Biomedical Engineering Reference
In-Depth Information
Figure 8.3
Example CFD of fluid flowing in a convergent-divergent pipe: (a) solid model; (b) CFD mesh;
(c) input/output constraints; (d) predicted pressure profile; (e) predicted velocity streamlines.
(Performed using CFX in ANSYS)
8.5.1 Formalizing the Selection Process
Selecting a material is not a simple task. It is difficult, complex, and requires justification.
Hence it is advisable to use a similar pro forma to that presented for design calculations.
Figure 8.4 illustrates a typical pro forma. If completed fully, it is able to go into the DHF
directly. As with other such pro forma, additional sheets are of course possible.
8.5.2 PDS
Hopefully your first port of call, the PDS, will give you some pointers, if not the material
itself. If not it will certainly have given you the design constraints to go into your materials
selection pro forma.
8.5.3 Precedent
Do you remember way back in Chapter 2 I introduced the idea that finding the classification
for your device can be made easier by finding a precedent? The same applies to materials. If
your device is similar to that of someone else, and that device is in common use, then does
it not make sense to start with that material? Of course, in some circumstances the company
will keep material data confidential, but in most cases it is easy to find. Be sure to check,
however, that there are no outstanding recalls!
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