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50 | ACCESS
in
ACTION | MAY 2012
ACCESS in ACTION
necessary for the detecting transducer
to be near the source of AE. The elastic
waves generated as the material fractures
or deforms under stress can be detected
at a distance from their point of origin.
This means that the whole FRP structure
‘Monitoring Integrity of FRP booms on EWPs’...
continued from p48
Figure 2: Deformation mechanisms in fibre composites
(surface and sub-surface)
can be tested in a single
examination that usually
takes just a few hours.
The other advantage of
AE is that it offers the
opportunity for continuous
surveillance under a
variety of environmental
conditions should it be
required.
Potential interference
from background noise can
be problematic without
filtering interference.
Operating in the frequency
range of 20kHz -100kHz,
background noise in
this range is removed
electronically by a band pass
filter within the AE system.
An AE event is a pulse of energy
generated when a material is stressed. This
pulse of mechanical energy is converted to
an electrical signal, amplified and filtered
for processing.
FRP is a copious emitter of AE, the
three sources being cracking of the resin
matrix, debonding between the matrix and
fracture of the fibres, and fibre failure. Each
type of failure has been characterised by
the amplitude of the AE associated with
it and hence can be isolated. Emissions
for fibre failure (the most critical in terms
of strength) have the highest amplitude.
Like most materials, FRP exhibits the
Kaiser Effect whereby no AE occurs until
the applied stress exceeds the previous
highest stress. Essentially, this means that
in order to account for the Kaiser Effect,
AE tests always require a minimum of two
load applications to the same load level.
A boom’s pass or fail will be determined
by the ratio of the first load to the second
load at the point where the AE reaches a
predetermined rate.
For more information on Acoustic
Emission testing contact ATTAR (Advanced
Technology Testing Research) on:
03 9574 6144 or davidlake@attar.com.au
HR
Octopussy “Twin Series” self-propelled
tracked platforms now distributed by
Aerial Access Australia are available in two
sizes, the ‘1412 Twin’ and the ‘1715 Twin’,
working heights of 14m and 17m with a
platform capacity of 120kg or 200kg.
Both platforms are compact when
transporting and in confined areas, and can
fit though an opening of 850mm wide.
The Octopussy is also available as an
option with non-marking tracks expanding
the versatility on tiles, marble or granite
surfaces. As standard the machine operates
a maximum drive motion speed of 1.2km
per hour. Both machines are economical
with an option for independent Honda
petrol or a Lombardini diesel engine and
come with a built in electric motor for use
in indoor applications minimising toxic
fumes for exhausts.
Geometrical features allow the machine
to select load limits automatically and select
work area limits suitable for the load to be
lifted. For example: to raise a single man
at 17m working height the platform limits
to 120kgs with a side reach of 6.8m and
to raise the platform with two men, the
platform will limit the machine to 15.2m
with a side reach of 5.2m with rotation up
to 350degrees.
Octopussy “Twin Series” tracked platforms
Aerial Access has launched the Octopussy “Twin Series” self-propelled tracked platforms
Aerial Access Australia is associated with
Oil & Steel (European manufacturers of
ewps) and offers Octopussy track mounted
ewps in the Classic, Evo, Twin & 2190 Series.
For more information, contact: 1300 654
591 or visit: www.aerialaccess.com.au
HR