Papers by Keyword: Tribology

Abstract: Lubricant-free deep drawing is motivated by the avoidance of using environmentally harmful lubricants as well as the potential for shortening the process chain by eliminating lubricant application and component cleaning. Central challenges of dry deep drawing are a significant increase in friction as well as in adhesive tool wear due to a lack of a separating lubricant layer between tool and workpiece. An approach to meet these challenges is the modification of the tools through diamond-like coatings. Based on findings from laboratory tests, a-C:H and ta-C coatings were selected and their effectiveness in overcoming these challenges was demonstrated in single stroke tests in previous research. In order to use the process-specific advantages of forming technology, high tool life is required. In this context, this research aims at investigating the application behavior of a-C:H and ta-C coatings during lubricant-free deep drawing of a high number of components made of the aluminum alloy AA5182. For this purpose, a new wear test rig is applied, which enables the time and material efficient production of high quantities. Numerical methods are utilized to identify the drawing die radius as well as the blank holder as the highest loaded areas. Based on these findings, the wear of the coatings as well as that of an uncoated tool as a reference is analyzed in these areas by optical and tactile measurements. In addition, the influence of tool wear on the component surface quality is determined. It is proven that the ta-C coating increases the tool life from 10 components in uncoated condition up to 3,000 components.

Abstract: The paper presents the results of the development of a special group of cast composite materials based on nodular cast irons. The alloys were based on alloying cast iron with copper in amounts that exceed its solubility in liquid Fe-C-Si systems (Cu>6 wt.%). A new component is obtained in the structure of castings in the form of a complex mixture based on the Cu-phase. Inclusions are relatively large (up to 200 μm) and globular in shape, with a uniform allocation in the volume of the castings. This favorably distinguishes the obtained alloys from the known cast irons and gives them high antifriction properties. With isothermal hardening, it is possible to obtain the lowest values of wear for structures of lower bainite. Developed cast composite materials are recommended to be used as tribotechnical materials working in conditions of poor lubrication and corrosion.

Abstract: In this study, crack propagation in PPS thrust bearings under rolling contact fatigue (RCF) in water was observed, and relation between subsurface crack and internal shear stress parallel to the surface was investigated. It was found the cause of flaking was subsurface crack. They were evaluated in terms of contact stress and friction between their faces. It was discovered that subsurface cracks distributed around shear stress peak, and flaking failure was dominated by subsurface shear stress.

Abstract: The article presents the results of research on the impact of laser surface treatment on selected steel properties. The laser treatment consisted of remelting and alloying high speed steel using hard ceramic phase powders. A high-power diode laser was used in the experiment to examine the effect of parameters such as beam power and powder type on the structure and properties of the surface layer. A structural mechanism was observed consisting in obtaining, after laser processing, a super fine crystalline structure and a dendritic structure at the remelting zone. Structural changes have been found to be associated with improved properties such as hardness, microhardness and wear resistance. Steel treated with conventional heat treatment was used as a comparative material.

Abstract: The purpose of this study was to investigate the influence of oleic acid as an additive in palm and coconut oils on tribological properties. Palm and coconut oils are vegetable oils that are consisted of free fatty acid, which one of the materials used as a source of environmental lubricant. Fatty acids in vegetable oil consist of saturated fatty acids and unsaturated fatty acids. Palm and coconut oils are rich in palmitic acid, which is categorized as saturated fatty acids. Whereas oleic acid is unsaturated fatty acids, and it has good lubricity as a lubricant. The effect of variation of oleic acid (10wt%, 20wt%, and 30wt%) in palm and coconut oils was investigated on tribological properties. The tribological properties were investigated by using a pin on disc apparatus and a ball bearing test rig. The results show that the effect of 10%wt oleic acids in coconut oil significantly increased its tribological properties with Δ scar width around 96 μm and 154 μm for the inner race and outer race, respectively.

Abstract: The objective of this work is to study the fiber orientation effect on frictional material properties and tribology performance. Effects of orientation on hardness, maximum load capacity under bending, the friction coefficient and surface wear of the composites were investigated. In this research, 3D printing technique was used to create workpieces in order to control fiber arrangement which is random, 0, 45, and 90 degrees. The results suggested that the fiber direction insignificantly affects material hardness with all specimen showing similar value of average hardness of approx. 90 HRC. However, the fiber orientation had a strong influence on material bending strength. The specimen with forced fiber orientation showed lower bending resistance compared to that with random fiber orientation. This may be caused by the non-uniform distribution of fiber which could promote fracture initiation site in some area with low fiber density. The coefficient of friction of the composite material was found to strongly related to it wear behavior, i.e. higher wear rate results in higher value of friction coefficient. The wear resistance was found to be controlled by both the fiber direction and fiber interface. With fiber oriented at 90 degree to sliding direction, higher coefficient was observed. However, as surface wear took place, the effect of wear debris results in an increase in friction coefficient. For 3D printed specimen, wear was increased with fiber interface density resulting in higher wear rate of specimen with 0-degree fiber orientation compared to those with 45-and 90-degree orientation during. Hence, the specimen with 0 degree fiber direction showed similar value of coefficient of friction to those with random and 90 degree fiber orientation.

Abstract: Lubricants have a very crucial role in machinery industry for friction reduction and wear reduction between two relatively moving parts. The current study enlightens the works from various authors on evaluating the tribological behavior of environment friendly vegetable based oils as emerging biodegradable lubricants. The influences of the vegetable oils on friction and wear performance using different Tribometers were reported. The review focuses efforts on the development and commercialization of these vegetable based oils as industrial lubricants for manufacturing industries, mainly, metal forming and metal cutting. The review reveals that, many vegetable oils can be used as industrial lubricant, due to their exemplary attributes in terms of friction and wear reduction, which would help to decrease the universal demand of commercial lubricants which are based on petroleum resources to a great extent.

Abstract: CN-Nb, CN-Ti and CN-Zr that are respectively doped with Nb, Ti and Zr metal in a CN coating are deposited on SKH51 substrate using DC unbalanced magnetron sputtering (DC-UBM). The coatings’ chemical characterization, morphology, mechanical, tribological and corrosion properties are determined. The XRD analysis shows when a low content of metal is added, the coatings exhibit DLC structures. Result from the incorporation of metals, coatings performed denser texture. Simultaneously, the surface became smoother and denser while surface roughness varied from 0.036 to about 0.020 mm. Various properties are improved over CN coating, CN-Ti has a 64% greater hardness at 21.9 Gpa and adhesion 26% better, with a critical load of 87 N. The elastic recovery ranges from 68% (CN) to 100% (CN-Nb and CN-Zr), the wear rate varies from 0.51 10^-6mm³/Nm (CN) to 0.1 10^-6mm³/Nm (CN-Zr) and the wear depth is reduced by about 73%. An increase in the elastic recovery gives a decreased wear rate. In addition, the corrosion resistance is increased because there is a decrease in the corrosion current density and the CN-Zr coating performed about 35 times better than a CN coating.

Abstract: The application range of natural fiber composites are increasing rapidly in several engineering areas. Unidirectional short castor oil fiber reinforced epoxy composites are fabricated using hand layup process with 40 vol% and 5mm length. Dry sliding wear tests are conducted using pin on disc tribometer. Applied loads are 15, 30 & 45N and track diameters were kept at 100, 110 and 120mm to achieve sliding distances of 1000, 2000 and 3000m respectively with adjustment of running times 6.5, 12 and 16 minutes at speed of 500 RPM. Full factorial DoE is employed and influence of each parameter on amount of wear, CoF and temperature are studied using ANOVA. It is found that load is the highly influential factor affecting amount of wear, CoF and temperature followed by sliding distance and other factors. Also, regression models are developed with good fit. The developed models predicted the results with 0-8 % error.

Abstract: Aluminium matrix composites (AMCs) are indispensable materials used extensively in the aerospace and automobile industries and are highly endorsed due to their good mechanical properties. In this paper, various compositions of the AMCs were fabricated, tested and analyzed using pin on disc tribometer test to understand the tribological behaviour and wear mechanism properties. The volume percentages of the Aluminium composite reinforced with boron carbide and graphite present in the form of Al-B₄C-Graphite are Al-B₄C (5%)-Graphite (5%), Al-B₄C (10%)-Graphite (5%), Al-B₄C (5%)-Graphite (15%), Al-B₄C (10%)-Graphite (15%), Al-B₄C (15%)-Graphite (15%). Loads were varied in steps of 10N, from 10N to 50N while the sliding velocity was correspondingly set as 0.7, 1.4 and 2.1m/s. SEM image analysis was conducted to understand surface tribology after wear tests. The composite Al-B₄C (15%)-Graphite (15%) exhibited best wear resistance which can be credited to the bearing capacity of boron carbide particles and adherent graphite layer.