Socket Analysis 1

[feajob]

Hi Guys,

Do you consider combined stress analysis for a socket analysis? or you check only bursting or bearing stresses separately?

Thanks,
A.A.Y.

 

[SWComposites]

Socket? Please describe in detail.

 

[feajob]

I would like to do stress analysis in the attachment regions of the Main Fitting Main (or Nose) Landing Gear. Landing Gears are attached to Aircraft or Helicopter Structure with Attachment Pins. In Some Stress Manuals, they talk about Beam (or pin) in a socket.

You can get some ideas by checking Figure 4 of the following link:

http://www.mscsoftware.com/events/v...ull_papers/2004-003-FP_sousa_rodolfo_tréz.pdf

Presentation Title: A Landing Gear FEM Analysis Using MSC.Patran ...

Upper regions of this Main Fitting can be considered and analysed by a socket analysis.

Thanks,
A.A.Y.

 

[jetmaker]

feajob,

For the socket analyses I have done in the past, the socket is checked for hoop burst at the ends when a peaking factor is applied. A bearing check is then made using the segmented socket load applied over it's contact area.

I assume you are using a sinusoidal load distribution within the socket... is that correct? My applications all used bushings installed in the socket, so bearing checks were made against the bushing and the housing.

jetmaker

 

[feajob]

Jetmaker,

Thank you for your response. Yes, I am using sinusoidal (cosine) load distribution along the socket length.

I also noticed that in some of our previous projects my former colleagues did socket analysis with hoop burst and bearing checks individually. But, from my viewpoint, we should deal with a combined stress M.S. calculation. I think that if we neglect the shear and bending stresses then we are not conservative. By applying the sinusoidal (cosine) load distribution along my socket interfaces in FEM, I also obtained noticeable hot spots.

I am not sure, may be there is a better agreement between experimental results (ultimate static tests) and checking hoop burst and bearing. I don't know?

If you guys have any experience with real tests for socket structures then I appreciate to know your feedback.

A.A.Y.

 

[jetmaker]

feajob,

What shear and bending stresses are you refering to? Are you refering to the bending stress along the length of the socket and the shear flow developed due to bending?

The only thing I can correlate these socket analyses to is a lug analysis. You do not use a combined stress for lugs; however, the data is based on tests and uses correlation factors.

 

[feajob]

Jetmaker,

Yes, I am referring to the bending stress along the socket and the shear flow due to bending.

BTW, I also saw some lug analysis for socket structures in stress reports.

Well, I guess that using combined stress M.S. for socket analysis is too much conservative. On the other hand, may be doing separate checks for bearing and burst is non-conservative. Note that, both stresses are at the same location with different directions (similar to a thick pressure vessel).



A.A.Y.

 

[jetmaker]

feajob,

Thinking about it, I do not know if I would say the socket is actually bending. If the socket is short enough in length, then it is not able to react the moment within itself and relies upon the connection of the socket to the supporting structure to do so. The socket is simply seeing a variation in radial load.

I still need to think about the shear aspect of the question.

jetmaker

 

[feajob]

Thanks Jetmaker. I am agreeing with you about bending issue. As I mentioned before, I don't know if we can neglect completely the interaction between (radial) bearing stress and (circumferential) hoop burst stress or we should at least assume some percentages of the interaction between these two stresses.

A.A.Y.

 

[jetmaker]

feajob,

The bearing stress is like the radial stress in a pressure vessel, gradually decreasing to zero at the outside free edge. You might want to check a pressure vessel manual to see how they treat the combination of radial and hoop stress.

Do not forget to include the residual stresses caused by the interference fit of the bushing in the socket housing.

jetmaker

 

[feajob]

Thanks Jetmaker, it is a good point. I will check a pressure vessel handbook.

Yes, I did consider the press fit stress, but I don't multiply this stress by 1.5 for ultimate M.S. calculation.

A.A.Y.