Papers by Keyword: Thin-Walled Tube

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Authors: Jie Xu, He Yang, Heng Li
Abstract: A multi-objective optimization method for thin-walled tube NC bending is presented. Firstly, a half-symmetry 3D elastic-plastic FEM model is established based on the initial design values, applying the dynamic explicit code ABAQUS/Explicit. Secondly, virtual orthogonal arrays are designed to optimize friction coefficients, with minimizing the maximum wall-thinning ratio, the maximum cross section distortion ratio and the maximum height of wrinkling waves as the multi-objectives. Lastly, the mandrel radius is optimized by sequential quadratic programming with approximate regressive models fit from uniform design values in the allowed range. Application is put forward for Ф50×1×100 (tube outside diameter ×tube wall thickness × central line bending radius) and Ф100×1.5×200 aluminum alloy tube bending. It is proved that the forming quality has been improved by the method.
Authors: Lan Fang Jiang, Wei Ming Lin, Dong Hui Wen, Hong Liu, Cong Da Lu, Yun Qing Gu
Abstract: Thin-walled spatial bending tube can not only provide engineering design with higher flexibility and lighter structure, but also enhance the construction of space saving and aerodynamics improvement. Based on rotary draw bending technique, a new method for spatial consecutive bending with no straight line for thin-walled tube was put forward. Firstly, a new bionic elastic mandrel was developed by analyzing the structural characteristics of the squilla. It mainly consisted of bowl-shaped mandrel balls, an elastomer and a mandrel shank. The bowl-shaped mandrel balls, nested matching one another, generated a non-smooth surface which can provide continuous support for internal surface of the tube wall. It could also achieve small bending radius. The elastomer featured of certain bending stiffness and enough tensile strength. Secondly, a curved clamping die was advanced to clamp the spatial consecutive bending tube with no straight line effectively. Based on the shape of the bending tube after the former bending forming process, the curved clamping dies which can match the shape of the former bending tube were designed for the later bending. Lastly, bending experiments was performed. A thin-walled tube made of Q235 with two passes, one bending angle 90° and the other 180° was taken for example and the spatial consecutive bending tube with no straight line was successfully obtained. It is of significant importance in enriching the spatial bending tube technique and achieving the small bending radius.
Authors: Zi Qian Zhang, Yun Hui Yan, Hui Lin Yang
Abstract: As there was no precise theoretical model for predicting the stress of deformation zone while straightening thin-walled tube, some technological parameters depended mostly on the experience of workers and on the results of trials, therefore by means of the membrane shell theory the equilibrium differential equations of stress is obtained firstly, then we analyze the strain of deformation zone, finally lead to a new theoretical model for predicting the stress in the elastic and plastic zone. Subsequently the simulated experiments have been done, the results show that the theoretical calculations coincide well with the simulated results, the errors are within 1%of the calculations, it is testified that the model is correct and efficient for the thin-walled tube straightening.
Authors: Majid Elyasi, Amin Moradpour, Saharnaz Montazeri
Abstract: Thin-walled tubes have always considered as energy absorption systems by researchers. This paper presents a new technique for energy absorption system which is simpler than other designs in production. This novel model is a thin-walled tube with perforation. During manufacturing process, equal numbers of holes are created in rows and columns in order to increase the energy absorption ability. In this article two different workpieces with the same geometry, one with holes and the other one with grooves, are compared to validate the model in accordance with other presented ones. For this purpose, specimens were modeled in finite element software ABAQUS with the same conditions and the amount of energy absorption, the initial decay, and the weight ratio of energy absorption (SEA) were evaluated. Then results which obtained from simulation are compared with experimental ones. Results confirmed that specimens with perforation have better decay symmetry rather than ones with grooves. In addition, force absorption in workpieces with hole is as twice as ones with grooves. The amounts of absorbed energy and SEA in workpieces with perforation are 56% and 46% more than workpieces with grooves, respectively.
Authors: Gang Liu, Jun Yang Peng, Xiao Song Wang, Shi Qiang Zhu, Shi Jian Yuan
Abstract: Hydroforming processes of a Y-shaped stainless steel tube with d/t (ratio of diameter to thickness) of 183 is presented. FEM simulations were carried out for analyzing the stress states and thickness distribution in the workpieces during hydroforming of the Y-shaped tube. A two-step process with preform procedure is presented to improve the stress states in the protrusion and to avoid the severe thinning at the top of the protrusion. Through the two-step hydroforming, the wrinkling and cracking defects were all avoided and sound components were produced.
Authors: Kengo Hashimoto, Masataka Tokuda, Tadashi Inaba, Atsuhisa Shiode, Petr Šittner, Borut Bundara
Authors: Cheng Ming Huang, Jian Wei Liu, Yin Zhong Zhong, Min Jian Wu, Kai Ming Wang, Rong Qin Zhou
Abstract: In order to realize the objective of lightweight manufacturing, the forming methods of thin-walled tubes are studied in this paper. Liquid impact forming, a compound forming technique of thin-walled tube using stamping and hydroforming processes, is presented in order to reduce the forming difficulty and increase the forming efficiency. A simple experimental tooling, including stamping device and tube hydroforming apparatus is developed. Forming experiments of stamping and liquid impact forming processes in rectangular cross-section dies are performed for 304 stainless steel tubes. The results of experiments show that the liquid impact forming technology is feasible, and it will be widely applied in the future.
Authors: Yan Qiu Zhang, Shu Yong Jiang, Yu Feng Zheng, Li Hong Zhao
Abstract: Backward ball spinning is applied to manufacturing thin-walled tubular part with longitudinal inner ribs. Rigid-plastic finite element method (FEM) is used to simulate and analyze backward ball spinning of thin-walled tubular part with longitudinal inner ribs. The fields of stress and strain in the deformation zone of the spun part are obtained by means of FEM. Finite element simulation results show that the deformation zone of the spun part is caused to be in a three-dimensional compressive stress state. The deformation zone in the inner rib is under the tensile strain in the radial and axial direction, and the compressive strain in the tangential direction. The wall deformation zone beside the inner rib is under the compressive strain in the radial direction, and the tensile strain in the axial and tangential direction. The three spinning force components all increase with the increase of the stroke of the ball. Furthermore, of all the three spinning force components, the radial force component is greater than the other two force components, and the tangential force component is minimum.
Authors: František Lofaj, Vladimír Ivančo, Péter Pál Varga
Abstract: Room temperature fracture behavior of short thin walled translucent coarse-grained polycrystalline alumina (PCA) tubes was investigated under compression loading in radial direction using conventional mechanical tests combined with the finite element modelling (FEM). FEM indicated strongly inhomogeneous stress distribution with the maximum tangential tensile stresses in the centre of the inner surface of a tube and opposite to the line of loading. Another zone of tangential tensile stresses form on the outer surface of the tube and oriented perpendicularly to the loading direction. However, these tensile stresses are lower compared to those under contact lines. Radial stresses were negligible compared to tangential stresses which were concluded to control tube fracture. Fracture occurs in two steps: firstly along the loading lines under the lines of contacts and secondly in the direction perpendicular to loading. It results in four regular pieces along the lines with the highest tangential tensile stresses. The results were analysed using Weibull statistics and standard fractography methods. The characteristic strength of the PCA tubes was 186 MPa and the Weibull parameter m‘corr = 16.9 ± 0.5. High m values and the absence of the obvious fracture origins were attributed to homogeneous microstructure and well developed PCA technology.
Authors: Bao Xing Zhang, Bin Lin, Zhi Lin Han, Lei Zhang
Abstract: Optimization of the cutting parameters is one of the most important contents in diamond turning process of the thin-walled tube of high strength aluminum alloy. Cutting conditions have an influence on reducing the production time and deciding the quality of the final workpiece. This paper proposes an optimization technique based on genetic algorithms (GA) for the determination of the cutting parameters. As the experimental results show, it is very efficient that the proposed genetic algorithm-based procedure for solving this problem.
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