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.
Simulation Based Process Parameters Study of the Tube Roll-cutting
In the large-diameter tube product line, the tube roll-cutting induces the tube shrinkage. The dashing blade is vulnerable part in the cutting machine. To decrease the tube shrinkage and increase the blade working life, the cutting processes with various process parameters are simulated by using the FEM. This paper is concerned with the quantitative effect of process parameters on the tube rollcutting. The considered parameters are the initial feed speed and the maximum cutting force. A comparison between the numerical and experimental results proves the validity of simulation. The relationship between the tube shrinkage and the process parameters is obtained by studying the cut dimension. The result of the stress analysis shows the influence of process parameters on the stress value. The appropriate process parameters are recommended through comparison among the simulated results for cutting Φ76×3.5mm tube.
Development of a damage-based criterion for ductile fracture prediction in sheet metal forming
Abstract A second-order continuity tensor ψ is proposed to characterize the state of anisotropic damage in ductile sheet metal during a forming process. The continuity tensor can be determined from the effective elastic stiffness matrix and it satisfies the requirement of symmetry for derivation of the effective elastic stiffness matrix and it satisfies the requirement of symmetry for derivation of the effective stress tensor, the effective elastic strain tensor and the effective elastic stiffness tensor. The corresponding anisotropic damage constitutive relations are formulated to model the damage-failure process for sheet metal. Hence, the expressions of the specific damage energy release rate Y , taking into account damage anisotropy and stress triaxiality, have been derived by means of decomposing Y into a hydrostatic and a deviatoric part. The damage evolution equation is established in terms of a Lemaitre’s type plastic damage dissipation potential and plastic stress–strain relation. The minimum principal component of continuity ψ II is taken as the predominant factor governing the damage failure process. A damage-based criterion, which is a non-linear function of the equivalent plastic strain, the triaxiality factor and the continuity threshold, is finally derived for the prediction of fracture strains. An example of the biaxial stretching of steel sheet has been used to demonstrate how the criterion can be applied to predict the fracture limit. The results show that the predicted values are in agreement with experimental values.