Analyses of abrasive wear behaviour in pin-on-plate tribo-system for several materials

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Abrasive sensitivity of engineering polymers and a bio-composite under different abrasive conditions

Two different test systems were designed to evaluate the tribological behavior of five engineering plastics (Polyamide-PA grades and Ultra High Molecular Weight Polyethylene-UHMW-PE) and a fully degradable bio-composite (Polylactic Acid-PLA/hemp fibers) targeted to agricultural machinery abrasive conditions. Pin-on-plate tests were performed with different loads, sliding velocity and abrasive particles. The material response was further investigated in a slurry containing abrasive test system with different sliding velocities and distances, abrasive media compositions and impact angles. The abrasive wear, the change of the 3D surface roughness parameters, the friction force and contact temperature evolution were also analyzed as a function of the materials' mechanical properties (H,E,sigma(y),sigma(c),epsilon(B),sigma(F),sigma(M)) and the dimensionless numbers derived from them. Using the IBM SPSS 25 software, multiple linear regression models were used to statistically evaluate the measured data and to examine the sensitivity of the material properties and test system characteristics on the tribological behavior. For both test setups, the system and material characteristics influencing the dependent variables (wear, friction, heat generation) and the dimensionless numbers formed from the material properties were ranked using standardized regression coefficients derived from the regression models. The abrasion sensitivity of the tested materials were evaluated taking into account a wide range of influencing parameters

New method for dynamic tribological test of engineering polymers

In this article, tribological tests of Polyamide 6 (PA 6), Ultra High Molecular Weight Polyethylene (UHMW PE) and Polyoxymethylene copolymer (POM C) by a new testing method is introduced. The tribometer used in the test is capable for pin-on-disc measuring within all possible layout known in tribology practice, otherwise can be modified into special model of fatigue sliding test. The pin was a specimen made from examined materials, always in contact with a rotating metal disc under a normal load, which is usually static. However, since vibration exists in every practical scene as an important phenomenon, for instance in turning process, we added vibration load into the test. The supplement load is generated by a special-designed vibrating machine. Then properties of examined materials can be studied more profoundly under vibration load. As a result, different value of friction coefficient in static and vibration load have been discovered and taken into comparison

Analysis of Vibration During Turning Process of Different Materials

In this article, we would like to introduce the problems caused by vibrations in case of polymer turning processes. Nowadays there is a lot of research in this topic, to avoid the unnecessary phenomena of vibrations. The two most common methods are the Spindle Speed Variation (SSV), and the Vibration Assisted Machining (VAM). In case of SSV, the CNC machine can increase and decrease the speed of spindle continuously during turning which can significantly reduce the effects of chatter. This method is beneficial for longer workpieces when there is not any support except the chuck. Vibration-assisted machining can be used to minimise the problems caused by vibrations. VAM combines precision machining with small-amplitude tool vibration to improve the fabrication process. It has been applied to some processes ranging from turning, drilling to grinding. Based on the enumerated above we made some trial measurements about the basic vibrations of the turning tool shank. The tests were done on an NCT EUROturn-12B CNC machine which can found in the workshop of our institute. The tested material was Polyamide 6 because this is the most commonly used polymer in the industry. In the future, we would like to test some other basic and composite polymer materials too. The equipment was served by a specialist from SPM Budapest Kft. With these tests, our goal was to make sure that the equipment and the measuring setup are suitable for our future research

Abrasive wear behaviour of 27MnB5 steel used in agricultural tines

Understanding the wear mechanisms in wear parts is a crucial element of tribological investigation, particularly in agricultural applications where the knowledge about abrasive micro-mechanisms of soil engaging tools are limited. In the current research, symmetrical skew wedge cultivator tines of 27MnB5 steel were wear tested to investigate the change in mass, linear dimensions, hardness and microstructure, aiming at prolonging the lifetime of these parts through design and material. The wear mechanisms were identified and characterized by non-contact 3D optical profilometry. Test results clearly shows a zone specific wear micro-mechanism based on the tine geometry. The cutting edge of the tine can be segmented into micro-cutting and micro-ploughing zone. Vickers hardness and microstructural analysis were performed on the cross-section of the sliding interface. Tribolayer was observed on the worn surface. Degree of penetration from the wear scratches was calculated to justify the wear micro-mechanisms. A Discrete Element Method (DEM) model was developed to investigate the soil flow during the tillage process. The model results and field test wear scars are in good agreement with each other with respect to the wear patterns

Abrasive slurry testing of different type of steels used in agricultural machinery

The aim of the current investigation is to identify a suitable material based on its wear performance for agricultural tines which currently uses alloyed martensitic steel 27MnB5. Low stress open three body abrasion is one of the wear mechanism in soil engaging tools. Slurry pot test was performed on candidate materials for experimentally simulating the ploughing action of the tine especially on the top surface which experiences abrasion from the flow of abrasive particles. The specimens were mounted on a rotating shaft which is eccentrically placed in a cylindrical container. The container was filled with an abrasive media Korund (Al2O3) with additional water forming the slurry. Samples extracted from the original tines were also included in these tests as reference material. Surface velocity (1-2 m/s) and ploughing depth (100 mm) was selected based on the real application. Change in specimen weight, dimensions, material hardness and surface morphology were studied. The surface of the contact area smoothened and experienced a polishing effect. The surface roughness reduced from Ra 0.3 to a Ra of 0.09 within 20 hours testing. Besides polishing hardening of the contact surface was evidenced where there is a relative increase in hardness of the worn zone compared to the unworn region. Beside the micro-cutting the impact angle of the particles influences the appearance of surface fatigue as pitting. The specimens set perpendicular to the flow of particles showed higher wear rate and experienced pitting as an additional mechanism. The pitting was present on the lower pressure region of the media. Among the tested materials martensitic steel (478 HBV, UTS 1523 MPa) performed best and was promoted for replacing the original material hence the high hardness of the martensitic microstructure leads to a better performance than the partly austenitic steel

Abrasive sensitivity of martensitic and a multi-phase steels under different abrasive conditions

The wear behaviour of two martensitic and one multiphase steel targeted for abrasion and erosion applications in agriculture and mining industry were investigated in three abrasive test systems with different complexity. Scratch tests were performed with different indenter radii, shapes, and loads. The material behaviour was also investigated in multi-asperity contact systems. Pin-on-disc tests were performed with various loads and abrasive particles, as well as abrasive slurry-pot tests with different sliding velocities, distances, and impact angles of the abrasive media were performed. Comparing the test systems, the tested materials ranked similarly based on their wear performance, however, in each configuration, the dominant variable of the wear mechanism differed. The significance and contributions of test paramecenterters, the material’s mechanical properties (H, σM, σY, E, εεM, εεB, W, σc, Ec) and the dimensionless numbers formed from them were investigated on the wear behaviour and the surface deformation. Correlation between parameters was established by multiple linear regression models. The sensitivity of the tested materials to abrasion was evaluated taking into account the wide range of influencing parameters

A Sequence of Phase Transformations and Phases in NiCoFeCrGa High Entropy Alloy

The present investigation is directed to phase transitions in the equimolar NiCoFeCrGa high entropy alloy, which is a mixture of face-centered cubic (FCC) and body-centered cubic (BCC) crystalline phases. The microstructure of the samples was investigated by using scanning electron microscopy (SEM), time-of-flight secondary ion mass spectroscopy (TOF-SIMS), transmission electron microscopy-based energy-dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS), as well as X-ray diffraction (XRD) measurements. Based on the phases observed in different temperature ranges, a sequence of the phase transitions can be established, showing that in a realistic process, when freely cooling the sample with the furnace from high to room temperature, a microstructure having spinodal-like decomposition can also be expected. The elemental mapping and magnetic behaviors of this decomposed structure are also studied