Effects of Fine Particle Peening on Fatigue Strength of Transformation-Induced Plasticity (TRIP)-Aided Martensitic Steel

2015 ◽  
Vol 665 ◽  
pp. 85-88 ◽  
Author(s):  
Koh Ichi Sugimoto ◽  
Yuta Mizuno ◽  
Tomohiko Hojo
Keyword(s):  
Fine Particle ◽  
Retained Austenite ◽  
Martensitic Steel ◽  
Crack Propagation Rate ◽  
Threshold Value ◽  
Propagation Rate ◽  
High Threshold ◽  
Fatigue Crack Propagation Rate ◽  
Stress Intensity Range ◽  
Transformation Induced Plasticity

The effects of fine particle peening on the torsional strength of a transformation-inducedplasticity (TRIP)-aided martensitic (TM) steel were investigated for applications to precision gears. Fine particle peening increased the fatigue limits and lowered the notch-sensitivities of steel, compared with quenched and subsequently tempered SNCM420 steel. In addition, fine particle peening lowered the fatigue crack propagation rate in TM steel with a high threshold value of the stress intensity range. These results were associated with (1) higher Vickers hardness, (2) higher compressive residual stress, and (3) a larger amount of untransformed retained austenite in the surface layer when compared with SNCM420 steel.

Influence of Different Crack Propagation Rate Descriptions on the Residual Fatigue Lifetime of Railway Axles

2014 ◽  
Vol 627 ◽  
pp. 469-472 ◽  
Author(s):  
Pavel Pokorný ◽  
Luboš Náhlík ◽  
Pavel Hutař
Keyword(s):  
Crack Propagation ◽  
Crack Propagation Rate ◽  
Threshold Value ◽  
Propagation Rate ◽  
Accurate Estimation ◽  
Fatigue Crack Propagation Rate ◽  
Lifetime Estimation ◽  
Fatigue Lifetime ◽  
Railway Axle ◽  
Residual Fatigue

The paper deals with an estimation of the residual fatigue lifetime of the railway axles. The railway axles can include some cracks either from manufacturing process or from previous loading operation. Because of cyclic loading of the railway axles there is a risk of fatigue failure of the railway axles with unacceptable consequences. Based on this fact, for conservative establishment of the residual fatigue lifetime of the railway axle is necessary to consider an existing crack in the railway axle during design process. The fatigue lifetime estimation of railway axles is very sensitive to used crack propagation rate description (e.g.v-Kcurve). Typical bending of this curve (knee) can be found in the vicinity of the threshold value in fatigue crack propagation rate dependence (typicallyv-Kcurve expressed in log-log coordinates). For accurate estimation of residual fatigue lifetime of the railway axle is necessary to use approximation ofv-Kcurve that takes into account existence of the knee close to the threshold value of the stress intensity factor. The paper shows important differences between different crack propagation rate descriptions on the residual fatigue lifetime estimation of the railway axles. Results obtained can be used for safer design and operation of the railway axles.

A Damage Accumulation Model for Fatigue Crack Propagation

1981 ◽  
Vol 103 (4) ◽  
pp. 293-297 ◽  
Author(s):  
C. Ihara ◽  
A. Igarashi
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Fatigue Crack Propagation Rate ◽  
Stress Intensity Range ◽  
Dimensional Version ◽  
Damage Accumulation Model ◽  
Dislocation Multiplication

The fatigue crack propagation rate is investigated on the basis of a dislocation multiplication model which was used previously in evaluation of the fatigue life up to crack initiation. The expression for fatigue crack propagation rate is derived from a two-dimensional version of a stochastic model proposed by Tsurui and one of the authors (A.I.), and a distribution function of the life of material elements in this expression is calculated on the dislocation multiplication model. On these theoretical bases, it is shown that the fatigue crack propagation rate is proportional to some power of the stress intensity range. Our results are compared with the experimental data.

Test Stand for Analysis of Fatigue Crack Propagation under Bending with Torsion

2008 ◽  
Vol 144 ◽  
pp. 90-93 ◽  
Author(s):  
Grzegorz Gasiak ◽  
Grzegorz Robak
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Digital Camera ◽  
Crack Propagation Rate ◽  
Propagation Rate ◽  
Test Stand ◽  
Crack Development ◽  
Fatigue Crack Propagation Rate ◽  
Fatigue Crack Development

The paper presents a test stand for measurements of fatigue crack propagation. The stand includes a fatigue machine MZGS–100 and a device for registration of the crack length. The test stand is equipped with a stereoscopic microscope with fluent magnification of 7× – 67.5×. The microscope can be applied for observation of fatigue crack development. The microscope is also equipped with a digital camera, which enables continuous observation of fatigue crack development on the computer monitor and it is not necessary to stop the machine. The test results obtained at this stand can be used for determination of fatigue life and fatigue crack propagation rate.

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