Modeling of plasticity and fracture behavior of X65 steels: seam weld and seamless pipes

Abstract

A non-associated/associated flow rule coupled with an anisotropic/isotropic quadratic yield function is presented to describe the mechanical responses of two distinct X65 pipeline steels. The first as a product of the cold-rolling forming (UOE) process also known as seam weld pipes and the second as a result of high temperature piercing process called seamless tube manufacturing. The experimental settings consist of a wide range of sample types, whose geometric characteristics represent different state of stresses and loading modes. For low to intermediate stress triaxiality levels, flat specimens are extracted at different material orientations along with notched round bar samples for high stress triaxialities. The results indicate that despite the existing differences in plasticity between materials due to anisotropy induced processes, material failure can be characterized by an isotropic weighting function based on the Modified Mohr-Coulomb (MMC) criterion. The non-associated flow rule allows for inclusion of strain directional dependence in the definition of equivalent plastic strain by means of scalar anisotropy (Lankford) coefficients and thus keeping the original capabilities of the MMC model.

Stress state characterization of ductile materials during scratch abrasion

“…As a noteworthy characteristic, many of these state-of-the-art ductile damage models assume a cut-off value [27] of stress triaxiality of -0.33 below which failure strain is infinite, which has been based on experimental results of round bar compression tests. Additionally, the nature of the loading (proportional or not) also influences the ductile damage significantly [28][29][30][31][32][33][34].…”

Numerical Analysis of Edge Cracking in High-Silicon Steel during Cold Rolling with 3D Fracture Locus

“…The constitutive behavior of high silicon steel is expressed in a combination of exponential form and power law form. Paredes [17] reported that the predicted stressstrain behavior after yield as well as after strain localization was consistent with measurements when the Swift model [18] and Voce model [19] were properly combined, as shown in Equation ( 1):…”

“…The eight parameters (K, n, C η , η 0 , C s θ , C ax θ , C 1 , and C 2 ) must be calibrated for the construction of the fracture envelope from the MMC criterion. K and n are the same material constants adjusted for the power law (σ = Kε n ) [17]. C η and η 0 are the parameters that determine the yield criterion.…”

Metamodeling of structural failure: Case study of API S-135 steel tube cut in BOP

“…In order to characterize API S-135 failure in different stress states, several specimens were manufactured from a 5.5'' 21.9 ppf pipe (Figure 35). The extraction of the specimens for mechanical tests followed the procedure described by Paredes (2018) [89], which is illustrated in Figure 36.…”