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The present case-study was aimed at evaluating and comparing the frictional properties (friction and wear) of alternative concepts for a shaft-bushing component in comparison to the actually used benchmark system. Through the use of a specially designed shaft-bushing tribology labor-sized test setup in combination with a high-precision modular tribometer, the overall performance of alternative concepts were evaluated and compared. Benchmark shafts consisted of nitro-carburized and oxidized bearing steel and benchmark bushings were made of sintered steel. The investigated alternative concepts consisted of shafts with a different thermal pre-treatment against benchmark bushings; benchmark shafts against surface modified bushings; and lubricated benchmark bushings (instead of lubricated shafts) with two different lubrication times before testing. For each concept under study, 3 performance tests were performed in order to assess the reproducibility of the results obtained. The most promising alternative component concepts identified through this labor-sized model screen test were then field tested by IMS Gear and the obtained results were in accordance with the labor test results.

Purpose In the cardboard package production process, the cardboard roll and the cardboard bottom are joined in the seaming process. During the process, the cardboard is plastically deformed and damage to the cardboard surface can occur. The purpose of this study was to optimise the macro-geometrical parameters of the seaming chuck in order to minimise the cardboard damage during the seaming process. Design/methodology/approach The influences of geometrical properties of the seaming chuck on the seaming force were investigated using numerical investigations and statistical analysis. Findings A force-displacement model was established, which enabled the optimisation of the seaming chuck geometry for a reduction of the seaming force. Research limitations/implications Results from the present study imply that for tribological optimisation, not only the surface properties such as roughness and frictional response but also the macro-geometrical features of the actual mechanical components should be considered, as these can considerably affect the contacting forces and consequently the friction within the tribosystem. Practical implications Based on the performed analyses, a new seaming chuck was manufactured, which is currently undergoing testing in the real production process and is providing improved performance in terms of seam quality as compared to the benchmark. Originality/value In the present work, a systematic approach towards the use of statistical methods in tribological optimisation projects is provided for a use case applying a combination of numerically calculated and experimentally measured values. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2020-0065/

A surface texture can be subdivided into three categories based on the magnitude of its wavelengths, i.e., macro-geometrical form, waviness, and roughness (from largest to smallest). Together, these components define how a surface will interact with the opposing surface. In most ice tribology studies

The ice friction behavior of various microtextured polymer surfaces was studied with respect to ice temperature and applied load using a customized linear tribometer. Similar micropillar patterns were replicated on polypropylene and two rubber compounds, and when hierarchical micro–micro textures were present, all the materials exhibited superhydrophobicity. Taller protective micropillars were shown to be crucial for protecting the smaller microtextures from abrasive wear. The mechanical properties of the polymers affected the sliding friction of the microtextured surfaces on ice. High loading of hierarchical textures on rigid polypropylene or operation near the ice melting point tended to increase its adhesion tendency or resisting behavior. The sliding performance of the hard and soft rubber compounds was temperature-dependent, and the texture on the soft rubber influenced the sliding friction differently depending on the ice temperature. Consequently, textural modifications of the sliding surface enabled a certain degree of control over the sliding friction behavior on ice.

In the present study, static coefficients of friction of pure and friction modified (FM) polyamide 6 (PA6) polymers against primer-coated steel surfaces were investigated under a series of nominal contact pressures and by considering the influences of water absorption by the polymer, temperature, counter-body surface roughness and lubrication conditions. Under the majority of the test conditions investigated, FM PA6 exhibited lower static friction than pure PA6. Under unlubricated conditions, this was due to the low adhesion of the FM PA6 provided by its friction modifying inclusions; while under lubricated conditions, a combination of softening due to water absorption and decreased adhesion provided by its friction modifiers enabled lower static friction, especially at medium and high contact pressures.

Elastomers are currently used intensively in various industrial applications. However, their deployment in dry tribological contact is normally inhibited by their poor dry sliding friction behaviour due to their intrinsically high adhesive characteristics. This problem is normally addressed in the industry by using various fluid (greases or oils) or solid (coatings or lacks) lubricants. Alternatives to the use of lubricants for tribosystems involving elastomers exist in the form of modifications of the elastomer composition or by reducing their effective nominal contact area by using surface texturing. The latter approach of reducing the adhesive nature of elastomers by surface structuring is the main focus of the present study. Two different micro-sized structures (consisting of micro-pits) were produced on thin Al inlays using a microscopically scaled punching process. These inlays were thereafter glued onto laboratory-scale injection moulds. These micro-pitted moulds were subsequently used to produce injection moulded micro-pillared Liquid Silicone Rubber (LSR) pads. The present study was focused on three different aspects: 1. Determination of the degree of replication of microstructures from injection moulds to the surface of LSR pads; 2. Evaluation of any possible friction reduction induced by a decrease of the nominal contact area through micro-texturing of LSR pads in dry tribological tests; and 3. Evaluation of the wear resistance of micro-pillared LSR pads under dry conditions. The results have shown that successful production and relatively accurate replication of micro-pitted structures from injection moulds onto LSR pad surfaces in the form of micro-pillars may be achieved. Furthermore, it was shown that a decrease of the effective nominal contact area through micro-pillars may enable a reduction of friction in comparison to the benchmark (unstructured LSR pads), but only for low normal loads where the adhesive component of friction is playing a determining role. Finally, wear tests have shown that the wear resistance of both micro-pillared structures produced on LSR pads under dry conditions against Al or PA6.6-GF30 was relatively poor. Both structures exhibited extensively worn regions after a testing distance of 11 m: structure 1 showed a larger worn area ratio than structure 2 (ratio worn area/total area ~45%–60% for structure 1 and ~30% for structure 2).

Ice friction is affected by various system and surface-related parameters such as ice temperature, ambient air temperature and humidity, relative sliding velocity, specific surface pressures and surface texture (waviness, roughness) as well as the macroscopic geometry of the samples. The influences of these parameters cannot be easily separated from each other. Therefore, ice friction is a very complex tribological system and it is challenging to draw sound conclusions from the experiments. In this work, ice friction experiments with stainless steel samples that have different isotropic surface roughness values were carried out. Two tribological experimental setups were used: (i) an inclined ice track where the sliding velocity of the freely sliding steel samples was determined and (ii) an oscillating tribometer, where the coefficient of friction was assessed. For both experimental setups, the environmental parameters such as air temperature, relative humidity and ice surface temperature as well as the test parameters such as normal load and surface pressure were kept as constant as possible. The results of the experiments are discussed in relation to the ice friction mechanisms and the friction regimes.

Anodization of aluminum (Al) is a well-known process for the production of oxidized Al surfaces. Within the scope of the present work, three different Al-oxide layers, produced with different electrochemical methods, were investigated in view of their layer morphology and tribological properties. For this purpose, a newly developed PCO layer (Innovent e.V.), and two commercially available layers, Ematal and a CERANOD®, were compared. Al-oxide layers produced on flat samples were tested against cylindrical DIN 100Cr6 rings under dry sliding conditions. It was observed that under the selected conditions, the frictional behavior of the Al-oxide layers can be influenced by their structural composition and their surface topography, i.e. is different when their structure is amorphous or crystalline. The newly developed Al-oxide layer, which possesses the lowest surface roughness and a very uniform porosity, provided the longest lasting low friction period. Since γ-Al2O3 was also observed in this layer, it is believed that the structural composition of the Al-oxide layer has additionally influenced the frictional response of these samples.

Tribological conditions in bulk metal forming processes are characterized by high contact pressures and large relative movements at high velocities between the tool and the workpiece. In addition, significant surface enlargements and elevated temperatures can occur. It is very challenging to reproduce such contact conditions on pin-on-disc tribometers. In this study, a method for simulating the contact conditions of a metal forming process on a pin-on disc tribometer is presented. Special test samples have been designed in order to achieve high contact pressures and surface enlargements with a homogeneous distribution of these quantities within the contact zone. It is shown that the test method delivers reproducible results and enables the detection of small changes of the contact conditions. Furthermore, microstructural changes of the real contact surface can also be simulated, which was verified by SEM imaging.

In this study, tool steel substrates were plasma-nitrocarburised at different processing parameters and afterwards tribologically tested under non-lubricated sliding conditions. It was observed that the micromechanical properties of the compound layer (thickness, hardness, roughness, surface topography) strongly affect the tribological behaviour of the nitrocarburised surface and can be tailored through the adjustment of the nitrocarburising parameters so that very favourable wear and friction behaviours can be achieved.

Coarsening of precipitates can have a profound effect on the mechanical properties of martensitic 9–12 wt.% Cr steels, which are typically used in critical parts of fossil-fuel power plants such as turbines, headers, and main steam pipes. In the present study, changes in precipitates’ size and distribution in the simulated heat-affected zone of two different 9–12 wt.% Cr steels (X20 and P91) after different aging conditions were analyzed and correlated with their creep, friction, and wear behaviors. It was shown that prior to aging, the morphology of the steel matrix (prior austenite grain size and microstructure homogeneity) governed the creep rate and the tribological performance of both steels, while after aging their response was additionally determined by the combination of the number and the size of precipitates. For the selected samples (prepared under identical conditions), number of precipitates was found to be within a narrower range for the X20 steel as compared to the P91 steel. For both steels, aging for a shorter time at the higher temperature yielded significantly higher stationary creep rate values as compared to aging for longer time at the lower temperature. The increase was more pronounced in the P91 than in the X20 steel. Both prior to and after aging, the P91 steel typically provided slightly higher creep resistance than the X20 steel, while the latter provided slightly better tribological performance. Furthermore, as a function of the increasing number of precipitates, static coefficient of friction in air atmosphere was approximately linearly decreasing, while the wear rate initially decreased.

The influence of temperature on friction and wear of unlubricated DIN 100Cr6 steel/steel contacts was studied in different anaerobic gaseous atmospheres, namely argon (Ar), nitrogen (N 2 ) and carbon dioxide (CO 2 ), and air atmosphere was used as benchmark. Tribological experiments were performed at high temperature (200 °C) and the results were compared with previously published results from experiments performed at ambient temperature (20 °C). Reciprocating ball-on-disc tribological tests were conducted with high contact pressures (maximum initial contact pressure of 1.5 GPa). In all anaerobic gas atmospheres at high temperature, lower friction and wear were measured than in air atmosphere. The lowest friction and wear were measured in CO 2 atmosphere; they were slightly higher in N 2 atmosphere and even more slightly higher in Ar atmosphere. In all anaerobic atmospheres, different oxidation kinetics of steel surfaces occurred as compared with air atmosphere. For N 2 and CO 2 atmospheres, XPS analyses of the wear debris showed an increased concentration of non-carbidic carbon and furthermore for the CO 2 atmosphere, iron–carbon–oxygen layers were also found which probably provided the very favourable friction and wear properties observed in this atmosphere. In N 2 and CO 2 atmospheres, higher wear and friction were observed at high temperature than at ambient temperature, which indicates that at high temperature, a deterioration of the beneficial properties of the N 2 and CO 2 -reacted tribolayers occurred. On the contrary, in Ar atmosphere at high temperature, a decreased adhesion and a significantly lower wear as compared with ambient temperature was observed.

In the present study, PA6 polymers with and without solid lubricant inclusions were investigated against S1100QL steel surfaces that had different surface roughness values&mdash, a very high surface roughness (Rz &asymp, 40 &micro, m) and a low surface roughness (Rz &asymp, 5 &micro, m). Static and dynamic friction coefficients were analysed under a series of nominal contact pressures (2.5 to 40 N/mm2) considering the influences of polymer water saturation, temperature, counter-body surface roughness and lubrication. Mechanisms for the observed influences of the respective parameters are provided and are interpreted from the view of the adhesive and deformative contributions to the friction force.

The wire flame spray process was used to produce electrically conductive and flexible Al coatings onto diverse textile fabrics. The investigation studied the influence of the spraying parameters and fabric materials on the electrical conductivity of the metal-fabric composites. Furthermore, this study showed that the production of flexible Li-ion batteries having good electrical properties based on the use of such flame-sprayed aluminium cathode current collectors is viable. Results show that a coating quantity threshold of about 20 mg/cm2 exists to obtain a sufficient electrical surface conductivity for a commercial use of the produced metal-fabric composites. An excellent electrical surface conductivity of the composites (about 500 SA) could be achieved through an adequate optimization of the spraying parameters. This conductivity increase enabled a reduction of the coating quantity and thus the flexibility of the fabric materials is better conserved, rendering the use of such composites for flexible batteries even more interesting. This study showed that the production of electrically conductive and flexible metal-fabric composites having sufficient electrical conductivity for the manufacture of flexible Li ions batteries is possible. This new method of producing such batteries represents an alternative to other chemically based processes which are hazardous to the environment because of their chemical nature.

Partially amorphous iron-based coatings were produced onto aluminium using a powder flame-spraying process with a commercially available feedstock powder (Nanosteel SHS-7170) obtained from the Nanosteel Company Inc.. Several coating properties such as the microstructure, porosity, phase content, micro-hardness, and wear resistance were evaluated in the as-sprayed condition. As shown by the results obtained, the powder flame iron-based coatings perform relatively well in term of wear resistance in comparison with similar coatings produced using other expensive thermal spray techniques. Furthermore, this study shows that all the coating properties (microstructure, porosity, phase content, hardness and wear performance) depend strongly on the flame spraying parameters used. Finally, this paper demonstrates clearly that the flame-spray process may be used to produce amorphous iron-based coatings having a good wear resistance, and that this process appears to be a suitable inexpensive alternative to plasma or HVOF processes based on the present results.

It is well known that elastomers usually possess poor dry sliding friction properties due to their highly adhesive character. In order to overcome this problematic behavior in industrial applications, interfacial materials such as oils, greases, coatings, or lacks are normally used in order to separate or to functionalize the contact surfaces of elastomers. Alternatively, the high adhesion tendency of elastomers may be explicitly reduced by modifying the elastomer composition itself or by enabling a reduction of its effective contact area through, for example, surface laser texturing. This second approach, i.e., the reduction of the adhesive character of elastomers through laser structuring, will be the main topic of the present study. For this purpose, different micro-sized grooved structures were produced on flat injection molds using an ultra-short pulsed laser. The micro-structured molds were then used to produce injection molded micro-ridged Liquid Silicone Rubber (LSR) sample pads. The investigations consisted firstly of determining the degree of replication of the mold micro-structures onto the surface of the LSR pads and secondly, to ascertain the degree of reduction of the friction force (or coefficient of friction) of these micro-ridged LSR pads in comparison to the benchmark (unstructured LSR pads) when tested under dry conditions against Aluminum alloy (Al-6082) or PA6.6-GF30 plates. For this second part of the investigation, the normal force (or contact pressure) dependency of the coefficient of friction was determined through stepwise load increasing friction tests. The results of these investigations have shown that the production of micro-ridged surfaces on LSR pads through laser structuring of the injection molds could be successfully achieved and that it enables a significant reduction of the friction force for low normal forces (or contact pressures), where the component of adhesion friction is playing an important and determining role in the overall friction behavior of the LSR elastomer.

Thermal spraying of a nanograined WC-12Co cermet powder using high velocity oxy-fuel was employed to produce nanostructured coatings. The spray conditions were varied by employing a wide range of thermal spray parameter settings and using either hydrogen or propylene as fuel gas. By determining the characteristics of the spray jet for each set of spray conditions and by studying various aspects of the coatings, including the microstructure, properties, and performance in dry abrasion tests, conclusions were drawn regarding the effect of the spray parameters on the properties and performance. When comparing the effect of using hydrogen or propylene as fuel on in-flight particle characteristics, the results indicated that, for a given particle temperature, the particle velocity tended to be higher with hydrogen than propylene. As well, it was found that the coatings produced using hydrogen tended to have a higher microhardness and a lesser degree of carbide degradation. The resistance to wear in dry abrasion was significantly higher for coatings produced using hydrogen as fuel. For both series of coatings, it was found that the abrasion resistance increased with the particle temperature at the point of impact during thermal spraying and with the hardness of the coating. The abrasion resistance of coatings produced using propylene appeared to be much more sensitive to changes in hardness. For the thermal spray system studied in this work, the results indicate that nanostructured WC-12Co coatings having a maximum abrasion resistance are obtained by using hydrogen as fuel under conditions such that the particles achieve temperatures above approximately 1850-1900°C and a speed greater than 575-600 m/s.