to ensure the strain path independence. The newly designed tube having a number of dimples
on the both sides are manufactured by the press forming process. Thickness distributions for the principal cross-sections
are observed from both the simulation and the experiment and compared each other. From the results, it is confirmed that the
forming process is robust to manufacture the dimple type rectangular tubes with the comparison of thickness, and application
of the forming limit curves. 相似文献
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F. F. Li M. W. Fu J. P. Lin X. N. Wang 《The International Journal of Advanced Manufacturing Technology》2014,71(1-4):297-306
To reveal the effects of forming temperature and blank thickness on the formability of boron steel 22MnB5, which is represented by forming limit diagram, the hot forming limit experiments and B-pillar hot stamping simulations are conducted. Combined with air cooling test, the forming limit diagrams of boron steels with different blank thicknesses of 1.8, 1.6, and 1.4 mm and forming temperatures of 800, 700, and 600 °C are established. The relationships between the formability and the crystal structure of steel, the forming limit diagram, and the effect of blank thickness and forming temperature on the formability of boron steel are extensively investigated. A model for prediction of hot forming limit of 22MnB5 steel before the occurrence of phase transformation induced by cooling based on Oh's ductile fracture criterion and Logan–Hosford yield criterion is derived and verified by experiments. The research thus provides an in-depth understanding of the formability of 22MnB5 steel for its process determination and process parameter configuration in industries. 相似文献
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针对目前车用22MnB5高强钢和7075铝合金板料在连接工艺上存在的问题,提出一种高强钢和铝合金异种材料车身零件的热铆接冷模具淬火(Hot riveting quenching, HRQ)无铆钉铆接工艺,利用22MnB5在高温下良好的成形性及易淬性,实现对22MnB5高强钢与7075铝合金的有效连接。通过建立HRQ无铆钉铆接的成形和淬冷有限元模型,证明了该工艺的可行性,使铆接后接头的高强钢具有全马氏体组织,保证了接头的强度。并从仿真和试验两方面研究高强钢铆接温度对接头尺寸颈厚值Tn、自锁值Tu的影响,发现在600~800 ℃区间内,Tn和Tu均呈现先上升后下降的趋势,Tu受温度影响更显著,两者均在700 ℃时获得最大值,表明700 ℃是高强钢板料的最佳铆接初始温度。 相似文献