allowable stress for bolt

[arbor]

I am using FEA to analyze the bolts of a plate heat exchanger based on the elastic stress analysis in Section VIII, Div 2. The loads include preload, pressure and thermal. 90% of the total stress is due to the operating pressure. I did the stress linearization for the bolts. The membrane stress in the bolt produced by the combined load is below the allowable, S. However, the bending stress is so high that the membrane+bending stress is in the range of 1.5-2S. Can I use 2.7S as the allowable stress according to 5.1.3.3? Could any code expert here advise? Thank you very much.

Arbor

 

[SnTMan]

This is not really be best area, but membrane stress in a bolt?

Regards,

Mike

 

[metengr]

arbor;
Why would there be a bending stress in a joint under preload? Tension and shear loads, yes, I can understand, but bending loads?

 

[arbor]

metengr:

In a plate heat exchanger, stacked heat transfering plates are placed between two thicker end plates/frames. The bolts connect the two frames to hold the entire structure. The frames will bend under pressure which is similar as the rotation of bolted flange. The deformation of the frames will exert rotation/bending on the bolts and cause bending stress in the bolt. Hope I've exlpained it clearly. Thank you,

Arbor