Determination of a Load Approaches for Aircraft Impacts
As basis for the analysis and verification of building and mechanical components adequate load approaches for aircraft impacts have to be developed. Different approaches and mathematical models to derive load-time-functions for the contact force between a
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Determination of a Load Approaches for Aircraft Impacts
Abstract As basis for the analysis and verification of building and mechanical components adequate load approaches for aircraft impacts have to be developed. Different approaches and mathematical models to derive load-time-functions for the contact force between airplane and hit structure are presented. Finally the shown impact load-time functions of the different types of aircraft are compiled for comparison.
14.1
General Information
The crash of an aircraft on a target is physically an impact problem with largely non-linear processes. The kinetic energy of a projectile, determined by its mass and speed, is changed into other forms of energy during impact. For the design of a structure the contact force between the striking and hit bodies are important. In principle this is dependent on the ductility of the participating structural elements. In the case of an aircraft impact a so called soft impact takes place. This is characterized by the fact that the projectile is very ductile. The kinetic energy is largely absorbed by the striking body itself in the form of plastic deformation, such that only a fraction of the energy is introduced into the impacted body. Due to the large deformations of the projectile on impact the size of the resulting contact force is practically independent of the behaviour of the impacted structure. This allows a decoupled examination. In a first step the impact force-time function can be determined using only the characteristics of the projectile. The impacted structure can then be loaded with this load function in a dynamic analysis in a second independent step. The spatial distribution of the load over the whole impact area with respect to the time sequence is of special interest. It is necessary to establish the load functions for the aircraft models and approach scenarios discussed in the previous chapter in order to continue the analysis of the problem. The first functions were created in the early 1970s: first
G. Kessler et al., The Risks of Nuclear Energy Technology, Science Policy Reports, DOI 10.1007/978-3-642-55116-1_14, © Springer-Verlag Berlin Heidelberg 2014
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Determination of a Load Approaches for Aircraft Impacts
A320
B747
Phantom
Fig. 14.1 Comparison of the geometric dimensions in a horizontal section: Phantom–Airbus A320–Boeing 747 on impact of a convoy containment with diameter of 66 m
the load function based on the “accidental” crash of a Starfighter, then of a Phantom. As previously mentioned, the latter became a part of the RSK-Guidelines of 1981. Furthermore, the document establishes that the load can be assumed to be equally distributed over an area of 7 m2. After the attacks on September 11, 2001 the deliberate crash of a large commercial aircraft was also considered. Different conditions apply in the case of such a crash compared to the load function of a Phantom. Figures 14.1 and 14.2 clarify the geometric relationships. While the impact of a phantom can be assumed to be almost puncti
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