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Heterogeneous aluminium alloys are in demand in the aviation industry, where the ability of the material to withstand fatigue loads is important. The topic of the article is the search for the most experimentally available methods of deformation effect on such materials in order to increase fatigue life. Unfortunately, previous studies were ambiguous due to the large number of factors influencing the fatigue of metal materials under the same type of mechanical load; so, we chose a dynamic load with pulse loading. It turned out that for heterogeneous 2024-T351 and D16CzATW alloys, shock–vibration loading (SVL) applied during static straining prolongs their further fatigue life at a certain magnitude of the deformation during the action of the pulse. For example, for the 2024-T351 alloy at the maximum stress of alternating load σmax = 400 MPa, the longest fatigue life should be expected at deformations εimp = 2–4%; and at the maximum stress of alternating (fatigue) loading of 440 MPa, it is at εimp = 3–5%. In comparison with the average values of fatigue life of the D16CzAT alloy in the initial state, fatigue life after processing increases at σmax = 340 MPa alloy by 11.6%, at a stress of σmax = 370 MPa, by 18.4%, at a stress of σmax = 400 MPa, by 21.2%. The positive effect of long-term exposure after treatment on fatigue life was also noted. The influence of the strengthening phases, such as the nanosize Θ-Al2Cu and S-CuAl2Mg particles, on the separate stages of pre-treatment of alloys and the effects of their quantities on total fatigue durability, is investigated by statistical methods of transmission electron microscopy. Great attention is paid to the mechanism of formation of fatigue fracture embryos in the near-surface areas of the samples, for which analytical calculations and the experimental method of ultrasonic impact treatment (UIT) are used. It is shown that the use of UIT after SVL does not affect the fatigue life of the 2024-T351 alloy at a fatigue load frequency of 15 Hz, while the single UIT increases the fatigue life of the alloy. It is concluded that the use of complex deformation loads accelerates the relaxation processes, which shorten fatigue life.

It is known that many researchers of the mechanical properties of layered composites claim that in comparison with traditional structural metals and alloys, composites have serious advantages, mainly associated with high specific characteristics of static and fatigue strength. It should be noted that a well-founded idea of the advantages of composites strength characteristics is of particular importance for the elements of aircraft structures, taking into consideration an extremely important issue of operation safety. Unfortunately, at least, such a reasonable conception with respect to fatigue resistance characteristics has not been formed yet, consequently, a number of points concerning application of laminated composites in aircraft structures remain unanswered. The article presents a method and an example of comparing the fatigue life of the specimens with the open hole made of modern aluminum aviation alloy 1163T7 and carbon laminate AS4-PW. An obvious advantage of fatigue life of carbon composite materials compared to aluminum alloy at room temperature is noted. On the basis of a number of significant factors to be considered, the specified advantage can be largely diminished. First of all, these factors include the following: effect of temperature and humidity and degradation of the resistance characteristics of layered composites after impact damage. Taking into account the effect of the listed factors, the results of the comparison for the fatigue resistance characteristics of the specimens under consideration are presented. It is noted that the mentioned comparison was carried out using experimental data for the specimens considered under cyclic loading with constant amplitudes as well as under irregular loading, therefore, the comparison results may be slightly different. Nevertheless, it is obvious that the similar comparison presents relevant interest and should be considered when drawing final conclusions about the advantages (or their absence) of the fatigue resistance characteristics of carbon laminates over aluminum alloys.

Copyright of Problems of Friction & Wear is the property of National Aviation University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Threaded joints are the most technological for piling up in the fields. However, violations of standard threaded joints account for 70% of all complications in pipe processing and production. These malfunctions result in significant material losses, reduced well productivity, and contamination of the wells and environmental pollution. Particularly acute is the loss of these sealed joints during exploration and development of gas and gas condensate fields. The necessary increase in volumes and intensification of hydrocarbon energy production is envisaged by the increase of drilling depth, construction of slopes and horizontal wells. Horizontal drilling and fracturing are used to produce shale gas. The efficiency and safety of the operation of oil and gas wells in complex mining and technical conditions depend on the quality and reliability of casing and pumping columns, which requires the modernization of machinery and technology for the installation of wells. The most technological for column fitting in the fisheries sector is threaded joints. However, breach of standard threaded connections causes 70% of all complications with pump housings and columns. This leads to significant material losses, reduced production of raw materials, contamination of the interior and the environment. Therefore, the urgent task is to improve the threaded joints by increasing their reliability and efficiency under heavy workloads.

Investigating the behavior of asphalt concrete at low loading frequency is essential to understand the thermal fatigue damage due to cyclic day-night temperature cycles, where the loading frequency is usually very low. This study determines some properties (e.g., fatigue damage, dissipated energy, and stiffness) of asphalt concrete beam samples at a low frequency of loading using four-point bending test apparatus. Results show that fatigue damage is more significant at a lower frequency of cyclic loading and the number of cycles at failure becomes stable at a frequency equal to or lower than 0.01 Hz. The concept of initial stiffness at the 50th cycle of loading is inappropriate at a low frequency of loading as the stiffness reduction with a number of loadings is so considerable at a frequency of loading. In addition, the dissipated energy per loading cycle decreases with a decrease in loading frequency.

Methodological recommendations are presented for evaluating the fatigue life of machine load-bearing elements under the action of random processes of operational loading based on the integrated application of computer modeling technologies. The basic stages are considered for solving the problems of calculating dynamic loading, stress-strain state indicators, and evaluating the fatigue life of a mining dump truck when the machine is operating under typical operating conditions. Computational studies are implemented using a set of software tools for modeling multi-component ADAMS systems, finite element analysis ANSYS, and calculated fatigue life estimation nCODE Design Life.

The paper has analyzed influence of additives representing a group of thermoplastic elastomers and complex thermoplast-based modifiers on fatigue life of asphalt concrete. Regularities in time have been determined in the paper and close values of their physical and mechanical properties have been obtained while using various types of binders and modifiers. Statistic and laboratory investigations have made it possible to obtain theoretical parameters of the fatigue life for materials used for road dressing. The analysis has been based on statistical values of ordinary and modified asphalt concrete and asphalt concrete mixes of C- and A-type obtained during the experiments for the period from 2010 till 2016. A statistic analysis has permitted to compare a parameter Ипл (resistance index to plastic deformations) with such parameters as ny (number of elastic constraints) and Rc (threshold structural strength). 12 calculations (Nos. 1–12) have been carried out in order to realize targets of the second investigation. Calculative characteristics of asphalt concrete required for determination of reliability parameters have been estimated in the paper. A bottom layer of twoor three-coat pavement has been selected as an object of the investigation due to the fact that it is more often subjected to an impact of cyclic tensile stresses caused by a transport load. The required value for calculation of tensile stresses s at calculated temperature 0 has been accepted on the basis of executed estimations while using finite elements method and distribution of stresses has been determined along structure with 20 cm thickness due to load А2. Corresponding conclusions have been made in accordance with the obtained results.

Background. The issue of technological support of the required part’s material fatigue life by creating a mathematical model of the finishing turning process is considered. This model includes, as a target function, the maximum process productivity and the set of feed constraints and cutting speeds, permissible force and cutting power, machining precision, tool stability, surface roughness, part fatigue life, and cutting condition optimization. Objective. The aim of the paper is to provide technological support for the required part fatigue life by determining the rational cutting conditions, taking into account the properties of the processed material, and to develop appropriate methodological recommendations. Methods. The objective of the research is achieved by creating a mathematical model of the finishing turning process, determining the coefficients of the generalized materials’ characteristics of the classification group taking into account the properties of the processed material, further model optimization by the method of sliding admission and the definition of rational cutting conditions. Results. The mathematical model of the finishing turning process, which takes into account the characteristics of the processed material and the properties of the technological processable system, was created. Relative coefficients of the materials’ generalized characteristics of the structural alloyed chromium steels group are calculated. A multivariate optimization method of the developed mathematical model is proposed. Conclusions. The proposed methodological recommendation of technological support of a part’s material fatigue life based on a mathematical model of the finishing turning process, which includes the maximum process productivity and set of restrictions as the target function, which allows determining the rational cutting condition by the chosen method of nonlinear optimization.

With the goal of searching effective methods of industrial wastes recycling, filler systems for bituminous binders in road building have been proposed. For the first time in the world, the product of recycled tire rubbers, which is an active powder of discretely devulcanized type of rubber in addition to waste of sulfur produced in technological processes of oil refining, natural gas, etc., have been tested in order to improve the quality of bitumen binders. The rheological properties and fatigue life of the sulfur-bitumen binder have been investigated according to the linear amplitude sweep test (LAS) by using a Smart Pave dynamic shear rheometer (Physica MCR series, Anton Paar, Austria). A technique for preparing samples of sulfur-containing binders has been developed based on the results of photomicrographs analysis obtained by optical microscopy. It has been done to study their fatigue cracking resistance. The analysis of the influence of sulfur and elastic filler on fatigue life has showed that the rise of the quantity of cycles up to fatigue damage of binder samples by the factor of 3-5 (strain of 5% and 2.5%) is due to crumb rubber concentration. The addition of sulfur to ternary systems bitumen/sulfur/elastic filler enables saving energy resources as a result of the possibility of manufacturing sulfur-extended asphalt at lower temperatures.

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

By results of the review, the analysis and use of data of activities [1-8] substantive provisions of a method for fatigue life analysis of shear joint fasteners in metal-composit joints of aircraft structural elements are formulated and presented. It is noticed, that a main objective of working out and application of the presented method – search of the erroneous is constructive-technological decisions yielding unsatisfactory settlement and experimental results on fatigue durability of shear joints in mixed packages.

Copyright of Problems of Friction & Wear is the property of National Aviation University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background. Fatigue life of most important details of crushing equipment - wear plates - does not only depend on the operating conditions, but also on the method of their mechanic treatment. Austenitic composition of steel 110Γ13JI ensures unique properties - better resistance to wear and tendency to hardening together with high elasticity and impact hardness. This makes it difficult to treat it by cutting action (for example, cuttability for this kind of steel is 1480 MN/m², while, for example, for steel X18H10T it is only 592 MN/m²). The use of cutting tools with plates made of polycrystalline superhard materials (PSHM) based on cubic boron nitride (CBN) has become the solution to the problem of the decrease of cutting force during the treatment of high manganese steels by sintered-hard alloys from 125 to 8...10 kN. At the same time the longer life of an expensive tool needs the use of diagnostics technologies and methods of prevention of plates' fractures during the treatment of high manganese steels. Materials and/or methods. As a diagnostic method of technical state of the cutting instrument there has been used the method of vibroacoustic diagnostics with the reading of diagnostic information during the identification of resonance phenomena of the tool's vibroexcitation. Results. There has been shown for the first time that the level of resonance excitation of a tool with PSHM based on CNB plates during the treatment of high manganese steels is twice bigger than resonance excitation during the treatment of carbon steel of the same hardness. There has been stated the stability of diagnostic reaction to the change of the technical state of a cutting tool, equipped with cutting plates made of PSHM based on CNB during the treatment of details of high manganese steels within the frequency range of 1.6...1.8 kHz. The constant diagnostic characteristic of the beginning of intensive fracture of the cutting plate within the technological parameters of details treatment is the increase by 2.5...2.6 maximums of resonance values of vibration amplitude of a tool on the frequency of their characteristic vibration. Conclusion. It has become possible to diagnostically control the working capacity of the cutting tool, equipped with PSHM based on CNB plates during the mechanic treatment of details of high manganese steels as well as the creation of monitoring systems and adaptive control of the instrument's resource. [ABSTRACT FROM AUTHOR]

Background. One of the promising methods to reduce the retained stress in welded connections is a cheaper and more affordable vibration treatment. The work presents the research of the influence of vibration treatment during the welding cycle on the microstructure and mechanic properties of dissimilar welded connections. Materials and/or methods. There has been presented the procedure of experimental research with the description of the chosen welding conditions and corresponding treatment. To estimate the influence of vibration treatment on mechanic properties of dissimilar welded connections there has been carried out the butt welding of steel plates with simultaneous vibration treatment with frequencies between 0 and 200 Hz and vibration amplitude 62 micrometer. From the received dissimilar welded connections there have been prepared the standards for experiments on static tension, impact bending, fatigue life and metallographic research. Results. The experimental results have shown that vibration treatment during dissimilar types of steel welding with frequency 50...100 Hz increases mechanic properties of dissimilar welded connections: fatigue life - up to 4 times, impact hardness of the welded connections material at the temperature - 20 °C - twice, yield point - by 15...25 %. It also increases the disperse microstructure of the metal of welded connections. Conclusion. The results of the conducted research have allowed to state that the use of vibration treatment during the welding cycle results in improvement of mechanic properties and decrease of retained stress in dissimilar welded connections. Moreover, vibration treatment is most efficient at the vibration close to the characteristic vibration of the system. [ABSTRACT FROM AUTHOR]