Which is not a side effect of bending a tube?

• A. Inner radius becomes thinner
• B. Outer diameter increases
• C. Wall thickness decreases
• D. Bend radius tightens

Answer: (A)

When a tube is bent, the outside of the bend is stretched while the inside is compressed. This causes real changes in dimensions: the outer part tends to increase in diameter and the wall there can thin as material is pulled apart. The bend radius is determined by the tooling and how the material yields, so it can appear tighter if the bend is sharp or if springback occurs. The inner radius itself is a curvature measure, not a thickness, so bending doesn’t make this distance “thinner.” That’s why inner radius becoming thinner isn’t a typical side effect of bending.