substructuring and frequency clustering

To whom it may concern,

 

I am writing my bachelor thesis at STADLER Pankow (a client of yours). 

The goal is to conduct a Harmonic analysis (direct frequency response) on an attachement part of a train wagon. 

A modal analysis was  already conducted, therefore possible frequencies of interest are already known. 

 

I have two issues at the moment:

 

1. the card freq3 offers the possibility to achieve a frequency clustering when approaching a eigenfrequency, the problem is that the documentation of optistruct states that it is only allowed in a modal analysis and not in direct frequency response. Is there no possibility to do a clustering in a direct frequency response? if yes I would be grateful if a someone could explain that to me. 

 

2. the rail car body is vital in order to achieve a realistic stiffness, the problem is that it increase dramatically the calculation time. A valid method to solve this issue is to apply SUBSTRUCTURING. This would statically compress all the nodes of the rail car body, holding the stiffness but reducing the calculation time. I have consulted all the documentation of Optistruct, there is no tutorail on how to achieve that. I am in need of a step-by-step guide on how to carry out this procedure. 

 

I would really appreciate a promt answer and I am confident you can help me out. 

 

best regards 

Andrea Torcianti