Abstract :
Resonance phenomena in mechanical elements can cause partial or total failure to the system. this phenomena is related to the coincidence of natual and forced frequencies in mechanical parts and the system. If these frequencies stay within the same range, they all cause the system to break in a definite period of time. as an example, consider a bridge cotnaining certain natural feequency, it may also be encountered with external forces due to the wind in which forced frequencies will be created, and there fore the collapse of the bridge because of coincidence of above frequencies. as another example, consider aerodynamic forces exerted upon the aircraft wings (each wing has certain natural frequency) during the flight. crated forced frequencies by the air is then coincided with natural frequency of the wing results a great vibration and consequently the break down of the aircraft... prefae:...methods for finding natural frequeny,natural frequencied in wings and rotor wings,appendix...
