Which term refers to a tube feature that prevents wrinkles during bending?

• A. Merge
• B. Mandrel Bend
• C. Double-slip
• D. Formed

Answer: (B)

Wrinkles during bending happen when the inner wall of the tube isn’t supported and buckles as the material is pushed to create the bend. A mandrel bend solves this by inserting an internal mandrel inside the tube to support the interior during the bend. That interior support keeps the wall from wrinkling and helps maintain a consistent cross-section, which also lets you bend to tighter radii with a smooth, even inside surface. The mandrel can be a solid rod, segmented for flexibility, or a floating type that travels with the bend, all aimed at preserving shape and wall thickness through the bend.

Other terms describe different ideas. Merging usually refers to joining tubes together rather than shaping a single tube with interior support. Double-slip and formed describe other bending or forming techniques that don’t specifically invoke interior support to prevent wrinkling, so they don’t inherently address wrinkle prevention the way a mandrel bend does.