AIAS
Meeting Gruppo di Lavoro
Tecnologie di Giunzione
Vicenza, 27-28 Marzo 2008
Prof. Ing. Alessandro Pirondi
Università di Parma, Dipartimento di Ingegneria Industriale
OUTLINE
•
Adhesive bonding
- Academic Research
- Technology Transfer
- Education and Symposia
•
Welding
- Academic Research
- Education
•
Ongoing research and perspectives
eretta, Poli MI)
• Application
- Lightweight jib for long-distance concrete casting
- Structural adhesive (3M 9323 A/B) + woven grafite-epoxy laminate
• Flow-chart of the project
[Goglio, Rossetto, Dragoni, AIAS ‘02, Parma]
ADHESIVE BONDING: Research
OUTLINE
•Adhesives and environmental conditions considered
- Structural adhesives (Multibond 330, Hysol 9514, Hysol 9466)
- Adherends: construction steel or aluminum alloy
- Lab air
•Studies
- Fracture toughness, Fatigue Crack Growth (FCG)
(experimental)
- Fatigue strength and fatigue life prediction
(experimental)
- Failure simulation with a Cohesive Zone Model (CZM)
(numerical)
WHY FRACTURE...?
•Bonding technology faults, service conditions
•Literature survey
- About 100 papers collected spanning over the last 10 years
- Applications in: residual strength of joints with defects
fatigue life prediction
durability ranking (fitness-for-purpose)
FRACTURE AND FCG TESTS
DCB (Double Cantilever Beam)
P
teflon (s=0.05mm)
shims
h
t
h

a0 = 45 mm
W = 120 mm
h = 15 mm
t = 0.3 mm
b = 30 mm
a0
P
W
b
P
Tensile loading (Mode I)

Mixed Tensile-Shear
loading (Mixed-Mode I/II)
CTS
(Compact Tension-Shear)
FRACTURE AND FCG TESTS
•Qualifying points of the research (non-conventional features)
- Automated crack length evaluation from compliance measurement
- Fracture toughness correction to account for elasticity of the
adhesive layer
- Mixed-Mode I/II conditions
•Outcomes
- 3 peer-reviewed papers on international journals + 1 submitted
- several national and international conferences
•Exploitation of the results
- Testing procedures
- Fatigue life prediction methodology
FATIGUE TESTS
•Clip-gages
(compliance monitoring=crack length
evolution)
•Applied load
•Single-lap joint
FATIGUE TESTS: defect evolution
25
Crack length, a [mm]
20
a
a
15
10
5
steady-state
accelerating
0
0
20000
40000
60000
80000
Number of cycles
100000
120000
140000
FATIGUE TESTS: life prediction
- Time (cycles) to nucleate a defect negligible
- Time (cycles) to propagate to rupture (Nf):
Nf  
ac
da
C G m
L W
ac 
2
a0  ( possible ) initial crack
a0
b
rupture
L
da
 C G m
dN
G  f  Pmax  Pmin ,a 
C,m  adhesive properties
from FCG tests
FATIGUE TESTS: life prediction
•Example: Hysol 9514 single-lap joint
6
Average Shear Stress [Mpa]
5
4
3
2
1
Pred. 60mm
exp 60mm
Pred. 80mm
exp 40mm
exp 80mm
Pred. 40mm
0
1000
10000
100000
Cycles to failure, Nf
1000000
10000000
SIMULATION: cohesive zone model
•Concept
(from: Hutchinson, Evans, Acta Mater. 48, 2000, 125-135 )
Adherend contribution
to peel strength
Adhesive contribution
to peel strength
SIMULATION: cohesive zone model
•Use
- Calibration of parameters on (standard) fracture tests
- Simulation of failure of different geometries
•Advantages
- Efficient way to model potentially failing interfaces, including
adhesive joints
- Model transferability (not to be tuned case-by-case)
•Potential applications
- Structural joints static and fatigue failure
- Composites static and fatigue delamination
- Impact delamination (shock absorbers, car bodies, ...)
- Peeling of flexible laminates
- ...
CZM SIMULATION: example
•T-peel test: CZM calibrated on DCB fracture test (Multibond 330)*
800
700
600
Load (N)
500
Experiment
Simulation
400
300
200
100
0
0.00
0.50
1.00
1.50
Displacement (mm)
Courtesy Prof. M. Rossetto, Politechnic of Turin, Italy
2.00
2.50
3.00
ADHESIVE BONDING: Technology
Transfer
Plate heat exchanger
•Current solution
•AISI 316L stainless steel
•Brazing
•Max pressure 15bar
•Max temperature 70°C
•Overall cost: 11.5€
•Cost of brazing: 4.25€ (37% tot.!)
Adhesive bonding ?
•Proposed solution
•Bolt(s) to sustain loading
•MS adhesive for sealing
•Overall cost 25% lower !
Wall decoration preassembled patches
•Current solution
•2x2cm2  10x10cm2 tesseras
•Patch: 45x90cm2
•Preassembly system: adhesive dots on the back
•Current adhesive solution: plastisol (single-component)
highly flexibile
low cost
cure time 15’ at 190°C
•Wear of anti-sticking coating
alternative ?
•Energy (heating) costs
•Proposed solution
•Two-component, high-flexibility adhesive (developed specifically by Henkel)
•Cure time 20’ at room temperature
•Higher adhesive cost
•No energy costs for heating
•Compactness of the new process line (no oven)
Wall decoration preassembled patches
- Polimerization tower (20’ storage capacity)
•Engineering
- Two-component adhesive dispenser
Component A injectors
Component B injectors
Railway track joint (RFI-Henkel)
•Application
- Sustained loading conditions
- High average shear stress
•Sustained loading testing
Creep
Composite joint design (project driven
by S. Beretta, Poli MI)
• Application
- Lightweight jib for long-distance concrete casting
- Structural adhesive (3M 9323 A/B) + woven grafite-epoxy laminate
• Flow-chart of the project
[Goglio, Rossetto, Dragoni, AIAS ‘02, Parma]
ADHESIVE BONDING: education
EDUCATION
• Academic
- Seminars
- Viscoelastic behaviour (polymers in general, about 6h)
• On-the-job and collective courses
- “Simulazione ad elementi finiti di giunzioni incollate”.
8h, Dallara Automobili, Parma
- “TECNOLOGIE DI GIUNZIONE NON TRADIZIONALI:
INCOLLAGGIO E FRICTION STIR WELDING”. 4h, CISITA, Parma.
- “GIUNZIONI/COLLEGAMENTI”. Corso di Alta Formazione “Materiali,
Progettazione e Innovazione di Prodotto”, UNIVERSITA’ DI PARMA
- “ESEMPI APPLICATIVI DEL METODO DEGLI ELEMENTI FINITI:
CONTATTO, ASSEMBLAGGIO, GIUNZIONI”. Corso di Formazione
“Gli Elementi Finiti nella Progettazione Meccanica”, CSPMI, Reggio E.
• Symposia
- Yearly Henkel-Loctite workshop, 2000, 2005
• Progetto 2007
2° posto in classe 3
• Progetto 2008
• Utilizzo di materiali compositi (fibra di carbonio-resina epossidica)
• Utilizzo di incollaggi
• Motore semiportante
WELDING: research
OUTLINE
•Joints and environmental conditions considered
- Friction Stir Welded joints
- Materials: aluminum alloy, aluminum
alloy matrix composite
- Lab air
•Studies
- Fracture toughness, Fatigue Crack Growth (FCG)
(experimental)
- Fatigue strength and fatigue life prediction
(experimental)
- Residual strength prediction
(numerical)
FRACTURE AND FCG TESTS
- Al/Al2O3 butt joints
C*  
d
dP
a  f (C * )
FRACTURE AND FCG TESTS
•Qualifying points of the research (non-conventional features)
- FSW applied to Al/Al2O3 particulate composites
- Automated crack length evaluation from compliance measurement
- Crack closure evaluation and analysis
- Crack path evaluation
•Outcomes
- 2 peer-reviewed papers on international journals (under re-review)
- several national and international conferences
•Exploitation of the results
- Testing procedures
- Joining technique qualification
FATIGUE TESTS
- Al overlap joints
FATIGUE TESTS: defect evolution
and life prediction
Experimental
Nasgro model-threshold 2,7 MPa*m^0.5
Nasgro early mode II propagation: 200 microns
Nasgro early mode II propagation: 100 microns
60
s MPa
50
40
30
20
10
1,00E+04
1,00E+05
1,00E+06
1,00E+07
Number of cycles (N)
1,00E+08
RESIDUAL STRENGTH PREDICTION
Transferability Kahn tear test  large M(T) panels
Al-alloy FSW butt joint
1:50 scale (in-plane)
CTOA
F
Keff
COD
Δa
WELDING: education
• Academic
- Seminars
- Overview of weldability and design (about 10h)
• On-the-job and collective courses
- “Simulazione ad elementi finiti di giunzioni saldate”.
8h, Dallara Automobili, Parma
- “TECNOLOGIE DI GIUNZIONE NON TRADIZIONALI:
INCOLLAGGIO E FRICTION STIR WELDING”. 4h, CISITA, Parma.
- “GIUNZIONI/COLLEGAMENTI”. 4h. Corso di Alta Formazione “Materiali,
Progettazione e Innovazione di Prodotto”, UNIVERSITA’ DI PARMA
- “ESEMPI APPLICATIVI DEL METODO DEGLI ELEMENTI FINITI:
CONTATTO, ASSEMBLAGGIO, GIUNZIONI”. 8h. Corso di Formazione
“Gli Elementi Finiti nella Progettazione Meccanica”, CSPMI, Reggio E.
ONGOING RESEARCH AND
PERSPECTIVES
HYBRID JOINTS
• Origin: PhD student stage at Henkel
• Typologies of hybrid joints considered
- Weldbonded (spot); Ultrasonic weldbonded (spot); rivetbonded; clinchbonded
- Al/Al; Fe/Fe; Al/Fe (non weldbonded) + structural adhesive
- Overlap joint
• Program
Literature research
Market analysis
Testing parameters (DoE from market analysis)
Manufacturing
Testing / FE simulation
Influence of parameters
Design guidelines
HYBRID JOINTS
-Ultrasonic weldbonding prel. results (joints manufactured at Poli MI)
Strutturale
Solo spotweld ultrasonico
Ibrido con strutturale
Ibrido con frenafiletti
Ibrido con retainer
Retainer
HYBRID JOINTS
Rivetbonding damage and failure simulation
HYBRID JOINTS
(da letteratura)
Clinchbonding damage and failure simulation
SELF-HEALING
?
That’s all Folks!
COLLABORATIONS
- Prof. Gianni Nicoletto
- Ing. David Fersini
- Ing. Fabrizio Moroni
- Ing. Matteo Vettori
- Dr. Pierfranco Mauri
- Dr. L.M. Volpone
- Ing. C. Dalle Donne
- ....