The Mass Target option is an alternative optimisation constraint that overrules the usual approach based on a stress goal. The optimisation attempts to reach a user specified global target mass, which has to be defined as a relative value. However, locally the design will still be a stress driven one, meaning regions with low and high stresses will be avoided as good as possible.
Please consider that the stress goal (respectively tensile strength and safety factor) still have to be set to a meaningful value. It will be used to calculate and display the local optimization achievement. However the amount of stress or local optimization achievement will rather be a simulation output than an input.
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