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The
Al-Fin bond is a bond between an aluminium alloy and a ferrous metal.
The actual bond area is an alloy of iron and aluminium that has
an intermediate chemical composition, of approximately FeAl3;
it is this area that is to be inspected. In diesel engine piston,
this Al-fin process is used to bond an iron insert in the position
where the top piston ring groove will be machined. This is necessary
because of the high compression ratio of a diesel engine, compared
to that of a gasoline engine and therefore the stress on the top
ring groove is that much greater. This piston inspection software
provides the capability of inspecting the Al-Fin bond using ultrasonic
instrumentation.
Inspection
of top, bottom bonds using pulse echo of through transmission
Inspection
of back bonds and crater cracks
Measurement
of oil cooling gallery position
Cummins
approved automatic threshold algorithm
Has
operator and supervisor modes or operation
Applies
an automatic gage R&R procedure to ensure system calibration
traceability
Supports
up to 8 ultrasonic channels
The
piston inspection software, allows the use of up to 8 Ultrasonic
channels, to test different features associated with diesel engine
pistons, which have an Al-Fin bonded iron insert or oil cooling
gallery.
The
main screen has a number of tab pages, which allow viewing of the
data for the desired feature and the setting of the user defined
acceptance parameters for that feature. The system has a nominal
resolution of 0.05% of the piston circumference, but displays the
results to 0.1%.
Bond
Inspection
This
software allows for the inspection of the Top, Bottom and Back bonds
simultaneously. Also more than one channel may be inspecting the
same bond to ensure that as much of the bond area is covered as
possible.
The result of an inspection is displayed as a strip chart with the
defect length calculated as a percentage of the piston circumference,
as shown on the front of this brochure and in the form of a C-Scan.
Each
line in the C-Scan image is a different channel; therefore in the
above case there are 3 channels assigned to the Top bond inspection,
2 channels for the Bottom bond inspection and a single channel for
the Back bond inspection.
Gallery Inspection
In
addition to the bond inspection the software allows for the measurement
of the gallery position. The results of these measurements are shown
on a strip chart for channels that have been assigned to the Crown
or Skirt Gallery measurements and in the form of a C-Scan.
The
gallery position measurement is compared to the user defined tolerance,
also shown on the strip chart; the area outside this tolerance band
is calculated as a percentage of the piston circumference and also
displayed.
Automatic
Threshold
The
automatic threshold algorithm calculates the threshold to be applied
to data from each of the channels not assigned to the gallery position
measurement.
It is entirely possible that different threshold levels will result
for different channels, since the threshold itself is based on the
data set for its respective channel. This has obvious advantages
over the traditional fixed threshold approach. In that the sensitivity
on each channel is constant and independent of the ultrasonic Instrument
gain for that channel. Therefore, it essentially eliminates errors
due to incorrect setting of the Ultrasonic Instrument by an operator.
In
piston inspection systems it is possible to get different effects
on the raw data captured from the Ultrasonic Instrument, it is made
up of two frequency components.
A
low frequency component normally associated with the tilt of the
iron insert. The chart below shows this low frequency effect, where
the raw data signal is cyclic in nature for 360o rotation
of the piston. And a high frequency component, which results in
the signal randomly, fluctuating.
The
chart below illustrates this high frequency fluctuation, on a typical
piston.
The
chart below shows the result of applying the algorithm to the first
chart above. It shows both the low and high frequency components
being removed and a threshold of 52.4% calculated.
FOR
MORE INFORMATION PLEASE SEE: STATISTICAL
PROCESS CONTROL APPLIED TO AUTOMATIC ULTRASONIC INSPECTION (pdf
format) from our Technical Papers Library
To obtain this
information as an Adobe Acrobat document Click
Here.
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