Unfortunately, the damping factor is problem dependent; therefore, you must rely on experience from previous runs. Compare the viscous forces (VF) with the overall forces in the analysis, and ensure that the viscous forces are relatively small compared with the overall forces in the model. Compare the viscous damping energy (ALLSD) with the total strain energy (ALLIE), and ensure that the ratio does not exceed the dissipated energy fraction or any reasonable amount. The viscous damping energy may be large if the structure undergoes a large amount of motion. The automated procedure of computing damping factors well for many applications. However, there are cases where the computed damping factor is either too small, thus not controlling the instability, or too high, thus leading to inaccurate results. These problems are more likely to occur when using a constant damping factor—the damping factor is computed in the first increment, which may not be representative of behavior in the rest of the step. For example, consider a sequentially coupled thermal-stress analysis in which a mechanical analysis reads temperatures from a previous transient thermal analysis. Typically the thermal analysis exhibits a diffusive process, where rapid changes in temperature occurs early in the analysis and minor changes in temperature occur once steady state is reached. In such a case Abaqus will compute the extrapolated strain energy based on the temperatures corresponding to the time of the first increment (in this case there may be a significant change in temperature for the first increment), thus yielding a larger then expected extrapolated strain energy. This in turn leads to a damping factor that is too large, resulting in inaccurate results. If one of the automatic stabilization methods is not working appropriately, you can try using the other automatic stabilization method; the adaptive stabilization scheme is generally preferred. Alternatively, you can try directly specifying the damping factor.
Unfortunately, the damping factor is problem dependent; therefore, you must rely on experience from previous runs. Compare the viscous forces (VF) with the overall forces in the analysis, and ensure that the viscous forces are relatively small compared with the overall forces in the model. Compare the viscous damping energy (ALLSD) with the total strain energy (ALLIE), and ensure that the ratio does not exceed the dissipated energy fraction or any reasonable amount. The viscous damping energy may be large if the structure undergoes a large amount of motion. The automated procedure of computing damping factors well for many applications. However, there are cases where the computed damping factor is either too small, thus not controlling the instability, or too high, thus leading to inaccurate results. These problems are more likely to occur when using a constant damping factor—the damping factor is computed in the first increment, which may not be representative of behavior in the rest of the step. For example, consider a sequentially coupled thermal-stress analysis in which a mechanical analysis reads temperatures from a previous transient thermal analysis. Typically the thermal analysis exhibits a diffusive process, where rapid changes in temperature occurs early in the analysis and minor changes in temperature occur once steady state is reached. In such a case Abaqus will compute the extrapolated strain energy based on the temperatures corresponding to the time of the first increment (in this case there may be a significant change in temperature for the first increment), thus yielding a larger then expected extrapolated strain energy. This in turn leads to a damping factor that is too large, resulting in inaccurate results. If one of the automatic stabilization methods is not working appropriately, you can try using the other automatic stabilization method; the adaptive stabilization scheme is generally preferred. Alternatively, you can try directly specifying the damping factor.
1470137427519_Automatic%20stabilization%20of%20unstable%20problems.docx