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<TD BGCOLOR="#003300" align=center> <FONT COLOR="#ffffcze" SIZE=+1><B> Engine
Blocks (Ford Zetec 2.0)</B></FONT><BR>
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<TD><FONT COLOR="#000000"><B><I>Objective</I></B></FONT> <IMG SRC="grafisch/dot.gif" HEIGHT=3 WIDTH=1><BR>
<P>In the continiously innovating technology inside the automobile industry
tendency is set to lighter engines.To compeet with the aluminium industry,
the production of cast iron engineblocks following the Compacted Graphite
Iron process is investigated. In this type of grey cast iron the graphite
has a structure in between the classic structures: flake iron and nodular
iron. CGI combines the properties of both types:</P>
<UL>
<LI>good mechanical properties
<LI>castability
<LI>good transfer of heat
<LI>good damping properties
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<IMG SRC="grafisch/dot.gif" HEIGHT=1 WIDTH=1>
<P>However the CGI process lays between very strict tolerances which forces
the need of a qualitycontrole of the process and end-product. IMCE has
together with a German cast iron foundry investigated how the impuls excitation
measurement can be a helpful tool to examine the quality of an engineblock.</P>
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<TD><FONT COLOR="#000000"><B><I>Methodology</I></B></FONT> <IMG SRC="grafisch/dot.gif" HEIGHT=3 WIDTH=1><BR>
<P>In the study several engineblocks (type Ford Zetec 2.0) were investigated
performing impuls excitations on the cylinders. The response was measured
using microphones. The goal was to find a correlation between the measured
responses and their graphitestructure. To achieve this correlation a classificationmodel
is set up. To built this model one has to measure a set of engineblocks
(trainingsset) that covers the whole range of possible graphite structures
(from 100% nodularity to 100% flake iron)<BR>
The model was built with the Fuzzy Clustering method. This method finds
clusters in the featurespace. In this space all measured objects are represented
by specific features extracted from their responses. Each cluster or class
represents a certain graphitestructure present in the measured trainingsset.
As a result we get for each object the membership of that object to each
class.</P>
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<TD><FONT COLOR="#000000"><B><I>Results</I></B></FONT> <IMG SRC="grafisch/dot.gif" HEIGHT=3 WIDTH=1><BR>
<P>As a result of the study a classification model was built using 7 classes
ranging from 100% nodular iron to 100% flake iron with three subclasses
in the CGI range. CGI1 tends to nodular iron, CGI 3 to flake iron. </P>
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<FONT COLOR="#ffffcze" SIZE=+1><B>Oxide ceramics</B></FONT><BR>
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<P>A polycrystalline Al<SUB>2</SUB>O<SUB>3</SUB> specimen (size 83<B> </B>* 12.5
* 3 mm<SUP>3</SUP>, weight 9.3g) was tested. Alumina is highly oxidation
resistant, and can be sintered without sintering additives. FIG. 1 shows
the evolution of both resonance frequency (and E-modulus) and internal
friction from room temperature to 1500°C.</P>
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<TD align=center><IMG SRC="grafisch/g024.gif" HEIGHT=270 WIDTH=370 alt="impulse excitation measurement"></TD>
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<P>It is known from literature that no sudden changes in both <I>f<SUB>r</sub></I> or <I>Q<SUP>-1</sup></I> of a pure Al<SUB>2</SUB>O<SUB>3</SUB> occur at temperatures below 1000°C. Above this temperature the grain boundary defects become mobile, and minor secondary phases soften. This leads to the increase of <I>Q<SUP>-1 </sup></I>and a corresponding decrease in <I>f<SUB>r</sub></I>, which is confirmed fully by the results presented in FIG. 1. Above a certain <I>Q<SUP>-1</sup></I> (6 %), the vibration amplitude decreases too fast to allow accurate analysis. This is close to the 10% level above which the anelastic assumptions required to calculate <I>Q<SUP>-1</sup></I> from the vibration amplitude decay, are not valid anymore.</P>
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<P>Also two industrial types of polycrystalline zirconia ZrO<SUB>2</SUB> were tested in air.<BR>
First a partially stabilized ZrO<SUB>2 </SUB> with 2.7% MgO specimen was tested up to 1400°C. The phase transformation from the monocline phase to the tetragonal phase can clearly be seen at about 1000°C during the heating cycle. During the cooling down, the reverse phase transformation from tetragonal to monocline has a very sharp reading on the frequency.</P>
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<TD align=center><IMG SRC="grafisch/g025.gif" HEIGHT=270 WIDTH=370 alt="RFDA measurement"></TD>
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<P> The damping behavior of zirconias is much more complex than this of alumina, since the crystal lattice of zirconia contains many defects (both oxygen vacancies and interstitials of stabilizing atoms like Y<SUP>3+</SUP> or Mg<SUP>2+</SUP>). Pairs of oxygen vacancies and substitutional ions constitute elastic dipoles, which reorient under applied stress. The motions of these pairs and larger agglomerates is thermally activated and well defined, which explains the sudden decreases in <I>f<SUB>t</sub></I> and sharp Q<SUP>-1 </SUP>peaks in the corresponding temperature scans (FIG. 3). </P>
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<FONT COLOR="#ffffcze" SIZE=+1><B>Non-oxide ceramics</B></FONT><BR>
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<P>Silicon nitride is a structural ceramic, like alumina, but cannot be sintered to full density without sintering additives, unlike alumina. Therefor dense sintered Si<SUB>3</SUB>N<SUB>4</SUB> contains a secondary, intergranular phase. This phase is (partially) amorphous, and softens above its glass transition temperature (typically around temperatures of 1000°C). This gives rise to an increased viscous component in the deformation of the bulk ceramic, and consequently an increase in damping. At temperatures too far above the glass transition temperature, the secondary phase does not resist the deformation anymore, and less energy is dissipated. Further deformation is blocked by the rigid Si<SUB>3</SUB>N<SUB>4</SUB>-grains. When the temperature is increased even more, other diffusion type of deformations start playing a role, and Q<SUP>-1 </SUP>increases again. This well-known behavior does perfectly correspond to the data presented in FIG. 4.
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<TD align=center><IMG SRC="grafisch/g027.gif" HEIGHT=270 WIDTH=370 alt="young's modulus and damping measurement"></TD>
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<P>Depending on the heating rate, and the maximum temperature, the damping peak near the glass transition temperature is substantially reduced. The same Si<SUB>3</SUB>N<SUB>4</SUB> was tested in a torsion-pendulum, and uniaxially. Whereas the high-amplitude uniaxial results demonstrate a severe stress amplitude dependence, a good correspondence between the stress amplitude independent damping measured by the torsion pendulum, and the impulse excitation results is noted.</P>
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<FONT COLOR="#ffffcze" SIZE=+1><B>slate</B></FONT><BR>
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<P>Example of IET measurement : Effect of a temperature-cycle on slate<BR>Dr. K. Van den Abeele, civil engineering, K.U.Leuven</P></TD>
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<P>Measurements done at : K.U. Leuven, Department of Metallurgy and Materials Engineering</P>
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<TD BGCOLOR="#003300" align=center> <FONT COLOR="#ffffcze" SIZE=+1><B>glass</B></FONT><BR>
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<TD> <IMG SRC="grafisch/dot.gif" HEIGHT=3 WIDTH=1><BR>
<P>Example of IET measurement : Fully amorphous, glass materials Young’s
Modulus vs. Temperature</P>
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<p><IMG SRC="grafisch/g044.gif" HEIGHT=317 WIDTH=379></p>
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<P>Measurements done at : K.U. Leuven, Department of Metallurgy and Materials
Engineering</P>
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<td bgcolor="#003300" align=center> <font color="#ffffcze" size=+1><b>Epoxy
Coating</b></font><br>
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<td height="77"><font color="#000000"><b><i>Example of IET measurement : Freshly
mixed 2-component epoxy coating 0.125 mm thick applied onto a stainless
steel substrate (1 mm)</i></b></font> <img src="grafisch/dot.gif" height=3 width=1><br>
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<td><img src="grafisch/g046.gif" width="590" height="360" alt="Impulse excitation measurement">
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<p>Measurements done at : K.U. Leuven, Department of Metallurgy and Materials
Engineering</p>
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