ODB test

Chapter 5

are also bending during barrier penetration, including the ones on the rhs. This appears to be due to the cross beam, which does not deform and in an attempt of transferring load between main rails pushes the whole front outwards. At this point, as the crash boxes do not perform any additional function, the crash structure is loaded and starts progressively bending inwards, keeping the acceleration low. During the same interval, a number of components in the engine bay start packing and pushing against the engine but the load on the engine support remains low. As the maximum peak of 44g is reached, the crash structure is loaded to its maximum capacity in bending and finally buckles together with its supporting section of the firewall and underbody rail. The engine support is subsequently loaded, but it does not detach from its mountings and does not impact with the firewall. At the same time, the barrier is completely punctured and the vehicle is now loading the rigid wall. In the further two acceleration spikes, the crash structures are completely ineffective , the sill and the outer underbody rails absorb the energy coming from the compact bulk of gearbox, wheel, suspension components and engine cradle, all in contact with the wall.

The sill does not deform and slowly unloads as the impact energy dissipates.

Overall, the maximum acceleration reached in the test is quite high, with a peak of 44g and another two also around the 40g mark. This behaviour was however expected due to the limited size of the vehicle and its need to absorb as much energy as possible with only a limited front crumple zone.

Figure 5.1: Toyota Yaris ODB - simulation snapshot

5.1 – Toyota Yaris

Figure 5.2: Toyota Yaris ODB - structural collapse detail

Figure 5.3: Toyota Yaris ODB - acceleration

Figure 5.4: Toyota Yaris ODB - section forces

Cabin deformation

Looking at intrusion measurements, it is evident that although the vehicle performed well in Euro NCAP, the structure allows a level of intrusion in areas which do not impact heavily the loading on the ATDs. Note that all measurements given which do not have an explicit direction are taken along the X axis.

The two main areas that show high cabin deformation levels are the firewall and the A-pillar: these drive the subsequent intrusion of the other components listed in Table5.12.

Starting from the firewall, it is evident that the extensive deformation achieved is due to the positioning of the battery and brake booster: these rigid components are placed one in front of the other and during the maximum loading against the rigid barrier they are pushed against the firewall, which fails. As a result, the cross car beam deflects in its weakest spot, the centre point, and pushes the whole dashboard in the cabin. The deformation, however, interests mainly the central part and does not diminish to a large extent the space available for body deceleration. The steering column is also moved together with the dashboard and the firewall: its movement consists in rising, moving towards the passenger side and towards the driver at the same time. This measurement, however, does not include the collapsing of the steering column, which cannot occur in this simulation due to the absence of a test dummy loading the steering wheel.

The second important area of deformation, as stated above, is the lower base part of the A-pillar. Its deformation is driven by the compact mass of components crushed between the cabin and the rigid wall and by the effect of the wheel, pushing on the sill and deforming consequently the firewall. This, in turn, leads to a partial deformation of the

5.1 – Toyota Yaris

door, which is compressed and bends outwards, as demonstrated by the readings taken on the door opening width. Furthermore, the fixture point of the cross car beam, which is located in correspondence with the mid part of the A-pillar’s base, is pushed towards the driver, dragging with itself part of the instrument cluster. The extent of this phenomenon is, however, not substantial. With regards to the passenger side, no major deformation areas are present and the intrusion levels are near zero.

Additional areas worth noting are the floor and centre tunnel. The former is affected by the behaviour of the engine cradle and hence by the engine itself: when the vehicle loads the rigid wall completely, during the final stages of the impact, the cradle is loaded and does not detach from its mountings. These are fixed both to the inner and outer floor rails and to the sill. However, the weakest and most direct point of loading is represented by the inner rail, which is only supported by the floor. This leads to the rails moving backwards and deforming the floor area around it, as shown in Figure 5.9. On the other hand, the central tunnel is affected by the firewall deformation and also by the floor deformation just highlighted, resulting in its frontmost part crumbling.

Table 5.1: Toyota Yaris ODB - intrusion measurements Direction or Intrusion

Position [mm]

Steering column

x 29

y 36

z 19.5

A pillar upper 6

lower 32

Firewall upper 118

lower 49

Door opening width - driver side upper -14

lower -17

Door opening width - passenger side upper -3

lower -1

Cross car beam - fixture point

x 8

y 14.4

z -0.1

Cross car beam - max deformation

x 37

y 17.2

z 9.5

Figure 5.5: Toyota Yaris ODB - firewall intrusion

Figure 5.6: Toyota Yaris ODB - firewall deformed region

Figure 5.7: Toyota Yaris ODB - driver door opening deformation

5.1 – Toyota Yaris

Figure 5.8: Toyota Yaris ODB - A-pillar deformation

Figure 5.9: Toyota Yaris ODB - floor and tunnel deformation