Scratch Parameters Research Articles

Evaluation of Hardness and Elastic Modulus of Polymer Materials Through Micro-Scratch Method: An Empirical Study

ABSTRACT A number of researchers have focused on scratch methodologies to examine the surface properties of materials. Scratch testing is primarily employed to examine tribological behavior and coating failure. This study attempts to determine the hardness (H) and elastic modulus (E) of polymeric materials via the scratch method. The research performed a progressive loading scratch test on Poly-(ether-ether ketone) (PEEK), Poly(methyl methacrylate) (PMMA), Poly-tetra-fluoro-ethylene (PTFE), polyvinyl chloride (PVC), and High-density polyethylene (HDPE). The least-squares curve fitting model was used to develop two models for assessing the H and E of materials based on indentation and scratch parameters. The H is determined by tangential force, scratch width, residual depth, and E calculated from the recovered depth and additional scratch parameters. Validation of both models indicates a maximum error of around 5%, indicating that the recently established models align well with experimental data. This study presents two robust models for assessing material surface attributes derived from a single scratch test with additional parameters.

Scratch geometry effects on lubrication and performance of two-lobe journal bearings: A detailed study

Scratches on bearing surfaces can significantly affect the performance and lifespan of journal bearings. This study investigates the impact of scratches on two-lobe journal bearings through both theoretical and numerical analyses. The theoretical approach provides insights into how scratches influence lubrication, while the numerical simulations investigate how the three key scratch parameters, namely width, position, and depth, affect bearing performance. Key metrics analyzed include pressure, velocity distributions, temperature profiles, eccentricity, attitude angle, minimum film thickness, and maximum temperature. The findings offer valuable guidance for optimizing bearing design, maintenance, and condition monitoring, contributing to enhanced reliability and operational efficiency.

Advancements in Polymer Friction and Wear: A Scratch-Modeling Approach

Due to its many applications, including assessing strength, fracture toughness, and so on, the scratch method has attracted much attention in the research community. Finding the tribological characteristics of polymers, such as friction and wear, proved difficult for scratch approaches. This study tested a constant loading scratch method with a Rockwell indenter on the polymeric surface to develop an accessible wear and friction calculation model. Scratch load, speed, and passes, three primary factors, are considered to observe the polymers' response, particularly in terms of width, penetration depth, residual depth, and percentage of recovery. Considering all these scratch parameters, the experiments were conducted on five polymers: polytetrafluoroethylene (PTFE), polyether ether ketone (PEEK), polypropylene (PP), high-density polyethylene (HDPE), and polymethylmethacrylate (PMMA). The scratch characteristics are considered to calculate the friction coefficient and wear throughout the scratching process. Increased groove width, penetration depth, and residual depth and a decrease in recovery percentage are the effects of the number of scratch passes. The strain hardening caused by the multiple movements of the indenter on the same grooves causes a behavior change. With an increase in the scratch pass, the coefficient of friction decreases and stabilizes, and the volumetric wear increases, suggesting that more scratch passes will cause more material loss. This study derived two distinct models by applying the least-square curve fitting technique to evaluate friction and material wear characteristics. This model demonstrates a high degree of compatibility with the specific characteristics of polymeric materials and exhibits a significantly low margin of error.

The Influence of Scratches on the Tribological Performance of Friction Pairs Made of Different Materials under Water-Lubrication Conditions

Water-lubricated bearings are widely used in marine equipment, and the lubricating water often contains hard particles. Once these particles enter the gap between the bearing and the shaft, they can scratch the smooth surfaces of the shaft and bearing, influencing the working performance of the bearing system. To investigate the effect of scratch parameters on tribological performance, this paper conducts multiple block-on-ring experiments and constructs a mixed-lubrication model under water-lubrication conditions. The results show that among the three commonly used bearing materials, the tribological performance of graphite block is the most sensitive to scratches on the test ring surface. Under the condition of one scratch (N = 1), the loading area of water film pressure is divided into two separate zones (a trapezoidal pressure zone and an extremely low-pressure zone). In addition, the variation of maximum water film pressure is determined by the positive effect (hydrodynamic pressure effect of fluid) and negative effect (“piercing effect” of the asperities). Compared with the scratch depth and scratch location, the scratch width has the most significant effect on the tribological performance of the block-on-ring system. The maximum contact pressure is located at both edges of the scratch due to the formation of a water sac structure. The scratch has a great influence on the transition of the lubrication state of the block-on-ring system. The existence of scratches increases the critical speed at which the lubrication state transits from mixed-lubrication to elastohydrodynamic lubrication, and the critical speed is directly proportional to the scratch width.

Prediction of Friction Coefficients During Scratch Based on an Integrated Finite Element and Artificial Neural Network Method

Abstract An integrated finite element and artificial neural network method is used to analyze the impact of scratch process parameters on some variables related to elastoplastic deformation of titanium alloy. The elastoplastic constitutive parameters applied for scratch simulations are obtained from the nanoindentation experiments and finite element analysis. The validity of the finite element model of scratch is confirmed by comparing the friction forces from simulations to those from experiments. The input parameters of the artificial neural network are three scratch process parameters: tip normal force, tip radius, and shear friction coefficient. The outputs are four variables related to material deformation measured during scratch: scratch depth, elastic recovery height, plowing height, and plowing friction coefficient. The network is trained with pairs of input and output datasets generated by scratch simulations. The prediction results of the neural network are in agreement with the finite element results. The model provides assistance for the prediction and analysis of complex relationships between scratch process parameters and variables related to material deformation, and between the plowing friction coefficient and the relevant parameters. The results show the independence of scratch depth and the shear friction coefficient, and the positive relationships between the shear friction coefficient and plowing friction coefficient.

Surface deformation and friction characteristic of nano scratch at ductile-removal regime for optical glass BK7.

Nano scratch for optical glass BK7 based on the ductile-removal regime was carried out, and the influence rule of scratch parameters on surface deformation and friction characteristic was analyzed. Experimental results showed that, with increase of normal force, the deformation of burrs in the edge of the scratch was more obvious, and with increase of the scratch velocity, the deformation of micro-fracture and burrs in the edge of the scratch was more obvious similarly. The residual depth of the scratch was measured by atomic force microscope. The experimental results also showed that, with increase of normal force, the residual depth of the scratch increased linearly while the elastic recovery rate decreased. Furthermore, with increase of scratch velocity, the residual depth of the scratch decreased while the elastic recovery rate increased. The scratch process of the Berkovich indenter was divided into the cutting process of many large negative rake faces based on the improved cutting model, and the friction characteristic of the Berkovich indenter and the workpiece was analyzed. The analysis showed that the coefficient of friction increased and then tended to be stable with the increase of normal force. Meanwhile, the coefficient of friction decreased with the increase of scratch velocity, and the coefficients, k ln(v) and μ0, were introduced to improve the original formula of friction coefficient.

Nanoscratch characteristics and interfacial adhesion energy of SiN/GaAs film/substrate bilayer systems

Deformation characteristics and interfacial adhesion property of silicon nitride/gallium arsenide film/substrate systems were investigated by use of nanoscratch. During scratching, three different types of deformation, elastic, elastoplastic and fracture, were discovered. The critical loads for film failure were obtained. The critical loads, together with the other scratch parameters, were used to determine the interfacial adhesion energies. The practical adhesion energies per unit area of the bilayers obtained were 2.72 and 3.73 Joules/m2, respectively. The tensile stress developed just behind the contact area and at the interface was attributed to the film failure. It was also found that residual compressive stress strengthened, but tensile stress weakened the interfacial adhesion.

Evaluation of anti-scratch properties of graphene oxide/polypropylene nanocomposites

Graphene oxide/polypropylene (GO/PP) nanocomposites were fabricated by varying the concentration of GO in the presence of octyltriethoxysilane (OTES) using an internal batch mixer to enhance the anti-scratch properties of pristine PP. Mechanical properties, including hardness, elastic modulus, and fracture toughness, of the prepared GO/PP nanocomposites were analyzed by nanoindentation. As a compatibilizer, OTES increased dispersibility, interfacial interactions, and mechanical interlocking between the GO nanofiller and the PP matrix, improving mechanical strength. A 286% increase in hardness, 127% improvement of elastic modulus and 117% enhancement on fracture toughness are achieved by addition of only 1.0 wt% of GO and OTES. For scratch tests, several GO/PP nanocomposite samples were analyzed according to various scratch parameters. Furthermore, scratch hardness, elastic recovery, and tangential forces acting on the scratch probe were investigated to provide insight into scratch behavior. The outstanding resistance to scratch deformation such as a maximum increase in scratch hardness of 189% was likely due to the excellent mechanical properties of the GO/PP nanocomposites.

Effect of the substrate and interface on micro-scratch deformation of epoxy-polyester powder coatings

The role of the interface on the deformation response in scratch tests of epoxy-polyester films deposited by electrostatic spraying is investigated. A comparative study of the scratch deformation behaviour of films deposited on micro- and macro-corrugated rigid substrates and on ‘soft’ silicon sub-layers is made. Scratch deformation parameters were evaluated by contact gauge inductive profilometry, whilst morphological examinations of the residual scratch patterns were performed by electron microscopy.3-Response models based on a 2-D and 3-D reconstruction of the scratch pattern during the application and after the release of the load were used to perform the deformation response analysis and calculate the key geometrical features of the residual scratch patterns. In particular, the influence on the residual scratch patterns of the applied loads, sliding speeds, contact geometries, and the test modes were looked into.

Optimization of the Scratch Test for specific coating designs

The proper design of wear resistant coatings applied to cutting tools comprises the optimization of the mechanical properties (Young's modulus, yield strength, adhesion, intrinsic stresses, fracture, fretting etc.) of the coating-tool system. The goal is to find material and structural solutions which keep the resulting stress–strain field under typical application conditions below the stability limits of the system. Based on nanoindentation measurements obtained from the coating-tool system which should be optimized, a scratch test is dimensioned with respect to load range and indenter geometry. The measured data from this “Physical Scratch Test” are used to simulate spatial stress profiles and to calculate the von Mises stress characteristics and the maximum normal stresses in the scratch direction. In a further step, the simulations are used to suggest scratch parameters for a “Fine Tuned Scratch Test” which increase the sensitivity of the test for specific depth regions in the coating-tool architecture and allow improved and more sensitive investigations of critical interfaces, transition layers and surface-near substrate regions. The tests were performed at PVD coated inserts (nitrides and oxides) and compared with the results obtained from cutting tests.

A comparison study of scratch and wear properties using atomic force microscopy

The patterning technique that uses an AFM (atomic force microscopy) tip as a scratch tool, also known as AFM scratching, has been a vital technique for nanofabrication because of its low cost and potential to reach a resolution into the sub-nanometer domain. The AFM scratching technique was first used to study the scratch characteristics of silicon, with an emphasis on establishing its scratchability or the nanoscale machinability. The effects of the scratch parameters, including the applied tip force and number of scratches, on the size of the scratched geometry were specifically evaluated. The primary property that measures the scratchability was identified and assessed. To illustrate its suitability and reliability, the value of the scratchability, based on the present Si scratching experiments, was compared with the values based on the data available in the literatures for different scratching conditions or for materials other than Si. Since AFM scratching is in some aspects similar to the nanoscale wear test, the scratchability property identified is also compared with two major wear resistance indicators, wear coefficient and hardness. All comparison results indicate that the scratchability property identified, the scratch ratio, is an appropriate manufacturability indicator for measuring the degree of the ease or difficulty of a material scratched by an AFM tip and more suitable than the wear coefficient and hardness to gauge the nanoscale AFM scratchability.

Scratch properties of nickel thin films using atomic force microscopy

Experiments using atomic force microscopy (AFM) as a machining tool for scratching patterns on nickel thin films have been conducted with an emphasis on establishing the material scratchability or more general, the nanoscale machinability. The effects of the scratch parameters, including the applied tip force and scratch direction, on the size of the scratched geometry were investigated. The primary factors that measure the scratchability were then assessed. The scratchability of Ni as compared to that of Si was specifically evaluated and discussed. A stress-hardness analysis was also performed to further validate the experimental and correlation results. All results indicate that the Ni thin film possesses excellent scratchability and one order of magnitude higher than that of Si. Based on the correlation formula developed, Ni should be able to be precisely scratched by AFM tip with the required dimension and nanoscale accuracy and precision.

Scratching properties of nickel-iron thin film and silicon using atomic force microscopy

Atomic force microscopy (AFM) is well known for its ability for nanopatterning many different materials. The patterning technique using an AFM tip as a scratch tool, known as scratch nanolithography, is used to study the scratch characteristics of 80% Permalloy thin film and silicon, with the emphasis on establishing their scratchability or the nanoscale machinability. The effects of the scratch parameters, including the applied tip force, scratch speed, and number of scratches, on the size of the scratched geometry were specifically evaluated. The primary factors that measure the scratchability were then identified and the governing material properties for scratchability were evaluated. To demonstrate its versatility, the scratching technique was applied to fabricate a NiFe-based nanoconstriction, which is used for many ferromagnetic devices. All results indicated that NiFe thin film has much better scratchability than that of Si and the scratched groove geometry can be accurately correlated with and precisely controlled by the tip normal force.

Effects of filler type and content on mechanical properties of photopolymerizable composites measured across two-dimensional combinatorial arrays

Multicomponent formulations coupled with complex processing conditions govern the final properties of photopolymerizable dental composites. In this study, a single test substrate was fabricated to support multiple formulations with a gradient in degree of conversion (DC), allowing the evaluation of multiple processing conditions and formulations on one specimen. Mechanical properties and damage response were evaluated as a function of filler type/content and irradiation. DC, surface roughness, modulus, hardness, scratch deformation and cytotoxicity were quantified using techniques including near-infrared spectroscopy, laser confocal scanning microscopy, depth-sensing indentation, scratch testing and cell viability. Scratch parameters (depth, width, percent recovery) were correlated to composite modulus and hardness. Total filler content, nanofiller and irradiation time/intensity all affected the final properties, with the dominant factor for improved properties being a higher DC. This combinatorial platform accelerates the screening of dental composites through the direct comparison of properties and processing conditions across the same sample.

Fabrication of metal oxide nanostructures based on Atomic Force Microscopy lithography

Atomic Force Microscopy (AFM) mechanical lithography is a simple but significant method for nanofabrication. In this work, we used this method to construct nanostructures on Pt/Cu bilayer metal electrodes under ambient conditions in air. The influence of various scratch parameters, such as the applied force, scan velocity and circle times, on the lithography patterns was investigated. The Pt-Cu-Cu x O-Cu-Pt nanostructure was constructed by choosing suitable scratch parameters and oxidation at room temperature. The properties of the scratched regions were also investigated by friction force microscopy and conductive AFM (C-AFM). The I–V curves show symmetric and linear properties, and Ohmic contacts were formed. These results indicate that AFM mechanical lithography is a powerful tool for fabricating novel metal-semiconductor nanoelectronic devices.

Effect of aluminium grain size on scratch resistance for spherical and conical indenter

PurposeThe purpose of this paper is to study the correlation between abrasive wear resistance, contact configuration and grain size of aluminium alloy.Design/methodology/approachDifferent aluminium alloy with different grain size has been tested using a scratch test. Comparison between scratch parameters, especially scratch depth and grain size aluminium alloy, has been made. Two indenters were used: conical and spherical indenter.FindingsCorrelation between grain size of aluminium alloy, configuration contact and abrasive wear resistance has been discussed. This study can be useful for choosing material which can provide better abrasive wear resistance.Originality/valueThis study can be a reference both practically and academically. A similar study has been made in order to investigate the effect of hardness in abrasive wear resistance. However, the importance of microstructure and especially the grain size of aluminium alloy have been taken into account.

Susceptibility to scratch damage of high density polyethylene coating

The scratch behaviour of a polymeric coating, based on high density polyethylene (HDPE), used for pipeline application was investigated in this work. Instrumented scratch testing was used for the characterization of the friction and wear behaviour of such materials. Static contact of a diamond conical indenter against the polyethylene (PE) coating was experimentally studied. Normal and tangential forces are measured during the scratch experiments using various scratch parameters (such as sliding velocity, attack angle, applied normal load). All the experiments were performed under unlubricated conditions and at room temperature. Moreover, some hygrothermally aged coating samples were considered in order to analyze the effect of immersion aging on their scratch behaviour. Before being subjected to scratch experiments, these samples were immersed in synthetic sea water at a set temperature of 70 °C and for 6 months. The scratch behaviour of the polymeric coating was discussed in terms of friction coefficient, wear resistance and wear mechanisms. Thus, scratch tracks were analyzed qualitatively and quantitatively. To characterize the scratch process, three-dimensional topography of the scratched surfaces was measured. In fact, wear morphologies of the PE coating were observed after scratching by tactile profilometer and laser interferometer. Friction response was correlated to wear mechanisms. Wear volume can be considered relevant responses to describe the material's scratch resistance. It was found that friction and wear behaviours are significantly affected by scratch parameters. Hygrothermal aging considerably affects the wear resistance of the studied coating. In terms of wear mechanisms, the ploughing controls the wear of such PE coating whole the retained test conditions.

On the combined use of scratch tests and CLA profilometry for the characterization of polyester powder coatings: Influence of scratch load and speed

The prediction of the mechanical properties of polyester powder coatings is of paramount importance, as they have to undergo a wide variety of forces and deformations during their service life. Determine the response of polymeric coatings to the actual loading conditions can be, however, very troublesome as their properties are function of the material physical state, rate-dependence and yield and break behaviour. Further, the characterization of soft, contaminated organic surfaces such as polymers can often cause severe problems with reliability and imaging accuracy due to instrumental artefacts. This is therefore the context in which this paper investigates the capability of multiple parameters scratch tests joined with non-contact CLA profilometry and FE-SEM to detect the scratch response of polyester powder coatings for protective and decorative outdoor applications. Scratch tests with blunt contact geometry were used to evaluate the response of polyester coatings baked at different time–temperature programs and, so, at different stages of their curing process. In particular, being such coatings highly non-linear in their response to mechanical stress or strain, the influence from scratch load and speed was carefully taken into account. Analytical evaluations of the experimental results led to good correlations between the extent of the deformed zone after scratch, scratch parameters and curing operational settings. This allows mapping the scratch response of the polyester topcoats to broad ranges of both scratch parameters and curing conditions.

Effects of molecular weight and thermal history on scratch behavior of polypropylene thin sheets

The effects of molecular weight ( M w) and thermal history on the scratch behavior of polypropylene (PP) thin sheets and a commercial thermoplastic olefin (TPO) have been investigated. Scratch parameters like the critical load for onset of scratch visibility and scratch coefficient of friction (SCOF) were utilized in this evaluation. The results suggest that scratch performance is improved when the M w and surface crystallinity of PP are high. Correlation between scratch resistance and surface crystallinity of PP is established and discussed. Approaches for the preparation of scratch-resistant TPOs are also addressed.

Nanohardness and Crack Resistance of HTS YBCO Thin Films

Nanoindentation and nanoscratching using atomic force microscope (AFM) were employed to study the local mechanical properties of high TC superconductors YBCO thin films featuring high critical current density. Two YBCO films sputtered on two different substrates featuring substantial different hardness and Young's modules (sapphire and SrTiO3) were studied. The microstructure and the mechanical properties such as hardness (H), Young's modulus (E) and scratch parameters were investigated. The intrinsic hardness and Young's modulus of YBCO thin films were found to be H /spl sim/ 8.5 GPa, and E /spl sim/ 210 GPa, respectively. The substrate's influences on the mechanical parameters were found to be insignificant as long as the indentation penetration depth was below approximately 25% of the film thickness.