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Ultra-high molecular weight polyethylene (UHMWPE) possesses distinctive properties, but has an extremely low melt flow rate (MFR) of about zero, which makes it unsuitable for processing by standard methods for polymers. The aim of this paper was to investigate the tribological properties of two-component UHMWPE-based composites with different content of isotactic PP. The composites were fabricated by three methods: a) hot pressing of the powder mixtures; b) hot compression of granules; and c) 3D printing (FDM). It was shown that the UHMWPE-based composites obtained by extrusion compounding (hot compression of granules and 3D printing) in terms of the mechanical and tribological properties (wear resistance, the friction coefficient, Young's modulus, and yield strength) were superior to the ones manufactured by hot pressing of the powder mixtures. The most effective was the ‘UHMWPE+20% PP’ composite in terms of maintaining high tribological and mechanical properties and the necessary melt flow rate (MFR) in a wide range of loads. It was recommended as a feedstock for additive manufacturing of complex-shaped products (joint components) for friction units in orthopedics.

(1) Background: The paper addresses the effect of carbon fibers (CFs) treatment by low-temperature plasma with runaway electrons on the deformation behavior of the polyetheretherketone (PEEK)-layered composites. (2) Methods: The effect of the interlayer adhesion on the mechanical response of the composites was assessed through the tensile and three-point bending tests. In addition, computer simulations of the three-point bending were carried out with the use of the finite element analysis (FEM) with varying conditions at the “PEEK–CF layers” interface. (3) Results: DRE–plasma treatment during the optimal time of t = 15 min led to formation of a rougher surface and partial desizing of a finishing agent. The shear strength of the layered composites increased by 54%, while the tensile strength and the flexural modulus (at three-point bending) increased by 16% (up to 893 MPa) and by 10% (up to 93 GPa), respectively. (4) Conclusions: The results of the numerical experiments showed that the increase in the stiffness, on the one hand, gave rise to enlarging the flexural modulus; on the other hand, a nonlinear decrease in the strength may occur. For this reason, the intention to maximize the level of the interlayer stiffness can result in lowering the fracture toughness, for example, at manufacturing high-strength composites.

A modified Mori–Tanaka model to predict the average mechanical characteristics for dispersedly reinforced materials considering the physical nonlinearity, especially plasticity, of its constituents is proposed. A comparison of theoretical results with experimental data showed that this modification provides a sufficiently high accuracy of calculated estimates for parameters of the stress-strain state of such materials.

The paper proposes a simple two-layer model to assess the behavior of a heat-loaded thermal barrier coating–substrate system with neglect of thermally grown oxide and bond coat. The model includes solutions of boundary value problems of thermal conduction, thermoelasticity, stability, and stress-strain state after stability loss, and it also provides for coating delamination from the substrate after stability loss. It is shown that when the coating–substrate system is exposed to intense heat, the coating experiences compressive stresses which can cause a loss of its stability. When the coating losses its stability on the elastic substrate, chess-board extrusion and intrusion regions with respective tensile and compressive zones arise in the system. At a critical stress intensity, the system losses its continuity at the coating–substrate interface, and the coating delaminates from the substrate in tensile zones. The zones of delamination at the coating–substrate interface are arranged periodically.

Previously, an algorithm based on two control parameters was applied to computer aided design of materials, and here the algorithm is extended to three parameters controlling the effective physicomechanical properties of polymer matrix composites: (i) the average particle size of a polymer powder, (ii) the length of reinforcing fibers, and (iii) the level of fiber–matrix adhesion. The use of these control parameters is dictated by the possibility of their ranging in terms of degrees of influence on effective material characteristics. The algorithm with built-in experimental data is applied to design a composite with specified properties on the example of ultrahigh molecular weight polyethylene reinforced with milled or chopped glass fibers. The form of data presentation shows the whole range of the three parameters which provides the desired result.

Abstract The paper presents the results on application of Lamb waves based technique for impact damage detection and severity identification. The PZT network operates in the round-robin mode changing the actuator and sensor roles of the transducers in order to detect the response of the system in the presence of damage. The monitoring is performed via the analysis of three parameters: change of the amplitude (dA), change of the energy (dP) and cross-correlation (NCC) of the signals in baseline and damaged state. Testing of laminate CFRPs shows that the damage location is estimated with an error of 5–15 mm, while the computed Damage index is linearly dependent on the applied impact energy. For honeycomb CFRPs the NCC parameter do not provide accurate results, however, other parameters allow identification within the 5–20 mm error and reflect accurate data on the severity of the damage.

TEM and X-ray diffraction studies were carried out to examine changes in the structure, phase composition, and defect substructure in the head of a differentially hardened rail after 691.8 and 1411 million gross tons (MGT) of traffic. The rail material was examined along the central axis of the head and along the gauge corner radius at distances of 0, 2, and 10 mm from the tread surface. The redistribution of carbon atoms was quantitatively analyzed. It was shown that long-term operation of rails is accompanied by two simultaneous processes related to the evolution/degradation of the structure and phase composition of lamellar pearlite colonies, namely, cutting and cold dissolution of cementite lamellae. The first process involves the cutting of carbide particles and the subsequent dragging of their fragments, which causes changes only in their linear dimensions and morphology. The second process is the fracture of cementite lamellae in pearlite colonies due to the migration of carbon atoms from the cementite lattice to dislocations, which creates favorable conditions for a structural-phase transformation in the rail metal. The reason of this is the low average binding energy of carbon atoms with dislocations (~0.6 eV) and with iron atoms in the cementite lattice (~0.4 eV). Cementite nanoparticles were revealed in the ferrite matrix; their appearance was accompanied by dislocation glide and deformation-induced decomposition of carbon solid solution in α-iron. The curves of the change in the total yield strength versus the distance to the tread surface along different directions in the rail head were plotted. The carbon content in the structural elements of rail steel was estimated. It was found that carbon in the initial state is mainly contained in cementite particles, while in rails subjected to traffic loading it is located, along with cementite particles, at crystal structure defects (dislocations, grain boundaries, subgrains). In the surface layer of steel, carbon is also present in the crystal lattice of α-iron. The results on the redistribution of carbon atoms are interpreted using the concept of interstitial bifurcation structural states in lattice curvature zones.

The fatigue properties of neat polyimide and the “polyimide + 10 wt.% milled carbon fibers + 10 wt.% polytetrafluoroethylene” composite were investigated under various cyclic loading conditions. In contrast to most of the reported studies, constructing of hysteresis loops was performed through the strain assessment using the non-contact 2D Digital Image Correlation method. The accumulation of cyclic damage was analyzed by calculating parameters of mechanical hysteresis loops. They were: (i) the energy losses (hysteresis loop area), (ii) the dynamic modulus (proportional to the compliance/stiffness of the material) and (iii) the damping capacity (calculated through the dissipated and total mechanical energies). On average, the reduction in energy losses reached 10–18% at the onset of fracture, whereas the modulus variation did not exceed 2.5% of the nominal value. The energy losses decreased from 20 down to 18 J/m3 (10%) for the composite, whereas they reduced from 30 down to 25 J/m3 (17%) for neat PI in the low-cycle fatigue mode. For high-cycle fatigue, energy losses decreased from 10 to 9 J/m3 (10%) and from 17 to 14 J/m3 (18%) for neat PI and composite, respectively. For this reason, the changes of the energy losses due to hysteresis are of prospects for the characterization of both neat PI and the reinforced PI-based composites.

The effect of a lattice curvature on impact toughness at low temperatures is studied for the 09Mn2Si and 10Mn2VNbAl high-strength low-alloy (HSLA) steels having different compositions of doping elements. It is shown that the formation of the lattice curvature (several degrees/micrometer), in particular by helical rolling, significantly increases the low-temperature impact toughness of the HSLA steels, regardless of the alloying element compositions. This means that the observed effect could be characteristic of other HSLA steels subjected to complex thermo-mechanical treatment with the formation of the lattice curvature of a certain degree. Authors suggest that the perlite $$\rightarrow $$ bainite phase transformation develops under helical rolling at a temperature of $$\sim $$ $$850\,^\circ \hbox {C}$$ . As a result, bainite is formed in the lattice curvature zones characterized by the presence of interstitial mesoscopic structural states where random rotational deformation modes could develop. This drastically improves the low temperature impact toughness of the HSLA steels and contributes to enhance their fatigue life and wear resistance.

The cross-sectional curvature and shape (inner and outer) of a cylindrical surface formed by turning have an effect on the roughness parameter—the arithmetic mean deviation of the Ra profile. The main regularities in this influence are analyzed in this article. The authors investigated specially designed test specimens using their own method, which excludes the influence of other parameters on the roughness forming process. The diameters of the cylindrical surfaces of test specimens were selected taking into account the spindle rotation speed of the lathe. As a result, these surfaces were machined at practically the same cutting speed when performing the final processing step. The Grebbs criterion was used to evaluate the uniformity of surface roughness obtained experimentally.

The structure, mechanical and tribological properties of the PEI- and PI-based composites reinforced with Chopped Carbon Fibers (CCF) and loaded with commercially available micron-sized solid lubricant fillers of various nature (polymeric-PTFE, and crystalline-Gr and MoS2) were studied in the temperature range of 23–180 (240) °C. It was shown that tribological properties of these ternary composites were determined by the regularities of the transfer film (TF) adherence on their wear track surfaces. The patterns of TFs formation depended on the chemical structure of the polymer matrix (stiffness/flexibility) as well as the tribological test temperatures. Loading with PTFE solid lubricant particles, along with the strengthening effect of CCF, facilitated the formation and fixation of the TF on the sliding surfaces of the more compliant PEI-based composite at room temperature. In this case, a very low coefficient of friction (CoF) value of about 0.05 was observed. For the more rigid identically filled PI-based composite, the CoF value was twice as high under the same conditions. At elevated temperatures, rising both CoF levels and oscillation of their values made it difficult to retain the non-polar PTFE transfer film on the sliding surfaces of the PI-based composite. As a result, friction of the ceramic counterpart proceeded over the composite surface without any protecting TF at T ≥ 180 °C. For the sample with the more flexible PEI matrix, the PTFE-containing TF was retained on its sliding surface, providing a low WR level even under CoF rising and oscillating conditions. A similar analysis was carried out for the less efficient crystalline solid lubricant filler MoS2.

This research addresses the development of a formalized approach to dental material selection (DMS) in manufacturing removable complete dentures (RDC). Three types of commercially available polymethyl methacrylate (PMMA) grades, processed by an identical Digital Light Processing (DLP) 3D printer, were compared. In this way, a combination of mechanical, tribological, technological, microbiological, and economic factors was assessed. The material indices were calculated to compare dental materials for a set of functional parameters related to feedstock cost. However, this did not solve the problem of simultaneous consideration of all the material indices, including their significance. The developed DMS procedure employs the extended VIKOR method, based on the analysis of interval quantitative estimations, which allowed the carrying out of a fully fledged analysis of alternatives. The proposed approach has the potential to enhance the efficiency of prosthetic treatment by optimizing the DMS procedure, taking into consideration the prosthesis design and its production route.

The optimal mode for ultrasonic welding (USW) of the “PEEK–ED (PEEK)–prepreg (PEI impregnated CF fabric)–ED (PEEK)–PEEK” lap joint was determined by artificial neural network (ANN) simulation, based on the sample of the experimental data expanded with the expert data set. The experimental verification of the simulation results showed that mode 10 (t = 900 ms, P = 1.7 atm, τ = 2000 ms) ensured the high strength properties and preservation of the structural integrity of the carbon fiber fabric (CFF). Additionally, it showed that the “PEEK–CFF prepreg–PEEK” USW lap joint could be fabricated by the “multi-spot” USW method with the optimal mode 10, which can resist the load per cycle of 50 MPa (the bottom HCF level). The USW mode, determined by ANN simulation for the neat PEEK adherends, did not provide joining both particulate and laminated composite adherends with the CFF prepreg reinforcement. The USW lap joints could be formed when the USW durations (t) were significantly increased up to 1200 and 1600 ms, respectively. In this case, the elastic energy is transferred more efficiently to the welding zone through the upper adherend.

Since the inelastic strain development plays an important role in the low-cycle fatigue (LCF) of High-Performance Polymers (HPPs), the goal of the research was to study the effect of an amorphous polymer matrix type on the resistance to cyclic loading for both polyimide (PI)- and polyetherimide (PEI)-based composites, identically loaded with short carbon fibers (SCFs) of various lengths, in the LCF mode. The fracture of the PI and PEI, as well as their particulate composites loaded with SCFs at an aspect ratio (AR) of 10, occurred with a significant role played by cyclic creep processes. Unlike PEI, PI was less prone to the development of creep processes, probably because of the greater rigidity of the polymer molecules. This increased the stage duration of the accumulation of scattered damage in the PI-based composites loaded with SCFs at AR = 20 and AR = 200, causing their greater cyclic durability. In the case of SCFs 2000 µm long, the length of the SCFs was comparable to the specimen thickness, causing the formation of a spatial framework of unattached SCFs at AR = 200. The higher rigidity of the PI polymer matrix provided more effective resistance to the accumulation of scattered damage with the simultaneously higher fatigue creep resistance. Under such conditions, the adhesion factor exerted a lesser effect. As shown, the fatigue life of the composites was determined both by the chemical structure of the polymer matrix and the offset yield stresses. The essential role of the cyclic damage accumulation in both neat PI and PEI, as well as their composites reinforced with SCFs, was confirmed by the results of XRD spectra analysis. The research holds the potential to solve problems related to the fatigue life monitoring of particulate polymer composites.

(1) Background: The paper addresses the computer simulation and prediction of the service life of the base of removable complete dentures (RCDs) under typical loads caused by biting and chewing food. For this purpose, the finite element method (FEM) was used. It is assumed that various blocks of teeth, such as incisors, canines, premolars and molars, are subjected to cyclic impacts during a human life. (2) Methods: Both symmetric and asymmetric mastication (two- and one-sided loads, respectively) cases were considered. The load level was assumed to be 100 N, which corresponds to the average muscular compression force of typical human jaws. (3) Results: The FEM analysis of the stress–strain state evolution for RCDs under cyclic loads was carried out. Maps of equivalent lines were drawn for the denture base in terms of its durability. A multi-axial criterion was implemented to determine the number of cycles prior to failure by the mechanism of a normal opening mode crack. The FEM-based assessment of the service life of RCDs enabled us to establish the critical stress concentration areas, thereby allowing for further planning for the correction of an occlusal scheme or teeth inclinations. As a result, the service life of RCDs under cyclic loading can be improved. (4) Conclusions: An algorithm for designing RCDs in the case of edentulism based on the FEM simulation using commercial software as part of the procedure is proposed.

—The hardness and the tribological properties of the AK10M2N silumin subjected to irradiation by a high-energy pulsed electron beam with an energy density of 35 J/cm2 are studied. As compared to the as-cast state, the microhardness of the surface layers increases by ≈20% (up to ≈1.2 GPa), the friction coefficient decreases by a factor of ≈1.3 (down to 0.42), and the wear parameter decreases by a factor of ≈6.6 (down to 0.74 × 10–3 mm3/(N m)). These changes are shown to be caused by the dissociation of silicon and intermetallic compounds in the surface layer during irradiation by a high-energy pulsed electron beam.

The manuscript is devoted to the investigation of microstructure, static and fatigue tensile properties of commercially pure titanium grade 2 in two states with coarse grains (CG ≈ 25 µm) and ultra-fine grains (UFG ≈ 0.2 µm). During mechanical tests, the in situ monitoring was conducted by means of acoustic emission and digital image correlation. Scanning electron microscopy was employed for fracture surface observations. The results of the tensile tests show significant growth in ultimate strength and decrease of ductility due to grain-boundary strengthening. Fatigue tests revealed that the high amount of defects (grain boundaries, dislocations, etc.) in UFG suppress plastic deformation and leads to earlier crack initiation, however, at the macrocrack growth stage, these impurities are obstacles for the transgranular mechanism of fracture. The experimental data obtained allow one to get the appropriate understanding of the mechanisms responsible for the variation of mechanical properties and fracture patterns as well as to attain quantitative estimation of strain localization induced by the grain refinement.

Laminated composites based on polyetheretherketone (PEEK) and polyimide (PI) matrices were fabricated by hot compression. Reinforcing materials (unidirectional carbon-fiber (CF) tapes or carbon fabric) and their layout patterns were varied. Stress–strain diagrams after three-point flexural tests were analyzed, and both lateral faces of the fractured specimens and fractured surfaces (obtained by optical and scanning electron microscopy, respectively) were studied. It was shown that the laminated composites possessed the maximum mechanical properties (flexural elastic modulus and strength) in the case of the unidirectional CF (0°/0°) layout. These composites were also not subjected to catastrophic failure during the tests. The PEEK-based composites showed twice the flexural strength of the PI-based ones (0.4 and 0.2 GPa, respectively), while the flexural modulus was four times higher (60 and 15 GPa, correspondently). The reason was associated with different melt flowability of the used polymer matrices and varied inter- (intra)layer adhesion levels. The effect of adhesion was additionally studied by computer simulation using a developed two-dimensional FE-model. It considered initial defects between the binder and CF, as well as subsequent delamination and failure under loads. Based on the developed FE-model, the influence of defects and delamination on the strength properties of the composites was shown at different stress states, and the corresponding quantitative estimates were reported. Moreover, another model was developed to determine the three-point flexural properties of the composites reinforced with CF and carbon fabric, taking into account different fiber layouts. It was shown within this model framework that the flexural strength of the studied composites could be increased by an order of magnitude by enhancing the adhesion level (considered through the contact area between CF and the binder).

The aim of the paper was to improve the functional properties of composites based on ultra-high molecular weight polyethylene (UHMWPE) by loading with reinforcing fibers. It was achieved by designing the optimal composition for its subsequent use as a feedstock for 3D-printing of guides for roller and plate chains, conveyors, etc. As a result, it was experimentally determined that loading UHMWPE with 17% high density polyethylene grafted with VinylTriMethoxySilane (HDPE-g-VTMS) was able to bind 5% glass fillers of different aspect ratios, thereby determining the optimal mechanical and tribological properties of the composites. Further increasing the content of the glass fillers caused a deterioration in their tribological properties due to insufficient adhesion of the extrudable matrix due to the excessive filler loading. A multi-level approach was implemented to design the high-strength anti-friction ‘UHMWPE+17%HDPE-g-VTMS+12%PP’-based composites using computer-aided algorithms. This resulted in the determination of the main parameters that provided their predefined mechanical and tribological properties and enabled the assessment of the possible load-speed conditions for their operation in friction units. The uniform distribution of the fillers in the matrix, the pattern of the formed supermolecular structure and, as a consequence, the mechanical and tribological properties of the composites were achieved by optimizing the values of the main control parameters (the number of processing passes in the extruder and the aspect ratio of the glass fillers).

The aim of the paper was to investigate the helical rolling parameters (a number of passes) for the microstructural modification and the low-temperature impact toughness improvement of the 09Mn2Si High Strength Low-Alloyed (HSLA) steel. In order to achieve this purpose, work spent to crack initiation and propagation was analyzed and compared with patterns of fracture surfaces. The microstructure and impact toughness values were presented in the temperature range from +20 to –70°C. Also, the fracture mechanisms in individual regions on the fracture surfaces were discussed. In addition, a methodology for computer simulation of the process was developed and implemented within the framework of the excitable cellular automata method and its integration with the kinetic theory of fracture. Finally, a theoretical analysis of the effect of grain shapes and orientations on the strain response patterns of a certain meso-volume simulating the material after the helical rolling was carried out.

The aim of this work was to design and optimize compositions of three-component composites based on polyetheretherketone (PEEK) with enhanced tribological and mechanical properties. Initially, two-component PEEK-based composites loaded with molybdenum disulfide (MoS2) and polytetrafluoroethylene (PTFE) were investigated. It was shown that an increase in dry friction mode tribological characteristics in metal-polymer and ceramic-polymer tribological contacts was attained by loading with lubricant fluoroplastic particles. In addition, molybdenum disulfide homogenized permolecular structure and improved matrix strength properties. After that, a methodology for identifying composition of multicomponent PEEK-based composites having prescribed properties which based on a limited amount of experimental data was proposed and implemented. It was shown that wear rate of the “PEEK + 10% PTFE + 0.5% MoS2” composite decreased by 39 times when tested on the metal counterpart, and 15 times on the ceramic one compared with neat PEEK. However, in absolute terms, wear rate of the three-component composite on the metal counterpart was 1.5 times higher than on the ceramic one. A three-fold increase in wear resistance during friction on both the metal and ceramic counterparts was achieved for the “PEEK + 10% PTFE + 0.5% MoS2” three-component composite compared with the “PEEK + 10% PTFE”. Simultaneous loading with two types of fillers slightly deteriorated the polymer composite structure compared with neat PEEK. However, wear rate was many times reduced due to facilitation of transfer film formation. For this reason, there was no microabrasive wear on both metal and ceramic counterpart surfaces.

The structure and mechanical properties of the 09Mn2Si high-strength low-alloyed steel after the five-stage helical rolling (HR) were studied. It was revealed that the fine-grained structure had been formed in the surface layer ≈ 1 mm deep as a result of severe plastic strains. In the lower layers, the “lamellar” structure had been formed, which consisted of thin elongated ferrite grains oriented in the HR direction. It was shown that the five-stage HR resulted in the increase in the steel fatigue life by more than 3.5 times under cyclic tension. The highest values of the number of cycles before failure were obtained for the samples cut from the bar core. It was demonstrated that the degree of the elastic energy dissipation in the steel samples under loading directly depended on the area of the grain boundaries as well as on the grain shapes. The fine-grained structure possessed the maximum value of the average torsional energy among all the studied samples, which caused the local material structure transformation and the decrease in the elastic energy level. This improved the crack resistance under the cyclic mechanical loading. The effect of the accumulation of the rotational strain modes at the grain boundaries was discovered, which caused the local structure transformation at the boundary zones. In the fine-grained structure, the formation of grain conglomerates was observed, which increased the values of the specific modulus of the moment of force. This could be mutually compensated due to the small sizes of grains. At the same time, the coarse-grained structures were characterized by the presence of the small number of grains with a high level of the moments of forces at their boundaries. They could result in trans-crystalline cracking.

The tribomechanical properties of the wear-resistant ultrahigh molecular weight polyethylene (UHMWPE)-based composites loaded with wollastonite microfibres silanized with various coupling agents (&ldquo, KH-550&rdquo, &ldquo, Penta-1006&rdquo, and &ldquo, OTS&rdquo, ) were investigated. It was demonstrated that the mechanical properties of UHMWPE-based composites filled with various amounts of wollastonite (7&ndash, 23 wt. %) increased by 1.3 times (yield strength) and by 1.8 times (elastic modulus), while the wollastonite silanization further improved yield strength by 9&nbsp, % in some cases. It was demonstrated that the composite loaded with 23 wt. % wollastonite silanized with the &ldquo, coupling agent possessed the maximum wear resistance under &ldquo, moderate&rdquo, conditions of tribological loading. Under &ldquo, severe&rdquo, conditions, the composites containing 23 wt. % wollastonite silanized with the less efficient &ldquo, agents showed the greatest wear resistance during dry sliding friction. Wear resistance significantly depended on filler weight fraction and the load&ndash, speed mode of the tribological tests. Based on the obtained experimental data on the mechanical (including impact toughness) and tribological properties of the UHMWPE-based composites loaded with wollastonite, the optimal compositions (the filler content and the type of the coupling agent) for two load&ndash, speed modes were designed using the developed computer algorithm. The composites provided the predefined high tribomechanical properties for operation in the metal-polymer friction units compared to neat polymer.

It is believed that the structure and properties of parts fabricated by additive (i.e., non-stationary) manufacturing are slightly worse compared to hot pressing. To further proceed with improving the quality of Fused Deposition Modeling 3D-printed parts, the &lsquo, UHMWPE + 17 wt.% HDPE-g-SMA + 12 wt.% PP&rsquo, composite feedstock fabrication parameters, by the twin-screw extruder compounding and 3D printing (the Fused Deposition Modeling (FDM) process), were optimized using the Taguchi method. The optimization was carried out over the results of mechanical tests. The obtained results were interpreted in terms of (1) the uniformity of mixing of the polymer components upon compounding and (2) the homogeneity of the structure formed by the 3D printing. The values of the main factors (the processing parameters) were determined using the Taguchi method. Their application made it possible to improve the physical, mechanical, and tribological properties of the samples manufactured by the FDM method at the level of neat UHMWPE as well as the UHMWPE-based composites fabricated by compression sintering. A comparative analysis of the structure, as well as the mechanical and tribological properties of the composite obtained by the FDM method, and the hot pressing from &lsquo, optimized&rsquo, feedstock was performed. The &lsquo, composites fabricated by the optimal compounding and 3D printing parameters can be implemented for the additive manufacturing of complex shape products (including medical implants, transport, mining, and processing industries, in particular, in the Far North).

The aim of the study was to develop a design methodology for the UltraHigh Molecular Weight Polyethylene (UHMWPE)-based composites used in friction units. To achieve this, stress&ndash, strain analysis was done using computer simulation of the triboloading processes. In addition, the effects of carbon fiber size used as reinforcing fillers on formation of the subsurface layer structures at the tribological contacts as well as composite wear resistance were evaluated. A structural analysis of the friction surfaces and the subsurface layers of UHMWPE as well as the UHMWPE-based composites loaded with the carbon fibers of various (nano-, micro-, millimeter) sizes in a wide range of tribological loading conditions was performed. It was shown that, under the &ldquo, moderate&rdquo, tribological loading conditions (60 N, 0.3 m/s), the carbon nanofibers (with a loading degree up to 0.5 wt.%) were the most efficient filler. The latter acted as a solid lubricant. As a result, wear resistance increased by 2.7 times. Under the &ldquo, heavy&rdquo, test conditions (140 N, 0.5 m/s), the chopped carbon fibers with a length of 2 mm and the optimal loading degree of 10 wt.% were more efficient. The mechanism is underlined by perceiving the action of compressive and shear loads from the counterpart and protecting the tribological contact surface from intense wear. In doing so, wear resistance had doubled, and other mechanical properties had also improved. It was found that simultaneous loading of UHMWPE with Carbon Nano Fibers (CNF) as a solid lubricant and Long Carbon Fibers (LCF) as reinforcing carbon fibers, provided the prescribed mechanical and tribological properties in the entire investigated range of the &ldquo, load&ndash, sliding speed&rdquo, conditions of tribological loading.

In this study, the authors have analyzed the effect of nanosized particles of titanium carbonitride Ti-C-N and non-stoichiometric nitride TiN1–x on the structure and properties of coatings on 09Mn2Si steel formed by arc welding, utilizing MP-3 electrodes. It was shown, that adding of TiN1–x modifying powders into the weld pool effectively increased the fatigue durability and impact toughness at negative temperatures.

Tribomechanical properties of antifriction composites based on the extrudable matrix “UHMWPE + 17 wt. % HDPE-g-VTMS + 12 wt. % PP” with chopped fiberglass formed by three methods: Hot Pressing of Powders (HPP), Hot Pressing of Granules (HPG) and Fused Deposition Modeling (FDM) was studied. It has been found that a composite fabricated by the FDM method possesses the highest strength properties (elastic modulus, yield strength and tensile strength). It is shown that tribological properties (friction coefficient, volumetric wear) of composites fabricated by the three methods are close to each other that is related to impact of the reinforcing filler (fiberglass). The latter takes on compressive and shearing loads during tribo-loading and improves wear resistance of the composite. The studied multicomponent UHMWPE based composite is recommended for use as a feedstock for the manufacturing antifriction products by additive manufacturing.

The structure and mechanical properties of ductile ferrite-pearlite 09Mn2Si steel after helical rolling (HR) were studied. It has been shown that five passes of the helical rolling (with a gradual temperature decrease at each pass) resulted in a finely dispersed structure formation in the rod surface layer (up to ∼1 mm thick). This indicated the development of intensive plastic deformation there. At the same time, a lamellar structure consisting of thin elongated ferrite grains has formed in the underlying layers. The largest strain hardening was evident in the surface layer up to 3 mm thick. A yield tooth and plateau were evident on plastic flow curve. The length of the yield plateau was increased up to 2 times compared to as-received steel. This was accompanied with tensile strength increasing by 30%, while the elongation at break decreased. Data of cyclic testing have shown that fatigue life of the HR-treated samples increased by 3.8 times. The highest fatigue durability was characteristic for specimens cut out from the core of HR processed rod.

The effect of high temperature helical rolling (HR) on structure and fatigue life of 09Mn2Si pipe steel has been studied. With the use of transmission electron microscopy there was revealed that rolling gives rise to refinement of ferrite grains and cracking (fracturing) of cementite plates within the pearlite phase. The effect manifests itself to the greatest extent in the surface layer where due to the rolling the level of plastic deformation was the highest. Data of microhardness measurements confirms the gradient pattern of strain hardening over the cross section during the HR occurs while the most intensive microhardness increasing take place at the depth of up to 3 mm. According to the mechanical testing results the helical rolling of 09Mn2Si steel gives rise to increasing the level of deforming stress at the yield plateau as well as the proportionality limit with a general decrease in the relative elongation. At the same time, despite the strain hardening resulting from the helical rolling the mechanisms of plastic deformation which manifest themselves in the form of parabolic hardening with a smooth decrease in the flow stress level after neck formation are preserved in the steel. During the cyclic tension the number of cycles prior to failure increases from 2.5 to 3.8 times that depends on the location of specimens’ cutting from the rolled rod. The highest improvement in fatigue fracture resistance is registered for specimens cut out from the core of the rolled rods.

The paper is devoted to solving the problem of excluding areas of irregularities in material surface images. To solve this problem, we propose an algorithm for automatic mask construction with identifying the areas with material, areas without material, and crack areas; this combines image processing methods (pattern search, threshold flood filling, boundary search) with crack detection algorithms. It is demonstrated that this algorithm is applicable to experimental images with a large number of frames in a series.

It was shown that an increase in impact toughness of the Ti-6Al-4V alloy (including at low temperatures) was associated with two mechanisms. The first one was the suppression of the discontinuity nucleation due to the dynamic nature of the structural rearrangement provided by interstitial mesoscopic nanoscale structural states (IMNSS) under the crystal lattice curvature conditions as well as plastic distortion. The second mechanism was the ductile material extrusion in the superplastic flow mode (down to T=–70°C). This enabled to extensively deform specimens without failure (in fact, in the superplastic flow mode) upon impact bending. It was discussed that the development of deformation defect flows was realized according to the mechanism of the structural-phase transformation.

Ultrasonic impact treatment (UIT) is intended for improving surface properties of metals and alloys due to the combined structure modification. Application of electrical pulses (electropulsing—EP) combined with ultrasonic surface straining allows to increase the depth of the modified surface layer and to improve physical-mechanical properties of alloys under the treatment. A clear explanation of this effect has not been developed yet. The paper deals with modeling the process of combined mechanical-electrophysical treatment (UIT + EP) of titanium alloy composite “Ti-6Al-4V + TiC”. Ultrasonic impact treatment was modeled by applying pulsed mechanical loads with the use of a hard–alloy striker. It is shown that the complementary electric current exposure made it possible to enhance the effect of ultrasonic impact treatment. In so doing, the strain in local treated regions was enlarged. It was revealed that the application of the combined treatment made it possible to locally modify effective mechanical properties, in particular, an elastic modulus was decreased, while tensile strength and the elongation at break were enlarged.

In this study, a structural and functional analysis was conducted to investigate antifriction multicomponent polymer composites on the basis of ultrahigh-molecular polyethylene (UHMWPE) developed as feedstocks for additive manufacturing of friction parts operating under extreme conditions. The aim was to make UHMWPE extrudable by selecting appropriate polymer plasticizers. An algorithm is proposed for the development of extrudable UHMWPE-based composites with a minimum amount of experimental data available. The algorithm determines the control parameters that provide required characteristics of multicomponent polymer materials and thereby ensure the achievement of desired tribological, mechanical and processing properties. The dependence of the experimentally determined characteristics versus the control parameter values is analyzed, and corresponding response surfaces are constructed in the state space. The surfaces reveal the range of the control parameter values that ensure the achievement of specified properties. The algorithm is applied to select an optimal composition of the ternary “UHMWPE+ 17 wt% HDPE-g-SMA + 12 wt% PP” mixture, whose tribological and mechanical behavior is similar to that of unfilled UHMWPE, but the melt flow is good enough for 3D printing. A comparative study is carried out on structural, mechanical and tribological properties of the multicomponent “UHMWPE+ 17 wt%HDPE-g-SMA+ 12 wt% PP” composites fabricated by FDM printing and hot pressing. It is shown that the tribological and mechanical properties of 3D-printed extrudable UHMWPE-based composites exceed the properties of composites obtained by compression sintering, which is due to the formation of more homogeneous permolecular structure with increased crystallinity. The tribological characteristics of the 3D-printed composites are studied under various friction test conditions (P*V). The composites are proposed as suitable for friction parts operating in a wide range of speeds and loads.

It was shown that loading with carbon and glass fibers results in increasing mechanical properties of polyimide (PI) based composites. Upon annealing and subsequent treatment of the fibers with a silane-coupling agent the tensile strength of the composites increased compared to loading with the unmodified fillers. The ultimate reason was increasing degree of interphase adhesion. It was shown that loading with carbon and glass fibers increased wear resistance of the composites. When testing over a ceramic counterpart, the wearing of the composites was slightly evident. In this regard, one can recommend application of these composites to operate in friction units in ceramic-polymer tribological conjugations.

The mechanical and tribological properties of PEEK-based composites reinforced with chopped carbon fibers have been studied. It has been shown that blending in a paddle mixer with bottom horizontally blade positioning did not result in carbon fibers agglomeration (in the form of “pellets”). Use of this mixing method allowed increasing the elastic modulus (at 3-point bending) of PEEK-based carbon composites by 15–25%, while flexural strength enlarged by 27–42% as compared to gravity blending or mixing with a top vertical blade positioning. Loading the PEEK with chopped carbon fibers reduced the friction coefficient by 1.3 times, while the wear rate decreased by 3 times.

The mechanical and tribological properties of “Polyimide (PI) – PTFE” composites (loaded with various size particles and fibers) at testing against metal and ceramic counterpart have been studied. It is shown that at fine PTFE powder (fluorolite) content equal to 10 wt. % the mechanical properties of the composite are comparable with ones of neat PI due to the uniform filler distribution in the matrix. At the same time, wear resistance of the composite increases up to 100 times due to transfer film formation on a counterpart surface. The composite “PI + 10 wt. % fluorolite” is recommended for antifriction applications for metal-polymer and ceramic-polymer tribological friction units.

The main goal of this paper is to design and justify optimized compositions of thermoplastic&ndash, matrix wear-resistant composites based on polyetheretherketone (PEEK) and polyphenylene sulfide (PPS). Their mechanical and tribological properties have been specified in the form of bilateral and unilateral limits. For this purpose, a material design methodology has been developed. It has enabled to determine the optimal degrees of filling of the PEEK- and PPS-based composites with carbon microfibers and polytetrafluoroethylene particles. According to the results of tribological tests, the PEEK-based composites have been less damaged on the metal counterpart than the PPS-based samples having the same degree of filling. Most likely, this was due to more uniform permolecular structure and greater elasticity of the matrix. The described methodology is versatile and can be used to design various composites. Its implementation does not impose any limits on the specified properties of the material matrix or the reinforcing inclusions. The initial data on the operational characteristics can be obtained experimentally or numerically. The methodology enables to design the high-strength wear-resistant composites which are able to efficiently operate both in metal&ndash, polymer and ceramic&ndash, polymer friction units.

The paper deals with a problem of laser welding of zinc-coated steel (DX53D+Z and DX54D+Z) plates. Experiments were carried out with the use of steel plates 0.8; 1.0; 1.3; and 1.75 mm thick. High power 2.5-2.9 kW CO2 laser was employed. CO2 was used as the shielded gas. The optimal parameters of welding for material under study were determined. The mechanical properties of welded joints were measured through the tensile loading and microhardness measurement. Tensile performances of the specimens fabricated at different welding rate and laser beam power were compared with that of the base material.