Relation between Ductile Fracture Locus and Deformation of Phases in Ti–6Al–4V Alloy

Abstract

Failure criteria based on ductility associated with triaxiality are often used to define the strength of metal alloys as a function of the load modalities. However a discussion of the results with regards to the microstructural evolution and the behavior of the different phases is still not investigated, especially in multi-phase alloys. In this paper a ductile failure criterion was calibrated on α/β titanium alloy (Ti-6Al-4V).The applied approach is based on different experimental tests supported by numerical analyses carried out by detailed FE models. Specimens were tested on a multiaxial test system to investigate the failure induced by different states of stress triaxiality. Results have been discussed with regards to the textures induced in the lattice of the α-phase and β-phase, which are a direct consequence of the rotations associated with the dissipative plastic strains. Schmid factors at failure have been also calculated to determine which slip system have been activated by the different load modalities. The proposed approach could be also extended to steel.

The second Sandia Fracture Challenge: predictions of ductile failure under quasi-static and moderate-rate dynamic loading

“…Some of the teams used published empirical data for the Ti-6Al-4V failure locus of failure strain as a function of stress triaxiality, also known as the "garland curve", e.g. Giglio et al (2013Giglio et al ( , 2012, to calibrate the dependence of the failure strain on triaxiality and Lode angle. Furthermore, the effect of orientation and rate dependence on this type of failure curve is not known and techniques to obtain such data are still to be developed.…”

“…Denoted "estimated" in forthcoming sections, it was employed to establish all blind predictions. The second is another failure locus given by Giglio et al (2013) for room-temperature Ti-6Al-4V under quasistatic loading. This locus was also reduced by 20 % to give a locus appropriate for dynamic loading.…”

“…Consequently, the R12 parameter was set to 0.88 to obtain the reduction of the yield stress by 12 % under shear. Additionally, the failure locus given by Giglio et al (2013) was used as it gave more realistic failure strains for low stress triaxialities. As was done for the blind prediction, the static failure locus was decreased by 20 % to give the dynamic locus.…”

Modeling and Evaluation of Damages in Bismuth-containing Stainless Steel Rolling

“…Therefore, the prediction and prevention of damage and fractures during material forming processes have always been a focal point of international research. [1][2][3][4][5] Scholars from different countries have carried out a significant amount of research on the micro mechanisms, fracture criteria, and process optimization related to damage and fracture in metal materials. [6][7][8][9][10][11] These studies involve various materials, different forming methods, diverse damage patterns, and distinct fracture criteria.…”

“…Some scholars have previously used fracture criteria to predict possible defects in sheet metal forming processes and cracks in workpiece during multi-pass stretching processes. 4,[12][13][14] Some scholars have conducted detailed research on the damage and fracture of rolled products in two-roll and three-roll spiral rolling processes 15,16) and proposed new fracture criteria based on the stress-strain conditions and microstructures during material rolling. These outstanding publications have broadened readers' perspectives and greatly contributed to deepening…”