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.

- Skill level:
- Easy

### Other People Are Reading

### Things you need

- Calculator (optional)

Show More

## Instructions

- 1
Measure the length (L), width (W), outer diameter (OD) and inner diameter (ID) of the tube .

- 2
Calculate the modus of elasticity (E) by using the following formula: E = stress ÷ strain = psi ÷ in/in = psi.

- 3
Calculate the second moment of inertia (I) by using the formula: (pi x (OD^4 - ID^4)) ÷ 64.

- 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.