Definition of a unified material model for cellular materials with high morphological and topological dispersion: Application to an AA7075-T6 aluminium foam

Author(s):  
Edoardo Mancini ◽  
Francesca Campana ◽  
Daniela Pilone ◽  
Dario Amodio ◽  
Marco Sasso
1976 ◽  
Vol 98 (1) ◽  
pp. 133-138 ◽  
Author(s):  
I. V. Kragelsky ◽  
N. M. Alekseev

A scheme for estimating, in two stages, the seizure of friction pairs has been proposed. The first stage is the assessment of the extent of destruction of lubricant or other protective films. The second stage deals with plastic flow which occurs in surficial layers of the solid. For the second stage, the solid is assumed to be perfectly plastic with deformation hardening. This material model allows the definition of conditions at which plastic flow develops and damage of the surfaces occurs in the form of torn out wedges. Examples of such an estimate for seizure which considers both the properties of lubricant and protective surface films and mechanical properties of the surficial layer of material have been given. Comparison is made of the estimate and experimental data.


2021 ◽  
Author(s):  
Antonio Piccininni ◽  
Attilio Lattanzi ◽  
Marco Rossi ◽  
Gianfranco Palumbo

The continuous research for progressively lighter components moves the attention on the massive adoption of Al alloys. The achievement of such an ambitious goal passes through the definition of innovative manufacturing methodologies able to overcome some of the most hindering limitation of Al alloys, i.e. their poor formability at room temperature. A viable approach is based on the modification of the blank properties through a local heat treatment (to achieve an optimized spatial distribution of ductility/strength), so that the subsequent forming operation can be carried out at room temperature. The implementation of such approach relies on finite element simulations, where the use of a proper constitutive material model plays a fundamental role. In the present work an innovative methodology, already proposed by the authors in a previous research, is again adopted to enrich the characterization of a strain-hardenable Al alloy (AA5754), initially purchased in a pre-strained condition (H32), and locally annealed by means of a laser treatment: in particular, Thanks to the adoption of the DIC, the investigation of the anisotropy showed a strict correlation between the value of the Lankford parameter and the material condition reached at the end of the local treatment. The experimental data were fitted by a sigmoidal function and implemented in a modified Hill plasticity model for the simulation of the tensile test of a locally treated dogbone specimen, showing a good accordance with the experimental results.


Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1041 ◽  
Author(s):  
Varun Sharma ◽  
Nenad Grujovic ◽  
Fatima Zivic ◽  
Vukasin Slavkovic

We have studied an application of the Voronoi tessellation method in the modeling of open-cell aluminium foam under uniaxial compressive loading. The Voronoi code was merged with computer-aided design (CAD) for converting the polyhedral model into an irregular open-cell cellular structure to create porous samples for compression testing simulations. Numerical simulations of the uniaxial compression uniformly over the upper surface of the sample in the z-axis direction at a constant 20 N load was realised. Samples with three different porosities (30%, 60% and 80%) were studied. A nonlinear elasto-plastic material model with perfect plasticity, without hardening, based on the von Mises yield criterion was applied below 10% strain. Corresponding stress–strain curves were observed and the influence of porosity on deformation mechanism was discussed. Samples with higher porosity exhibited significantly higher normal stress under the same load, and increased stress plateaus. An increase of porosity produced an increase of both compressive and tensile stresses and struts exhibited complex stress fields. Voronoi-based modeling was in accordance with experimental results in the literature in the case of the quasi-static condition and linear elastic region (below 1% strain). Further study is necessary to enable the simulation of real dynamic behaviour under all deformation regimes by using the Voronoi tessellation method.


2017 ◽  
Vol 742 ◽  
pp. 740-744 ◽  
Author(s):  
Jörg Hohe ◽  
Monika Gall ◽  
Hannes Gauch ◽  
Sascha Fliegener ◽  
Zalkha Murni binti Abdul Hamid

Objective of the present study is the definition of a material model accounting for fatigue damage and degradation. The model is formulated as a brittle damage model in the otherwise linear elastic framework. A stress driven damage evolution equation is derived from microplasticity considerations. The model is implemented as a user-defined material model into a commercial finite element program. In a comparison with experimental data in the low cycle fatigue regime, a good agreement with the numerical prediction is obtained.


2022 ◽  
Author(s):  
Morgane Chapelier ◽  
Robin Bouclier ◽  
Jean-Charles Passieux

Abstract Identification from field measurements allows several parameters to be identified from a single test, provided that the measurements are sensitive enough to the parameters to be identified. To do this, authors use empirically defined geometries (with holes, notches...). The first attempts to optimize the specimen to maximize the sensitivity of the measurement are linked to a design space that is either very small (parametric optimization), which does not allow the exploration of very different designs, or, conversely, very large (topology optimization), which sometimes leads to designs that are not regular and cannot be manufactured. In this paper, we propose an intermediate approach based on a non-invasive CAD-inspired optimization strategy which relies on the definition of univariate spline Free-Form Deformation boxes to reduce the design space and thus regularize the problem. Then, from the modeling point of view, we propose a new objective function that takes into account the experimental setup and we add constraint functions that ensure that the gain is real and the shape physically sound. Several examples show that with this method and at low cost, one can significantly improve the identification of constitutive parameters without changing the experimental setup.


PAMM ◽  
2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Anne Jung ◽  
Thomas Bleistein ◽  
Stefan Diebels

2010 ◽  
Vol 659 ◽  
pp. 289-294
Author(s):  
Attila Bojtos ◽  
Antal Huba ◽  
Lena Zentner ◽  
Uwe Risto

For the simulations of elastic constructions actuated by inner pressure we need for the definition of the material model parameters, the data originating from the biaxial test. The paper reviews the biaxial material testing methods, especially the bubble inflation methods. It contains a short summary of the stress analysis of the rotation ellipsoid shells in association with the bubble inflation. The paper shows a developed equibiaxial inflating test using optical measurement method. Two different methods using image processing are showed. The test result of an examined silicone rubber (MED-4930) is presented with it’s material parameters.


2011 ◽  
Vol 31 (4) ◽  
pp. 182-192 ◽  
Author(s):  
J.A. García ◽  
A. Chiminelli ◽  
B. García ◽  
M. Lizaranzu ◽  
M.A. Jiménez

2008 ◽  
Vol 13-14 ◽  
pp. 85-90 ◽  
Author(s):  
Robert A.W. Mines ◽  
S. McKown ◽  
S. Tsopanos ◽  
E. Shen ◽  
Wesley J. Cantwell ◽  
...  

This paper discusses the penetration behavior of fully supported sandwich panels with micro-lattice and foam cores, and composite skins. This behaviour is of importance during foreign object impact and perforation of sandwich structures. Experimental results are given for quasi-static penetration of micro-lattice and foam blocks, and it is shown that these two cellular materials are comparable. Experimental results are also given for drop weight penetration of fully supported skinned panels, and it is shown that skin failure and core penetration are also similar for the two core materials. It is concluded that there is scope for improving the performance of micro-lattice structure and so making such material superior to that of aluminium foam.


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