Basic geometric details of the bracket only. This detail is from Solidworks which puts annoying little boxes around each part. This is not normal draughting practice.
The finite element stress analysis |
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Although this is a simple and very common component, hand analyses frequently concentrate on stress on the sides. This analysis demonstrates that this is not where the maximum stresses are developed, although the maximum stress is very localised.
It also shows the shape and relative size of the heel point where the bracket bears compressively on the back plate. Exactly what to use for a heel area is always difficult to guess in a hand analysis. This shape of component is ideal for solid modelling and tet meshing but it is easy to end up with an enormous number of elements. |
Basic geometric details of the bracket only. This detail is from Solidworks which puts annoying little boxes around each part. This is not normal draughting practice.
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Model picture.
The bracket is aluminium and the back plate and peg bolts are steel. |
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Model constraints and loading. The plate back face is also fully fixed.
There are contact conditions between the bracket back face and the plate front face, and between both pegs on the plate and the bracket. Contact is very easy to setup in DesignSpace. |
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Deflections
Deformation from the side direction showing the bracket parting under tension from the back plate except where this is prevented by the bolts; and the compressive heel at the base of the bracket.
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Deformation from the front showing the sides of the bracket pulling in. This will be started by the base deformation causing rotation of the sides.
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Heel indentation in back plate.
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Elongation of hole and separation of bracket from the lower fixing bolt. Tensile stress is shown on each side of the hole.
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Deformation of the fixing bolts grossly exaggerated to show indentation of the shanks.
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von Mises stress
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von Mises stress. The maximum is in a very small area and is probably partly due to element meshing, although this model had a fairly fine mesh around the holes.
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Localised von Mises stress on load support hole, at the intersection of several elements. Mesh refinement may help this.
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Minimum principal stress
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Minimum principal stress. Maximum compressive stress is under top bolt seating. The bolts in this model had no tension applied so the plate is not under preload.
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Maximum principal stress
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Maximum principal stress. Localised stress concentration around the load supporting hole. A radius on this corner might spread out the concentration and result in a reduced stress? Or would it reduce the overall section stiffness and result in greater deflection? It would be interesting to test this. Also some mesh changes would be useful. |
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Maximum principal stress showing very slight concentrations at the bottom bolt seating and on the fillet between the bracket base and back.
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Maximum principal stress on the under side of the bracket base showing the maximum value at the loaded bolt hole.
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Updated 25/01/2003