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With the pursuit of high-precision and high-efficiency machining, laser-assisted machining technology has attracted more and more attention. Especially, ultra-short pulse laser irradiation can facilitate a quite high cooling rate and produce a local active space, which can make the surface modification realized without any removal. In this study, a novel tribo-characteristic improvement technology using ultra-short pulse laser irradiation in oil, with the hydrocarbon composition in oil as a carbon source, was proposed, to realize the surface modification of the workpiece in the same process with machining. Herein, a Ti-6Al-4V disk was irradiated using a pico-second laser in PAO oil under 4 different conditions with changed effective irradiated laser pulses and scanning modes. Besides the uniform laser irradiation, patterning irradiation was also conducted. From the results of the reciprocating friction tests, compared to those uniformed irradiated specimens, patterning irradiation processed surfaces show obviously more stable friction than the as-received metal surface. More importantly, much longer lifetime has been obtained, indicating the enhanced wear resistance. According to the investigation of hardness distribution, laser-induced thermal strain in the patterning irradiation method is considered to be an important factor of wear resistance improvement.

Pulse laser grinding (PLG), an edge-shaping process, was developed previously to implement high-performance cutting tools. In this study, two femtosecond (fs) lasers with wavelengths of 1045 nm and 257 nm were used to conduct PLG on chemical vapor deposited (CVD) diamond-coated tool edges, as the fs laser is reported to have less thermal impact and the potential to improve the material crystallinity. We investigated the effects of the laser parameters on the tool edge formation and microstructural changes. The results show that although the infrared fs laser could – compared to the conventional nanosecond (ns)-laser PLG – naturally suppress surface thermal damage, the roughness of the processed surface remained relatively high with an Rz of 0.21 μm. However, under the optimal laser parameters proposed in this paper, an ultraviolet fs-laser PLG was used to obtain a much smoother edge, reducing Rz to approximately 0.08 μm. Moreover, scanning electron microscopy images indicated that the longitudinal machining marks on the ns-laser-processed surface were significantly reduced, with virtually no attached debris on the surface. Furthermore, from the Raman spectra, a significant increase in the diamond peak intensity was observed, indicating that the crystallinity of the CVD diamond (CVDD) was improved following ultraviolet-fs-laser PLG. These results demonstrate that edge shaping and structural modification of polycrystalline CVDDs can be integrated into ultraviolet-fs-laser PLG.

In this paper, we propose a surface integrity technique referred to as pulse laser grinding (PLG). This method is a combination of laser ablation and averaging processes, such as grinding, and has two characteristic features. The first feature is that the irradiation area consists of a long-focus lens and a pulse laser with a Gaussian profile, and this method has a laser irradiation area equivalent to that of the grinding wheel. However, owing to the difference in the removal process of PLG and that of conventional grinding, the surface roughness after processing is expected to be different. The second feature is that the workpiece is placed at an approximately parallel angle between the laser axis and the work surface to undergo laser ablation on the surface. The characteristic piece placement restrains laser-specific problems such as debris and redeposition. This study targets sintered tungsten carbide (WC-Co), for which it is particularly difficult to form low-roughness surfaces. Binder removal followed by WC grain detachment caused by conventional grinding contributes to the increase in roughness and deterioration of corner sharpness. The experimental results of PLG with a sufficiently averaged surface of a WC-Co tool confirmed that the parallel roughness reached an arithmetical mean roughness (Ra) of 0.025 μm, and the perpendicular roughness reached Ra below 0.006 μm, in agreement with the aforementioned considerations.

Adhesion is one of essences with respect to rubber friction because the magnitude of the friction force is closely related to the magnitude of adhesion on a real contact area. However, the real contact area during sliding depends on the state and history of the contact surface. Therefore, the friction force occasionally exhibits rate-, state-, and pressure dependency. In this study, to rationally describe friction and simulate boundary value problems, a rate-, state-, and pressure-dependent friction model based on the elastoplastic theory was formulated. First, the evolution law for the friction coefficient was prescribed. Next, a nonlinear sliding surface (frictional criterion) was adopted, and several other evolution laws for internal state variables were prescribed. Subsequently, the typical response characteristics of the proposed friction model were demonstrated, and its validity was verified by comparing the obtained results with those of experiments conducted considering the contact surface between a rough rubber hemisphere and smooth acrylic plate.

In the metal cutting, generally, application of lubricant to a cutting edge is one of the methods in order to suppress temperature rise of the cutting edge by reducing frictional heat. However, the reduction in friction with lubricant disappears at higher temperature environment because of the loss of lubricant oiliness associated with temperature rise. Conversely, this reduction effect might work only in the initial stage immediately after cutting edge /work engagement because the temperature is not so high. Therefore, if the cutting duration of each blade of end-mill is shorten by limiting the cutting length per once, the cutting temperature can be suppressed to be lower than the moderate magnitude for lubrication. On the other hand, Ti-alloys with low thermal conductivity would experience quite high temperature increase during the high-speed cutting process. Therefore, it is thought that lubricant cannot be used properly with conventional cutting methods. In this study, the high-speed milling method mentioned above was used to implement the machining of Ti-alloys, and the lubricant effects of different types oils were compared from two aspects as tool wear and cutting force. As a result, when using low-viscosity synthetic ester oil, the damage to the cutting edge was suppressed most. At the same time, there was no fluctuation in cutting force by repeated machining. From this result, it was suggested that the lubricant performance, in intermittent cutting with very short cutting duration, depends on the heat resistance and permeability of the oil.

To deepen the understanding of the frictional sliding phenomena of rough surfaces, advances are required in numerical analysis methods at various spatial scales. In this study, to examine the microscopic behavior of a rough asperity contact corresponding to a bulk contact on the macroscopic scale, a loop-type meso–macro coupled analysis scheme is proposed. A mesoscale numerical model and a macroscopic friction model are required for the proposed multi-scale analysis. A friction model was adopted based on the multipoint contact model for the mesoscale model, and the pressure- and state-dependent elastoplastic analogy friction model was used for the macroscale model. In the proposed meso¬¬–macro coupled analysis, the parameter set for the elastoplastic analogy friction model was first identified via a numerical friction test using the mesoscale multipoint contact model assuming various conditions. Then, a macroscale finite element analysis incorporating the elastoplastic analogy friction model was performed for the macroscopic analysis of contact between a rough rubber hemisphere and a smooth plate. Here, the information from the mesoscale rough surfaces were reflected in the macroscale finite element analysis. Finally, a mesoscale localization analysis was performed in which the macroscopic histories of several typical locations were obtained by finite element analysis and used as boundary conditions for the mesoscale model. It is suggested that the microscopic sliding process of rough surfaces represented by the finite element analysis can be examined using the proposed method.

In this paper, an application of the surface plasmon resonance (SPR) method to real-time and in-situ measurements of changes in adsorption film thickness, e.g., fatty acid adsorbed films, is presented. As discussed in the previous study, the high sensitivity and overall simplicity of its optical system make the SPR method advantageous for monitoring lubricant film thickness. In order to demonstrate the high sensitivity of the SPR method, in-situ and real-time adsorption film growth processes of stearic acid (additives) in hexadecane (base oil) were monitored using the Otto configuration. Based on a comparison between experimental and model calculation results, changes in the adsorption film thickness during a series of different contact tests were measured.

This study discusses the effect on kinetic friction of the number of surface grooves present on the contact surface of a rubber slider. From some experiments, it was found that the number of grooves is important in determining the kinetic friction. For a dry interface, kinetic friction decreases as the number of grooves increases. However, for a wet interface, the effect of the grooves on kinetic friction depends on the surface roughness of the rubber slider. For a rubber slider with a relatively rough surface, kinetic friction increases as the number of grooves increases. In contrast, for a smooth rubber slider and a wet interface, kinetic friction decreases with increasing number of grooves.

This study provides a new insight into the field of static friction. Based on the static friction model developed by Lorenz and Persson, in which it is assumed that a slip distance characterizes the level of frictional shear stress acting on the contact interface, we pointed out that tangential loading history is an important factor for determining the value of static friction. The stop-restart motion increased the level of static friction force, while the stop-inversion motion reduced the static friction.

This study presents a method for extending the life of tools in cutting of Carbon-fiber-reinforced plastics (CFRP). In the previous study, our research group found that the use of two layer tool, which has a wear resistance distribution due to the use of a combination of two different materials with different hardnesses, is effective for decreasing cutting force during machining of CFRP composites. In the two layer tool, a narrow region of the flank face close to the tool edge and the whole of the rake face were made of a material with a relatively high wear resistance, e.g., diamond or polycrystalline diamond (PCD). In contrast, the other region of the flank face was made of a material with a relatively low wear resistance, e.g., tungsten carbide (WC-Co). In this study, based on some experiments, the effect of the thickness of high wear resistance region on the reduction effects of cutting forces was investigated.

This study investigated the effects of Schallamach wave (SW) propagation on macroscopic frictional behaviors. The temporal changes in the friction force that acts on the sliding interface between a rubber block made of cross-linked polydimethylsiloxane (PDMS) and a cylinder made of polymethyl methacrylate (PMMA) were monitored. Simultaneously, in-situ observation of the sliding interface was performed with a total reflection optical system. Through experiments, three types of sliding modes were observed: stick–slip (SS) resulting from SW propagation (SS–SW), SS resulting from large bulk deformation (SS–BD), and steady sliding without SS (non-SS). The effect of the normal load on the SS behavior was also investigated.

Herein, structural modification of a chemical vapor deposit (CVD) diamond film by a low fluence femtosecond laser irradiation has been studied with Raman spectroscopy, X-ray adsorption fine structure (XAFS) spectroscopy, and X-ray diffraction (XRD). Polycrystalline CVD diamond films of approximately 20 μm thickness were irradiated with femtosecond laser of varied defocus distances corresponding to the laser fluence range of 0.1–127.3 J/cm2. At fluences below 1.27 J/cm2, although there was no observable change in the appearance of the film surface, however, the FWHM of the diamond peak in the Raman spectra was observed to reduce considerably from 17 to 7 cm−1. Furthermore, the higher fraction of diamond phase with the increase in laser fluence strongly suggests that the microstructure of the diamond film has been modified by the femtosecond laser. By employing XAFS measurement, it can be found that after irradiation, the weak π* fine structure in the pre-edge almost vanished in response to the significant increase in σ* adsorption; further, a distinct diamond crystal characteristic peak was observed, which further confirms the femtosecond laser-induced modification, and its occurrence inside the bulk film. XRD results also pointed out that the improved diamond crystallinity with the integral intensities increased by approximately 20% after the femtosecond irradiation. Based on the above-mentioned results, an improvement in the crystallinity of CVD diamond under the low-fluence femtosecond laser irradiation has been confirmed in this study; this is attributed to a photo-induced phase transition from amorphous carbon to diamond.

It has been known that the ultrasonic elliptical vibration cutting (UEVC) is the effective method for ultra-precision machining with diamond tools for ferrous materials. In these cutting methods, the formation of protective films by the adsorption of atmospheric gas to the contact surface suppress the wear of diamond tools. In addition, the ultrasonic vibration cutting has the effect of reducing the rise in the tool temperature during processing, which is also the reason for suppressing tool wear. In this study, to discuss the wear reduction mechanism described above in more details, we investigated the influence of tool wear exerted by the presence or absence of atmospheric gas and by the difference of worked materials. Consequently, it was found that the production of carbide is the controlling factor that determines the wear process of the diamond tool during the ultrasonic vibration cutting. Thus, it was suggested that in atmospheric conditions, the adsorption films from atmospheric gas suppresses the production of carbide, leading to decrease wear of diamond tools.

In the design and development of rubber products, it is important to evaluate the contact load dependency of the friction coefficient. In particular, since the pressure distribution varies depending on the dimensions of sliding bodies and the pattern of the contact surface, a simplified and accurate evaluation method that can take these influences into account is desired. In this study, we proposed a prediction method for the adhesive friction between rubber specimens of arbitrary shapes with arbitrary roughness and a smooth hard surface, by combining the: (1) friction theory considering the influence of roughness; (2) basic friction test; and (3) finite element analysis. Further, we verified the effectiveness of the proposed method by comparing the predicted results with the measurement results of friction between a hemispherical PDMS specimen and a PMMA flat plate and between a PDMS block specimen with a grooved surface and a flat prism. Results show that the prediction accuracy of the contact load dependency of the friction coefficient is reasonably good.

In this study, a new cutting model for the machining of unidirectional CFRP laminates was developed to examine the mechanism for changes in the cutting forces with tool wear. This model is based on Zhang's model and divides the cutting zone into two characteristic deformation regions; chipping and pressing. Furthermore, CFRP milling tests were performed using two kinds of cutting tools: tungsten carbide (WC–Co) and polycrystalline diamond (PCD). Based on the experimental results with the developed cutting model, the net cutting forces to make a cut chip and press CFRP laminates under the flank surface of the tool were quantitatively evaluated. Consequently, it was found that the former does not depend on the progress of the tool wear, but the later increases with tool wear. Additionally, based on the results in this study, a new technique for reducing cutting forces during CFRP machining, which is based on the use of two layer tool that has a wear resistance distribution at around the tool edge was introduced.

Herein, the role of friction-induced torque in sliding friction of rubber materials is investigated. A friction tester was developed to monitor the friction force between a silicon rubber block and a surface made of PMMA 1 . Based on the experimental results, a simplified model was developed to express the nonuniform distribution of normal pressure developed due to the friction-induced torque, and the normal pressure dependence of the real contact area based on Persson׳s contact theory. Based on the modeling, the mechanism of the effect of the friction-induced torque on frictional force reductions was clarified.

This study focused on the normal load dependence of the friction coefficient for the sliding friction of a rubber material with a rough surface. A developed friction tester was used to visualize the real contact regions distributed within the transparent contact interface between poly-dimethyl siloxane (PDMS) and glass surfaces. Based on experimental results, an adhesion friction model was developed to explain the normal load dependence of the friction coefficient. This model provides a simple technique that can roughly but easily estimate the real contact area and shear stress without in situ observation of the contact interface.

This paper discusses tool-wear processes in the milling of carbon fiber-reinforced plastic (CFRP) laminates. Plane down-milling tests with unidirectional and cross-directional CFRP laminates were performed using two types of cutting tools made of tungsten carbide and polycrystalline diamond. Measurements of the changes in the cutting forces and tool-wear widths over the cutting distance revealed that the fiber orientation direction in the CFRP laminates relative to the tool-traveling direction is an important parameter to determine the tool-wear processes. Additionally, based on obtained experimental results, a wear parameter to characterize cutting tool wear is introduced. This parameter can accurately explain the relationship between the worn tool-edge profiles and the processed-surface quality.

This paper presents a novel concept for extending the life of the tools that are used in the milling process of carbon-fiber-reinforced plastic (CFRP) composites. Three types of tools were compared in milling tests; tool I: an uncoated tungsten carbide (WC-Co) tool, tool II: a polycrystalline diamond (PCD) tool, and tool III: a combination tool comprising a PCD layer surface with a thickness of 100 μm and a WC-Co substrate flank surface. The measurement of changes in cutting forces over cutting distance revealed that tool III had a better (tool) life performance than the other tools. Additionally, observation of changes in the edge profiles of the tools revealed that the effective edge sharpness of tool III remains constant during the milling tests. The difference between the wear rates of the PCD rake and WC-Co flank surfaces in tool III maintained a constant effective sharpness during the milling process, and it extended the tool life. Based on our findings, we concluded that using the difference between the wear rates of rake and flank surfaces is an effective technique for tool life extension in the milling process of CFRP laminates.

The erasure of a bit of information is an irreversible operation whose minimal entropy production of kB ln 2 is set by the Landauer limit1. This limit has been verified in a variety of classical systems, including particles in traps2,3 and nanomagnets4. Here, we extend it to the quantum realm by using a crystal of molecular nanomagnets as a quantum spin memory and showing that its erasure is still governed by the Landauer principle. In contrast to classical systems, maximal energy efficiency is achieved while preserving fast operation owing to its high-speed spin dynamics. The performance of our spin register in terms of energy–time cost is orders of magnitude better than existing memory devices to date. The result shows that thermodynamics sets a limit on the energy cost of certain quantum operations and illustrates a way to enhance classical computations by using a quantum system., The research reported here was supported by an advanced ERC grant (Mols@Mols). We also acknowledge financial support by the Dutch Organization for Fundamental research (NWO/FOM). E.B. acknowledges funds from the EU FP7 programme through the project 618082 ACMOL. F.L. acknowledges the Spanish MINECO (grant MAT2015-68204-R), the Gobierno de Aragón (grant E98-MOLCHIP) and the European Union (COST 15128 Molecular Spintronics project). R.G. especially thanks L. Gammaitoni for inspiring discussions.

The interaction stresses (pressure and shear stress) for the (001) surface between a half-space consisting of a homogeneous material and a half-space with a spatially periodic material distribution in two-dimensions (i.e., x- and y-directions) were derived using the Lennard-Jones potential. The periodically distributed material property function was expanded as a complex Fourier series. Because the pressure is the same as that already presented by the authors even though the calculation process is different, only the shear stress in the x-direction is presented here. The shear stress in the y-direction is easily obtained by exchanging variables. The interaction shear stresses for a distribution of two materials as a typical example of a periodic material distribution were calculated. The basic characteristics of the shear stress for parallel planes and inclined planes were quantitatively clarified. Specifically, the distributions of the shear stress, the effects of the surface distance, the duty ratio, the refractive index ratio, and vector diagrams of the shear stresses were presented.