For considering the DoC for the *MAT252 model, another option is to scale the material parameters directly within the Envyo application. As a result, a series of material cards is created and written out to the Envyo application's output file. In order to avoid writing out a modified material card for every element, in this approach, a clustering of elements is conducted, where each cluster represents a unique part with its own material. Otherwise, the strategy is almost equivalent to the one discussed in Output: Initial Stress Cards with the difference that here, each element has its own material definition instead of each integration point. The overall procedure is described below, and see Output: New *PART and *MAT252 Cards for the corresponding commands:
Read in the DoC-values stored as history variables at the integration points in the *INITIAL_STRESS_SOLID cards.
Compute the average DoC for each element.
Based on their average DoC values, sort the elements into buckets, which are characterized by their lower and upper DoC values. You must set the number of buckets and the ranges these cover.
For every bucket, create a new *PART card and corresponding *MAT252 card. The material properties for the given part are modified based on the average DoC associated with bucket limits. To achieve this, the functions in Output: Initial Stress Cards are evaluated first. Then, the resulting values are used according the seven equations below, where the parameters on the left-hand side are parameters for the new, modified *MAT252 card, while the values on the right-hand side with the ref extension refer to the parameters of the reference *MAT252, which is modified depending on the DoC. All elements that fall into a given bucket are added to that part.
(5–5)
(5–6)
(5–7)
(5–8)
(5–9)
(5–10)
(5–11)
For more information about these parameters, see the LS-DYNA User's Guide.
The *MAT252 material model represents an adhesive material and as such, it is typically augmented by the *MAT_ADD_COHESIVE keyword. Since depending on the number of requested buckets, a large amount of new parts and material cards are created, and adding the *MAT_ADD_COHESIVE cards by hand can potentially be a tedious task. Thus, these cards are also generated by the Envyo application based on certain inputs.