Master Thesis - OUFTI-1

In our case, only the SMT and heavy components will be included in the FE model of
the OBC 2 card. The light components, due to their negligible eect on the stiness and
mass properties of the PCB, will not be modeled in any application. The Catia modeling
of the OBC 2 card is presented in Figure 4.13.
Figure 4.13: Catia modeling of the OBC 2 card
To take into account the mass contributions of these components on the OBC 2 response,
the methods exposed in section 4.2.5 will be applied one by one. Thus, the accuracy
of each of them will be discussed, based on experimental results obtained through the
test that will be presented in section 4.3.3.
The stiness contributions will not be included in FE models for several reasons:
• First, the datasheets provided with most electronic components, do not contain this
information.
• Then, realizing a static bend test on each component is too expensive with regard to
the expected results.
• Finally, as already mentioned, ignoring the stiness is a conservative approach. So,
the natural frequencies that will be obtained, will be lower than the real ones. This
fact is not critical in our case because, in general, LV manuals specify minimum
values for the payload natural (fundamental) frequency of vibration in order to avoid
dynamic coupling between low frequency dynamics of the LV and payload modes.
So, if the natural frequencies obtained using this method fulll the requirements, the
real ones will automatically fulll these requirements. An example of this type of
requirement is presented in Figure 4.14.
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