The AMendate program allows to build an optimization model, to start this optimizationon a local level as well as via an interface with a server and to visualize the results.
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Starting the Program
When the program is started, the projects menu appears first. In the "Local working directory" the storage location of the projects can be seen. The location can be chosen arbitrarily. In the "Projects" tab, an existing project can be renamed and opened, or a new project can be created. In addition, in the "Example Projects" tab, already prepared example optimizations can be opened and used as a template or tutorial.
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Below are three further tabs, which are described in the following:
Objects/Surfaces
First, all STL files required for the optimization are loaded into the program in the "Objects/Surfaces" tab. This can be done either via the "Plus" button or by drag-and-drop from the Windows Explorer. Incorrectly loaded or revised objects can be removed individually or replaced by a new version. A removed file will not be considered during the optimization, but it will not be deleted from the project folder so that it can be loaded again.
An STL file is activated by clicking on it, so that a property field opens in the lower area.
- Here you can change the name and select the material.
- The material database can be extended with specific material properties via the gear next to the material field. (The Material file is saved in your personal AppData folder.)
- For exactly one volume, the assignment must be defined as a design space. Several design spaces within a model are not possible, even though the volume of the design space may be shaped as complex as desired.
Boundary Conditions
In the Boundary conditions area, the "Plus" button is used to create the boundary conditions required for optimization. To do this, enter a name and select the concerned space. The load case relevant for the boundary condition (several are also possible) is then activated in the lower list of load cases. The boundary condition can be either a force, a fixation or a moment. Forces, fixations and moments are always specified in component notation in the main coordinate directions
Although the units within a model must be consistent, the choice of the unit system is left to the user (see Settings). The metric system is provided with the units kilogram, millimeter and Newton (kg, mm, N). STL files are often stored in mm and forces are given in N. Accordingly, the unit of the appropriate moment is Nmm
For the different boundary conditions, there are different approaches for the structure and design of the optimization model. In the following, different possibilities for the generation of different boundary conditions are presented and special features of the software are pointed out. A specified boundary condition (force, fixation, moment) always refers to the entire object. To support the input process, an area of a volume can be clicked directly after activating the check box "Force" or "Moment" and thus a direction orthogonal to the surface can be defined. This can be particularly advantageous for round surfaces, hollow cylinders of bolting points or bearing seats. By dragging the mouse pointer, an approximate load size can be defined directly afterwards. The exact values of the spatial directions can then be corrected and adapted via the input fields.
- Loads
- Forces are specified per object (volume) and distributed evenly over this object.
- For a surface load, the active surface with thickness 0 must be loaded as a separate object (.STL file).
- If only a single force is to act as a point load, a separate (very small) volume must be generated for this. Here it should be pointed out that an idealized point load in reality always corresponds more to an area/volume load!
- Fixations
- Displacements can be locked in the x, y and z directions.
- The activation of all displacement restrictions corresponds to a fixed fixation.
- A floating bearing can be created by selecting only one or two displacement restriction(s).
- For optimization, each direction must be locked (activated) at least once on any object, so that no rigid-body movement can occur. (Exception when using symmetry, see below).
- Moments
- Moments also affect entire objects and can be defined in x, y and z directions. The right hand rule can be used to imagine the direction of rotation.
- Moments also affect entire objects and can be defined in x, y and z directions. The right hand rule can be used to imagine the direction of rotation.
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Optimization (Definition of an Optimization)
Using the previously defined materials and boundary conditions, an analysis can already be performed for the selected geometry. In order to carry out a geometry optimization, further parameters must be set.
Design Type
First of all, a distinction can be made between the three settings "filigree", "normal" and "massive". This influences the design, which means that "filigree", "massive" or "normal" structures are formed during optimization. An example for the different settings is shown in the picture below. It should be noted that an optimization result with the "Filigree" setting is not automatically lighter than a "Massive" setting, because many fine struts can make the weight heavier than a few massive ones.
Figure 1: filigree, normal, massive
Calculation Type
Further it can be selected whether only an "estimation", an "optimization" or an "optimization" up to the printable design should take place. In most cases, an "estimation" only takes a few minutes and gives an overview of the weight and stress development that an optimization can achieve under the given boundary conditions. The "optimization" can take up to a few hours, depending on the conditions, and provides a detailed/high resolution design proposal. The "Manufacture" option takes the longest time, because here the resolution at the end of the optimization is significantly increased in order to obtain a good printable surface and structure of the component in detail.
Figure 2: estimate, optimize, manufacture
Optimization Goal
Then the optimization target must be defined. With AMendate, a target stress is specified that serves as the reference during optimization. For this purpose, a fatigue strength value of the material can be used and provided with an additional safety factor. The software does not take any safety factors internally into account when determining the design. This must be included in the maximum stress by the engineer. Through the stress-oriented optimization, an optimally uniformly loaded component is developed, in which above all the transitions between struts and surfaces are formed optimally and with few stress increases. The standard unit of stress MPa = Nmm^2 corresponds to the previously mentioned system of units
Symmetry
An axis symmetry around the coordinate origin can be selected for the calculation of symmetrical components. A model structure with complete geometry is recommended for this. For the calculation, however, only the positive area of the spatial axes is used, the result is then mirrored into the negative area. Both the geometry and the boundary conditions are mirrored. Therefore, for loads beyond the zero point (e.g.: area load of a symmetrical bridge), only the load portion for the positive coordinate space may be specified (halved force, corresponding to half the area, e.g.: only force on one of the bridge sides). For a correct calculation ALL boundary conditions must be symmetrical, this applies to fixations, forces and moments. Errors can easily creep in, especially when defining moments.
Configuration File
Finally, all the specified information can be viewed in the configuration file. Other special settings are also possible here, which are of particular interest to simulation experts.
Together with the stl files, the configuration file is the only input parameter for optimization.
The following settings can be made under User Setting:
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An analysis of the design space is carried out.
Further settings can be made in the FEM area:
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solver=
Extern
CG
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Conection to solver:
Externer solver from AMendate z.B. AMendateCudaSolver.
Uses an integrated conjugated gradient solver.
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Definition of the maximum available memory for the stiffness matrix. Corresponds to the resolution ot the model and thus determines the calculation time.
With GPU Solving, the GPU RAM must not be exceeded (1 GB to 14 GB if necessary with CPU also over 100 GB). We are mainly using Nvidia Quadro P5000 with 16GB Memory
The following output files can be selected:
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export_stl_name_MC_Smooth_intersection
intersectionDetail =
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The current optimization result is intersected with the design space on a voxel basis in each iteration.
0...3 Setting the resolution on the basis of which the intersection is performed. A good value here is 2.
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Results
The first iteration is displayed as soon as a result is available. Further iterations are displayed as soon as they are calculated. You can use the control in the Result iterations field to switch manually between the different iterations or to view an automatic process.
The AMendate Log can be used to track the current progress in the form of the console output.
The result file is an STL file, which can usually be produced directly using an additive process.
Older result files can also be selected and displayed in the project.
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Model Generation and Visualization of an Analysis
Both optimization results and original components can be analyzed. After both analysis have been performed, the results can be compared and the performance of the optimization can be evaluated.
For the analysis of an object, the model generation is carried out exactly as for an optimization. All required files (Design/Nondesign space) are imported and the corresponding boundary conditions and load cases are created. The object to be analyzed must be activated as a design area in the Objects/Surfaces area.
The Optimization area does not have to be filled in, but the configuration file must be opened in this area and the command "onlyFEM" added under "User Settings". This only performs an analysis without optimization. In addition, the resolution can be changed under FEM to achieve more accurate results. The resolution of an optimization / analysis is always estimated according to the stl with the largest volume within the working folder. If the stl file of the original design space remains in the folder, the resolution is determined by this volume.
The result of the analysis shows the stresses and displacements in the selected object.