Finite element study of stress and strain state during hot tube necking process

Abstract

Tube necking is a common process used for manufacturing pressure vessels, for example, compressed natural gas capsules, categorized under general spinning processes. An experimentally validated finite element model suited to the process is incorporated to study the deformation, and state of strain and stress in the contact zone. The in situ variation of stress and strain is illustrated via colored contour plots, and Cartesian and polar diagrams. It is shown that in some areas, there are similarities and differences between flow forming and tube necking; for example, like flow forming, the equivalent plastic strain decreases from the inner and outer layers toward the middle layer, and unlike flow forming, the axial strain at the outer layer is negative all around the tube while at the inner layer, axial strain possesses a maximum positive value at contact position. The state of stress and plastic strain in regions around the contact zone is shown at an instant of process duration, which is not quite similar to postprocess stress and strain distribution.

Research on the Integral Forming Process of Thin walled and Thick Mouth Seamless Gas Cylinders

“…The bending due to compressive strain along the axial direction in Zone and the axial extension in Zone together ampli ed the positive strain. Such ndings are consistent with the deformation pattern of Zoghi and Fallahi Arezoodar [7] in their research on neck spinning. The excessive elongation of the outer metal at the rim in Zone was caused by the unconstrained material at the rim of the bottle mouth, which is consistent with the behavior mentioned by Hamed et al [17] in their research on tube spinning.…”

“…6. In manufacturing certain pressure vessels using the tube spinning process, Zoghi and Fallahi Arezoodar [7] , highlighted the existence of thickening, thinning, elongation, compression, bending, and shearing in the deformation zone during the neck spinning process of the bottle mouth. To further investigate the strain state of the bottle mouth, the plastic strain distribution on each thickness layer in Fig.…”

“…By investigating the relationship between the microstructure and mechanical properties of gas cylinders, Li et al [6] improved the mechanical properties of gas cylinders based on the manufacturing process proposed by Jin et al [5] . Zoghi and Fallahi Arezoodar [7] manufactured pressure vessels using a necking spinning process, which essentially involved forming parts by applying the required force and displacement to the rotating blank by means of one or more forming rolls. Wang et al [8] claimed that a combination of stamping and deep drawing using steel plates could produce cylinder blanks as well as cups.…”

Optimization of Process Parameters during Flow Forming Process and its Verification

“…Kim et al [7] had analyzed the different roller angles using upper bound method and simulations. Zoghi et al [8] had done finite element analysis of hot tube necking process for 42CrMo steel. Xia et al [9] had done the analysis of flow forming for non axisymmetrical geometry.…”

Comparative Study of Forward and Backward Flow Forming Process using Finite Element Analysis

“…Zoghi et al [2] did finite element analysis of hot tube necking process for 42CrMo steel. The working temperature was set as 850° C. The study was concentrated for plastic strain and von-mises stresses and they were found that the equivalent plastic strain value is lower at the inner surface compared to top and middle surface.…”