Solidworks Simulation Bolted assembly stress analysis
05/2/2016
Don Blanchet
3B Associates
Problem How does one use FEA to simulate bolted
assemblies ?
The easy way is to assume the surfaces are joined or bonded, no bolt stress information simulated.
Another method is to approximate the bolts with modeled extruded pins and join the outer diameter of the pin with the surface of a mating hole.
The best way is to use the bolted connection joint available in Solidworks Simulation. The variables of bolt torque, thread pitch and bolt strength are available.
The spring behavior of the bolt and joined materials is calculated.
Common Rookie mistake calculating bolt stress using S=(P/A) will under estimate stress
Not considering the pre load created when the bolt is tightened. Torquing uses up a considerable portion of the bolt load capacity.
Analysis Cases
Joined brackets no bolts
Bolts added
– 3 Torque cases
Field weld repair after bolt failure
Simple model
3/8 , 24 TPI GRADE 5 Bolt with
nut Alloy steel 2 places
300 lb
fixed
Metric
Max stress
Metric
Max deformation
Metric
Joint gap
Typical Bolt Results
Field weld repair (bolt failure)
Fillet weld
Results Summary
analysis Case
Joint Gap inch
Bolt F.O.S.
Max bracket stress
psi
Max bracket
deflection inches
No bolts
0.0000
na
55,000
.044
Bolt torque 5 ft-lb
0.0008
7.20
55,000
.053
Bolt torque 10 ft-lb
0.0006
4.30
55,000
.053
specified Bolt
torque 25 ft-lb
0.0004
1.88
49,800
.052
Field weld repair
0.0000
na
50,000
.055
Conclusions
For static loading all of the cases studied are acceptable designs.
No plastic deformation is predicted.
For shock and vibration loading the recommended torque of 25 ft-lb should be used.
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