Aviation aluminum alloy after many use were tightly closed type crack a serious threat to flight safety,with fatigue crack of 7075 aluminum alloy as test object,the use of ultrasonic vibration as vibration excitation source of vibrothermography,by adjusting the power,between welding torch and tablet pre-tightening force and incentive location,the recognition of defects of aluminum alloy plate is realized.The experimental results show that the vibration of thermal imaging technology can detect the tightly closed crack,also found that detection effect is controlled by driving power,the influence of large amplitude detection significantly effect is good.In addition,under the condition of high power,preload has a great influence on the detection effect,while under the condition of low power,preload has a small effect on the detection effect.Finally,it is found that reasonable adjustment of the preload and excitation position can make the defect imaging result clearer.