Page 60 - Kutnar, Andreja, et al., eds., 2015. Proceedings of the 1st COST Action FP1307 International Conference - Life Cycle Assessment, EPDs, and modified wood. University of Primorska Press, Koper.
P. 60
lysis
of
neutral
axis
position
in
thermally
modified
wood
using
DIC
Václav
Sebera*1,
Martin
Brabec2,
Petr
Čermák3
,
Jan
Tippner4,
Jaromír
Milch5
Department
of
Wood
Science,
Faculty
of
Forestry
and
Wood
Technology,
Mendel
University
in
Brno,
Zemědělská
3,
613
00
Brno,
Czech
Republic,
e-‐mails:
1vaclav.sebera@mendelu.cz,
2martin.brabec@mendelu.cz,
3petr.cermak.und@mendelu.cz,
4jan.tippner@mendelu.cz,
5jaromir.milch@mendelu.cz
Keywords:
neutral
axis,
DIC,
thermal
modification,
bending
Thermally
modified
timber
(TMT)
has
been
long
recognized
as
an
efficient
and
eco-‐friendly
alternative
to
tropical
species
and
wood
treated
by
other
techniques.
Nevertheless,
the
range
of
feasible
applications
for
TMT
is
limited
by
undesired
side
effects,
such
as
reduction
of
mechanical
properties.
For
a
material,
it
is
important
to
know
the
location
of
the
neutral
axis
(NA).
The
NA
can
be
successfully
located
by
means
of
the
full-‐field
optical
techniques.
It
is
hypothesized
that
thermal
modification
affects
the
tensile
and
compressive
wood
stiffness
parallel
to
the
grain
on
a
different
level,
so
the
location
of
the
NA
changes.
Therefore,
this
paper
aims
to
obtain
the
full-‐
field
axial
strains
by
the
optical
technique
applying
the
principles
of
the
digital
image
correlation
(DIC)
for
the
NA
localization
in
thermally
modified
wood
loaded
by
the
three-‐point
bending.
The
samples
were
cut
from
untreated
and
differently
thermally
modified
(180
°C
and
200
°C)
wood
of
the
European
beech
(Fagus
sylvatica
L.)
as
clear
orthotropic
blocks
with
dimensions
of
14
mm
×
14
mm
x
210
mm
(radial
(R)
x
tangential
(T)
x
longitudinal
length
(L))
meeting
the
requirements
of
the
BS
373
(British
Standard
Institution
1957).
Before
the
sampling,
all
source
material
was
conditioned
in
a
climate
chamber
at
20
°C
and
65
%
relative
humidity
until
the
equilibrium
moisture
content
(EMC)
was
reached.
The
three-‐point
loading
of
the
samples
in
the
tangential
direction
was
carried
out
using
the
universal
testing
machine,
Zwick
Z050/TH
3A
equipped
with
a
50
kN
load
cell.
The
deformation
induced
in
the
samples
was
determined
by
the
full-‐field
optical
stereovision
system
consisting
of
two
CCD
cameras.
The
system
was
calibrated
to
an
area
of
interest
(AOI),
which
was
210
mm
×
14
mm.
The
images
were
captured
every
0.25
seconds
(4
Hz)
and
synchronized
with
the
applied
force.
The
strain
fields
at
the
AOI
from
the
partial
derivatives
of
the
displacement
using
Lagrange
notation
were
calculated
in
Vic-‐3D
(Correlated
Solutions
Inc.).
RESULTS
Fig.
1
shows
that
the
variation
in
the
zero
axial
strain
position
(i.e.,
NA
location)
within
the
sample
height
increased
as
the
distance
from
the
loading
point
at
the
midspan
increased.
This
is
48
of
neutral
axis
position
in
thermally
modified
wood
using
DIC
Václav
Sebera*1,
Martin
Brabec2,
Petr
Čermák3
,
Jan
Tippner4,
Jaromír
Milch5
Department
of
Wood
Science,
Faculty
of
Forestry
and
Wood
Technology,
Mendel
University
in
Brno,
Zemědělská
3,
613
00
Brno,
Czech
Republic,
e-‐mails:
1vaclav.sebera@mendelu.cz,
2martin.brabec@mendelu.cz,
3petr.cermak.und@mendelu.cz,
4jan.tippner@mendelu.cz,
5jaromir.milch@mendelu.cz
Keywords:
neutral
axis,
DIC,
thermal
modification,
bending
Thermally
modified
timber
(TMT)
has
been
long
recognized
as
an
efficient
and
eco-‐friendly
alternative
to
tropical
species
and
wood
treated
by
other
techniques.
Nevertheless,
the
range
of
feasible
applications
for
TMT
is
limited
by
undesired
side
effects,
such
as
reduction
of
mechanical
properties.
For
a
material,
it
is
important
to
know
the
location
of
the
neutral
axis
(NA).
The
NA
can
be
successfully
located
by
means
of
the
full-‐field
optical
techniques.
It
is
hypothesized
that
thermal
modification
affects
the
tensile
and
compressive
wood
stiffness
parallel
to
the
grain
on
a
different
level,
so
the
location
of
the
NA
changes.
Therefore,
this
paper
aims
to
obtain
the
full-‐
field
axial
strains
by
the
optical
technique
applying
the
principles
of
the
digital
image
correlation
(DIC)
for
the
NA
localization
in
thermally
modified
wood
loaded
by
the
three-‐point
bending.
The
samples
were
cut
from
untreated
and
differently
thermally
modified
(180
°C
and
200
°C)
wood
of
the
European
beech
(Fagus
sylvatica
L.)
as
clear
orthotropic
blocks
with
dimensions
of
14
mm
×
14
mm
x
210
mm
(radial
(R)
x
tangential
(T)
x
longitudinal
length
(L))
meeting
the
requirements
of
the
BS
373
(British
Standard
Institution
1957).
Before
the
sampling,
all
source
material
was
conditioned
in
a
climate
chamber
at
20
°C
and
65
%
relative
humidity
until
the
equilibrium
moisture
content
(EMC)
was
reached.
The
three-‐point
loading
of
the
samples
in
the
tangential
direction
was
carried
out
using
the
universal
testing
machine,
Zwick
Z050/TH
3A
equipped
with
a
50
kN
load
cell.
The
deformation
induced
in
the
samples
was
determined
by
the
full-‐field
optical
stereovision
system
consisting
of
two
CCD
cameras.
The
system
was
calibrated
to
an
area
of
interest
(AOI),
which
was
210
mm
×
14
mm.
The
images
were
captured
every
0.25
seconds
(4
Hz)
and
synchronized
with
the
applied
force.
The
strain
fields
at
the
AOI
from
the
partial
derivatives
of
the
displacement
using
Lagrange
notation
were
calculated
in
Vic-‐3D
(Correlated
Solutions
Inc.).
RESULTS
Fig.
1
shows
that
the
variation
in
the
zero
axial
strain
position
(i.e.,
NA
location)
within
the
sample
height
increased
as
the
distance
from
the
loading
point
at
the
midspan
increased.
This
is
48
