5. C modeling#
5.1. Characteristics of modeling#
This modeling corresponds to the direct transient response of the friction pad. We use the DYNA_NON_LINE operator (see [U4.53.01]) with the relation DIS_CHOC. The integration diagram is HHT.
The normal contact direction is the local axis \(X\) which corresponds in the test case to the global axis \(Z\). The sliding plane is the local plane \((Y,Z)\), i.e. the plane \((X,Y)\) in the global coordinate system. We therefore direct the shock element to a node, with the keyword ORIENTATION from the AFFE_CARA_ELEM operator in the following way:
ORIENTATION = _F (MAILLE =” EL1 “, CARA:” VECT_X_Y “,
VALE = (0., 0., -1., -1., 1., 0.))
To be able to obtain a reaction force from the plane on the system, the system must be slightly pressed into the plane obstacle by a distance \(\delta n\) such as: \({F}_{n}={K}_{n}\cdot \delta n\).
The reaction balances the weight of the skate, so we have: \({F}_{n}=\mathrm{mg}\) i.e. \(\mathrm{\delta }n=\mathit{mg}/{K}_{n}\).
We considered a normal shock stiffness of \(20N/m\) (fictional stiffness that only makes sense to generate a reaction force from the plane on the system), so we have \(\delta n=\mathrm{0,5}\) where DIST_1 = 0.5.
The tangential shock stiffness considered is \({K}_{T}=400000N/m\), the Coulomb coefficient is 0.1.
The law of shock behavior is therefore defined as follows in DEFI_MATERIAU:
DIS_CONTACT =_F (RIGI_NOR = 20.0,
DIST_1 = 0.5,
RIGI_TAN = 400000.0,
COULOMB = 0.1)
We use a time step of \({5.10}^{-4}s\) for time integration.
5.2. Characteristics of the mesh#
Number of knots: 1
Number of meshes and types: 1 POI1
5.3. Tested sizes and results#
Values of the movements in the direction of the oscillator for the times when the sign of the speed changes.
instant |
reference value |
Tolerance |
\(\mathrm{\pi }/100\) |
|
1.0e-04 |
\(2.0\mathrm{\pi }/100\) |
|
1.0e-04 |
\(3.0\mathrm{\pi }/100\) |
|
1.5e-04 |
\(4.0\mathrm{\pi }/100\) |
|
1.0e-03 |