The 2014 Sandia Fracture Challenge (SFC2) Challenge Information Packet issued May 30, 2014

1. The 2014 Sandia Fracture Challenge (SFC2) Challenge Information Packet issued May 30, 2014 Brad L. Boyce blboyce@sandia.gov Sharlotte L.B. Kramer slkrame@sandia.gov Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

2. Introduction • Thank you for participating in the 2nd Sandia Fracture Challenge. The purpose of this exercise is to: (a) compare methodologies for predicting fracture behavior of metallic alloys, and (b) identify methodologies that appear to be most predictive. This exercise is used to evaluate the state-of-health in computational mechanics prediction, identify areas of weakness for further development, and foster the building of relationships in the mechanics community. • In this exercise, participants are asked to predict the forces and displacements required to initiate and propagate a crack from a relatively simple geometry, and predict the path of crack propagation. Participants are allowed to bound their predictions as they see fit. • Details are provided regarding the challenge geometry and material (see subsequent slides). • Experiments will be performed by two independent test labs to confirm the experimentally observed behavior. • The following deadlines are in effect: • (1) Any concerns regarding the challenge or sufficiency of the supplied data should be communicated to Brad • Boyce blboyce@sandia.gov and copied to Sharlotte Kramer, slkrame@sandia.gov by June 15th. • (2) Predictions must be e-mailed to blboyce@sandia.gov and copied to slkrame@sandia.gov by midnight, September 1st, 2014 (3 months after challenge was issued). • Experimental results will be e-mailed to all participants by November 1st, 2014. • Ethics: Detailed material property data has been included in the challenge, including chemistry certifications, hardness measurements, and tensile behavior (shear behavior will be forthcoming). By participating in the Sandia Fracture Challenge, all participants agree to not perform any mechanical experiments for the purpose of calibrating or validating their models. The intent of this exercise is to be a computational exercise based solely on data provided.

3. The 2014 Sandia Fracture Challenge (SFC2) Geometry: An S-shaped sheet specimen with two slots and 3 holes tested in axial tension. Two larger holes are used for loading pins. Detailed engineering drawings provided on subsequent slides. Material: commercial stock sheet of mill-annealed Ti-6Al-4V, thickness = 3.1240.025 mm (0.1230.001inches ). Detailed certifications and material property measurements are provided on subsequent slides. Loading Rate: the tests will be performed at two actuation rates spanning 3 orders of magnitude: 25.4 mm/sec and 0.0254 mm/sec. Please report predictions for both loading rates if possible. Challenge Questions (a reporting table for the questions is provided on the following slide) For each of the two loading rates, please predict the following outcomes: Question 1: Report the force at following COD displacements: COD1= 1-mm, 2-mm, and 3-mm. (COD1 and COD2 are defined on slide 7) Note: COD1 and COD2 = 0 at the start of the test; the COD values refer to the change in length from the beginning of the test. Question 2: Report the peak force of the test. Question 3: Report the COD1 and COD2 values when the force has dropped by 10% (to 90% of the peak value). Question 4: Report the COD1 and COD2 values when the force has dropped by 70% (to 30% of the peak value). Question 5: Report the crack path (see slide 9 for examples on how to report crack path) Question 6: Report the expected force-COD1 and force-COD2 curves as two separate ASCII data files with column 1 as force (in N) and column 2 as COD (in mm).

4. Reporting Table Actuation Rate = 25.4 mm/sec Actuation Rate = 0.0254 mm/sec Also, please attach ASCII force-COD1 and force-COD2 curves for both 25.4 mm/sec and 0.0254mm/sec. Filename should be “teamname_COD#_[fast or slow].txt” E-mail predictions to Brad Boyce, blboyce@sandia.gov and Sharlotte Kramer, slkrame@sandia.gov by September 1st.

5. Detailed Engineering Drawing of Challenge Geometry Dimensions in millimeters 3.124.025 millimeters 0.051 unless noted otherwise

6. Detailed Engineering Drawing of Challenge Geometry Dimensions in inches .123.001

7. About Plate Orientation, Actuation Direction, and Crack Opening Displacement (COD) Gauges Upper (fixed) end of test specimen COD2 (hole ahead of the notch) COD1 (no hole ahead of the notch) Orientation of plate rolling direction relative to sample geometry Lower (actuated) end of test specimen The COD gage measures the change in displacement between two ‘knife edge’ features on the sample (indicated by green arrow).

8. About the test clevis grips… Clevis grips are 17-4PH stainless steel manufactured in accordance with standard ASTM E 399. The grips were purchased from Materials Testing Technology (www.mttusa.net), model number ASTM.E0399.08.

9. About Crack Path Identification A C G E F D B Legend Example crack path “A-E-D-F” Example crack path “B-G”

10. Material Certification: Mill Annealed Ti-6Al-4V

11. Hardness Values The average of 6 measurements from the Ti-6AL-4V plate for SFC2, was 36.1 HRC (Rockwell C), consistent with mill annealed Ti-6Al-4V.

12. Tensile Bar Geometry 3.124.025 Dimensions in millimeters A 25.4 mm (1-inch) extensometer was used to measure strain for the tensile tests.

13. Actual Measured Dimensions of Tensile Tests

14. Tensile Data Summary Raw ASCII text data files embedded

15. Deformed Tensile Shape Rolling 0.0254 mm/sec Transverse .0254 mm/sec Rolling 25.4 mm/sec Transverse 25.4 mm/sec 12.6 mm 26.1 mm Note: each of these images are at slightly different magnifications. In each image, the actual height of the grip region on the left side is 12.6 mm And the width of the grip region is 26.1 mm. These dimensions can be used to scale the rest of the image.

16. Deformed Tensile Shape RD4 TD12 TD4 RD7 Note: absolute scale could be off by 5%, but these images capture the shape of the failure cross-section

17. Tensile Fractography: Comparing Typical Low Rate and High-Rate Morphology RD8 0.0254 mm/sec RD9 25.4 mm/sec

18. Fast-Rate Velocity Confirmation • Images of the high-speed pull tests were captured using a high-speed Phantom 611 camera. • Images were analyzed in a computer vision software package (VIC 2D) to determine the relative change in distance between a pair of fiducials placed on the grips (see image) • The software output data as a total change in distance between the fiducials in terms of pixels • A pixels-per-inch ratio was determined by knowing the size of the fiducial, allowing for a determination of change of location per image. • The velocity was determined by knowing the time-step between images. Because of the relatively small change in displacement per image, this data was quite noisy. Therefore, a 30-point (central difference) rolling average of the velocity data is presented. • This data was compared to data collected by the MTS testing software, where the difference between displacement values was divided by the difference in the timestamp on the data for each line of data. (forward difference) • Good agreement was seen (attached ASCII data files provide a detailed comparison). Example of extensometer and optical fiducials for high-speed confirmation

19. Shear Failure Calibration Specimen 3.124.025 An ASTM standard does not appear to exist for calibration of shear failure in ductile metals. There are numerous methods in the literature, each with advantages and disadvantages. For this challenge, we will provide test data on a specimen geometry based on ASTM D 7078, the V-notched rail shear geometry. LVDT data of grip displacement will be provided, rather than strain gages described in the standard. The geometry has also been modified (deeper notch than the standard) to induce failure at lower forces, minimize grip rotation, and eliminate the potential for grip slippage. This test data is not yet complete, but will be provided (expected completion: June 21, 2014)

20. Shear Failure Calibration Data Data will be forthcoming (expected June 21st, 2014) Check back on http://imechanica.org/node/16609 Or e-mail blboyce@sandia.gov and slkrame@sandia.gov if you have not received this information. A note about fixturing for this rare test. The grips used are a hybrid of the two grips shown on the left, with a total of six bolts (3 tall, 2 wide) to minimize rotation during high-load testing. The grips are rigidly attached to the loadframe, but lateral compliance of the loadframe might be non-negligible, so we will provide data that describes both the axial and lateral motion of the grips.