The　hemispherical　shell　metal　rubber　(HSMR)　exhibits　high　elasticity　and　large　damping　properties.　Compared　with　a　traditional　metal　hemispherical　shell,　this　structure　can　elastically　recover　to　its　original　shape　after　undergoing　a　certain　degree　of　large　deformation.　However,　its　nonlinear　mechanical　properties　cannot　be　accurately　characterized,　limiting　its　extensive　application　in　vibration　damping　and　impact　resistance.　To　address　this　issue,　this　article　develops　a　multiscale　quasistatic　nonlinear　mechanical　model,　deriving　nonlinear　mechanical　models　for　two　deformation　stages:　the　flattening　stage　and　the　denting　stage.　The　influence　of　relative　density　and　shape　parameters　on　the　generation　of　negative　stiffness　is　analyzed.　Experimental　validation　confirms　the　accuracy　of　the　restoring　force,　nonlinear　elastic　force,　and　viscous　damping　force　models　for　HSMR　at　different　relative　densities.　The　results　show　that　relative　density　primarily　affects　the　peak　restoring　force　during　the　flattening　stage,　while　thickness　significantly　influences　the　range　of　negative　stiffness　and　the　minimum　negative　stiffness　during　the　denting　stage.　Furthermore,　for　three　different　relative　densities,　the　residuals　between　the　theoretical　model＇s　restoring　force-displacement　curves　exceed　98.82%,　and　the　maximum　relative　error　between　the　theoretical　model＇s　static　loss　factor　and　the　experimental　results　is　9.80%.　©　2025　Wiley-VCH　GmbH.