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Found 2 results

  1. Hi, After doing the HyperMesh morphing tutorials and the Optistruct shape optimization tutorials, I created a shape optimization file on my own. It consists of a cylindrical cantilever which is loaded sideways at the free end. The goal is to find an optimized cross section. The inner part remains unchanged, for the outer part (connected using equivalence) three different shapes are defined (elliptical morphing along x, along y and circular stretching). When minimizing the volume of the cantilever while limiting the stress in z-direction, the expected elliptical cross section results and the optimization constraint is fulfilled: Shape_opt_stress_constr.hm When limiting the displacement in load direction at the end of the cantilever, the cross section shrinks to a circle of minimum diameter and the displacement is much larger than the specified 0.15. Shape_opt_disp_constr.hm Isn't it possible to use displacement dconstraints for shape optimization? The solver (Optistruct) doesn't recognise the constraint violation and minimizes the volume to the extreme, leading to very high displacements. Thanks in advance for any inputs.
  2. Hey all! I hope you can help me! I´m doing an optimization for a university project of a bracket but get no convergence and high constraint violations. The model: See the design volume (blue) in Screenshot 1. The yellow areas are not being optimized. There the loads are applied and the model is constrained at the two yellow areas on the top. I had to use TET10 elements because auf geometrical issues. 6 forces apply to the model. I use quite big elements but this is for doing quick calculations...I don´t want to wait 2 hours to see if it is working... but I think this should not be a problem here?! Optimization: I want to reduce the weight/volume. So objective is to minimze volume (I have tried Mass, volfrac). At the nodes, where I´ve applied the forces (basically in the middle of the yellow areas), I have set displacement constraints (betweent 0.5mm and 2mm). I use min member size controll of 0.4 and a stress constraint of 450(N/mm²) My Problem: The solver always reaches the iteration limit of 80 without converging below the tolerance and ist violating the constraints massively. (screenshot). I have tried to let the solver run 120 iterations but without any usable result. Here are the ones with 120 iterations: When I view the results given by the solver at iteration 80 it looks like it is about to find a solution that looks acceptable in my eyes. but the strange thing ist that the density values of the structure often are below 0.1 and not almost 1 as they shpould be. I have tried to check if it ist because of quite low loads (max about 165N) but with a scale factor of 10 the same element densities appear. Results with density values > 0.05: Results with density values > 0.2: Results with density values > 0.5: Has anybody an idea what I am doing wrong? Should I increase the number of iterations further?
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