Effect of offset on the blade stress in tube roll-cutting process
The main objective of this study is to obtain the reasonable range of offset in tube roll-cutting process by analyzing the effect of the process kinematics. For this aim, the roll-cutting processes are simulated. Due to the existence of the offset, the relative feed speed of blade is not constant. In this paper, the relationship between the radial feed speed shock of a blade relative to the tube and the offset is introduced. The effects of offset on the roll-cutting force and the blade stress have been analyzed. Regarding the stress of the blade, the offset should be less than 0.15mm for Φ76×3.5mm tube with the blade radial displacement per cycle as 1.0 mm.
STUDY ON PNEUMATIC ROLL-CUTTING SHEARERFOR SMALL TUBES
In this article, the roll-cutting and grip forces are investigated by the cutting theory and the slip line theory. A new pneumatic roll-cutting shearer has been designed for small tubes.
Modeling of ductile fracture: Application of the mechanism-based concepts
Abstract This paper summarizes our recent studies on modeling ductile fracture in structural materials using the mechanism-based concepts. We describe two numerical approaches to model the material failure process by void growth and coalescence. In the first approach, voids are considered explicitly and modeled using refined finite elements. In order to predict crack initiation and propagation, a void coalescence criterion is established by conducting a series of systematic finite element analyses of the void-containing, representative material volume (RMV) subjected to different macroscopic stress states and expressed as a function of the stress triaxiality ratio and the Lode angle. The discrete void approach provides a straightforward way for studying the effects of microstructure on fracture toughness. In the second approach, the void-containing material is considered as a homogenized continuum governed by porous plasticity models. This makes it possible to simulate large amount of crack extension because only one element is needed for a representative material volume. As an example, a numerical approach is proposed to predict ductile crack growth in thin panels of a 2024-T3 aluminum alloy, where a modified Gologanu–Leblond–Devaux model [Gologanu, M., Leblond, J.B., Devaux, J., 1993. Approximate models for ductile metals containing nonspherical voids – Case of axisymmetric prolate ellipsoidal cavities. J. Mech. Phys. Solids 41, 1723–1754; Gologanu, M., Leblond, J.B., Devaux, J., 1994. Approximate models for ductile metals containing nonspherical voids – Case of axisymmetric oblate ellipsoidal cavities. J. Eng. Mater. Tech. 116, 290–297; Gologanu, M., Leblond, J.B., Perrin, G., Devaux, J., 1995. Recent extensions of Gurson’s model for porous ductile metals. In: Suquet, P. (Ed.) Continuum Micromechanics. Springer-Verlag, pp. 61–130] is used to describe the evolution of void shape and void volume fraction and the associated material softening, and the material failure criterion is calibrated using experimental data. The calibrated computational model successfully predicts crack extension in various fracture specimens, including the compact tension specimen, middle crack tension specimens, multi-site damage specimens and the pressurized cylindrical shell specimen.