Characterization of Counter-Surface Substrates for a Laboratory Abrasion Tester (LAT100) Compared with Asphalt and Concrete to Predict Car Tire Performance

Tire performance is determined based on the interaction between the tire and the road as a counter-surface, and is of the utmost importance for driving safety. When studying tire friction and abrasion, the characteristics of the roads/counter-surfaces are crucial. The excitations on the tire come from the road asperities. A proper characterization of the counter-surface texture is, therefore, an absolute necessity in order to optimize tire performance. The present study provides the required knowledge over the counter-surfaces employed as common substrates in a Laboratory Abrasion Tester (LAT100), which are typically based on embedded corundum particles for dry/wet friction and abrasion experiments. All surfaces are scanned and characterized by laser microscopy. The surface micro and macro roughness/textures are evaluated and compared with asphalt and concrete as the real roads by power spectral densities (PSD). The reliability of the high-frequency data based on the device type should be considered carefully. The reliable cut-off wavenumber of the PSDs is investigated based on image analyses on the range of tested frequency for micro and macro textures obtained by optical scanning devices. The influence of the texture wavelength range on the rubber−surface interaction is studied on a laboratory scale.

Understanding Test Modalities of Tire Grip and Laboratory-Road Correlations with Modeling

The present study is meant to obtain tribological insight into the interface of a rolling rubber wheel on a counter-surface disk based on the work of the previous study Salehi et al. (Tribol Lett 68(1):37, 2020), in which a new test method was developed to rapidly predict tire grip in a laboratory environment. A Laboratory Abrasion Tester (LAT100) was used and exploited as a tribometer. This opened a new cost- and time-effective horizon for tire material development in a laboratory environment rather than having to test tread compounds by building full-scale tires. The method was validated by a comprehensive study for six different tire tread compositions, by correlating the laboratory data for solid rubber wheels as LAT100 specimens with real tire results in two test modalities: lateral (α) and longitudinal (κ) sweep tests on a dry road. It was demonstrated that the LAT100 can be exploited to simulate the $$\alpha$$ α -sweep tire tests, but not the $$\kappa$$ κ -sweep. The dynamics and physics of a rolling rubber wheel on a counter-surface disk of the LAT100 test step-up are investigated utilizing the renowned physical “brush model” in comparison to full-scale tire tests. The type of test modality leads to different friction mechanisms in the contact patch even at similar test conditions. This is substantiated by recognizing the two regions: stationary and non-stationary, in the contact area which results in different friction components and mechanisms. The behavior of the rolling wheel in lateral and longitudinal movements at the same test conditions is comparable if the contributions of the mentioned regions in the contact area are similar.

An investigation on the tribological and mechanical properties of silicone rubber/graphite composites

In this study, tribological properties and surface characteristics of silicone rubber/graphite (QMG) composites were investigated as a function of applied load, sliding velocity (1–5 m/s) and temperature. This study discusses a novel approach to improve the tribological properties of silicone rubber (QM). Inclusion of graphite significantly reduces the friction coefficient (̴40%) and specific wear rate of QM (50%). Wear mechanism involves formation of transfer film at the interphase between composite and steel counter surface. Tribological performance of QMG composites were found to be in agreement with its morphological, mechanical and dielectric properties.

Control of Head Smear Generated From DLC Films Using an External Electric Field

In this study, the dependence of the electric field between the magnetic disk and Si wafer, used as the counter surface, on the hydrocarbon smear generated from the diamond-like carbon (DLC) overcoat was investigated. As a result, the positive electric field from the disk to the Si wafer increased the amount of smear, and the negative field reduced it. The positive electric field was estimated to extract hydrocarbon ions from the thermal plasma toward the Si wafer, and the opposite field attracts the hydrocarbon ions to the DLC surface. Therefore, the electric field between the slider and disk possibly controls the smear generation from the DLC overcoat, which is heated by laser irradiation in the heat-assisted magnetic recording).

Better Surface Integrity and Tribological Properties of Steel Sintered by Powder Metallurgy

The current research reports the improvement in surface integrity and tribological characteristics of steel prepared using a powder metallurgy (PM) by ultrasonic nanocrystal surface modification (UNSM) at 25 and 300 °C. The surface integrity and tribological properties of three samples, namely, as-PM, UNSM-25 and UNSM-300 were investigated. The average surface roughness (Ra) of the as-PM, UNSM-25 and UNSM-300 samples was measured using a non-contact 3D scanner, where it was found to be 3.21, 1.14 and 0.74 µm, respectively. The top surface hardness was also measured in order to investigate the influence of UNSM treatment temperature on the hardness. The results revealed that the as-PM sample with a hardness of 109 HV was increased up to 165 and 237 HV, corresponding to a 32.1% and 57.2% after both the UNSM treatment at 25 and 300 °C, respectively. XRD analysis was also performed to confirm if any changes in chemistry and crystal size were took place after the UNSM treatment at 25 and 300 °C. In addition, dry tribological properties of the samples were investigated. The friction coefficient of the as-PM sample was 0.284, which was reduced up to 0.225 and 0.068 after UNSM treatment at 25 and 300 °C, respectively. The wear resistance was also enhanced by 33.2 and 52.9% after UNSM treatment at both 25 and 300 °C. Improvements in surface roughness, hardness and tribological properties was attributed to the elimination of big and deep porosities after UNSM treatment. Wear track of the samples and wear scar of the counter surface balls were investigated by SEM to reach a comprehensive discussion on wear mechanisms. Overall, it was confirmed that UNSM treatment at 25 and 300 °C had a beneficial effect on the surface integrity and tribological characteristics of sintered steel by the PM that is used in a shock absorber for a car engine.

Abrasive Wear Mechanism of Microwave-Assisted Compression Molded Kenaf/HDPE Composite

The present work aims to study the abrasive wear of kenaf/high-density polyethylene (HDPE) composites with 20% weight fraction reinforcement of the kenaf fiber. A unique technique of the microwave-assisted compression molding (MACM) was used to fabricate the composites. The pin-on-disc setup was used for two-body abrasive wear, in which the kenaf/HDPE composite acts as a pin and the abrasive paper (P100) acts as a counter surface. Two-body abrasive wear tests were conducted for HDPE and kenaf/HDPE composites at normal loads of 10 N, 20 N, and 30 N and the sliding speed of 1 m/s, 2 m/s, and 3 m/s within 100 m of sliding distance. Tribofilm formation was observed at higher values of load and speed, which helps in reducing the wear-rate of the composites. Wear mechanism of the kenaf/HDPE composite is discussed in detail and supported with scanning electron microscope (SEM) fractography.

Validity of Amontons’ law for run-in short-cut aramid fiber reinforced elastomers: The effect of epoxy coated fibers

Friction between two contacting surfaces is studied extensively. One of the known friction theories is Amontons’ law which states that the friction force is proportional to the normal force. However, Amontons’ law has been found to be invalid for elastomers. In the present study, the validity of Amontons’ law for short-cut aramid fiber reinforced elastomers is studied. Two types of fillers are used to reinforce the elastomers, namely highly dispersible silica and short-cut aramid fibers. Short-cut aramid fibers with two different surface treatments are used, namely non-reactive fibers with standard oily finish (SF-fibers) and fibers treated with an epoxy coating (EF-fibers). A pin-on-disc tribometer is used to investigate the frictional behavior of the composites in sliding contact with a granite counter surface. The results show that, after the run-in phase, Amontons’ law is valid for those composites that are reinforced by short-cut aramid fibers (without reinforcing filler, i.e., silica) if the contact pressure is below a threshold value. However, once the contact pressure exceeds this threshold value, Amontons’ law will be invalid. The threshold contact pressure of the composites containing EF-fibers is higher than of the composites containing SF-fibers. The composites that are reinforced by silica and short-cut aramid fibers do not follow Amontons’ law.

Fabricating Laser-Induced Periodic Surface Structures on Medical Grade Cobalt–Chrome–Molybdenum: Tribological, Wetting and Leaching Properties

Hip-implants structured with anti-bacterial textures should show a low-friction coefficient and should not leach hazardous substances into the human body. The surface of a typical material used for hip-implants, namely Cobalt–Chrome–Molybdenum (CoCrMo) was textured with different types of laser-induced periodic surface structures (LIPSS)—i.e., low spatial frequency LIPSS (LSFL), hierarchical structures consisting of grooves superimposed with high spatial frequency LIPSS (HSFL) and Triangular shaped Nanopillars (TNP)—using a picosecond pulsed laser source. The effect of LIPSS on the wettability, friction, as well as wear of the structures, when slid against a polyethylene (PE) counter surface and biocompatibility was analyzed. Surfaces covered with LSFL show superhydrophobicity and grooves with superimposed HSFL, as well as TNP, show hydrophobic behavior. The coefficient of friction (CoF) of LIPSS against a polyethylene (PE) counter surface was found to be higher (ranging from 0.40 to 0.66) than the CoF of (polished) CoCrMo, which was found to equal 0.22. It was found that the samples release cobalt within biocompatible limits. Compared to polished reference surfaces, LIPSS cause higher friction of CoCrMo against PE contact. However, the wear of the PE counter surface only increased significantly for the LSFL textures. For these reasons, it is concluded that LIPSS are not suitable for a heavily loaded metal-on-plastic bearing contact.