Depth-sensing nanoindentation, when the displacement the indenter is continuously monitored is widely used for analysis and estimations of mechanical properties of materials. Starting from pioneering papers by Bulychev, Alekhin, Shorshorov and their co-workers, nanoindentation tests are connected with Hertzian contact problems and the frictionless BASh relation is commonly used for evaluation of elastic modulus of materials. We discuss further the connections between Hertz type contact problems and nanoindentation tests and derive fundamental relations for depth-sensing nanoindentation for indenters of various shapes and for various boundary conditions within the contact region. For the loading branch, relations are derived among depth of indentation, size of the contact region, load, hardness, and contact area, using authors’ scaling formulae. The relations are valid for indenters of non-ideal shapes, whose shape function is a monomial function an arbitrary degree d , in particular for blunted pyramidal indenters when 1 < d < 2. We show that some uncertainties in nanoindentation measurements, which are sometimes attributed to properties of the material, can be explained and quantitatively described by properly accounting for geometric deviation of the indenter tip from its nominal geometry. Then relation is derived for the slope of the unloading branch of adhesive (no-slip) indentation. The relation is analogous the frictionless BASh relation and it is independent of the geometry of the indenter. Further, the JKR theory of contact the presence of forces of molecular adhesion is extended to describe contact between a monomial indenter of an arbitrary degree d and an elastic sample. Finally, some exact formulae are obtained for adhesive contact (both the no-slip contact and the contact in the presence of molecular adhesive forces) between indenters and isotropic, linear elastic materials. In particular, it is shown that the BASh formula is still valid for contact between a flat punch and a soft elastic sample in the presence of molecular adhesive forces (the Boussinesq-Kendall problem).

Examination of worn surfaces by optical, electron microscope detection and X-Ray diffraction analysis indicated that the replacement of the pin (steel 52100) by another pin (steel Stub 51115) facilitated and increased the influence of surface degradation which allows the sliding surface to be satisfactorily reactive to form high percentage of protective additive’s layers and to cover uniformly the whole wear track in boundary lubricated conditions. A few minutes of dry test well determined the production of the surface degradation to promote an optimal layer formation. The same type of tests were repeated using pin (sapphire) on the plate (steel Stub 51115) in order to be able to visualize the formation of layers. High speed camera has got images of layers and demonstrates the layer formation during experiment. This study suggests that the surface deterioration is a mechanical process and promotes chemical reactions at solid surfaces. Satisfactory degradation of the surface permits activating lubricant additives to form protective layers. The temperature has a significant chemical influence on the mechanical effect of the material type on the formation of additive’s layer.

Similar to the semiconductor sector improving processing power by decreasing device sizes, the information storage sector has been working to decrease device sizes in read/write heads. Chemical mechanical polishing (CMP) is a critical enabling technology for terabyte storage systems and other systems consisting of nanotechnology. A commercial CMP polisher was used, and the experimental material removal rates (MRR) are presented. Since the MRR is a function of the load, relative speed, and film hardness, a nano-indention technique was employed to characterize mechanical properties of the permalloy (NiFe) films. A basic MRR model was developed to compare to the experimental results.

The topography of a machined surface significantly influences the performance of both lubricated and unlubricated contacts. In this work the unlubricated frictionless contact of rough surfaces is the subject of study. The numerical deterministic contact mechanics model incorporates linear elastic surface material and the dry contact is simulated using classes of surface profiles randomly generated from a given Abbott curve (Abbott-Firestone bearing ratio curve). In this way all the height information of the surface profile is preserved and not only a few parameters, like R a , R q , R z , R sk , etc. The aim of this work is to investigate how classes of surfaces based on a single Abbott curve perform in terms of contact mechanical parameters like the real area of contact. The result shows that surfaces taken from a class of random surfaces generated from a specific Abbott curve behaves similar in a contact mechanics simulation. That is, the distribution of for example the real area of contact within such a class is compact, having a small deviation from its mean. This implies that it is possible to simulate classes of surfaces based on Abbott curves and to use the results to predict contact mechanical properties of real surface topographies.

This work was initially focused to analyze the onset of systematic fractures of car body parts (Ford Focus model) during stamping. Fractures were attributed to unexpected high values of friction between the tools and the steel sheets. All the sheets that failed fulfilled the required standard mechanical properties and topographical surface requirements (Ra between 1.0 and 1.7 μm and peak count Pc >50 peaks/cm, according to the German SEP 1940 standard), and were processed with the same lubricant. A detailed study of the surface features showed that, having similar and correct values of the conventionally used parameters for surface texture requirements, such as Ra and peak count Pc, those sheets that failed had some different asperity features, related to the asperity peak shape. Experimental work (measurement of real values of surface contact Sc and friction behavior under boundary lubrication conditions) confirmed that these differences in the asperity shape have an important effect on the friction behavior, controlling the rate of surface roughness flattening and therefore determining the real values of surface contact area and the remaining valley areas able to carry lubricant. The differences in asperity shape were reproduced in single roughness models and the flattening process of the asperities was simulated by finite element analysis. The agreement between simulation and experimental observation was excellent. The influence of asperity shape was found to be very important, justifying the real differences found in the values of real surface in contact and hence in the friction behavior during stamping real car body parts.

This work uses the finite element technique to model the elasto-plastic deformation of a hemisphere contacting a rigid flat for various material properties typical of aluminum, bronze, copper, titanium and malleable cast iron. Additionally, this work conducted parametric FEM tests on a generic material in which the elastic modulus and Poisson’s ratio are varied independently while the yield strength is held constant. A larger spectrum of material properties are covered in this work than in most previous works. The results are compared to two previously formulated elasto-plastic models simulating the deformation of a hemisphere in contact with a rigid flat. Both of the previously formulated models use carbon steel mechanical properties to arrive at empirical formulations implied to pertain to various materials. While both models considered several carbon steels with varying yield strengths, they did not test materials with varying Poisson’s ratio or elastic modulus. The previously generated elasto-plastic models give fairly good predictions when compared to the FEM results for various material properties from the current work, except that one model produces more accurate predictions overall, especially at large deformations where other models neglect important trends due to decreases in “hardness” with increasing deformation.

The determination of the mechanical properties using the nano or macroindentation test results was developed in order to predict the mechanical properties of materials such as thin or thick coatings [1]. In the present paper a new method using a continuous FEM supported simulation of the microindentation results through a special tester, is proposed in order to predict the stress–strain curve of various ferrous or non ferrous materials that are being used as constructive materials in several machines or devices. The elasticity modulus is determined using a large spherical indenter tip and the stress strain curve using smaller steel balls. In the case of three deferent ball diameter indenter tips, the adopted experimental-analytical methodology present similar results regarding the constitutive law of the examined steel or aluminum specimens.

In this study the effects of silica size (or specific surface area), mechanical properties and crosslink density on the wear of silica-filled SBRs (styrene butadiene rubbers) were examined. The modulus of each silica-filled SBR examined was proportional to crosslink density. The wear rate of silica-filled SBRs was reduced as the modulus and crosslink density increased. The wear rates increased as the specific surface area of the silica fill particles decreased, when the content of silane coupling agent was constant. As a result, the wear rate was shown to be lower as the modulus and crosslink density increased.

Among diamond-like carbon (DLC) coatings, hydrogenated amorphous carbon (a-C:H) coatings are of great interest since some of them may exhibit coefficients of friction in the millirange, so-called “superlow friction” in ultrahigh vacuum. However, there are still many points to be clarified and improved to employ them as solid lubricant for actual vacuum applications. For example, in space environment solid lubricants are required to function at both low and high temperature ranging from −150 to 100°C. To apply them as solid lubricant in such an extreme environment, it is necessary to know the evolution of the tribological behavior in temperature, leading to their application limit. Furthermore, tribological behavior of a-C:H coatings is known to depend on tribochemistry and on mechanical properties like viscoplasticity. Since both could be affected by temperature, a better understanding of superlow friction mechanisms is expected from experiments at various temperatures. In this present work, pin-on-disk reciprocating friction tests were conducted at various temperature conditions ranging from −130 to 300°C under ultrahigh vacuum (10 −7 Pa) to study the effect of temperature on the coefficient of friction of an a C:H coated flat mated against steel (AISI 52100) pins. For all temperatures, superlow friction regime could be reached, as it was observed usually at room temperature for this sample. However, an effect of temperature is evidenced on the duration of “running-in” phase, i.e. the number of cycles required to reach a superlow friction regime. The duration becomes shorter at higher temperatures and longer at lower temperatures. Also, the application limit in temperature is found between 200 and 300°C, at which the friction coefficient slowly increases after running-in, to reach values above 0.01. In light of these results, the mechanisms of superlow friction are discussed in terms of tribochemistry and mechanical properties of the coating.

From the point of view of the tribology of the touch quality, when one speaks about softness of an object, one very easily associates it his roughness, the friction and the mechanical properties of materials [1,2,3]. With regard to the human skin, the stratum corneum (SC), or cornea layer, is the part of skin surface, which is permanently requested during a friction test. In this work, we present a new approach developed in our laboratory, in order to understand the friction mechanisms of the human skin, and to identify the acoustic, signatures which can be correlated with the touch quality. The results show that the acoustic emission is correlated the stiffness and roughness of the stratum coreneum. The application to the analysis of ageing, show clearly the increase of acoustic emission during ageing of human skin.

We developed a second generation highly cross-linked UHMWPE by doping and stabilizing irradiated UHMWPE with the antioxidant vitamin E. With this stabilization method, the crystallinity of the irradiated polyethylene is not decreased as with melting, and hence mechanical properties and fatigue strength can be preserved. Vitamin E-doped, irradiated second generation highly cross-linked UHMWPE showed wear comparable to and higher strength and fatigue resistance than that of 100-kGy irradiated and melted first generation highly cross-linked UHMWPE.

Chameleon coatings are nanocomposite systems that adapt their tribological performance to changes in environmental conditions such as humidity and temperature. In this research we have investigated the tribological properties of two nanocomposite “chameleon” coatings and compared their properties. The two material systems of interest included: (i) Diamond like carbon (DLC) matrix with nanocrystalline WC and WS 2 inclusions, and (ii) Yttrium Stabilized Zirconia (YSZ) in an Au matrix with DLC and MoS 2 nanoparticle inclusions. The coating design approach included formation of nanocrystalline hard carbide or oxide particles for wear resistance, embedding them into an amorphous matrix for toughness enhancement, and inclusion of nanocrystalline and/or amorphous solid lubricants for friction adaptation to different environments. The coatings were produced using a combination of laser ablation and magnetron sputtering. Chemical and structural analysis of the coatings included x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, and micro-Raman spectroscopy. Mechanical properties such as coating hardness and toughness were investigated using nanoindentation, scratch, and indentation adhesion tests. It was observed that both YSZ and WC are valuable in enhancing film toughness. The chemical analysis was used to ascertain a correlation between chemical bonding of species and frictional properties. Friction measurements were studied by cycling between humid air and dry nitrogen conditions. The graphitic carbon component imparted low friction in humid air, MoS 2 and WS 2 were excellent for dry N 2 conditions, and Au was valuable for low friction at elevated temperatures. The direct comparison among coatings demonstrates that similar “chameleon” behavior can be achieved with different material systems, validating the universal nature of the design approach.

A novel quantitative nano+micro tribometer with integrated AFM and optical microscope has been utilized to characterize tribological and mechanical properties of liquid and solid thin films and coatings, with in-situ monitoring their changes during micro and nano indentation, scratching, reciprocating, rotating and other tribology tests.

Polymer derived ceramics (PDC’s) are processed from liquid organometallic precursors by cross-linking the polymers into infusible solids, followed by controlled pyrolysis. No previous work regarding their tribology has been reported. Further, the synthesis of PDC’s as thin films, and the role that the nanostructure plays on the mechanical properties has not been reported. The objective of this research was to evaluate the fundamental tribological behavior of polymer derived SiCN in both bulk and thin film form. Friction and wear evaluations were made on bulk materials and thin films using a Si 3 N 4 ballon-disk linear wear tester at various contact pressures and in different environments that contained various amounts of humidity. The micro/nanostructure was characterized by FTIR, microRaman, and scanning electron microscopy. Bulk SiCN gave a low friction coefficient and good wear resistance in humid environments but showed significant fracture and gouging in dry environments at higher contact pressures. Although there is ambiguity regarding the tribology of the thin films there seems to be a dependence upon the nitrogen content within the materials derived from the polymeric stage. The future work will focus on optimizing processing conditions of thin films and investigating the role that nitrogen plays in both bulk and thin film SiCN materials.

Some hydrogenated amorphous carbon (a-C:H) films have the peculiarity to exhibit coefficients of friction in the millirange, known as “superlow friction”, under inert environments like dry nitrogen or high vacuum. However, this “superlubricity” is only observed for some coatings and sometimes for very short duration. The role of tribofilm in the superlow friction regime observed on various a-C:H films sliding against steel pins has been investigated by performing experiments in ultra-high vacuum and hydrogen ambient. Tribofilm build-up appears to be controlled by interactions with oxide layers. Then, evolutions of the tribofilm will depend both on the composition of a-C:H film and on interactions with environment, through tribochemical reactions. Furthermore, the mechanical properties of the films are correlated with the achievement of superlow friction. All these results suggest that surface rheological properties are of critical importance in reaching superlow friction regime with a-C:H films.

Nanocomposite structures composed of hard and soft phases are very promising candidates for tribological applications involving both dry and lubricated sliding. This study aims to compare the wear behavior of copper doped hard nanocomposite nitride coatings under dry and lubricated sliding conditions. These nanocomposite coatings are produced in a cathodic arc-based hybrid PVD coating system and their mechanical and structural properties are fully characterized using electron microscopy and other relevant techniques. Tribological tests were performed in pin on disc and reciprocating wear test machines under dry and lubricated sliding conditions. The differences observed in the tribological behavior of nanocomposite coatings are discussed by taking into consideration the structure and mechanical properties of the coatings and the chemical character of the tribo films formed on sliding surfaces during wear testing.

A novel quantitative nano+micro-tribometer with integrated nanoindenter, SPM and optical microscope imaging has been used to characterize mechanical properties of Cu coated Si wafers at various test stages. A 2D Finite Element Model was developed to study changes on workhardened contacts assessed via nanoindentation experiments.

Nanostructured films offer potential for considerable improvements in mechanical properties by comparison with traditional single composition coatings. This nanostructuring can be carried out in many ways, but one of the easiest methods to implement it is through nanolayering with two or more phases. Alteration of the thickness of the different phases then permits the tailoring of the properties of the coating.

Gamma irradiation is used as a sterilization method for joint prosthesis. For this procedure, gamma irradiation causes crosslinking of UHMWPE. Crosslinked UHMWPE molecules connect each other strongly. However gamma irradiation causes the reduction in mechanical properties such as tensile strength and elongation because primary chain scission occurrs. Therefore, excessive irradiation would cause some problems. We suggest the existence of the optimum dose for minimum wear and moderate reduction in tensile strength and elongation. Furthermore we indicate a mechanism of wear resistance of gamma irradiated UHMWPE.

An AFM-based test station has been established for rapid mechanical and electrical characterization of contacts in a micromechanical switch. A wide contact force range is accessible, from nN to mN, determined by the mechanical properties of the microfabricated contact test cantilevers. During testing the contact force, deformation, and contact adhesion are measured. Periodic observations of material transfer are made. The cycling rate can reach 200 kHz.