How to Determine Deflection in Steel Tubing

Written by jason jensen
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The term "deflection" is used in engineering to describe the degree to which a load bearing structure will deform under stress. In other words, it is the amount a steel beam or tube will bend or twist when a certain amount of force is exerted on it. It is always important to determine the deflection of steel tubes whenever you are using them to support weight. Even though a certain amount of deflection is inevitable, too much can cause your structure to collapse.

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  1. 1

    Measure the length (L), width (W), outer diameter (OD) and inner diameter (ID) of the tube .

  2. 2

    Calculate the modus of elasticity (E) by using the following formula: E = stress ÷ strain = psi ÷ in/in = psi.

  3. 3

    Calculate the second moment of inertia (I) by using the formula: (pi x (OD^4 - ID^4)) ÷ 64.

  4. 4

    Use the figures gathered in Steps 1-6 to perform the following calculation: Deflection = W x L^3 ÷ 3 x E x I.

Tips and warnings

  • There are many free engineering calculators online that you can use to determine deflection.

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