3-D modeling of Fastener Connections

[aerohead56]

What is a good way to model fasteners in a fine grid Hex-element model?

 

[mloew]

aerohead56,

You will be interested in the following threads from this forum: [ul][li]Modelling Lap joint with HSFG Bolts In MSc NASTRAN (Thread727-48342) [/li][li]FE modelling of bolted connections (Thread727-32101)[/li][/ul]
You may be interested in these articles from the excellent magazine BENCHMark published by NAFEMS (

http://www.nafems.org):

[ul][li]FE Techniques for the Representation of Screw Threads (

http://nafems.org/publications/downloads/Screw.pdf)

October 2002[/li][li]Finite Element Techniques for the Representation of Screw Threads - Part II (

http://nafems.org/publications/downloads/screw2.pdf)

January 2003[/li][/ul]

Please become familiar with the search facility of this site; this is a previously asked question.


Best regards,

Matthew Ian Loew
"Luck is the residue of design."
Branch Rickey

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[mloew]

I have since found these resources:

A Closer Look at Bolted Joints
By John Crawford

http://206.210.94.185/techfile_text.html

2003-01-1594 Validation of a System of Finite Element Models Representing a Complex Transaxle
Paras M. Mehta, Sarav. Paramasivam, Kotha Reddy, David Popejoy
Ford Motor Company
Jerry Chung, Bill Steed
MTS Systems Corporation

http://www.mts.com/nvd/pdf/2003-01-1594_TransmissionFE_Correlation_Chung.pdf

BOLJAT - A Tool for Designing Composite Bolted Joints using Three-Dimensional Finite Element Analysis
G.S. Padhi, M.A. McCarthy, C.T. McCarthy
Composites Research Centre, Department of Mechanical and Aeronautical Engineering
University of Limerick, Limerick, Ireland

http://www.smr.ch/bojcas/Reports/ulim/ULIM_CompositesPartADec2002.pdf

Best regards,

Matthew Ian Loew
"Luck is the residue of design."
Branch Rickey

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[aerohead56]

Thank you for looking up these resources for me. There is a lot about modeling that the aerospace industry can learn from the auto industry. I think that I need to be a little more specific. I am modeling a thick, milled out fitting for an aircraft. Specifically I am looking for accurate fastener loads in the bolts that attach the fitting to the rest of the aircraft and stresses in the fitting pads that contain the bolt holes. Currently I am using an RBE3 to model this connection with the dependant node at the bottom surface of the part, farthest away from the loading point so I get the maximum reaction forces. The dependant nodes are connected with CELAS elements representing the bolt stiffness to coincident nodes to the RBE3 dependant nodes. I cannot take friction into account (not a standard practice in aircraft analysis). Due to the distribution of forces from the RBE3 there is an even amount of fastener shear going into the tension and compression sides of the hole. Also, it appears that more shear/tension is being transferred into the bottom of the hole than the top of the hole. I assume this is due to the position of the dependant node and the distance of the top independant nodes vs the bottom independant nodes to it. Due to the geometry of the part and the locations of the holes, it is very important that the fastener connections not be too stiff. This will result in an un-realistic load distribution in the part.