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Title: Prediction of Ductile Failure in the Stretch-Forming of AA2024 Sheets

Abstract

A number of ductile failure criteria are nowadays being used to predict the formability of aluminium alloy sheets. Generally speaking, integral criteria (e.g. those proposed by Cockcroft and Latham, Brozzo et al., Oyane et al Chaouadi et al., etc.) have been probed to work well when the principal strains are of opposite sign, i.e. in the left side of the Forming Limit Diagram (FLD). However, when tensile biaxial strains are present, as occurs in stretch-forming practice, their predictions are usually very poor and even non-conservatives. As an alternative, local criteria, such as the classical Tresca's and Bressan and Williams' criteria, have demonstrated a good capability to predict the failure in some automotive aluminum alloys under stretching. The present work analyses experimentally and numerically the failure in AA2024-T3 sheets subjected to biaxial stretching. A series of out-of-plane stretching tests have been simulated using ABAQUS. The experimental and the numerical FLD for different failure criteria are compared. The influence on the failure of the hydrostatic pressure and the normal stress to the fracture plane is also discussed.

Authors:
; ;  [1]
  1. Departamento de Ingenieria Mecanica y de los Materiales, Escuela Superior de Ingenieros Industriales, Universidad de Sevilla, Camino de los Descubrimientos, s/n, 41092 - Sevilla (Spain)
Publication Date:
OSTI Identifier:
21057362
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 908; Journal Issue: 1; Conference: NUMIFORM '07: 9. international conference on numerical methods in industrial forming processes, Porto (Portugal), 17-21 Jun 2007; Other Information: DOI: 10.1063/1.2740801; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; A CODES; ALUMINIUM ALLOYS; COMPUTERIZED SIMULATION; DUCTILITY; FRACTURES; MATERIALS WORKING; NUMERICAL ANALYSIS; SHEETS; STRAINS; STRESSES; TESTING

Citation Formats

Vallellano, C., Guzman, C., and Garcia-Lomas, F. J. Prediction of Ductile Failure in the Stretch-Forming of AA2024 Sheets. United States: N. p., 2007. Web. doi:10.1063/1.2740801.
Vallellano, C., Guzman, C., & Garcia-Lomas, F. J. Prediction of Ductile Failure in the Stretch-Forming of AA2024 Sheets. United States. doi:10.1063/1.2740801.
Vallellano, C., Guzman, C., and Garcia-Lomas, F. J. Thu . "Prediction of Ductile Failure in the Stretch-Forming of AA2024 Sheets". United States. doi:10.1063/1.2740801.
@article{osti_21057362,
title = {Prediction of Ductile Failure in the Stretch-Forming of AA2024 Sheets},
author = {Vallellano, C. and Guzman, C. and Garcia-Lomas, F. J.},
abstractNote = {A number of ductile failure criteria are nowadays being used to predict the formability of aluminium alloy sheets. Generally speaking, integral criteria (e.g. those proposed by Cockcroft and Latham, Brozzo et al., Oyane et al Chaouadi et al., etc.) have been probed to work well when the principal strains are of opposite sign, i.e. in the left side of the Forming Limit Diagram (FLD). However, when tensile biaxial strains are present, as occurs in stretch-forming practice, their predictions are usually very poor and even non-conservatives. As an alternative, local criteria, such as the classical Tresca's and Bressan and Williams' criteria, have demonstrated a good capability to predict the failure in some automotive aluminum alloys under stretching. The present work analyses experimentally and numerically the failure in AA2024-T3 sheets subjected to biaxial stretching. A series of out-of-plane stretching tests have been simulated using ABAQUS. The experimental and the numerical FLD for different failure criteria are compared. The influence on the failure of the hydrostatic pressure and the normal stress to the fracture plane is also discussed.},
doi = {10.1063/1.2740801},
journal = {AIP Conference Proceedings},
number = 1,
volume = 908,
place = {United States},
year = {Thu May 17 00:00:00 EDT 2007},
month = {Thu May 17 00:00:00 EDT 2007}
}
  • The anisotropic mechanical properties of friction stir welded (FSW) AA2024-T3 alloy joints were investigated based on the uniaxial tensile tests. The joint microstructure was examined by using electron back-scattered diffraction and transmission electron microscope. Results show that the evident anisotropic failure and yielding are present in the FSW joints. With the increase of loading angle from 0° to 90° the ultimate tensile strength and elongation of the specimens consistently decrease, or at first decrease and then increase, depending on the FSW process parameters. The specimen cut from the weld direction, i.e. a loading angle of 0°, exhibits the highest strengthmore » and elongation. - Highlights: • Microstructure and anisotropy of friction stir welded joints were studied. • The evident anisotropic failure and yielding are present in joints. • The lowest yield stress and UTS are at 45° and 60° loadings, respectively. • Rotation speed heavily impact on the anisotropy of joints.« less
  • Two analytical approaches are detailed for the determination of Forming Limit Diagrams (F.L.D.) and compared with experimental results. The first one is the 'Enhanced Modified Maximum Force Criterion EMMFC' and the second one is the 'Through-Thickness Shear Instability Criterion TTSIC'. The criteria are both written in an intrinsic analytical form and are applicable to linear and non-linear given strain paths as it occurs in any FEM codes for sheet-metal forming simulation. Finally, the two methods are complementary depending on the nature of failure and the predicted curves are in reasonable agreement with the trend of experimental results for a widemore » range of materials.« less
  • The paper analyzes the dispersion of the mechanical parameters and its influence on the forming limit curves of sheet metals. The tests have been made for the case of the DC01 steel sheets. The dispersion of the mechanical parameters has been observed during the experimental research. On the basis of this dispersion, a forming limit band has been calculated using an alternate formulation of Hora's model (MMFC).
  • Initiation and propagation of cracks in monolithic and multi-layer aluminum alloys, called “Fusion”, is investigated. 2D plane strain finite element simulations are performed to model deformation due to bending and to predict failure. For this purpose, fracture strains are measured based on microscopic pictures of Nakajima specimens. In addition to, micro-structure of materials is taken into account by introducing a random grain distribution over the sheet thickness as well as a random distribution of the measured yield curve. It is shown that the performed experiments and the introduced FE-Model are appropriate methods to highlight the advantages of the Fusion material,more » especially for bending processes.« less
  • Manufacturing processes of aircraft, automobile and electronic components involve a lot of stretch-forming of sheet metals. The processes contain a large amount of straining which, in turn, may lead to plastic instabilities such as necking, slip formation or shear banding. Understanding the instability phenomenon requires the development of constitutive description of material characterizing the plastic instability and post uniform deformation behavior. The previous work on plastic instability usually lacks the experimental verification of the theoretical models. This may be owing to the complexity involved in designing a suitable experimental methodology for accurate measurements of strain in the locally deforming zonemore » as the deformation progresses rather rapidly once the local neck sets in. A review of the important methodologies and analyses that were and are used in investigating instability of sheet metal in uniaxial tension is presented in this paper. Some supporting results are also presented. 58 refs., 11 figs.« less