As noted before, the stiffness coefficient is basically the force at which buckling occurs. For example, a car with a frontal stiffness coefficient of 6000 lb-ft/in, has a Euler buckling load of 500 lb. However, it should be recognized that this is the force that must be applied evenly across the front of the car. Thus, when the impact across the front is not even, an average depth is determined by making depth measurements at regular intervals and averaging them, as shown in Figure 16.5.

With regard to side crush, this is usually taken to mean the average crush over the area in which impact occurred, especially the area of the vehicle crush depth measurements taken at regular intervals

Figure 16.5 Uneven frontal crush.

located between the front and rear wheel wells. This is often simply the width across the front of the impacting vehicle.

Because the elastic energy, whether it be a front, side, or rear impact, is usually only a very small component of the total energy consumed in an impact, a reasonable approximation in many instances is to assume that the energy expended in the crush of one vehicle is the same as that expended in the other.

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