90° Steel Air-Bending Force Calculator

Formula and method

P[metric tf] = b·t²·Rm / [(W−Rd−Rp)·9800]. All lengths are in mm and Rm in MPa; W−Rd−Rp must be positive. The SSAB empirical constant 9800 is retained; kN=P·9.80665.

Worked example

Demonstration: b=1000 mm, t=10 mm, Rm=400 MPa, W=100 mm, Rd=10 mm and Rp=10 mm give 51.020 metric tf, about 500.339 kN. Strength and both radii are blank by default; enter actual values.

Assumptions and limits

Rm is tensile strength, not yield strength. Obtain it from the actual plate data; no strength is generated from a material name and a blank cannot be calculated.
Enter actual positive Rd and Rp values; do not use zero for an unknown radius. W exceeding their sum is only a formula requirement and does not validate tooling for the thickness or desired inside radius.
This empirical equation comes from a steel plate/Hardox bending guide and is used only for a preliminary estimate under the stated 90° air-bending conditions. Lubrication, material variation, tooling shape and friction affect results; SSAB recommends trials.
The result is not a safe machine capacity and does not check load per unit length, off-centre loading, punch/die capacity, minimum flange or frame limits. Confirm these separately from machine and tooling documentation before operation.
Here tf explicitly means metric tonne-force: 1 tf = 9.80665 kN. It is not US short ton-force or UK long ton-force. Examples are not material or tooling recommendations.

Frequently asked questions

Can I use aluminium, other angles or bottoming?

These cases are not validated here and no generic correction factor is supplied. Use a manufacturer model and trial data for the actual material, process and tooling.

References

90° Steel Air-Bending Force Calculator practical guide and common questions

What does 90° Steel Air-Bending Force Calculator calculate?

Uses the single empirical model on page 8 of SSAB’s 2024 Bending Hardox® guide. It was verified in 90° bend tests, assuming peak load at a 120° bend opening with normal friction and no lubrication. Other angles, bottoming and coining are outside scope. P[metric tf] = b·t²·Rm / [(W−Rd−Rp)·9800]. All lengths are in mm and Rm in MPa; W−Rd−Rp must be positive. The SSAB empirical constant 9800 is retained; kN=P·9.80665.

When is this useful?

Demonstration: b=1000 mm, t=10 mm, Rm=400 MPa, W=100 mm, Rd=10 mm and Rp=10 mm give 51.020 metric tf, about 500.339 kN. Strength and both radii are blank by default; enter actual values.

How do I enter the inputs?

Enter the inputs for 90° Steel Air-Bending Force Calculator: Bend length b, Actual plate thickness t, Actual tensile strength Rm (blank if unknown), Actual die opening W, Actual die entry radius Rd (required), Actual punch radius Rp (required). Calculate, check the units and assumptions, then copy or download the results.

How should I interpret the results?

Rm is tensile strength, not yield strength. Obtain it from the actual plate data; no strength is generated from a material name and a blank cannot be calculated. Enter actual positive Rd and Rp values; do not use zero for an unknown radius. W exceeding their sum is only a formula requirement and does not validate tooling for the thickness or desired inside radius. This empirical equation comes from a steel plate/Hardox bending guide and is used only for a preliminary estimate under the stated 90° air-bending conditions. Lubrication, material variation, tooling shape and friction affect results; SSAB recommends trials. The result is not a safe machine capacity and does not check load per unit length, off-centre loading, punch/die capacity, minimum flange or frame limits. Confirm these separately from machine and tooling documentation before operation. Here tf explicitly means metric tonne-force: 1 tf = 9.80665 kN. It is not US short ton-force or UK long ton-force. Examples are not material or tooling recommendations.

Where are my inputs processed?

90° Steel Air-Bending Force Calculator runs in this browser. Inputs are not uploaded to a calculation server; copying and CSV download require your action. The existing site analytics and advertising still load.