Research On Non-Stationary And Non-Gaussian Random Vibration Fatigue Accelerated Test Technology

Complex random vibration environment widely exists in the transportation and service process of all kinds of equipment,which has an important impact on the structural reliability of equipment.In practical engineering,the actual service dynamic environment of structure often presents obvious non-stationary and non-Gaussian random vibration.If the fatigue life is calculated based on the assumption of stationary Gaussian random vibration,it will often bring obvious errors and hidden dangers to service safety.In addition,with the continuous improvement of structural life and reliability,how to complete structural life prediction and reliability evaluation in a short time has become one of the urgent practical problems to be solved.This paper focuses on the research of structural vibration fatigue accelerated test technology under non-stationary and nonGaussian random vibration excitation.The main contents are as follows:1.Taking the single-degree-of-freedom system as the object,the factors affecting the structural fatigue damage are explored.Firstly,the effects of stationary Gaussian,stationary non-Gaussian and non-stationary non-Gaussian random excitations on structural fatigue damage are studied.Then,the effects of kurtosis and non-stationary index of non-stationary non-Gaussian random excitation signal on structural fatigue damage are studied.The results show that:(1)The fatigue damage caused by nonstationary non-Gaussian random excitation is the largest,and the damage caused by stationary non-Gaussian and stationary Gaussian random excitations is almost equal;(2)The increase of non-stationary index of non-stationary non-Gaussian random excitation signal will only affect the time-domain characteristics of excitation signal,which has no direct relationship with structural fatigue damage;(3)Structural fatigue damage accumulation will not strictly increase with the increase of the kurtosis of the nonstationary non-Gaussian random excitation signal,but will strictly increase with the increase of the kurtosis of the structural response.The kurtosis of the structural response is closely related to structural fatigue damage accumulation,showing an obvious positive correlation.2.The frequency decomposition of non-stationary non-Gaussian random excitation is carried out,and the dynamic response law of the system under non-stationary nonGaussian random excitation is studied in depth.The mathematical model describing the transmission law between the kurtosis of the excitation and response is established,and the simulation and experimental verification are carried out.The results show that there is a close linear relationship between the kurtosis of the structure dynamic response and the kurtosis of the signal obtained by frequency decomposition of the excitation signal with 3.2 times the half power bandwidth at the natural frequency of the structure,and the response kurtosis of the structure can be quantitatively estimated according to this relationship.This lays the foundation for accurately predicting the vibration fatigue life of the structure under non-stationary non-Gaussian random excitation.3.Based on transfer law between the kurtosis of the excitation and structural response,a new generation method of the random vibration acceleration test signal that can control the kurtosis of the structural response is proposed.By modulating the phase of the excitation signal near the natural frequency of the structure,the signal decomposed by the excitation signal with 3.2 times the half-power bandwidth at the natural frequency of the structure obvious non-Gaussian,so that the response of the structure under this excitation presents non-Gaussian.This method controls the kurtosis of the excitation decomposition signal through the kurtosis transmission mathematical model,so that the structural response can achieve the required kurtosis,which accelerate the fatigue failure of the structural while maintaining the excitation power spectral density of the structure,and greatly improve the test efficiency.Simulation and experiments verify the effectiveness of the method.The research results of this paper have important theoretical innovation significance and great engineering application value.They can be widely used in the fields of antivibration fatigue design,fatigue damage analysis and safety assessment,life determination and life extension of major equipment and engineering structures,and provide support for ensuring their safe and reliable service.