KEVOS® MAKEOS · Strength
Torque Tube and End Weld Check (Shear, Twist, Weld Throat Stress)
Is this round or rectangular tube strong and stiff enough to carry the torque, and is the fillet weld that joins it to its end plate big enough?
Check of a closed thin-walled tube carrying torque and the fillet weld around its end: shear stress, torsional constant and angle of twist of the tube (as the thin-walled tube torsion tool), the shear flow at the end weld from the area it encloses, the weld throat stress and the leg size needed (as the fillet weld strength tool, with the shear flow around the full perimeter), against the allowable stresses and your twist limit.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Section | choice | Shape of the tube section. |
| Outside diameter or width | mm | Outside diameter (round) or outside width (rectangular). |
| Outside height (rectangular only) | mm | Outside height of a rectangular tube. |
| Wall thickness | mm | Wall thickness. |
| Torque | N·m | Torque carried. |
| Length | mm | Length of the tube between the torque points. |
| Shear modulus | GPa | Shear modulus of the tube. |
| Allowable tube shear stress | MPa | Allowable shear stress of the tube. |
| Largest twist | °/m | Largest angle of twist per metre you accept. |
| End weld | ||
| Fillet weld leg | mm | Leg size of the fillet weld all round the tube end. |
| Allowable weld throat shear stress | MPa | Allowable shear stress on the weld throat. |
Method and formulas
- Shear stress = T ÷ (2 A_m t); J = 4 A_m² t ÷ s; twist = T L ÷ (G J) with A_m and s on the wall mid-line (as the thin-walled tube torsion tool).
- Shear flow at the weld q = T ÷ (2 A_w), A_w = area enclosed by the outside of the tube.
- Weld load = q × perimeter, carried by one weld of that length (as the fillet weld strength tool); throat stress = q ÷ (0.707 × leg).
- Example: the tube sees 42.459 MPa and twists 0.98646°/m; the weld throat sees 42.426 MPa (leg needed 1.463 mm).
Limitations
- Closed thin walls; corner radii and stress raisers at the weld toe are ignored.
- Pure torque; bending at the end plate needs adding separately.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a torque tube, drive arm or frame member in torsion
- Size the weld of a tube to its flange
- Compare round and box sections for twist
Who it is for
- Design engineers
- Fabrication engineers
- Structural detailers
What you get
- Tube shear stress, torsional constant and twist
- Shear flow at the weld and weld throat stress
- Weld leg needed
Interpreting the result
- Closed tubes are many times stiffer in torsion than open channels of the same weight.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 295–303, 1476–1486. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
Open the Torque Tube and End Weld Check (Shear, Twist, Weld Throat Stress) calculator
