Introduction
Thank you for participating in the 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. Sandia National Labs and Naval Surface Warfare Center (NSWC) hope to use this exercise to foster
future relationships and develop strategy in fracture prediction.
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. Participants are also asked to submit their best estimate for the observed
force-displacement response of the test geometry.
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 by May 23rd.
(2) Predictions must be e-mailed to blboyce@sandia.gov by midnight, September 15, 2012 (4 months after
challenge was issued).
(3) Experimental results will be e-mailed to all participants by October 15th, 2012 using the form provided.
(4) For those participants who agreed to participate prior to the May 15th start date, you have been reserved a slot
to present your findings in Symposium 9-13: “Symposium on Simulation and Experiment of Ductile Tearing” at the
ASME International Mechanical Engineering Congress and Exposition, November 9-15.
knife edge points
for COD measurements
The Sandia Fracture Challenge
Holes for loading pins
D
C
A
B
E
The alloy. Precipitation hardened stainless steel, alloy 15-5 PH,
purchased from AK-Steel and heat treated at 1100 ºF for 4
hours. Resulting tensile data (included in subsequent slides)
indicates properties that are consistent with the H1075 or
H1100 condition.
The geometry. A sheet of nominally 0.125 inch thick (actual
0.124 inch thick) 15-5 PH was machined into the challenge
geometry as well as tensile bars, fracture toughness samples,
and metallurgical coupons. The challenge geometry, shown on
the left, includes detailed engineering drawings in the
subsequent slides.
The challenge. When loaded at room temperature at a loading rate of 0.0005 inches/sec,
(Q1) What is the force and COD displacement1 at which a crack first initiates2?
(Q2) The starter notch, A, holes B-D, and the backside edge, E are labeled in the drawing.
What is the path of crack propagation? i.e. a crack that initiated on the backside and
propagated to hole D and then to notch A would be labeled “E-D-A”.
(Q3) If the crack does propagate to either holes B,C, or D, at what force and COD
displacement does the crack re-initiate out of the first hole?
1COD:
A Crack opening displacement (COD) gage will be used to monitor load-line displacement at
the point of the ‘knife-edge’ features, akin to fracture toughness testing. Only COD will be
measured (the test will begin with COD=0 inches).
2For the purposes of this challenge, crack initiation will be defined as a crack 100m on the
sidewall surface of the sample, so as to be witnessed by in-situ microscope.
The Sandia Fracture Challenge
Reporting Form
Please report predictions to Brad Boyce, blboyce@sandia.gov,
by September 15, 2012 using the following form:
Q1 force (lbs)
Q1
displacement
(inches)
Q2 path (i.e. AB-C-D-E)
Q3 force (lbs)
Upper Bound
Ex: 100 lbs
Expected
Outcome
Ex: 98 lbs
Lower Bound
Ex: 90 lbs
Filename for
Force-COD data
Ex: Groupname-force-COD-data.txt
Participants
reporting these
results:
Ex: John Doe, Joe Public, Annie Result, University of Awesome
Q3
displacement
(inches)
Ex: A-B-C-D-E
In addition to the scalar quantities reported in this table, please supply a single datafile
representing your best estimate for the force vs COD displacement. Data file should be 2
columns of ASCII text: first column- force in lbs, second column- COD displacement in inches
(change in displacement between knife edges).
The Sandia Fracture Challenge
Ethics
Detailed material property data has been included in the challenge, including
heat treatment schedule, chemistry certifications, hardness measurements,
tensile behavior, and sharp crack behavior.
Any participant can request a sample coupon of material for the sole purpose
of metallurgical examination.
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.
Challenge Geometry – dimensions in inches
Challenge Geometry – dimensions in millimeters
Original Material Cert.
Nominal Material Properties for AK Steel 15-5 PH H1075
Nominal Material Properties
0.2%
Yield
Strength
Condition
A
H 900
H 925
H 1025
H 1075
H 1100
H 1150
H 1150M
Ultimate
Tensile
Strength
ksi
MPa
ksi
MPa
-185**
175
165
150
135
125
85
-1276
1207
1138
1035
931
862
584
-200
190
170
165
150
145
125
-1378
1309
1173
1138
1035
1000
882
Condition
H 900
H 925
H 1025
H 1075
H 1100
H 1150
H 1150M
%
Rockwell
Elongation Reduction
C
in 2"
of Area Hardness
%
-14
14
15
16
17
19
22
-50
54
56
58
58
60
68
Ultimate
Tensile
Strength
0.2%
Yield Strength
ksi
MPa
ksi
MPa
185
175
165
150
135
125
85
1276
1207
1138
1035
931
862
584
200
190
170
165
150
145
125
1378
1309
1173
1138
1035
1000
862
35
44
42
38
36
34
33
27
Charpy
V-Notch
Impact
Strength
Modulus
of Elasticity (E)*
ft-lb
J
ksi
MPa
-15
25
35
40
45
50
100
-20
34
48
54
61
68
138
-28.5
-------
-195
-------
%
Elongation
in 2"
%
Reduction
of Area
Rockwell C
Hardness
10
11
12
13
14
15
18
30
35
42
43
44
45
50
44
42
38
36
34
33
27
Modulus
of Rigidity (G)
ksi x 10³ MPa x 10³
-11.2
-11.0
10.0
-10.0
--
-77.3
-75.9
69.0
-69.0
--
Charpy V-Notch
Impact Strength
ft-lb
J
7
17
27
30
30
50
100
10
23
37
41
41
63
136
Heat Treatment
Performed at Sandia
H1100 – 4 hrs. at 1100˚F
All samples and coupons were fabricated
from a single 12”x12” plate of 15-5 PH SS.
DAQSTANDARD
Data Viewer
Microsoft
R8.22.01
R8.22.01
Microsoft
Device Type
Serial No.
File Message
Time Correction
Starting Condition
Dividing Condition
Meas Ch.
Math Ch.
Ext Ch.
Data Count
Sampling Interval
Start Time
Stop Time
Trigger Time
Trigger No.
Damage Check
Started by
Stopped by
DX2000
U1J802972
None
Restart after Black Out
Auto
10
0
0
900
4 sec
Note added RNS 02.20.12 Part A-C only. Parts D-G are 60 seconds.
3/19/2012 14:10:36
0
3/19/2012 15:10:32
0
3/19/2012 15:10:32
0
899
Not Damaged
[ Key In ]
[ Running ]
Num. Of Converted Data
Num. Of Converted Ch.
Converted Group
(double click on the embedded worksheet to access all
heat treat data)
Date
Time
3/19/2012 14:10:36
3/19/2012 14:10:40
3/19/2012 14:10:44
3/19/2012 14:10:48
3/19/2012 14:10:52
3/19/2012 14:10:56
3/19/2012 14:11:00
3/19/2012 14:11:04
3/19/2012 14:11:08
3/19/2012 14:11:12
3/19/2012 14:11:16
3/19/2012 14:11:20
3/19/2012 14:11:24
3/19/2012 14:11:28
3/19/2012 14:11:32
3/19/2012 14:11:36
3/19/2012 14:11:40
3/19/2012 14:11:44
3/19/2012 14:11:48
3/19/2012 14:11:52
3/19/2012 14:11:56
3/19/2012 14:12:00
3/19/2012 14:12:04
3/19/2012 14:12:08
3/19/2012 14:12:12
3/19/2012 14:12:16
3/19/2012 14:12:20
3/19/2012 14:12:24
848-98024-****
900
4
1 -
1
MAX TEMPS:
598.4
Ch.
CH001
Tag
CONTROL
Tag No.
Unit
°C
sec
MIN
MAX
0
28.3
28.3
0
28.3
28.4
0
28.3
28.4
0
28.3
28.4
0
28.3
28.4
0
28.4
28.4
0
28.4
28.4
0
28.4
28.4
0
28.4
28.4
0
28.4
28.4
0
28.4
28.4
0
28.4
28.4
0
28.4
28.4
0
28.4
28.4
0
28.4
28.4
0
28.3
28.4
0
28.3
28.4
0
28.3
28.4
0
28.3
28.3
0
28.3
28.4
0
28.3
28.3
0
28.2
28.3
0
28.2
28.3
0
28.2
28.3
0
28.2
28.2
0
28.2
28.2
0
28.1
28.2
0
28.1
28.1
587.6
22
CH002
OVERTEMP
CH003
WORK 1
°C
MIN
°C
MIN
MAX
29.1
29.1
29.1
29.2
29.2
29.2
29.2
29.2
29.1
29.1
29.1
29.1
29
29
29
29
29
28.9
29
28.9
28.9
28.8
28.8
28.7
28.7
28.6
28.4
28.4
29.1
29.1
29.2
29.2
29.2
29.2
29.2
29.2
29.2
29.1
29.1
29.1
29.1
29.1
29
29
29
29
29
29
28.9
28.9
28.8
28.8
28.7
28.7
28.6
28.4
°C
MIN
MAX
20.9
20.9
20.9
20.9
20.9
20.9
21
21
20.9
20.9
21
21
21
21
21
21
21
21
20.9
20.9
20.9
20.9
20.9
20.9
20.9
20.9
20.8
20.8
616.7
CH004
WORK 2
20.9
20.9
20.9
20.9
20.9
21
21
21
21
21
21
21
21
21
21
21
21
21
21
21
20.9
20.9
20.9
20.9
20.9
20.9
20.9
20.8
MAX
27.8
27.8
27.8
27.7
27.4
27.2
26.8
26.5
26.2
26
25.9
25.9
26
26
26.1
26.2
26.2
26.3
26.3
26.2
26
25.8
25.7
25.3
25
25
24.8
24.8
27.8 PART A
27.8
27.8
27.8
27.7
27.4
27.2
26.8
26.5
26.2
26
26
26.1
26.1
26.2
26.2
26.3
26.3
26.4
26.3
26.2
26
25.8
25.7
25.3
25
25
24.8
Sample Extraction from a single 15-5 PH SS plate (12”x 12”x 0.123”)
Metallurgy Witness
Samples for Participants
5 Fracture
Toughness
Samples
3 Long. Tensiles
Tensile Sample Drawing
Tensile Test Setup
20 kip MTS system cell (ser. # 4678)
Universal joint
20 kip wedge loaded grips
1” 50% MTS Extensometer
(ser. # 10192232C)
20 kip actuator, MTS test frame (ser. #1327)
Summary of Tensile Test Results
UTS (ksi)
YS (ksi)
Strain (%)
RA (%)
• Longitudinal 1
162.9
159.8
16.3
54.0
27.2
• Longitudinal 2
162.4
160.1
16.7
53.6
28.7
• Transverse 1
160.9
157.7
15.8
46.6
28.9
• Transverse 2
160.3
155.5
15.9
50.1
27.6
Modulus (mpsi)
Tensile Data Files with
180000.0
Trans2, Wo=0.248", Thicko=0.123"
psi
Stress/Strain Conversions
and YS Determinations
(double click on the embedded graphs
to access all data)
668.1
1097.8
1594.7
2148.4
2652.4
3109.0
3669.1
4227.3
4679.2
5181.6
5731.8
6203.0
6689.0
7203.6
7634.5
8174.0
8552.8
9046.2
9474.8
9983.9
10409.2
10801.1
11181.8
11701.5
12048.9
12500.5
12899.6
13240.2
13655.4
14152.7
14455.3
14833.6
15107.8
15548.0
16014.8
16357.7
16846.6
17064.4
17442.2
17917.1
18226.5
18642.3
18950.5
19488.2
19798.2
20235.9
20543.8
20955.6
21390.0
21681.0
22191.3
22577.0
22886.1
23283.6
23727.1
160000.0
140000.0
120000.0
100000.0
Long 1
Long 2
Trans 1
80000.0
Trans 2
60000.0
40000.0
20000.0
-2.00E-02
0.0
0.00E+00
2.00E-02
4.00E-02
6.00E-02
8.00E-02
1.00E-01
1.20E-01
1.40E-01
1.60E-01
180000
1.80E-01
Trans 1
160000.0
160000
140000.0
140000
y = 28,897,374x + 30,733
120000.0
100000.0
120000
Trans 1
80000.0
100000
80000
0.2% Offset
60000.0
Trans 1
40000.0
Linear (Trans
20000.0
60000
0.0
0.00E+00 1.00E-03 2.00E-03 3.00E-03 4.00E-03
40000
20000
0.00232
0.00682
0
-0.005
0
0.005
0.01
0.015
0.02
0.025
40000
170000
Stress/Strain Plots
UTS
Long 1 = 162.9 ksi
Long 2 = 162.4 ksi
Trans 1 = 160.9 ksi
Trans 2 = 160.3 ksi
180000.0
160000.0
140000.0
Engineering Stress (psi)
120000.0
YS
Long 1 = 159.8 ksi
Long 2 = 160.1 ksi
Trans 1 = 157.7 ksi
Trans 2 = 155.5 ksi
Total Strain
Long 1 = 16.3 %
Long 2 = 16.7 %
Trans 1 = 15.8 %
Trans 2 = 15.9 %
100000.0
80000.0
Long 1
Long 2
Trans 1
Trans 2
60000.0
RA
Long 1 = 54.0 %
Long 2 = 53.6 %
Trans 1 = 46.6 %
Trans 2 = 50.1 %
40000.0
20000.0
0.0
0.00E+00
2.00E-02
4.00E-02
6.00E-02
8.00E-02
1.00E-01
1.20E-01
1.40E-01
Engineering strain measured using a 1-inch extensometer (inch/inch)
1.60E-01
1.80E-01
Raw Tensile Data Files
(double click on the file icons to open data files)
Data files are ASCII text files with space-separated columns
Fracture Cross-Sections
Longitudinal 1 - 54.0% RA
Longitudinal 1 – 53.6% RA
Transverse 1 – 46.6% RA
Transverse 2 – 50.1% RA
Side view of fracture profile
Longitudinal 1 - 54.0% RA
Transverse 1 – 46.6% RA
Longitudinal 1 – 53.6% RA
Transverse 2 – 50.1% RA
Average Rockwell Hardness Values
Mean: 34.9 HRC
Std. Dev. 0.31
Hardness values were taken from the
“skeletons” left from the tensile samples
Mean: 36.1 HRC
Std. Dev. 0.55
Fracture Toughness Sample Drawing
Fracture Toughness Test Setup
0.5 kip Interface cell (ser.# 62003) – precracking
5 kip Interface cell (ser.# 10541) - testing
Universal joint
MTS COD gage (ser. # 213) 0.0” – 0.200”
20 kip actuator, MTS test frame (ser. #1327)
Fatigue Precracking Load Shedding Schedule to prepare samples for
Fracture Toughness Tests
a/w
0.5
0.55
0.6
delta P
Pmax
Pmin
delta K
240 266.6667 26.66667
19
120 133.3333 13.33333
12
50 55.55556 5.555556
6
Fracture Toughness Test Results
1200
KQ values are offered as an indication only as the
sample thickness was insufficient for a valid K1c
and the Pmax/PQ ratio was invalid
KQ = 60.5 ksi √in
1000
KQ = 66.0 ksi √in
KQ = 74.4 ksi √in
Force (lbs)
800
15-5 H1100 K1c Test 1
600
15-5 H1100 K1c Test 2
15-5 H1100 K1c Test 3
400
200
F(a/W) = 12.84
F(a/W) = 13.82
F(a/W) = 15.01
Initial a/W after fatigue precracking = 0.584
Initial a/W after fatigue precracking = 0.603
Initial a/W after fatigue precracking = 0.623
0
0.00E+00
5.00E-02
1.00E-01
1.50E-01
COD Displacement (inch)
2.00E-01
2.50E-01
Raw Fracture Toughness Data Files
(double click on the file icons to open data files)