A　series　of　finite　element　simulations　of　frictionless　contact　deformation　between　an　elastic-power　plastic　sinusoidal　asperity　and　a　rigid　flat　are　carried　out　to　explore　the　influence　of　the　ratio　of　yield　stress　to　elastic　modulus　on　the　evolution　of　contact　deformation　regime.　The　deformation　behavior　comprises　five　regimes　with　four　transitional　states　corresponding　to　four　critical　events　determined　by　curve-fitting　of　simulation　results.　The　transitional　boundaries　between　neighboring　deformation　regimes　are:　(1)　initiation　of　plastic　deformation;　(2)　plastic　deformation　just　reaches　the　top　surface;　(3)　the　whole　contact　surface　just　experiences　plastic　deformation;　(4)　the　attainment　of　maximum　mean　contact　pressure.　It　is　found　the　mean　contact　pressures　at　transitional　events　are　closely　associated　with　yield　stress　and　characteristic　stress,　which　can　be　used　as　normalization　parameters.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.