Profile derived from the model. Click a number or a row to use that section in the calculation.
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Verification diagrams
The four diagrams update with the data entered. Hover over lines and points to read the values.
How to use it
Enter the diameter of the section to check, the material and the moments acting on it. In a rotating shaft the bending moment produces an alternating stress even if the load is fixed; the transmitted torque is usually constant and goes in as mean torque. Kt and notch sensitivity describe the fillet, groove or keyway at the section.
The peak factor multiplies the loads for the static check: start-ups, braking and shocks cause overloads that don't count for fatigue, because they're rare, but can make the section yield.
Uploading the STEP model
If you have the 3D model of the shaft, export it in STEP format (AP203, AP214 or AP242) and upload it to the calculator. The file is read directly in the browser: no data leaves your computer, an important point for projects under confidentiality.
- Axis and profile: the shaft segments are rebuilt from the coaxial cylindrical surfaces, distinguishing the outer profile from holes.
- Shoulders: for each change in diameter, d, D and the fillet radius are read from the toroidal surface; Kt and Kts come from approximations of Peterson's charts, q from Neuber's formula.
- Grooves, seats and threads: recognised from the non-axisymmetric faces, with conservative notch factors from tables.
- 3D view: the model is shown with the sections highlighted; the one used in the calculation is in orange.
The moments at the section aren't derived from the model: they depend on loads, supports and the static scheme, and must be calculated separately.
Method
The Haigh diagram compares the operating point with the Goodman and Soderberg lines and the Gerber parabola; the Goodman-Smith diagram shows the maximum and minimum stresses of the cycle against the permissible region; the Marin cascade shows how much surface finish, size and reliability lower the endurance limit; the von Mises domain places the normal and shear stresses relative to the yield ellipse.
When it isn't enough
The method applies to steels with a defined endurance limit, for infinite life and constant-amplitude loads. Loads that vary over time, finite life, welds, non-ferrous materials or complex geometries require damage accumulation and often a finite element model. These are the verifications of the calculation and simulation service: if you need help, contact us for a consultation.
FAQ
Which STEP files can I upload?
.stp or .step files exported as solids from any CAD (SolidWorks, Inventor, Creo, NX, Fusion, FreeCAD) in the AP203, AP214 or AP242 protocols. Recognition works on shafts of revolution; for assemblies or prismatic parts the proposed profile must be checked.
Is the STEP file uploaded to a server?
No. Reading, analysis and the 3D view happen in the browser, on your computer. Only the calculation and visualisation libraries are downloaded from the network, not your model.
What Kt value should I use for a shoulder?
It depends on the ratio between fillet radius and diameter and on the step in diameter. For r/d = 0.05 and D/d = 1.5 in bending Kt is about 2; with r/d = 0.1 it drops towards 1.7. If you upload the STEP file the tool calculates it automatically.
What's the difference between static and fatigue verification?
The static check makes sure the section doesn't yield under the maximum load, even if it occurs only a few times. The fatigue check makes sure the section withstands millions of alternating load cycles without a crack forming. A shaft must pass both.
What's an adequate safety factor?
In general engineering a value between 1.5 and 2 in fatigue and at least 1.5 static is normally sought, higher when loads and material properties are uncertain or when a failure has serious consequences.