$ elastic plate vs. rigid ground $ First, a normal contact force is established via prescribed motion. $ Next, a horizontal force is ramped starting at t=0.01e-3. $ The resulting horizontal motion is nonzero starting at t=0.01e-3 but is small and oscillatory until the $ applied force overcomes static friction at around t=0.025e-3 (see x-force in rcforc). $ Friction energy (sleout) resembles the horizontal motion. $ horforc.png is illustrative. It shows the applied horizontal force and the contact friction $ force. The friction force oscillates about the applied force for a bit (thus the $ horizontal velocity is near zero during this time) but then the friction tops out at the static $ friction force = (static friction coef. * normal force) while the applied external force continues to climb. $ It's when these 2 forces diverge the the near-static-equilibrium is violated and motion (and frictional contact energy) take off. $ *KEYWORD *part_move 1,0,.02 *CONTACT_automatic_SURFACE_TO_SURFACE 1 2 3 3 0 0 1 1 0.1000000 *CONTROL_CONTACT 0.0000000 0.0000000 0 0 0 0 0 0 0 0 0 0.0000000 0 0 0 $,1 $*database_ncforc $1.e-9 *database_binary_intfor 8.e-7 *TITLE energy-friction *CONTROL_TERMINATION 4.00000-5 0 0.0000000 0 0.0000000 *CONTROL_TIMESTEP 0.0000000 0.1000000 0 0.0000000 0.0000000 0 0 0 *CONTROL_ENERGY 2 2 2 2 *DATABASE_BINARY_D3PLOT 2.00000-8 0 *DATABASE_EXTENT_BINARY 0 0 0 0 0 0 0 0 0 0 0 0 0 0 *DATABASE_GLSTAT 4.00000-7 *DATABASE_RCFORC 2.00000-8 *DATABASE_SLEOUT 2.00000-8 *DATABASE_bndout 2.00000-8 *MAT_ELASTIC 1 7.33000-4 3.00000+7 0.3300000 *MAT_RIGID 2 7.33000-4 3.00000+7 0.3300000 0.0000000 0.0000000 0.0000000 1.0000000 7.0000000 7.0000000 0.0000000 0.0000000 0.0000000 0.0000000 0.0000000 0.0000000 0.0000000 0.0000000 *SECTION_SHELL 1 0 0.0000000 0.0000000 0.0000000 0.0000000 0 0.02,.02,.02,.02 *SECTION_SHELL 2 0 0.0000000 0.0000000 0.0000000 0.0000000 0 0.02,.02,.02,.02 *PART 1 1 1 0 0 0 0 0 *PART 2 2 2 0 0 0 0 0 *NODE 1-2.000000030E-01 0.000000000E+00-2.000000030E-01 0 0 2 2.000000030E-01 0.000000000E+00-2.000000030E-01 0 0 3-2.000000030E-01 0.000000000E+00 2.000000030E-01 0 0 4 2.000000030E-01 0.000000000E+00 2.000000030E-01 0 0 5-4.100000262E-01-1.000000225E-06-2.100000083E-01 0 0 6-2.050000131E-01-1.000000225E-06-2.100000083E-01 0 0 7 0.000000000E+00-1.000000225E-06-2.100000083E-01 0 0 8 2.050000131E-01-1.000000225E-06-2.100000083E-01 0 0 9 4.100000262E-01-1.000000225E-06-2.100000083E-01 0 0 10-4.100000262E-01-1.000000225E-06 2.100000083E-01 0 0 11-2.050000131E-01-1.000000225E-06 2.100000083E-01 0 0 12 0.000000000E+00-1.000000225E-06 2.100000083E-01 0 0 13 2.050000131E-01-1.000000225E-06 2.100000083E-01 0 0 14 4.100000262E-01-1.000000225E-06 2.100000083E-01 0 0 *ELEMENT_SHELL 1 1 1 2 4 3 2 2 5 10 11 6 3 2 6 11 12 7 4 2 7 12 13 8 5 2 8 13 14 9 *DEFINE_CURVE 1 0 0.0000000 0.0000000 0.0000000 0.0000000 0.00000000E+00 0.00000000E+00 3.99999999E-06 1.00000000E+02 4.40000003E-05 1.00000000E+02 *DEFINE_CURVE 2 0 0.0000000 0.0000000 0.0000000 0.0000000 0.00000000E+00 0.00000000E+00 7.99999998E-06 0.00000000E+00 4.40000003E-05 5.50000034E-02 *DEFINE_CURVE 3 0 0.0000000 0.0000000 0.0000000 0.0000000 0.00000000E+00 0.00000000E+00 3.99999999E-06 1.10000015E-04 4.40000003E-05 1.10000015E-04 *SET_NODE 1 1,2,3,4 *BOUNDARY_PRESCRIBED_MOTION_SET 1 2 2 3-1.0000000 $ 1 1 2 2 1.0000000 0 $ apply horizontal force which is resisted by friction *LOAD_NODE_SET 1,1,1011, 0.25 *DEFINE_CURVE 1011 0,0 0.01e-3,0 0.03e-3,30 0.05e-3,30 *END