CM2 FEM® SDK /release 5.1.0 Preview 2
- 5.1.0 Preview 2
- September, 2021
- All CM2 FEM® SDK
- Major release of the CM2 FEM® SDK
- Due to changes in the API, client applications must be recompiled against the new headers
- Preview version. API is still subject to changes.
- Major version. Due to changes in the API, client applications must be recompiled against the new headers.
- Lib names suffix is
_51for this series.
- Win32 and Linux x86 (32-bit) builds shall be soon deprecated.
- Augmented Lagrange Method (ALM) to enforce more precisely the constraints (
The constraints are satisfied by applying still a high penalty stiffness but much lower than with the Pure Penalty Method (PPM) together with a few correction iterations.
Pros: The constraints are satisfied accurately and the condition numbers of the global stiffness matrices stay reasonable.
Cons: Needs some additional iterations and internal forces (i.e. reactions) inside the constraints are null (replaced with intern Lagrange multipliers).
ALM is enabled by default but can be disabled and return to PPM through the new
settings_type::sort_modes_by_PF_flagto sort the dynamic modes by decreasing effective participation factor (most effective modes first).
sort_modes_by_PF_flag = false(lowest frequencies first as before).
- Can now smooth Tresca equivalent stresses on nodes with the new
- Can also now smooth signed Tresca with the
FEM_NODES_TRESCA_SIGNED(signed with the sign of the trace of the stress tensors).
- Now works also on
FEM_NODES_VON_MISES_SIGNED(signed with the sign of the trace of the stress tensors).
Note that signed Tresca and Von Mises stresses can flip between positive and negative values when trace is close to zero.
FEM_matrix, FEM_Zmatrix, FEM_states
- New members
pop_backto append/remove columns and states.
- New unsymmetrical elasto-plastic laws
These scalar laws are made of two elasto-plastic laws, one for traction (positive strains) and one for compression (negative strains).
The laws are of the same class (both
law_scalar_ep_piecewise_linear) but can have different diagrams (data) and state limits.
pulley_rigid: new sigmoid smoothing (controlled by a new
lambdaparameter) to make the diagrams continuous and derivable (thus helping the Newton algorithm).
TRAPEZEmomentums are now allowed on linear 2-node beams (used to be silently discarded).
These distributed momentums give however only approximative results (exact for
TRAPEZEforces, exact also for
PUNCTUALforces and momentums).
DBL_MAX). Experienced users only.
numerical_model_base::set_relaxations: new output parameters
unsigned& fictitious1to access the underlying fictitious nodes.
For the same purpose,
fem::hingeis now equipped with new members
unsigned get_fictitious0() constand
unsigned get_fictitious1() const.
- New functions
Tresca_stresseswith optional parameter
All types of models and elements
- Major optimisations in the computation of elementary matrices and vectors:
- Speed-ups in the 30-60 % range for
- Speed-ups in the 10-30 % range for other models and elements.
- Speed-ups in the 30-60 % range for
- Major optimisations (on top of the above improvements in elementary computations).
Total speed-ups can be massive.
- On many load cases, the assembly of RHS is parallelized over load cases instead of within each load case (coarser grain parallelism).
- On many load cases with different Dirichlet conditions, the resolution of RHS is parallelized over load cases (was single threaded).
- Simpler and more reliable penalty factors.
Now based on the diagonal terms associated to the penalty DOFs in the global stiffness matrix (instead of a characteristic value based on the constitutive laws’ parameters).
They are now computed only when penalty models are present (
In addition, these penalty factors are now stored inside the solutions
FEM_statesto avoid their recomputation.
- Simpler and more reliable artificial drilling stiffness.
Now based on rotation diagonal terms of the actual elementary stiffness matrices instead of a characteristic value based on the constitutive laws’ parameters (which could be null or irrelevant)
- Bug with prescribed values on free DOFs in multiple load cases.
- Wrong output values in
- Bad stress diagram with non-linear beam models.
- Bad stress diagram with rod models (linear and non-linear).
- Intern parameters of elasto-plastic solid constitutive laws weren’t properly stored.
This could cause states to be non-equilibrated (leading to wrong restarts, bad reactions…)
- Doc fixes and clarifications.
- With the new formula for the penalty factors (see above), small numerical differences vs previous versions can be expected (when constraints models are present and Pure Penalty Method is still used).
The new default minimum penalty factor (now 1, was 1E12) can also cause some numerical differences.
elementary_server, solver_condensation_static, solver_energy, solver_reactions
reset_penalty_factorsremoved from the
runfunctions (not needed any more because the penalty factors are passed through the
inputsparameter and do not need to be recomputed).
- The Dirichlet boundary conditions
loads_mgr::record_DOF_prescribed_value(s)are no longer cumulative.
When several Dirichlet values are associated to the same DOF, the last one prevails (overwrites any previous one).
The Neumann boundary conditions
- At threshold
e_ithe stiffness used to be the right value
Now the value is the _average_ value
k(e) = 1/2 (k_i + k_i+1)(even when leaving the default
lambda = DBL_MAX, i.e. no smoothing).
- The offset vector represents the physical position of the mass minus the position of the node (used to be the other way round).
solver_modal, solver_modal_ldrv, solver_modal_gyroscopic, solver_buckling_Euler
- Deprecated data fields
B_modes… have been removed.
- Deprecated data fields
B_modes_requested_memory… have been removed.
They gain the optional parameter
Tresca_stressesto sign with the sign of the trace of the stress tensors.
- The orthonormal Eigen vectors computed by
eigen_pairs(3D) are now always positively oriented (trihedral with determinant = +1).