, STABILIZE=dissipated energy fraction Abaqus/CAE module: Create Step: General: any valid step type: Basic: select Specify dissipated energy fraction from the Automatic stabilization field Considerations when the first increment is unstable or singular There are cases where the first increment is either unstable or singular (due to a rigid body mode). In such cases it is not possible to obtain a solution to the first increment without applying some damping. Therefore, some damping is already applied during the first increment. The damping factor used for the initial increment is chosen such that the average element damping matrix component, divided by the step time, is equal to the average element stiffness matrix component multiplied by the dissipated energy fraction. If the calculated strain energy change in this increment indicates that the solution without damping is stable, the damping factor is recalculated based upon the energy method described previously. However, if the strain energy change indicates that the solution is unstable or singular, the initially calculated damping factor is maintained, and a warning message is issued indicating that the amount of damping applied may not be appropriate. In many cases the amount of damping may actually be rather large, which can affect the solution in ways that are not desirable. Therefore, if the above mentioned warning message is issued, check the viscous forces (VF) and compare them with the expected nodal forces to make sure that the viscous forces do not dominate the solution. If necessary, follow the stabilized step with another step in which stabilization is not used or with a step in which a much smaller damping factor is used. Directly specifying the damping factor You can also specify the damping factor directly. Unfortunately, it is generally difficult to make a reasonable estimate for the damping factor unless a value is known from the output of previous runs; the damping factor depends not only on the amount of damping but also on mesh size and material behavior. Input File any of the following options to specify the
, STABILIZE=dissipated energy fraction Abaqus/CAE module: Create Step: General: any valid step type: Basic: select Specify dissipated energy fraction from the Automatic stabilization field Considerations when the first increment is unstable or singular There are cases where the first increment is either unstable or singular (due to a rigid body mode). In such cases it is not possible to obtain a solution to the first increment without applying some damping. Therefore, some damping is already applied during the first increment. The damping factor used for the initial increment is chosen such that the average element damping matrix component, divided by the step time, is equal to the average element stiffness matrix component multiplied by the dissipated energy fraction. If the calculated strain energy change in this increment indicates that the solution without damping is stable, the damping factor is recalculated based upon the energy method described previously. However, if the strain energy change indicates that the solution is unstable or singular, the initially calculated damping factor is maintained, and a warning message is issued indicating that the amount of damping applied may not be appropriate. In many cases the amount of damping may actually be rather large, which can affect the solution in ways that are not desirable. Therefore, if the above mentioned warning message is issued, check the viscous forces (VF) and compare them with the expected nodal forces to make sure that the viscous forces do not dominate the solution. If necessary, follow the stabilized step with another step in which stabilization is not used or with a step in which a much smaller damping factor is used. Directly specifying the damping factor You can also specify the damping factor directly. Unfortunately, it is generally difficult to make a reasonable estimate for the damping factor unless a value is known from the output of previous runs; the damping factor depends not only on the amount of damping but also on mesh size and material behavior. Input File any of the following options to specify the
1470137427519_Automatic%20stabilization%20of%20unstable%20problems.docx