ABAQUS User-defined field (USDFLD) subroutine for stochastic strength field

The Fortran code (USDFLD) was implemented in Abaqus/Standard to introduce a stochastic strength field based on a power law-accelerated Weibull distribution and to define a bilinear elastic-plastic model for silk materials. The subroutine randomly assigns a strength to each integration point at the start of the analysis, evaluates the maximum principal stress, updates the plastic evolution parameter (FIELDVP) and fracture parameter (FIELDVF), and records their values in user-defined field variables (FIELD).