薄壁双层管液压胀形规律的研究/Study of Deforming Rule in Hydraulic Bulging Process of Bimetal T

2018-05-03 16:44:31

hydraulic inner tube outer bimetal



薄壁双层管具有单一金属管所不具备的优越性能,在汽车、石油、化工、核工业、医疗、食品、航空航天等领域有着广泛的用途。液压胀形技术因其胀形力均匀,大小容易控制,在双层管的制造中应用越来越广泛。然而,由于内、外管层材料性能的差异,双层管液压胀形比单层管的液压胀形更为复杂。目前,对管材液压胀形的研究多集中于单层管。因此,薄壁双层管液压胀形规律的研究对材料加工工程学科发展及指导生产具有重要的理论意义与实用价值。
本文采用理论分析、数值模拟和试验相结合的方法,针对AISI304无缝不锈钢为外管、20号无缝钢为内管的管Ⅰ和20号无缝钢为外管、AISI304无缝不锈钢为内管的管Ⅱ这两种薄壁双层管的液压胀形规律进行了较系统的研究。在对双层管液压胀形特点理论分析的基础上,模拟研究了薄壁双层管在管端固定、管端自由和轴向压缩三种类型液压胀形过程中的胀形程度、内外管壁厚变化、内外管的材料轴向流动和内外管接触界面的结合状态等胀形规律,以及内、外管界面间摩擦系数对胀形的影响;探讨了内、外管层材料性能的差异及内、外管接触界面摩擦系数对双层管液压胀形规律的影响;通过试验验证数值模拟的可靠性。
对双层管液压胀形过程中胀形区内、外管层的应力应变状态进行了分析,获得了内、外管层界面间残余接触压力与胀形液压力之间的关系式;研究表明:相同的液压胀形条件下,内、外管材料的性能差异如应变硬化指数n、伸长率δ和弹性模量E值等对双层管液压胀形规律的影响较大;轴向压缩胀形能较好地消除内、外管材料轴向流动的差异;内、外管界面摩擦系数对双层管液压胀形结果有一定的影响;设计了一套管材液压胀形模具,试验研究了管端固定的双层管液压胀形规律,获得了内、外管界面结合紧密的双层管Ⅰ,并验证了数值模拟方法应用于双层管液压胀形技术研究中的可靠性和有效性。

The bimetal thin-walled tube has the high performance which the sole metal tube does not have, and it has been widespread used in the domain of automobile, petroleum, chemical industry, nuclear industry, medical service, food, aerospace field and so on. With the excellence of that its hydraulic force is equably and easy to control, the hydro forming technique is more and more widely applied to the manufacture of bimetal tube. However, because there are differences in the material parameters of the inner and outer tube, the hydraulic bulging process of bimetal tube is more complex than the sole metal tube’s, and at present, most of the research into hydraulic bulging of tube focus on the sole metal tube. So the study of the deformation rule in hydraulic bulging process of the bimetal thin-walled tube has important meaning to the development of subject and the manufacture practice.
With the method which theory analysis and numerical simulation are combined by experiment, the deformation rule in the process of two kinds of bimetal thin-walled tube which are tube I and tube II is researched systematically. Tube I are composed by the seamless stainless steel AISI304 as the outer tube and the seamless steel 20 as the inner tube, and tube II are composed by the seamless steel 20 as the outer tube and the seamless stainless steel AISI304 as the inner tube. Basing on the theory analysis to the hydraulic bulging characteristic of bimetal tube, the deformation rule in hydraulic bulging of bimetal thin-walled, such as the forming degree of tube shape, thickness change of inner and outer tube, axial material moving happened in the inner and outer tube, and the joint state of the interface between the inner and outer tube, as well as the influence to the hydro forming which caused by the friction coefficient between the outer and inner tube, are simulated in the three types of hydraulic forming with the tube ends fixed, free and axial compressed, so as to discuss the influence of the material parameters differences and the friction coefficient between the outer and inner tube to the deforming rule of the hydraulic bulging of bimetal tube. The reliability of the numerical simulation is validated by the experiment.
The stress and strain’s state of the inner and outer tube in the bulge region of bimetal tube in the hydraulic bulging process is researched by theory analysis, and the relation of the remnant contact pressure between the inner and outer tube and the hydro bulging pressure is obtained. It is revealed by simulated that in the same hydro bulge condition, the difference of the material parameters such as the strain hardening exponent(n value), elongation(δ value) and elasticity modulus(E value) of the inner and outer tube has a great influence on the deformation rule in the hydraulic of the bimetal tube. The difference of the axial material moving happened in the inner and outer tube can be eliminated well by the hydro bulge with the tube ends axial compressed. The friction coefficient between the inner and outer tube has some influence to the hydraulic bulging of the bimetal tube. A hydraulic bulging die used for the test is designed and the experiment is done to research the deforming rule in the hydraulic bulging of bimetal tube with the tube ends fixed. A tube I with tight joint interface between inner and outer tube is obtained, and the reliability and validity of applying the method of numerical simulation to the researching into the hydraulic bulging technology of the bimetal tube is approved by the experiment.