Wear Process Research Articles

Study on the performance of reciprocating seals under the coupling effect of elastohydrodynamic lubrication and rubber wear

Due to the lack of research on the sealing performance of reciprocating combined seals under the coupling of elastohydrodynamic lubrication and rubber wear, this paper uses the UMESHMOTION user subroutine and the improved Archard model to realize the dynamic wear process of the combined seals and the adaptive meshing of the local area to simulate the wear of the seals. At the same time, combined with the elastohydrodynamic lubrication model of the toothed slip ring combined seal ring, the sealing performance of the reciprocating combination under mixed lubrication conditions is studied. Finally, the accuracy of the model is verified by building a two-cylinder reciprocating seal test bench with more accurate measurement. The results show that the influence of the change of fluid pressure on the wear of the seal lip is greater in the fast wear stage than in the stable wear stage. The influence of the change of interference on the wear of the sealing lip is small at different wear stages. The wear of the sealing lip has a significant effect on the sealing performance of the instroke, but has little effect on the sealing performance of the outstroke.

Coupled evolution process of lubrication and wear in piston-liner interface of high-pressure common rail pumps

As a pivotal frictional pair of piston pumps, the piston-liner interface is vulnerable to rapid wear in the face of severe environment, triggering a consequent contraction in the piston pump's service longevity. Based on statistical theory, a transient mixed lubrication model has been established in this work, which takes the surface roughness effect, thermal-elastic deformation, as well as the piston micro-movements into account. In conjunction with the wear calculation model, we propose a novel lubrication-wear coupling strategy for the piston-liner interface, enabling a nuanced exploration of the transient interdependency link between lubrication efficiency and wear characteristics. To underscore the robustness of our proposed model, a comparison is drawn with experimental results gleaned from established literature. This investigation not only provides insights into the progression of wear depth and lubrication efficiency throughout a given time frame. but also assesses the impact of varying operational parameters on wear depth Parametric studies reveal that the wear region predominantly occurs at the inlet and outlet positions of the liner. Furthermore, both working pressure and cam rotational speed significantly influence the interface's lubrication characteristics and wear behavior. Consequently, in piston systems operating under high-pressure and high-speed conditions, it is imperative to closely monitor wear patterns and consider the impact of thermal effects.

Effect of Low-Temperature Plasma Carburization on Fretting Wear Behavior of AISI 316L Stainless Steel

AISI 316L stainless steel has received considerable attention as a common material for key ball valve components; however, its properties cannot be improved through traditional phase transformation, and fretting wears the contact interface between valve parts. A carburized layer was prepared on the surface of AISI 316L stainless steel by using double-glow low-temperature plasma carburization technology. This study reveals the effect of double-glow low-temperature plasma carburization technology on the fretting wear mechanism of AISI 316L steel under different normal loads and displacements. The fretting wear behavior and energy dissipation of the AISI 316L steel and the carburized layer were studied on an SRV-V fretting friction and wear machine with ball–plane contact. The wear mark morphology was analyzed by using scanning electron microscopy (SEM), the phase structure of the carburized layer was characterized with X-ray diffractometry (XRD), and the wear profile and wear volume were evaluated with laser confocal microscopy. The carburized layer contains a single Sc phase, a uniform and dense structure, and a metallurgically combined matrix. After plasma carburizing, the sample exhibited a maximum surface hardness of 897 ± 18 HV0.2, which is approximately four times higher than that of the matrix (273 ± 33 HV0.2). Moreover, the surface roughness was approximately doubled. The wear depth, wear rate, and frictional dissipation energy coefficient of the carburized layer were significantly reduced by up to approximately an order of magnitude compared with the matrix, while the wear resistance and fretting wear stability of the carburized layer were significantly improved. Under different load conditions, the wear mechanism of the AISI 316L steel changed from adhesive wear and abrasive wear to adhesive wear, fatigue delamination, and abrasive wear. Meanwhile, the wear mechanism of the carburized layer changed from adhesive wear to adhesive wear and fatigue delamination, accompanied by a furrowing effect. Under variable displacement conditions, both the AISI 316L steel and carburized layer mainly exhibited adhesive wear and fatigue peeling. Oxygen elements accumulated in the wear marks of the AISI 316L steel and carburized layer, indicating oxidative wear. The fretting wear properties of the AISI 316L steel and carburized layer were determined using the coupled competition between mechanical factors and thermochemical factors. Low-temperature plasma carburization technology improved the stability of the fretting wear process and changed the fretting regime of the AISI 316L steel and could be considered as anti-wearing coatings of ball valves.

Assessing brain integrity in patients with long-term and well-functioning metal-based hip implants.

Production of metal debris from implant wear and corrosion processes is now a well understood occurrence following hip arthroplasty. Evidence has shown that metal ions can enter the bloodstream and travel to distant organs including the brain, and in extreme cases, can induce sensorial and neurological diseases. Our objective was tosimultaneously analyze brain anatomy and physiology in patients with long-term and well-functioning implants. Included were subjects who had received total hip or hip resurfacing arthroplastywith an implantation time of a minimum of 7 years (n = 28) and age- and sex-matched controls (n = 32). Blood samples were obtained to measure ion concentrations of cobalt and chromium, and the Montreal Cognitive Assessment was performed. 3T MRI brain scans were completed with an MPRAGE sequence for ROI segmentation and multiecho gradient echo sequences to generate QSM and R2* maps. Mean QSM and R2* values were recorded for five deep brain and four middle and cortical brain structures on both hemispheres: pallidum, putamen, caudate, amygdala, hippocampus, anterior cingulate, inferior temporal, and cerebellum. No differences in QSM or R2* or cognition scores were found between both groups (p > 0.6654). No correlation was found between susceptibility and blood ion levels for cobalt or chromium in any region of the brain. No correlation was found between blood ion levels and cognition scores.Clinical significance: Results suggest that metal ions released by long-term and well-functioning implants do not affect brain integrity.

Analysis of the Sand Erosion Effect and Wear Mechanism of Wind Turbine Blade Coating

The wind–sand climate prevalent in the central and western regions of Inner Mongolia results in significant damage to wind turbine blade coatings due to sand erosion. This not only leads to a decline in power generation but also poses safety risks. This study replicated the wind–sand environment of Alashan and numerically simulated the erosion and wear process of the blade coatings of a 1.5 MW horizontal axis wind turbine under rotational conditions using the DPM model. Additionally, erosion tests were conducted on the operating wind rotor in a wind tunnel. The simulation results demonstrate that sand particle trajectories in the rotating domain are influenced by vortex, incoming wind speed, and sand particle size. For small-sized sand particles, variations in wind speed do not substantially alter the number of particles in contact with the wind turbine blades. However, alterations in the momentum of these particles lead to changes in the impact force on the coating surface. Conversely, the change of wind speed will not only alter the number of large-size sand particles in contact with the wind rotor but also modify the impact force on the coating surface. Furthermore, after impacting the blade, small sand particles continue to move along an approximate helical trajectory with the airflow, while large-size sand particles swiftly rebound. Through statistical analysis of erosion pits on the blade surface after the erosion experiments, it was observed that, in comparison among the leading edge, windward side, trailing edge, and leeward side, the leading edge presents the greatest number of erosion pits, whereas the leeward side has the fewest. Along the spanwise direction, the 0.7R-blade tip segment exhibits the highest count, while the blade root-0.3R section displays the fewest number of pits. The wear morphology of the blade coating was observed from the blade root to tip. The leading edge coating exhibits a range from shallow pits to coating flaking and deeper gouge pits. On the windward side, the coating displays wear patterns varying from tiny cutting pits to cutting marks, and then to gouge pits and coating flaking. Erosion morphology of the trailing edge evolves from only minor scratches to spalling pits, further deepening and enlarging. These research findings provide a basis for the study of zoning-adapted coating materials for wind turbine blades in wind–sand environments.

Self-Reinforced Piezoelectric Response of an Electroluminescent Film for the Dual-Channel Signal Monitoring of Damaged Areas.

Organic piezoelectric nanogenerators (PENGs) show promise for monitoring damage in mechanical equipment. However, weak interfacial bonding between the reinforcing phase and the fluorinated material limits the feedback signal from the damaged area. In this study, we developed a PENG film capable of real-time identification of the damage location and extent. By incorporating core-shell barium titanate (BTO@PVDF-HFP) nanoparticles, we achieved enhanced piezoelectric characteristics, flexibility, and processability. The composite film exhibited an expanded output voltage range, reaching 41.8 V with an increase in frequency, load, and damage depth. Additionally, the film demonstrated self-powered electroluminescence (EL) during the wear process, thanks to its inherent ferroelectric properties and the presence of luminescent ZnS:Cu particles. Unlike conventional PENG electroluminescent devices, the PENG film exhibited luminescence at the damage location over a wide temperature range. Our findings offer a novel approach for realizing modular and miniaturized real-time damage mapping systems in the field of safety engineering.

Exploring the influence and mechanism of hardfacing STL12 on impact wear performance at high temperature and heavy load

As one of the most important contact pairs of an engine, the performance improvement of the valve and seat insert contact pair is of great concern. In this study, commonly used industry tempered seat inserts and hardfacing seat inserts were selected (named tempered group and hardfacing group respectively). The impact wear performance test was carried out, under conditions consistent of temperature of 650 °C, load of 30 kN, frequency of 12 Hz, and stroke of 1 mm. The wear process of the wear zone was investigated using 3D scanner, optical microscope (OM), scanning electron microscope (SEM), and X-ray photo-electron spectroscopy (XPS). The wear mechanism of the wear area was analyzed according to macro profile and micro wear morphology. The results showed that after the impact test, a layer of oxide film was formed on the surface of the hardfacing seat insert, which isolated direct contact of the valve and the seat insert, greatly improving the wear performance of the pairs. In addition, the hardness of the hardfacing seat insert was higher than the tempered seat insert, this further reduced the weight loss between the contact pairs. The weight loss of hardfacing group was 0.36 g and tempered group was 1.62 g, the weight loss of hardfacing group was reduced by 77.78 % compared with that of tempered group. So in conclusion the impact wear performance of the hardfacing pair is better than the tempered pair.

Microstructure and wear behaviors of a WC10%-Ni60AA cermet coating synthesized by laser-directed energy deposition

This study successfully prepared crack-free WC10%-Ni60AA cermet coatings with high hardness using directed-energy deposition incorporating substrate preheating up to 500 °C. At the bottom of the deposit, the crack-free coating microstructure exhibited a lamination layer with a coarse herringbone eutectic, and the crystal-microstructure phase mainly comprised γ-Ni solid solution and eutectic precipitation Ni17W3, Ni31Si12, and Cr23C6. At the middle and top of the deposit, the microstructure exhibited a dense net-like eutectic, including a dendritic with the main phase of γ-Ni solid solution, interdendritic with a main phase of Cr23C6, and subdendritic with a main phase of Ni31Si12, Ni17W3, and a small block-like precipitate with a main phase of Cr2.4W0.6Si. Furthermore, the deposits on the substrate preheated to 500 °C exhibited the highest hardness (812 HV, an increase of 64 % compared to that of the non-preheating sample) owing to the dense net-like eutectic precipitation with fine-grain structure. Furthermore, wear test results show that the wearing process is divided into three stages: the rapid-increase stage; the plowing-friction stage; and the stable-wear stage. Specifically, as the load increased from 100 N to 400 N, the width and depth of the wear tracks increased, and the wear mechanisms were adhesive and oxidation, with the most severe wear occurring under a load of 400 N. Similarly, as the speed increased from 50 RPM to 300 RPM, the width and depth of the wear tracks increased, and the wear mechanisms were adhesive and oxidation at low speeds. When the speed was increased to 300 RPM, the most severe wear occurred, and the wear mechanisms were primarily adhesive and abrasive, along with a small amount of oxidation wear.

Effect of Operating Parameters on the Mulching Device Wear Behavior of a Ridging and Mulching Machine

To conduct an in-depth investigation of the impact of various operating parameters on mulching device wear during the operation of full-film dual-row ridging and mulching machine mulching, this paper employed EDEM software to create a 3D discrete element model of how a mulching device interacts with the soil on the seed bed and simulated the dynamic process of the interaction between the mulching device and the soil during the mulching operation. We analyzed the cladding wear process between the cladding device and the cladding sand particles, and two areas of impact wear on the overburden conveyor housing and areas of wear on the chute deflector scratches were detected. A three-factor, three-level Box–Behnken experimental design approach was used, with mathematical modeling of the relationship between the scraper conveyor lifting line speed, seed bed cover, scraper spacing, and wear of the cover device, finding the optimal combination of operating parameters for mulching devices. The results of the simulation test indicated that the mulching device experienced a minimum wear of 0.958 × 10−3 mm at a lifting line speed of 0.7 m·s−1 for the scraper conveyor, a mulching volume of 2.55 kg·s−1 for the seed bed, and a scraper spacing of 98 mm. The results of the field trial validation showed that, in a comparison between simulated wear parts and a mulching operation prototype of the same two wear parts, the established discrete element model appeared reasonable concerning the structural parameters, with a feasible abrasion mechanism process of sand particles on the soil-covering devices, demonstrating the model’s reliability and validity. It can serve as a guide for optimizing the design of mechanized full-film dual-furrow seed bed mulching operation.

Insights into interrupted rolling strategy as post-processing impact on dual phase tribological behaviour properties of Mg-8%Li doped bagasse nanoparticles composite

Abstract A combined effect of percentage reduction in rolling and weight percentage bagasse nanoparticles were used to improved the wear behaviour of Mg-8% Li/bagasse nanoparticle composites for the first time. The composites were produced using the double stir casting method by varying bagasse nanoparticles from 1 to 3%. The interrupted rolling process was used to reduce the samples to 50, 70, and 90%. The microstructural, hardness, and wear properties of the rolled composite were investigated. The results show that interrupted rolling lessen macrocracking and increase the rolled sample's formability. At 90% rolled reduction and 3% bagasse addition, the sample's hardness values improved to 74%. The coefficient of friction and wear resistance improved; with 90% rolled work exhibiting the highest wear resistance. Adhesion and delamination were the main wear processes in the as-cast samples; in the rolled samples, abrasion was the predominant wear mechanism. This study showed how to make Mg-8% Li-bagasse nanoparticle composites more resistant to wear by combining the effects of bagasse nanoparticles and rolling reduction.

Effect of N on the Microstructure and Wear Resistance of 4Cr13 Corrosion-Resistant Plastic Mold Steel.

The effect of N content on the microstructure and wear resistance of 4Cr13 corrosion-resistant plastic mold steel were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and tribometer. The results showed that the influence mechanism of nitrogen on the hardness of the test steels responded to the changes in the quenching temperature. When the quenching temperature was below 1050 °C, the solid solution strengthening of N played a dominant role as a wear mechanism, and as the N content increased, the hardness of the steel increased. When the quenching temperature was higher than 1050 °C, N increased the residual austenite content, resulting in a decrease in hardness. The addition of N reduced the optimal quenching temperature of the test steels. The N addition promoted the transformation of large-sized M23C6 to M23C6 and fine Cr2N, resulting in an increase in the hardness of the test steels. The influence on the wear resistance of the experimental steels differed according to the varied N contents. The addition of 0.1% N delayed the precipitation of large- sized particles in the second phase, increased the hardness of the steel, and reduced the degree of wear. However, an excessive addition of N (0.18%) led to the excessive precipitation of the second-phase particles, and the second-phase particles then gradually flaked during the wear process and continued to participate in the wear process as third-body abrasives, reducing wear resistance.

Preparation and tribological properties of novel cold–sprayed Ti–diamond composite coating

Attaining a high deposition efficiency and uniform distribution of the reinforced phase in cold-sprayed composite coatings has always been challenging. In the present study, a Ti–diamond composite powder was prepared via ball milling, followed by the deposition of a composite coating onto a Ti6Al4V substrate using cold-spraying technology. X-ray diffraction analysis confirmed that neither α-Ti nor diamond phases underwent a phase transformation during the ball milling or spraying processes. Scanning electron microscopy revealed that the irregular diamonds in the composite coating powder were uniformly coated on the surface of the spherical Ti particles, leading to a homogeneous dispersion of the diamonds within the coating. Energy-dispersive X-ray spectroscopy indicated that metallurgical and chemical bonding occurred between the diamond and Ti, and microhardness and bonding strength test results revealed that the hardness of the coating increased with the diamond content. Friction and wear analyses indicated that the wear resistance of the composite coating was better than that of a pure Ti coating, and the wear rate of the coating was the lowest when the diamond content of the coating was 10 wt%. Morphological and composition analyses of the worn surfaces of the composite coatings suggested that some of the Ti was oxidized into TiO2 during the wear process, and the diamond lost its support owing to the wear and spalling of Ti. Finally, abrasive wear occurred under the joint action of TiO2 and shed diamond.

A story of two transitions: From adhesive to abrasive wear and from ductile to brittle regime.

Atomistic simulations performed with a family of model potential with tunable hardness have proven to be a great tool for advancing the understanding of wear processes at the asperity level. They have been instrumental in finding a critical length scale, which governs the ductile to brittle transition in adhesive wear, and further helped in the understanding of the relation between tangential work and wear rate or how self-affine surfaces emerge in three-body wear. However, so far, the studies were mostly limited to adhesive wear processes where the two surfaces in contact are composed of the same material. Here, we propose to study the transition from adhesive to abrasive wear by introducing a contrast of hardness between the contacting surfaces. Two wear processes emerge: one by gradual accretion of the third body by detachment of chips from both surfaces and the other being a more erratic mixed process involving large deformation of the third body and removal of large pieces from the soft surface. The critical length scale was found to be a good predictor of the ductile to brittle transition between both processes. Furthermore, the wear coefficients and wear ratios of soft and hard surfaces were found to be consistent with experimental observations. The wear particle is composed of many concentric layers, an onion-like structure, resulting from the gradual accretion of matter from both surfaces. The distribution of sizes of these layers was studied, and it appears that the cumulative distribution of hard surface's chip sizes follows a power law.

Study on the role of chromium addition on sliding wear and corrosion resistance of high-manganese steel coating fabricated by wire arc additive manufacturing

Guide shoe made of steel is an important component of coalcutter and rail transport to sustain forward direction. However, the guide shoe suffers from wear failure due to the heavy load and fatigue. Preparing wear-resistance coating on the worn surface is a practical and economic technology to elongate longevity. High manganese steel is a candidate material with excellent wear resistance. In this study, high-manganese (HiMn) and high-manganese medium-chromium (HiMnMeCr) coatings are fabricated by using wire arc additive manufacturing (WAAM) to investigate the role of Cr addition on the microstructure and resistance to wear and corrosion by analyzing the microstructure morphology, wear rate, coefficient of friction, surface and cross-sectional morphology of the wear track, and electrochemical behavior by using sliding wear test and electrochemical experiment. The experimental results obtained by using the counterface material of ZrO2 showed that Cr addition changed the microstructure constitutes of WAAMed HiMn coating from biphasic austenite + martensite to single austenite. The addition of Cr elongated the running-in period of the wear process and weakened the wear resistance of the WAAMed HiMnMeCr coating due to the work-hardening effect induced by the severe plastic deformation of austenite. At loads of 50 and 100 N, the primary wear mechanism for the HiMn coating was a complex mode of abrasive and adhesive wear. The wear mechanism transformed into a single adhesive wear at a load of 120 N. However, the primary wear mechanism of the HiMnMeCr coatings was abrasive wear at all tested loads. The electrochemical experiment (pote ntiodynamic curves and EIS analysis) shows that the corrosion resistance of HiMnMeCr coating was better than that of HiMn coating, indicating that the addition of Cr enhanced the corrosion resistance of the WAAMed HiMn steel by the passivation effect of Cr. This study will provide a fundamental theory for the fabrication of wear-resistance coating by using WAAM.

Advanced nanoparticles in osteoarthritis treatment.

Osteoarthritis (OA) is the most prevalent degenerative joint disorder, affecting hundreds of millions of people globally. Current clinical approaches are confined to providing only symptomatic relief. Research over the past two decades has established that OA is not merely a process of wear and tear of the articular cartilage but involves abnormal remodelling of all joint tissues. Although many new mechanisms of disease have been identified in the past several decades, the efficient and sustainable delivery of drugs targeting these mechanisms in joint tissues remains a major challenge. Nanoparticles recently emerged as favoured delivery vehicles in OA treatment, offering extended drug retention, enhanced drug targeting, and improved drug stability and solubility. In this review, we consider OA as a disease affecting the entire joint and initially explore the pathophysiology of OA across multiple joint tissues, including the articular cartilage, synovium, fat pad, bone, and meniscus. We then classify nanoparticles based on their composition and structure, such as lipids, polymers, inorganic materials, peptides/proteins, and extracellular vesicles. We summarise the recent advances in their use for treatment and diagnosis of OA. Finally, we discuss the current challenges and future directions in this field. In conclusion, nanoparticle-based nanosystems are promising carriers that advance OA treatment and diagnosis.

Study of the wear process in an experimental simulation of a fuselage/runway rubbing contact

In this work, the authors tackle the problem of laboratory simulation of frictional contact in wheels-up emergency landing conditions. To design a novel tribometer simulating the contact between an aircraft structure and a runway, one must carry two complementary main tasks: the understanding of the underlying physical mechanisms and the scaling up of the in-lab results to the scale of interest. The authors propose to progress on the first task by conducting exploratory work using existing resources. Their contribution consists of a multi-scale methodology to reconstruct the wear process in a tribological system within wheels-up emergency landing conditions. This could provide guidance for safer aircraft and runway design. The study falls within the framework of three-body tribology. The proposed multi-scale characterisation methodology is made up of four steps. After describing the whole tribological system, its mechanical response is measured and analysed. This measurement is complemented by surface observations and physicochemical analyses. Finally, all the measurements and observations are discussed to come across a phenomenological wear scenario that revealed friction and wear as system responses with the key role of the third body.

Procena karakteristika obrade i habanja alata tokom bušenja ugljenika / aluminijum-aluminijum

In the past few decades, fibre metal laminate (FML) machining has been facing critical challenges in quality control and tool wear monitoring due to the material's intrinsic heterogeneity and abrasiveness. Different drill tools have been used to investigate the effect of process parameters on machining performances. Composite holes and tool wear was studied for drilling forces and surface roughness. An emphasis was made on examining the tool morphologies and wear processes that influence the drilling of CARALL composites. The drilling responses obtained from both the drill bits were optimized using a decision-making approach viz; Combined Compromise Solution Analysis (CoCoSo). The SEM investigation of the machined samples was used to examine the hole quality and surface finish. A lower point angle drill with a longer chip flute length produced the best results for drilling CARALL composites up to a specific point with minimum flank wear and chip adhesion.

Nanodiamond-structured zinc composite coatings with strong bonding and high load-bearing capacity.

The aerospace and automotive industries find that relying solely on the intrinsic resistance of alloys is inadequate to safeguard aircraft and automotive structural components from harsh environmental conditions. While it is difficult to attribute accidents exclusively to coating failure due to the involvement of multiple factors, there are instances where defects in the coating initiate a wear or degradation process, leading to premature and unplanned structural failures. Metallic coatings have been introduced to protect the aircraft mainly from wear due to the extreme temperatures and moisture exposure during their service life. Bare metallic coatings have a limited lifespan and need to be replaced frequently. Herein, the strength and wear resistance of zinc (Zn) coating is enhanced using varying concentrations of diamond particles as an additive in the Zn matrix (Zn-D). The dispersion strengthening mechanism is attributed to the high hardness (70 HRC), and reduced friction-of-coefficient (0.21) and dissipation energy (4.6 × 10-4 J) of electrodeposited Zn-D7.5 (7.5 g l-1 of diamond concentration) composite coating. Moreover, enhanced wear resistance with minimum wear volume (1.12 × 10-3 mm3) and wear rate (1.25 × 10-3 mm3 N-1 m-1) of the Zn-D7.5 composite coating resulted in perfect blending of diamond with Zn. The improved hardness and wear resistance for Zn-D7.5 (optimum 7.5 g l-1 diamond concentration) is due to the steadiness between well-dispersed diamonds in Zn and enrichment in load-bearing ability due to the incorporation of diamond particles. Electronic structure calculations on the zinc-diamond composite models (two configurations adopted) have been performed using the density functional theory (DFT) approach, and the in silico studies appeared to facilitate meaningful and evocative outcomes. Zn-doped diamond (C10@Zn) without hydrogen (H) atoms (binding energy: 418 kcal mol-1, i.e. showing an endothermic reaction and thermodynamically not favourable) was detected to be more stable than the Zn-doped diamond (C10H16@Zn) consisting of hydrogen (H) atoms (binding energy: -33.3 kcal mol-1, i.e. showing an exothermic reaction and thermodynamically preferable). Thus, a composite coating of zinc and diamond can be a suitable candidate for the aerospace and automotive industries.

МЕТОДИКА ВОССТАНОВЛЕНИЯ РАЗМЕРНЫХ СВЯЗЕЙ ПРИ РЕГУЛИРОВКЕ КЛАПАННОГО ЗАЗОРА В МЕХАНИЗМЕ ГАЗОРАСПРЕДЕЛЕНИЯ АВТОМОБИЛЬНОГО ДВИГАТЕЛЯ ВНУТРЕННЕГО СГОРАНИЯ

The relevance of research is due to the problems of organizing auto repair production in modern conditions associated with the difficulty of logistics and the high cost of foreign spare parts, which is confirmed by the analysis of domestic and foreign literary sources. Of particular importance in this case are the methods of optimizing the balance of costs for performing repair and restoration actions and replacing defective parts. The purpose of the work is to improve the quality of repair of rolling stock of road transport based on the use of methods for restoring dimensional connections. This study is designed to fill the existing knowledge gap caused by the lack of methods for restoring specific repair links. The use of new parts in repair, along with restored or used ones, necessitates the wider use of methods for optimizing the limit values of wear and recovery processes of dimension chain elements. The materials and methods of research are presented as an example of the development of a technique for restoring the necessary parameters of dimensional connections when adjusting the valve gap value, since the thermal gap in the timing mechanism of an internal combustion engine is an important element affecting the efficiency of the car engine. The scientific novelty of the work lies in the study of two different methods potentially suitable for implementation in the repair industry for restoring dimensional ties while reducing the valve gap by machining the outer or inner contact surfaces of car engine pushers. Studies have been carried out in relation to the decrease in the gap in operating conditions, which is widespread in automobile engines with overhead camshafts, since a decrease in the valve gap to a greater extent than an increase in it affects the efficiency of the machines. The equation of the size chain of the valve group is given, in which the valve gap is the closing link. As a result of sequentially discretely removing the surface layers of the pusher metal at 0.05 mm intervals and measuring the hardness of the surface layers, it has been found that this approach to restoring repair bonds can be recommended for use in auto repair production, with a more preferred method being to adjust the valve clearance by grinding the outer surface of the pushers. The data obtained can serve as the basis for further research in the development of a set of technologies for restoring specific size chains using repair kits that include parts with different manufacturing accuracy or that have been in operation.

FAILURE MODEL OF NON-RESTORABLE COMPLEX TECHNICAL OBJECT OF MILITARY EQUIPMENT

Maintenance (MT) is a necessary component the process of operating a complex technical object of military equipment, intended for long-term operation in wartime and harsh operating conditions. The volume, content and timing of maintenance must be completely determined by the reliability properties of the object, conditions and modes of its use. Effective implementation of any maintenance operation is possible only if the design of the object provides special means for this purpose (for measuring the defining parameters) and ensures the accessibility and convenience of performing the operation. Complex technical objects in modern society are extremely important. Such objects belong to the class of restored objects long-term repeated use. They are usually expensive and require significant operating costs. To ensure the required level of failure-free operation during their operation, maintenance is usually carried out, the essence of which is the timely preventive replacement of elements that are in a pre-failure state, which is very important for military equipment. A characteristic feature of complex technical objects for special purposes (military equipment) is the presence in their composition of a large number (tens, hundreds of thousands) different types of components that have different levels of reliability, different patterns of their wear and aging processes. This feature requires a more subtle approach to organizing and planning maintenance during operation (of military equipment). The above statements fully justify the conclusion about need to determine the main characteristics of the maintenance system in early stages of its design, when it is still possible to make changes to design of the object. In this work, a model of failure-free operation non-repairable complex technical object of military equipment is developed. The work also confirms the general idea that data obtained fully confirm the assumption that a maintenance strategy that is not restored is more preferable in the case of unreliable (inaccurate) information about the reliability indicators of elements of a military equipment object.