SHOCK PROTECTION WITH A NONLINEAR SPRING

Using the simplest case of a nonlinear spring with a cubic restoring f orce, we show that a hard characteristic might be advisable for struct ural elements which are able to withstand high accelerations (decelera tions), while the maximum displacement has to be made small by any mea ns. Application of a spring with a soft characteristic can result in a ppreciably lower maximum accelerations (decelerations) than in a linea r system; therefore, such application can be recommended in the case w hen the requirement for the lowest displacement possible is not very s tringent. However, if the maximum drop height Is not known with certai nty (which is typically the case) the advantages of a soft spring cann ot be utilized to a full extent, because of the possibility of a ''rig id impact''. To such a case (which occurs if the initial potential ene rgy of the element is too high and significantly exceeds the work of t he restoring force within the actual ''breaking distance''), a probabi listic approach can be effectively used to design a soft spring with a low enough probability of a rigid impact. The obtained results can be helpful when designing spring protectors for vulnerable structural el ements in portable electronics. These results can be useful for a rath er broad class of nonlinear springs, not necessarily with cubic restor ing forces.