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
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.