Effect of Loading Sequence on Short Crack Propagation Behavior of LZ50 Axle Steel

doi:10.3901/JME.2025.12.118

Abstract

Abstract: Taking LZ50 steel for railway vehicle axle as the object, the fatigue replica tests of rotating bending specimens under different loading sequences were carried out. The results show that the overall law of short crack initiation and propagation is basically the same under the two loading sequences of high low and low high, that is, the cracks all originate at the ferrite grain boundary, and there are two obvious rate decreases in the process of crack propagation; In the stage of micro short crack (MSC), the microstructure size barrier plays a leading role in the crack growth rate; In the stage of physical short crack (PSC), the influence of microstructure obstacle decreases gradually. The crack growth rate is mainly affected by the load amplitude. The growth rate increases continuously and rapidly with the increase of load amplitude until the specimen breaks. Under the rotating bending load, the fracture surfaces show multiple fatigue crack sources, but there are great differences in the morphology of the propagation zone and the location of the instantaneous fracture zone：the spacing of fatigue bands in the propagation zone is narrower and the number of dimples in the instantaneous fracture zone is more in the high-low loading sequence than in the low-high loading sample. The short crack growth rate model is modified. The modified model has a good fitting effect on the test results under different loading sequences, and can reflect the influence of microstructure and loading sequence on the short crack fatigue behavior.

Key words: LZ50 axle steel, short crack, loading sequence, growth rate

CLC Number:

U279

YANG Bing, HUANG Mian, ZHOU Minhao, XIAO Shoune, YANG Guangwu, ZHU Tao. Effect of Loading Sequence on Short Crack Propagation Behavior of LZ50 Axle Steel[J]. Journal of Mechanical Engineering, 2025, 61(12): 118-126.

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