ANALYSIS OF BUCKLING PHENOMENA

ANALYSIS OF BUCKLING PHENOMENA

AIM – To perform buckling analysis on a cyclonic separator stand to find change in its buckling factor of safety. Run a design study and find the optimum position for the stiffener.

OBJECTIVES-

1. Create a metallic stiffener on the legs of the stand.
2. Run Buckling analysis to find out the change in buckling factor of safety.
3. Run a design study and find the optimum position for the stiffener to maximize buckling factor of safety.
4. Compare the results for all the cases using tables and highlight the best one

INTRODUCTION-

Cyclonic separation is a method of removing particulates from an air, gas or liquid stream, without the use of filters, through vortex separation. When removing particulate matter from liquid, a hydrocyclone is used; while from gas, a gas cyclone is used. Rotational effects and gravity are used to separate mixtures of solids and fluids. The method can also be used to separate fine droplets of liquid from a gaseous stream.

A high speed rotating (air) flow is established within a cylindrical or conical container called a cyclone. Air flows in a helical pattern, beginning at the top (wide end) of the cyclone and ending at the bottom (narrow) end before exiting the cyclone in a straight stream through the centre of the cyclone and out the top. Larger (denser) particles in the rotating stream have too much inertia to follow the tight curve of the stream, and thus strike the outside wall, then fall to the bottom of the cyclone where they can be removed. In a conical system, as the rotating flow moves towards the narrow end of the cyclone, the rotational radius of the stream is reduced, thus separating smaller and smaller particles. The cyclone geometry, together with volumetric flow rate, defines the cut point of the cyclone. This is the size of particle that will be removed from the stream with 50% efficiency. Particles larger than the cut point will be removed with a greater efficiency and smaller particles with a lower efficiency as they separate with more difficulty or can be subject to re-entrainment when the air vortex reverses direction to move in direction of the outlet.

PROCEDURE-

1. Import the cyclone separator assembly. Proceed with Feature recognisation.
2. Hide all other parts other than stand. Save the part as stand.
3. Now, open the part. Select Top plane. Draw outer boundary of stiffener. Make sure that it has same corners as that of stand.
4. Extrude the stiffener to height 50mm and offset it distance 250mm.

5. Click on Simulation>New study>Buckling Analysis.
6. Apply material Alloy Steel to stand and stiffener.
7. Select Fixed geometry and select end faces of each leg.
8. Apply the load of 15000 N on top face.
9. Click on Mesh>Create mesh. Set mesh parameter slider to fine.
10. Click on Run to obtain Results.
11. Right click on Results>List of Factor of safety.
12. Click on New study>Design Study.
13. In Variables select model dimension of distance between stiffener and top plane.
14. Range by step is selected by default. Select minimum value to 250 mm and maximum to 1750 mm.
15. In step put 125 mm.
16. For constraints select Add sensor>Buckling Factor of Safety. Set minimum value to 20.00.
17. For goals select Add sensor>Buckling Factor of Safety. Set maximize.
18. Click on run.

RESULTS –

For stand without stiffener-

Buckling factor of safety= 11.704

For stand with stiffener-

For optimum scenario-

So, maximum Buckling factor of safety =21.041 is observed when stiffener is at distance 950mm from top plane.

CONCLUSIONS & EXPLANATIONS-

1. Make sure that stiffener outer boundary coinciding with that of legs of stand. Else there will be contact issues during simulation.
2. Run a buckling study before running design study.
3. Select’ Buckling factor of safety’ while adding constraint or goals and not mistake it with ‘factor of safety option’.
4. Clearly, the maximum FOS will be there somewhere around 1m distance i.e. somewhere near middle of legs.