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Modelling ductile damage is one of the most important applications of continuum damage mechanics (CDM) models. Scientists have previously tried to identify the damage parameters and have calibrated the failure behaviour of different materials using CDM models. However, more comprehensive studies are still needed to investigate the capabilities of CDM models for different materials. It is possible to extend the methodology to titanium alloys that are, currently, an optimal solution for highly stressed mechanical components. Therefore Lemaitre's CDM model parameters for ti-6Al-4V titanium alloy have been identified and reported in this work. A series of experimental tests have been carried out to identify the CDM model's parameters by the method of degradation of elastic modulus. A subroutine has been written in ABA-QUS to numerically simulate the behaviour of the simple specimen using Lemaitre's model. Keywords: Continuum damage mechanics / Ti-6Al-4V titanium alloy / ductile damage / numerical simulation / Die Modellierung duktiler Schädigung ist eine der wichtigsten Anwendungen der Kontinuums-Schädigungsmechanik (CDM). Forscher haben versucht die Schädigungsparameter verschiedener Materialien durch CDM zu identifizieren und somit die Versagensverhalten zu kalibrieren. Um die Fähigkeit von CDM in verschiedenen Materialien zu untersuchen, sind jedoch umfassende Studien erförderlich. Es ist möglich, diese Methode auch auf Titanlegierungen zu erstrecken, die sich heutzutage als eine optimale Lösung für anspruchsvolle mechanische Komponenten anbieten. Deshalb werden in dieser Arbeit auch die Lemaitre CDM-Parameter identifiziert und präsentiert. Um die CDM-Parameter (durch die Bestimmung der Abnahme des Elastizitätmodul) zu identifizieren, wurden eine Reihe von experimentellen Untersuchungen durchgeführt. Um das Verhalten durch ein einfaches Modell (Lemaitre) zu simulieren, wurde eine Unterprogramm in Abaqus geschrieben.

The widespread Von Mises plasticity model fails to take the hydrostatic and the Lode angle effects into account and the assumption of this model is not valid for all types of metallic alloys. Hence in the present work the applicability of the Von Mises plasticity model in applications on a Ti-6Al-4V Titanium alloy have been analysed. A virtual test methodology, combination of experiments and numerical analysis have been developed. For this purpose various tensile tests on different specimen shapes have been carried out experimentally. These tests have been subsequently numerically reproduced to calibrate a constitutive law which fits every single test best, highlighting the possible effect of triaxiality and Lode angle on plasticity (strain hardening behaviour). An analysis of the specimen fracture surfaces have been carried out to evaluate possible effect of triaxiality and Lode angle down to a microscopic level.

Different damage mechanics models have been proposed by researchers to calibrate the failure behavior of materials. Continuum damage mechanics (CDM) models are one of the main categories of damage models that can be exploited in numerical simulations. In this paper Lemaitres damage model, has been applied to finite element models of flat specimens. These models allow assessing the geometry transferability of the previously calibrated CDM model investigating in different geometry and loading conditions. Four different types of plane stress specimens have been designed to get different stress triaxialities which cover shear dominant and high triaxiality failure. Experimental tests were also done and the obtained data were critically compared with the results from numerical models. The tested material is Ti-6Al-4V titanium alloy which is a widely used material in aerospace industry because of its high strength and low density.