Damage Identification for Anisotropic Sheet-Metals Using a Non-Local Damage Model

Abstract

A new damage model which takes account of void shape effect and anisotropy of the matrix material is integrated into the explicit finite element framework to predict the damage evolution which occurs under crash or stamping process. The void coalescence failure mechanism by internal necking is also considered by using a modified Thomason’s plastic limit-load model. An inverse method is developed to identify the material parameters by correlating experimental and numerical measurements with tensile tests on sheet-metal strips. The pathological mesh dependence has been overcome by a non-local approach where the evolution equation for the porosity is modified by an additional term containing a characteristic internal length. In this paper the evaluation of the Laplacian is based on a least square approximation of the internal state variable around each integration points. The presented formulation is applied to an Ni-based sheet-metal (INCO 718) and an aluminium alloy (AA 5182). The effectiveness of the numerical predictions is verified carrying out a set of experimental tests with a flat-headed punch.

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References

Bazant, Z.P. and Pijaudier-Cabot, G. (1988). Non-local Continuum Damage, Localization Instability and Convergence , J. Applied Mechanics, 55: 287-293 .

Benzerga, A.A., Besson, J. and Pineau, A., 1999, Coalescence-controlled Anisotropic Ductile Fracture , J. of Engineering Material and Technology, 121: 221-229 .

Brunet, M. and Morestin, F. (2001). Experimental and Analytical Necking Studies of Anisotropic Sheet-metals , J. of Material Processing Technology, 112: 214-226 .

Brunet, M., Morestin, F., and Godereaux, S. (2001). Non-linear Kinematic Hardening Identification for Anisotropic Sheet-Metals with Bending-Unbending Tests , J. of Engineering Material and Technology, 123: 378-384 .

Brunet, M., Morestin, F. and Walter, H. (2002). Failure Prediction in Anisotropic Sheet-metals Under Forming Operations using Damage Theory , Int. J. of Forming Processes, 5: 225-235 .

Chow, C.L., Yu, L.G. and Demeri, M.Y. (1997). A Unified Damage Approach for Predicting Forming Limit Diagrams , J. of Engineering Material and Technology, 119: 346-353 .

Gologanu, M., Leblond, J.B. and Devaux, J. (1997). Recent Extension of Gurson’s Model for Porous Ductile Metals, In: Suquet, P. (ed.), Continuum Micromechanics, pp. 61-130, Springer Verlag, Berlin .

Li, X. and Cescotto, S. (1996). Finite Element Method for Gradient Plasticity at Large Strains , Int. J. for Numerical Method in Engineering, 39: 619-633 .

Li, X. and Cescotto, S. (1997). A Mixed Element Method in Gradient Plasticity for Pressure Dependent Materials and Modelling of Strain Localization , Comp. Methods Appl. Mech. Engineering, 144: 287-305 .

10.

Ortiz, M. and Simo, J.C. (1986). An Analysis of a New Class of Integration Algorithms for Elasto-plastic Constitutive Relations , Int. J. for Numerical Method in Engineering, 23: 353-366 .

11.

Pardoen, T. and Hutchinson, J.W. (2000). An Extended Model for Void Growth and Coalescence , J. of Mechanics Physics of Solids, 48: 2467-2485 .

12.

Peerlings, R., Geers, M., R. de Borst and Brekelmans, W. (2001). A Critical Comparison of Non-local and Gradient Enhanced Softening Continua , Int. J. of Solids and Structures, 38: 7723-7746 .

13.

Saanouni, K., Chaboche, J.L. and Lesne, P.M. (1989). On the Creep Crack Growth Prediction by a Non-local Damage Formulation , European J. of Mechanic Solids, 8: 437-459 .

14.

Thomason, P.F. (1990). Ductile Fracture of Metals, Pergamon Press, London .