Metal Fatigue Capability Analysis Based On Thermographic Method

The development and progress of industry accelerate lots of new materials to bring out. But to realize their fatigue property quickly is an urgent problem for using. Traditional experimental methods to determine fatigue property of materials are time-consuming, laborious and cost, so they can not meet the urgent need of development. However, infrared thermal imaging method takes intrinsic dissipation energy as an indicator, and measure energy from material with infrared camera to judge its fatigue property in experiment. This method has a virtue of non-destructive, real-time, non-contact and usually needs two or three specimen to determine material's fatigue property. So many investigators have been studying this method and receiving many achievements.The instrument of this paper is infrared thermographic method. And this method makes lock-in thermal imaging system as experiment tools, which is developed by CEDIP company and this system includes ALTAIR-LI system that is used to gather data and ALT AIR system that is used to deal with data. Investigators use this method to judge the crack genesis and determine fatigue parameters of specimen from the difference of surface temperature distribution on specimen, which is induced by change of dissipation energy in materials. First of all, investigators measure fatigue parameters of Q235 and the change of surface temperature of specimens of pre-fatigue. And then non-destructive tests (NDT) on several plates with blind hole, which are loaded by the light and force. Investigators find out that the force stimulation is better than the light in active facilities about NDT, but the light do not destroy facilities. The experiment can offer reference on the behaviors of fatigue of mild steel and alloy steel.The author also uses this method to test the stress of specimens. The stress concentration factor of cross-weld in weld toe is measured by stress test function (E-MODE). And the stress concentration factor is credible compared with the results that received form calculated by theory and finite element method (ANSYS). Thermal imaging method has so many advantages:convenience, shortcut and exact, and it can reflect real load, the shape of framework in experiment. So thermal imaging method will be more spread and applied.