B modeling ============== Characteristics of modeling ------------------------ In this modeling, we use the operator DYNA_VIBRA (see [:ref:`U4.53.03 `]) with the relationship DIS_CHOC. The integration diagram is DEVOGE. In modeling B, we consider the skate and the plane as two mobile structures. Each structure is then modelled by a node and an element of type POI1. Node :math:`\mathrm{NO2}` is supposed to be locked, it materializes the plane of friction. Relationship conditions between degrees of freedom are imposed on node :math:`\mathrm{NO1}` (which models the skate) so that the movement is unidirectional in the :math:`\theta` direction. An obstacle of type BI_PLAN_Z (two moving parallel planes separated by a game) is used to simulate the sliding plane. We choose to use the Oy axis as the generator of this plane, i.e. NORM_OBST = (0., 1., 0.). By default, the origin of the obstacle is located halfway between nodes :math:`\mathrm{NO1}` and :math:`\mathit{NO}2`. It remains to define the parameters DIST_1 and DIST_2 which represent the thickness of material around the shock nodes. For there to be a reaction force from the plane on the system, the system must be slightly pressed into the plane obstacle by a distance :math:`\mathrm{\delta }n` such as: :math:`{F}_{n}={K}_{n}\cdot \mathrm{\delta }n`. Like :math:`{F}_{n}=\mathrm{mg}`, we then have :math:`\delta n=\mathrm{mg}/{K}_{n}`. We considered a normal shock stiffness of :math:`20N/m` (fictional stiffness that only makes sense to generate a reaction force from the plane on the system), so we have :math:`\mathrm{\delta }n=\mathrm{0,5}m`. Knowing that the two nodes :math:`\mathit{NO}1` and :math:`\mathit{NO}2` are geometrically confused, we choose for example: DIST_1 = DIST_2 = :math:`\mathrm{\delta }n/2`. Tangential shock stiffness: :math:`{K}_{T}=400000N/m`: it is greater than the stiffness of the oscillator for the stopping phase to be modelled correctly. No time used for time integration: :math:`{5.10}^{-4}s`. Characteristics of the mesh ---------------------------- Number of knots: 2 Number of meshes and types: 2 POI1 Tested sizes and results ------------------------------ Values of the displacements (in meters) in the direction of the oscillator for the times when the sign of the speed changed over the time period :math:`(0;0.3s)`. .. csv-table:: "**Identification**", "**moment (s)**", "**Reference**" ":math:`\mathrm{DY}=\mathrm{r2}\mathrm{cos45}` "," :math:`\pi \times {10}^{-2}` ", "—4.596E—4" ":math:`\mathrm{DY}=\mathrm{r3}\mathrm{cos45}` "," :math:`2\pi \times {10}^{-2}` ", "3.182E—4" ":math:`\mathrm{DY}=\mathrm{r4}\mathrm{cos45}` "," :math:`3\pi \times {10}^{-2}` ", "—1.768E—4" ":math:`\mathrm{DY}=\mathrm{r5}\mathrm{cos45}` "," :math:`4\pi \times {10}^{-2}` ", "3.536E—5"