Sheet Metal Example

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Creating sheet metal parts for your beam in SolidWorksWhat follows is an example of how to build and analyse a simple sheet metal beam in SolidWorks.

Your structure will be longer and more complex, but this example should give you a good idea of

how to go about using SolidWorks to help you in your design. Remember, only use SolidWorks if you

are going to use it dont just draw pictures for the sake of it! There are excellent tutorials in

SolidWorks on sheet metal, finite element analysis, spot welds, etc. and you may want to consult

these too. You cannot use the COSMOS optimizer for shell meshes, which are used below. If you

want to use the optimizer, which is not available in your home version of SolidWorks, you will need

to use a solid mesh. An example optimization is included at the end of this document.

A basic folded sheet part

Select Base flange and sketch sheet metal shape:

Exit sketch and define thickness:


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Select Edge flange. Note Trim side bends is selected and radius is set to 3mm (naturally, this will

depend on how you intend to bend the sheet):

Add two more flanges:


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Note how the final flange overlaps the first two, and is offset by 0.1mm so that SolidWorks does not

unite the overlap with the other flange:

Select Flat pattern Unsuppress and Suppress to toggle between a template for the sheet

metal and the formed part:


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Analysing an assembly

Create a new assembly and add this part and the mounting plate. Use the Mate tool to position

the parts. Here I am positioning the two joining face such that they are parallel and very close

together, but not touching (0.1mm).

Further Mates position the part relative to the mounting plate:


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We need to spot weld the part together and to the mounting plate. The welds will be positioned

using reference points (add as many as you think you will need):


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Setting up the COSMOSWorks analysis

Things get a bit more tricky now! We need to define what type of analysis we want and what

conditions the beam is under. To begin with, open up a new Study in COSMOSWorks and choose

Shell Mesh Using Surfaces and Static:

Right click on Shells and Define By Selected Surfaces.... Select all the surfaces on one side of both

parts:


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Right click on Shells and Apply Material to All.... Use 1023 Carbon Steel Sheet:

Add the spot welds by right clicking on Load/Restraint and selecting Connectors.... Select faces

which correspond to those you selected as shell surfaces above. Use the reference points as created

above to position the welds:


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Right click on Load/Restraint and add a restraint to all the mounting point holes (select edges on the

shell surface):

Then add a loading force:

I have added a force to a 15mm hole. The actually load would be applied in a small area at the base

of this hole, but for simplicity I am applying it to the whole interior surface. Only 10N is used,

because this is a very weak structure (you need to use 200N):


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Now we need to tell the analysis what to do where the two parts meet. Right click on

Contact/Gaps and select No Penetraction:

Now right click on Mesh and select Create Mesh. A coarse mesh will give quicker, but less

accurate results while the opposite is true of a fine mesh. Here Im using the default:


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Now right click on the Study and Run. Here are the stress results:

and the displacement:

Clearly using one spot weld to join to the back plate is insufficient: there is large displacement here.


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I have used four welds positioned as shown:

to produce the following stresses and displacements:


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There is now much less displacement near the welds. Notice, though, how the mounting plate is

under considerable stress obviously an area to add more sheet metal.

Because we are dealing with sheet metal, it is likely that buckling will be a problem. It is therefore

advisable to run a buckling analysis too. Open a new study and select buckling. The properties of the

previous study can be copied by right clicking on each property of the study and selecting copy and

then paste when the corresponding property of the new study is highlighted. Here are the results

of a buckling study:

The load factor of -0.027 means that buckling is not predicted. Look up buckling load factor in the

COSMOSWorks help to interpret load factors.


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Optimisation

(N.B. this example uses a solid mesh and slightly different geometry than above, but the process is

basically the same)

It is possible to optimise the dimensions of parts in an assembly using an optimization study. We

need to define the objective, the design variables and the constraints. Our objective is the mass of

the beam:

I have chosen just one design variable: the height of the beam. Note that I have added equations to

other dimensions so that they vary with the design variable (recall that these are derived

parameters)


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The constraints are that the deflection should not exceed 5mm,

the peak stress should not be greater than the yield stress of the material (~300,000,000 N/m2),


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and that the beam should not buckle. Here a safety factor of 2 is chosen (the upper bound is set

high so it is inactive) for the first mode of buckling:

The optimisation reduces the mass slightly by reducing the height of the beam from 50mm to 46mm,

whilst meeting the stress constraint. You may want to include a factor of safety in your stress

constraint (though the beam will be heavier). The other constraints are easily met. Note the slightly

increased stress in the beam below:


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The optimisation takes quite a long time, particularly when lots of design variables are used. You will

need to run it overnight if you want to optimise the whole beam. Try coarsening the mesh to speed

things up, or just optimise individual parts.

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Sheet Metal Example