The third Sandia fracture challenge: predictions of ductile fracture in additively manufactured metal

Abstract

The Sandia Fracture Challenges provide the mechanics community a forum for assessing its ability to predict ductile fracture through a blind, round-robin format where mechanicians are challenged to predict the deformation and failure of an arbitrary geometry given experimental calibration data. The Third Challenge, issued in 2017, required participants to predict fracture in an additively manufactured 316L stainless steel tensile-bar configuration containing through holes and internal cavities that could not have been conventionally machined. The volunteer participants were provided extensive materials data, from tensile tests of specimens printed on the same build tray to electron backscatter diffraction maps of the microstructure and micro-computed tomography scans of the Challenge geometry. The teams were asked to predict a number of quantities of interest in the response, including predictions of variability in the resulting fracture response, as the basis for assessment of the predictive capabilities of the modeling and simulation strategies. This paper describes the Third Challenge, compares the experimental results to the predictions, and identifies successes and gaps in capabilities in both the experimental procedures and the computational analyses to inform future investigations.

A Unified, Stable and Accurate Meshfree Framework for Peridynamic Correspondence Modeling—Part I: Core Methods

“…Since the dependence of the non-local deformation gradients, i.e., Eqs. (16), (25), and (28), on displacement is linear, the following constitutive model is constructed for consistency with linear elastostatics:…”

“…The unstable behavior appears as zero-energy mode oscillations in meshless peridynamic simulations and has been largely attributed to the cancellation of the non-uniform parts of deformation, which is allowed within the integration (averaging) technique [2,7,13,31,36]. The instabilities can lead to large errors in practical applications [16]. To address the issue, stabilization techniques have been proposed, such as (1) addition of penalty terms to deviations from homogeneous deformations [20,31], which involves artificial (non-physical) parameters, and (2) splitting of the integration domain into multiple sub-regions [13], which is unsettling as a continuum theory.…”

On the stability of the generalized, finite deformation correspondence model of peridynamics

“…Remark 8. Recently, Behzadinasab and Foster (2019), within the context of Sandia Fracture Challenge 2017 (Kramer et al, 2019), used the m = 1 model to predict the deformations and failure of an additively manufacture metal under tensile loading.…”

A framework for material calibration and deformation predictions applied to additive manufacturing of metals

“…Hence, sequential calibration of the individual properties and sequential calibration of their statistical distribution is required. The third Sandia Fracture Challenge (SFC3) (Kramer et al 2019) is a case study of the structural engineering task: blind computational predictions for a complex component produced by AM.…”

“…SFC3 (Kramer et al 2019) uses the same three steps as the previous challenges: calibration experiments guide material model identification, blind numerical predictions of the global and local behavior, and experimental verification using a custom 3D-geometry. This challenge used a 316L stainless steel, which was produced by Direct Metal Laser Sintering (DMLS) (also referred to as Laser Powder Bed Fusion (LPBF) King et al 2015).…”