Buckling Analysis on a Cyclonic Separator Stand
INTRODUCTION
When any long slender object is loaded in the axial direction, it will buckle when the load reaches a particular load. This load called the critical load, Pcr, is when the object will deflect significantly in the lateral direction (perpendicular to the load). Thus, buckling is 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 slender structure is subjected to axial compressive stress, buckling may occur as lateral displacement.
The buckling FOS is the ratio of critical buckling load to the currently applied load.
Buckling factor of safety = (P critical)/ P applied)
Project Objective:
The objectives of the project are:
- To use SolidWorks Simulation tool to observe the buckling characteristics of a Cyclonic Separator Stand having long slender legs and find out the first critical buckling load or the buckling factor of safety.
- To add a stiffener to the legs of the stand and determine the increase in critical buckling load.
- To use SolidWorks parametric design study to run parametric simulations and obtain the optimum position of the stiffener that will maximize buckling FOS.
Problem Definition:
The Cyclonic Separator Stand is subjected to a load of 150kN in the top face and the bottom face of the legs are fixed in all three directions (X, Y and Z) as shown in figure 1. Only the first Buckling mode is studied here.
Stiffener, having a height of 75mm is modelled in an arbitrary and the location of the stiffener is to be found out using the buckling analysis and subsequent design optimisation study. This should result in a design that having maximum buckling FOS.
Case 1: Buckling analysis of Cyclone Separator stand without stiffener
Geometry with boundary conditions
Figure 1: Cyclone Separator Stand
Applied Load: 15kN
Mesh Size: 18
RESULT
The first buckling mode observed was as shown in figure 2.
Figure 2: Mode shape 1, Buckling Factor of Safety = 9.35
Inference
The observed critical load was 9.35 that of the applied load and the structure was reliably safe under the loading conditions.
Case 2: The Cyclone Separator Stand Equipped with a stiffener
Height of the stiffener = 75 mm
Geometry with boundary conditions
Figure 1: Cyclone Separator stand with stiffener
Applied Load: 15kN
Mesh Size: 18
RESULT
The first buckling mode observed is as in figure 2
Figure 2: Mode shape 1, Buckling Factor of Safety = 27.56
Inference
The observed critical load was 27.555 that of the applied load and the structure was much more reliably safe under the loading conditions as well as the critical load (Buckling FOS) increased 3 times than the design without the stiffener.
Case 3: Parametric design study to locate the optimal position of the stiffener.
Defined Parameters:
- Variables
Offset Distance: The stiffener was moved axially from .25m to 1.75m through an increment of .25m from the datum (Ground level).
- Constraints
Buckling factor of Safety: The minimum buckling FOS criteria was set as 25.
- Goal
Maximize the Buckling factor of safety parameter.
The above inputs were given to the solver. And the solver populated 7 scenarios to analyse and choose the best scenario among them revealing the position of the stiffener with respect to datum. The output of the design study is as listed in table 1.
Table 1: The Parametric Design Study Output
Figure 1: Buckling factor of safety Vs. Offset distance of the stiffener
Inference
The parametric design study gave an optimal location of the stiffener as a 1m offset (set 4) from the datum, which was already the position for the buckling analysis. Placing stiffener at this location will yield maximum Buckling factor of safety thereby maximum critical load of buckling.
Conclusion
From the analysis conducted in three stages, the stand without the stiffener showed a buckling factor of safety of 9.35. Whereas the one with stiffener exhibited almost 3 times the FOS i.e. 27.56. The stiffener location was found to be optimal by using a parametric design study and the design met the requirements of Buckling FOS ≥ 25.
Submitted by,
Amal Swalih S R