Modeling of the Degradation of Elastic Properties due to the Evolution of Ductile Damage

A new conical splay test is developed to assess the mechanisms of damage evolution in a range of stress states representative of hot rolling. The test consists of a bulk forming operation between open dies, during which plastic deformation occurs across a gradient of stress states from near-uniaxial tension to highly compressive. The transition between tensile and compressive stress state allows the microstructure to be accurately linked to the corresponding stress state. FE simulation of the new test is used to analyze the stress-state history during deformation. A low-carbon free-cutting steel, which is prone to edge cracking during hot rolling, is studied and the modes of damage evolution are discussed.

Section: Introductionmentioning

confidence: 99%

A Test for Evaluating the Effects of Stress-States on Damage Evolution with Specific Application to the Hot Rolling of Free-Cutting Steels

Foster

Lin

Farrugia³

et al. 2009

“…Al-Shayea et al (2003) quantified parameters for a plastic-damage model for the stress-strain behavior of two types of soils at maximum density only. There are growing inters in ductile damage mechanics and strain-softening phenomena, Wallin et al (2008) and Chow and Jie (2009).…”

Section: Literature Reviewmentioning

confidence: 99%

Parameters for an Elasto-Plasto-Damage Model for the Stress-Strain Behavior of Dense Sand

Al-Shayea

Mohib

2009

This article presents a constitutive model for dense sand that exhibits a post-peak strain-softening behavior. This model combines elements of plasticity with damage mechanics to simulate the stress—strain behavior. The post-peak stress drop is captured by the elasto-damage formulation, while the plasticity is superimposed beyond the elastic range. The total strain increment is composed of an elasto-damage strain increment and a plastic strain increment. The elasto-damage strain increment is found using the elasto-damage formulation, while the plastic strain increment is found using either the Drucker—Prager classical plasticity model or as a function of the damage strain. To calibrate this model, an experimental program was conducted on dense sand at different relative densities. The various physical and mechanical properties of the sand were determined. Both triaxial compression tests and hydrostatic tests were performed under different confining pressures, in order to obtain the model parameters at various conditions. These parameters were used to calibrate the model, which was coded in FORTRAN computer programs to simulate the stress—strain behavior of dense sand. The model was verified and found to be a good predictor of the response of dense sand for the selected stress path.

“…T HE RUPTURE OF heterogeneous material like concrete, rock, and other materials is always accompanied by the localization of deformation and damage in a narrow zone (Rudnicki and Rice, 1975;Scarpelli and Wood, 1982;Loret and Prevost, 1990;Labuz and Biolzi, 1991;Poirier et al, 1992;Harris et al, 1995;Tordesillas, 2004;Wallin et al, 2008;Chow and Jie, 2009;Van and Man, 2009). This implies that when eventual rupture occurs the scale governing the rupture is much smaller than the sample size.…”

Section: Introductionmentioning

confidence: 99%

Evolution of Localized Damage Zone in Heterogeneous Media

Hao

Xia

Fang

et al. 2010

Evolution of localized damage zone is a key to catastrophic rupture in heterogeneous materials. In the present article, the evolutions of strain fields of rock specimens are investigated experimentally. The observed evolution of fluctuations and autocorrelations of strain fields under uniaxial compression demonstrates that the localization of deformation always appears ahead of catastrophic rupture. In particular, the localization evolves pronouncedly with increasing deformation in the rock experiments. By means of the definition of the zone with high strain rate and likely damage localization, it is found that the size of the localized zone decreases from the sample size at peak load to an eventual value. Actually, the deformation field beyond peak load is bound to suffer bifurcation, namely an elastic unloading part and a continuing but localized damage part will co-exist in series in a specimen. To describe this continuous bifurcation and localization process observed in experiments, a model on continuum mechanics is developed. The model can explain why the decreasing width of localized zone can lead stable deformation to unstable, but it still has not provided the complete equations governing the evolution of the localized zone.