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Found 10 results

1. ## Shape Optimization, Frequency Response Modal Analysis: Minimize dynamic Stiffness

Hello, i want to reduce the dynamic stiffness of a rubber bearing by changing the geometry. I have an approximate idea of the "optimized" geometry of this rubber bearing therefore I created morphvolumes and changed the specified area (solid elements) by translating the handles. I saved these changes as shapes which are my design variables. I know that the optimum is between the initial model and the changed model. I want to do an optimization with optistruct to find the optimum. To reduce the dynamic Stiffness i need 3 responses and an equation (dont know another way so far). The calculation of the dynamic Stiffness is simple: Cdyn = Force/Displacement. First i defined an equation with the dequation-panel: F(x,y)=x/y --> where x is the "frf force (ELFORCE)" and y the displacement (frf displacement) which are two of the three responses. The Last response is "function" which includes the dequation and the other two responses defined before. I would like to minimize the response "function" (which is the dynamic stiffness). But it's not possible to create an objective which minimizes my response "function", i get following error: *** ERROR # 1812 *** Multiple responses are assigned to the DESOBJ objective function. A MINMAX/MAXMIN objective function definition with DOBJREF should be used instead. Number of responses = 1000 1) Do you know what the maximum number of responses is? (It's an frequency response analyis from 0 Hz to 3000 Hz with an increment of 3, thats why its 1000 responses (i guess)) . I created an obj reference "dobjref" which includes the response "function", then i created MINMAX objective.This works, and i can start the optimization but here i have some questions: 2) When i define the obj reference i can choose neg and pos reference. What can i do with these references? 3) I don't really know what this minmax function does. Does it minimize the maximum value of the equation? It is not my goal to minimize only the maximum value of the equation, it's rather minimizing the area of the function. 4) Is it normal that optistruct finds a solution after 2 iterations? I have two different shapes and i would expect that it takes a lot of time and iterations to find the optimum. I guess i did something wrong or forgot sth. Sry for asking so many questions and sry for my bad english. I thank you so much in advance. Regards, Fatih Uysal
2. ## OptiStruct Composite optimization number of ply shapes

In a free size optimization, i always get from a ply, 4 different ply shapes, How can i change this number?
3. ## Shapefile Template for OSSmooth

Hello, I would like to generate my own shapefiles to be used with OSSmooth to create new topologies. Is there any information on how the file is constructed? I understand that the beginning of the file has element ids with their associated relative densities but there are many other fields whose contents are unknown to me. Thank you in advance, -Eric
4. ## Shape (?) Optimization for 1D Elements

Hey guys, I was wondering if it is possible to setup the following optimization problem. Lets say I have a set of nodes and bar elements. This framework has some loads and boundary conditions. I am not sure if the node position of each node is optimal regarding compliance. I would like to define "shapes" for the nodes where I can set some pertubations e.g. Node x can move in a sphere of radius y. I have not seen this kind of optimization although I think it must be possible from an algorithmic point of view. Any suggestions? Thanks!
5. ## Shape optimisation error

I am doing the shape optimisation and I am getting the responce error. H:/New folder (2)/Opti/sh2.fem "DSYSID 1 Shapeopt" *** ERROR # 1000 *** in the input data: Incorrect data in field # 4. I have given the responce from... responses>response name> response type = static stress> Prop(select components,inlet,outlet,wall)> create. But its not working.
6. ## Change Soft convergence criterion

Hello, when i start an optimization with optistruct the calculation is finished after 1 Iteration. In the Output-file i found following Information: Soft convergence criterion satisfied; the design did not change during the last Iteration. What does this mean? I already did a lot of successful shape-optimizations but in this case i don't really know why the shape didn't change. I changed the default OBJTOL value from the opti control card but the problem still occurs. The most interesting thing is: When i change the inital value in the shape panel to 0.5 I don't have any problems and the optimization finds the best shape. When I start with an inital value of 0.0 then i get the problem with the soft convergence criterion. Thank you Greets, Fatih Uysal
7. ## OptiStruct Composite optimization

Hello, I've built a composite I beam and optimatized the thickness plys only, but, I would like to get the best height for the beam web. At the moment i'm doing this manually, comparing the results of the composite optimization for differents heights, but for each height, at this moment, i have to build all the laminate again, from zero. How can i automatized this process? or at least do it in a smart way. It's possible to do a shape optimization for composites to get the best web height without it buckling or failure? more info about the simulation: In the optimization process, for the free size stage: obj :min compliance constrains: vfrac 0.3 for the size stage: obj: min mass constrains: -buckling modes 1, 2 and 3 λ >1 -max displacement of the node on the center of the beam < 12mm -Tsai Hill failure criteria < 1 The files are attached Thanks: Lucas Pereira cat_A_optimization_freesize.hm cat_A_optimization_size.hm
8. ## ERROR # 7315 No DSHAPE grids are on the boundary

Hello, I am new to Optistruct and having a repeating error for my 1D linear static free shape optimization of truss. When I try to run it w/Optistruct, the error that I get is: *** ERROR # 7315 *** No DSHAPE grids are on the boundary. Any ideas about a possible reason for this error? I checked card of DSHAPE and everything looks ok. Thanks, kosa26
9. ## Hypermorph radius and rotate

Hi, I give the radius value in the corners, and the component direction separately as shapes. I will use these shapes as DOE in Hyperstudy. But when I change the two shapes at the same time, a useless shape like the one in figure 'radiusandrotatecombined' appears. How can I design a proper shape by correcting this situation? Thank you, rotateandradius.hm
10. ## After the analysis shape change

Hı everyone, My structure has very less weight and size. I want to lattice optimization and I do. But shape of my structure is changing. shape is very thin. I think this can be due to the weight. Can you help me? Thank you. First picture my structure, Secondly figure at the end of the analysis.
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