# coatkuanteen

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1. ## Ply angle optimization with DRESP3

I have tried to optimize ply angles to reach min. nonlinear axial displacement (DRESP3). However ply angles varied very slightly throughout the optimization process and non-optimal solution was found when it stopped. It works fine when I optimize thicknesses instead of ply angles. Any comments on this issue? I use SENSOPT AUTO option for gradient calculation.
2. ## ESLM: Strain Constraints

Thank you! But why do we need the correction factor if we are still in the linear stress-strain relation? ESLs based on displacement should produce strains very close to the ones from (geometrical) nonlinear analysis with linear material property.
3. ## ESLM: Strain Constraints

Could you please forward this query to the development department? Kind regards, Tanut
4. ## ESLM: Strain Constraints

Hi, Small deviation because of different solvers is acceptable, but the difference I am pointing out is more than 100% ! For instance, in the attached files, we look at strain response of the first outer loop iteration (initial design, no optimization yet): NORMAL STRAIN XX, PLY 1, Time=1.0s or equivalent static Subcase 90008 Element ID 40477: RADIOSS value=-6.344E-04, DRESP value=-1.628E-03, Difference=157% Element ID 40245: RADIOSS value=-6.388E-04, DRESP value=-1.587E-03, Difference=148% Element ID 36632: RADIOSS value=-6.276E-04, DRESP value=-1.465E-03, Difference=133% Regards, V55s_t_REF_STRN.eslout V55s_t_REF_STRN_01.h3d
5. ## ESLM: Strain Constraints

When I impose ply strain responses, which can be derived directly from displacement ESLs of the same nonlinear loadcase, as design constraints for a nonlinear loadcase, there are differences between strain response values outputted in .out file and strain contour in .h3d file. In theory, design responses from these two files should match each other but strain values in .out file (optimization values) tend to be larger than what is plotted in .h3d file (analysis values). What could be the reason behind this? Any suggestion on how I can use .h3d strain output as design responses? V55s_t_REF_STRN.fem
6. ## DRESP3 within ESLM

Hi, I would like to know whether OptiStruct ESLM allows the utilization of DRESP3 in static subcases or nonlinear static subcase or both. Thank you very much,
7. ## ESLM: Stopping Criteria

Answer from Altair Development Engineer: "We basically check the number of outer loops w/o any change or improvement in objective/constraint. This is consistent with regular OS optimization. For example, if the number of outer loop w/o any change (see below tolerance) => 2, then convergence is satisfied. Tolerance for maximum constraint violation change – default = 5.0E-3 Tolerance for objective function value change – default = 5.0E-3"
8. ## ESLM: Stopping Criteria

I have used OptiStruct nonlinear-response optimization via Equivalent Static Load Method (ESLM) extensively in my research but would like to know more regarding its stopping criteria of the outer loop i.e. How are convergence criteria defined in order to stop the ESLM (besides ESLMAX max.no. of iteraitons reached)? I know OBJTOL is used in the inner loop (linear static opt. loop), but not sure whether the outer nonlinear-response loop deploys the same criteria. I have not found this info in the User’s Guide. I appreciate your kind support in this matter. Mr.ESLM

thank you!
10. ## ESLM: Stress Constraints

Hi, Is the current Optistruct 13.0 ESLM capable of handling stress/strain constraints from nonlinear analysis i.e. correct generation of ESLs to produce identical stress/strain responses in linear static environment? regards, Mr.ESLM
11. ## INTERNAL PROGRAMMING ERROR in ESLM (tabscr.F)

I have solved the error by deleting all unused design variables. Thanks anyway! Tanut