how to add a preload of spring in Ansys workbench ls-dyna?

- October 31, 2019 at 7:11 pm
  
  pengchengyin
  Subscriber
  
  Hi all,
  
  Recently, I am using workbench ls-dyna to simulation the drop test of a rack server. But I so confused about how to add a preload of spring in workbench ls-dyna. When I try to add the preload of spring at the setting of spring, the same as the image shows at below. it doesn't work. I want to ask, does anybody know how to add preload of spring in workbench ls-dyna?
  
  Thank you.
- October 31, 2019 at 8:37 pm
  
  Sandeep Medikonda
  Ansys Employee
  
  It can be done by using Insert>Bolt Pretension object either in a dynamic relation phase or a regular transient phase.
  
  See the Help on this
  
  How to access the ANSYS Online Help
- October 31, 2019 at 9:04 pm
  
  pengchengyin
  Subscriber
  
  Hi Sand,
  
  Thank you for replying me. I also have a question. should I need to delete the spring setting and use a cylinder to instead of spring by using bolt pretension?
  
  Thank you
- November 1, 2019 at 12:03 am
  
  pengchengyin
  Subscriber
  
  and if I delete spring, the beam connection cannot instead of spring which has damping. But if I don't delete spring, the beam connection cannot add at the same place as spring which has kinematic incompatibility. Is that right?
- November 1, 2019 at 2:16 pm
  
  Sandeep Medikonda
  Ansys Employee
  
  When you are using bolt pretension, you wouldn't need to model the spring and if beam connections are available I don't see why these can't be used. Yes, but definitely not both.
  
  The velocities are damped but only in the dynamic relaxation phase? See this video.
  
  https://www.youtube.com/watch?v=ATMq_fi35Uk
- November 1, 2019 at 2:53 pm
  
  pengchengyin
  Subscriber
  
  sorry, I can't open that link. But I thought spring can affect the model damping when model drop on the gorund, which beam connection can not do. is that right? Sorry I am a new guy for workbench ls-dyna. I really appreciate you replying.
- November 1, 2019 at 2:56 pm
  
  pengchengyin
  Subscriber
  
  Or I can use beam connections and put the longitudinal damping of spring in Global Damping?
- November 1, 2019 at 3:01 pm
  
  Sandeep Medikonda
  Ansys Employee
  
  Why do you need it to be damped? Is a cushion between the 2 parts physical behavior?