THESIS ON FRETTING FATIGUE IN RAILWAY AXLES

THESIS ON FRETTING FATIGUE IN RAILWAY AXLES

For an analytical investigation, different initial crack lengths are compared with regard to crack growth. A new fatigue crack detection system. And the data of similar specimens play a role of bridge to connect material and material structures. The crack initiation life varied from 4. However, this concept and also the approach of critical bearing load, aim on excluding an initial crack respectively critical relative movements. The data of real axles reveal the difference between material and a special structure. However, the crack growth calculation made above has the problem of completely neglecting the phases of fretting fatigue crack nucleation and short crack growth.

The conditions of the tests are shown in table 3. Xi Lu, Ning Zhu. Hirakawa, Fundanmental investigations of fretting fatigue Part 5. According to Babbick , the oxide particles accumulate in the fitting gap and lead to a modified stress distribution, a change in dimension and position accuracy, surface pitting, the formation of grooves and cracks. Dissimilar to Continuous Wavelet Transform, Discrete Wavelet Transform DWT is more commonly used because the computational cost is lower and the signals usually comprise discrete data. Cracks were detected on the basis of the measurements exceeding the threshold values for the displacement of the center of the axle, the temperature, and the variation in the load applied.

Notch factor model In design guidelines like FKMthe dimensioning of certain distinguished shaft-hub connections is specified. Proceedings of the Institution of Mechanical Engineers. This one has been developed and assembled by the University of Applied Sciences in Hamburg.

Effect of Understress on Fretting Fatigue Crack Initiation of Press-Fitted Axle

At the small test bench the bending moment is applied by two cross forces blue hydraulic cylinders. Journal of the China Railway of Society. The results show that the strength and hardness of LZ20Mn2 axle steel drop gradually and its toughness and plasticity are increased when tempering temperature goes up. Hence, an application of a multiaxial model would provide the opportunity of identifying the moment of crack initiation, in order to perform a subsequent crack growth investigation.

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New stopping criteria for crack detection during fatigue tests of railway axles. Experiments on crack propagation and threshold at defects in press-fits of railway axles.

thesis on fretting fatigue in railway axles

This paper addresses a new methodology based on vibration measurements to establish more precise stopping criteria for crack detection during fatigue testing of railway axles. Figure 9 shows the evolution of energy in the 5.

The crack initiation life varied from 4. Vibration, Fatigue tests, Fatigue crack, Railway Engineering.

thesis on fretting fatigue in railway axles

And we have measured electromagnetic properties of the wheelsets and performed finite element analysis for wheelsets with defects. Results obtained from analytical analysis could help to make a damagetolerant design, and to optimize the safety and planning of maintenance [2]. It was concluded that, due to surface presure and the existence of stress concentration, which the wheel and axle interference fit resulted in, wear abrasion and fretting fatigue initiated fatigue crack.

Fretting fatigue is a well-known phenomenon that occurs when two contacting surfaces perform oscillating relative movement under normal load.

Analysis of Transverse Cracks Forming in a Railway Axle

Thus, the range of available approaches is presented. To account for this, critical plane approaches are used. Reznicek, Fatigue tests of railway axles, Procedia Engineering 2 — Further developments have been made by Ding et al.

As a service to our customers we are providing this early version of the manuscript. Life assessment of dovetail joints between blades and discs in aero-engines.

Stress distribution on the rotor shaft and hot spot at edge of main bearing This seems reasonable when considering that cracks from fretting fatigue will at a certain length start growing under Mode I, dominated by the principle stress, in a direction perpendicular to the contact surface.

On the prediction of high-cycle fretting fatigue strength: By the means of a rainflow counting algorithm the load time series are transferred to a cumulative frequency distribution of loads, extrapolated to 20 years of turbine operation and afterwards analytically converted into a distribution of nominal bending stresses at the bearing seat.

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Analysis of Transverse Cracks Forming in a Railway Axle

The changes in the trend values in this example began prior to those changes that were related to the harmonics of the rotation speed of the axle. In a special loading scenario however, a negative vertical wind shear will lead to a summation of both components of the bending moment.

Fatigue tests can be performed using test machines in which the axle rotates or more frequently, using Sincotec resonance test machines. Detail of the dimensions of the specimens used for the fatigue tests An experimental modal analysis was performed to determine resonant frequencies using accelerometers and a dynamometric hammer. This way, resulting cross forces in the shaft of variable magnitude can be achieved.

The reason of surface hardness changes could be due to that the microstructure of material was improved after being strengthening under low-amplitude loads below the fatigue limit. Thus, conventional stopping criteria allow the test to be performed for a high number of cycles after cracks have initiated, involving a waste of energy and time and a risk of catastrophic failure for the axle, which raises safety concerns and could lead to serious damage of the machine and its environment.

Zi, Fault diagnosis of rotating machinery based on improved wavelet package transform and SVMs ensemble, Mechanical Systems and Signal Processing 21 — Accompanying full scale and 1: Multiaxial models Multiaxial models try to take into consideration the time-variant and non-proportional nature of contact stresses.