Hello everyone,

At the moment I’m writing my bachelor thesis about torque shocks to a coupling in a power plant, caused by a lightning impacting in an overhead line.

I want to connect two halves of a flange coupling (drive side and output side) to transmit a torque.

 The whole half is made of 16 symmetric parts shown in the picture below.

The further task of the model is to simulate a variable torque on the output side while a constant torque on the drive side is applied. By this I want to get the tensions inside the bolt and the halves for a later strength calculation

 Background is the following:

In a steam turbine power plant a turbine drives a shaft turning with 3000 RPM (=50Hz). Shaft gives its torque to a following shaft by a coupling (this model). The electric generator converts the mechanical energy into electrical energy and gives it to the power supply.

With a constant supply frequency this steady state remains with this equilibrium of moments. Drive torque = output torque.

Now there’s a lightning striking into an overhead line. The voltage spreads throughout the power supply up to the power plant.

 Because of the lightning there’s a variable counter torque generated by the coils. This counter torque has to be absorbed by the shaft and the coupling.

 We look at the tensions in 3 steps for discovering σmax, σmin, σm and σa considering the variable torque is quasi-static.

1. Step: Steady-State: uniform output moment
2. Step: malfunction: maximum counter torque at generator à output torque decreases (-2%)
3. Step: malfunction: minimum counter torque at generator à output torque increases (+2%)

 Before there are 3 additional steps

a)       Initial step: environment temperature (60°C), defining contacts and cyclic symmetry

b)      Step: Bolt pretension

c)       Step: defining rotational speed and therefore centrifugal forces

 Unfortunately Abaqus is giving me an error all the time while running the job at step c) where the rotational force is applied. The program aborts the job because of too many attempts.

In the following there a some screenshots of the boundary conditions, contact surfaces, symmetry and constraints.

Cyclic Symmetry

Interactions and contacts

contact properties

kinematic coupling, for applying the output torque at 1 point which distributes the torque on alle the surface 

bolt load

centrifugal forces: I don’t know why but the centrifugal force arrows at the symmetry line indicates in different directions?

bc-2: the coupling must turn around its own axis only (in y-direction) and do not translate in radial directions

BC-1: restraint: drive torque shouldn’t run into nothing

I used the student version of Abaqus 6.14. therefore there was a gross mesh on the model. But I also got access to a full version. There Abaqus gives me the same error messages while using the exact same model. So my conclusion is that the error is not based on meshing things.

for a better view I attached a .docx file with this documentation.

please help me, i don't know what i can do to make things work.