An algorithm for localised and diffuse necking analysis

2007 ◽  
Vol 1 (4) ◽  
pp. 494 ◽  
Author(s):  
Juri Majak ◽  
Meelis Pohlak ◽  
Rein Kuttner
Keyword(s):  
Diffuse Necking

Biaxial Strength of HY 80 Steel

1985 ◽  
Vol 107 (2) ◽  
pp. 132-137 ◽  
Author(s):  
K. S. Chan ◽  
U. S. Lindholm ◽  
J. Wise
Keyword(s):  
Biaxial Tension ◽  
Strain Ratio ◽  
Thin Wall ◽  
Plastic Strain Ratio ◽  
Axial Tension ◽  
Diffuse Necking ◽  
Stress States ◽  
Von Mises ◽  
Tube Geometry ◽  
Good Agreement

The biaxial deformation behavior of HY 80 steel has been examined by testing thin wall tubes under combined axial tension and internal pressure. The effective stress-strain curves and the hardening response have been found to vary with the stress state. The plastic strain ratio at a given stress ratio deviates from the von Mises value except at the stress states near uniaxial tension, plane strain and equi-biaxial tension. Using Drucker theory, these deviations are eliminated and the resulting yield locus is in good agreement with both the Bishop-Hill theory and the experimental results. Influenced by the tube geometry, the instability strains at the onset of diffuse necking are decreased by an increase in hoop tension. The diffuse necking strains are reasonably predicted by the Swift and the Lankford-Saibel/Mellor criteria.

scholarly journals BIFURCATION ANALYSIS VERSUS MAXIMUM FORCE CRITERIA IN FORMABILITY LIMIT ASSESSMENT OF STRETCHED METAL SHEETS

2014 ◽  
Vol 06 (06) ◽  
pp. 1450064 ◽  
Author(s):  
F. ABED-MERAIM ◽  
R. H. J. PEERLINGS ◽  
M. G. D. GEERS
Keyword(s):  
Constitutive Models ◽  
Maximum Force ◽  
Present Contribution ◽  
General Applicability ◽  
Diffuse Necking ◽  
Hardening Modulus ◽  
Metal Sheets ◽  
Hardening Models ◽  
Elasto Plasticity ◽  
Necking Criterion

The present contribution deals with the prediction of diffuse necking in the context of forming and stretching of metal sheets. For this purpose, two approaches are investigated, namely bifurcation and the maximum force principle, with a systematic comparison of their respective ability to predict necking. While the bifurcation approach is of quite general applicability, some restrictions are shown for the application of maximum force conditions. Although the predictions of the two approaches are identical for particular loading paths and constitutive models, they are generally different, which is even the case for elasticity, confirming the distinct nature of the two concepts. Closed-form expressions of the critical stress and strain states are derived for both criteria in elasto-plasticity and rigid-plasticity for a variety of hardening models. The resulting useful formulas in rigid-plasticity are shown to also accurately represent the elasto-plastic critical states for small ratios of the hardening modulus with respect to Young's modulus. Finally, the well-known expression of Swift's diffuse necking criterion, whose foundations are attributed in the literature to the maximum force principle, is shown here to originate from the bifurcation approach instead, providing a sound justification for it.

A Consistent Criterion for Diffuse Necking in Sheet Metals Using Hill’s 1979 Yield Surface

1998 ◽  
Vol 120 (2) ◽  
pp. 177-182 ◽  
Author(s):  
S. K. Esche ◽  
R. Shivpuri
Keyword(s):  
Plastic Deformation ◽  
Yield Surface ◽  
Shape Factor ◽  
Biaxial Tension ◽  
Yield Function ◽  
Surface Shape ◽  
Principal Strain ◽  
Sheet Metals ◽  
Diffuse Necking ◽  
Anisotropic Yield Function

A review of some existing criteria for diffuse necking in sheet metals is given and their limitations are discussed. The introduction into production of new sheet materials whose plastic deformation is impossible to be modeled using Hill’s 1948 anisotropic yield function necessitates improvements of these existing criteria to accurately describe their necking behavior. In this paper, a generalization of the existing diffuse necking criteria for materials describable by Case IV of Hill’s 1979 anisotropic yield function is presented. The proposed criterion is consistent with the previous criteria. It predicts a significant effect of Hill’s 1979 yield surface shape factor on the critical principal strain in the range of negative minor strains while in the range of biaxial tension this influence is small.

scholarly journals On Complete Solutions for the Problem of Diffuse Necking in Sheet Metal

2017 ◽  
Vol 207 ◽  
pp. 2012-2017 ◽  
Author(s):  
S. Coppieters ◽  
J.-H. Kim ◽  
K. Denys ◽  
S. Cooreman ◽  
D. Debruyne
Keyword(s):  
Sheet Metal ◽  
Diffuse Necking ◽  
Complete Solutions

Assessing the formability of metallic sheets by means of localized and diffuse necking models

2016 ◽  
Author(s):  
Dan-Sorin Comşa ◽  
Lucian Lăzărescu ◽  
Dorel Banabic
Keyword(s):  
Diffuse Necking

scholarly journals Characterisation of Diffuse and Local Necking of Aluminium Alloy Sheets using DIC Technique

2019 ◽  
Vol 12 (3) ◽  
pp. 191-204 ◽  
Author(s):  
Szabolcs Szalai ◽  
Dóra Harangozó ◽  
Imre Czinege
Keyword(s):  
Aluminium Alloy ◽  
Strain Distribution ◽  
Tensile Tests ◽  
Time Dependent ◽  
New Method ◽  
Local Necking ◽  
Diffuse Necking ◽  
Dic Technique ◽  
Exact Description

This paper introduces a new method for the characterisation of the boundary of diffuse and local necking based on DIC measurements during tensile tests. A series of images illustrate the extension of diffuse necking and show the occurrence of local necking as well. The evaluation of strain distribution gives the exact description of processes using both time dependent and non-dependent methods.

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