PhD Defence Santonocito - Energy Methods for Fracture and Fatigue assessment

Ph.D. Defence
November 20, 2020
Ph.D. candidate
Dario Santonocito
University of Messina
Department of Engineering
Ph.D. course in «Engineering and Chemistry of Materials and Constructions»
Cycle XXXIII
Supervisor: Prof. Giacomo Risitano Ph.D. Coordinator: Prof. Giovanni Neri
ENERGY METHODS FOR FRACTURE AND
FATIGUE ASSESSMENT

Ph.D. defence - Energy Methods for fracture and Fatigue assessmentPh.D. defence - Energy Methods for fracture and Fatigue assessment
Why adopt Energy Approaches?
A classical fatigue test campaign, according to Standards:
2 Dario Santonocito
 5 stress level;
 5 specimens per stress level;
 Every specimen must be broken (between 1’000 and
2’000’000 cycles)
 Optimal test frequency (10-20 Hz)
A simple time estimation:
 5 stress level x 5 specimens = 25 specimens;
 Average fatigue life of 1’000’000: 25 specimens x 1’000’000 cycles= 25’000’000 cycles;
 15 Hz as average frequency: 25’000’000 cycles / 15 Hz = 1’666’667 s -> 27’778 min -> 463 h !!!!
1x103
σ[MPa]
N. cycles
NA=2x106
S-N curve with
scatter band at
5%-90% PS
σ0, 50%
σ0, 5%
σ0, 90%
Fatigue limits

Theoretical Background: Energy Methods
Evaluation of the energetic release during:
3 Dario Santonocito
 Fatigue test
 Static tensile test
Evaluation of failure in notched components (Local approaches):
 Notched – Stress Intensity Factor (NSIF)
 Strain Energy Density (SED)
 Peak Stress Method (PSM)
 Thermographic Method (TM) (Risitano Thermographic Method)
 Static Thermographic Method (STM)
 ~4-5 h to obtain the S-N curve!
 ~5 min to obtain the fatigue limit!

Thermographic Method (TM)
D. Santonocito
4
During HCF tests of common
engineering metals, the temperature
evolution on the specimen surface,
detected by means of an infrared
camera, is characterized by three
phases when the specimen is
cyclically loaded above its fatigue
limit:
1. an initial rapid increment (phase I),
2. a plateau region (phase II),
3. a very high further temperature
increment until the failure (phase III).IR Camera
σ0
La Rosa, G., Risitano, A., 2000. Thermographic methodology for rapid determination of the fatigue limit of materials
and mechanical components. International Journal of Fatigue 22, 65–73. 439 Citations (Scopus)

Static Thermographic Method (STM): 10 years of research
5 Dario Santonocito
1. Corigliano P, Cucinotta F, Guglielmino E, Risitano G, Santonocito D. Fatigue assessment of a marine structural steel and comparison with Thermographic
Method and Static Thermographic Method. Fatigue Fract Eng Mater Struct 2020;43:734–43. doi:10.1111/ffe.13158.
2. Santonocito D. Evaluation of fatigue properties of 3D-printed Polyamide-12 by means of energy approach during tensile tests. Procedia Struct Integr
2020;25:355–63. doi:10.1016/j.prostr.2020.04.040.
3. Foti P, Santonocito D, Ferro P, Risitano G, Berto F. Determination of Fatigue Limit by Static Thermographic Method and Classic Thermographic Method on
Notched Specimens. Procedia Struct Integr 2020;26:166–74. doi:10.1016/j.prostr.2020.06.020.
4. Ricotta, M.; Meneghetti, G.; Atzori, B.; Risitano, G.; Risitano, A. Comparison of Experimental Thermal Methods for the Fatigue Limit Evaluation of a Stainless
Steel. Metals 2019, 9, 677.
5. G. Risitano, E. Guglielmino, D. Santonocito, Evaluation of mechanical properties of polyethylene for pipes by energy approach during tensile and fatigue tests,
Procedia Structural Integrity, Volume 13, 2018, Pages 1663-1669, ISSN 2452-3216.
6. Risitano, A., Corallo, D., Guglielmino, E., Risitano, G. and Scappaticci, L. (2016) “Fatigue assessment by energy approach during tensile tests on AISI 304
steel”, Frattura ed Integrità Strutturale, 11(39), pp. Pages 201-215.
7. V. Crupi, E. Guglielmino, G. Risitano, F. Tavilla, Experimental analyses of SFRP material under static and fatigue loading by means of thermographic and DIC
techniques, Composites Part B: Engineering, Volume 77, 2015, Pages 268-277, ISSN 1359-8368.
8. A. Risitano,G. Risitano, Determining Fatigue Limits with Thermal Analysis of Static Traction Tests, Fatigue Fract. Engng. Mater. Struct. 36 (2013) 631-639
9. C. Clienti, G. Fargione, G. La Rosa, A. Risitano, G. Risitano, A first approach to the analysis of fatigue parameters by thermal variations in static tests on
plastics, Engineering Fracture Mechanics, Volume 77, Issue 11, 2010, Pages 2158-2167, ISSN 0013-7944.
10.Risitano, A. and Risitano, G., L’importanza del “parametro energetico” temperature per la caratterizzazione dinamica dei materiali, Workshop
“Progettazione a Fatica di Giunzioni Saldate (…e non)— Sviluppi teorici e problem applicativi”, March 9-10, 2009, Frat.ed Int. Strutt., 9, 123–124, 2009

Static Thermographic Method (STM)
6 Dario Santonocito
During static tests of common engineering materials,
the temperature evolution on the specimen surface,
detected by means of an infrared camera, is
characterized by three phases:
1. an initial approximately linear decrease
due to the thermoelastic effect (phase I);
2. then the temperature deviates from
linearity until a minimum (phase II);
3. a very high further temperature increment
until the failure (phase III).
A. Risitano,G. Risitano, Determining Fatigue Limits with Thermal Analysis of Static
Traction Tests, Fatigue Fract. Engng. Mater. Struct. 36
(2013) 631-639
Risitano, A. and Risitano, G., L’importanza del “parametro energetico” temperature
per la caratterizzazione dinamica dei materiali, Workshop “Progettazione a Fatica di
Giunzioni Saldate (…e non)— Sviluppi teorici e problem applicativi”, Forni di Sopra
(UD), March 9 and 10, 2009, Frattura ed Integrità Strutturale, 9, 123–124, 2009 1010 




 TKT
c
T ms
σ[MPa]
ΔTs[K]
t [s]
Phase IIIPhase IIPhase I
σlim
σyielding
A
B
B’
A’
Thermo-Elastic material constant

Temperature trend in Static tensile test: a FE implementation
7 Dario Santonocito
σ [MPa]
ΔT[K]
Km
Thermo-Plastic
Phase
Thermo-Elastic
Phase
σmicro yielding
pe TTT 



11 TIKTI
c
T me 


t
Q
t
T
c






 



2
1
1






pppp d
c
dtQ
c
T
pp WQ  
Thermo-Elastic
effect
Thermo-Plastic
effect
Pitarresi G, Patterson EA. A review of the general theory
of thermoelastic stress analysis. J Strain Anal Eng Des
2003;38:405–17. doi:10.1243/03093240360713469.
Biot MA. Thermoelasticity and irreversible
thermodynamics. J Appl Phys 1956;27:240–53.
doi:10.1063/1.1722351.
Ly H., Inoue H, Irie Y. Numerical Simulation on Rapid Evaluation of Fatigue Limit through
Temperature Evolution. J Solid Mech Mater Eng 2011;5:459–75. doi:10.1299/jmmp.5.459.
dV
σ

Local Approaches: two Study abroad experience
8 Dario Santonocito
University of Padova
Norwegian University of
Science and Technology
Messina
Padova
Trondheim
Supervisor:
Prof. Filippo Berto
Supervisor:
Prof. Giovanni Meneghetti
General aspects of Local Approaches:
• N-SIF
• SED
• PSM
SED applied to
welded structures
and hyperelastic
materials
(3 months)
(1 month)

Local approaches: Notched –Stress Intensity Factor (NSIF)
Stress field around a sharp V-notch:
9 Dario Santonocito
2α= 0°
σθθ
τrθ σrr
θ
r
ρ= 0
γ
Mode II
Mode I
𝜎 𝜃𝜃
𝜎𝑟𝑟
𝜏 𝑟𝜃
=
𝐾1
𝑟1−𝜆1
⋅
𝜎 𝜃𝜃 𝜃
𝜎𝑟𝑟 𝜃
𝜏 𝑟𝜃 𝜃 𝑚𝑜𝑑𝑒 𝐼
+
𝐾2
𝑟1−𝜆2
⋅
𝜎 𝜃𝜃 𝜃
𝜎𝑟𝑟 𝜃
𝜏 𝑟𝜃 𝜃 𝑚𝑜𝑑𝑒 𝐼𝐼
Williams’ eigenvalues
Stress field singularity
𝐾1 = 2𝜋 lim
𝑟→0+
𝑟1−𝜆1 𝜎 𝜃𝜃(𝑟, 𝜃 = 0
𝐾2 = 2𝜋 lim
𝑟→0+
𝑟1−𝜆2 𝜏 𝑟𝜃(𝑟, 𝜃 = 0
Notched Stress Intensity Factor (NSIF)
for Mode I and II
i.e. the asymptotic stress field at a distance
r= 1/2π from the notch tip.
Lazzarin P, Tovo R. A notch intensity factor approach to the stress analysis of welds.
Fatigue Fract Eng Mater Struct 1998;21:1089–103. doi:10.1046/j.1460-
2695.1998.00097.x.

Local approaches: Strain Energy Density (SED)
10 Dario Santonocito
2α
γ
𝑊𝑐 =
𝜎𝑡
2
2𝐸
𝑊 𝑟, 𝜃 =
1
2𝐸
𝜎11
2
+ 𝜎22
2
+ 𝜎33
3
− 2𝜈 𝜎11 𝜎22 + 𝜎11 𝜎33 + 𝜎22 𝜎33 + 2 1 + 𝜈 𝜎12
2
Mode II
Mode I
R0 𝑅0 =
1 + 𝜈 5 − 8𝜈
4𝜋
𝐾𝐼𝐶
𝜎𝑡
2
𝑝𝑙𝑎𝑛𝑒 𝑠𝑡𝑟𝑎𝑖𝑛
Strain Energy Density for a
linear elastic isotropic material
Critical Strain Energy Density
𝑅0 =
5 − 3𝜈
4𝜋
𝐾𝐶
𝜎𝑡
2
𝑝𝑙𝑎𝑛𝑒 𝑠𝑡𝑟𝑒𝑠𝑠
𝑅0 =
𝐼1
2𝜆1 𝜋 − 𝛼
𝐾𝐼𝐶
𝜎𝑡
2
1
2 1−𝜆1
Control Radius
(2α=0)
Control Radius
(2α>0)
Strain Energy Density over a Control
Volume
𝑊 =
𝐸 𝑅
𝐴 𝑅
=
𝑒1
𝐸
𝐾1
𝑅0
1−𝜆1
2
+
𝑒2
𝐸
𝐾2
𝑅0
1−𝜆2
2
𝑅0 =
2𝑒1Δ𝐾1𝐴
𝑁
Δ𝜎𝐴
1
1−𝜆1
Fatigue
assessment by
SED approach
R0
Sharp V-notch
assumption
2α=135°
Lazzarin P, Zambardi R. A finite-volume-energy based approach to
predict the static and fatigue behavior of components with sharp V-
shaped notches. Int J Fract 2001;112:275–98.
doi:10.1023/A:1013595930617.

Local approaches: Peak Stress Method (PSM)
2α
γ
r
Mode I
Mode II
X
Y
Average Element
dimension
d =1 mm
𝐾1 = 𝐾 𝐹𝐸
∗
⋅ 𝜎 𝑝𝑒𝑎𝑘 ⋅ 𝑑1−𝜆1
σpeak
Elastic Peak Stress
at Notch vertex
KI/σpeak depends only on d!
NSIF in terms of elastic peak stress
Constant:
• FE software
• Element type
• Mesh pattern
Δ 𝑊 =
𝑒1
𝐸
𝐾 𝐹𝐸
∗
⋅ Δ𝜎 𝑝𝑒𝑎𝑘 ⋅
𝑑
𝑅 𝑐
1−𝜆1
2
+
𝑒2
𝐸
𝐾 𝐹𝐸
∗∗
⋅ Δ𝜏 𝑝𝑒𝑎𝑘 ⋅
𝑑
𝑅 𝑐
1−𝜆1
2
=
1 − 𝜈2
2𝐸
⋅ Δ𝜎𝑒𝑞,𝑝𝑒𝑎𝑘
2
SED in terms of elastic peak stress
Meneghetti G, Lazzarin P. Significance of the elastic
peak stress evaluated by FE analyses at the point of
singularity of sharp V-notched components.
Fatigue Fract Eng Mater Struct 2007;30:95–106.
doi:10.1111/j.1460-2695.2006.01084.x.

Application of the TM and STM to…
Material
Thermographic
Method (TM)
Static
Thermographic
Method (STM)
Traditional
fatigue test
Numerical
Simulation
Structural steel(S355) X X X
Medium carbon steel (C45) X X X
Notched medium carbon steel
(AISI1035)
X X X
High Strength Concrete X X
HD Polyethylene (PE100) X X X
PA66GF35 X X
Polyamide 12 (PA12 - AM) X X
Stainless Steel (AISI 316L – AM) X X
STEELs
PLASTIC/
COMPOSITEs
ADDITIVE
MATERIALs

TM and STM: typical Experimental Setup
Dogbone specimen
 High emissivity black
paint (>0.98)
 Dic speckle pattern
ITALSIGMA 25 kN
IR Camera
FLIR A40
DIC Aramis
3D 12 M
INSTRON 8854/ MTS 810 250 kN
Static tests
Fatigue tests
 Stress rate
 Displacement rate
 Stress control
 R= σi/σs, f= 5-20 Hz
σ0
STEELSETUP
PLASTIC/COMPOSITESETUP

TM and STM on Steel: Structural steel S355
Corigliano, P, Cucinotta, F, Guglielmino, E, Risitano, G, Santonocito, D. Fatigue assessment of a marine structural
steel and comparison with thermographic method and static thermographic method. Fatigue Fract Eng Mater
Struct. 2020; 43: 734– 743
TM
Tests
Comparison
STM
Tests
Traditional
Fatigue Tests
σ0, TM= 179.8 MPa
σ0, 50%= 173 MPa
Traditional
fatigue test
scatter band
σlim STM= 181.2 MPa
σlim STM= 181.2 MPa
σ0, TM= 179.8 MPa

TM and STM on Steel: Medium Carbon Steel (C45)
Test procedure
University of
Messina
University of
Catania
Politechnic of
Milan
University of
Padova
University of
Pisa
STM 222,2 ± 4,0 205
TM (dT/dN) 316
TM (Tstab) 200÷220 310 309
E-mode (ω) 301
D-mode (2ω) 305
Q 308 295
Staircase 274
261 (PS 10%)
245 (PS 50%)
229 (PS 90%)
Static Tensile
Tests Fatigue Tests
MEAS Group
ROUND
ROBIN on
Several
Energy
Methods Guglielmino E., Risitano G., Santonocito D., A new
approach to the analysis of fatigue parameters by thermal
variations during tensile tests on steel, Procedia
Structural Integrity,
Volume 24, 2019, Pages 651-657, ISSN 2452-3216

TM and STM on Plastic: High Density Polyethylene (PE100)
G. Risitano, E. Guglielmino, D. Santonocito, Evaluation of mechanical properties of polyethylene for pipes by energy approach
during tensile and fatigue tests, Procedia Structural Integrity, Volume 13, 2018, Pages 1663-1669, ISSN 2452-3216
PhaseI
Phase II Phase III
σlim= 12.4 MPa
Risitano G, Guglielmino E, Santonocito D. Energetic approach for the fatigue assessment of PE100. Procedia
Struct Integr 2020;26:306–12. doi:10.1016/j.prostr.2020.06.039.
σTM= 11.32 MPa
Fatigue Tests Static
Tensile
Tests
Comparison

TM and STM on Composite: PA66GF35
Santonocito D. Numerical and experimental evaluation of the energetic release during tensile tests on short fiber reinforced composite material.
Under print (presented at national machine design conference AIAS2020, Juniores Session)
Fiber
d= 10 μm
l= 280 μm
Type 1A ISO527
• Injection moulded
• 0° Orientation angle
• Room Temperature
condition
• Naturally aged
MFD
• Fibre (E-Glass): Linear Elastic
• Matrix (PA66): Von Mises Yielding
𝑉𝑓 =
𝑙𝑑2
𝐿𝑆2
Micro-mechanic FEM
fibre matrix
Axialsimmetry
displacement
L
lf
S
df
Fibre Volume fraction :
X
Z
Y
displacement
1/8th geometry
Symm XY
Symm YZ
I1σ , Wp
Macro-mechanic FEM
Fiber-Matrix debonding
~5% lf
ε= 0.001
ε= 0.002
ε= 0.004
ε= 0.0095
ε= 0.008
Stress Ratio
σlim Exp =
31.5 MPa σlim FE = 32.7 MPa
Phase I Phase II Phase III

TM and STM on AM: Polyamide 12 (PA12)
Yielding
stress?
E linear regression
ε1=0.0005-ε2=0.0025
Phase I Phase II Phase III
NA=2x106
HP Jet Fusion 3D
4200 printer
(MultiJet Fusion)
Santonocito D., Evaluation of fatigue properties of 3D-printed Polyamide-12 by means of energy approach during tensile tests, Procedia Structural
Integrity, Volume 25, 2020, Pages 355-363, ISSN 2452-3216
Printing profile:
• Mechanical
• Cosmetic
• Fast
1,287 mm
0,930 mm
0,383 mm 0,686 mm
IR
Static
Failure
Fatigue
Failure

TM and STM on AM: Stainless steel (AISI316L)
X
Y
Z
XY
Z
Prof. Andrea Gatto
σ
σ
Step Cycles
Stress sup
[MPa]
1 10.000 80
2 10.000 90
3 10.000 100
4 10.000 110
5 10.000 120
6 10.000 130
7 10.000 140
8 10.000 150
9 10.000 160
10 10.000 170
… 10.000 …
-1
0
1
2
3
4
5
6
7
0 10000 20000 30000 40000 50000 60000
ΔT[K]
N. cycles
Failure!
Nf = 52.672
SLS Printing process:
• Laser Power 300W
• Z building direction
No significative
temperature
increment!

SED application to Welded joints
Full
Penetration
Partial
Penetration
FE Model
Foti P, Santonocito D, Risitano G, Berto F. Fatigue assessment of common welded joints by
means of the Strain Energy Density method. (Engineering Structures, Under review)
SED Comparison with:
 Eurocode 3
 British Standard
 IIW
 DNV-GL
1) Influence of intermediate plate
thickness
2) Influence of plate thickness
3) Scale effect 4) Lack of penetration: Probability of
failure
Prof. Filippo Berto

Research activity: Concluding Remarks
 Energy Methods reduce
 Time spent in testing and design
 Material amount to be tested
 Costs in R&D
 Energy Methods allow to
 Obtain reliable Fatigue data
compared to traditional tests
 S-N curve
 Fatigue limit
 Predict possible critical area of
fracture in mechanical
components and structures
Thermographic
Method (TM)
[~ 4-5 h]
&
Static Thermographic
Method (STM)
[~ 5 min]
Strain Energy Density
Approach (SED)
And…

Further development: Industrial applications
Universitat Politecnica de
Catalunya
Supervisor:
Prof. Esteban Codina Macia
(3 months)
Messina
Padova
Trondheim
Terrassa
Mr.
Pedro Roquet
Friction stir welding:
Rapid evaluation of the
fatigue life of the
weldings by TMs
Oleodynamic cylinder:
Crack danger by SED
method

Further development: FastFatigue Machine
In partnership
with
Patent Request
Compact Rapid Test
Machine for fatigue
properties evaluation
of materials
 Static tensile test -> Static Thermographic Method (STM)
 Fatigue test -> Thermographic Method (TM)
 Designed specifically for rapid fatigue assessment of Additive Materials

Ph.D. defence - Energy Methods for fracture and Fatigue assessment
University of Messina
Department of Engineering
Dario Santonocito
Thank you!!

PhD Defence Santonocito - Energy Methods for Fracture and Fatigue assessment

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