Keyword: «steel»

One of the little-studied problems of modern mechanics and the physics of fracture is the branching of the crack, which is observed in materials of a different nature. To experimentally determine the rate of crack branching velocity in steels, a series of tests were carried out on the fracture by internal pressure of steel thin-walled cylindrical shells (vessels) with measuring of the crack velocity by the method of breaking the conductive strips. A measurement setup was created on the basis of a precision converter “Tercon” signals of resistance thermometers and thermocouples, connected to a computer. Measurements of the crack velocity were carried out with a rectilinear crack propagation and crack branching.

The features of the stress state, physical-mechanical and structural properties of welded joints of structural steels 09G2S and St3sp, made at low climatic temperatures, are studied. Welded samples were obtained by manual arc welding using domestic electrodes UONI-13/MOROZ, HOBEKS-K-54, LB 52TRU. During the research, pulsed arc welding was tested in comparison with the traditional method of direct current welding. When welding in the cold, an increase in the level of tensile residual welding stresses by an average of 40 ... 50% is observed compared with welding at room temperature. Features of the structure and mechanical properties during welding at negative temperatures are revealed.

In this article substantiates the relevance of research into the material of the rim of a locomotive wheel, in particular, the assessment of its cold resistance by the method of determining impact strength. A calculated FE calculation of the sharpness-deformed state of the sample during impact bending testing is carried out, taking into account the sample of plastic hardening of the material. The results of the calculation show that the accumulation and deformation of along the sample notch is contribute a localization of deformation and determinate a more rigid stress-strain state of the pre-damaged material. Thus, the impact strength of a sample made of a material of construction with a long service life decreases due to a more rigid stress-strain state, which contributes to the onset of a ductile-brittle transition at a higher temperature. A method is proposed for assessing the cold resistance of using a numerical FEM calculation of a sample for impact strength, taking into account the actualized movement of the contact samples and the stand. The causes of typical errors in solving such problems are explained.