| Aluminum alloy due to of its low density,high strength,good toughness,good corrosion resistance,etc are widely used in aerospace,transportation and other important industrial fields,such as aircraft,satellites,in areas such as the railway passenger cars are the application of aluminum alloy.But the spacecraft flying back and forth every time the process is affected by the reciprocating alternating stress,such as air friction,prone to defects of the common,such as fatigue crack.If equipment defect detection is not in service in a timely manner,often can make the defect to further expand,such as crack failure occurs,will cause serious economic losses,and safety accidents,so for defect detection is very important.However,the detection technology of vibrothermography has a strong applicability to fatigue crack and a good effect on microcrack detection.Therefore,this paper mainly studies the detection of aluminum alloy fatigue crack by vibrothermography detection technology in infrared detection.In this paper,the crack of aluminum alloy is detected from three aspects:detection parameters,excitation parameters and crack parameters by means of finite element simulation and experiment.Simulation is used to explore the relationship between excitation parameters and heat generation,the relationship between detection parameters and detection effect is studied,and the relationship between crack parameters and vibration amplitude on both sides of the crack and heat generation is discussed.The main conclusions are as follows.(1)Numerical simulation shows that the vibrothermography is greatly affected by the excitation amplitude,and the heat generation at the crack is linearly positively correlated with the amplitude.The law of excitation frequency and heat generation is not obvious,but when heat generation is high,the vibration pattern is more intense.It was found that with the increase of excitation time,the generation of heat at the crack would increase,but not to a certain extent,so the excitation time around 1s was selected.(2)The experimental results show that the detection parameters have a great influence on the generation of crack heat:when the excitation power is more than 90V,the crack can be well identified.The larger the power is,the more obvious the crack is and the clearer the heat map is,the better the detection effect is.When the power is constant,the generated heat at the crack increases first and then decreases with the increase of the preload.It is observed through experiments that the preload at 40?50N has the best detection effect.When the excitation power and preload are fixed,it is found that the excitation position has a great influence on the generation of heat,the location of the excitation source is far away from the crack and the detection effect is poor,but the closer the crack is,the better the effect is.When the excitation position is changed,it is found that the side excitation effect is slightly better than the front excitation.(3)The study of crack parameters shows that:under the experimental conditions,the heat generation at the crack is positively correlated with the crack length;when the crack length is constant,the roughness of the crack surface is positively correlated with the heat generation in the crack area.Found in the vibration experiment,incentives on either side of the crack in the process of vibration will happen very big change,the speed difference of crack on both sides of the waveform have left two crack surface there is relative motion,thus making contact heating,after detection of crack surface under SEM observation,can obviously observed friction marks,and after the experiment of crackle appear black powder,energy spectrum analysis found that the main elements of 7075 aluminum alloy components,show that friction heat generating mechanism for heating. |
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