Fracture of Steels: New Approaches to Modeling and Experimental Characterization: Session I
Sponsored by: TMS Steels Committee
Program Organizers: Louis Hector, General Motors Global Technical Center; Ana Luiza Araujo, AK Steel Research & Innovation; Matthias Militzer, University of British Columbia; Amy Clarke, Los Alamos National Laboratory
Wednesday 8:00 AM
October 20, 2021
Room: A211
Location: Greater Columbus Convention Center
Session Chair: Ana Araujo, CBMM
8:00 AM
Applied Potential Influence on Stress Corrosion Cracking Susceptibility of 316LN Stainless Steel Rebars in Simulated Concrete Pore Solution with Chlorides: Ulises Martin1; Jacob Ress1; Juan Bosch1; David M. Bastidas1; 1University of Akron
In this work, the influence of the applied potential on the corrosion and mechanical properties of the passive film of AISI 316LN stainless steel rebar is studied. The tests were performed under stress corrosion cracking conditions using a slow strain rate in simulated concrete pore solution contaminated with 4 wt.% Cl– at different applied potentials, both cathodic and anodic. At the applied potentials ‒100 and +100 mVOCP the passive film is developed until the residual and tensile stresses exceed the ultimate tensile stress, producing a ductile fracture. Higher anodic potential of +400 mVOCP increases dissolution kinetics and diminishes the mechanical material performance, in addition, chloride induced cracking is seen as torn grains in the ductile overload area, indicating TG‒SCC mechanism. Mainly brittle fracture is seen at +600 mVOCP, because the oxygen equilibrium line is cross promoting the OER; where TG‒SCC and branched IG‒SCC cracks are formed in the cleavage planes.
8:20 AM Invited
Fracture Anisotropy of SS-304L Tubes under Biaxial Loading: Madhav Baral1; Yannis Korkolis2; 1University of New Hampshire; 2The Ohio State University
The ductile fracture behavior of 304L stainless steel is probed by inflating a tube under axial force and internal pressure. The tubes are inflated under volume control; by measuring the induced pressure and servo-controlling the axial force to follow it, proportional loading paths can be realized. The characteristic of these paths is that the stress state can be controlled very accurately, and thus it can remain constant for most of the experiment. The biaxial experiments are used to calibrate the non-quadratic, anisotropic yield criterion Yld2004-3D. While SS-304L is both rate- and temperature-dependent, this is neglected in this work. A finite element (FE) model of the experiments is first constructed, and is shown to reproduce the experimental responses (stress-strain in the axial and hoop directions) very closely. This model is then used to probe the fracture locus of the SS-304L, which is found to be anisotropic.
8:50 AM
Local Micromechanical Properties of Inclusions in Ferrous Alloys: Alejandra Slagter1; Joris Everaerts1; Léa Deillon1; Andreas Mortensen1; 1EPFL
Non-metalic oxide inclusions are commonly present in steel and can exert a tangible influence on its mechanical properties; yet, comparatively little is know of their intrinsic mechanical properties. We fill this gap by conducting micromechanical tests on micron-scale inclusions that have been precipitated within ferrous samples, aiming to measure their local mechanical properties including their stiffness and strength. Samples of iron containing oxide inclusions of varying composition are produced by melting oxygen-containing iron in a cold-crucible furnace and adding deoxidizing elements such as silicon, aluminum or calcium. Local inclusion micromechanical properties are measured by means of instrumented nanoindentation along flat polished surfaces, and compression testing of microscopic “C-shaped” bend test samples that have been carved by focused ion beam milling of inclusions partially exposed along electrochemically etched alloy surfaces.
9:10 AM Cancelled
The Mechanics of Size Effect in Brittle Fracture of Steel: Connecting the Change in Strain Energy and Its Planar Dissipation to Rationalize the Size-effect: K. S. Ravi Chandran1; 1University of Utah
Size-effect in nominally brittle fracture, which was documented in some of the earliest brittle fracture investigations on large scale steel structures, has defied a rigorous explanation thus far. In the typical size effect the fracture energy per unit volume, or the specific fracture energy, rapidly decreases with an increase in specimen size in geometrically-similar specimens spanning a large size range. In the present work, the net-section-mechanics approach is shown to fully explain the size-dependence of fracture energy. A consistent mechanics analysis is presented here under constant conditions of fracture initiation from notch. It is shown that, when analyzed on a common energy density principle, the equating of the change in net-section energy to the planar energy dissipation in fracture layer explains the size-effect. The analysis presented here provides a new framework to broadly explain the size effect on strength and toughness seen in steels and other materials.
9:50 AM
Peculiarities of Mechanics Destruction Tribojoints
at a Difficult Dynamic Loading
: Volodymyr Tsyganov1; Sergey Sheyko2; 1Zaporizhzhia Polytechnic National University; 2Zaporizhzhia National University
Mechanics of contact destruction tribojoints is considered at a friction in the conditions of difficult dynamics loading. Possibility of mathematical description complex damage knots friction is shown, intensities of wear taking into account the features forming superficial layer at a contact. The method of calculation superficial durability and longevity of tribojoints is presented and the example of practical estimation this interdependency is shown.Keywords: wearproofness; superficial layer; nanostructural state; loading.