Welds in Pro/E and ANSYS Workbench

Mike Renfro

July 14, 2008

1 Modeling Weld Material as Pro/E Parts

Accurate analysis of welds in ANSYS Workbench requires that the weld geom-etry be accurately modeled. Since all of our geometry modeling is done insidePro/E, we’ll use it to model the welds as well. The basic procedure will be tocreate simple parts that match the weld geometry. By default, we’ll assumethat a weld is a revolved or extruded isosceles right triangle with a given leglength. For a weld along a straight edge, this triangle will be extruded. For aweld along a circular edge, this triangle will be revolved. If we’ll have a largenumber of different weld geometries (with respect to either weld size, length,or circular edge diameter), we might use a family table to make all the similarwelds.

Figure 1: Sketch of Revolved Feature for Weld Part

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2 Assembling Welds to Other Pro/E Parts

Once we have the various weld geometries modeled, we assemble them as sep-arate components into the top-level assembly or any lower-level subassemblies.

Figure 2: Welds Assembled to Other Parts

3 Suppressing Contact Pairs for Missing LoadPaths

When we import a Pro/E assembly into ANSYS Workbench, every pair of partsthat make contact with each other generates a contact pair. In order to accu-rately reflect the actual load paths on the real assembly, we may need to suppresssome contact pairs in order to drive the loads through the new contact pairsassociated with the welds. In Figure 3, notice the “X” symbols by some of thecontact pairs indicating that they’ve been suppressed.

4 Examining Differences Among Models WithVarying Levels of Weld Accuracy

It may be helpful to see the differences in model displacement and maximumequivalent stresses as we move from a simple model with no welds to a morecomplex model with welds present or absent on the outside surface of the bracket

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Figure 3: Screenshot Showing Suppressed Contact Pairs for Missing Load Paths

(with a surface normal in the positive Z direction), the inside surface of thebracket (with a surface normal in the negative Z direction), or between the rodand the base block. The base block measures 6 in × 6 in × 2 in, and is fixed onfive surfaces. The bracket has a 100 lbf load applied in the negative Y directionon the bottom surface of the smaller hole. See Figure 4 for clarification.

As shown in Figure 5, ANSYS Workbench’s default mesh size was used onall parts except for the welds. The weld mesh size was held to approximately0.125 in.

As an example, Figure 6 shows the equivalent stresses across the assemblywhen all three welds are present, and loads travel through six contact pairs.Table 1 shows the maximum equivalent stress and maximum displacement foreach model.

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Figure 4: FEA Model Loads and Boundary Conditions

Figure 5: Mesh Sizing Overview

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Tab

le1:

Sum

mar

yof

Res

ults

Var

iant

dm

ax(i

n)σ

max

(psi

)σ

max

Loc

atio

nN

ow

elds

,2

cont

act

pair

s0.

0135

4218

Bot

tom

Bra

cket

Face

Out

side

wel

d,3

cont

act

pair

s0.

0145

1030

0O

utsi

deW

eld

Out

side

and

back

wel

ds,

4co

ntac

tpa

irs

0.01

4710

300

Out

side

Wel

dA

llw

elds

,6

cont

act

pair

s0.

0137

7511

Bac

kW

eld

5

Figure 6: Stress Results Including All Welds

6