Bolts from M8 to M64

Pictured: Bolts from M16 to M64

Calculations for bolted connections

  • Comparison and evaluation of tightening
  • Local fatigue calculations for threads and bolt head
  • Damage analysis and cracking and fracture models
  • Tensile tests on bolts and threaded components
  • (High-frequency) oscillation tests on bolt assemblies

Calculation of nonskid prestressed connections

Nonskid preloaded bolted connections (designation GV) are, for example in lattice towers for wind turbines used. Of crucial importance is the technical execution of the friction surfaces in order to also ensure the desired boundary sliding force can.

The loading of the connection results from the average height proportions of the components to be connected. In the example below a double-shear GM compound was chosen with a prestressed bolt. Between the plates and washers are additional contact elements to allow sliding or friction effects. Essentially, the following calculation steps were required to:

  • Model geometry of the double shear GM connection
  • Specify constitutive equations and boundary conditions
  • Apply biasing force with Pretension elements
  • Define contact algorithm with corresponding coefficients of friction
  • Load schedule (eg, tensile stress at the edge of the sheets)
  • Structural analysis
  • Post Processing
FE-model for GM connection
Contact pressure
Contact status
Friction tension

Damage analysis with fracture mechanics methods

Fracture pattern in the thread of a bolt

The SKI engineering company has fracture mechanics methods and local fatigue concepts, to assess the durability of screws under static and dynamic loading can. For more details please contact us.

Oscillation tests for different types of loading

It can be realized oscillation tests on screws with the following load types:

  • Tension
  • Bending
  • Tension + Bending
  • Torsion

The test frequencies are, depending on Bolts and strain size between 20 and 200Hz.

Resonance test frame for tension
Resonance test frame for tension + bending