What’s new in Abaqus 2021- Contacts and Constraints

This is our second blog on What’s new series of 2021 and it primarily talks about solver contact and constraints enhancements.

  • Foams enhancements:

This is a big achievement in foams modeling. Foams always had a problem of penetrations due to large deformation. The explicit solver has been modified to address these penetrations. First lets understand why penetrations tend to be on higher side for foams.

ℎ𝑝𝑒𝑛𝑒𝑡𝑟𝑎𝑡𝑖𝑜𝑛_𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒 = 𝑟ℎ/Δ𝐿 × 𝜀𝑁𝑜𝑚_𝑁𝑜𝑟𝑚𝑎𝑙𝐷𝑖𝑟 𝐸𝑙𝑎𝑠𝑡𝑖𝑐 × 𝐿𝑜𝑟𝑖𝑔_𝑒𝑙𝑒𝑚_𝑑𝑖𝑚𝑒𝑛𝑠𝑖𝑜𝑛

The first term on right hand is called linear penalty stiffness. Its value is 0.2 for standard and in the range of 3 for explicit. As foams are very compressible, the higher value of strains combined with higher value of penalty stiffness, particularly in explicit, create large penetrations. The new explicit in 2021 accounts for less penetrations for a given mesh size and linear penalty stiffness without much difference in total number of increments.

  • Wear output enhancements:

CRICWORK field output has been introduced in 2021x FD03 to help understand wear. The field output variable calculates frictional work associated with each surface node. By default, half of friction work of a contact constraint is associated to each surface in contact. This value can be modified in surface property definition.

  • Better visualization of interference fit:

The COPEN has been modified in Abaqus explicit 2021x FD03 to represent true penetration distance. In previous releases COPEN was observed as portion of penetration distance that contact stiffness acted upon.

  • Edge to edge contact enhancement:

The dynamic feature edge criteria was introduced in explicit in 2018x to make number of contact edges variable with time. The activation of contact edges is a function of edge angle. The algorithm is much robust than perimeter edges only option and yet much faster than “all edges” option. The dynamic feature edge criteria has been further enhanced in 2021xFD04 to reduce simulation time by further 35 percent.

  • Submodeling enhancement:

A new method has been developed in 2021x FD03 to address submodeling through field import of sim output from previous simulation. It leverages mapping capabilities of the co-simulation engine. It is based on interpolating results from a previously run global model. So there is some on the fly computation involved that makes this method more memory saving compared to the traditional method.

  • “Master and Slaves” get renamed

I am sure next few statements are going to be a big surprise for traditional Abaqus users. The master and slave terminology will be deprecated from Abaqus 2021xFD04. MASTER->MAIN and SLAVE->SECONDARY. It does not mean that old terminology will give a fatal error message or warning. However, an informational message will appear in .DAT file as follows:

***NOTE: For *CLEARANCE, the MASTER parameter is changed to MAIN and the SLAVE parameter is changed to SECONDARY. The MASTER and SLAVE parameters will no longer be supported in a future release.

There are no plans to stop supporting the old parameter as of now.

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