Papers by Keyword: Internal High Pressure Forming

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Authors: Ying Liu, Feng Xu, Bing De Wang
Abstract: nternal high pressure forming is a new technology producing hollow light components. Due to the process of internal high pressure forming is very complicated with many factors, the dissertation will focus on the use of plastic-elastic force theory to acquire the hydraulic pressure needed and the tubes wall thickness in the final forming fillet. Based on the assumption of volume's incompressibility condition, we analyze and calculate the stress and strain of the tubes wall. Finally we estimate the formula of the hydraulic pressure needed in the forming process. The whole work can offer a concise formula to engineer in the infancy of designing. And it also is the great theoretical support to the development of the internal high pressure forming.
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Authors: Bohuslav Mašek, Ivan Vorel, Hana Jirková, Petr Kurka
Abstract: All sectors of industry experience high demand for shaped products with as good mechanical properties as possible at low costs. Automotive industry, in addition, requires that the parts are of lightweight construction. Consequently, new types of materials and processes have to be combined to design new production chains capable to meet this demand. For instance, there are high-strength low-alloyed steels, whose final properties are attained by advanced heat treating techniques. One of such techniques is the Q&P process which can deliver excellent ultimate strengths exceeding 2000 MPa at a sufficient elongation level of 10 %. When combined with an unconventional forming method, it allows complex-shaped parts with outstanding mechanical properties to be made. One example of such combined procedure is the sequence of internal high pressure forming, hot stamping and Q&P processing. In the present study, thin-walled hollow stock was processed using such a combined procedure. After stepwise optimization of processing parameters, products with martensitic structure and a small amount of bainite were obtained. In all locations of the product which were tested, the ultimate strength exceeded 1950 MPa and elongation reached 15 %
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Authors: Gang Liu, Stephan Jäger, Klaus Siegert
Abstract: The paper researched formability ability of AZ31 Mg-alloy tube by hot pneumatic bulging. FEM simulations were carried out to reveal the effect of internal pressure changing on bulging process and forming limit. Several loading paths with different pressure changing were used in the simulations. From the research, the original expansion ratio of diameter using a bilinear loading path, namely the internal pressure was increased linearly, is only 22%, and bursting occurs quickly. With a step-like loading path, namely the internal pressure is increased step by step, among the steps, the pressure is kept constant, and the strain rate of bulging can be kept into a small range. Thus the deformation around the hoop direction is more even than the linear loading path, and than bursting can be postponed. During bulging, the inner pressure should be lowered with the increase of diameter to keep the strain rate in a small range around a constant value. Through optimization of loading path, the forming limit can be enhanced obviously so that the expansion ratio of diameter can be increased to 25.1%.
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Authors: Cong Han, Shi Jian Yuan, L.N. Sun
Abstract: In the past decade, hydroformed structural components have been widely used in industrial areas in North American and Europe and there is a large potential market in Asia with the development of automotive industry. An extraordinary feature of tube hydroforming is that a hollow component with a three dimension axis and variable closed-sections can be integrally formed, so that the number of component parts is minimized, weight is reduced and stiffness of the part is increased. The section shapes in many automotive hollow components are complex and it is usually difficult or impossible to hydroform these typical sections directly from circular section tube, so that satisfactory preforms are necessary. In this paper, a method to reduce the friction and calibration pressure through a petal-like cross-section shape preform is presented and its mechanism is analyzed. Preforms for rectangular, trapezoidal and polygonal sections used in hollow components are investigated and satisfactory preforms are obtained. Taking an engine cradle as example, satisfactory preform section shapes have been designed, by which the thickness distribution was controlled and the flash generated from the die-parting surface in the final forming was avoided. So a carefully selected preform process can contribute significantly to the reduction of friction and calibration pressure and it is a dominant factor for successful hydroforming.
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Authors: Wen Jing Yuan, Hao Bin Tian, Xiao Hang Liu, Xiao Song Wang, Shi Jian Yuan
Abstract: Firstly, the geometry condition of useful wrinkles during the hydroforming of double-cone tube was given. Then the stress condition of useful wrinkles was given by formula between the parameters of wrinkles shape at the end of axial feeding and internal pressure, hoop stress and axial stress. The analytical results were compared with the FEM analysis and experiments results. The results show that the useful wrinkles must meet both the geometry condition and the stress condition. The geometry condition of useful wrinkles is that the area of arbitrary length of wrinkles is a little smaller than the area of corresponding die cavity. The stress condition of useful wrinkles is that shape parameter G is not smaller than the radius R at the top of middle wrinkle. That means the increment of thickness strain dεt is positive and no thickness thinning will occur during the calibration. When the wrinkles didn’t match geometry condition, the dead wrinkles or bursting will take place. And when the wrinkles didn’t match stress condition, the bursting at top of middle wrinkle will occur during the calibration.
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Authors: Shi Gang Wang, Fu Sheng Gao, Feng Lan Cheng, Qiang Guo
Abstract: Internal high pressure forming is a kind of the modern plastic processing technology. Using liquid as the pressure transmitting medium, explore the effect of internal high pressure parameter on the three passing pipe technique, internal high pressure forming technique is applied on the three-dimensional shape parts deformation. In this study, we simulate the three-way pipe process by finite element software, analyze the forming force influence to the tube forming quality and get the changeable regulation of the pipe wall thickness with conclusion of the wall thickness variation, which provides the reference data and guidance for the actual production of the three-way pipe.
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Authors: Cheng Zhu Jin, Ge Zhan
Abstract: When filling liquid’s temperature is over 300 degrees centigrade, the internal high pressure forming process is easy to be decomposed and metamorphosed, therefore, as the pressure transmission medium, the important limited factor for the further development of the temperature state internal high pressure forming process is the heat-resistant limit. This paper analyzes the physical properties of the composite powder between micro silica and hexagonal boron nitride, and on the basis of it, discusses its pressure-transmitting properties under the static pressure condition. The researcher uses the pressing machine to force the press on different quality of the mixed powder in the different temperature, and measures the wall pressure distribution by using the high temperature resistant pressure sensor. The experimental results demonstrate that when the hexagonal boron nitride comes to 2 percents of the composite powder, the effect of the pressure transmission performance are the best, meanwhile it is not a significant factor for the temperature to influence the pressure transmission properties of the composite powder, and it will keep stable on the high temperature. In the 500 degrees centigrade, as the pressure transmission medium, the warm state internal high pressure forming research has been done through adding axial force and internal pressure to the 40Cr steel pipe fittings. The research results prove that the pressure transmission medium can not only overcome the traditional medium in high pressure forming filling liquid under high temperature, but also fully improve the plasticity deformation of metal workpieces. It helps to the bulging of complex, high hard metal pieces, and it is also helpful for simplified forming technology.
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