Plastic strain amplitude, temperature and electrical resistance measurements can be equivalently used for the characterization of the fatigue behavior and for the calculation of the fatigue life of metals under constant amplitude loading. Temperature and electrical resistance measurements are proportional to cyclic plastic deformation and provide the opportunity to evaluate the actual fatigue state of components, even under random or service loading. According to the physically based fatigue life calculation method "PHYBAL" one load increase test and two constant amplitude tests are sufficient for the calculation of Woehler (S-N) curves in excellent accordance with those determined experimentally in conventional manner with 20 or more specimens. Load increase tests allow to estimate the endurance limit of metals with one single specimen. The stress amplitudes of the two constant amplitude tests are selected slightly above the endurance limit estimated in the load increase test and slightly below the stress amplitude, which leads to failure in the load increase test. On the basis of plastic strain amplitude, temperature or electrical resistance data measured in the load increase test and in the two constant amplitude tests at 104 cycles, the Morrow curve for constant amplitude loading can be calculated. The calculation can be also performed with any other fatigue data, e.g. at half lifetime or saturation state. The fatigue state 104 cycles was selected in particular to underline the high potential of the new fatigue life calculation method. With the number of cycles to failure of one constant amplitude test, the Woehler curve can be calculated according to a generalized Basqum equation in excellent confidence with the conventionally determined one. With a total running time of about two days per material, the "PHYBAL" method yields an enormous saving of time and costs compared to the conventional determination of fatigue data. In contrast to a calculation of a Woehler curve on the basis of only two constant amplitude tests, the new fatigue life calculation method leads to negligible scatter effects, because also information about proceeding fatigue damage caused by previous load levels are incorporated. The fatigue life calculation method "PHYBAL" was also successfully applied on aluminum, magnesium and titanium alloys under constant amplitude and random loading. A new test procedure with short constant amplitude sequences periodically inserted in any kind of random load spectra enables the fatigue assessment under random loading on the basis of cyclic deformation data. Fatigue life curves for random loading can be calculated in the same manner as dedicated above for constant amplitude loading, using fatigue data of one random load increase test and two random load tests at 104 cycles.


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    Title :

    Fatigue life calculation of railway wheels on the basis of "PHYBAL"


    Additional title:

    Lebensdauerberechnung von Eisenbahnrädern auf Basis von "PHYBAL"


    Contributors:


    Publication date :

    2010


    Size :

    9 Seiten, 7 Bilder, 2 Tabellen, 8 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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