Material-induced anisotropic damage in DP600

Abstract

Plasticity-induced damage development in metals is anisotropic by nature. The anisotropy in damage is driven by two different phenomena: anisotropic deformation state i.e. load-induced anisotropic damage (LIAD) and anisotropic microstructure i.e. material-induced anisotropic damage (MIAD). The contribution of second-phase particles can be anisotropic in terms of shape as well as distribution. Most of the continuum anisotropic damage models mimic the phenomenon of LIAD only. Not much attention has been paid to MIAD. This work shows the existence of MIAD in a (pre-production) grade of dual-phase steel (DP600). The aim is to see the influence of MIAD on post-localization deformation behavior and final failure mode. The deformation in this material is almost isotropic up to localization but the post-localization deformation and final failure mode is different when loaded in 0 and 90 to rolling direction. Tensile specimens were deformed up to final failure. A few specimens were stopped just before the final failure. Scanning electron microscopic analysis was carried out to study martensite morphology and damage in these specimens. The martensite morphology showed anisotropy in shape and orientation in the undeformed specimens. Significant MIAD was observed in the deformed tensile specimens due to the anisotropic martensite morphology. MIAD explains direction-dependent post-localization deformation, final failure mode, and formability of this material. Lemaitre's anisotropic damage model is modified to account for MIAD in a phenomenological manner. The MIAD parameters were determined from tensile tests carried out in 0 , 45 , and 90 to the rolling direction.

An anisotropic damage model based on microstructure of boom–panel for the fatigue life prediction of structural components

“…(11), (13) and (14), and obtain the damage driving force by using Eq. (16), and then combine the results with Eqs (17) and (18). It is clear that the evolution rate of booms of NO.…”

“…It is clear that the evolution rate of booms of NO. 12,14,15,16,18,25,45 and panels of NO.1458, 1256 is 0. Assuming that the initial continuity extent of boom is φ b,0 and that of panel is φ p,0 , we can obtain the following:…”

“…15 However, the development of anisotropic damage has been confirmed experimentally even if the virgin material is isotropic. [16][17][18] And this revelation has prompted the development of anisotropic damage theories. [19][20][21][22] Generally, trying to describe the anisotropic damage of materials by means of continuum damage mechanics, one must define a tensorial damage variable.…”

Study on deformation-induced damage evolution for Inconel718 superalloy with the use of innovative single-specimen method

“…To obtain a credible result of strain measurement, we have to use a technique enabling measurement on big enough volume of a uniformly stressed material (Representative Volume Element). In most cases, such kind of a specimen is used also for damage investigations (Niazi et al, 2013;Ganjiani, 2013;Shen et al, 2014). To investigate the effect of permanent deformation (plastic strain) on the structure of the material, such kind of the specimen is usually deformed to reach a particular level of plastic strain in the entire gage part and then unloaded to perform structural analysis.…”

Robust optimization and tailoring scatter of forming processes

“…The volume fraction of the martensite distributed in the ferrite matrix plays a key role in controlling the mechanical properties. Additionally, it is known that DP steel often shows a banded martensite structure that is mostly concentrated at the centre of the sheet (Niazi et al, 2013). This depends on the cooling rate during hot rolling, the intercritical annealing temperatures, and the soaking time (Caballero et al, 2006).…”