OS0410 Evaluation of Stress Triaxiality and Fracture Strain of Automotive Steel Sheet Using Digital Image Correlation

2016 ◽  
Vol 2016.22 (0) ◽  
pp. _OS0410-1_-_OS0410-2_
Author(s):  
Daichi KANAZAWA ◽  
Satoru YONEYAMA ◽  
Kuniharu USHIJIMA ◽  
Junya NAITO ◽  
Shota CHINZEI
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Steel Sheet ◽  
Fracture Strain ◽  
Stress Triaxiality ◽  
Image Correlation ◽  
Automotive Steel

scholarly journals On the Evaluation of Stress Triaxiality Fields in a Notched Titanium Alloy Sample Via Integrated Digital Image Correlation

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
Dominik Lindner ◽  
Florent Mathieu ◽  
François Hild ◽  
Olivier Allix ◽  
Cuong Ha Minh ◽  
...  
Keyword(s):  
Digital Image Correlation ◽  
Tensile Test ◽  
Digital Image ◽  
Speckle Pattern ◽  
Equivalent Plastic Strain ◽  
Stress Triaxiality ◽  
Numerical Procedure ◽  
Constitutive Law ◽  
Image Correlation ◽  
Alloy Sample

This paper presents a coupled experimental/numerical procedure to evaluate triaxiality fields. Such a type of analysis is applied to a tensile test on a thin notched sample made of Ti 6-4 alloy. The experimental data consist of digital images and corresponding load levels, and a commercial code (abaqus) is used in an integrated approach to digital image correlation (DIC). With the proposed procedure, samples with complex shapes can be analyzed independently without having to resort to other tests to calibrate the material parameters of a given constitutive law to evaluate triaxilities. The regularization involved in the integrated DIC (I-DIC) procedure allows the user to deal with experimental imperfections such as cracking of the paint and/or poor quality of the speckle pattern. For the studied material, different hardening postulates are tested up to a level of equivalent plastic strain about three times higher than those achievable in a tensile test on smooth samples. Different finite element (FE) discretizations and model hypotheses (i.e., 2D plane stress and 3D simulations) are compared.

A digital image correlation based methodology to characterize formability in tube forming

2019 ◽  
Vol 54 (2) ◽  
pp. 139-148 ◽  
Author(s):  
Valentino AM Cristino ◽  
Joao P Magrinho ◽  
Gabriel Centeno ◽  
Maria Beatriz Silva ◽  
Paulo AF Martins
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Effective Strain ◽  
Stress Triaxiality ◽  
Image Correlation ◽  
Ductile Damage ◽  
Tube Forming ◽  
Loading Paths ◽  
A New Technique ◽  
Force Displacement

This article describes a methodology to characterize the failure limits by necking and fracture, and to determine the critical value of ductile damage in tube forming. The methodology makes use of digital image correlation, thickness measurements and force–displacement evolutions to obtain the strain loading paths and the strain values at the onsets of failure by necking and fracture. The onset of failure by necking is determined by a new technique that combines the strain and force–displacement evolutions whereas the fracture strains at the cracked regions of the tubes are obtained by a similar technique utilized by the authors in sheet metal forming. Transformation of the strain loading paths from principal strain space into the space of effective strain versus stress-triaxiality allows determining the critical experimental value of ductile damage at the onset of failure by necking. The methodology is applied to tube expansion with circular, elliptical and square cross-section punches and results confirm its importance and helpfulness for researchers and engineers involved in the development and optimization of industrial tube forming processes.

Material characterization and damage assessment of an AA5352 aluminium alloy using digital image correlation

2019 ◽  
Vol 55 (1-2) ◽  
pp. 3-19 ◽  
Author(s):  
Behzad V Farahani ◽  
Rui Amaral ◽  
Paulo J Tavares ◽  
Pedro MGP Moreira ◽  
Abel dos Santos
Keyword(s):  
Mechanical Properties ◽  
Digital Image Correlation ◽  
Aluminium Alloy ◽  
Digital Image ◽  
Material Characterization ◽  
High Stress ◽  
Stress Triaxiality ◽  
Image Correlation ◽  
Displacement Response ◽  
Force Displacement

The emergence of reliable material characterization techniques in automotive and aeronautical industries, in particular sheet metal forming, promises to underpin a novel advance in materials research. In this regard, 5xxx series aluminium alloys deliver the largest formability range and can be deformed at room temperature. This study aims at determining the mechanical properties of the AA5352 aluminium alloy, using digital image correlation. Thus, tensile sheet specimens manufactured from the corresponding alloy are mechanically tested under a uniaxial condition and deformation fields are monitored. Considering the force/displacement response and stress/strain curves, the material Poisson’s ratio, Young’s modulus and anisotropy coefficient in the transverse direction are characterized by the experimental digital image correlation data. It intends to obtain accurate and reliable mechanical properties to be considered in the future processing analyses. Numerically, adopting the experimentally obtained material properties, the Gurson–Tvergaard–Needleman damage model is implemented using finite element method formulation to forecast the ductile fracture performance of the tested AA5352 sheet. The predicted results are then compared with the experimental digital image correlation solution verifying good agreement with the force/displacement response and the deformation fields. Overall, the acquired numerical results imply that the Gurson–Tvergaard–Needleman damage criterion is capable to render an accurate prediction upon a high stress triaxiality state.

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