Analytical Research On Impacting Load Of Aircraft Crashing Upon A Concrete Target

The analytical research of impact load equation is the primary aspect about planecrashing upon the containment and gradually becoming one of the most important andactive subjects. Many researchers found that because some assumptions are used and someconditions are ignored in the derivation process making an uncertain correction factorappeared in the impact load equation. The more important ignored condition is that there isa crashing region between the integral part of aircraft and concrete target during impact.But how crashing region affect the impact load equation by correction factor. Until to now,it is unclear. Therefore this paper explains the formation mechanism of crashing region，establishes the new impact model and provides the expression of crashing region length byusing stress wave theory, and correct the impact load equation with correction factor byusing the principle of momentum conservation.At first, the impact when the nose of aircraft crashing on the target will cause the loadis far greater than the plastic yield limit or buckling stress limit of the material, thereforethere will appear a double-wave spread in the aircraft. When plastic wave meet the uninstallwave which is elastic wave reach the tail and then return to the nose of aircraft, it results inthe existence of crashing region because of plastic wave unloading below the damage limit.Expression of crashing region length show that the length is related with the current speedand the remaining length of aircraft, finally this length is reduced to zero.Secondly, based on the concept of crashing area and the law of momentum, the newimpact load equation with correction factor can be got of aircraft crashing upon thefixed/unfixed target, it is show that physically correction factor can be regarded as aspecific value between the difference value of the velocity of the integral part and thevelocity of crashing region and the current impact velocity. Moreover there is a certaincorrection factor in the range through the introduction of equivalent velocity. In general, thecorrection factor is not constant but a function of time.From those analytical research we can see that the amendment with impact loadequation added correction factor is caused by the change in the amount of momentum taking into account the crashing region which is different from the traditional model duringimpact. It shows that correction factor is related with the equivalent velocity of crashingregion.