Anderlen stress analysis 2

The comparison of stresses around a hole
with and without a fitted bolt.

Introduction.

T

his is an analysis of the loading in a plate with a single central hole with a fitted bolt, under axial tensile loading. The bolt is not loaded other than by the compression due to plate contact. The analysis is intended to show the difference in the plate stress and deflection with the hole full or empty.
The perfectly fitted bolt is unrealistic but represents a starting point for this type of analysis.

Finite Element Model.

A finite element model of a quarter of the plate is used, with symmetrical constraints applied at the cut surfaces. DesignSpace has been used for the analysis, since this will model contact between solid bodies very easily. Solidworks was used to model the solid assembly. To run the model with the hole empty, the bolt part was suppressed; all other model conditions remaining the same.

The mesh
viewed without
perspective.
An enhancement
request has
been logged with
Ansys US for
perspective
viewing in
DesignSpace.

Loading and Constraints.

The plate has a tensile load of 200 MPa applied to the right hand edge. The solution sequence is linear static, and the material properties are linear. The hole edges are free to deflect. Both plate and bolt are in the same material in this analysis.

The loading
and constraints.

Results.

Since this analysis is done as a comparison, the results for each parameter are presented together for the open and filled hole cases. All displacements are shown grossly exaggerated.

Displacements.

Open hole
displacement.

Filled hole
displacement.

Normal x stress.

Open hole
normal stress
in the axial
loaded
direction.

Filled hole
normal
stress.

Minimum principal stress.

Open hole
minimum
stress.

Filled hole
minimum
stress.

Maximum principal stress.

Open hole
max prin
stress.

Filled hole
max prin
stress.

von Mises stress.

Open hole
von Mises
stress.

Filled hole
von Mises
stress.

Tabulated Results.

Analysis of open and filled holes in tension.
	displacement mm	normal stress MPa	min prin stress MPa	max prin stress MPa	von Mises stress MPa
open hole stress position	0.126 bar end	756 90 deg	-297 0 deg	756 90 deg	750 90 deg
filled hole stress position	0.122 bar end	601 90 deg	-281 90 deg	619 90 deg	759 90 deg
difference %	-3.28	-25.76	-5.80	-22.17	1.14

Note:
0 degrees implies that result is on the hole edge, in line with the loaded direction.
90 degrees implies that result is on the hole edge, transverse to the loaded direction.

Conclusions.

The bar deflection in line with the applied load has reduced slightly.
The normal stress in line with the applied load has reduced significantly and is roughly the same as the maximum principal stress.
The minimum principal stress has reduced slightly but has moved from being a hole edge bending stress in line with the applied load, to a contact stress transverse to the applied load at the point of contact with the bolt.
The maximum von Mises stress has actually increased slightly and is in the same position, but has changed from tensile bending at the hole edge, to tensile in the loaded direction plus compression due to the contact.
Overall, the main purpose of using a fitted bolt is demonstrated by a large reduction in normal tensile stress.
Note that not all the necessary data have been presented here; it is intended to produce more analyses which will clarify this. Also this analysis represents a rather large bolt.

Using DesignSpace.

Some comments about using DesignSpace.
This is a very easy program to set up and runs quickly. There were problems initially with program stability but with Ansys Tech Support help, this was traced to the graphics card on the machine used for these runs. The existing 64 Mb ATI graphics card was changed to a 128 Mb PNY with the new nVidia chip, and there have been no more blue screens from Windows 2000 since then. There is now a problem with the display of some Microsoft Word files which did not happen before but ..... well you can't have everything it seems!
The way that contact problems can be done in DesignSpace is impressive. One downside which is often common with interactive type programs is that it is easy to lose the settings of a previous run, so it's necessary to keep saving to a different file name.
Annoyingly, there is no way at present to display in perspective in Designspace; however this facility has been requested.

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Anderlen stress analysis 2 The comparison of stresses around a hole with and without a fitted bolt.

The comparison of stresses around a hole with and without a fitted bolt.

Anderlen stress analysis 2

The comparison of stresses around a hole
with and without a fitted bolt.

The comparison of stresses around a hole
with and without a fitted bolt.