Bienvenue

1
New numerical and experimental approach for
mixed mode crack growth in wood by Mqv integral
Rostand Moutou Pitti, Frédéric Dubois, Christophe
Petit
Laboratory ()GEMH, University of
Limoges Egletons, France
() Heterogeneous Material Research Group Civil
Engineering and Durability Team
frederic.dubois_at_unilim.fr
2
New numerical and experimental approach for
mixed mode crack growth in wood by Mqv integral

• Scientific context
• 2MCG specimen
• Optimization by the Mq Integral
• Conclusions and perspectives

3
Scientific context

• Crack growth process during timber structure live

?
Crack propagation during creep loading
Crack process in joints

• Complex loading
• Viscoelastic behavior

?
Differed mixed mode configuration around the
crack tip
4
Scientific context

• Crack growth process parameters

Long term loading or creep effects Viscoelastic
effects Shrinkage/swelling effects Mechano-sorptiv
e effects
5
Scientific context

• Crack growth stability energy release rate
  approach

Stationary crack
Crack growth initiation
Time crack growth process caused by viscoelastic
effects
Crack growth stability
Crack growth instability
6
Scientific context

• Crack growth stability G / time representation

Energy release rate G
time t
7
Scientific context

• Crack growth stability G / crack length
  representation

Energy release rate G
Crack growth initiation
Viscoelastic energy
Crack length a
8
Mixed mode crack growth (2MCG) specimen

• DCB specimen Crack growth stability for open
  mode configuration

G
(N/mm)

2.5
Part 1
Part 3
Part 1
Part 3
Crack growth initiation
2.0
1.5
1.0
Stability
Crack growth instability
Part 2
0.5
0.0
30
40
50
60
70
80
90
100
Crack length (mm)
Elastic energy release rate
9
Mixed mode crack growth (2MCG) specimen

• CTS specimen Mixed mode configuration with
  instable crack growth

Steel arcans
Mixed mode for different ratios
10
Mixed mode crack growth (2MCG) specimen

• New 2MCG specimen crack growth stability for
  mixed mode configuration

(a) Stable DCB specimen
11
Optimization by the Mq Integral

• Formalism

y
1
x
1
W
12
Optimization by the Mq Integral

• Physical interpretation

13
Optimization by the Mq Integral

• Geometric optimization by the FEM

Energy concentration around the crack tip
14
Optimization by the Mq Integral

• Crack growth stabilization

Circular mesh around the crack tip
15
Optimization by the Mq Integral

• Crack growth stabilization

Virtual displacements for the Mq integral
Open mode
16
Optimization by the Mq Integral

• Crack growth stabilization

Virtual displacements for the Mq integral
Shear mode
17
Optimization by the Mq Integral

• Numerical results

Force orientation for different mixed mode ratios
18
Optimization by the Mq Integral

• Numerical results

pure mode I
mode I
19
Optimization by the Mq Integral

• Numerical results

pure mode II
mode I
20
Optimization by the Mq Integral

• Numerical results

mixed mode
b
mode I
21
Optimization by the Mq Integral

• Numerical results

mixed mode
b
mode I
22
and
Conclusions
perspectives

• Design of the 2MGC specimen
• Crack growth stability for mixed mode loadings
• Interpretation of viscoelastic effects on the
  crack growth process

• Experimental validations for crack growth
  stability
• Crack growth criterion for mixed mode fracture
• Crack growth tests for creep loadings

23
New numerical and experimental approach for
mixed mode crack growth in wood by Mqv integral
Rostand Moutou Pitti, Frédéric Dubois, Christophe
Petit
Thanks for your attention
Laboratory ()GEMH, University of
Limoges Egletons, France
() Heterogeneous Material Research Group Civil
Engineering and Durability Team
frederic.dubois_at_unilim.fr