Sheet Metal Engineering

A: B is π/2 × (R + K·t) → 1.5708 × (3.0 + 0.66) ≈ 5.24 mm. A looks tempting if you forget the K-factor term and run centerline at R only. C shows up when someone drops K entirely and runs outer fiber. D is what you get if you mistakenly use degrees directly instead of radians, a classic spreadsheet slip.

A: B matches common guidance of 1× thickness for 5052 in air bending and keeps the outer fibers below cracking strain. A often works in protos but lives on borrowed time when grain direction flips. C is safe but drives part growth and packaging pain without need. D belongs to soft copper logic, not aluminum-magnesium alloys.

A: B explains the directional nature and thickness sensitivity. A would show tool marks and broader deformation issues. C would crack regardless of bend direction if edge prep were the driver. D shows delayed cracking and usually after plating, not immediately off the brake.

A: C comes from T = (1.42 × t² × L) / V → (1.42 × 16 × 600) / 32 ≈ 168 kN. A is what you get if you forget length is in mm and mentally run meters. B drops the material factor, a common habit when someone last lived in aluminum. D assumes bottoming, not air bending.