Design And Implementation Of Fatigue Ilfe Online Monitoring System Under Multiaxial Variable Amplitude Loading

This paper designed and implemented online fatigue life monitoring systemusing variable amplitude multiaxial fatigue life prediction theories under multiaxialvariable amplitude loading. Based on the thought of modern structural healthmonitoring, this system was completed by combining data acquisition system, PCmachines and software system. The function of this system included strain dataacquisition, network signaling, fatigue life prediction and abnormal fatigue lifewarning. This system can conduct remote monitor on key components of operatingequipments, help to improve the safety of the equipments, instruct reasonablemaintenance and management, and extend the service life of old equipments.Therefore, the system has great application value and economic benefits.Firstly, variable amplitude multiaxial fatigue life prediction theories were deeplyreviewed in this paper. Currently, under multiaxial variable amplitude loading, fatiguelife prediction usually has three steps, including multiaxial cycle count, multiaxialfatigue damage calculation and multiaxial fatigue damage accumulation. In the paper,Wang-Brown method, Bao method and Chen method were used to realize multiaxialcycle count. Shang model was used to realize calculation of fatigue damage andMiner’s theory was used to realize accumulation of fatigue damage. These methodswere compiled to Fortran DLL which can be called by other computer languages.Secondly, this paper chose hardware equipment suitable for strain signalacquisition to build strain signals online monitoring system. And then, by usingmultithreading technology, mixing programming technology, and object-orientedvisualization programming language C#, the variable amplitude multiaxial fatigue lifeonline monitoring system was developed. The system has the functions of usermanagement, data management, waveform display, fatigue life monitoring andabnormal fatigue life warning, etc.Finally, a testing environment was built using MTS858fatigue test equipments.The online fatigue life monitoring system developed was tested under multiaxialvariable amplitude loading. The results showed that the system can realizecorresponding functions and achieve the predetermined goal.