Wear Path Research Articles

Performance of Austenitic High-Nitrogen Steels under Gross Slip Fretting Corrosion in Bovine Serum.

Modular artificial hip joints are a clinical standard today. However, the release of wear products from the head-taper interface, which includes wear particles in the nm size range, as well as metal ions, have raised concerns. Depending on the loading of such taper joints, a wide variety of different mechanisms have been found by retrieval analyses. From these, this paper concentrates on analyzing the contribution of gross slip fretting corrosion at ultra-mild wear rates using a bovine calf serum solution (BCS) as the lubricant. The parameters were chosen based on biomechanical considerations, producing wear rates of some ng/m wear path. In parallel, the evolution of tribomaterial (third bodies) was analyzed as to its constituents and generation rates. It has already been shown earlier that, by an advantageous combination of wear mechanisms and submechanisms, certain constituents of the tribomaterial remain inside the contact area and act like extreme-pressure lubricant additives. For the known wear and corrosion resistance of austenitic high-nitrogen steels (AHNSs), which outperform CoCrMo alloys even under inflammatory conditions, we hypothesized that such steels will generate ultra-mild wear rates under gross slip fretting. While testing AHNSs against commercially available biomedical-grade materials of CoCrMo and TiAlV alloys, as well as zirconia-toughened alumina (ZTA) and against itself, it was found that AHNSs in combination with a Ti6Al4V alloy generated the smallest wear rate under gross slip fretting corrosion. This paper then discusses the wear behavior on the basis of ex situ analyses of the worn surfaces as to the acting wear mechanisms and submechanisms, as well as to the tribological reaction products.

AN IN-DEPTH INVESTIGATION ON KERF ANGLE IN PIERCED HOLE ON INCONEL-625 SUPERALLOY USING ABRASIVE WATERJET CUTTING PROCESS

This work investigates the piercing of microholes in turbine shroud rings (Inconel-625) using the Abrasive Waterjet Cutting process. The concern with the hole piercing is the kerf angle caused by the attenuation of the jet energy and stand-off distance, which seriously impacts the processing precision of abrasive water jet piercing. The effects of piercing parameters like machining time (40, 60 and 80[Formula: see text]s), abrasive mesh size (80 mesh and 120 mesh), stand-off distance (1, 2, 3 and 4[Formula: see text]mm), abrasive jet pressure (100, 125, 150 and 175[Formula: see text]MPa) are studied to reduce the kerf angle. The kerf angle increased linearly with a stand-off distance increase at different machining times. By piercing for 60[Formula: see text]s and 80[Formula: see text]s, the lowest values of kerf angle are obtained (0.03∘ and 0.02∘). The optimum conditions for making a pierced hole with a minimum kerf angle of 0.02∘ were achieved with a machining time- of 60[Formula: see text]s, abrasive mesh size- of 20 mesh, and abrasive jet pressure- of Scanning electron microscope (SEM) images and visual measuring system (VMS) images are used to identify the surface characteristics in kerf zone. The features, including ploughing, particle embedment, lip impression and wear path due to the ductile mode of erosion caused by high energy impact, is also discussed.

Effect of hydrogen concentration on the friction evolution mechanism of few-layer graphene: A molecular dynamics study in nanoscratch processes

This article explored the friction evolution mechanism of graphene under different hydrogen concentrations and scratch depths based on molecular dynamics. In a vacuum, graphene exhibits excellent frictional properties when the scratch depth is less than the layer distance of graphene. However, as the depth increases, the diamond tip contacts more CC bonds, and the phenomenon of fracture and recombination of CC bonds in the graphene layer intensifies, increasing surface friction. In a low concentration of hydrogen environment, compared with the friction in a vacuum, it increases due to the interlocking effect of the protruding hydrogen atoms on the diamond tip and the scratch path. As the concentration of the hydrogen environment increases, the friction force does not increase monotonically. In addition, in a hydrogen environment, the stability of the planar structure of graphene will be weakened, thereby affecting the wrinkling effect and wear path.

Evaluation of wear test on functionally graded metal-polymer tri-laminate composite interfaces of cooling-assisted friction stir additive manufacturing

In this study, a new friction stir welding (FSW) based additive manufacturing (AM) process called "cooling-assisted friction stir additive manufacturing (CA-FSAM)" was introduced to join sheets of metal-polymer hybrid structures (MPHS). Dry ice was introduced as the coolant. Thickness variations of the raw high-density polyethylene (HDPE) and 5083 aluminum alloy (Al5083) sheets were functionally graded at a rate of 0.75 mm from the former layer. The arrangement of layers in terms of thickness was arranged in the order of 3, 2.25, and 1.5 mm. Functionally graded metal-polymer tri-laminate composite fabricated with CA-FSAM technology was investigated using the pin-on-disk wear test. The results showed that mechanical locking between the layers affected the bond strength. Cross-sectional morphology examination revealed defect-free, strong joints. X-ray diffraction (XRD) results confirmed the formation of Mg2Si; however, the XRD peak was low, indicating a slight effect on the interface properties. Thermal gravimetric analysis (TGA)-Fourier transform infrared spectroscopy (FT-IR) characterization highlighted that the main evolved products during tri-laminate composite joining were CO, CC, CH3, CH2, and CH2. Oxidation occurred in the FTIR peak in the absorption band (1029.92 cm−1 to 1370.63 cm−1). Disk loading resulted in the buildup of an internal drag force that caused the dislocation/rupture of the CC or CH bonds. Defects, such as deep grooves, pits, and delamination at the interface, were observed in the composite specimen. The wear path was not visible in the worn composite material. The wear rate at 4 kg load on Al5083, HDPE, and metal-polymer tri-laminate composite specimens was 3.15 ± 0.22, 4.72 ± 0.36, and 3.42 ± 0.18 × 10−6 mm3/N. m, respectively.

Influence of elevated temperature and gas atmosphere on coke abrasion resistance. Part one: Pilot oven cokes

A novel approach was developed to examine coke abrasion resistance in-situ at temperatures of up to 950 °C and in a controlled gas atmosphere using rotational tribological testing. The originality of this approach lay in the ability to apply tribological testing to the porous coke surface at elevated temperatures under a controlled inert or CO2 reactive atmosphere. Coke wear characteristics were quantified via (i) the application of advanced microscopy and image analysis techniques, and (ii) analysis of the coefficient of friction (COF) during tribological testing.Two pilot oven cokes were examined in this study, which were generated from single coking coals of similar rank but different petrographic composition. The cokes tested showed a deterioration in abrasion resistance even at 400 °C, and this was accentuated at 950 °C.The COF and the severity of the wear as a function of temperature and gas atmosphere were markedly different between the two cokes. Coke C396 from a mid-to-low vol, medium vitrinite coal showed no statistically significant differences between the wear severity results recorded following room temperature testing and high temperature testing in a CO2 environment. Conversely, the more reactive coke C426 with a higher parent coal inertinite content showed clear differences in the extent of abrasive wear at room temperature and at high temperature in both inert and reactive gas atmospheres.This suggests that the reduction in abrasion resistance at elevated temperatures is accentuated in the coke with the highest coke reactivity index (CRI) and the highest content of inertinite maceral derived components (IMDC). Our research has shown that at room temperature, the IMDC show greater resistance to abrasion than the reactive maceral derived components (RMDC). This has implications for understanding the relevance of room temperature testing to the abrasion resistance of coke under practical blast furnace operation conditions. For example, a coke from a coal or blend with a comparatively high inertinite content may show lower resistance to abrasion in the blast furnace than would be expected from tumble drum indices. Larger sample numbers and cokes from a variety of single coals need to be tested in further work to verify these assertions.Finally, a novel method using micro-CT image analysis was developed to examine the wear path generated at the coke surface during tribological testing. The purpose of this was to assess the extent of the abrasive wear by comparing the rendered micro-CT images before and after tribological testing. A colour gradient scale was used to facilitate the quantitative assessment, whereby the colour of each voxel was based on the distance from the nearest voxel that is associated with solid phase.As expected, the specific surface area (SSA) calculated for the upper 1 mm of each sample decreased following tribological testing due to the generation of a wear track which is smoother than the initially rough, porous coke surface. In the C426 coke type examined, the SSA decreased the most for the sample tested in an argon atmosphere at 950 °C, matching the COF and quantified wear severity results, which showed there was a notable increase in abrasive wear to this coke as the temperature was raised from room to elevated temperature.Coupling this method of analysis with 3D visualisation techniques in further work would provide a powerful approach to examine and quantify mechanisms of coke surface breakage and the microstructural and/or microtextural features responsible for the breakage.

Eudora Welty Foundation 2022 News

Eudora Welty Foundation 2022 News Jeanne Luckett The Eudora Welty Foundation, often working in collaboration with the Eudora Welty House & Garden, helped promote and produce an increased number of in-person activities in 2022 as the Coronavirus (COVID–19) abated to a degree. Although some virtual programming continued, many events were held outside on the lawn of the Welty House and in the Welty Garden. Some programs that had been postponed were finally held. A most significant occurrence for the Foundation in 2022 was its receipt of a grant from the Mississippi Arts Commission to assist with the construction of an Education Center on the property immediately behind the Visitor Center which is next door to the Welty House. Mississippi Arts Commission Grant Facilitates Education Center Construction Plans for an Education Center to host larger audiences than the Welty Visitor Center can seat were greatly enhanced when the Eudora Welty Foundation received a $225,000 Building Fund for the Arts (BFA) grant from the Mississippi Arts Commission (MAC). MAC is a state agency that receives funding from the National Endowment for the Arts, the Mississippi Legislature, and other resources. Of forty-six applicants, the Foundation was one of sixteen to receive a BFA grant. The Foundation had already begun fundraising and is continuing to raise the grant match and the balance needed. Maggie Bjorgum of Belinda Stewart Architects, PA, of Eupora, MS, has developed architectural plans, and site work is already underway. The Visitor Center garage where garden supplies and tools have been stored will be torn down. The Welty House garage has been repurposed as a garden shed, thanks to a grant from the Garden Club of Jackson and help from the Foundation. The Education Center will be completed within two years and will accommodate a variety of activities and events. The new building [End Page 181] will have, among other amenities, a large meeting room, a kitchen, and a covered back porch and will be donated by the Foundation to the Mississippi Department of Archives and History when completed. Welty At Home Virtual Book Club Held via Zoom Continues To Thrive Begun in 2020, the virtual Welty at Home Book Club was a success throughout 2022. With participation growing, Zoom capacity was increased to permit more than 100 participants. The Welty House staff manages the technical operations, and Welty Foundation scholar-in-residence Suzanne Marrs leads most discussions, with readers actively engaged in comments. Programs from January through March focused on William Faulkner's The Sound and the Fury with guest lecturer Jay Watson, Howry Professor of Faulkner Studies at the University of Mississippi. Welty's The Wide Net and Other Stories was read and discussed May–July. Jane Austen's Pride and Prejudice was the subject September–November. To sign up for the Book Club and receive the Zoom link, call 601–353–7762 or email info@eudoraweltyhouse.com. For a participant's view of Welty at Home, see University of Mississippi Jacob Agner's story about the Book Club in the Eudora Welty Review, Volume 14, 2022. Author Ron Rash Delivers Bettye Jolly Lecture at Welty Garden Acclaimed author Ron Rash presented the Bettye Jolly Lecture in the Welty Garden on September 22 to a large and enthusiastic audience. The lecture was delayed two years because of Covid. Rash discussed his appreciation of Welty's work and noted that he teaches "A Worn Path" in his classes at Western Carolina University. He read from "The Belt," a story from In the Valley. He also read one of his poems "3 a.m.: The Stars Were Out" and noted that he had become a better poet by writing fiction. The lecture may be viewed on the Welty Foundation website: eudorawelty.org. Search: Ron Rash Lecture. Rash is the author of seven novels, seven collections of short stories, six poetry collections, and a children's book. An endowed program of the Welty Foundation, the lecture honors the late Bettye Jolly, a volunteer and supporter of the Welty House & Garden. [End...

Growth Kinetics, Microstructure Evolution, and Some Mechanical Properties of Boride Layers Produced on X165CrV12 Tool Steel

The powder-pack boriding technique with an open retort was used to form borided layers on X165CrV12 tool steel. The process was carried out at 1123, 1173, and 1223 K for 3, 6, and 9 h. As a result of boriding the high-chromium substrate, the produced layers consisted of three zones: an outer FeB layer, an inner Fe2B layer, and a transition zone, below which the substrate material was present. Depending on the applied parameters of boriding, the total thickness of the borided layers ranged from 12.45 to 78.76 µm. The increased temperature, as well as longer duration, was accompanied by an increase in the thickness of the FeB zone and the total layer thickness. The integral diffusion model was utilized to kinetically describe the time evolution of the thickness of the FeB and (FeB + Fe2B) layers grown on the surface of powder-pack borided X165CrV12 steel. The activation energy of boron for the FeB phase was lower than that for the Fe2B phase. This suggested that the FeB phase could be formed before the Fe2B phase appeared in the microstructure. The high chromium concentration in X165CrV12 steel led to the formation of chromium borides in the borided layer, which increased the hardness (21.88 ± 1.35 GPa for FeB zone, 17.45 ± 1.20 GPa for Fe2B zone) and Young's modulus (386.27 ± 27.04 GPa for FeB zone, 339.75 ± 17.44 GPa for Fe2B zone). The presence of the transition zone resulted from the accumulation of chromium and carbon atoms at the interface between the tips of Fe2B needles and the substrate material. The presence of hard iron and chromium borides provided significant improvement in the wear resistance of X165CrV12 steel. The powder-pack borided steel was characterized by a four times lower mass wear intensity factor and nine times lower ratio of mass loss to the length or wear path compared to the non-borided material.

The effect of friction stir process on the mechanical, tribological, and biocompatibility properties of AZ31B magnesium alloy as a biomaterial: A pilot study.

Recently, AZ31B magnesium alloy has been widely employed in automotive, aerospace, and bio implant industries due to its light-weight and biocompatibility properties. However, the equilibrium of ductility and strength of this material and the negativity brought by its poor wear behavior have limited its versatile use. Friction stir processing (FSP) has been commonly used as severe plastic deformation method for improving mechanical and tribological properties of metal sheets. The effect of this method on the biocompatibility of materials is a matter of curiosity that should be emphasized. So, the present study aims to investigate the effect of friction stir process on the mechanical, tribological, and biocompatibility properties of AZ31B magnesium alloy. It is observed that FSP enhanced the tensile properties of the alloy but decreased its elongation. It was determined that the base material exhibited ductile character on the fracture surface of the specimens, and mixed ductile/brittle fracture was evident with the FSP. In the FSP zone, the hardness value was improved by 17% compared to the base material. Also, the wear performance of the alloy enhanced in ambient air and Simulated Body Fluid (SBF) solution. Wear properties in SBF solution were better due to less adhesive bonds between the friction surfaces. This assessment was supported by SEM images of the wear path and surface of counter bodies. On the other hand, FSPed AZ31B alloy materials with improved strength properties were not cytotoxic for human gingival fibroblasts, and these results may suggest that the materials are safe for clinical uses.

The Old Federal Road in Alabama: An Illustrated Guide by Kathryn H. Braund, Gregory A. Waselkov, and Raven M. Christopher

Reviewed by: The Old Federal Road in Alabama: An Illustrated Guide by Kathryn H. Braund, Gregory A. Waselkov, and Raven M. Christopher Christine E. Sears The Old Federal Road in Alabama: An Illustrated Guide. By Kathryn H. Braund, Gregory A. Waselkov, and Raven M. Christopher. Tuscaloosa: The University of Alabama Press, 2019. 176 pp. $24.95. ISBN 978-0-8173-5930-0. The Old Federal Road in Alabama is a vivid and witty travel companion. The first part tells the history of the Old Federal Road and the second lays out a guide for touring Alabama’s Old Federal Road. The work blends historical context with the experiential to connect us to a time during which the “land and its people were remade” (93). The first section draws on recent scholarship on Creek Indians in the Southeast to provide a succinct and inclusive history of the ancient path that would one day become a road. The foundation was “laid by Indian feet” (7) which used the path for generations. Deer skin traders and native peoples traversed the footpath up to the Seven Years’ War. At war’s end in 1763, the Spanish and French were ejected while the British set up trading posts in Mobile and Pensacola, making “formerly minor paths to the Gulf Coast … major routes” (11). After the American Revolution, American settlers charged into what are now Georgia and Tennessee, straining Creek-US relations. The US government demanded road and waterways through Creek territory while pushing a “civilization policy” (12) to transform Creeks and other Indians into settled farmers. Creeks, through whose land much of the Old Federal Road passed, farmed proficiently and had already selectively adopted many Anglo practices. The authors give ample time to Creek resistance to Americans passing through and squatting on their land, as well as to those Creeks who leveraged the needs of travelers for their own gain. The broad outlines of nineteenth-century changes are likely familiar, but the authors, by anchoring their work around the road, add important depth to that outline. Readers will not be surprised that the Louisiana Purchase instigated a transformation along the worn path. But not just Anglo settlers journeyed to the new territory. The federal government and military needed improved access to the territory for communication and defense, particularly in regard [End Page 256] to the real prize of the Purchase, the port of New Orleans. Further, the Creek were not completely sidelined by Anglo immigration in the early 1800s. Many travelers hired Creek Indians as post riders. Creeks, like Samuel Moniac, constructed houses on the route to provide fresh horses, fodder, and a stopping place on the unpopulated roadway. The year 1811 proved a pivot point in pushing the “barely tolerable path” (5) to a wheel-worthy road. Importantly, the authors highlight the federal government’s role in this change. In 1811, the US Army widened the trail and built bridges along it. In the early 1800s, the government forced Creeks to cede much of their land. And whites increasingly owned the inns and stage stops along the road while Creeks were relegated to menial jobs. The Old Federal Road, the authors note, was a “conduit that enabled both immigration and deportation” (90), moving Creek inhabitants out and cotton planters with enslaved peoples in. The United States had transformed the area from Creek territory to the Cotton South. The work is enlivened with carefully chosen illustrations that are equally inclusive. A detailed 1773 French map of Louisiana (10) highlights existing Indian trails, including some that became the Alabama Old Federal Road. An 1802 Georgia passport giving a white man permission to travel through Creek Nation territory (17) indicates Creek control of their land. Multiple illustrations of Creek Indians give faces and form to Creeks living along the path (64-65). Photos of the contemporary landscape add life to the tour guide section of the work. My favorite is the photo of an evening primrose (139), a flower written about by William Bartram, who traveled to the area in 1775. The lovely primrose grows only around Stockton, Alabama. The book’s second part is sub-divided into three sections—into the Eastern, Central, and Southern segments...

The Mechanical and Tribological Properties of Epoxy-Based Composites Filled with Manganese-Containing Waste.

Waste from large-scale production processes is a growing environmental problem that can potentially be solved by using this waste as fillers in polymeric composites to improve the mechanical and tribological properties of polymeric matrixes. This paper presents research concerning how the introduction of fillers in the form of manganese residue and manganese(II) oxide changes the mechanical and tribological properties of epoxy composites produced by gravity casting. The research was carried out for composites with 2.5 wt.%, 5 wt.%, and 10 wt.% of fillers. Properties such as the density, hardness, resilience, flexural strength, deflection, flexural modulus, tensile strength, elongation at break, and Young’s modulus were determined. Moreover, based on the ball-on-plate test, the wear volume and friction coefficients of the tested materials were determined. Microscopic images of the abrasion profiles were also obtained. The geometry of the wear paths was measured with a profilometer, and the results showed that introducing fillers reduced the abrasive wear of the composites; however, in all cases, the fillers decreased the strength of the tested materials.

Properties of Semisolid Parts: Comparison with Conventional and Innovative Manufacturing Technologies

In this paper, wear properties of samples manufactured using thixocasting were compared with those of components obtained using low-pressure die-casting and additive manufacturing in order to assess the relationship between material performance and production technologies, both conventional and innovative. The investigated items were made with AlSi7Mg alloy. First, microstructural analysis and hardness measurements were carried out. Subsequently, pin-on-disk wear tests were performed. Wear behavior of the samples was studied considering both coefficient of friction and wear rate, while the damage mechanism was analyzed by observation of the worn paths using scanning electron microscope, correlating the behavior to the specific microstructure. In addition, the effect of selected heat-treated conditions, relevant for real applications, on wear properties was also evaluated.

Способы передачи просторечий при переводе художественного текста с английского языка на русский

The article covers the problems of commentary in translation of fiction, related to the difficulties of conveying low colloquialisms and ways to solve them and achieve the most adequate translation (meaning extension, loss-of-meaning compensation, descriptive equivalence in translation, concretization, generalization) with examples of the author's translation from the story by Eudora Welty “A worn path”. The paper includes the most interesting moments for translation associated with the speech image of the main character.

Wear and friction analysis of bio-ceramic cordierite system as orthopedic material

Wear affects the performance and lifetimeof implants, and it is a major cause of primary failure in artificial hip joints. The aim of this research is to examine and determine wear inceramic-on-ceramic hip implants. The cordierite system was used to create the composite ceramic materials, which were synthesizedvia thecoprecipitation technique. The AMTI Orth-POD machine has beenused for testing 5systems for pin on disc wear. The dry and wet wear tests were carried out in physiologically relevant conditions. After 5,000 cycles of sliding velocity 81.4487 mm/s, normal load 50 N,and circular wear paths, gravimetric analysis was utilized to describe wear. The simulated bodyfluid functions as lubricants, and the results show that the coefficient of friction decreaseswhen the aluminaconcentration increases.

The Characters of Children in Alice Walker’s “Everyday Use” and Eudora Welty’s “A Worn Path”: A Comparative Study

This article tries to compare between two well-known American short stories, “A Worn Path” by Eudora Welty and “Everyday Use” by Alice Walker, from a comparative perspective. The author of the first of these stories is an African-American novelist, short story writer, poet, and social activist. Alice Walker and the other story is written by an American short story writer, novelist and photographer, who wrote about the American South, Audra Welty. The specific reasons behind choosing these two short stories because they are written by women writers from different cultures, both deal with racial issues, but more importantly is that both include children characters that can add an attribution to be representations of the new African- American generation. Walker’s story includes the characters of two African- American daughters; Maggi and Dee, each of these characters behave in a different way, a behavior which consequently represents a special attitude towards the new generation of African- Americans. While in Welty’s story, we find the character of the grandson of the protagonist, Phoenix, who has a disease which deprived him from his ability to speak. This study analyses how these three characters provide different angles of seeing how the new generation of African- Americans is represented through a comparative outlook.

Characterization and Modeling of Nano Wear for Molybdenum-Based Lubrication Layer Systems.

As a result of global economic and environmental change, the demand for innovative, environmentally-friendly technologies is increasing. Employing solid lubricants in rolling contacts can reduce the use of environmentally harmful greases and oils. The aim of the current research was the development of a solid lubricant system with regenerative properties. The layer system consisted of a molybdenum (Mo) reservoir and a top layer of molybdenum trioxide (MoO3). After surface wear, Mo is supposed to react with atmospheric oxygen and form a new oxide. The determination of the wear volume of thin layers cannot be measured microscopically, which is why the wear behavior is initially determined on the nano level. In this work, single Mo and MoO3 coatings prepared by physical vapor deposition (PVD) are characterized by nano testing. The main objective was to determine the wear volume of the single coatings using a newly developed method considering the initial topology. For this purpose, nano-wear tests with different wear paths and normal forces were carried out and measured by in situ scanning probe microscopy (SPM). Based on the characteristic values determined, the coefficient of wear was determined for wear modeling according to Sarkar. The validation of the wear model developed was carried out by further wear tests on the respective mono layers.

Effect of ellipse motion paths with different aspect ratios on friction and wear of highly crosslinked polyethylene

Cobalt chromium molybdenum alloy and highly cross-linked polyethylene are selected as the counterpairs in this study to carry out friction and wear testing over different ellipse motion paths to explore the influence of ellipse motion path on friction and wear of prosthesis materials. Here, the analytical methods for the periodic friction coefficient and special point wear are proposed to investigate the relationship between motion paths and tribological properties. The damage mechanism model of high cross-linked polyethyleneunder ellipse motion paths was established, which revealed the connection among material composition, motion paths and friction and wear mechanism. The results show that the friction coefficient and wear morphology are directly affected by changes in motion paths. The friction coefficient decreases with increasing aspect ratios, and the wear profile depth increases with increasing aspect ratios. The spatially resolved friction coefficient curve distinctly exhibits periodic “W”-type variation in elliptical motion paths. The friction coefficient shows maximum values at the long-axis endpoints and minimum values at the short-axis endpoints. There are different wear morphologies in different characteristic areas over the elliptical wear paths. The wear profile depth and width at the long-axis endpoints are larger than those at the short-axis endpoints, and the wear morphology is also more serious.

A Study of the Wear Resistance of the Surfaces of Components via a Strengthened Combined Electromechanical Method

The issues of the process of hardening of parts made from steel 45 by a combined method were considered, which consisted in the application of coating by electric-arc metallization, subsequent lathe work, diamond surface smoothing and pulsed magnetic refinement. Parts that were hardened by a combined method were analyzed for durability. A pilot plant for the study of parts for durability resistance was described. The results of the research are presented. The nature of wearing of the component surfaces hardened by the combined method has been established. According to the test results, it was found that in the process of wear of component surfaces hardened by a combined electromechanical method no run-in occurred. The period of normal exploitation began immediately after the start of the work. The surface of the analyzed part after burnishing deformation by the diamond smoothing method works for a long period of time practically without abrasion. According to this, wear products do not enter the friction zone and cause abrasive wear. The destruction of the surface does not affect the entire surface simultaneously, it occurs in its individual sections. Other sections are only vulnerable to physico-chemical changes. Such partial destruction and changes features of the surface affect the interaction of the conjugate surfaces. Pulsed magnetic refining also increases the wear path by changing the physico-mechanical properties of the original material. The wear stages of coating surfaces hardened by diamond smoothing and pulsed magnetic refinement last longer.

Service Behavior of Nitride Layers of Steels for Military Applications

Steels which are utilized in the manufacturing of specific parts of military technology such as crankshafts of engines in heavy-duty vehicles or barrels of guns must be subsequently modified by heat treatment according to the requirements of customers. Despite the hard surface of martensitic structure obtained by hardening process, steels have a low wear resistance and high values of coefficient of friction. To improve these parameters and due to the fact that many of steels which are utilized for manufacturing of mentioned parts are also categorized as Nitralloy steels, in this paper, the improvement in these properties of chosen steels by the application of plasma nitriding has been studied. The steel equivalent 17Ni4CrMo (i.e., CSN 41 6720) and equivalent 42CrMo4 (i.e., CSN 41 5142) were chosen for the study. The chemical composition of chosen steels was verified by optical emission spectrometry. The microstructure and the diffusion layer were observed by optical microscopy due to the evaluation of layer parameters important for the lifetime. ZWICK ZHU 2.5 was used for a measurement of the universal hardness of the surface and values of graphs of microhardness were obtained by the device LM 247AT LECO from a cross-section of samples. The coefficient of friction was determined by Bruker CERT-UMT-3 with a ball-on-disc method. The parameters of wear paths were obtained by Talysurf CLI 1000. After the application of plasma nitriding technology, the hardness of both steels was rapidly increased in comparison with non-nitrided samples. According to the comparison of coefficients of friction with respect to the parameters of the measurement, the coefficient of friction of nitrided samples decreases with increasing temperature, which is essential knowledge for the weapon industry, especially the construction of bore barrel.

Dialogic Pedagogy: Teaching English Literature in Korean Classrooms

Most of my students taking English literature courses have tended to be inactive and to have an anxiety about presenting their own views on literary texts. Many students preferred just listening to a lecture passively in their safe zone without being disturbed. I, however, am skeptical about passive learning because students have a better chance of realizing their potential when they participate in class actively. I think dialogic teaching can be a pedagogical alternative to a traditional lecture which allows students to be passive and uninvolved in class activities. Dialogue is not a one-sided but a two/multi-sided communication. And individuals grow through dialogic communications. Therefore, dialogic teaching which welcomes dialogues and communications does not look for only one monologic, authoritative and right answer/truth in classrooms. Dialogic teaching gives students voices and makes them creative as well. This paper deals with the possibility of dialogic teaching in English literature classes for Korean students. Firstly, the cultural backgrounds which make dialogic teaching difficult in Korean classrooms are discussed. In particular, Confucian virtues which can be obstacles to dialogic teaching are examined. Secondly, I explore the dynamics of dialogism which can be applied to teaching English literature, dealing with Paulo Freire’s pedagogy. Thirdly, I go over one of my English literature classes in which Eudora Welty’s “A Worn Path” has been discussed. And finally, I examine what the four-step routine is and how it works for dialogic teaching. Dialogic teaching makes students’ potential realized and their voices heard. Students learn how to communicate with each other, acknowledging the self-other relationship in a dialogic classroom. With supporting students’ growth, teachers are transformed as well.

Metoda modelowania degradacji obrotowego uszczelnienia wargowego w oparciu o analizę mechanizmu uszkodzenia i proces stochastyczny

Rotary lip seal is widely used in aircraft and its performance affects the safety of the aircraft. Hence, it is necessary to estimate useful lifetime and reliability of the seal. Degradation of rotary lip seal is always with random effects, which cannot be considered by theoretical failure mechanism analysis. Hence, in order to consider the random effects of rotary lip seal degradation, stochastic processes are applied. Furthermore, considering the monotonic degradation of the seal, Gamma process and inverse Gaussian process are selected as the candidate processes. To combine the candidate processes, Bayesian model averaging is introduced. Based on the failure mechanism analysis and numerical simulation, the theoretical wear path is predicted and corresponding linearization method is proposed. The measured degradation data is converted and the seal wear process is transformed to a linear degradation process. The model parameters and model probabilities are evaluated by fully Bayesian inference method. The effectiveness of the proposed method is verified by comparing the predicting degradation and experimental observations. The proposed method can be used to evaluate reliability and useful lifetime of rotary lip seal. According to sensitivity analysis, an effective way to improve lifetime and reliability of the seal is to increase the wear depth threshold.