Work Hardening of FCC and BCC Metals in Conical Flows in Metal Forming

1971 ◽  
Vol 38 (4) ◽  
pp. 1053-1056
Author(s):  
Nazeer Ahmed ◽  
P. S. Venkatesan ◽  
J. Waldman
Keyword(s):  
Work Hardening ◽  
Metal Forming ◽  
Conical Flows ◽  
Bcc Metals

Conical Flows in Metal Forming

1972 ◽  
Vol 94 (1) ◽  
pp. 213-222 ◽  
Author(s):  
N. Ahmed
Keyword(s):  
Work Hardening ◽  
Metal Forming ◽  
Plastic Material ◽  
Dead Zone ◽  
Equivalent Stress ◽  
Plastic Region ◽  
Maximum Pressure ◽  
Rigid Plastic ◽  
Hardening Material ◽  
Conical Flows

An improved velocity field based on the solution to an incompressible fluid flow is used to establish an upper bound approach for conical flows in metal forming. From a three parameter characterization of the equivalent stress-equivalent strain data on copper and aluminum, the effects of work hardening on forming stresses, maximum reduction ratios, optimum cone angles, and dead zone angles are studied for drawing, conventional, and hydrostatic extrusion. Results for a rigid-plastic material are obtained as a special case of the work hardening material. Experimental data are offered to show an excellent correlation with theory. A representation for the redundant work factor is developed that incorporates in it the effects of material properties and flow geometry. The existence of maximum pressure well inside the plastic region is pointed out and the possibility of introducing the forming fluid at some distance inside the die to facilitate better lubrication is examined.

scholarly journals Repulsion leads to coupled dislocation motion and extended work hardening in bcc metals

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
K. Srivastava ◽  
D. Weygand ◽  
D. Caillard ◽  
P. Gumbsch
Keyword(s):  
Work Hardening ◽  
Activation Barrier ◽  
Dislocation Motion ◽  
Dislocation Dynamics ◽  
Additional Contribution ◽  
High Symmetry ◽  
Screw Dislocations ◽  
Bcc Metals ◽  
Kink Pair ◽  
Extended Work

Abstract Work hardening in bcc single crystals at low homologous temperature shows a strong orientation-dependent hardening for high symmetry loading, which is not captured by classical dislocation density based models. We demonstrate here that the high activation barrier for screw dislocation glide motion in tungsten results in repulsive interactions between screw dislocations, and triggers dislocation motion at applied loading conditions where it is not expected. In situ transmission electron microscopy and atomistically informed discrete dislocation dynamics simulations confirm coupled dislocation motion and vanishing obstacle strength for repulsive screw dislocations, compatible with the kink pair mechanism of dislocation motion in the thermally activated (low temperature) regime. We implement this additional contribution to plastic strain in a modified crystal plasticity framework and show that it can explain the extended work hardening regime observed for [100] oriented tungsten single crystal. This may contribute to better understanding the increase in ductility of highly deformed bcc metals.

scholarly journals Modeling of Cross Work Hardening and Apparent Normality Loss after Biaxial–Shear Loading Path Change

Symmetry ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 142
Author(s):  
Yanfeng Yang ◽  
Cyrille Baudouin ◽  
Tudor Balan
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Work Hardening ◽  
Metal Forming ◽  
Material Model ◽  
Shear Loading ◽  
Loading Path ◽  
Forming Simulation ◽  
Apparent Loss ◽  
Specific Loading

The specific loading-path change during sheet metal forming may lead to some abnormal deformation phenomena. Two-stage orthogonal loading paths without elastic unloading have revealed a phenomenon of apparent loss of normality, further modeled in the literature by non-normality theories. In this paper, a particular orthogonal strain-path change is investigated using the Teodosiu–Hu hardening rule within an associated plasticity framework. The results indicate that cross work-hardening has a significant contribution to the apparent loss of normality and subsequent asymmetric yield surface evolution. Detailed contributions of the model’s ingredients and features are clarified. The developed material model is intended for sheet metal forming simulation applications.

scholarly journals Friction law in dry metal forming of materials with work hardening

2018 ◽  
Vol 15 ◽  
pp. 475-480 ◽  
Author(s):  
Zhigang Wang ◽  
Tatsuhiro Suzuki
Keyword(s):  
Work Hardening ◽  
Metal Forming ◽  
Friction Law

scholarly journals Repulsive coupled screw dislocation pairs cause work hardening in bcc metals

MRS Bulletin ◽  
2021 ◽  
Vol 46 (4) ◽  
pp. 297-297
Author(s):  
Judy Meiksin ◽  
Gopal Rao
Keyword(s):  
Screw Dislocation ◽  
Work Hardening ◽  
Bcc Metals

Tailored work hardening descriptions in simulation of sheet metal forming

2013 ◽  
Author(s):  
Henk Vegter ◽  
Hans. Mulder ◽  
Peter van Liempt ◽  
Jan Heijne
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Work Hardening ◽  
Metal Forming

Springback Analysis in Sheet Metal Forming of Non-linear Work-Hardening material Under Pure Bending

2016 ◽  
Vol 98 (2) ◽  
pp. 155-170 ◽  
Author(s):  
Radha Krishna Lal ◽  
Jai Prakash Dwivedi ◽  
Manish Kumar Bhagat ◽  
Virendra Pratap Singh
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Work Hardening ◽  
Metal Forming ◽  
Pure Bending ◽  
Hardening Material ◽  
Non Linear

Field-Ion Microscopy of BCC Metals: A Study of Image Differences and Topographical Variations

1973 ◽  
Vol 31 ◽  
pp. 114-115
Author(s):  
O. T. Inal ◽  
L. E. Murr
Keyword(s):  
Liquid Nitrogen ◽  
Liquid Nitrogen Temperature ◽  
Surface Atom ◽  
Image Brightness ◽  
Field Ion Microscopy ◽  
Topographic Features ◽  
Bcc Metals ◽  
Electron Orbital ◽  
Ion Microscopy ◽  
Field Ion Microscope

When sharp metal filaments of W, Fe, Nb or Ta are observed in the field-ion microscope (FIM), their appearance is differentiated primarily by variations in regional brightness. This regional brightness, particularly prominent at liquid nitrogen temperature has been attributed in the main to chemical specificity which manifests itself in a paricular array of surface-atom electron-orbital configurations.Recently, anomalous image brightness and streaks in both fcc and bee materials observed in the FIM have been shown to be the result of surface asperities and related topographic features which arise by the unsystematic etching of the emission-tip end forms.

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