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.