Analysis of Buckling phenomena
OBJECTIVE:
The aim of this project is to carry out buckling analysis on a cyclone separator stand. The analysis is to be carried out on plain stand and with a metallic stiffener attached to it. Further, a design study is to be carried out to find the optimum position of the stiffener.
SOLUTION:
Buckling of beam is a phenomenon where the beam bends from a straight to curved member due to compressive loads. A cyclone separator is a device used to separate particulates from a fluid and is usually mounted on a stand. This stand is fixed at the bottom and is subjected to forces on the top face. This generates compressive stresses on the legs of the stand and it may undergo buckling and stresses are generated. When this stress exceed beyond the permissible limits, the member undergoes failure.
In this project buckling analysis is performed on a cyclone separator stand with and without a stiffener and the factor of safety of the model is analysed. A stiffener is a secondary plate or section which is attached to the webs or flanges of the beams, so as to stiffen the model and reduce buckling. A design study is carried out to find out the optimal position of the stiffener, which gives the maximum factor of safety for the stand model.
Step 1: A simple cyclone separator model was provided for carrying out the buckling analysis. Since the cyclone separator does not serve any purpose in the analysis, these parts can be suppressed. For performing the analysis with the stiffener, the same has to be included into the given model. As shown in the figure, two rectangles are sketched such that it connects all the legs of the stand. It is then extruded for 75mm and placed at an offset to the top plate.
Step 2: The material for the entire model, in both cases, is assigned as Alloy steel and the properties are as given below:
Step 3: The next step is to define the fixtures and loads. As explained before, the stand is fixed at the bottom and this can be modelled by giving fixed condition to the ends of each leg. Further, a uniform force of 150000N is applied on the top face of the stand.
Step 4: For both cases, the models were meshed using an element size of 30mm.
Step 5: Design Study
For finding the optimal position of the stiffener, we have to define the minimum, maximum and step values for the dimension to be varied. This can be done by adding the offset value as a variable in the design study. The constraint was given so as to achieve a FOS greater than 25. The final goal of the study is to maximise the FOS.
Two design studies were carried out so that the best optimal solution is found out. In the first study, the approximate range where the highest FOS is achieved is found out. The minimum, maximum and step values were set as 500mm, 1500mm and 200mm respectively. It was observed that the FOS peaked in the range 900mm to 1100 mm, hence a second study was carried out with minimum value 900mm, maximum value 1100mm and step value of 20mm.
RESULTS:
Case 1: Without stiffener
Case 2: With stiffener
It was observed that the FOS for the model without the stiffener was 9.38 and that with the stiffener was 19.67. Hence, it can be concluded that the addition of stiffener increases the FOS significantly. The design study results are as shown below:
It can be observed that the highest factor of safety, FOS = 27.73, was achieved when the stiffener was placed at an offset of 1000mm from the top plate. When compared to the one without the stiffener, the FOS increased by approximately 3 times.