This article provides a comparison of the various Radioss interfaces. 

 

Here is a table comparing Lagrangian contact interfaces:

 

Here is a table comparing ALE interfaces:

 

The behavior of a Type 2 interface changes based on the selected SpotFlag parameter.
Based on the SpotFlag parameter, a tied interface can have failure defined and even switch to penalty formulation, as opposed to being a kinematic constraint. Below is a table comparing all the available options for the SpotFlag parameter in /INTER/TYPE2

 

Regarding the choice between Spotflag = 27 or 28:

• These 2 formulations transmit moments from secondary nodes to elements on the master surface
  (see notes #19 and #20 in the documentation for /INTER/TYPE2)
  
  
• Spotflag = 28 is the only formulation that transmits the drilling moment
  (But only if the master surface is based on shell elements)
  For this reason, SpotFlag = 28 should be used when modelling spotwelds
  
  
• With Spotflag = 27, there is no addition of mass at t = 0
  This differs from Spotflag = 28, which can add mass when the main surface is based on solid elements
  (see note #21 in the documentation for /INTER/TYPE2)
  
  
• Spotflag = 27 should be used for connections to solid components
  
  
• Spotflag = 28 should be used for connections to shell components

 

 

Below is a link to the "Contact Definition for Crash Analysis" YouTube video comparing interfaces as well:
https://www.youtube.com/watch?v=kQnMhFM9iAE

This video covers the following topics:

• Typical Applications of Interfaces
• Variations of Interfaces
• Most Used Interfaces Types for Impact
• Interface Type 7
• Interface Type 25
• Example Model Description
• Results
• Interface Stiffness Formulation
• Sub Interface: /INTER/SUB
• Thickness at /PART