Failure point 1

[elogesh]

Hai,

I have a huge complex part made of cast-iron.

I carried out hydraulic burst test under static conditions.Same loading was simulated using FEM package.

The failure location in the experimental condition is different from that of FE reults(Maximum stress location).

When we relooked into the actual part, the failure location was occuring in the parting line. But in the FE model,the failure was not occuring anywhere around the parting line.

Therefore the query is whether the strength of casted part around the parting is usually weaker? If so How to attack this problem?

With Thanks and Regards,
Loganathan.E

 

[tld23]

Dear elogesh,
It is difficult to determin why there might me a difference between the Test and FEA without seeing the detail of what you have done. However consider the following:

1) Your model probably has isotropic homogenious material data. Castings are neither of these. Firstly it is not uncommon to have flaws (inclusions, cracks, pores) in castings. You may want to check for these in your test components. Even small flaws can be critical (see next section). Directional silidification can cause dendritic growth and elongated grains which makes the material anisotropic (CI sufferes from this less than some other materials).

2) Depending on the type, CI can be brittle and hence have sensitivity to small defects, or even cast features such as the flash at a misaligned parting line (although this would have to be severe for a significant effect).

3) Both of the above means that CI castings will be more variable in their strength than other more ductile materials. Therefore the failure will be statistical in nature. The next test may fail somewhere else.

4) You do not say what failure criteria you were using for the 'maximum stress location', but you may want to use the maximum principal stress rather than the more traditional von Mises.

5) All of what I have said above will depend on the type of material and casting. Flake CI will generally be brittle whereas SGCI will be much tougher.

Hope this helps
TERRY