Calculation
SF = Rp / σv
SF compares the material yield strength directly against the actual equivalent stress; unlike the DIN 743 shaft calculator, this calculator assumes no round shaft and no notch effect.
SF = Rp/σv
Static safety factor against yielding
SF compares the material yield strength directly against the actual equivalent stress; unlike the DIN 743 shaft calculator, this calculator assumes no round shaft and no notch effect.
MINTSI
02
Result
Select a target and calculate.
Understand the inputs
- Safety factor SF — Ratio of yield strength to equivalent stress.
- Yield strength Rp — Material property Rp0.2 (or ReH) at operating temperature.
- Equivalent stress σv — Actual equivalent stress, e.g. from the combined GEH stress calculator.
Example
355 MPa yield strength against 142 MPa equivalent stress gives SF = 2.5.
Assumptions and limits
Applies to predominantly static load; endurance strength, notch effects and cyclic load require a separate dynamic strength check, e.g. DIN 743 for shafts.
Understand Static safety factor against yielding
This calculator determines the static safety factor against yielding of an arbitrarily shaped part from yield strength and equivalent stress — independent of shaft cross-section, notch geometry or cyclic load.
What does this quantity describe?
The static safety factor SF = Rp/σv compares the material's yield strength Rp directly against the actual equivalent stress σv (e.g. from the GEH calculator). SF > 1 means the yield strength has not yet been reached; SF ≤ 1 means yielding has begun or occurred.
Think of the ratio of a bridge's load capacity limit to the load actually crossing it: as long as the limit is well above the load, margin remains; as the two converge, the safety factor drops toward 1.
Formula and variables
SF = Rp / σv
SF = Rp / σvσv = Rp / SFRp = SF · σv
| Symbol / input | Meaning |
|---|---|
| Safety factor SF | Ratio of yield strength to equivalent stress. |
| Yield strength Rp | Material property Rp0.2 (or ReH) at operating temperature. |
| Equivalent stress σv | Actual equivalent stress, e.g. from the combined GEH stress calculator. |
Choose the inputs correctly
Rp (allow) is the material's yield strength Rp0.2 or ReH at operating temperature. σv (actual) is the actual equivalent stress, typically from the combined GEH stress calculator.
How to use the calculator
First compute σv with the appropriate equivalent-stress calculator. Enter that value together with the yield strength here to get SF.
Worked example
Rp = 355 MPa and σv = 142 MPa give SF = 355/142 = 2.5.
Understand the result and units
SF = 2.5 means the equivalent stress would need to rise 2.5-fold before the yield strength is reached. Unlike the DIN 743 shaft calculator, this assumes no round-shaft geometry and no notch effect — it suits arbitrarily shaped parts.
Rp and σv are usually given in MPa; SF is dimensionless.
Difference from the DIN 743 shaft calculator
The DIN 743 shaft calculator is designed specifically for round shafts with defined notch locations (shoulders, grooves, keyways) under cyclic load, and accounts for the notch effect factor, size influence and surface factor as part of a fatigue-strength verification. This calculator, by contrast, checks only the static yield limit of an arbitrarily shaped part against an already-known equivalent stress, assuming no shaft geometry, notch effect or load cycling — making it more broadly applicable but also less specific than DIN 743.
Typical applications
The calculator is used as a final static check for arbitrarily shaped, ductile parts under predominantly static load, such as brackets, mounts, castings or sheet-metal structures.
Assumptions, limits and common mistakes
The calculator addresses only static safety against yielding. Cyclic or fluctuating load, notch effects and size influence require a separate dynamic strength check, e.g. DIN 743 specifically for round shafts with shoulders and grooves.
Common mistake: A common mistake is confusing this general static check with a full fatigue-strength verification — SF > 1 here only means no yielding occurs under the current load, but says nothing about endurance under cyclic load.
Frequently asked questions
What does SF ≤ 1 mean?
The equivalent stress reaches or exceeds the yield strength; the part would yield plastically at that location.
Can I use this instead of DIN 743 for shafts?
Only for a rough static estimate; for shafts with notch locations under cyclic load, DIN 743 with its notch effect factor and size influence is the right tool.
Which yield strength do I use?
Rp0.2 (0.2% proof stress) for most steels, ReH for materials with a pronounced yield point, both at the relevant operating temperature.
How does this relate to the GEH calculator?
The GEH calculator produces σv from superimposed stress components; that result is used here directly as the actual value.
What SF value counts as sufficient?
It depends on the application, load uncertainty and consequences of failure; typical values range from 1.2 to 3, but there is no fixed rule.