Fig. 1 shows four extruded aluminium sections. Identify which section resists bending best about the axis shown and give a reason. [4]
Question 1 Report
Fig. 1 shows four extruded aluminium sections. Identify which section resists bending best about the axis shown and give a reason. [4]
Answer Details
The I-shaped extruded section [2] resists bending best about the axis shown.
When a section bends, material furthest from the neutral axis contributes most to its second moment of area, and therefore to bending stiffness. In an I-section, a large proportion of the material is in the two flanges, far from the neutral axis, rather than concentrated in the middle. [2]
The flanges carry much of the tension and compression produced by bending. This is why an I-section can be very stiff without being solid and heavy.
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