Frequency Domain Method Of The Crack Growth Life Analysis For Structure Vibration Fatigue

Vibration fatigue often occurred in the engineering structure under random loading.The vibration fatigue often accompanied by crack propagation,which affects the life of the structure.Such problems have many bad effects on the structure and even lead to catastrophic accidents sometimes.Therefore,it is very important to study the crack growth life of structures under random loading.The cracked structure is the research object in this paper.The extrapolation method in the frequency domain was deduced by it in the time domain.Both methods are used to calculate the stress intensity factor K.Taking the cracked cantilever beam as an example,the range of extrapolated points in stress extrapolation method in the time domain is discussed,which provides the basis for the life estimation.A new frequency method to estimate the life of crack growth under random loading is proposed.The dynamic response of the cracked cantilever beam was analyzed by Abaqus.The power spectral density of the stress intensity factor was derived by the extrapolation method in the frequency domain.Then the life of the structure is analyzed by considering the Paris equation and the coupling effect of dynamic response and crack propagation.Furthermore,the effects of the damping,the bandwidth of excitation and the crack location on the life of the structure are discussed.The results show that the damping and the crack location have a great influence on the life of the structure,and the bandwidth of excitation which contains the first-order natural frequency has little influence on the structure life.The Matlab program is written out to achieve the time domain simulation of the random signal.In order to verify the accuracy of the time domain simulation,the power spectrum estimation of the time domain signal is performed.The method which is in the frequency domain is used in the time domain by using the cracked cantilever beam.The results show that the frequency domain method proposed in this paper can also be applied to the life analysis of a time-domain signal.