Users:General FEM Analysis/Analyses Reference/Cutting Pattern

From Carat++ Public Wiki
Jump to: navigation, search


Contents

General Description

Cutting pattern generation determines a plane and (optimally) stress-free geometry which can be reassembled to build a membrane with a certain prestress and shape (as it was determined in Formfinding).


Structure of Equation System

A nonlinear problem is formulated by the equation r = f_int(u) where r specifies the residual vector and f_int defines the internal forces respectively. In general, the internal forces depend on the actual displacement field u. Thus, the equation is nonlinear with respect to the a priori unknown equilibrium displacements.

At the equilibrium point the residual vector is equal to zero. The above specified nonlinear problem is linearized for the actual displacement state and solved e.g. by a Newton-Raphson scheme where the residual vector is used to compute incremental displacements by K_t u_inc = r.


Input Parameters

Parameter Description

Compulsory Parameters
Parameter Values, Default(*) Description
PC-ANALYSIS int : CUTTING_PATTERN Keyword of analysis with analysis ID
SOLVER PC-SOLVER int Linking to a linear solver (direct or iterative)
OUTPUT PC-OUT int Linking to output objects (specifies the type of output format, e.g. GiD)
COMPCASE LD-COM int Linking to computation case object which specify the boundary conditions (loading and supports). Only a single computation case is allowed.
DOMAIN EL-DOMAIN int Linking to the domain the analysis should work on
MAX_ITER_EQUILIBRIUM int Maximum number of equilibrium iterations that are allowed.
EQUILIBRIUM_ACCURACY float Equilibrium accuracy that has to be reached for convergence. The convergence is checked with the L2 norm of the incremental displacements.
PATTERN PART int The parts which should be included in the analysis, separation with comma.
BC_CONFIGURATION TYPE int The type of boundary condition configuration, 4 means largest distance between the supports. For each part, one type must be given.
RELAXATION_METHOD STATIC or NONE or GALERKIN or COMBINED Definition of relaxation method.
FLATTENING_AREA 0 or 1 0... prestress area. 1... mean surface normal.
PATTERNING_METHOD GALERKIN or LS_NR or LS_CG or NONE Definition of the patterning method. GALERKIN... principle of virtual work. LS_NR and LS_CG... optimization problem solved with Newton-Raphson or Conjugate Gradient approach.
Optional Parameters
SEAM_LENGTH to be added Includes the seam lengths into the cutting pattern analysis.

Example of a Complete Input Block

PC-ANALYSIS 1: CUTTING_PATTERN
  DOMAIN = EL-DOMAIN 1
  MAX_ITER_EQUILIBRIUM = 20
  EQUILIBRIUM_ACCURACY = 1e-06
  COMPCASE = LD-COM 1
  OUTPUT   = PC-OUT 1
  PATTERN = PART 1,3
  BC_CONFIGURATION = TYPE 4,4
  SOLVER = PC-SOLVER 1
  RELAXATION_METHOD=STATIC    !NONE, STATIC, GALERKIN, COMBINED
  FLATTENING_AREA=1           !0 ...Prestress area, 1  ...Mean surface normal				
  PATTERNING_METHOD=GALERKIN  !LS_NR, GALERKIN, LS_CG, NONE

Example

The following simple example shows the cutting pattern analysis of two parts from a four-point sail. It uses a static relaxation method, the flattening area is the mean surface normal and a Galerkin approach is used for the patterning method.

Benchmark cutpat 4point.png

The cutting pattern of the two stripes is shown in the picture below.

Benchmark cutpat 4point relaxed.png

References





Whos here now:   Members 0   Guests 0   Bots & Crawlers 1
 
Personal tools
Content for Developers