| China Railway is gradually towards the rail transport direction of bus speed andtrucks overloaded, aluminum has a good overall performance: low density, highstrength, good corrosion resistance and has been widely applied in the train field, as amain material which used for the realization of high-speed and light-weight.The advancement of technology in aluminum alloy welded aluminum alloyresults in the ever-increasing range of applications in the rolling stock, many parts ofthe connections are completed by welding. Through statistics, many structures ofrailway axle and wheel-rail failure has been sustained over107weekly cyclic loading.Therefore, fatigue characteristics in the super long life range of the welded joint hasgreat significance on longer and more secure applications in the rolling stock structureof aluminum alloy.Self-developed TJU-HJ-I ultrasonic fatigue test device is used to test the fatigueperformance of5A06aluminum alloy base metal, flush welded joint and sheet buttjoint specimen in the super long life range, to explore whether aluminum existsfatigue limit or not. The fatigue S-N curve of base metal, flush welded joint and sheetbutt joint sample will be measured and compared, and the corresponding fatiguestrength and comparative analysis under N=1×10~7and N=1×10~9number of cyclesare obtained. The reduction of fatigue strength of welded joints to the base material iscompared.The fatigue fracture morphology is scaned and analyzed to explore fracturemechanism; the differences of morphology characteristics between the base metalfatigue fracture and welded joints fatigue fracture are compared. Ultrasonic fatiguetests are carried out under different stress levels, the kind of fatigue crack defects areclassified, the impact of different defects is studied respectively; conventional fatiguetesting machine is used to carry out welded joint fatigue test, the S-N curves aremeasured under conditions of the very high cycle frequency and conventionalfrequency, then the impact of the frequency on aluminum welded joints is studied. |
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