KEVOS® MAKEOS · Fabrication
Minimum and Maximum Bend Radius
What is the smallest bend radius this sheet takes without cracking, and the largest that still forms permanently?
Minimum inside bend radius from the material’s reduction of area in a tensile test, and the maximum radius that still produces permanent (plastic) deformation, by the handbook formulas.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Material thickness | mm | Sheet or plate thickness. |
| Reduction of area in a tensile test | % | Percentage reduction of area from a tensile test of the material (from the mill certificate or material data). |
| Elastic modulus | GPa | Elastic modulus. |
| Yield strength | MPa | Yield strength. |
| Planned inside bend radius | mm | Inside radius you intend to use. |
Method and formulas
- R_min = T (50 ÷ r − 1), with r the reduction of area in per cent.
- R_max = T E ÷ 2 YS (beyond this the outer fibres stay elastic).
- Example: 3 mm sheet with 40% reduction of area can be bent to 0.75 mm minimum radius.
Limitations
- Bends across the rolling direction tolerate tighter radii than bends along it.
- Edge condition (burrs, shearing) causes cracks at larger radii than predicted.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Choose a punch radius that will not crack the bend
- Check whether a large-radius bend will form at all
- Compare materials for formability
Who it is for
- Fabrication supervisors
- Manufacturing engineers
- Estimators
What you get
- Minimum bend radius
- Maximum bend radius for a permanent bend
- Check of the planned radius
Interpreting the result
- Allow extra radius for bends parallel to the grain and for sheared edges.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1346–1347. Topic reference; no source tables or recommended settings are reproduced.
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