Bredt's formula
The Bredt's formulas are a fundamental part of the strength of materials . They form a basis for the calculation of shear stresses and deformations in components with closed, thin-walled hollow cross-sections under pure torsional stress . Subsequently, thus can also Torsionswiderstände and thrust midpoints calculated.
The formulas originally come from Rudolf Bredt , who published them in the VDI Journal in 1896 .
1. Bredt's formula
: Shear flow (constant) in [N / mm], with the shear stress in [N / mm²] and the wall thickness t in [mm] | |
: Torsional moment in [Nm] | |
: area enclosed by the cross-sectional center line in [mm²] |
2. Bredt's formula (specific twist angle)
: Twisting (twisting) | |
: Run coordinate along the member axis in [mm] | |
: Shear stress | |
: Shear modulus in [N / mm²] |
Torsion resistance (St. Venant's twist resistance)
The Bredt formula can be used to determine the torsional resistance (i.e. the torsional area moment of the 2nd degree ) of closed thin-walled profiles:
with the length of the component in [mm].
This formula is often referred to as the second Bredt formula.
swell
- ^ Rudolf Bredt ( Memento from September 5, 2007 in the Internet Archive )
Web links
- Construction dictionary online - Bredtsche formulas
- HTWG Konstanz, lecture Technical Mechanics (PDF file; 140 kB)
literature
- Karl-Eugen Kurrer : History of Structural Analysis. In Search of Balance , Ernst and Son, Berlin 2016, pp. 556f and 573f, ISBN 978-3-433-03134-6 .