Bolted connections

[dorin.r.ghimpu]

Hello,

I have a brick model with several bolt connections, with and without nuts. I've input the surfaces and torque. Do I have to input contact between the 2 surfaces that are connected, as well? 

I've ran the model and after going thru all the parts brick elements, ending reaction computations and deleting temporary files I got this error (see below):

..............
**** PARTS REMAINING 12
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 29
THE 28th PART CONTAINING 7054 ELEMENTS
5600 (79.%) elements
4800 (68.%) elements
4000 (56.%) elements
3200 (45.%) elements
2400 (34.%) elements
1600 (23.%) elements
800 (11.%) elements
0 ( 0.%) elements

**** PARTS REMAINING 11
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 30
THE 29th PART CONTAINING 1460 ELEMENTS
0 ( 0.%) elements

**** PARTS REMAINING 10
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 31
THE 30th PART CONTAINING 992 ELEMENTS
0 ( 0.%) elements

**** PARTS REMAINING 9
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 32
THE 31th PART CONTAINING 1032 ELEMENTS
0 ( 0.%) elements

**** PARTS REMAINING 8
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 33
THE 32th PART CONTAINING 380 ELEMENTS

**** PARTS REMAINING 7
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 34
THE 33th PART CONTAINING 380 ELEMENTS

**** PARTS REMAINING 6
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 35
THE 34th PART CONTAINING 361 ELEMENTS

**** PARTS REMAINING 5
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 36
THE 35th PART CONTAINING 361 ELEMENTS

**** PARTS REMAINING 4
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 37
THE 36th PART CONTAINING 361 ELEMENTS

**** PARTS REMAINING 3
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 38
THE 37th PART CONTAINING 380 ELEMENTS

**** PARTS REMAINING 2
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 39
THE 38th PART CONTAINING 361 ELEMENTS

**** PARTS REMAINING 1
**** ELEMENT/GLOBAL CONTRIBUTIONS Part = 40
THE 39th PART CONTAINING 380 ELEMENTS

**** ENDING REACTION COMPUTATIONS

Processing completed ...

ds.t7 = 26778.109 kilobytes
ds.t8 = 53124.105 kilobytes
ds.t9 = 0.000 kilobytes
ds.t10 = 0.000 kilobytes
ds.t11 = 0.000 kilobytes
ds.t12 = 26777.789 kilobytes
ds.t13 = 26874.781 kilobytes
ds.t14 = 0.000 kilobytes
ds.t15 = 0.000 kilobytes
ds.t17 = 0.000 kilobytes
ds.t50 = 2196236.523 kilobytes
ds.t51 = 182562.531 kilobytes
ds.t52 = 3421179.086 kilobytes
ds.t54 = 13388.918 kilobytes
ds.t55 = 452772.824 kilobytes
ds.t56 = 905545.648 kilobytes
ds.t56 = 905545.648 kilobytes
ds.t58 = 0.000 kilobytes
ds.t59 = 0.000 kilobytes

total temporary disk storage (megabytes) = 8018.346

ds.l = 2836310.508 kilobytes
ds.do = 53124.047 kilobytes

**** BEGIN DELETING TEMPORARY FILES
**** TEMPORARY FILES DELETED
**** END OF SUCCESSFUL EXECUTION

**** Total actual hard disk space used = 10840.060 megabytes

Sub-total elapsed time = 41.801 minutes

Autodesk (R) Simulation Stress Calculation Utility
Version 2017.00.00.3131-W64/X64 10-Mar-2016
Copyright (c) 2016, Autodesk, Inc. All rights reserved.

DATE: FEBRUARY 17, 2020
TIME: 01:02 PM
INPUT......C:\Temp\MIT112W2201-6_-\MIT112W2201-6 with holes for screws.ds_data\1\ds

**** Model Unit System Settings:
--------------------------------------------
Unit System : English (in)
Force : lbf
Length : in
Time : s
Temperature (Absolute) : deg F (R)
Thermal Energy : in*lbf
Voltage : V
Current : A
Electrical Resistance : ohm
Mass : lbf*s^2/in
--------------------------------------------

**** Error: Found 3427557 NANs in displacement solution, quit
computing stresses.

It indicates model experienced difficulty in solving
displacements, please check boundary condition related
setting etc. The first incidence occured at,
node 1 Tx degree of freedom.

ERROR DETECTED - EXECUTION TERMINATED
This module elapsed time = 0.326E-03 minutes

The TOTAL elapsed time = 41.8 minutes

I believe this is due to the way I've set the bolted connections. I'm not familiar with this error. What should I focus on? Please, help me to clarify this.

Thank you much,

Dorin G.

[John_Holtz]

Hi Dorin,

Other than the message that indicates the analysis did not calculate proper displacements, there is nothing that can be determined from the output file. (NaN means Not a Number, as in the calculated displacements are not a valid number. Of course you know this because you looked at the displacement results in the Results environment and saw that the results were junk.)

I have a few questions to help determine what the problem is.

1. Why do you think the problem is with the bolts?
2. Do you want the two bolted surfaces to contact each other? If so, then you should define contact! (But what is the default contact? The two surfaces should have some type of contact established because of the default.)

I think the problem is with your material properties. Another possibility is that the model is missing constraints so that it is free to move as a rigid body in one of 6 directions (translation in X, Y, Z; rotation about X, Y, Z).

Let us know what you find out.