Steel Disc Research Articles

Tribological Behavior of Structural Steel with Different Surface Finishing and Treatments for a Novel Seismic Damper

In the context of developing an innovative seismic dissipation system, which aims to compromise on the steadiness of friction and processes costs, this work deals with the tribological characterization of an S355JR structural steel, whose surface has been preliminarily treated by different mechanical and galvanic processes. Tribological tests were performed in a pin-on-disk configuration and in reciprocating motion, using values of 1 Hz and 2 Hz as the motion inversion frequency, a constant normal load of 50 N, and variable test duration, according to the most frequent seismic events. The tribological system was composed of S355JR structural steel pins and disks of the same steel, which were alternatively treated by electrolytic nickel plating, electrolytic zinc plating, and two different shot peening processes. The results highlight that while electrolytic nickel increments the overall steadiness of the coefficient of friction (COF), electrolytic zinc plating guarantees the longest first steady-state stage and a COF lower than the one guaranteed by the coupling of untreated pins and disk.

On the Photo-Eradication of Methicillin-Resistant Staphylococcus aureus Biofilm Using Methylene Blue.

This work compared the effectiveness of several Methylene Blue (MB)-based protocols for photo-eradication of biofilms formed on the surface of the glass and stainless steel discs by S. aureus MRSA isolates using a diode laser (λ = 665 nm; output power 40 mW; energy fluence was 189 J cm-2). The results obtained showed that MB alone, up to a concentration of 62.5 mgL-1, had limited photo-bactericidal activity. It was possible to enhance the activity of MB using two types of spherical gold nanoparticles of similar sizes, 15 ± 3 nm/20 ± 3 nm, but differing in the method of their synthesis and stabilization. The enhancement of the photodestruction effect was related to the increased production of hydroxyl radicals by the MB+gold nanoparticles mixture, and this mixture showed dark cytotoxicity against the cocci studied. Effective destruction (mortality above 99.9%) of the biofilms formed by MRSA isolates was also possible without the use of gold nanoparticles, but the concentration of MB had to be at least 125 mgL-1. A highly efficient protocol of photodestruction of biofilms, consisting of triple exposure of biofilms to laser light in the presence of MB alone, combined with the removal of dead bacteria protecting deep layers of pathogens against photosensitization, was also described.

Vibration based adhesion for underwater robotic operation

In the face of underwater non-magnetic wall environments, the existing underwater adsorption mechanisms are difficult to achieve continuous adhesion without destroying the surface, and the combination of vibration and underwater adsorption will help to solve this problem. The underwater vibration adhesion mechanism of rigid body proposed in this paper uses vibration to form adhesion on the surface of the object, and explores the influence of vibration frequency, driving current and driving disc radius from the perspective of displacement change, and tests the application: A stainless steel disc with a thickness of 0.5 mm and a radius of 50 mm can continuously adhere to a mass load of 1 Kg at a frequency of 150 Hz, and can adhere to the surface of seashells at a frequency of 100 Hz. The underwater vibration adhesion of rigid body is a new adhesion technology, which can be used in the fields of underwater wall climbing robots and underwater object grasping.

Condition monitoring of pitting evolution using multiple sensing

Pitting on surfaces is a type of rolling contact fatigue (RCF) occurs in rolling-sliding contacts operating under mixed or boundary lubrication conditions. The early detection of pitting is of great importance due to its potential detrimental effects on the performance and reliability of machinery components, such as rolling element bearings and gears. This research aims to investigate the responses of multiple sensors to the progression of pitting and achieve early detection of pitting initiation. Experiments were conducted on a TE74 twin-disc tribometer to investigate the behaviour of bearing steel discs. Mild wear and pitting fatigue were obtained with specimens of different roughness combinations. During testing, vibration, acoustic emission (AE) and electrostatic (ES) data were recorded, and post-test signal analysis was conducted in both the time domain and frequency domain. After testing, the worn surfaces were examined to determine the mechanisms responsible for specific features seen in the sensor data. The presence of pitting in the near-surface region was observed, and its development was effectively monitored using the employed sensing techniques. The stages of running-in, pitting initiation, and pitting formation were identified through the analysis of time-domain parameters and frequency spectrums. Vibration signal analysis exhibited a more prominent indication of pitting formation, whereas AE and ES methods demonstrated an ability to detect the onset of pitting at an earlier stage.

Increase of Wear and Heat Resistance of the AISI 304 Steel Surface Layer by Multi-Pass Nanostructuring Burnishing

The paper presents the results of experimental studies of the AISI 304 steel disc surface after finishing turning, electropolishing and nanostructuring burnishing after one and five passes of the tool with a natural diamond tip with a radius of 2 mm. It is shown that surface layer nanocrystallization provides for almost complete decomposition of austenite in a layer up to 100 µm thick, an increase in microhardness up to 400...450 HV0.025 and a 3.3-fold reduction in the wear intensity on hardened AISI 1045 steel under conditions of lubrication with industrial oil compared with electropolishing. The content of residual austenite in the surface layer is not more than 5% when the temperature rises to 400°C.

Self-centering beam-column joints with variable stiffness for steel moment resisting frame

Different from the self-centering joint with constant post-yield stiffness (CS joint), self-centering joint with various post-yield stiffness (VS joint) is proposed to control the seismic responses and improve the seismic resilience of frame structures under the extremely rarely occurring earthquake (EROE) level. The angle steel connectors and disc springs are adopted to provide the energy dissipation and self-centering capacities of the VS joint, respectively. First, theoretical study and pseudo-static tests are conducted, the results show that the VS joint has two stages of stiffness after the joint gap opens; the joint can deform and dissipate energy during the first stage with ordinary post-yield stiffness when the rotation angle of the joint is small; with the increase of the joint rotation angle, the weak stack of disc springs is flattened, causing the joint to enter the second stage with strengthened post-yield stiffness. It is found that the smaller the deformation capacity of the preloaded weak stack, the smaller the begin rotation angle of the second stage; the larger the stiffness of the strong stack, the larger the strengthened post-yield stiffness. Then, the updated displacement-based design method suitable for the frame structure with the VS joints (VSF structure) is also proposed. The non-linear dynamic time analysis results show that the plastic damage of the general moment resisting frame structure (GF structure) is severe and exceeds the extent of repairability under the EROE level; both the frame structure with the CS joints (CSF structure) and VSF structure have similar structural responses under the frequently occurring earthquake (FOE), the moderately occurring earthquake (MOE) and the rarely occurring earthquake (ROE) levels, and both can avoid plastic damage and have good self-centering capability even under the EROE level; due to the strengthened post-yield stiffness of the VS joints, the displacement responses of the VSF structure under the EROE level can be effectively controlled, while this is difficult for the CSF structure, whose responses exceed the performance target.

Effect of B4C/Gr on Hardness and Wear Behavior of Al2618 Based Hybrid Composites through Taguchi and Artificial Neural Network Analysis

Artificial neural networks (ANNs) have recently gained popularity as useful models for grouping, clustering, and analysis in a wide range of fields. An ANN is a kind of machine learning (ML) model that has become competitive with traditional regression and statistical models in terms of useability. Lightweight composite materials have been acknowledged to be the suitable materials, and they have been widely implemented in various industrial settings due to their adaptability. In this research exploration, hybrid composite materials using Al2618 reinforced with B4C and Gr were prepared and then evaluated for hardness and wear behavior. Reinforced alloys have a higher (approximately 36%) amount of ceramic phases than unreinforced metals. With each B4C and Gr increase, the wear resistance continued to improve. It was found that microscopic structures and an appearance of homogenous particle distribution were observed with an electron microscope, and they revealed a B4C and Gr mixed insulation surface formed as a mechanically mixed layer, and this served as an effective insulation surface that protected the test sample surface from the steel disc. The ANN and Taguchi results confirm that load contributed more to the wear rate of the composites.

Influence of areal surface parameters on the tribological behavior of Ti6Al4V under lubricated condition

The present work investigates the influence of areal surface parameters according to ISO 25178 on the tribological behavior of Ti6Al4V alloy. Experiments on lubricated sliding wear at varied weights and sliding speeds were conducted using the pin-on-disk tribo test with an EN31 steel disk as the counter body and SAE40W15 as the lubricant in accordance with ASTM G-99. The lowest friction coefficient was obtained at 3 m/s sliding velocity and was independent of normal load, however the wear rate increased with increase in normal load. Vvv, Svk, Spk, Sk, Sku, Sk and, Sq had shown strong correlation with CoF and wear depth. Spk had a correlation coefficient of −0.8247 with CoF, and Vvv had a correlation coefficient of - 0.8415 with wear depth. Vvv and Svk retained the lubricant and increased the life of the component.

Fabrication of a High Wear Resistance AA7075/AL2O3 Composites Via Liquid Metallurgy Process

In the present study, AA7075/Al2O3 composites have been fabricated via liquid metallurgy process. AA7075 alloy and Al2O3 particles were taken as the base matrix and reinforcements, respectively. Then, contents of 3 and 6 wt. % of Al2O3 subdivisions were added into the AA7075 matrix. To improve wettability and distribution, reinforcement particles were pre-heated to a temperature of <i>550°C</i> for each composite sample. A hardened EN32 steel disc as the counter face was used to evaluate the wear rate pin-on-disc. The results showed that the wear rate of the AA/Al2O3 composites was smaller than that of the monolithic AA7075 samples. Finally, the worn surfaces of samples were investigated by SEM.

A generalized method for numerical modeling of seismically resilient friction dampers using flat slider bearing element

There has been a growing interest in recent years by both researchers and industry in developing friction dampers that have enhanced seismic performance by using inclined friction interfaces (i.e., not colinear with the plane of loading) in combination with a re-centering mechanism such as steel disc springs and/or SMA materials. These friction and friction-hybrid dampers provide both energy dissipation and self-centering characteristics. Compared to conventional flat-slider friction dampers (where friction interface is colinear with the plane of loading), numerical modeling of these types of friction devices is not straightforward and requires unique material models or complex element configurations to predict earthquake building responses. This technical note provides a generalized numerical model implemented in the OpenSees structural analyses framework that could be broadly applied to the numerical modeling of seismically resilient type friction dampers. The modeling scheme presented in this study utilizes readily available elements (i.e., flat-slider bearing element), eliminating the need and complexity of creating new material models. Given the increased interest found in the literature in the development of friction dampers with re-centering characteristics, this technical note could be useful for both researchers and engineers. Illustrative examples using two distinctly different seismically resilient friction dampers are presented for validation of the proposed modeling scheme. The first comparison is made with a cross-laminated timber rocking wall detailed with a newly proposed Uplift Friction Damper (UFD). Comparisons are made with both quasi-static cyclic tests and a continuum finite element numerical model in the ABAQUS software program. The second validation example compares results with a quasi-static uniaxial cyclic test of a Friction Spring Damper (FSD) device. Predictions of the proposed generalized numerical model are in good agreement with the results of both validation examples.

Effect of groove textures on tribological properties of 40CrNiMoA steel under starved grease lubrication

40CrNiMoA steel is widely used in important mechanical parts under starved lubrication, such as shafts, gears and flexsplines for harmonic reducers. To improve the tribological properties of 40CrNiMoA steel and prolong the service life of the material in practical application, micro-grooves were fabricated on steel discs by laser texturing. The texture areal density is controlled by the number and width of the micro-grooves. The friction tests were carried on a ball-on-disk friction tester. The worn surfaces were observed by a scanning electron microscope and a three-dimensional microscope to discuss the friction and wear properties of textured discs under starved grease lubrication. The results show that the groove texture can effectively improve the tribological performance of the 40CrNiMoA steel. After optimizing, the tribological properties were greatly improved. The average friction coefficient reduced from 0.259 to 0.116 and wear rate was reduced by about 46 times. The contact stress of ball and textured discs was analyzed, the results shown that larger width of groove lead to higher contact stress, which may increase friction and wear. Therefore, storing lubricants and increasing contact stress should be balanced to obtain better tribological performances. In this study, the preferred range of texture areal density is 10% ∼ 22%.

Effect of Temperature and Sliding Velocity on the Dry Sliding Wear Mechanisms of Boron Modified Ti-6Al-4V Alloys

The dry sliding wear behavior of as-cast pristine and boron-modified Ti-6Al-4V (Ti64) alloys (having 0.3 and 0.55 wt% B) is investigated using pin-on-disc experiments with the pin being Ti64 alloy and the EN31 steel disc. Experiments are performed at sliding speeds (s) of 1, 2, and 4 m/s and temperatures 300 and 573 K. A mixed response in wear behavior is observed. At the lowest sliding speed, all three alloys (except 0.55B alloy at 300 K) exhibit similar wear rates, with abrasive wear being the dominant wear mechanism. At 2 m/s, temperature and s increase, and adhesive wear takes over along with delamination wear. Here, the 0.55B sample shows the highest wear rate due to the debonding of more TiB particles, which increases three body abrasion wear. With further increase in s to 4 m/s, delamination and oxidation wear are observed for all the samples. XRD evaluation shows traces of TiO2 and Fe2O3, which imply the formation of MML in samples tested at s = 4 m/s, which is also validated through subsurface microstructure analysis. It is found that MML having more TiB particles has more stability, because of which 0.3B samples show higher wear rate.

The effect of diamond like carbon coating on the wear resistance at dry sliding conditions

Wear due to sliding is an inevitable problem in many engineering applications. Protective surface coating is usually used to mitigate this problem. The development in this field is continuous and consistent. There are many types of coatings according to their compositions and the deposition methods. One of the coatings with the most promising properties, such as the hardness, is the Diamond-Like Carbon (DLC) coating. The tribological properties of this coating generated by Plasma-Assisted Chemical Vapor Deposition (PACVD) and applied on bearing steel 52100 ASTM are not available. In this study, the wear resistance of the DLC coating applied to bearing steel 52100 ASTM, was evaluated. The coating method employed was PACVD, which is regarded as one of the most distinctive coating techniques due to the unique tribological properties imparted to the coating. The pin-on-disc tribometer was used to examine the coefficient of friction and mass losses for samples of (steel disc against steel ball) and (DLC coated disc against DLC coated ball) under constant sliding velocity and constant sliding distance with four different loads (2, 5, 10 and 20 N) that results in maximum contact pressure below and higher than the maximum shear stress of the bearing steel. The wear coefficient was calculated using Archard’s equation based on the experimental results. It was found that the DLC coating may result in significant reduction, reaching 93.5%, in weight loss and 83% in COF at low contact pressure (less than the maximum shear stress). However, at high contact pressure (equals to or higher than the maximum shear stress) the weight loss and the COF for the DLC coating are higher than those of the bearing steel. This behavior indicates that the DLC coated pair may not be suitable at high loads. The wear coefficient is calculated for each testing condition and it is found to be affected by the applied load. The average wear coefficient for the DLC coating is provided which can be used with the Archared wear model to predict the wear rate within the range of the parameters used in this study.

Establishment of a new horizontal casting device and evaluation system for characterizing the homogeneity of food soft matter solution

A non-destructive dynamic solution casting device with in-situ roundness calculation for evaluating the homogeneity of food soft matter solutions is designed. The Charge-Coupled Devices (CCD) camera takes pictures of solution casting while the roundness is calculated by image software. Homogeneous single-component solutions were casting on a horizontal casting disc. The optimal combination of device hardware was obtained as the overflow hole diameter of 4 mm, overflow hole depth of 2 mm, injection tube diameter of 2 mm and injection height of 8 mm. The volume of sample solution was determined as 50 mL, and the relative roundness error of casting solution could be controlled below 0.25% when casting on a 304 stainless steel disc polished by 7000 Cw sandpaper. Finally, solutions with different viscosities must be casting with casting tubes of different diameters was proved. This work provides fundamental information for future analyses of the compatibility of food soft matter solutions.

Sliding electrical contact properties of highly oriented copper fiber brush

Metal fiber brush is a new electrical brush that has a promising application in high current density and non-lubricating conditions owing to its unique structure. The copper fiber brush comprised of highly oriented and uniformly distributed fibers was prepared by the knitting method with a packing fraction of 20%. The influence of current on the sliding electrical contact properties of the copper fiber brush as sliding against the steel disc was investigated. The worn surfaces of the copper fiber brushes and the steel discs were characterized to reveal the involved wear mechanisms. The results show that the static contact resistance decreases significantly from 55 to 18 mΩ with the gradual increase of contact force from 1 to 8 N, which is attributed to the elastic contact of multiple fibers and good compressive performance. The sliding contact resistance and electrical noise decrease with the increase of current, which is attributed to the micro-welding of contact spots induced by an electric arc. The wear rate of copper fiber brush increases significantly from 1.2 × 10−5 to 5.7 × 10−5 mm3/N·m with the increase of current from 0 to 8 A. The electrical wear caused by arc erosion becomes the dominant wear mechanism, which is more profound than mechanical wear under high currents.

Effects of Operating Conditions and Pit Area Ratio on the Coefficient of Friction of Textured Assemblies in Lubricated Reciprocating Sliding.

The experiment was carried out in a reciprocating lubricated conformal sliding contact between steel discs of the same hardness. The effects of disc surface texturing on the friction coefficient at various operating conditions (temperature, normal load, and frequency of oscillations) were studied. Under various conditions, surface texturing caused friction reductions of sliding pairs. The largest reduction was 4.6 times at a lower temperature and 2.5 times at a higher temperature. The effect of the pit area ratio on the friction reduction was visible at a higher temperature. The highest dimple density of 25% corresponded to a lower coefficient of friction than the smallest density of 9%. The sliding pair with a dimple density of 17% led to large variation of the friction force. At lower temperatures, the coefficients of friction were lower compared to tests at higher temperatures.

Tribological characteristics of polymer composites based on polytetrafluoroethylene and UVIS-AK-P carbon fibers under loading

Experimental and computational results of tribotechnical tests of polymer composites based on polytetrafluoroethylene and UVIS-AK-P discrete carbon fibers are presented. The PV factor is determined in the dry friction mode at a sliding speed of 0,2 m/s. Using the "steel disk — polymer disk" mathematical friction model, the maximum load was determined taking into account the allowable temperature of 120 °С for the friction surfaces of the materials under study. Keywords: polytetrafluoroethylene, wear resistance, friction coefficient, wear rate, carbon fiber. ppavlina@yandex.ru, markovamusya@mail.ru, roman_tikhon@mail.ru

Effects of Ti microalloying on the microstructure and mechanical properties of acicular ferrite casting steel for high-speed railway brake discs

Owing to the continuous interest on high-speed railway trains, research on the brake disc made of ferritic cast steel with high strength and toughness, and the manufacturability of complicated cooling fins has been conducted. In acicular ferrite, Ti is a major element; however, studies on the effect of Ti composition on the mechanical and impact properties are limited to a Ti content of up to 0.05 wt%. In this study, the microstructure and mechanical properties of high-speed railway brake disc steel material with 0–0.12 wt% Ti were investigated. The specimens were subjected to the same quenching–tempering heat treatment, in which acicular ferrite formation was observed by optical microscopy, scanning electron microscopy, electron backscatter diffraction (EBSD), electron probe microanalyzer, and transmission electron microscopy. Ferrite blocks, such as acicular ferrite, granular bainite, bainitic ferrite, and polygonal ferrite, were characterized in detail and quantitatively analyzed by EBSD. For different Ti contents, ferrites of various morphologies were noted. Moreover, the types of precipitates were determined to be cementite, Cr-rich carbide, V-rich carbide, and Ti-rich carbide. The highest hardness, impact toughness, and strength were measured with the addition of 0.06 wt% Ti. The crack propagation mode in the impact specimen was observed using fracture surface analysis. In addition, the relationship between the microstructure and mechanical properties, such as strength, toughness, and hardness, was discussed based on the alloying Ti content. In this study, the effect of acicular ferrite and precipitates on toughness in ferrite casting steel was confirmed, and the optimal Ti content was confirmed.

Understanding the Role of Directional Texture in Tribofilm Evolution

Abstract This paper reports a study of the evolution of directional texture and its role in the manipulation of tribofilm layers under boundary lubrication (BL). The use of surface protective tribofilms/lubricant chemistries along with the use of textured surfaces has gained significant attention as an effective BL strategy to provide advanced lubrication. However, the evolution of surface texture in the direction of motion under continuous asperity-to-asperity contact remains unexplored, especially in correlation with the tribofilm properties on textured surfaces. Mechanical polishing using SiC abrasive paper was used to generate directional and concentric surface texture on 52100 steel discs. Tribological tests of varying time durations were performed using MoS2-based lubricant to systematically study the evolution of texture and tribofilm using a pin-on-disc rotational setup. A laser microscope was used for areal texture characterization while tribofilm was characterized using SEM/EDS, Raman, and FIB/TEM. The results show that directional texture manipulates the early onset and tribo-chemical reactions and the delivery of lubricant tribofilm on the asperities during the evolution process.

The Effect of the Displacement Amplitude on the Fretting Wear of GCr15 Steel with a TiC Coating.

In the present paper, the effect of mechanical ball milling time on the fretting wear of GCr15 steel balls at different displacement amplitudes is investigated. TiC powder coating was fabricated on the surface of GCr15 steel balls using various process times, and the fretting wear tests were conducted on an AISI 52100 steel disk with the applied force of 80 N. Additionally, various displacement amplitudes (10 μm, 20 μm, and 60 μm) were selected. Specimen attributes and wear scars were characterized using an inverted metallographic microscope, a microhardness tester, an X-ray diffractometry analyzer, a white light interferometer, and a scanning electron microscope. The results showed that thick and continuous coatings could be obtained at the milling time of 18 h. The specimens processed for a longer milling time demonstrated better fretting wear resistance, which we attribute to higher microhardness of the surface layer. The coefficient of friction and wear volume of specimens at each different displacement amplitude significantly decreased with increasing milling time. As the displacement amplitude increased, the three fretting states were: partial slip coordinated by elastic deformation; partial slip state coordinated by plastic deformation; and gross slip condition. Our observations indicate that mechanical ball milling could be an efficient approach to improve the fretting wear resistance of GCr15 steel balls.