/PERTURB/PART/SHELL

Block Format Keyword This option can be used to study the robustness of a design by generating different thickness values for every shell element in the specified part group. The random noise scale factors can have either a normal (Gaussian) distribution or random distribution.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/PERTURB/PART/SHELL/ID
perturb_title
F_Mean Deviation Min_cut Max_cut Seed Idistri
grpart_ID parameter

Definition

Field Contents SI Unit Example
ID Perturb identifier.

(Integer, maximum 10 digit)
perturb_title Perturb title.

(Character, maximum 100 characters)
F_Mean Mean value of the random noise scale factor.

(Real)
Deviation Standard deviation for the normal distribution. Only used when Idistri=2.

(Real)
Min_cut Minimum value for random noise scale factor. Must be entered when using Idistri=1, random distribution.

If random value is < Min_cut, random value is replaced with Min_cut.

(Real)
Max_cut Maximum value for random noise scale factor. Must be entered when using Idistri=1, random distribution.

If random value is > Max_cut, random value is replaced with Max_cut.

(Real)
Seed Seed used for random noise generation.
= 0 (Default)
For each run, a random (different) seed value is calculated and written in the Starter output file.

(Integer) 3
Idistri Distribution type.
= 0 (Default)
Set to 2.
= 1
Random distribution.
= 2
Normal (Gaussian) distribution.

(Integer) 4
grpart_ID Part group identifier.

(Integer, maximum 10 digits)
parameter Parameter identifier.
THICK (Default)
Thickness of shell elements in /PROP/SHELL.

(Character, maximum 20 characters. Starting at any location in the input field)

Example

#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/PERTURB/PART/SHELL/1
set Random Noise with normal distribution on Shell Thickness (model unit : g-mm-ms)
#         Mean_value           Deviation             Min_cut             Max_cut      Seed   Idistri
                 1.8                0.02                0.7                  1.2      7182         2
#grpart_ID           parameter
    123456               THICK
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/PERTURB/PART/SHELL/2
set Random Noise with random distribution on Shell Thickness
#         Mean_value           Deviation             Min_cut             Max_cut      Seed   Idistri
                 2.1                                     0.9                 1.1      7182         1
#grpart_ID           parameter
    123457               THICK
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/GRPART/PART/123456
test_grpart
         1         2
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/GRPART/PART/123457
test_grpart
         3
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#ENDDATA

Comments

  1. Two computations with the same values, Seed will return exactly to the same results. Currently the only valid parameter is THICK.
  2. Due to discretization, the random noise in the model will not exactly match the input random noise values. However, the model’s actual random noise values are calculated and output in the Starter output file.
  3. Seed is an integer used to initialize random number generation for the random noise. The Seed can be changed to study sensitivity or model robustness. If Seed=0, a random (different) seed value is calculated for each run and written to the Starter output. To rerun an analysis with Seed=0, use the Seed value written to the Starter output in the original analysis as input in the analysis rerun.
  4. If Idistri=1, the distribution of the scale factors will be random.
    If Idistri=2, the normal distribution of the scale factors will have the following probability density function.
    Figure 1.

    perturb_density