Chapter 8 – Analysis Step Types

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Updated on 2025-10-18

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The step types and their options available in Solvix are:

Static Step #

  • Name.
  • Solver: Default, PaStiX, Pardiso, Spooles, Iterative scaling, Iterative Cholesky.
  • Nlgeom: On/Off (enable or disable the geometric non-linearity – large deformations and large displacements).One has to be careful when using the Default incrementation and amplitudes – incrementation is not automatically adjusted to account for the spread a
  • Incrementation: Default/Automatic/Direct (the incrementation options listed below are for Automatic incrementation).
  • Max increments – maximum number of increments in the step.
  • Time period – time period of the step.
  • Initial time increment – initial value of time increment in the step.
  • Min time increment – minimum time increment allowed.
  • Max time increment – maximum time increment allowed.
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Slip wear step #

  • Name.
  • Solver: Default, PaStiX, Pardiso, Spooles, Iterative scaling, Iterative Cholesky.
  • Nlgeom: On/Off (enable or disable the geometric non-linearity – large deformations and large displacements).
  • Incrementation: Default/Automatic/Direct (the options listed below are for Automatic incrementation).
  • Max increments – maximum number of increments in the step.
  • Time period – time period of the step.
  • Initial time increment – initial value of time increment in the step.
  • Min time increment – minimum time increment allowed.
  • Max time increment – maximum time increment allowed.
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Boundary displacement step #

  • Name.
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Frequency step #

  • Name.
  • Solver: Default, PaStiX, Pardiso, Spooles, Iterative scaling, Iterative Cholesky.
  • Perturbation: On/Off (when it’s set to On, preload from the previous static step can be included).
  • Storage: Yes/No – stores eigenvalues, eigenmodes, mass and stiffness matrix in a binary form in a file jobname.eig for further use in steady state dynamics or modal dynamics step.
  • Number of frequencies – number of eigenfrequencies to compute.
  • Lower frequency bound – lower bound of the frequency range.
  • Upper frequency bound – upper bound of the frequency range.
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Buckle step #

  • Name.
  • Solver: Default, PaStiX, Pardiso, Spooles, Iterative scaling, Iterative Cholesky.
  • Perturbation: On/Off (when it’s set to On, preload from previous static step can be included).
  • Number of buckling factors – number of buckling factors desired (default: 1).
  • Accuracy – accuracy desired (default is 0.01).
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Modal dynamics step #

  • Name.
  • Solver: Default, PaStiX, Pardiso, Spooles, Iterative scaling, Iterative Cholesky.
  • Perturbation: On/Off (when it’s set to On, preload from previous static step can be included).
  • Steady state: On/Off (can be used to continue a modal dynamics calculation until steady state has been reached).
  • Damping type:
    • Off
    • Constant: Damping ratio.
    • Direct: Damping ratios (table: Lowest mode, Highest mode, Damping ratio)
    • Rayleigh: Alpha, Beta
  • Max increments – maximum number of increments in the step.
  • Initial time increment – initial value of time increment in the step.
  • Time period – time period of the step (when steady state is off) or Relative error – relative error for the solution to be considered as steady state (when steady state is on).
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Steady state dynamics step #

  • Name.
  • Solver: Default, PaStiX, Pardiso, Spooles, Iterative scaling, Iterative Cholesky.
  • Perturbation: On/Off (when it’s set to On, preload from previous static step can be included).
  • Harmonic: Yes/No (switches between harmonic periodic loading and non-harmonic periodic loading).
  • Lower frequency bound – lower bound of the frequency range.
  • Upper frequency bound – upper bound of the frequency range.
  • Number od data points – number of data points within the frequency range.
  • Bias – distribution bias of the data points within the frequency range (1 for equal spacing).
  • Damping type:
    • Off
    • Constant: Damping ratio.
    • Direct: Damping ratios (table: Lowest mode, Highest mode, Damping ratio)
    • Rayleigh: Alpha, Beta
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Dynamic step #

  • Name.
  • Solver: Default, PaStiX, Pardiso, Spooles, Iterative scaling, Iterative Cholesky.
  • Nlgeom: On/Off (enable or disable the geometric non-linearity – large deformations and large displacements).
  • Alpha – amount of numerical damping (between -1/3 and 0).
  • Solution procedure :
    • Implicit/Implicit– implicit structural and implicit fluid (currently unsupported) computations.
    • Implicit/Explicit– implicit structural and explicit fluid (currently unsupported) computations.
    • Explicit/Implicit– explicit structural and implicit fluid (currently unsupported) computations.
    • Explicit/Explicit– explicit structural and explicit fluid (currently unsupported) computations.
  • Relative to absolute : On/Off (needs to be enabled when the coordinate system in the previous step was attached to a rotating system and the coordinate system in the present dynamic step should be absolute).
  • Damping type:
    • Off
    • Rayleigh: Alpha, Beta
  • Incrementation: Default/Automatic/Direct (the incrementation options listed below are for Automatic incrementation).
  • Max increments – maximum number of increments in the step.
  • Time period – time period of the step.
  • Initial time increment – initial value of time increment in the step.
  • Min time increment – minimum time increment allowed, should be set to the desired minimum time increment if mass scaling is to be used in explicit dynamic calculations.
  • Max time increment – maximum time increment allowed.
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Heat transfer step #

  • Name.
  • Solver: Default, PaStiX, Pardiso, Spooles, Iterative scaling, Iterative Cholesky.
  • Steady state: Yes/No – switching between the steady state and the transient analysis
  • Incrementation: Default/Automatic/Direct (the options listed below are for Automatic incrementation).
  • Max increments – maximum number of increments in the step.
  • Time period – time period of the step.
  • Initial time increment – initial value of time increment in the step.
  • Min time increment – minimum time increment allowed.
  • Max time increment – maximum time increment allowed.
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Uncoupled temperature-displacement step #

  • Name.
  • Solver: Default, PaStiX, Pardiso, Spooles, Iterative scaling, Iterative Cholesky.
  • Nlgeom: On/Off (enable or disable the geometric non-linearity – large deformations and large displacements).
  • Steady state: Yes/No – switching between the steady state and the transient analysis
  • Incrementation: Default/Automatic/Direct (the options listed below are for Automatic incrementation).
  • Max increments – maximum number of increments in the step.
  • Time period – time period of the step.
  • Initial time increment – initial value of time increment in the step.
  • Min time increment – minimum time increment allowed.
  • Max time increment – maximum time increment allowed.
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Coupled temperature-displacement step #

  • Name.
  • Solver: Default, PaStiX, Pardiso, Spooles, Iterative scaling, Iterative Cholesky.
  • Nlgeom: On/Off (enable or disable the geometric non-linearity – large deformations and large displacements).
  • Steady state: Yes/No – switching between the steady state and the transient analysis
  • Incrementation: Default/Automatic/Direct (the options listed below are for Automatic incrementation).
  • Max increments – maximum number of increments in the step.
  • Time period – time period of the step.
  • Initial time increment – initial value of time increment in the step.
  • Min time increment – minimum time increment allowed.
  • Max time increment – maximum time increment allowed.
  • Output frequency – integer N indicating that only results of every N-th increment will be stored.

Postscript #

One has to be careful when using the Default incrementation and amplitudes – incrementation is not automatically adjusted to account for the spread and range of amplitude data points. One should change the time period, initial and maximum time increment accordingly.

The slip wear step and the boundary displacement step (available only after adding the slip wear step) are not standard Solvix analysis procedures and thus require additional explanation. They are based on the Archard’s model [1] and can be used to estimate the progressing sliding wear between contact surfaces. This linear model predicts the volume of the removed material due to the wear process. Since the model neglects the changes in the geometry of the contacting surfaces during multiple wear cycles, a multistep numerical procedure can be used to determine the wear parameters better. Archard’s wear model was developed based on the results of the wear experiments between metals in dry conditions.

The implementation of the sliding wear analysis in the Solvix is general in terms of model geometry, boundary conditions and loads and involves the following assumptions:

  • the continuous wear process between the parts can be discretized into several repeating wear cycles,
  • the wear occurs only on a softer surface in the contact pair,
  • the geometry of the contacting surfaces does not change during a single wear cycle,
  • the dimensionless wear coefficient remains constant during the entire wear process.

Based on these assumptions, a finite element model of a single wear step is first prepared. The model must accurately capture the evolution of the contact conditions through time; thus, a nonlinear time-dependent analysis is required. The wear computation starts after the completion of the analysis. All computations of the wear parameters are done in the finite element nodes of the slave surface, which are in contact during the wear cycle. Nodal pressure and slip values are computed from the contact pressure slip fields. The nodal wear depths are then calculated using equation (2) and material properties at contact nodes. The processing of a single wear cycle completes with the computation of the contact surface geometry change due to wear, defined by nodal wear displacements. Single-cycle wear displacements are calculated by multiplying the scalar nodal wear depth value by the nodal surface normal. Wear displacements of a single cycle are then added to the wear displacements of the previous wear cycles.

The combined wear displacements are then considered during model preparation for the next wear cycle. The initial finite element mesh of the model is updated by the combined nodal wear displacements considering the model boundary conditions. If a zero boundary condition is prescribed on a nodal degree of freedom where the wear displacement component is computed, the wear displacement component is set to zero. The analysis of the symmetric wear models is possible in this way. The procedure repeats until the final number of wear cycles is reached.

References:

  1. J. F. Archard and W. Hirst, “The wear of metals under unlubricated conditions”, Proc. R. Soc. London. Ser. A. Math. Phys. Sci., vol. 236, no. 1206, 1956.
  2. X. Shen, L. Cao, and R. Li, “Numerical simulation of sliding wear based on Archard model”, in 2010 International Conference on Mechanic Automation and Control Engineering, MACE2010, 2010.