Title: Predicting the reliability of an additively-manufactured metal part for the third Sandia fracture challenge by accounting for random material defects

Abstract

We describe an approach to predict failure in a complex, additively-manufactured stainless steel part as defined by the third Sandia Fracture Challenge. A viscoplastic internal state variable constitutive model was calibrated to fit experimental tension curves in order to capture plasticity, necking, and damage evolution leading to failure. Defects such as gas porosity and lack of fusion voids were represented by overlaying a synthetic porosity distribution onto the finite element mesh and computing the elementwise ratio between pore volume and element volume to initialize the damage internal state variables. These void volume fraction values were then used in a damage formulation accounting for growth of these existing voids, while new voids were allowed to nucleate based on a nucleation rule. Blind predictions of failure are compared to experimental results. The comparisons indicate that crack initiation and propagation were correctly predicted, and that an initial porosity field superimposed as higher initial damage may provide a path forward for capturing material strength uncertainty. Here, the latter conclusion was supported by predicted crack face tortuosity beyond the usual mesh sensitivity and variability in predicted strain to failure; however, it bears further inquiry and a more conclusive result is pending compressive testing of challenge-builtmore » coupons to de-convolute materials behavior from the geometric influence of significant porosity.« less

Authors:

Johnson, Kyle L.  ^[1];

• Search DOE PAGES for author "Johnson, Kyle L."
• Search DOE PAGES for ORCID "0000-0001-5126-1399"
• Search orcid.org for ORCID "0000-0001-5126-1399"

Emery, John M. ^[1]; Hammetter, Chris I. ^[1]; Brown, Judith Alice ^[1]; Grange, Spencer J. ^[1]; Ford, Kurtis Ross ^[1]; Bishop, Joseph E. ^[1]

---

+ Show Author Affiliations

1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Publication Date:

2019-07-24

Research Org.:

Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

Sponsoring Org.:

USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1570251

Report Number(s):

[SAND-2019-10227J]
[Journal ID: ISSN 0376-9429; 678949]

Grant/Contract Number:  

[AC04-94AL85000]

Resource Type:

Accepted Manuscript

Journal Name:

International Journal of Fracture

Additional Journal Information:

[ Journal Volume: 218; Journal Issue: 1-2]; Journal ID: ISSN 0376-9429

Publisher:

Springer

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; Additive manufacturing; Failure; Plasticity; Porosity; Sandia fracture challenge; Fracture