Chromium Steel Ball Research Articles

High-temperature dry sliding wear behavior of additively manufactured austenitic stainless steel (316L)

Austenitic steels are commonly used in aero-engine components owing to their higher thermal resistance to wear and corrosion. This study investigates the high-temperature dry sliding wear behavior of direct metal laser-sintered (DMLS) austenitic stainless steel (SS 316L) up to 400°C. A dry sliding reciprocating wear test conducted on a high-frequency tribometer with a ball-on-flat setup. High-hardness chrome steel (900 HV0.5) and alumina (1165 HV0.5) balls of 6 mm diameter were used as the steel and ceramic counterbodies against 316L specimen (320 ± 5 HV0.5). When tested against the chrome steel, the initial average coefficient of friction (CoF) decreased to a lower value (0.45) during the initial running-in period. However, with rising temperatures, the CoF also increased, stabilizing at 0.6 under steady-state conditions. A similar CoF pattern was observed in experiments with the alumina counterbody. Wear resistance declined at 100°C, followed by an increase at 200°C due to the development of an oxide glaze on the surface. Subsequently, wear resistance decreased as the temperature continued to rise. Up to 200°C , the wear mechanism was characterized by a combination of abrasive and oxide debris wear, transitioning to adhesive wear with plastic deformation at higher temperatures (400°C). Diffraction (XRD) analysis revealed the formation of oxide layers and martensite phase at higher temperatures, contributing to the observed improved wear resistance around 200°C . However, these oxide layers were progressively removed from the surface at 400°C, leading to an increased wear. The measured wear rates are two times lower, up to 200°C, compared to the reported values for conventional 316L due to the fine microstructure and higher hardness of DMLS SS 316L. This results in potentially rendering it suitable for applications where high-temperature (up to 200°C) wear-resistant SS is needed. This study provides further insights into the importance of post-treatment of DMLS parts for temperature beyond 400°C.

Sliding wear behaviour of austempered ductile iron, boron steel and AISI 1045 steel of similar hardness: effect of microstructure, yield strength, and strain hardening

ABSTRACT A study on dry sliding wear investigated four alloys: fully austenitized ADI (F-ADI), intercritically austenitized austempered ductile iron (I-ADI), hardened and tempered Boron steel (B-Steel), and hardened and tempered AISI 1045 steel (EN-Steel). Despite their similar hardness levels, these alloys differ in composition and microstructure. Testing was conducted using a Ball-On-Disc setup (ASTM G99-05) with a chrome steel ball, maintaining a constant sliding speed of 0.6 m/s and applying loads between 20 and 80 N. This study aimed to understand the influence of yield strength (σy ), strain hardening coefficient (n), and microstructure on sliding wear under uniform hardness conditions. The findings indicated a strong connection between sliding wear resistance, strain hardening coefficient, toughness, and yield strength. Wear mechanisms varied slightly among materials; F-ADI and I-ADI exhibited deformed layers with increased hardness and oxide formation, while B-Steel and EN-Steel showed micro-cutting and micro-ploughing. F-ADI's high-carbon austenite film and I-ADI's proeutectoid ferrite contributed to improved wear performance. The hardness of the deformation layer on FADI and I-ADI's worn surfaces highlighted the benefits of strain hardening in dry sliding wear.

Characterisation of thin α-Al2O3 tribo-coating deposited by low-power gas tunnel plasma spray

This study used a unique, low-power (2.8 kW) gas tunnel plasma spray and γ-Al2O3 feedstock powder to deposit a thin Al2O3 coating (<2 µm) on mild steel substrate. By optimising the plasma gas flow rate, powder feed rate, spraying time, and distance, a dense and homogeneous Al2O3 coating was obtained at a very high deposition rate (150 nm/s). During plasma coating, the high energy density plasma transforms the γ-Al2O3 powder into a highly crystalline α-Al2O3 as the predominant microstructure of the coating. The performance of the Al2O3 coating on mild steel was then evaluated preliminary using a linear sliding wear test against a chrome-steel ball, with the results indicating an 18–26% reduction in wear when compared to the uncoated substrate.

Formulation and tribological performance of engine oil blended with various non‐edible vegetable oils

AbstractThis present study formulated eco‐friendly lubricants by combining non‐edible vegetable oils with a mineral oil and investigated their efficacy on the friction and wear characteristics of four AISI 52100 chrome steel balls. Multiple formulations containing varying combinations of 0 to 100 vol% of a mineral oil SAE 15W40 (S100), castor oil (C100), and jatropha oil (J100) were prepared using the sonification technique in an ultrasonic homogeniser. A fourier transform spectrometer (FTIR) was then used to investigate the molecular vibrations of each formulation. A tribological test was also performed with a four‐ball tribometer according to ASTM D4172‐94 engineering standards. Finally, a scanning electron microscope (SEM) equipped with an energy dispersive X‐ray spectroscope (EDX) was used to examine surface morphologies. The 80% S100, 10% C100, and 10% J100 (S80C10J10) formulation provided excellent tribological performance as it contained fatty acids composed of carbohydrates and carbonyl groups, particularly polysaccharides and glycerols.

Effect of load, sliding frequency, and temperature on tribological properties of graphene nanoplatelets coated carbon fiber reinforced polymer composites

The present work primarily focuses on the thermo-mechanical and physical properties of polymer composites. The effects of normal load, sliding frequency, and temperature on the reciprocating sliding performance of Carbon fiber (CF) segments are evaluated. These CF segments are coated with graphene nanoplatelets (GNPs), and carbon fiber-reinforced polymer (epoxy) composites (CFRPs). Experiments are carried out at three different normal loads (55 N, 75 N, and 95 N), sliding frequency (8 Hz, 12 Hz, and 16 Hz), and temperature (25°C, 40°C, and 60°C). The experiments are conducted for 20 min with a constant stroke length of 1.5 mm against a 62 HRC hardened chrome steel ball as a counter surface material. Optical microscopy and Scanning electron microscope (SEM) have been used to examine the worn surfaces. In addition, an artificial neural network (ANN) is applied to model the coefficient of friction on the basis of different parameters. It has been observed that adding GNPs to carbon fiber strands improves the strand’s bonding tendency with the matrix, resulting in an increase in wear resistance. With the addition of GNPs on carbon fiber strands, the specific wear rate decreased by 32.39%, respectively, while the thermal conductivity increased by 47.95%. The coefficient of friction increases with the normal load up to 75 N and then drops. This is due to fiber fragments and friction film at high loads. As the sliding frequency and temperature increase, the friction coefficient gets reduced. It has been found that the ANN model is able to predict the coefficient of friction with high accuracy.

A roller scanning type prostate palpation sensor system using a cantilever beam type force measurement.

Palpation has been used for centuries in medicine as a screening and diagnosis modality for a number of pathological conditions. However, this technique is subjective since palpation sensitivity depends on the skill and experience of a medical examiner. An objective approach to acquire quantitative tactile information is needed. A roller scanning type palpation sensor system consisting of an x-axis linear slider and a palpation probe for detecting lumps in a soft object such as the prostate tissue is proposed and fabricated in this study. By translating the slider and changing the palpation angle of the probe, a chrome steel ball which was the contact component indented and scanned the surface of soft silicone phantoms embedded with hard lumps. Lumps were detected by measuring reaction force waveform fluctuations. Fundamental characteristics of the proposed sensor system were validated by comparison with the ground truth load cell output and showed a strong linear correlation with r2=0.9985. On silicone samples with hard lumps, the system was able to detect lumps of various sizes embedded at the depth of 5mm. From the results, the proposed sensor system holds potential for tissue characterization.

Scuffing resistance of polyalphaolefin (PAO)-based nanolubricants with oleic acid (OA) and iron oxide nanoparticles

The development and application of nanolubricants has shown great potential to reduce friction and wear, especially in the automotive field for systems operating under boundary and mixed lubrication regimes. The search for additives that do not attack the environment has motivated the use of nanoparticles, especially metallic oxides, because of their characteristics such as low toxicity, high surface area, high wettability, and easy dispersion. The objective of this work was to evaluate the addition of iron oxide nanoparticles as additive to pure PAO 8 base oil. The nanoparticle action mechanisms, lubrication efficiency, friction, and wear rates were evaluated. The concentration of nanoparticles in the oil and the addition of oleic acid as a dispersing agent were varied. The synthesis of the nanoparticles was done by aqueous precipitation; characterization was performed by XRD, FTIR, Raman and SEM analyses. Tribological tests were performed in a reciprocating tribometer (Plint TE 67) using AISI 1020 prismatic samples and AISI 52100 chrome steel balls of 5 mm diameter. Test conditions resulted in boundary lubrication regime, for a starved contact with limited lubricant supply (0.5 µL). Concentrations of 0.4 and 1.6 wt% of nanoparticles were added to the base oil with and without the presence of oleic acid. Friction coefficient was not sensitive to the presence of nanoparticles, with statistically similar values for all the fluids tested. On the other hand, the presence of nanoparticles increased scuffing resistance and reduced wear rates. The lubricants with nanoparticles proved able to withstand relatively high loads, keeping the friction coefficient low for longer test durations due to the formation of protective tribolayers between the worn surfaces. The addition of nanoparticles reduced wear rates by around 27% when compared to tests using pure PAO 8.

Simultaneous effect of flake powder methodology and SiC addition on the density and hardness of Al matrix

In the present work, Flake Powder Methodology(FPM) followed by cold press sintering has been adopted to improve the density and hardness of the Aluminium based metal matrix composite. The effect of hard ceramic particles of SiC (1 vol%) on the Al matrix has been also studied. Three powders Al (procured), Al (FPM), and Al_SiC_1 vol% (FPM) were taken. Green samples using three respective powders were then compacted at 867 MPa and sintered in an inert atmosphere at a temperature of 530 °C for 2 Hr. The particle size of Al was observed to be reduced by adopting FPM. Al sample prepared following FPM shows an improvement of 14.83% and 157.2% in density and hardness respectively compared to the Al sample prepared from procured powder. However, SiC addition by 1 vol% decreased the relative density by 2.12% and improved the hardness by 30.63% compared Al(FPM) sample. Tribological tests has been performed in a ball on disc reciprocating microtribometer at 10 N load with a 6 mm chrome steel ball with the sliding speed of 0.5 cm/s and 5 cm/s. Addition of SiC into Al matrix increased COF of the composite and lowered the wear rate. The COF and wear rate were also increased with increases in sliding speed.

Tribological and mechanical properties of cellulose/PMMA composite

Cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs) extracted from rice stalks were added to poly-methyl methacrylate (PMMA) with weight ratios of 0.1–1.0 wt%. The tribological and mechanical properties of the resulting composite materials were evaluated and compared. The addition of CNCs and CNFs reduced the wear volume by around 72–90% compared to pure PMMA samples in ball-on-disk wear tests performed against a chrome steel ball counter body. The CNC and CNF reinforcements also effectively improved flow stress under static and dynamic deformation conditions. Furthermore, the flow stress enhancement increased with an increasing CNC/CNF addition for both composite materials. For a constant strain and strain rate, the maximum enhancement effect was observed in the samples reinforced with CNFs. Overall, the CNF/PMMA showed a better tribological and mechanical performance than the CNC/PMMA. In addition, the CNFs had a longer length and higher aspect ratio than CNCs, which led to a more effective mechanical entanglement effect with the PMMA matrix. This physical entanglement improved the structural integrity of the composites. The CNC reinforcement (CNC percentage from 0% to 1.0 wt.%) also enhanced an effective improvement of about 35%∼45% in yield stress and ultimate strength under dynamic deformation conditions and static deformation conditions. Furthermore, the CNF reinforcement (CNF percentage from 0% to 1 wt%) also enhanced an effective improvement of about double yield stress and ultimate strength under dynamic deformation conditions and static deformation conditions.

Analysis of the stress distribution in a laminar direct simple shear device and implications for test data interpretation

Direct simple shear (DSS) testing allows observation of load-deformation response under rotation of the major principal stress plane, which is descriptive of many actual field problems. While the simplicity of the test configuration makes its use popular in research and industry, key uncertainties still remain regarding the interpretation of the laboratory data. This study uses laboratory validated discrete element method (DEM) models to examine the stress transmission in laminar-type direct simple shear devices under drained constant effective stress conditions. The DEM models (comprised of spheres) closely replicate physical specimens of precision chrome steel ball bearings for which the properties (e.g., shape, surface friction, and stiffness) were measured directly. The DEM models were also validated using experimental tests, so that conclusions regarding the system response can be derived with confidence from the available DEM data. The testing program included both loose and dense specimens, allowing for a comparison of the influence of density on stress state which has not been examined in previous simple shear DEM studies. Differences were observed between vertical effective stresses and shear stresses derived from boundary measurements (as commonly carried out in experimental programs) and those derived from force measurements within the DEM specimens. The failure state of the material in simple shear was also examined through Mohr’s circles of stress. The evolution of stresses on both the horizontally and vertically oriented planes were considered so that established methods of direct simple shear interpretation could be critically assessed. For the loose specimens, the angle of shearing resistance can be confidently estimated considering the maximum shear stress acting on the horizontal plane, which is easily inferred from measurements of the shear force during the physical test. This was true considering both internal and boundary calculated stresses. This approach, however, is inaccurate for the dense specimens. Analysis of the particle-scale kinematics of the response illustrates that the deformation field within the central portion of the specimen is in simple shear, although the magnitude of this shearing was significantly larger than what was measured on the boundary. This study and the conclusions derived focus on smooth spherical particle specimens; the objective was to examine the stress distribution within DSS devices and the implications for test interpretation using DEM models that more closely matched the physical laboratory specimens tested than in previous studies. When considered alongside the existing studies, the findings show that there is no broad conclusion that can be applied for all materials and all conditions in simple shear and that interpretation should be carefully tied to the physical conditions simulated.

Designing a Bioinspired Surface for Improved Wear Resistance and Friction Reduction

Abstract This study used 2-photon three-dimensional lithographic printing and replica molding to fabricate a micro-texture based on the Ocellated Skink. The fabricated surface texture was studied for friction and wear behavior using linear reciprocating tribological tests with a chrome steel ball counterface under various loading conditions and compared with samples fabricated with the same methods without a surface texture. The texture was found to decrease friction at low loads and provide steady friction under all loading conditions. The textured samples also decreased the average wear track width up to 61%. Wear was reduced on surfaces by the texture through the controlled formation of microcracking, which both reduced the amount of debris built up on samples and effectively reduced the worn area.

The Roles of Alloy Elements on Self-Lubrication of Anodic Al2O3/MoS2 Composite Films on Al Alloys

Aluminum alloys have good specific strength, corrosion resistance, and recyclability, so they are attracting attention from the automobile industry as a structural material to replace steel materials. Since aluminum alloys are prone to adhesive wear, resulting in poor tribological performance, it is necessary to improve the wear resistance by appropriate surface modification. It is known that filling some solid lubricants, such as MoS2 or PTFE, inside the anodic porous films is an effective method to improve the wear resistance of aluminum alloys in industry. However, few studies have been conducted on the alloy elements in aluminum alloys containing Si and Cu, especially casting alloys. The intermetallic compounds such as Si and CuAl2 contained in aluminum alloys usually cause defects inside the anodic films, which may affect the wear resistance of the anodic films. In this study, our purpose is to fabricate self-lubricating anodic Al2O3/MoS2 composite films on various aluminum materials by successive anodization and electrodeposition, to investigate the effects of alloy elements in aluminum alloys on the filling of MoS2 and wear resistance.Three kinds of commercial aluminum alloy sheets (A1100: 99.0% Al, A2017: Al-3.85% Cu, A4045: Al-9.85% Si) and an Al-12Si-5Cu casting alloy for automotive engine parts. Anodizing was performed using a sulfuric acid-based solution in constant current mode. After anodizing, anodic electrodeposition was performed in an ammonium tetrathiomolybdate solution, to incorporate molybdenum disulphide (MoS2) into the anodic films. The surface and cross section of the prepared sample were observed by FE-SEM to investigate the influence of intermetallic compounds in aluminum alloy on MoS2 anodic electrodeposition. GD-OES was used to examine the composition depth profiles inside the anodic Al2O3/MoS2 films. XPS was used to investigate the composition and chemical bond state of the formed MoS2. Furthermore, in order to evaluate the influence of the substrate on the wear resistance, the friction coefficient of various samples was measured using a reciprocating wear tester (SRV-4; 20 N, 1.0 mm, 20 Hz). The counterpart material was a high carbon chromium steel ball (100 CR6-DIN) of φ12.7 mm.Fig.1 a-b shows the results of GD-OES measurement of composition depth profiles within the self-lubricating anodic Al2O3/MoS2 composite films formed on (a) pure Al (A1100) and (b) Al-Si-Cu casting alloy. By making only Mo intensity the same measurement condition, it was possible to compare the amount of MoS2 filled inside the anodized films on pure Al and Al-Si-Cu casting alloy. Strong Mo peaks were found on the surface of both pure Al and Al-Si-Cu casting alloy specimens. The, with weak intensity inside the alumina film. Whereas the Mo and 0.1concentrate and Al-Si-Cu casting alloy. In case of pure Al, distribution of Mo mainly accumulates on the surface with only weak intensity inside the alumina film, and the intensity of Mo becomes almost stable toward the inside of the film. Whereas in case of the Al-Si-Cu casting alloy, the intensity Mo is much higher than that of pure Al, with a gradual distribution across the composite films, indicating that more Mo is deposited inside the anodic alumina film. The enhancement of Mo amount is ascribed to the presence of MoS2 in the defects of the anodic alumina film formed by the intermetallic compound (AlCu) contained in the Al-Si-Cu casting alloy, which can also be confirmed by cross-sectional observation by FE-SEM..Fig.1 c shows dynamic friction coefficient vs. number of reciprocating slides of self-lubricating anodic Al2O3/MoS2 composite films. Both the pure Al and the Al-Si-Cu casting alloy maintained a low friction coefficient at the beginning and then showed a sharp rise at a certain point. It is considered that the self-lubricating film was completely worn and reached the base metal at the point where the friction coefficient sharply increased. It can be confirmed that the number of sliding times to reach the base metal is about 26000 times with pure Al and about 36000 times with the Al-Si-Cu casting alloy, and that the Al-Si-Cu casting alloy has a longer coating life. In addition, the friction coefficient of the self-lubricating films decreased from 0.15-0.25 for pure Al to around 0.1for the Al-Si-Cu casting alloy, thus indicating the excellent lubricating effect of MoS2, which can be attributed to the increase of the filling amount of MoS2 inside the anodic film, as shown in the results of GD-OES (Fig.1a-b). Figure 1

Improved tribological behavior of lubricating oil dispersed with hybrid nanoparticles of functionalized carbon spheres and graphene nano platelets

A novel synthesis method of Functionalized Carbon Spheres (FCS) coated with Graphene nanoplatelets (GNP) using a simple sonication technique is reported. The FCS/GNP hybrid nanoparticles were found to be effectively improving the tribological characteristics of lubricating oils. For the synthesis of FCS, Carbon Spheres (CS) synthesized via non-catalytic chemical vapor deposition was functionalized using nitric acid. The hybrid nanoparticles were characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Raman spectroscopy. The tribological behavior of CASTROL-20 W 40 engine oil dispersed with different concentrations of FCS and GNP using ultrasonication was investigated using a four-ball tester. The tribological behavior of FCS and GNP were investigated separately to compare the tribological performance of the FCS/GNP hybrid nanoparticles. The neat oil dispersed with 0.275 wt% of FCS/GNP hybrid nanoparticles in 10:1 ratio shows excellent dispersion and stability for 30 days without the addition of any surfactant. The results indicate that the addition of these hybrid nanoparticles causes a remarkable reduction (~18%) in the Coefficient of Friction (COF) of the neat oil. The optical image of wear scar on the ball immersed in neat oil shows a significant reduction in the Wear Scar Diameter from 425.6 µm to 390.0 µm with the addition of hybrid nanoparticles. The Raman mapping of the wear scar on chromium steel ball reveals that the FCS/GNP hybrid nanoparticles remain unseparated after the tribology test.

Defining the role of ‘zero wear volume’ in percussive impact

This work defines the previously undetermined contribution of the ‘zero wear’ volume, that is geometry change due to material compression that occurs before other mechanisms that cause change through actual material loss are initiated during to repetitive impact. Five metal alloys widely used in engineering applications, each with a different bulk hardness, were the subjects of the experiments. Using a reciprocating hammer type impact wear test apparatus, flat coupon type specimens were subjected to repetitive impact from a chrome steel ball acting normal to the surface. 36,000 impacts were applied at a nominal rate of 10 impacts per second, each with an impact energy of 0.23J and an impact force of 3.5 kN. The impact wear crater on selected worn specimens was examined using a 3D non-contact profilometer. Scanning electron microscopy techniques were used to further examine the damage on the specimens. The main damage mechanism was plastic deformation and surface fatigue due to spalling. Microcracks and adhered wear debris were noted on the specimens, but with no evidence of delamination, while subsurface examination showed no possible microcracks under the impacted surface and only surface pitting could be observed from subsurface examination. Analysis of the wear scars suggests that zero wear volume is the main contributor to the total volume ‘loss’ for all materials, and, for specific materials, plastic flow volume and bulk hardness could be a significant parameter in characterising zero-wear volume and crater depth.

Evaluation of Tribological Performance of Jatropha Oil Modified With Molybdenum Disulphide Micro-Particles for Steel–Steel Contacts

Abstract Crude oil reserves are sapping with time, therefore researchers have considerably shifted their focus to bio-lubricants which can be surrogated for petroleum-based lubricants. The objective of the present research is to cater an idea to the researchers about the lubricating potentials of Jatropha oil (JO). The study was performed using reciprocating friction monitor (RFM) machine having ball-on-flat arrangement with 52100 chromium steel ball and EN-31 steel as a tribo-pair. The experiments were conducted at three different loads at a temperature of 40 °C. JO was mixed with glycerol (G) and different percentages of molybdenum disulphide (0.5%, 1%, 2%, and 3%) micro-particles to prepare a lubricant. The friction and wear of the tribo-pair was assessed in the presence of these mixtures. The results revealed that MoS2 micro-particles were effective in reducing both friction and wear, with minimum friction recorded at 2% MoS2 concentration. The coefficient of friction (COF) was reduced by 18–52% with the addition of MoS2 as compared to the base JO. The results showed that JO has better lubrication ability as compared to the commercial lubricant SAE 10W/30. The experimental results were substantiated by examinations of tribo-pairs on scanning electron microscope, optical microscope, and optical three-dimensional profilometer. The results were found to be in close agreement with each other. It was concluded that the blend (80% JO + 20% G + 2% MoS2) is a strong candidate that can be used in the place of mineral oils as a lubricant.

Friction and Wear Characterization of Spark Plasma Sintered Hybrid Aluminum Composite Under Different Sliding Conditions

Abstract Friction and wear behaviors of hybrid aluminum matrix self-lubricating nanocomposite, containing varying amount of nano-aluminum oxide (Al2O3) and graphene nanoplatelet (GNP) particles were investigated under dry and boundary lubrication sliding conditions. All the specimens were prepared by ultrasonic probe mixing followed by high-energy mechanical ball milling and spark plasma sintering fabrication route. The objective of this present study is to determine the tribological behavior of GNP as nanoreinforcement under dry and wet lubricating conditions. The wear test was carried out at room temperature on a ball-on-disc reciprocating tribometer with a contact load of 5 N, a frequency of 30 Hz, a stroke of 2 mm, and a sliding distance of 120 m. The chromium-plated chrome steel ball is used as the counter body for tribo-testing. From the results, it has been observed that GNP, as the solid lubricant reinforcement, reduces the friction by 25.33% and 68.14% under dry and wet lubricating conditions, respectively, for the hybrid composite. Reduction in wear volume by 91.15% and 90.50% is observed under dry and wet lubricating conditions, respectively, for the hybrid composite in comparison to the base eutectic Al–Si alloy. The reduction in the coefficient of friction and wear volume for the hybrid composite is attributed to the multilayer two-dimensional GNP nanoparticles that cause easy shearing by forming a conformal protective film layer on the sliding interface. Ultra-mild to severe wear regime was obtained for different composition samples including base composition to hybrid composition.

Experimental study on the coefficient of restitution of grain against block interfaces for natural and engineered materials

The coefficient of restitution (COR) is an important input parameter in the numerical simulation of granular flows, as it governs the travel distance, the lateral spreading, and the design of barriers. In this study, a new custom-built micromechanical impact loading apparatus is presented along with impact experiments on engineered and natural materials. The COR and energy loss of various grains and base block combinations are studied, including fairly regular-shaped Leighton Buzzard sand (LBS) grains as a natural soil and granite or rubber as base blocks, apart from the use of engineered materials for the grains (chrome steel balls, glass balls) and blocks (stainless steel, brass). The repeatability of the new micromechanical impact loading apparatus was checked by impacting chrome steel balls on stainless steel block. In all the test combinations, the higher and lower values of the COR are found for granite block (ranging between 0.75 and 0.95) and rubber block (ranging between 0.37 and 0.44) combinations, respectively. For the tested grain–block combinations, lower values of COR were observed for impacts between materials of low values of composite Young’s modulus. However, within the narrow range of composite surface roughness of the tested grain–block interfaces no particular trend was observed in the COR values. Compared to glass balls and chrome steel balls, greater scatter in the COR values is observed for natural sand grains. This is due to the variation of the elastic and morphological characteristics among individual LBS grains.

Development of the Backside Loading Inductive Tactile Force Sensor Using the Flip-Chip Bonding of CMOS Sensing Chip

This study presents a backside loading design inductive tactile sensor with the monolithic integration of thermometer. Based on the commercially available standard complementary metal-oxide-semiconductor (CMOS) process (the TSMC $0.35\mu \text{m}$ 2P4M CMOS process) and the in-house post CMOS processes, the sensing chip is designed and implemented. The electrical connection is further achieved by using the flip-chip bonding process, and hence the breakage of bonding wires by the tactile load can be avoided. The CMOS sensing chip consists of the magnetic sensing coil and the polysilicon RTD (resistive thermal detector). Moreover, a cavity is defined on the backside (silicon substrate) of CMOS chip to act as a mold for the polymer filler as well as the housing for the chrome steel ball contact interface. The tactile force will cause the polymer deformation and chrome steel ball displacement, and further lead to the magnetic flux change on the sensing coil. Thus, the tactile force is detected by the inductance variation of magnetic sensing coil on the CMOS chip. Moreover, the temperature variation is detected by the resistance change of RTD thermometer, and the in-situ temperature monitoring during tactile loading is achieved. The force response of the proposed tactile sensor and the temperature response of the thermometer have been characterized. The influence of temperature variation on the tactile sensor has also been calibrated. Moreover, the characteristics of the thermometer on sensing chip at different contact conditions are also investigated.

Effect of load on the friction and wear properties of aluminum hybrid composite/chromium plated chrome steel tribopair under boundary lubrication conditions

Friction and wear loss are the main reason that contribute to the failure in the IC engine components. This emerges the demand for the light weight, low friction and wear resistant material to enhance the efficiency and to reduce the emission problem in the IC engine components. In this concern, tribological test are performed on the hybrid aluminium matrix composites (Al–Si/Al2O3/GNP) composite fabricated using non-conventional rapid Spark Plasma Sintering (SPS) against chromium plated chrome steel ball under boundary lubrication conditions at room temperature using Ball-on-disc tribometer configuration. Friction & wear studies are conducted under high loading conditions ranging 100 N–300 N with 120 m sliding distance, 30 Hz frequency, 2 mm stroke length. From the study, it is reported that coefficient of friction (COF) as well as the wear significantly reduces; attributed to SAE20W50 engine oil lubricant with GNP Nano particles used as the secondary reinforcement (solid lubricant) in the hybrid composite. Ultra-mild adhesion and abrasion are the dominating wear mechanisms for the hybrid composite samples.

Effect of load on the tribological behavior of self-lubricating hybrid aluminum composite under dry sliding conditions

Self-lubricating composites are the new development of next generation. Hence the objective of this study is to determine how Aluminum Oxide (Al2O3) and Graphene Nano Platelets (GNP) nanomaterial reinforcements could be used to enhance the tribological properties of Eutectic Aluminum-Silicon matrix material. Friction and wear studies of self-lubricating novel Aluminum-Silicon/Aluminum Oxide/ Graphene Nano Platelets (Al-Si/Al2O3/GNP) hybrid composite with varying amount of Graphene Nano Platelets (GNP); synthesized using Spark Plasma Sintering (SPS) has been studied in this research paper. The tribo-testing was done on the ball-on-disc configuration under dry sliding conditions. Effect of the solid self-lubricating composite was studied under room temperature at high load varying from 50N-300N with chrome plated chrome steel ball as counter-body and other parameters i.e. frequency, stroke, sliding distance remained constant throughout the experimentation. The results of the tribo tests indicates that the novel hybrid composite fabricated using both reinforcement’s nanomaterial exhibit excellent antifriction as well as antiwear. Results showed that best tribological properties were achieved for composite sample having 4 wt% of GNP. Reduction in friction and wear of the hybrid composite was reported in the range 4.04%–12.47% and 61.87%–82.84% respectively, compared to the base matrix material (Eutectic Al-Si alloy). It was observed that the seizure phenomenon which occurs with monolithic Aluminum-Silicon (Al-Si) alloy did not occur with hybrid composite. The surface morphology and wear surface analysis were done by using Optical Microscopy , Scanning Electron Microscopy , Electron Dispersion Spectroscopy and 3D Surface Profilometer. The results of this research highlights the novel self-lubricating hybrid composite which can be used in manufacturing of various mechanical components applications.