Hello Sandeep,

Thanks for the insights. 

 been trying to simulate the standard Hertz/Boresi contact cases for regular geometries (like two parallel cylinders pressing; sphere on plane etc ) for which there is clear theoretical backing to predict the contact stress. When doing this, I initiallly left program controlled stiffness updated for each iteration and this give me good agreement. Convergence was also very smooth. So does this mean, I should not further try to soften the contact by reducing the factor for stiffness? 

  1. What are the general guidelines under which we should start using non-program controlled stiffness?
  2. For typical contact problems lets say gear to gear contact / cam to follower contact/ contacts between pin joints of a mechanism, what is the best approach with normal stiffness? 
  3. Ansys user guide only gives range of normal stiffness that can be used (as you mentioned) and also default penetration tolerance of 10% element depth. But is there a typical best practice as to what is acceptable penetration for the above mentioned typical problems which we encounter in all mechanical assemblies? The basic starter course on contacts in Ansys eLearning suggests even 3% penetration of local deformation /element size is high enough. 
  4. My particular use case is where I'm interested to study if failure due to contact can occur between the pin/links of small hand held devices , say a hand held dremmel under loading. I'm already using slow loading in steps, augmented lagrange, large deformations and other standard best practices. I noticed that the contact pressure (and subsequent equivalent stresses generated) are much dependent on the stiffness value (& penetration) that I choose.

Much obliged for your time & insights.