| Magnesium alloy’s density is the lowest in the current engineering applications of structural metallic materials, based on the advantage in property of weight and strength etc., it is provided with the great potential to be used in automobile, electron, space transport, national defense etc.. However, the application is limited due to the fatigue property. Infrared thermography is a new detection technology develops rapidly, it is provided with the advantage in noncontact, high sensitivity, high resolution, visual display etc., and it is used in the study on fatigue property of materials, study on fatigue property of magnesium alloy based on the infrared thermography has a important significance.Fatigue crack propagation of AZ31B magnesium alloy in room temperature was studied. And the temperature on the surface of ED and TD AZ31B magnesium alloy were tested by infrared thermographic technology. The mechanism of magnesium crack propagation is studied according to the relationship between the temperature of crack tip and crack length,and the relationship between temperature distribution on the surface and the trend of crack propagation in this test. The mechanism of crack propagation of two orientations of samples is compared.Results show that the temperature on the surface of the samples increased in the beginning and then decreased during the process of fatigue crack propagation, the temperature changed a little in the stabilize phase and obviously in the rapid phase. The highest temperature rise of three ED group samples is sample Al10.89℃, sample A215.19℃and sample A312.37℃, four TD group samples is sample B114.89℃,B217.47℃,B316.86℃,B415.30℃.The fatigue crack propagation rate of two orientations of samples were tested, the constant C and n of Paris formula for da/dN-△K curves of ED samples are3.66×10-8and3.67in the range of3.7<△K<5.5MPa·m1/2,1.00×10-21and22.1in the range of5.5<△K≤6.1MPa·m1/2,1.57×10-5and1.60in the range of6.1<△K≤12.0MPa·m1/2, and TD samples are9.71×10-13and5.17in the range of5.7<△K≤7.5MPa·m1/2,2.37×10-7and3.35in the range of7.5<△K≤12.6MPa·m1/2.Research shows that the maximum temperature area on the surface of samples is related to the damage mechanisms of materials. This area corresponding to the stress concentration zone, it is the site of which the fatigue micro-crack formation and expansion, the temperature change and the final section of the specimen is consistent. |
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