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The purpose of the issue is to study the process of heat release in metals under a symmetric loading cycle under conditions of uniaxial stress in order to assess the development of fatigue damage in the elements of metal superstructures of railroad and highway bridges. The author considered bending and axial loads of specimens with and without artificial concentrators. During the experiments, the samples were covered with matte paint, which ensured an emission coefficient of 0.95. For simultaneous fixation of thermal radiation on the upper and lower surfaces of the slots, mirrors were used. To eliminate interference from thermal radiation from surrounding objects, a fabric screen was installed between these objects and samples. As a result of experimental work, the author found that in all samples, regardless of their configuration and loading conditions, fatigue failure (the appearance of visible cracks) was preceded by a sharp increase in surface temperature at the same stress level, which the author called critical. The author during the study revealed that the magnitude of the critical stresses for the tested samples under uniaxial stress state and symmetric loading cycle does not depend on the number of concentrators, their sizes and location, but depends on the self-heating temperature and the type of deformation. Thus, the critical stress can be considered a characteristic of the material. The author also noted that at stresses greater than critical, an almost linear dependence of the temperature change on the total value of the stress increment is observed. Summarizing the noted properties of critical stresses, it can be argued that such stresses can be used to assess the development of fatigue damage when assessing the technical condition of a structure during bridge inspections.The work was performed as part of a dissertation research with the support of a grant from Russian Railways for the development of scientific and pedagogical schools.

Investigation of heat release in metals under uniaxial stress state as a parameter of fatigue damage in metal bridges