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薄板曲面微结构电流辅助滚压成形工艺研究 总被引:1,自引:0,他引:1
针对燃料电池等系统中的薄板曲面微结构制造,提出了薄板曲面微结构滚压成形工艺,并借助电流辅助成形技术,提高了薄板曲面微结构的成形质量。采用单向拉伸实验,研究了脉冲电源参数如电压、频率、脉宽等对T2紫铜薄板单向拉伸变形行为的影响;开展了薄板曲面微结构滚压变形有限元模拟,优化坯料结构,抑制了曲面微结构件的翘曲失稳;在此基础上,开展了电流辅助滚压成形实验。结果表明,脉冲电流在达到一定阈值时,流动应力显著降低,断裂应变明显提高;采用梯形板坯,可优化板料受力状态,抑制翘曲失稳;脉冲电流辅助滚压成形时,曲面微结构高度分散性变小,成形件一致性更好,微结构尺寸精度更高。 相似文献
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采用自制的热型连铸设备制备了直径为12 mm的单晶铜、单晶铝和单晶锌试样。采用SHIMADZU(岛津)AG-I250kN精密万能试验机拉伸试样;用XRD和SEM研究了单晶体的优先生长方向和拉伸试样断口的形貌及其形成机制。试验结果表明:单晶铜和单晶铝试样拉伸过程中发生了各向均匀的缩颈现象,试样拉断后断口呈双锥状,有明显的韧窝。但是单晶锌在拉伸过程中仅发生单向收缩,没有缩颈现象,其断口呈现典型的解理脆性开裂特征,解理面是(1012)晶面。 相似文献
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以黄铜薄板为研究对象,通过对不同厚度、不同宽度试样的单向拉伸,研究厚度和宽度变化对薄板单向拉伸过程应力和塑性性能的影响。实验结果表明,厚度变化对应力的影响十分显著。当厚度小于10倍左右内禀尺寸,薄板变形不均匀性加剧,不断增大的几何必需位错加强了薄板的硬化,流动应力随厚度的减小而增大,表现出明显的第Ⅱ类尺寸效应。但是当应变增大到0.013以后,几何必需位错所占比例不断减小,其对材料的硬化作用明显减弱。此外,随着厚度的减小,薄板的断裂机制由韧窝微孔聚集断裂转变为沿晶断裂,板料的塑性性能持续下降。拉伸试样宽度减小使流动应力略微下降,但对塑性性能影响不大。 相似文献
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通过采用在不锈钢冷轧薄板退火酸洗机组工艺段提取的SUS30 4冷轧不锈钢试样进行模拟试验 ,证明了张家港浦项不锈钢有限公司退火酸洗工艺条件合理 ,并得出了退火酸洗后的铁鳞损失量 相似文献
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In order to analyze the effect of viscous medium on the deformation behavior of sheet metals in viscous pressure bulging (VPB), the entire deformation process including instability and fracture was investigated real-timely by the aid of electronic speckle pattern interferometry (ESPI). Images of speckle patterns were captured continuously to obtain fringe patterns representing the full field strain rate. Values of strain rates were calculated based on the fringe patterns. The evolution of the weak region from the initial defect to the groove until crack was also observed through the fringe patterns. The onset of diffuse and localized necking were determined qualitatively and quantitatively. Experimental results show that the deformation of sheet metals in VPB passed through five states, namely, uniform deformation, strain localization, diffuse necking, localized necking and fracture. A defect emerged in strain localization. The growth of the defect caused the diffuse necking and generated a groove. The groove expanded mainly in length direction until the localized necking occurred. Finally the specimen fractured as a result of groove deepening. The tangential adhesive stress provided by viscous medium in VPB restricted the locally larger strain of the specimen. The diffuse necking was postponed greatly. Theoretical prediction of the limit strains of sheet metals in VPB would be made based on the experimental results in further work. 相似文献
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A uniform nickel (Ni) coating was bilaterally electrodeposited on the low-carbon steel substrate for the application of advanced
battery shells. Its forming limit was investigated by Hill localized necking theory coupled with finite element simulation
and scanning electron microscopy. The effective stress and effective strain in the Ni coating and steel substrate are deduced
using Hill’s anisotropic yield function. The localized necking condition is derived by sandwich sheet analysis, and the forming
limit strains are obtained by solving the nonlinear equation of the localized necking condition. Extensive calculations are
carried out using the proposed model. This study exhibits the nickel coating thickness and the normal anisotropic coefficients
of the coating and substrate have little influence on the forming limit curve (FLC) in the left region of the coated sheet,
but the strain hardening exponents of the coating and substrate have much effect on it. The calculated result matches well
with the measured data in uniaxial tension. This investigation is useful for the preparation of the electrodeposited Ni coating
and helpful for the forming operation of the battery shells. 相似文献
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《Journal of Materials Processing Technology》2014,214(5):1120-1130
Digital image correlation (DIC) analysis methods can provide very accurate strain measurement that is useful for identifying the onset of localized necking and thus determining the forming limit strains of sheet metals. Several different DIC procedures to establish a forming limit diagram (FLD) are compared including both position dependent and time dependent measurement methods where the latter is found to be more accurate for an Al–Mg–Si alloy. Since FLD standards are still being developed to include DIC methods, a new DIC-based time dependent measurement method for the forming limit strains is proposed in this research: (1) Surface topography is extracted from the DIC data and changes in surface height difference are obtained, of the test specimen; (2) The onset of localized necking is identified by the limit of stable flow of the surface height difference or the first derivative of the surface height difference near the development of a local neck when using the Marciniak test procedure. Compared to existing methods, this new procedure more accurately defines the onset of necking and the boundary of safe deformation of an FLD. 相似文献
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Woo-Jin Song Seong-Chan Heo Tae-Wan Ku Jeong Kim Beom-Soo Kang 《International Journal of Machine Tools and Manufacture》2010,50(9):753-764
The material properties for the analytical and numerical simulation in sheet metal processes, especially in tube hydroforming process, are generally obtained from the uniaxial tensile test of raw sheet material. However, the validation of the formability and reliability of the numerical simulation for the tube hydroforming process arises from the fact that the material characteristics of tubes are different from those of the raw sheet materials. In order to determine the most suitable material property of the tubular material for the evaluation of forming limit on the THF process, the uniaxial tensile test for the specimens of the raw sheet metal and the roll-formed tube and the free bulge test for the roll-formed tubular material are carried out in this paper. The forming limit curves are also derived using plastic instability based on three kinds of necking criteria, which are Hill’s local necking criterion for sheet and Swift’s diffuse necking criteria for sheet and tube, to describe and explain the forming limits for the roll-formed tubular material in the THF process. In order to acquire the informative data on the forming limit curves in the THF process, the loading condition of the free bulge test is controlled. The proper band from nearly necking initiation to nearly bursting initiation has been defined for the roll-formed tubular material in the THF process. It can be concluded that the flow stress of the tubular material should be determined from the actual free bulge test to find the practically valuable forming limit curve for the THF process. 相似文献
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L.M. Smith C. Wanintrudal W. Yang S. Jiang 《Journal of Materials Processing Technology》2009,209(8):3830-3839
A new experimental approach for determining the sheet metal flow stress curve for diffuse necking deformation through the hydraulic bulge expansion (HBE) test is introduced. For this approach, a flat sheet of metal is bulged under the load of hydraulic pressure within the confines of a rigid binder/die tool set of circular die opening. The hydraulic pressure and volume flow rate of the pressurized water entering the die cavity are recorded in real time. Operating under the assumption of thin-walled pressure vessel behavior, the real time data are used to compute the flow stress curve for the material type considered. The novel aspect of the proposed technique is the use of water volume measurement for determining the radius of curvature of the expanding dome. An example flow stress curve for 1.0 mm thick DDQ cold rolled sheet steel is shown to be in good agreement with the flow stress curve obtained through the standard uniaxial tension test. One key advantage of this proposed method is that the analyst may determine the diffuse necking portion of the flow stress curve without employing cumbersome techniques associated with uniaxial tensile test methods. Two disadvantages of the proposed method are the uncertainty associated with having to assume a yield surface, and the error associated with having to assume membrane behavior in the work piece. The introduction of this new method will increase researchers’ access to practical methods for obtaining sheet metal flow stress curves. 相似文献
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Surajit Kumar Paul Satish Roy S. Sivaprasad H. N. Bar S. Tarafder 《Journal of Materials Engineering and Performance》2018,27(11):5736-5743
The stress–strain behavior of sheet metal is commonly evaluated by tensile test. However, the true stress–strain curve is restricted up to uniform elongation of the material. Usually, after the uniform elongation of the material the true stress–strain is obtained by extrapolation. The present work demonstrates a procedure to find out the true tensile stress–strain curve of the steel sheet after necking using digital image correlation (DIC) technique. Hill’s normal anisotropic yield criteria and local strains measured by DIC technique are used to correct the local stress and strain states at the diffuse necked area. The proposed procedure is shown to successfully determine the true tensile stress–strain curve of ferritic and dual-phase steel sheets after necking/uniform elongation. 相似文献
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Gyu-Jin Oh Kye-Man Lee Moo-Young Huh Jin Eon Park Soo Ho Park Olaf Engler 《Metals and Materials International》2017,23(1):26-34
Three initial tensile specimens having different textures and, in consequence, different r-values were cut from a sheet of an interstitial-free steel. Using these specimens, the effect of r-value and texture on plastic deformation and the necking behavior were studied by tackling the strain state and texture during tensile tests. A reduced decrease in work hardening rate of tensile specimens with higher r-values led to a slower onset of diffuse necking which offers an increased uniform elongation. A slower reduction in thickness of specimens with a higher r-value provided a favorable resistance against onset of failure by localized necking. 相似文献
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Zhou Weixian Department of Aeronautical Manufacturing Engineering Northwestern Polytechnical University Xi′an 《中国有色金属学会会刊》1997,(1)
DEPENDENCEOFPREDICTIONMODELOFFORMINGLIMITSTRAINSONFORMINGMETHODANDMECHANICALPROPERTIESOFSHEETMETALS①ZhouWeixianDepartmentofAe... 相似文献