## 4 Results  
### \"Bending\" Mode  
The strength analysis is performed according to several criteria, the main feature of which is the assessment of the stress amount. According to the stress map, the maximum value was 381.13 MPa (marked as Max in Figure 11), which exceeds the yield strength of the material 1.4003, the yield tensile strength = 320 MPa (Table 1). The maximum stress area (Figure 11) corresponds to the location of the cross-beam between the two rear axes, on which two of the eight supports for the compactor rest (marked orange in Figure 12). Let us analyze the stress-strain state of the rods from the central part of the frame (between the cabin and the central axis). The maximum value was 131 MPa and was recorded in the slope of the floor base (Max in Figure 12). The rest of the beams are characterized by stresses in the range of 70-80 MPa. That is, if additional loading in this area with other masses is not planned, then the safety margin can be considered sufficient. The front (cabin) load-bearing part received a stress of no higher than 179 MPa (observed in the left spar), which is absolutely normal from the point of view of the margin at the yield point (Max in Figure 13):  
Figure 10: Mass distribution along the frame. The uniform strength of the frame can be estimated using the safety factor, which is physically equal to the ratio of the yield strength of the material to the actual stress value in this area of the frame. A value of 1 means that the actual stresses are equal to the yield strength; a value less than 1 means that the strength is insufficient; values greater than 1 mean that the safety margin has been exceeded (Figure 14). Figure 11: Maximum stress before optimization. Figure 12: Maximum stress in the center frame part. Figure 13: Maximum stress in the cabin frame part. After receiving the first calculation results, a huge set of measures was taken to modify the structure of the frame (selection of alternative cross-sections, change the wall thickness, introduction of additional links, etc. ); more than 50 changes in the structure of the frame were applied. Some of them are shown below (Figure 15), the application of which finally improved the total uniform strength and spread of the stress concentrators. By the way, not all the steps focused on strengthening the elements; practice has shown that it is often necessary to weaken certain elements. For example, here are a few steps that were taken (Figure 15): (a) the configuration of the roof dome with the same cross-section was changed (40 \(\times\) 40 \(\times\) 2); (b) channels 80 \(\times\) 40 \(\times\) 4 were added; (c) 3 mm thick stiffeners (scarves) were added in the front suspension mounting brackets; (d) the thickness of the sheets on the reverse side was reduced to 6 mm; (e) the thickness of the suspension brackets was increased to 8 mm; and (f) the thickness of the sheets in the rear axle suspension mounting bracket was increased to 8 mm. Figure 14: Safety factor map: (**a**) front part; (**b**) rear part. Figure 15: Cont. As a result of the optimization measures to improve the uniform strength of the frame, we achieved a reduction in the maximum stress level to 270.5 MPa (marked as Max in Figure 16), which is completely normal compared with the yield tensile strength = 320 MPa (marked as Max in Figure 16). The results are shown in Figure 17.  
Figure 15: Garbage truck frame structural modifications (aka optimization steps): **(a)** roof dome; **(b)** channels; **(c)** front suspension mounting brackets; **(d)** sheets on the reverse side; **(e)** suspension brackets; and **(f)** rear axle suspension mounting bracket. (Table 1). This value is found in regard to the load-bearing crossbar in the central axle wheel attachment of the garbage truck. In general, the central axle is always the most loaded axle and at the same time the driving one, this is typical for all trucks, one can say, without exception.