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The paper involves reviewing researches, which consider crystallographic aspects of fatigue damage in both metallic polycrystals and single crystals. The primary aim of this work is to substantiate the necessity and feasibility of considering both material texture in polycrystals and the crystallographic orientation of single crystals during the assessment of equivalent stresses under multiaxial loading. Additionally, the study aims to assess quantitatively the accumulated fatigue damage. The tasks undertaken include as follow: analysing contemporary research investigating cases, where surface deformation relief in metals serves as an indicator of accumulated fatigue damage, examining crystallography; studying the surface relief components, and estimating how the texture of constructional metals influences the formation of deformation relief and corresponding fatigue damage. The study provides evidence for the activation of additional slip systems during biaxial loading. It is noted that the Huber--Mises method for assessing equivalent stresses during biaxial loading does not account for anisotropy in constructional materials, such as aluminium alloys commonly used in aviation. Methodologically, the paper considers mechanical tests, light microscopy, x-ray analysis. The main result of the study is the substantiation of the need to consider metals' crystallographic anisotropy, when calculating equivalent stresses under multiaxial loading. The review of research indicates that the fatigue- damage accumulation and the evolution of surface deformation relief are related closely to the crystallographic orientation of single crystals and crystallites in textured polycrystal materials. Recognizing these crystallographic aspects is essential for thorough estimating accumulated fatigue damage. It demonstrates the necessity and feasibility of considering crystallographic aspects in the development of methods for estimating accumulated fatigue damage. The effect of both the crystallographic orientation of single crystals and the texture of polycrystalline material is pronounced under the uniaxial and biaxial loadings. [ABSTRACT FROM AUTHOR]

The results of research and testing of the technology of strengthening contact surfaces in an oil medium with the addition of fluorinated graphite of the teeth of bevel gears and rolling bearings are presented. The technology provides a significant increase in resource by slowing down the development of fatigue damage to the teeth of bevel gears and rolling bearings of the NK-14ST engine starter drive. [ABSTRACT FROM AUTHOR]

The paper considers the peculiarities of damage to welded joints of steam pipelines that have been operated for a long time (more than 280 thousand hours) under creep and fatigue conditions. It is established that the damage caused by creep and fatigue depends to a large extent on the structural and phase state of the metal of welded joints, which changes considerably during their long-term operation. With longer service life of welded joints, a ferrite-carbide mixture forms in their structure as one of the components. The presence of such a mixture contributes to acceleration of damage of welded joints. The dependence of formation of the ferritecarbide mixture on the initial structure of welded joints was established, and recommendations were given for producing an initial structure with improved quality characteristics, which is advisable for increasing their reliability and service life. [ABSTRACT FROM AUTHOR]

The article substantiates the importance and relevance of increasing problem of the performance and service life of babbitt sliding bearings (SB), which are the rotors supports of a large number of centrifugal pumps, compressors, turbines and other dynamic equipment operating at high operating parameters (speeds, loads and temperatures), as well as in conditions of corrosive, abrasive and other types of working environment's influence. The analysis of the babbitt SBs production technology and operating conditions showed that the reason for the decrease in their durability are factors that are formed both at the stage of manufacture and during operation. SB failure under normal operating conditions is a consequence of wear various types: cavitation, abrasive wear, damage due to plastic deformations, fatigue damage, etc. The antifriction layer wear resistance depends on the mode of operation and design of the bearing, the physical properties of the connection between the layer and the base, the rigidity of the shaft and the bed under the bearings. As established, the bearing anti-friction layer quality must be evaluated according to the following criteria: adhesion strength of the coating to the base, cohesive strength of the anti-friction layer, porosity, and homogeneity of the structure. As established, during the production of SBs, the formation by the method of electrospark alloying (ESA) of a copper intermediate layer, firmly bonded with steel substrate, and tin layer (formation of solid substitution solutions) and babbitt provides a stronger (by 35%) of adhesion, compared to traditional technology (steel 20 + babbitt), steel substrate with babbitt, as well as more intensive removal of heat from the friction zone. As determined, a new technology in which all operations are carried out by the ESA method can be a reserve for improving the babbitt coatings formation quality, which significantly affects the durability of the SB. As determined, in order to determine a more rational technology for applying babbitt coatings, it is necessary to develop a physically based mathematical model that relates the wear of a certain amount of babbitt to the frictional work spent on it. [ABSTRACT FROM AUTHOR]

The results of investigations of the causes for fatigue fracture of rail butt joints on two new tram tracks, made by thermit welding by two organizations are presented. Control analysis of the chemical composition and mechanical properties of the rail material; analysis of the chemical composition of the welds; macroscopic and microscopic investigations of the weld, HAZ and base metal; and hardness studies in these zones were performed. It was found that pore accumulation and isolated microcracks in the weld metal are the potential cause for cracking. Violations of the technological process of thermit welding of the tram tracks were determined, which lead to appearance of these defects. The detected defects are the result of the following factors, associated with failure to meet the standard requirements on thermit welding of tram tracks and of the system of ensuring the quality of welding operations, namely violation of welding technology and insufficient control at the respective stages of the production process. 12 Ref., 7 Fig. [ABSTRACT FROM AUTHOR]

The resistance to fatigue fracture of steel 40Kh after wear-resistant surfacing using PP-NP-25Kh5FMS flux-cored wire with a sublayer of a low-carbon plastic material formed by Sv-08A wire was investigated. The design of the deposited specimens and the procedure of their testing simulated the operating conditions of the mill rolls, for the surfacing of which PP-NP-25Kh5FMS flux-cored wire is widely used. A comprehensive procedure for evaluating the resistance of multilayer material to fatigue fracture included three stages: establishment of cyclic life of specimens after manufacturing surfacing; study of cyclic crack resistance of different metal layers; determination of fatigue life of specimens, which in the course of preliminary tests had fatigue cracks in the deposited layer after repair surfacing. It was established that the cyclic life of the specimens of carbon steel 40Kh, deposited using PP-NP-25Kh5FMS flux-cored wire with a sublayer of low-carbon steel 08kp (rimmed) exceeds the cyclic life of the specimens deposited without a sublayer, approximately by 2 times. The maximum values of SIF (140…180 MPa√m) obtained on the specimens with a multilayer surfacing with a sublayer, are 2… 3 times higher than the maximum values of SIF obtained on the specimens without a sublayer, which indicates the feasibility of using a low-carbon sublayer to increase the crack resistance of a multilayer material with wear-resistant surfacing. It was shown that performance of repair surfacing according to the scheme of removal and a subsequent surfacing of only areas of the metal with fatigue cracks of long-term operating parts does not lead to a significant increase in the cyclic life after repair. This is related to the fact that after long operation, the defect-free layer of deposited metal has a significant level of accumulated fatigue damages. Therefore, to increase the efficiency of repair surfacing, it is recommended to remove not only the metal around the detected fatigue cracks, but the entire deposited layer to the depth of detected fatigue cracks with the subsequent restoration surfacing. [ABSTRACT FROM AUTHOR]

Cyclic fatigue life of specimens surfaced by flux-cored wire PP-Np-25Kh5FMS that provides deposited metal of the type of tool semiheat-resistant steel was studied. The design of the surfaced specimens and procedure of their testing simulated the operating conditions of mill rolls, for surfacing which fl ux-cored wire PP-Np-25Kh5FMS is widely used. Cyclic fatigue life of the specimens directly after surfacing was evaluated, as well as the effectiveness of application of repair surfacing to increase the residual cyclic fatigue life of specimens, in which preliminary testing revealed fatigue cracks in the deposited wear-resistant layer. The numerical method was used to determine the stress-strain state and calculate the stress intensity factor on the front of a nonthrough-thickness crotch corner fatigue crack that propagated in a specimen of 40Kh steel with a wear-resistant deposited layer at three-point zero-to-load cyclic loading. It is shown that the maximum values of the stress intensity factor along the crack front are located at approximately 1 mm distance from the vertical side face in the deepest point of the crack front and during fracture they reach the value of 52…64 MPa√m. During investigations it was shown that application of repair surfacing to products with fatigue cracks after their long-term service does not result in a significant extension of their cyclic fatigue life after repair. This is related to the fact that after long-term service the defect-free layer of the deposited metal has a considerable level of accumulated fatigue damage. That is why performance of repair of the product region damaged by a fatigue crack, is not effective without complete removal of the deposited metal layer. Results obtained in this work will be further used as base ones during performance of comparative assessment of the impact of surfacing technique and technology, as well as surfacing materials, on the fatigue life of specimens. [ABSTRACT FROM AUTHOR]

At present time, a number of HPP power units having operated about 250,000 h. in a relatively stationary operating condition, changed to a maneuver mode. This transition caused a need in the studying damageability of their equipment according to the mechanism of fatigue and, above all, welded joints of steam pipelines of heat-resistant steels, operating under the conditions of creep. A further increase in fatigue damageability causes an increase in the requirements to the initial structure of both the welded joints being produced as well as the parts to be repaired using welding. 14 Ref., 12 Fig. [ABSTRACT FROM AUTHOR]

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Aviation construction subjected to cyclic load, in consequence of which, near stress concentrators (rivet holes), emerge and develop fatigue cracks. The development of fatigue crack reduces the residual strength of the structure and further, its destruction. This work describes the selection of the sample to assess multi-site damage. Technique drilling rivet holes. Mounting the sample on the test machine. Processing of the results of the experiment. The data for crack growth in the aviation alloy D16AT. The coefficients C and n equations Paris Law that characterize properties of the material. The dependence of the crack growth rate of the stress intensity factor (SIF). The rate of crack growth and the number of cycles until a crack of specified length. According to experimental data obtained prediction of fatigue cracks. [ABSTRACT FROM AUTHOR]