The timestep of autodyn too small

- February 11, 2022 at 6:50 am
  
  faceless_man
  Subscriber
  
  I'm doing an analysis about shaped perforating charge penetrating a steel cylinder ,autodyn belongs to ansys 17.2 version ，the explosive and lining are Euler solvers, the outer casing and steel cylinder are Lagrangian solvers, the Euler domain mesh size is 0.2*0.2, The mesh size of the Lagrangian part is 0.4*0.4, and the other details are in the attachment. There is a question here. As the analysis progresses, the time step becomes very small. How can I improve the computational efficiency?
- February 11, 2022 at 5:08 pm
  
  Chris Quan
  Ansys Employee
  
  Time step problem could be caused by either Euler elements or Lagrange elements.
  Please check the thickness of the liner. The number of Euler elements through the liner thickness should be at least 3 for proper material transport. More Euler elements are through the liner thickness, more accurate the solution is. It will also help to prevent small time step.
  Also make sure both failure and erosion models are applied to the out casing and steel cylinder. So once they are deformed or penetrated, the material could fail and thus strength is not over-predicted. Furthermore, distorted elements will be removed to prevent the time step problem.
- February 14, 2022 at 1:08 am
  
  faceless_man
  Subscriber
  
  Dearcxquan´╝îmrife. Thank you for replying in your busy schedule
  I have checked that the number of Euler elements through the liner thickness is 7´╝îboth failure and erosion models are applied to the out casing and steel cylinder.When the jet gets closer to the original, the time step gets slower and slower, and the erosion process goes on for a while and then displays "timestep too small, problem terminated"
- February 15, 2022 at 9:26 am
  
  faceless_man
  Subscriber
  
  Dearcxquan´╝îmrife. Thank you for replying in your busy schedule
  I have checked that the number of Euler elementsthrough the liner thickness is 7´╝îboth failure and erosion models are applied to the out casing and steel cylinder.When the jet gets closer to the steel cylinder, the time step gets slower and slower, and the erosion process goes on for a while and then displays "timestep too small, problem terminated"

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