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Prevent Destruction with SOLIDWORKS Simulation
  • Prevent Destruction with SOLIDWORKS Simulation

    Posted on Oct Thu, 2015 by seacad_admin

    Why is BUCKLING Analysis important?

    When it comes to failure analysis we are all quite aware about stresses and strains. In fact it is always the first thing we check. However, why is it that we neglect the other modes of failures, such as fatigue, buckling, and natural frequency?

    In reality, these modes of failures are highly as likely to occur as much as material failure due to high stresses. In this article we will focus on Buckling, a failure mode so dangerous that we need to put more emphasis on it.

    Buckling can be defined as the sudden, large, lateral deflection of a column owing to a small increase in an existing compression load. Examples of situations in which buckling could occur would be:

    • Structural frames meant to hold weight such as cabinets, buildings and supports
    • Machinery housing
    • Support legs of furniture

    And many more. The difference between buckling and stress failure is that buckling does not lead to material failure. The material is still intact, but it causes the material to loose stiffness. Imagine a three legged stool. With a high enough force acting downwards, a leg would lose its stiffness, making it weak like jelly. When this happens, the leg will bend, making the stool loose its stability and causing it to fall. Now in some cases, that could be worse than material failure. Imagine if a 20-storey building were to fall down due to buckling, the debris may not just fall straight down but along a lateral length, which leads to 60 meters of destruction!

    A 13-Storey building project worth millions of dollars toppled over due to poor design

    Here is the scary part of buckling:

    The Euler Formula basically describes the load (Pcr) that would cause a beam of particular length (L), material characteristic (E) and cross sectional area charactieristic (I) to buckle, and its defined as:

    Pcr = (π^2 EI) / L^2 

    For a beam pinned on both sides.

    So how can we know if buckling is more likely to occur than material failure. One way is to use the Buckling Analysis failure found in SOLIDWORKS Simulation. Lets take a look:

    Here I have a cabinet which consists of beams and the housing. A load is applied on top with the cabinet fixed at the bottom. When I run a linear static analysis, I see that I get a Factor of Safety (FOS) plot of :

    The minimum of 2.4 seems to be a singularity issue, therefor it is ignored. However overall the FOS is about 4.6, meaning this design is able to take up to 4.6 times the load applied. Now when we perform the buckling analysis with the same parameters, we get this:

    pic3

    Here we get that buckling FOS is 3.686, meaning that buckling occurs only at 3.686 times the applied force. This shows that buckling is more likely to occur than due to material failure!

    So how can we make sure that we increase the buckling FOS? Well with this we could try to:

    • Use materials of higher Young’s Modulus
    • Use beams of different cross sectional areas

    And just like that, we managed to create a safer structure for all.

    If you would like to know more about buckling and factor of safety analyse, you may call us at +65 6372 1416 or email support@seacadtech.com.

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