抄録
In any manned vehicle, safety during an exterior impact event is of the highest concern. Protecting the human from the gross shock loads through the use of airbags, seats and restraints is one area of protection. Injury from flying objects within the compartment is another issue. Bolted on components have many modes of failure, none more dangerous than fracture due to a high velocity impact condition. The danger arises from the residual energy transferred to the detached mass, referred to as a secondary projectile, in the form of kinetic energy. These loose dynamic component masses can cause serious injury to humans. This paper specifically deals with the effects of bolted on components within the crew compartment of a vehicle. By varying the velocity of the impactor and the mass of the attached mass, an energy transfer efficiency can be developed. Impacts are assumed to occur directly at the bolt location. The study will hold constant the bolt as an M12 diameter Class 12.9, tapped into a 25mm thick 100mm X 100mm Aluminum plate, and a 131g steel impactor mass. Also, the head of the bolt is assumed to be on the interior surface. The range of attached masses will be limited by the ability of the M12 bolt to carry the highest mass at a static 20G load with a factor of safety of 2.0. The impacting speeds may be in the range of ballistic or explosively induced speeds, as opposed to vehicle crash impact speeds, which will be part of this evaluation. Because of this, the application may be for military applications. The actual failure mode is more a function of shock wave reflection, instead of pure shear or bending forces, so failure is not directly proportional to energy. For this reason, a small mass impactor at high velocity with the same energy as a larger mass a lower velocity, will produce higher probability of bolt fracture. Also, exterior surfaces are most likely to be critical for this mode of failure. The desired result of the study is to determine critical conditions for human safety and possible methods of capturing the loose masses. Current methods of capturing these loose projectiles include a covering blanket to catch the component. With a better understanding of the component energy, we should be able to minimize the safety capturing solution and save weight.
