Introduction

Basil is a finite element program which calculates quantities which describe  stress  and strain in non-linear viscous materials, for strains up to the of order 100%.   The calculations  describe  very  viscous  Earth materials which undergo irreversible large-strain deformation at  high  temperature  and over long time periods, under the influence of body forces and surface tractions.  Sybil  is the post-processing program that permits basil solutions to be examined in detail using an interactive graphical user interface.

The program permits a spatially variable Newtonian  or  non-Newtonian  viscosity  in a 2-D geometry with boundary conditions on traction and/or velocity.  It is also  possible  to include  a single fault or discontinuity in the problem in a dynamically self consistent way.  The 2-D deformation  field represents  either plane-strain deformation, or it permits a specified distribution of normal stress in the third  direction.   The  latter is referred to as the thin viscous sheet formulation when the normal force is due to  gravity  acting on variations of the layer thickness.  Plane-stress calculations are a specific case of the thin viscous sheet formulation.
 

• Examples
• Basil and Sybil Man pages

The programs basil and sybil have been developed  mainly  at Monash  University  since  1988,  and before that at ANU and Harvard.  The present set of  programs  has  been  developed mainly  by  Greg  Houseman,  Terence  Barr  and  Lynn Evans.  Important contributions by others,  particularly  by  Philip England  during  the  early stages of development are gratefully acknowledged.  Comments on, or questions about,  basil and sybil should be sent to greg@earth.leeds.ac.uk