Experiments on Damage and Failure Mechanisms in Ductile Metals at Different Loading Conditions
This paper deals with a phenomenological damage and failure model for ductile metals. The anisotropic continuum approach takes into account the effect of stress state on damage condition and damage rule corresponding to different mechanisms acting on the
- PDF / 821,680 Bytes
- 15 Pages / 439.37 x 666.142 pts Page_size
- 104 Downloads / 228 Views
Abstract This paper deals with a phenomenological damage and failure model for ductile metals. The anisotropic continuum approach takes into account the effect of stress state on damage condition and damage rule corresponding to different mechanisms acting on the micro-scale. Different branches of the criteria are formulated depending on stress intensity, stress triaxiality, and the Lode parameter. A new experimental program will be discussed in detail to validate the proposed continuum framework. Experiments with aluminum alloys are performed using a biaxial testing machine allowing individual loading of flat specimens in two directions. Loads are recorded during loading of the specimens and digital image correlation technique has been used to analyze the strain states in critical regions of the specimens. The biaxial experiments cover a wide range of stress states in shear-tension and shearcompression regimes. They will extend understanding of stress-state-dependent damage and failure mechanisms in ductile metals.
1 Introduction Damage and failure prediction is an important issue in analysis and design of metal forming processes. For example, it has been observed in many experiments with ductile metals that during loading or forming of material samples large, often localized inelastic deformations occur which may be accompanied by damage and failure processes acting on the micro-scale. In this context, theoretical models also taking into account negative stress triaxialities are of special interest since many industrial M. Brünig (B) · S. Gerke · M. Schmidt Institut für Mechanik und Statik, Universität der Bundeswehr München, 85577 Neubiberg, Germany e-mail: [email protected] S. Gerke e-mail: [email protected] M. Schmidt e-mail: [email protected] © Springer Science+Business Media Singapore 2016 K. Naumenko and M. Aßmus (eds.), Advanced Methods of Continuum Mechanics for Materials and Structures, Advanced Structured Materials 60, DOI 10.1007/978-981-10-0959-4_15
279
280
M. Brünig et al.
processes like rolling and forging involve compressive hydrostatic stress states. In these industrial processes, formation of damage and failure on the micro-level may then lead to macro-cracks and, thus, to final failure of structural elements. Many theoretical approaches are able to simulate in a phenomenological way growth and coalescence of micro-defects as well as corresponding macroscopic material softening under general loading conditions. They are based on internal scalar or tensorial damage variables whose increase is governed by evolution laws. Critical values of these damage variables may be seen as major parameters characterizing onset of fracture. Recent investigations have elucidated that damage and failure mechanisms depend on the stress state acting in a material point. For example, during tension loading conditions with high positive stress triaxialities damage is mainly caused by nucleation, growth and coalescence of micro-voids, whereas during shear and compression loadings with small positive o
Data Loading...
