Mass-scaling refers to a technique whereby nonphysical mass is added to a structure in order to achieve a larger explicit timestep.
For quasi-static solutions, optimum efficiency is obtained by arranging for all elements in the model to require the same timestep. This can be achieved by adding or subtracting mass from each element. To perform an analysis of this type, enter a positive value of DT2MS on *CONTROL_TIMESTEP. The mass of every element in the model will then be adjusted such that the timestep is SCFT*DT2MS (SCFT is normally 0.9). Note that the analyst must still select a suitably long event time for the simulation to ensure that the behaviour is sufficiently quasistatic.
Note also that if DT2MS is set to a negative value, masses are changed only for those elements whose timestep would otherwise be less than the desired timestep. With DT2MS positive, the masses of all elements are changed.
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Mass-scaling is a term that is used for the process of scaling the element's mass in explicit simulations to adjust its timestep. The primary motivation is to change (usually increase) the global compute timestep which is limited by the Courant's stability criteria. LS-DYNA allows two different types of mass-scaling using the DT2MS parameter from *CONTROL_TIMESTEP with the default set to no mass-scaling. When DT2MS is less than zero, LS-DYNA adds mass of each element whose timestep is below abs(DT2MS) such that the element's updated DT is equal to abs(DT2MS). When DT2MS is greater than zero, LS-DYNA adds mass to elements whose DT is below abs(DT2MS) and "removes" mass from elements whose DT is greater than zero. DT2MS>0 is seldom used while DTM2<0 is frequently used for overcoming the smallest computed timestep. Care must be taken when using DT2MS<0 to ensure that the added mass does not have an adverse effect on the simulation accuracy. It is common practice to limit the percentage of added mass to less than 5% (at part level) in dynamic simulations. Optionally, users can set ENDMASS in *CONTROL_TERMINATION to terminate a simulation based on percentage of added mass based on the total mass of the model. When ENDMAS is greater than zero, LS-DYNA terminates when the percentage of added-mass reaches ENDMAS and a report of up to 20 nodes (sorted in the descending order of its added mass due to mass-scaling) is written to both standard output and D3HSP file. It must be noted that the percentage of added-mass is based on total mass of the model which included rigid body, rigid walls, etc... and could be misleading if looked at the global level. LS-DYNA outputs the percentage of added mass at component level which is a better indicator of amount of added mass due to mass-scaling. The concept of mass-scaling for both options of DT2MS is graphically illustrated below.
Link to the 2nd definition http://blog2.d3view.com/overview-of-mass-scaling/
For quasi-static solutions, optimum efficiency is obtained by arranging for all elements in the model to require the same timestep. This can be achieved by adding or subtracting mass from each element. To perform an analysis of this type, enter a positive value of DT2MS on *CONTROL_TIMESTEP. The mass of every element in the model will then be adjusted such that the timestep is SCFT*DT2MS (SCFT is normally 0.9). Note that the analyst must still select a suitably long event time for the simulation to ensure that the behaviour is sufficiently quasistatic.
Note also that if DT2MS is set to a negative value, masses are changed only for those elements whose timestep would otherwise be less than the desired timestep. With DT2MS positive, the masses of all elements are changed.
========
Mass-scaling is a term that is used for the process of scaling the element's mass in explicit simulations to adjust its timestep. The primary motivation is to change (usually increase) the global compute timestep which is limited by the Courant's stability criteria. LS-DYNA allows two different types of mass-scaling using the DT2MS parameter from *CONTROL_TIMESTEP with the default set to no mass-scaling. When DT2MS is less than zero, LS-DYNA adds mass of each element whose timestep is below abs(DT2MS) such that the element's updated DT is equal to abs(DT2MS). When DT2MS is greater than zero, LS-DYNA adds mass to elements whose DT is below abs(DT2MS) and "removes" mass from elements whose DT is greater than zero. DT2MS>0 is seldom used while DTM2<0 is frequently used for overcoming the smallest computed timestep. Care must be taken when using DT2MS<0 to ensure that the added mass does not have an adverse effect on the simulation accuracy. It is common practice to limit the percentage of added mass to less than 5% (at part level) in dynamic simulations. Optionally, users can set ENDMASS in *CONTROL_TERMINATION to terminate a simulation based on percentage of added mass based on the total mass of the model. When ENDMAS is greater than zero, LS-DYNA terminates when the percentage of added-mass reaches ENDMAS and a report of up to 20 nodes (sorted in the descending order of its added mass due to mass-scaling) is written to both standard output and D3HSP file. It must be noted that the percentage of added-mass is based on total mass of the model which included rigid body, rigid walls, etc... and could be misleading if looked at the global level. LS-DYNA outputs the percentage of added mass at component level which is a better indicator of amount of added mass due to mass-scaling. The concept of mass-scaling for both options of DT2MS is graphically illustrated below.
Link to the 2nd definition http://blog2.d3view.com/overview-of-mass-scaling/
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