Landing Gear FEA using Sol 106

[Jet-Eng]

Hi

I am modeling a transport aircraft's main landing gear in MSC Nastran. The goal of the analysis is computation of internal loads of the MLG components (such as shock absorber, struts, braces) which will be used for detailed FEA of the components. The model is created using beam and bars for strut and braces and CBUSH1D and PBUSH1D (Input Type for spring: Table) is used for the shock absorber. Since the shock absorber stroke is about 30 cm (large displacement), Static non-linear solution 106 is used. When I analyzed the results, some elements forces and stress seems to be wrong. I reviewed the Nastran guides and help docs, for guidelines about modeling large displacement problems and also for shock absorbers, but nothing found. I have also searched the web, with no helpful results.

1- First of all, is this strategy (One model for internal load calculations and multiple separated models for detailed analysis) is a reasonable strategy?
2- Is the selection of Sol 106 is suitable for this kind of problems? Which other solution is more accurate than Sol 106?
3- Is modeling of shock absorber using CBUSH1D is a reasonable practice? Which other element can be used?
4- Can anybody provide some information about this type of problems?

Thanks.

 

[WKTaylor]

SH...

Has Your landing gear already been analyzed using hand calculations in a classical Landing gear external/internal-loads and stress Analysis report?

That analysis might shed light on what You are seeing/not-seeing in the FEM.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[Jet-Eng]

WKTaylor, Thanks for your response.

SH...

Has Your landing gear already been analyzed using hand calculations in a classical Landing gear external/internal-loads and stress Analysis report?

That analysis might shed light on what You are seeing/not-seeing in the FEM.

Yes, the landing gear preliminary stress report exist, and the FEM results showing significant differences with the existing results.

The landing gear overall configuration is similar to ATR-72's one. I think, the large deflections (due to shock absorber), is one of the primary sources of error.

 

[WKTaylor]

OK...

What about instrumented static and dynamic test results? How do they match/not-match the original hand analysis, and your FEM analysis, compare?

Any instrumented flight test data for similarity/comparison?

How are you accounting for the effects of fluid compressibility, tire elasticity and joint lubrication?



Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]