Tribological behavior of UHMWPE in water lubrication: the effect of molding temperature

Purpose Ultra-high molecular weight polyethylene (UHMWPE) is adopted in water-lubricated bearings for its excellent performance. This paper aims to investigate the tribological properties of UHMWPE with a molecular weight of 10.2 million (g mol‐1) under different molding temperatures. Design/methodology/approach The UHMWPE samples were prepared by mold pressing under constant pressure and different molding temperatures (140°C, 160°C, 180°C, 200°C, 220°C). The friction and wear tests in water were conducted at the RTEC tribo-tester. Findings The friction coefficient and wear loss decreased first and rose later with the increasing molding temperature. The minimums of the friction coefficient and wear loss were found at the molding temperatures of 200°C. At low melting temperatures, the UHMWPE molecular chains could not unwrap thoroughly, leading to greater abrasive wear. On the other hand, high melting temperatures will cause the UHMWPE molecular chains to break up and decompose. The optimal molding temperatures for UHMWPE were found to be 200°C. Originality/value Findings are of great significance for the design of water-lubricated UHMWPE bearings.

Mechanical Properties of Bisacryl-, Composite-, and Ceramic-resin Restorative Materials

SUMMARY Objective: Resin-based materials used in restorative dentistry are introduced at a fast pace with limited knowledge about their properties. Comparing properties of these materials from different restorative categories is lacking but can help the clinician in material selection. This study aimed to compare mechanical properties and wear resistance of bis-acryl-, composite-, and ceramic-resin restorative materials. Methods and Materials: Bisacryl-resin (Bis-R, LuxaCrown, DMG), composite-resin (Com-R, Filtek Supreme Ultra, 3M Oral Care), and ceramic-resin (Cer-R, Enamic, VITA Zahnfabrik) specimens were prepared for mechanical tests: fracture toughness (FT) with and without initial thermomechanical loading using a mastication simulator, flexural strength (FS), and flexural modulus (FM), compressive strength (CS), and volumetric wear loss measurement. The datasets for FT and wear resistance were each analyzed using two-way ANOVA followed by pairwise comparisons or Tukey testing as appropriate. The datasets for FS, FM, and CS were analyzed using one-way ANOVA followed by the Tukey test. Results: Analysis of FS, FM, and CS showed significant differences between materials, with all pairwise comparisons between materials showing significance. Analysis of FT resulted in a significant interaction between the material and treatment, with analysis of wear loss showing a significant interaction between the material and the number of cycles. Conclusions: Cer-R demonstrated superior FT, CS, and wear resistance compared to Bis-R and Comp-R materials. Fracture toughness of Bis-R increased after thermomechanical loading.

Study of wear losses and frictional heat dissipation during dry sliding wear of ilmenite reinforced Al-alloy composite

In this investigation, ilmenite mineral reinforced Al–Si alloy matrix composite (AMC) has been developed. The wear behavior of the developed composites has been studied for their end application as break drum material to replace cast iron used in automobile industries. Ilmenite is one of the major sea beach mineral. AMC has been prepared through a low-cost stir-casting method in which 1 wt.% graphite (Gr)/tin (Sn) as a solid lubricant has been added during the fabrication of composites itself. The optical micrographs of AMC revealed uniform distribution of ilmenite particles throughout the matrix. The wear rate of the base LM30 alloy containing 17% Si and the developed composites has been studied at different normal loads at a constant velocity of 1.6 m.s−1. Optimized data revealed a significant wear rate reduction due to solid lubrication provided by Gr/Sn (∼32%). The wear rate of composites has been compared with traditional cast iron used in brake drums under similar experimental conditions. Composites exhibit nearly identical wear behavior throughout the test. The microstructural study of wear track and debris revealed that Sn and Gr used as solid lubricants played a vital role in reducing the wear loss of the prepared composites. A theoretical study of frictional heat generated during dry sliding and its dissipation has been done to establish the operative wear mechanism in the composites.

Wear and Morphological Analysis on Basalt/Sisal Hybrid Fiber Reinforced Poly lactic acid Composites

The investigation was undertaken to evaluate the wear behavior of basalt fiber and sisal fiber reinforced polylactic acid PLA composites. Basalt saline-treated chopped fiber and treated sisal chopped fiber were alloyed with polylactic acid and the samples were obtained using an injection mold in a twin-screw extruder. Three weight fraction samples were prepared, namely PBSi-1 (90% by weight polylactic acid, 5% by weight basalt and 5% by weight sisal), PBSi-2 (85% by weight polylactic acid, 7.5% by weight basalt and 7.5% by weight sisal) and PBSi-3 (80% by weight polylactic acid, 10% by weight basalt and 10% by weight sisal). The wear behavior of the prepared specimen were determined using a Pin-on-disc. The wear loss was measured at four different loads (10 N, 20 N, 30 N and 40 N) and four different sliding speeds (100 rpm, 150 rpm, 200 rpm and 250). The wear mechanism map was generated based on the wear regime nature using the Fuzzy Cluster C-means algorithm. The PBSi-3 composite showed a more mild wear regime than the severe and ultra-severe wear, due to the increase in the basalt and sisal fiber content within the composite that results in an increase of hardness and wear resistance. The predominant mechanism observed in the SEM image of PBSi-3 composite is ironing, which indicates the lesser wear occurrence in the composite.

Wear Based Lifetime Estimation of a Clutch Facing using Coupled Field Analysis

Repetitive use of the clutch, over a period of time, causes the friction material at the contact surfaces (clutch facing and flywheel/pressure plate) to wear, thus deteriorating its performance and usable life. The working life of a rigid clutch is the limiting factor when it comes to extracting maximum performance from a dual mass flywheel system, which is used in a lot of modern vehicles nowadays to lower fuel consumption and improve ride quality. In this study, we investigate the influence of different groove patterns on wear in rigid clutch facings and estimate their life using a comprehensive finite element model. The wear is calculated and analysed for five different groove patterns across two different inorganic materials, namely FTL180 and TF1600-MC2, using Archard’s Adhesive Wear Model. Coupled multi-physics elements are employed in the analysis to capture the effect of frictional heat generation on wear. We found that the Waffle pattern offered a decrease of 10.4% in volumetric wear loss, a 5.78% decrease in maximum wear thickness and an increase of 11.51% in the average working life is used in city like conditions with frequent engagements. This work sheds light on the impact of groove patterns on clutch facing wear and opens a new path for the design and development of more resilient rigid clutches.

Effect of TiB2 Content on Properties of Nickel-Coated Graphite Self-Lubricating Coating Prepared by Laser Cladding

To improve the anti-wear and friction-reducing properties of self-lubricating coatings, Ni60/Nickel-coated graphite/TiB2 composite coatings with different contents were prepared by laser cladding. The coating properties were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), energy spectrometer (EDS), electrochemical workstation, micro-Vickers hardness tester, and friction and wear tester. The results showed that with the increase in TiB2 content, the graphite morphology changed from spherical at 0 wt.% TiB2 content to a little black graphite alone at 14 wt.% TiB2 to irregular agglomerates at 22 wt.% TiB2. Furthermore, the hardness of the coatings increased with increasing TiB2 content, and the 63% Ni60 + 15% nickel-coated graphite + 22% TiB2 coating had the highest hardness. TiC and Cr7C3 were generated in the coatings with the addition of nickel-coated graphite, creating a dispersion reinforcement effect, so that the hardness of these coatings was higher than that of the 86% Ni60 + 0% nickel-coated graphite + 14% TiB2 coating without the addition of nickel-coated graphite. In addition, the 71% Ni60 + 15% Ni-coated graphite + 14% TiB2 coating had the lowest friction coefficient, wear loss, and wear volume, thus exhibiting excellent friction reduction and anti-wear properties. The 71% Ni60 + 15% nickel-coated graphite + 14% TiB2 coating had excellent corrosion resistance.

SLIDING FRICTION WEAR BEHAVIOUR OF SEASHELL PARTICULATE REINFORCED POLYMER MATRIX COMPOSITE – MODELING AND OPTIMIZATION THROUGH RSM AND GREY WOLF OPTIMIZER

In this work, the friction wear behaviour of seashell particles reinforced in thermoplastic polymer Nylon-6 is investigated.. Seashells were collected from the seashores, uniform size 75 µm is obtained using mechanical ball milling and vibrating sieve. Various proportions of seashells such as 12, 15 and 18% by weight are added to nylon-6 and the polymer composites wear performance in dry sliding is studied as per ASTM G99 standard, loss of material in wear, friction coefficient and interface temperature are optimized. For experiment design Response surface methodology (RSM) based Box-Behnken method (BBD) is adopted and multi-objective analysis is performed using desirability analysis. Observation shows that interface temperature is highly influenced by rotational speed (41.61%), % reinforcement of seashells influences the wear loss significantly (35.71%) and coefficient of friction is influenced greatly by rotational speed (41.48%)and % reinforcement of seashells (18.18%). A novel metaheuristic algorithm Grey wolf optimizer is used for constrained optimization, which shows that for 0.3 CoF and 25°C interface temperature as constraint wear loss is 35.77 microns for % reinforcement of seashell as 3.59, whereas for 0.3 CoF and 30°C interface temperature wear loss is 28.99 microns for a seashell reinforcement of 18%.

Tribological behavior of grooves textured thrust cylindrical roller bearings under dry wear

To prolong the serve life of roller element bearings (REB) and improve the reliability of mechanical system, the tribological behavior of the “washers-cage-rollers” system of grooves textured thrust cylindrical roller bearings (TCRB, 81107TN) under dry wear was researched. The pattern parameters include: width of grooves (WOG, 50, 100, and 150 μm), depth of grooves (DPOG, 7, 11, and 15 μm), as well as groove deflection angle (GDA, 0°, 45°, 90°, and 135°). The influence mechanism of grooves on the tribological properties of REBs is discussed. The results show that: As the GDA is 45°, the coefficient of friction (COF) and mass loss of bearing is the lowest among four angles. The average COFs of grooves textured bearings are much higher than that of smooth one, and their mass losses are all lower than that of smooth bearing. The influence of pattern parameters on the surface stresses of grooves textured bearings is weak. In this work, when the WOG is 50 μm and the DPOG is 7 μm, the wear loss of grooves textured bearing is the lowest, reduced by up to 75.6%. This work can provide a valuable reference for the raceway design and optimization of REBs.

WEAR CHARACTERIZATION OF LM29 ALLOY WITH40 MICRON SIZED B4C REINFORCED METAL COMPOSITES

This paper deals with the fabrication and evaluation of wear properties by introducing40 micron size B4C particulates into LM29 alloy matrix. LM29 alloy based metal matrix composites were prepared by stir casting method. 3, 6 and 9 wt. % of 40 micron sized B4C particulates were added to the base matrix. For each composite, the reinforcement particles were pre-heated to a temperature of 600 degree Celsius and then dispersed in steps of two into the vortex of molten LM29 alloy to improve wettability. The Micostructural study was done by using Scanning Electron Microscope (SEM), which revealed the uniform distribution of B4C particles in matrix alloy, EDS analysis confirmed the presence of B4C particles in the LM29 alloy matrix.A pin-on-disc wear testing machine was used to evaluate the wear loss of prepared specimens, in which a hardened EN32 steel disc was used as the counter face. The results revealed that the wear loss was increased with increase in normal load and sliding speed for all the specimens. The results also indicated that the wear loss of the LM29-B4C composites were lesser than that of the LM29 matrix. The worn surfaces and wear debris were characterized by SEM microanalysis.