Friction Force of Locust <Emphasis Type="Italic">Locusta migratoria manilensis</Emphasis> (Orthoptera,Locustidae) on Slippery Zones of Pitchers from Four <Emphasis Type="Italic">Nepenthes</Emphasis> Species

Slippery zone of inner pitchers in Nepenthes species serves functions of trapping insect and restraining escape of prey being used as a main nitrogen and phosphorus source. To investigate the influence of the slippery zones from different Nepenthes species on friction force of insect possessing smooth adhesive pads and rigid claws, friction force of locust Locusta migratoria manilensis on slippery surface of pitchers from four Nepenthes species was measured. The friction force of locust was also measured on stainless steel plate for comparison. Different friction forces were showed among the four Nepenthes species (mainly 380–550 mN in imagines, 120–185 mN in larvae), and were apparently lower than on the stainless steel plates (mainly 650 mN in imagines, 230 mN in larvae). Surface morphologies and structures of the slippery zones were observed and analyzed with scanning electron microscope and scanning white-light interferometer to explain the discrimination of the friction force. The slippery zones from the selected Nepenthes species exhibited similar surface morphologies and structures, but differed obviously in the geometrical dimensions of the surface architectures, and the difference probably result in the discriminations of the locust’s friction force. The obtained results contribute to further interpretation of the slippery zone’s anti-attachment mechanism to insect and presumably supply suitable theoretical foundations for biomimeticing structure and function of the slippery zone to develop slippery plates for trapping plague locusts or other agricultural pests.     

Friction and Wear Characteristics of Haynes 25, 188, and 214 Superalloys Against Hastelloy X up to 540 <Emphasis Type="Bold">°</Emphasis>C

As demand for more power increases, compression ratios, and operating temperatures keep rising. High speeds combined with high temperatures make turbomachinery sealing applications even more challenging. In order to confirm sufficient service life material pairs should be tested under conditions similar to engine operating conditions. This study presents high temperature friction and wear characteristics of cobalt/nickel superalloys, Haynes 25 (51Co–10Ni–20Cr–15W), Haynes 188 (39Co–22Ni–22Cr–14W), and Haynes 214 (75Ni–16Cr–3Fe–0.5Mn) sheets when rubbed against Hastelloy X (47Ni–22Cr–18Fe–9Mo) pins. Tests are conducted at 25, 200, 400, and 540 °C with a validated custom design linear reciprocating tribometer. Sliding speed and sliding distance are 1 Hz and 1.2 km, respectively. Friction coefficients are calculated with friction force data acquired from a load cell. Wear coefficients are calculated through weight loss measurements. Results indicate that Haynes 25 (H25) has the lowest friction coefficients at all test temperatures. Above 400 °C, H25 and Haynes 188 (H188) exhibit the best wear resistance. Protective cobalt oxide layers are formed on the H25 and H188 at 540 °C in addition to nickel, chrome, and tungsten oxides. Although, it has better oxidation resistance, Haynes 214 has relatively higher wear rates than other tested materials especially at low temperatures. However, its wear performance improves beyond 200 °C.     

Abrasive and Adhesive Wear Behavior of Arc-Evaporated Al<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Cr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>N Hard Coatings

During the last decade, the usage of difficult-to-machine materials such as austenitic stainless steels has increased continuously in various industrial applications. Tools such as blind hole taps, punches, or deep drawing molds are often exposed to severe wear while machining/forming these materials, mainly due to excessive adhesion and material transfer. On combination with abrasive wear due to work-hardened wear debris, tool lifetime in these applications is often limited. In this study, ball-on-disc experiments were carried out with arc-evaporated AlCrN coatings with different Al/(Al + Cr) ratios against Al₂O₃ and austenitic stainless steel balls in ambient atmosphere. Test temperatures of 25, 500, and 700°C were chosen for the hard Al₂O₃ balls simulating severe abrasive loads, whereas 25, 150, and 250°C were used for the softer stainless steel material to evaluate the adhesive wear behavior. Characterization of the wear tracks was done by scanning electron microscopy in combination with energy-dispersive X-ray analysis and optical profilometry. The best abrasive wear resistance during testing against Al₂O₃ was observed for the coating with the highest Al content. In the case of the austenitic stainless steel balls, sticking of the ball material to the coating surface was the dominating wear mechanism. The influence of test temperature, chemical composition, and surface roughness was studied in detail.     

Ultralow-friction and wear properties of IF-WS<Subscript>2</Subscript> under boundary lubrication

Tested in boundary lubrication, inorganic fullerene-like WS₂ nanoparticles used as additives in oil present interesting friction reducing and anti-wear properties. A dispersion with only 1 wt% of particles leads, from a contact pressure of 0.83 GPa, to a drastic decrease of the friction coefficient below 0.04 and to very low wear. High resolution transmission electron microscopy (HRTEM), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Raman Spectroscopy and video imaging were used to explain the lubrication mechanisms. A structural modification of fullerene-like nanoparticles into sheets during the friction test was evidenced to be the main effect at the origin of these properties.*To whom correspondence should be addressed. E-mail: lucile.joly-pottuz@ec-lyon.fr     

A Memetic Algorithm for the <Emphasis Type="SmallCaps">n</Emphasis>/2/Flowshop/α<Emphasis Type="SmallCaps">F </Emphasis>+ β<Emphasis Type="SmallCaps">C</Emphasis><Subscript>max</Subscript> Scheduling Problem

Machine scheduling has been a popular area of research during the past four decades. Its object is to determine the sequence for processing jobs on a given set of machines. The need for scheduling arises from the limited resources available to the decision-maker. In this study, a special situation involving a computationally difficult n/2/Flowshop/ αF + βCmax flowshop scheduling problem is discussed. We develop a memetic algorithm (MA, a hybrid genetic algorithm) by combining a genetic algorithm and the greedy heuristic using the pairwise exchange method and the insert method, to solve the n/2/Flowshop/ αF + βCmax flowshop scheduling problem. Preliminary computational experiments demonstrate the efficiency and performance of the proposed memetic algorithm. Our results compare favourably with the best-known branch-and-bound algorithm, the traditional genetic algorithm and the best-known heuristic algorithm.     

Aqueous Lubrication of SiC and Si<Subscript>3</Subscript>N<Subscript>4</Subscript> Ceramics Aided by a Brush-like Copolymer Additive,Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine)-<Emphasis Type="Italic">graft</Emphasis>-poly(ethylene glycol)

We have examined the adsorption properties of poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG)—a brush-like polymer—on Si₃N₄ and SiC surfaces and determined its impact on the aqueous lubrication of Si₃N₄ and SiC at various speeds and applied loads. The addition of PLL-g-PEG in aqueous solution reduces the interfacial friction forces significantly for self-mated sliding contacts of these two ceramics, as compared to lubrication with water or buffer solution alone. For SiC, the improved lubricating performance by addition of PLL-g-PEG was apparent for all tested speeds (from 1.4 to 185 mm/s under 2 N load). For Si₃N₄, the effect was more apparent in the slow-speed regime (≤20 mm/s under 2 N load) than in the high-speed regime (>100 mm/s), where extremely low coefficients of friction (μ ≤ 0.006) are readily achieved by aqueous buffer solution alone. It was further observed that the optimal lubricating effect with Si₃N₄ is achieved when the tribopairs are first run-in in polymer-free aqueous buffer to render the sliding surfaces smooth, after which the PLL-g-PEG copolymer is added to the buffer solution.     

MoS<Subscript>2</Subscript> Films Formed by <Emphasis Type="Italic">In-contact</Emphasis> Decomposition of Water-soluble Tetraalkylammonium Thiomolybdates

Synthesis and tribological evaluation of three tetraalkylammonium thiomolybdate (R₄N)₂MoS₄ (R = methyl, propyl, or ammonia) aqueous-based lubricant additives on a ball-on-disk tribometer was carried out for a steel–aluminum contact. Tests were performed at the same conditions of load, entrainment speed, sliding distance, temperature, and concentration of MoS₂ to compare the activity (lubrication effect) of the thiomolybdates prepared. A friction reduction is observed for the three salts compared to pure water; however, significant differences in friction coefficient are observed depending on the alkyl group. SEM/EDAX and Raman analysis of the wear tracks reveal the in-contact formation of a MoS₂-lubricating film, rich in molybdenum and sulfur.     

Tribological behaviors and mechanisms of Ti<Subscript>3</Subscript>AlC<Subscript>2</Subscript>

Tribological behaviors and the relevant mechanism of a highly pure polycrystalline bulk Ti₃AlC₂ sliding dryly against a low carbon steel disk were investigated. The tribological tests were carried out using a block-on-disk type high-speed friction tester, at the sliding speeds of 20–60 m/s under a normal pressure of 0.8 MPa. The results showed that the friction coefficient is as low as 0.1∼0.14 and the wear rate of Ti₃AlC₂ is only (2.3–2.5) × 10⁻⁶ mm³/Nm in the sliding speed range of 20–60 m/s. Such unusual friction and wear properties were confirmed to be dependant dominantly upon the presence of a frictional oxide film consisting of amorphous Ti, Al, and Fe oxides on the friction surfaces. The oxide film is in a fused state during the sliding friction at a fused temperature of 238–324 °C, so it takes a significant self-lubricating effect.     

Tribological Property of Ni<Subscript>3</Subscript>Al Matrix Composites with Addition of BaMoO<Subscript>4</Subscript>

The Ni₃Al matrix composites with addition of 10, 15, and 20 wt% BaMoO₄ were fabricated by powder metallurgy technique, and the tribological behaviors were studied from room temperature to 800 °C. It was found that BaAl₂O₄ formed during the fabrication process. The Ni₃Al composites showed poor tribological property below 400 °C, with high friction coefficients (above 0.6) and wear rates (above 10⁻⁴ mm³/Nm). However, the composites exhibited excellent self-lubricating and anti-wear properties at higher temperatures, and the composite with addition of 15 wt% BaMoO₄ had the lowest wear rate (1.10 × 10⁻⁵ mm³/Nm) and friction coefficient (0.26). In addition, the results also indicated that BaAl₂O₄ for the Ni₃Al composites did not exhibit lubricating property from room temperature to 800 °C.     

Automatic discontinuous 2 transmission lines with sections of different productivity (<Emphasis Type="Italic">q</Emphasis><Subscript>1</Subscript> < <Emphasis Type="Italic">q</Emphasis><Subscript>2</Subscript>)

An analytical solution is derived for automatic discontinuous 2s’ transmission lines with sections of different productivity (q ₁ < q ₂). On that basis, a range of characteristics that depend on the reliability of the production sections and the bunker capacity may be determined. Accordingly, the solution provides the basis for improvements in the design of such lines.     

Tribological Properties of Nanocomposite CrC<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/a-C:H Thin Films

Recently we showed that coatings, prepared by unbalanced magnetron sputtering from a metallic Cr target in an Ar/CH₄ discharge are composed of nanocrystalline CrC _x embedded in an a-C:H matrix. This work investigates the structural correlation of such nanocomposite CrC _x /a-C:H coatings to their tribological properties. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize the phase composition and the chemical bonding in the films deposited at different experimental conditions. The coating microstructure was investigated on selected samples by high-resolution transmission electron microscopy. For CrC _x -dominated coatings deposited at CH₄ partial to total pressure ratios (p_CH4/p_t) < 0.42, only minor changes regarding the friction coefficients and the abrasive wear rates were observed although microstructural changes towards a higher degree of crystallinity were proven by transmission electron microscopy and substantiated with XPS results. For a-C:H dominated coatings deposited at p_CH4/p_t > 0.42, the friction coefficients and abrasive wear rates were shown to decrease with increasing a-C:H phase content and its more sp²-like bonding configuration. It can be concluded that the microstructural changes in terms of CrC _x crystallite coarsening and bonding configuration of the a-C:H matrix phase are responsible for the observed changes of the friction coefficients and wear rates.     

Effect of deposition pressure on microstructure and tribological behavior of MoS<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/MoS<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>-Mo nanoscale multi-layer films

MoS _x /MoS _x -Mo multi-layer films consisted of several bilayers and a surface layer on steel substrate were deposited by d.c. magnetron sputtering at different deposition pressures. Each bilayer contained a MoS _x layer with 80 nm in thickness and a MoS _x -Mo composite layer with 20 nm in thickness. With the increase of deposition pressure, the perpendicular orientation of the basal plane prevailed while the parallel orientation decreased. The tribological properties of the multi-layer films were investigated by using a ball-on-disk tribometer both in vacuum and in humid air. The multi-layer film deposited at 0.24 Pa had a compact, consistent layered structure with high intensity of (002) plane and low S content compared to the others deposited at 0.32 and 0.40 Pa, and showed the lowest friction coefficient and wear rate in humid air.     

The Role of Configuration Entropy in Boundary Lubricants Based on the <Emphasis Type="Italic">n</Emphasis>-Perfluoropropylene Oxide Main Chain Structure

We have investigated the resistance of a novel end-functionalized perfluoropolyether (PFPE) lubricant film to slider–disk interactions caused by low-flying sliders. The PFPE lubricant is based on the CF₂CF₂CF₂O main chain monomer unit. Both slider–disk interactions and the formation of lubricant moguls are significantly reduced compared to the Fomblin Z backbone, (CF₂O) _p –(CF₂CF₂O) _q . These results are interpreted on the basis of ab initio quantum chemical computations that show that the barrier to internal rotation about the C–O bond in the CF₂CF₂CF₂O monomer unit is significantly larger than in the CF₂O monomer unit that is bordered by another CF₂O monomer unit, ~8 kcal/mol compared to <2 kcal/mol, respectively. It is proposed that main chains containing CF₂O monomer units will be very flexible and hence their physical properties will be more sensitive to adhesive and cohesive interactions, while main chains containing CF₂CF₂O and CF₂CF₂CF₂O monomer units will be comparatively stiffer and hence their physical properties will be less sensitive to adhesive and cohesive interactions.     

End-grafted Sugar Chains as Aqueous Lubricant Additives: Synthesis and Macrotribological Tests of Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine)-<Emphasis Type="Italic">graft</Emphasis>-Dextran (PLL-<Emphasis Type="Italic">g</Emphasis>-dex) Copolymers

Comb-like graft copolymers with carbohydrate side chains have been developed as aqueous lubricant additives for oxide-based tribosystems, in an attempt to mimic biological lubrication systems, whose surfaces are known to be covered with sugar-rich layers. As adopted in the previous studies of the graft copolymer poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), which showed both excellent lubricating and antifouling properties, a similar approach was chosen to graft dextran chains onto the same backbone, thus generating PLL-g-dex. PLL-g-dex copolymers readily adsorb from aqueous solution onto negatively charged oxide surfaces. Tribological characterization at the macroscopic scale, either under pure sliding conditions or a mixed sliding/rolling contact regime, shows that PLL-g-dex is very effective for the lubrication of oxide-based tribosystems. The relative lubricating capabilities of PLL-g-dex copolymers compared with PLL-g-PEG copolymers were observed to be highly dependent on the molecular structure of the copolymers (in particular, side-chain density along the backbone) and the measurement conditions (in particular, time between tribocontacts); the PLL-g-dex copolymers with a low degree of grafted side chains (≤20% grafting of available protonated primary amine groups along the backbone) showed better lubricating performance than their PLL-g-PEG counterparts at high tribocontact frequency (≥ca. 0.32 Hz).     

In Situ TEM Observation of the Behavior of an Individual Fullerene-Like MoS<Subscript>2</Subscript> Nanoparticle in a Dynamic Contact

Inorganic fullerene-(IF)-like nanoparticles made of metal dichalcogenides (IF-MoS₂, IF-WS₂) have been known to be effective as anti-wear and friction modifier additives under boundary lubrication. The lubrication mechanism of these nanoparticles has been widely investigated in the past and even if the exfoliation and third body transfer of molecular sheets onto the asperities constitute the prevalent mechanism for the improved tribological behavior of IF nanoparticles, it has also been suggested that a rolling friction process could also play a role for well crystallized and spherical particles. In this study, in situ Transmission Electron Microscopy (TEM) observations of the behavior of single IF-MoS₂ nanoparticles were conducted using a sample holder that combines TEM and Atomic Force Microscopy (AFM) which simultaneously can apply normal and shear loads. It was shown that depending on the test conditions, either a rolling process or a sliding of the fullerenes could be possible. These in situ TEM observations are the first carried out with IF nanoparticles.     

<Emphasis Type="Bold">Plant Layout Computerised Design: Logistic and Relayout Program (LRP)</Emphasis>

Markets are affected by strong competition in terms of continuous innovation of products and processes, high customer satisfaction and low cost of production. In order to achieve these strategic results it is recommended, or necessary, to rectify lack of organisation. For instance, the increasing costs due to material handling, force factories to check the facility layout and, when necessary, to improve it. The evaluation of a prospective improvement requires a large effort and a well-established skill. The study and the optimisation of plant layout is a strategic activity. This paper represents the last step of a research program on the automatic design of plant layout. The aim is to support the design activity of plant layout by means of an integrated approach, taking into account many criteria, both quantitative and qualitative. In particular, this paper presents a global approach, based on material flow and activity relationships. It is carried out using new software, called LRP (layout and re-layout program), introduced by the authors. A real application in a factory, specialising in the production of electronic devices, is presented.     

Synergistic Effect of Nano-MoS<Subscript>2</Subscript> and Anatase Nano-TiO<Subscript>2</Subscript> on the Lubrication Properties of MoS<Subscript>2</Subscript>/TiO<Subscript>2</Subscript> Nano-Clusters

A MoS₃ precursor deposited on anatase nano-TiO₂ is heated at 450 °C in an H₂ atmosphere to synthesize MoS₂/TiO₂ nano-clusters. The nano-clusters are then characterized, and their tribological properties are evaluated. MoS₂ is found to be composed of layered structures with 1–10 nm thicknesses, 10–30 nm lengths, and 0.63–0.66 nm layer distances. The MoS₂ sizes in the MoS₂/TiO₂ nano-clusters are smaller and their layer distances are larger than those of pure nano-MoS₂. The MoS₂/TiO₂ nano-clusters also present a lower average friction coefficient than pure nano-MoS₂, but the anti-wear properties of both the nano-clusters and pure nano-MoS₂ are similar. X-ray photoelectron spectroscopy indicates that nano-TiO₂ and the element Mo are transferred to the friction surface from the MoS₂/TiO₂ nano-clusters through a tribochemical reaction. This produces a lubrication film containing TiO₂, MoO₃, and other chemicals. The nano-MoS₂ changes in size and layer distance when combined with nano-TiO₂, producing a synergistic effect. This may further be explained using a micro-cooperation model between MoS₂ nano-platelets and TiO₂ solid nanoparticles.     

Alkyl Imidazolium Ionic Liquids as Friction Reduction and Anti-Wear Additive in Polyurea Grease for Steel/Steel Contacts

Five room temperature ionic liquids (ILs), 1-butyl-3-methylimidazolium hexafluorophosphate (L-P104), 1-hexyl-3-methylimidazolium hexafluorophosphate (L-P106), 1-octyl-3-methylimidazolium hexafluorophosphate (L-P108), 1-decyl-3-methylimidazolium hexafluorophosphate (L-P110), and 1-hexyl-3-methylimidazolium tetrafluoroborate (LB106) were studied as 1 wt% additives of polyurea grease for steel/steel contacts. Their tribological behaviors as additives of polyurea grease for steel/steel contacts were evaluated on an Optimol SRV-IV oscillating reciprocating friction and wear tester and an MRS-1J (G) four-ball tester at room and high temperatures. The friction test results showed that the ILs, as 1 wt% additives in polyurea grease for steel/steel contacts, had better friction reduction and anti-wear properties at high temperature than at room temperature, and ILs can significantly improve the friction reduction and anti-wear properties of polyurea grease compared with base grease containing 1 wt% of zinc dialkyldithiophosphate (T204). The excellent tribological properties are attributed to the formation of a surface protective film composed of FeF₂, nitrides, and compound containing the P–O bonding on the lubricated metal surface by a tribochemical reaction. The ordered adsorbed films and good miscibility of ILs with the base grease also contributed to the excellent tribological properties. Wear mechanisms and worn steel surfaces were studied by a PHI-5702 multifunctional X-ray photoelectron spectrometer and a JSM-5600LV scanning electron microscope.     

Tribological Behavior of Polyamide 66-Based Ternary Nanocomposites Modified with Organoclay and SEBS-<Emphasis Type="Italic">g</Emphasis>-MA

The tribological behavior of polyamide 66 (PA66) nanocomposites consisting of styrene–ethylene/butylene–styrene triblock (SEBS-g-MA) particles and organoclay was studied. It was found that the blending sequence significantly influences the wear resistance of PA66/SEBS-g-MA/organoclay nanocomposites, and the PA66 + (SEBS-g-MA + organoclay) nanocomposite has the biggest d-spacing of organoclay nanolayers and the best wear resistance.     

<Emphasis Type="Bold">Effective Form Design of Electrode in Electrochemical Smoothing of Holes</Emphasis>

This study discusses electropolishing of holes using feeding electrodes as well as inserted electrodes for several common die materials. Traditionally, the hole polishing of a die requires a sequence of complicated premachining operations or scarce manual skill. In the current experiment, eight types of electrode are used and supplied with both continuous and pulsed direct current and another eight types of electrode are fed into holes using continuous direct current. The design features of the electrodes are of major interest for the effective electrochemical of holes. The controlled factors include the diameter of the electrode as well as the chemical composition and the concentration of the electrolyte. The experimental parameters are current density, current rating, electrode design, die material, rotational speed and feedrate of the electrode. For inserted electrodes, an electrode with a helical discharge flute performs better than one without a flute or with a straight flute. Pulsed direct current can improve the polishing effect at the expense of increased machining time and cost. For feeding electrodes, an electrode of a borer type performs better than one with a cycle lap on the leading edge. It was also found that electrobrightening after reaming needs only a short time to make the hole bright, and electropolishing saves the need for reaming, making the total process shorter than for electrob-rightening.