General engineering analysis

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Adaptive analysis | Fatigue Analysis

Adaptive Analysis

The Adaptive Meshing Wizard (available only with LUSAS Analyst) automatically runs an adaptive analysis with specified parameters until the results obtained are less than a pre-defined error, or until the maximum number of specified iterations is exceeded. Graphs of global error against iteration number are produced and contour plots of adaptivity error can be produced to show areas where further mesh refinement or unrefinement would be achieved.

adaptivity graphThe Adaptive Meshing Wizard requires the following parameters to be defined:

  • Minimum and Maximum element spacing - this sets the minimum and maximum allowable element sizes in model units.
  • Maximum % change - sets the maximum allowable percentage change in element size during a mesh refinement.
  • Global relative % error - sets the target error. The mesh will be successively remeshed until the global relative % error falls below this value.
  • Error norm factor - sets an artificial factor that scales the errors to aid mesh refinement.
  • Maximum number of iterations - sets the maximum number of remeshes allowed.
  • Cancel facility - allows the adaptive process to be stopped after each remesh.
  • Use default background grid and spacing - allows the control of the mesh density using a background grid.

adaptive modelAfter the adaptivity parameters have been set the initial model is solved and an adaptive loop is executed which remeshes the model, solves the model and checks the global % error obtained from this mesh. This adaptive loop is repeated until either the global error is within the required tolerance or the maximum number of iterations has been reached. A graph of global error against iteration number is drawn and updated after each iteration.

Error contours for initial mesh and after 2 adaptive iterationsWhen the adaptive analysis is finished results may be viewed on the mesh or deformed mesh in exactly the same way as for other analyses. In addition, contours of adaptivity error can be plotted to show the quality of the mesh used. These contours do not represent the % error but highlight the required increase or decrease in mesh density. The target value for the adaptivity error is therefore 1. Areas of the model with an error contour value greater than 1 indicate that more elements are required in these regions. Similarly, areas of the model with an adaptivity error value of less than 1 indicate that less elements could be used.

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