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The 2014 Sandia Fracture Challenge (SFC2) Challenge Information Packet issued May 30, 2014 Brad L. Boyce [email protected] Sharlotte L.B. Kramer [email protected]. - PowerPoint PPT Presentation
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The 2014 Sandia Fracture Challenge (SFC2)
Challenge Information Packet
issued May 30, 2014
Brad L. Boyce [email protected] L.B. Kramer [email protected]
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.
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 [email protected] and copied to Sharlotte Kramer, [email protected] by June 15th. (2) Predictions must be e-mailed to [email protected] and copied to [email protected] by midnight, September 1st, 2014 (3 months after challenge was issued).(3)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.
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 = 3.1500.025 mm (0.1240.001 inches ). 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).
Force (N) at COD1=1mm
Force (N) at COD1=2mm
Force (N) at COD1=3mm
Peak Force of Test(N)
COD1@90% of peak force (mm)
COD2@90% of peak force (mm)
COD1@30% of peak force (mm)
COD2@30% of peak force (mm)
Crack Path (e.g. A-D-C-E)
Upper Bound (optional)
Expected Value
Lower Bound (optional)
Actuation Rate = 25.4 mm/sec
Actuation Rate = 0.0254 mm/secForce (N) at COD1=1mm
Force (N) at COD1=2mm
Force (N) at COD1=3mm
Peak Force of Test(N)
COD1@90% of peak force (mm)
COD2@90% of peak force (mm)
COD1@30% of peak force (mm)
COD2@30% of peak force (mm)
Crack Path (e.g. A-D-C-E)
Upper Bound (optional)
Expected Value
Lower Bound (optional)
Full name, e-mail address, and institution of all team members contributing to this prediction
Example: John Z. Doe, [email protected], University of Place; Jane A. Doe, [email protected], Federal Institute of Otherplace
Reporting Table
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, [email protected] and Sharlotte Kramer, [email protected] by September 1st.
Detailed Engineering Drawing of Challenge GeometryDimensions in millimeters
3.150.025
millimeters0.051 unless noted otherwise
Detailed Engineering Drawing of Challenge GeometryDimensions in inches
.124.001
COD1 (no hole ahead of the notch)
COD2 (hole ahead of the notch)
About Plate Orientation, Actuation Direction, and Crack Opening Displacement (COD) Gauges
Upper (fixed) end of test specimen
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).
Orie
ntati
on o
f pla
te ro
lling
dire
ction
rela
tive
to s
ampl
e ge
omet
ry
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.
About Crack Path Identification
B
D
E
C
A
F
G
Example crack path “B-G” Example crack path “A-E-D-F”Legend
Material Certification: Mill Annealed Ti-6Al-4V
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.
Tensile Bar Geometry
A 25.4 mm (1-inch) extensometer was used to measure strain for the tensile tests.
3.150.025
Dimensions in millimeters
ID orientation Thickness Width Area Location Broke Nominal Ratemm mm mm^2
RD8 rolling direction 3.175 6.35 20.16 with in extensometer 0.0254 mm/sRD2 rolling direction 3.1623 6.35 20.08 with in extensometer 0.0254 mm/sRD9 rolling direction 3.175 6.35 20.16 with in extensometer 25.4 mm/sRD7 rolling direction 3.1496 6.35 20.00 with in extensometer 0.0254 mm/sRD6 rolling direction 3.175 6.35 20.16 with in extensometer 0.0254 mm/sRD5 rolling direction 3.1623 6.35 20.08 with in extensometer 0.0254 mm/sRD4 rolling direction 3.1623 6.35 20.08 with in extensometer 25.4 mm/s
RD10 rolling direction 3.1623 6.35 20.08 with in extensometer 25.4 mm/s
TD1 transverse direction 3.1496 6.35 20.00 within exten 25.4 mm/sTD2 transverse direction 3.1496 6.35 20.00 within exten 0.0254 mm/sTD3 transverse direction 3.1496 6.35 20.00 within exten 0.0254 mm/sTD4 transverse direction 3.1242 6.35 19.84 within exten 0.0254 mm/sTD5 transverse direction 3.1496 6.35 20.00 within exten 25.4 mm/sTD6 transverse direction 3.1242 6.35 19.84 within exten 0.0254 mm/sTD7 transverse direction 3.1242 6.35 19.84 within exten 0.0254 mm/sTD8 transverse direction 3.1242 6.35 19.84 within exten 25.4 mm/s
TD11 transverse direction 3.1369 6.35 19.92 within exten 25.4 mm/sTD12 transverse direction 3.1496 6.35 20.00 within exten 25.4 mm/s
Actual Measured Dimensions of Tensile Tests
0
200
400
600
800
1000
1200
0 0.05 0.1 0.15 0.2
25.4 mm/sec, Transverse Direction
TD1TD5TD8TD11TD12
En
gin
ee
rin
g S
tre
ss (
MP
a)
Extensometer Strain [25.4 mm gage length] (mm/mm)
0
200
400
600
800
1000
1200
0 0.05 0.1 0.15 0.2
25.4 mm/sec, Rolling Direction
RD4
RD9
RD10
En
gin
ee
rin
g S
tre
ss (
MP
a)
Extensometer Strain [25.4 mm gage length] (mm/mm)
0
200
400
600
800
1000
1200
0 0.05 0.1 0.15 0.2
0.0254 mm/sec, Rolling Direction
RD2RD5RD6RD7RD8
En
gin
ee
rin
g S
tre
ss (
MP
a)
Extensometer Strain [25.4 mm gage length] (mm/mm)
0
200
400
600
800
1000
1200
0 0.05 0.1 0.15 0.2
0.0254 mm/sec, Transverse Direction
TD2TD3TD4TD6TD7
En
gin
ee
rin
g S
tre
ss (
MP
a)
Extensometer Strain [25.4 mm gage length] (mm/mm)
Tensile Data Summary
RD2.txt
RD4.txt
RD5.txt
RD6.txt
RD7.txt
RD8.txt
RD9.txt
RD10.txt
TD1.txt
TD2.txt
TD3.txt
TD4.txt
TD5.txt
TD6.txt
TD7.txt
TD8.txt
TD11.txt
TD12.txt
Raw ASCII text data files embedded
Deformed Tensile Shape
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.
12.6
mm
26.1 mm
Tran
sver
se.0
254
mm
/sec
Tran
sver
se25
.4 m
m/s
ecRo
lling
25.4
mm
/sec
Rolli
ng0.
0254
mm
/sec
Deformed Tensile ShapeRD4 TD12
RD7 TD4
Note: absolute scale could be off by 5%, but these images capture the shape of the failure cross-section
RD80.0254 mm/sec
RD925.4 mm/sec
Tensile Fractography: Comparing Typical Low Rate and High-Rate Morphology
• 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).
Fast-Rate Velocity Confirmation
Velocity-as-determined-by-actuator-LVDT.txt
Velocity-as-determined-by-high-speed-camera.txt
Example of extensometer and optical fiducials for high-speed confirmation
Shear Failure Calibration Specimen
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)
Shear Failure Calibration Data
Data will be forthcoming (expected June 21st, 2014)
Check back on http://imechanica.org/node/16609
Or e-mail [email protected] and [email protected] 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.