**4.3 Strength calculation of GP design**

256 Advanced Topics in Measurements

The team rates each concept against pre specified selection criteria, which may be weighted. The concept selection method is built around the use of decision matrices for evaluating each concept with respect to a set of selection criteria. At the same time such formalized methods are elaborated as method of imprecision (Zimmermann, 2001) with noncompensating aggregation and compensating aggregation as well as fuzzy design method

The GP styles of different cars significantly differ and should be evaluated in context of the specific vehicle. At the same time style determines an arrangement of particular components (distances between gage axes etc.). In Fig. 14 we can see initial styles and the 3D model of

Fig. 14. Frontal view of GP of the initial styles and 3D geometrical model of GP.

First let us briefly discuss obtaining responses of GP for each particular objective.

Now we can try to use the previously discussed approach for multiobjective shape

min ( ) [ ( ), ( ),..., ( )] 1 2

*T <sup>k</sup> <sup>x</sup> Fx F x F x F x* (8)

with different level interval algorithms.

**4.2 Vehicle GP optimization problem** 

optimization of the GP. The problem is stated as follows:

where *k* is the number of objective functions *Fi*; *m* is the number of inequality constraints; *e* is the number of equality constraints; *<sup>n</sup> x E* is a vector of *n* design variables.

subject to *gj(x*) ≤ 0, *j* = 1, 2,…, *m*, and *hl(x)* = 0, *l* = 1, 2, …, *e*;

the GP designed for new vehicles (Company Amoplant, 2011).

Generally the strength of the GP design is checked on special vibrostands. The GP is subjected to different dynamic loads. Vibrostability and vibration strength of the GP are checked on excitations in the frequency domain from 10 to 250 Hz. One of the main natural experiments is a test of shock resistance of the GP design under acceleration level *a* = 10*g*. Such experiments require significant material and time expenses and for optimization purposes the computer based design check must be used. The 3D geometrical model (Fig. 14) of the GP is created using SW and it consists of 18 parts: 6 deformable bodies and 12 rigid bodies that take into account the inertial characteristics of the internal devices. The deformable parts are made from the ABC 2020 plastic, but for the internal device bodies are assumed as alloy steel. The initial volume of the GP assembly is *v*0 = 764674 cm³ and mass *m*0 = 1.02 kg. The 3D model of the GP assembly is used for FEM analysis by SW Simulation to evaluate different responses of the GP. The FE mesh (Fig. 15) is generated with curvature based mesh (max elements size = 9 mm, min element size = 1.8 mm, element size growth ratio = 1.5), that ensures accurate discretization of the complex shape bodies of the GP. The FE mesh consists of ~ 210,000 nodes, ~147,000 elements, ~640,000 DOF.

In the initial design of the GP von Mises stresses from impact loading are shown on Fig. 15. We can see that maximal stresses are concentrated on the bracket's cross-section and it reaches 4 MPa. Other parts of the GP design are stressed considerably less. This implies that the bracket design should be improved.

Fig. 15. Meshed 3D model and von Mises stresses distribution in initial design of GP.
