FEA of Buckling Phenomena

AIM:

To do a finite element analysis (FEA) of buckling in a Cyclonic Separator Stand with and without a stiffener constructed across the columns and also do a Parametric Design Study for finding the optimum position of the stiffener using SOLIDWORKS

THEORY:

Cyclone separator or simply cyclones are separation devices, dry scrubbers that use the principle of inertia to remove particulate matter from flue gases. It works like a centrifuge, but with a continuous feed of dirty air. Cyclones separators are one of many air pollution control devices known as pre-cleaners since they generally remove larger pieces of particulate matter. This prevents finer filtration methods from having to deal with large, more abrasive particles later on.

Buckling is an instability that leads to structural failure. The failure modes can in simple cases be found by simple mathematical solutions. For complex structures the failure modes are found by numerical tools. When a structure is subjected to compressive axial load, buckling may occur. Buckling is characterized by a sudden sideways deflection of a structural member. This may occur even though the stresses that develop in the structure are well below those needed to cause failure of the material of which the structure is composed. As an applied axial load is increased on a member, such as a column, it will ultimately become large enough to cause the member to become unstable and it is said to have buckled. Further loading will cause significant and somewhat unpredictable deformations, possibly leading to complete loss of the member’s load carrying capacity. If the deformations that occur after buckling do not cause the complete collapse of that member, the member will continue to support the load that caused it to buckle.

Finite element analysis is the process of simulating the behavior of a part or assembly under given conditions so that it can be assessed using the finite element method. FEA is used by engineers to help simulate physical phenomena and thereby reduce the need for physical prototypes, while allowing for the optimization of components as part of the design process of a project.

PROCEDURE:

• Import the file in solidworks and as we have to do analysis on the stand only, suppress all the other parts and then save the stand as a separate part.

• First start the analysis without the stiffener. To start with the analyses click on ‘Simulation’ and select ‘Buckling’ for buckling study.

• Select the material for the stand as Alloy steel.

• Now for fixing the geometry right click on ‘Fixtures’ and then on ‘Fixed Geometry’ then select all the bottom faces of the legs as this will fix the stand.

• Now for applying the load right click on ‘External Loads’ then on ‘Force’ now select the top face of the stand and enter the value of force as 150000 N make sure its direction is downwards.

• Now right click on ‘Mesh’ and then click on ‘Mesh and Run’ to rum the simulation.

• Secondly for the analysis with the stiffener. A sketch is created on the top plane of the stand, set the stand such that the bottom face can be seen now make a rectangle in such a way that its sides coincide with the inner sides of the legs. Now make another rectangle which coincides with other edges. Now extrude the sketch as 75 mm at an offset of 1000 mm.

• Now fix the geometry.

• Now apply the load of 150000 N.

• Now create a mesh.

• Thirdly for the Parametric Design Study. Select new Design study. Now add ‘Variables’ as ‘Offset Distance’ by clicking on the offset distance of the stiffener and setting the minimum value as 250 mm and maximum value as 1750 mm also add the step as 250 mm. Now add ‘Constraints’ select ‘Simulation Data’ as the ‘Data Quantity’ now select the ‘Properties’ as ‘Buckling Factor of Safety’ and select ‘is greater than’ and the minimum value of buckling as 25. Also add ‘Goals’ as the maximum value of buckling factor of safety.

RESULTS:

• STAND WITHOUT STIFENER

Animation : Buckling - Without Stiffeners

• STAND WITH STIFFENER

Animation : Buckling - With Stiffeners

• PARAMETRIC DESIGN STUDY OF STAND WITH STIFFENER

CONCLUSIONS:

• We can see that in the first case of stand without any stiffener the Buckling Factor of Safety is 9.3643. This means the stand can withstand a load which is nearly 9 times more than the load applied.
• In the case of stand with a stiffener the Buckling Factor of Safety is 27.935. This means the stand cab withstand a load which is nearly 27 times more than the applied load. By adding the stiffener the load carrying capacity of the stand is increased by almost 3 times.
• We can see that with the Parametric Design Study the position of the stiffener is best at a distance of 1000 mm from the top plane as the Buckling Factor of Safety is maximum at this point that is 27.9345.