## Materials and Methods
### Design Procedure Using the TO Method
#### 2.2.2 TO  
The TO process in the SGD module of the _3 DExperience_ CAD software consists of the following sequential steps:  
1. Defining the TO strategy;
2. Defining the optimization object and its functional elements;
3. Definition of force loads, constraints and their assignment to individual _Load Cases_;
4. Analysis and creation of _Mesh_;
5. Initial strength check of the optimization object;
6. Definition of optimization conditions;
7. TO;
8. Concept generation;
9. Strength check of the generated concepts. TO Strategy  
In the SGD module, the optimization process can be based on different strategies. The TO strategies used are:  
1. Maximize the stiffness for a given part's weight;
2. Minimize weight while respecting constraints;  
Figure 4: Functional elements of semi-finished products for optimization: (**a**) front mount, (**b**) rear mount. Maximize the value of the lowest natural frequency for a given mass of the part. For strategies 1 and 3 it is necessary to define the required weight of the optimized part. The disadvantages of these strategies (especially strategy 1) are that the predefined required weight may not be the lowest possible weight of the component at which the strength requirements are met. Optimization by strategy 2 requires the determination of a limiting factor, such as:  
* The maximum permissible voltage;
* The maximum allowable deformation;
* The maximum/minimum wall thickness;
* The manufacturing technology. In this strategy, material is removed as long as the optimization conditions of the TO are met [17]. In the development of the electric motor mounts, the goal was set to achieve the lowest possible weight at which the components met the strength requirements. Therefore, the strategy chosen for TO was No. 2, _Minimize weight while respecting specified constraints_. Optimization Object and Its Functional Elements  
Before optimization, it is necessary to select which volumes of the object to be optimized are to be preserved and which are to be optimized. The software also informs the user of the masses of the individual volumes. The total weight of the semi-finished front mount is 12.776 kg, of which the weight of the functional volumes is 0.188 kg (1.46%) and the weight of the optimized volume is 12.589 kg (98.54%). The total weight of the semi-finished rear mount is 6.668 kg, of which the weight of the functional volumes is 0.198 kg (2.96%) and the weight of the optimized volume is 6.471 kg (97.04%). Defining _Load Cases_  
The loads applied to the components were obtained from measurements made on a real vehicle during 30 load situations available from a specific manufacturer. The individual load situations represent conditions that may occur during vehicle handling, driving or collision. The measured forces were in the silentblocks (Figure 5, positions 1, 2 and 3) through which the electric motor is attached by mounts to the vehicle frame. These forces are then applied to the inner circumference of the front mount bushings and the rear arm bushing, from which the force effects are transferred to the rear mount. All 30 load situations are represented in the software by _Load Cases_. A _Load Case_ consists of the applied force effects (force, moment,...) and constraints. For the front mount, the _Load Cases_ include (Figure 6a):  
* Two forces (_Force_ type)--reactions from the silentblocks acting on the mount bushings;
* Six links--represent the attachment of the mount to the electric motor by two bolts:  
* Two rotational links (_Rotate_ type);
* Four sliding links (_Slide_ type). Figure 5: Bushings for the silentblocks of the semi-finished front mount (**1**,**2**) and rear mount (**3**). For the rear mount, the _Load Cases_ include (Figure 6b):  
* One force (_Remote Force_ type)--reaction from the silentblock acting on the rear arm bushing;
* Nine links--representing the attachment of the mount to the electric motor by means of three bolts:  
Three rotational links (_Rotate_ type);  
Six sliding links (_Slide_ type).