Dynamic Loads Topology Optimisation in Optistruct

Hi,  

The problem consists of a connecting rod submitted to axial loads which define the phases of admission (traction) and combustion (compression). 

I am trying to run the following optimization:      

• 2 load steps :        
  • Traction        
  • Compression    
• 2 responses :        
  • Volume        
  • Compliance    
• 1 constraint :        
  • 60% Volume    
• 1 objective :        
  • Minimize compliance  

 

I managed to run a direct transient analysis for the two separate load cases. 

I tried running a topology optimization for one of the load cases but an error occured with the following message:  

 

*** ERROR # 557 ***  DRESP1 2 is not referenced from within a static or an MBD SUBCASE. 

This type of response must be specified from within a static or an MBD  SUBCASE. 

This error occurs in DESOBJ 2. 

 

I would like to know:     

1. How can I create alternating load steps to simulate the traction and compression phases   
2. If it is possible to run an optimization with these dynamic loads 

 

Thank you !