Open AccessCHANGES IN FATIGUE RESISTANCE OF STRUCTURAL STEELS AT DIFFERENT LOADING SPECTRA
Author(s) -
В. В. Мыльников,
Д. И. Шетулов,
O. B. Kondrashkin,
Е. А. Чернышов,
А. И. Пронин
Publication year - 2019
Publication title -
izvestiâ vysših učebnyh zavedenij. černaâ metallurgiâ
Language(s) - Uncategorized
Resource type - Journals
SCImago Journal Rank - 0.3
H-Index - 7
eISSN - 2410-2091
pISSN - 0368-0797
DOI - 10.17073/0368-0797-2019-10-796-802
Subject(s) - materials science , tangent , fatigue limit , hardening (computing) , composite material , structural engineering , cyclic stress , softening , mathematics , geometry , layer (electronics) , engineering
Fatigue strength of widely used engineering structural steels was studied at various frequencies of loading according to the scheme of cantilever bending of the rotating cylindrical samples. Fatigue resistance index is tangent of angle of inclination of fatigue curve to axis of longevity. It is established that 40 and 45 steels belong to the group of materials in which decrease in frequency of loading leads to cyclic softening and decrease in fatigue resistance, which is numerically expressed by increasing slope of fatigue curve. Tests of the samples made of 40X steel had shown that increase in frequency of loading cycles leads to a noticeable decrease in slope of fatigue curve parameter, i.e. to an increase in fatigue resistance. Decrease in fatigue resistance parameter is associated with an increase in hardening of material of the samples (parts) surface layers which reduces fatigue damage to the surface itself. Dependence of the fatigue curve slope tangent on surface damage at changing loading cycles frequency is shown and it is stated that, regardless of frequency, damage of material surface layers increases along the slope of fatigue curve. For each of these groups mathematical relations are defined. The correlation coefficient providing degree of convergence of experimental results with the constructed fatigue curve was adopted as a criterion of cyclic behavior stability of steels. It is revealed that increase in behavior stability of 40X steel is observed with increase in cyclic deformation rate. Tests of 45 steel have shown that decrease in cyclic strength with increase in loading frequency does not affect fatigue stability of material. Increased dispersion of experimental results was observed in 40 steel at low loading frequency, despite the high values of cyclic strength at given loading frequency. On the basis of conducted experiments, dynamics of behavior of real machine parts and structures subjected to cyclic loads operating was determined in the studied loading spectrum.