Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.39 No.453 October 1998)
Analysis of the Superplastic Deformation of a Ti-Alloy Tube
Nihat AKKUS, Ken-ichi MANABE, Masanori KAWAHARA and Hisashi NISHIMURA
(Received on November 5, 1997)
The deformation process of superplastic Ti-alloy tube into a spherical shape has been analytically simulated using axisymmetric membrane theory and incremental strain theory. A pressure algorithm, taking into account the differences in stresses and strains between the circumferential and meridional directions, was used to keep the strain rate approximately constant at the apex of the bulged tube with the assistance of an in-process bulging height measurement device. The Ti-alloy tube was used to form a spherical shell in the experiments at the temperature of 825℃. Tubes with a geometry of 30〓×1.8t×300Lmm were deformed to a final diameter of 150mm by maintaining the apex strain rate around 2〜3 × 10‐4 s‐1. The analytical model presented is able to predict some basic experimental variables such as process pressure, deformation time and thickness distribution prior to experimental tests. Experimental results were in good agreement with the theoretical predictions.
Key words : superplasticity, analytical simulation, tube bulging, spherical shell, in-process measurement
Effects of Base Profile on Can Bottom Performance
―― Study on Decreasing the Weight of Beverage DI Cans U ――
Hideki UTSUNOMIYA and Hisashi NISHIMURA
(Received on November 17, 1997)
Effects of DI (Drawn and Ironed) can base profile on can bottom performance such as dome reversal pressure, bottom growth and axial buckling load are experimentally investigated. The material used is 0.18mm thick steel with tensile strength in the rolling direction of 466 MPa. The factors studied in the base profile are base diameter, rim radius, dome shoulder radius, dome radius and dome depth. The dome reversal pressure is improved with decreased base diameter or increased dome depth. Bottom growth is improved by decreasing the rim radius, but a smaller rim radius means a thinner of rim inside wall, which in turn leads to the decrease of the dome reversal pressure, particularly for a large dome depth. Due to the fact that the rim inside wall moves toward the rim radius with bottom growth, the rim inside wall is a very important factor. A good correlation between the dome reversal pressure and the rim inside wall length is obtained.
Key words : sheet metal forming, design, DI can bottom profile, dome reversal pressure, bottom growth
Application of Corotational Elastoplastic Beam Element Analysis
to Wire-Rope Laying Process Simulation
Guilan WANG, Tatsuhiko AIZAWA, Junji KIHARA, Takuya MURAKAMI and Shinji KURASHIGE
(Received on December 26, 1997)
The three-dimensional corotational elastoplastic beam element analysis is applied to the wire-rope laying process simulation. Direct consideration of loading and unloading procedures in the actual operation enables us to describe the change in stress and strain states during the laying process. It is of great importance that the effects of the self-rotating ratio and tensile loading on the elastoplastic behavior can be quantitatively evaluated to optimize laying conditions. The laying process of a single wire is examined as a numerical example.
Key words : wire rope, laying process, simulation model, elastoplastic FEM, stress and strain analysis, self-rotating ratio
Numerical Analysis of Stretch-bending-unbending Process Based on
Elastic-plastic Incremental Strain Theory and Calculation of Residual Curvature
―― Springback Analysis of Sheet Metal V ――
Toshihiko KUWABARA, Norio SEKI and Susumu TAKAHASHI
(Received on January 29, 1998)
A rigorous numerical solution method for predicting the residual curvature of a metal sheet subjected to bending-unbending under tension has been established, based on an elastic-plastic incremental strain theory. The material is assumed to obey Hill's quadratic yield criterion and its associated flow rule. The Bauschinger effect is taken into account by adopting the combined hardening rule. In the solution procedure, the whole process of deformation is divided into five successive processes, i. e., initial stretching process, bending process, unbending process, unloading process, and springback process, and rigorous elastic-plastic incremental strain analysis is performed for each process. Two modes of deformation of a sheet are assumed in the calculations: (i) plane-strain condition (cal. I) and (ii) different deformation modes for each deformation process, taking into consideration the actual strain history observed in the bending-unbending experiment, described in the third report, for aluminum alloy sheets and cold-rolled steel sheets (cal. II). The cal. II results of residual curvature are in qualitative agreement with the experimental results, indicating the validity of the present analysis. However, the tendency that the calculated values of residual curvature are slightly larger than the experimental ones is still observed. For a more accurate prediction of the residual curvature, consideration of shearing deformation and the strain history dependence of the Bauschinger effect is necessary.
Key words : stretch-bending-unbending, elastic-plastic incremental strain analysis, residual curvature,
Bauschinger effect