Adhesion Friction Coefficient Research Articles

Characterization of friction behavior under cryogenic conditions: Ti–6Al–4V

Friction phenomena at the chip/tool/workpiece interfaces during machining of material impacts significantly the cutting process. In this article, the effect of friction conditions (dry, emulsion, cryogenic) on the tribological performance of uncoated tungsten carbide tools is investigated when machining titanium alloy Ti–6Al–4V. Friction tests were conducted to analyze the impact of sliding speed and cooling on the evolution of the friction coefficient. To determine the real friction coefficient (adhesive friction coefficient), a numerical simulation using the Lagrangian method was employed. After a comparative study of various simulation methods (“Lagrangian”, “CEL”, and “ALE”), the Lagrangian method was identified as the most relevant. The obtained results reveal that an increase of sliding velocity significantly influences the friction coefficient. Additionally, the application of cryogenic fluid (LN2) reduces the friction coefficient compared to both dry and emulsion-based friction. Adhesion phenomena play a crucial role in the nature of the contact, especially at high sliding velocities.

Effect of C2H2 flow rate on microstructure, properties, and application in micro-drilling of a-C:H films deposited by PECVD

The drilling of printed circuit board (PCB) using micro-drills is an important processing method in modern industry. A protective film with good lubricating and anti-wear properties is generally applied to improve the processing problems of micro-drills during operation. In this study, the effects of C2H2 flow rate on the microstructure, mechanical, and tribological properties of a-C:H films deposited by plasma enhanced chemical vapor deposition (PECVD) technique were investigated. The results showed that when the C2H2 flow rate was low, varying the flow rate had little effect on the microstructure of the prepared a-C:H films. However, when the C2H2 flow rate was greater than 210 sccm, the increase in flow rate caused large particles of carbon clusters to aggregate on the surface of a-C:H films, which resulting in an increase Ra value. Not only did it reduce the adhesion between the film and the substrate, but it also deteriorated the mechanical and tribological properties of the a-C:H film produced. In addition, a-C:H films were also deposited on the micro-drill, and were used for drilling tests on the PCBs to evaluate its servce capability. The optimal parameters of a-C:H film deposited on the micro-drill surface were obtained by observing the morphology of the micro-drill surface after drilling and the hole accuracy statistics. The results showed that a-C:H film deposited on the surface of the micro-drill showed the best machining performance when the C2H2 flow rate was 180 sccm. The surface wear of micro-drill was minimal, the entanglement of tangled chips was minimal. The value of the process capability index (CPK) after 500, 1000, and 2000 drilling of PCB boards was 5.95, 4.33, and 3.15 respectively, which showed the highest drilling accuracy. This is mainly attributed to the better overall properties of the a-C:H films prepared at C2H2 flow rate of 180 sccm, such as lower surface roughness, lowest residual stress, higher hardness, better adhesion, and lower friction coefficient.

Hard and Highly Adhesive AlMgB14 Coatings RF Sputtered on Tungsten Carbide and High-Speed Steel

We report a new industrial application of aluminum magnesium boride AlMgB14 (BAM) coatings to enhance the hardness of tungsten carbide ceramic (WC-Co) and high-speed steel tools. BAM films were deposited by RF magnetron sputtering of a single dense stoichiometric ceramic target onto commercial WC-Co turning inserts and R6M5 steel drill bits. High target sputtering power and sufficiently short target-to-substrate distance were found to be critical processing conditions. Very smooth (6.6 nm RMS surface roughness onto Si wafers) and hard AlMgB14 coatings enhance the hardness of WC-Co inserts and high-speed R6M5 steel by a factor of two and three, respectively. Complete coating spallation failure occurred at a scratch adhesion strength of 18 N. High work of adhesion and low friction coefficient, estimated for BAM onto drill bits, was as high as 64 J/m2 and as low as 0.07, respectively, more than twice the surpass characteristics of N-doped diamond-like carbon (DLC) films deposited onto nitride high-speed W6Mo5Cr4V2 steel.

Numerical analysis of axial compressed multifaceted concrete-filled tube elements

The object of study is multifaceted steel concrete- filled poles. The subject of research is the bearing capacity and parameters of the stress-strain state of multifaceted steel concrete- filled poles. The purpose of the research is to numerically study the features of the operation of multifaceted concrete-filled structures under axial compression. Are discussed the features of creating a computational finite element model of such structures in ANSYS APDL. Analytical methods are described for determining the parameters of the nonlinearity of the materials used, as well as the physical and mechanical characteristics of concrete operating under compression conditions. On specific examples the change in the bearing capacity for the object of study under various conditions of materials adhesion (friction coefficient μ varied within 0.1...0.6 with step 0.1). Is analyzed the "unified" analytical method for determining the bearing capacity of steel multifaceted concrete-filled structures, indicating the degree of variability of ultimate compressive load depending on the variation in the number of faces and thickness of the metal wall of the multifaceted model. The considered features of creating a computational model in the ANSYS APDL finite element analysis system, using various laws of deformation of steel and concrete, made it possible to determine the qualitative and quantitative levels of variability of their bearing capacity, which in combination will allow designers of such structures to reach a qualitatively new level when creating structures based on pipe concrete elements.

The relationship between adhesion morphology and cutting force in orthogonal cutting of 6061-T6 aluminum alloy

Due to the sticky and soft characteristics of aluminum alloy, it is easy to form adhesion on the tool rake face during cutting process. In this work, the orthogonal cutting tests for 6061-T6 aluminum were carried out at cutting speeds of 20–300 m/min and feed rates of 0.05–0.3 mm, and the relationship between adhesion and cutting force has been explored. A slip-line model was used to separate the edge force of cutting edge to obtain the pure friction force of tool rake face, thereby obtaining the average friction coefficient. Adhesion morphologies were observed under the scanning electron microscope (SEM) and compared with the average friction coefficients. It was found that different adhesion morphologies correspond to different friction coefficient ranges. Simultaneously, the relationship between the temperature and normal stress on the tool rake face and the adhesion morphology and friction coefficient was investigated. The results showed that the temperature is the major factor of adhesion evolution and friction coefficient change. Combining the tool rake face temperature and the adhesion morphology, it was noted that the reduction of the friction coefficient is not only owing to the self-lubrication caused by thermal softening, but also due to the decrease of the total shear force caused by the incomplete contact. Finally, the relationship between the friction coefficient of tool rake face and the cutting force and specific cutting energy was discussed, with the conclusion that the friction coefficient has an impact on the cutting force and specific cutting energy by changing the shear angle.

Friction behaviors of rice husk silica-reinforced elastomer composites in contact with rough self-affine surfaces

This study presents rice husk silica-reinforced elastomer composites fabricated by wet compounding, exhibiting 10% higher dynamic friction coefficients than the reference composites made by conventional dry compounding. Depending on the fabrication method, the filler micro-dispersion was characterized to correlate the measured friction coefficients with the viscoelastic properties with respect to sliding velocity and substrate lubrication. The effect of viscoelastic properties of the elastomer composites on the adhesion and hysteresis friction coefficients was investigated based on the elastomer friction theory. It was found that the constructed friction master curves showed a reasonable correlation with the theory. This study demonstrates that the rice husk silica can be used as a reinforcing filler for sustainable tires. More importantly, the well-dispersed filler microstructures can ensure the higher friction coefficients of the elastomer composites on rough surfaces, improving the tire performances (e.g., wet traction, cornering, and acceleration) of the ever-growing electric vehicles and future mobility.

Controllable high adhesion and low friction coefficient in TiAlCN coatings by tuning the C/N ratio

The cutting temperature will be significantly increased while cutting high reactive titanium alloy due to the large friction coefficient of the traditional TiAlN coated tools. The tool could also easily appear adhesive wear and thereby reduce the service life. In this work, TiAlCN coatings with high adhesion and low friction coefficient were deposited by changing the C2H2 and N2 flow rates and using medium-frequency magnetron sputtering. Compared with the TiAlN coating, the hardness of the TiAlCN coating increases up to the value of 20.36 GPa, the toughness is improved by about 230%, the adhesion reaches the value of 156 N. However, the friction coefficient is only 0.231. This performance improvement is attributed to the special structure of (Ti,Al)(C,N) nano-crystalline wrapped by a C-related amorphous phase that is formed in the coating. The structure can be formed by adjusting the C/N ratio to make the C atom content exceed the solid solubility but the C/N ratio does not reach saturation. This kind of TiAlCN coating reduces the wear and inhibits the adhesive wear during the high-speed cutting process of titanium alloy. The cutting distance is also increased by 50% compared with the TiAlN coating.

The co‐effect of microstructures and mucus on the adhesion of abalone from a mechanical perspective

Reliable and reversible adhesion underwater is challenging due to the water molecules and weak layers of contaminants at the contact interface, which requires to deepen the understanding of wet adhesion of biological surfaces. Herein, the co-effect of microstructures and mucus of abalone foot on wet adhesion is investigated from both experimental and theoretical perspectives. The morphologies, adhesion force and coefficient of friction indicate that the mucus in adhesion zone is crucial for successful attachment of abalone based on capillary forces and viscous forces, and the mucus in non-adhesion zone with lower adhesion force and friction coefficient may behave as a lubricant for the locomotion. The theoretical calculation manifests that the microstructures may help abalone to form multiple liquid bridges with the secreted mucus, and significantly increase the wet adhesion force of abalone. These findings will bring profound views into the underlying mechanisms of biological surface adhesion.

Prediction of Adhesion Friction Coefficient Using Two Different Models for Tire Tread Rubber Compounds

ABSTRACT Two proposed methods to determine the adhesion friction coefficient were validated by experimental results of two types of rubber compounds at different sliding velocities under dry conditions. The experimental results were measured from a linear friction tester, while the viscoelastic friction coefficient was estimated using the Persson's contact theory. Adhesive friction (model 1) was derived from the deconvolution of dry friction coefficient in two Gaussian-like curves. Interesting results were obtained using the deconvoluted method in the range of intermediate sliding velocities where preponderant contribution to the adhesion friction is replaced by the viscoelastic friction. Fitting parameter results were in good general agreement with values derived from the literature, confirming the influence of the mechanical properties of the compound and substrate texture on the proposed adhesion frictional method. The second adhesive friction model (model 2) was based on the confinement rheology of rubber chains on the contact with the asperities of the road surface. We demonstrated that acceptable adhesion friction results were achieved from a dynamic viscosity test at low frequencies, confirming the applicability of the proposed rheological model. Moreover, the relationship between the rubber composition and the modified contact layer along with the likely interphase reaction are also discussed.

Novel Environmentally Friendly Lubricants for Drilling Fluids Applied in Shale Formation

One of the biggest difficulties with water-based drilling fluids for shale horizontal wells is its relatively high friction, especially for long horizontal wells. Improving the lubricating ability of drilling fluids is very important for expanding the extension range of horizontal wells in unconventional oil and gas wells. In this work, three kinds of lubricants, graphene oxide (GO), choline chloride/glycerol deep eutectic solvent (Gly-DES), and GO/Gly-DES, were synthesized to investigate their ability to improve the lubricity of water-based drilling fluids. These synthesized lubricants were all environmentally friendly. The tribological test and the filter cake adhesion coefficient test were used to compare the lubricity of these fluids. On the other hand, the traditional commercial lubricant solid graphite (HY-202) was taken as the reference sample. The results indicated that GO and Gly-DES can exert a more obvious lubricating effect at much lower concentrations compared to the reference sample. GO (0.25 wt %) can reduce the adhesion coefficient of filter cake by 93.33% and the friction coefficient of drilling fluid by 48.47%. The complex of GO and Gly-DES can further increase the reduction rate of adhesion coefficient and friction coefficient. Whether it was in reducing the adhesion coefficient of the filter cake or the friction coefficient of the drilling fluids, the combined lubrication effect of GO and Gly-DES was significantly better than using GO or Gly-DES alone. GO and Gly-DES decreased the coefficient of friction due to their good ability in producing a strong protective film on the contacting surfaces of the metal and filter cake. GO and Gly-DES can slightly reduce the filtration volume of drilling fluids and are suitable for shale water-based drilling fluids.

Nano-scratch and nano-indentation study of diamond-like carbon/NiP-SiC nanocomposite bilayer

To overcome the poor adhesion of diamond-like carbon (DLC) films to the steel substrate, an interlayer can be used. In this study, the effect of the addition of NiP-SiC nanocomposite coating as an interlayer in comparison to the NiP coating has been investigated on tribological properties of the DLC layer. Using nano-scratch and nano-indentation tests, the mechanical and nanotribological behaviour of the DLC layers, such as scratch resistance, coefficient of friction, interfacial adhesion between DLC layer and substrate, and hardness were characterised. DLC/NiP-SiC samples showed higher adhesion, hardness, elastic modulus, and lower friction coefficient. These results reveal the improved tribological properties of DLC film by applying the NiP-SiC nanocomposite interlayer in comparison to using the pure NiP interlayer.

Key Properties of a Bioactive Ag-SiO2/TiO2 Coating on NiTi Shape Memory Alloy as Necessary at the Development of a New Class of Biomedical Materials.

Recent years have seen the dynamic development of methods for functionalizing the surface of implants using biomaterials that can mimic the physical and mechanical nature of native tissue, prevent the formation of bacterial biofilm, promote osteoconduction, and have the ability to sustain cell proliferation. One of the concepts for achieving this goal, which is presented in this work, is to functionalize the surface of NiTi shape memory alloy by an atypical glass-like nanocomposite that consists of SiO2-TiO2 with silver nanoparticles. However, determining the potential medical uses of bio(nano)coating prepared in this way requires an analysis of its surface roughness, tribology, or wettability, especially in the context of the commonly used reference coat-forming hydroxyapatite (HAp). According to our results, the surface roughness ranged between (112 ± 3) nm (Ag-SiO2)—(141 ± 5) nm (HAp), the water contact angle was in the range (74.8 ± 1.6)° (Ag-SiO2)—(70.6 ± 1.2)° (HAp), while the surface free energy was in the range of 45.4 mJ/m2 (Ag-SiO2)—46.8 mJ/m2 (HAp). The adhesive force and friction coefficient were determined to be 1.04 (Ag-SiO2)—1.14 (HAp) and 0.247 ± 0.012 (Ag-SiO2) and 0.397 ± 0.034 (HAp), respectively. The chemical data showed that the release of the metal, mainly Ni from the covered NiTi substrate or Ag from Ag-SiO2 coating had a negligible effect. It was revealed that the NiTi alloy that was coated with Ag-SiO2 did not favor the formation of E. coli or S. aureus biofilm compared to the HAp-coated alloy. Moreover, both approaches to surface functionalization indicated good viability of the normal human dermal fibroblast and osteoblast cells and confirmed the high osteoconductive features of the biomaterial. The similarities of both types of coat-forming materials indicate an excellent potential of the silver-silica composite as a new material for the functionalization of the surface of a biomaterial and the development of a new type of functionalized implants.

Effect of Bias Voltage on Characteristics of Multilayer Si-DLC Film Coated on AA6061 Aluminum Alloy

The multilayer Si-DLC films have been deposited on AA6061 aluminum alloy using a mesh hollow cathode plasma-enhanced chemical vapor deposition technique from acetylene and silane precursor gas at temperature 373 K. Low magnification electron microscopes, Raman spectroscopy, and Fourier transform infrared spectroscopy were employed for characterizing the coating film structure. The MFT-4000 scratch tester, G200 nano-indentation tester, and MS-T3001 tribology tester were utilized to evaluate the adhesion strength, mechanical properties, and friction coefficient. Potentiodynamic polarization and potentiostatic techniques were used to study the multilayer Si-DLC films electrochemical behavior in harsh solution 3.5 wt.% NaCl. The findings revealed that the increase in bias voltage to − 300 V led to the adhesion strength, hardness, elastic modulus, and friction coefficient around 18N, 9.89 GPa, 85.57 GPa, and 0.17, respectively. The polarization results showed a decrease in corrosion current density, increased polarization resistance, and decreased passive current almost 1.28×10−10 A/cm−2, 5.26×109 Ω cm2, and 24.3 nA cm−2, respectively. The findings are ascribed to reduce the internal stress and increase the overall content of sp3 bonds in the film. Moreover, the Si-doped DLC film forms a passive layer from SiOx at the film/solution interface to impede the charge transfer.

Evaluation of an Adhesive Friction Coefficient under Extreme Contact Conditions and Its Application to the Machining Process

The premature failure of cutting tools during machining of titanium alloys is primarily attributed to their low thermal conductivity and strain hardening. The coefficient of friction (CoF) at the tool –chip contact depends on the high stress–strain values, interface temperatures, and the velocity of the chip. In this work, a new tribometer is developed to overcome the drawbacks of the existing tribometer and evaluate the adhesive CoF, the heat partition ratio (HPR), and contact pressure. The experiments were conducted on Ti-6Al-4V alloy to estimate the variable CoF and HPR along the rake face. The extent of heat accumulation at the tool–chip interface was quantified using an infrared thermal imaging camera, and the approach successfully mimicked machining conditions, where the tangential force measured up to 900 N and contact pressure was up to 3 GPa. The experiments showed a clear indication of the adhesion of Ti alloy on the tool, strongly suggesting the existence of distinct CoF values for sliding and sticking. The results were further used to develop and validate a finite element model to predict the adhesive CoF, by taking into account the heat partitioning. The results showed considerable dependence of the CoF and HPR on the sliding velocity when implemented in a machining model where 13% maximum error was found in the cutting forces.

Modeling of variable friction and heat partition ratio at the chip-tool interface during orthogonal cutting of Ti-6Al-4V

The extreme contact conditions and temperature at the tool-chip interface in machining make it difficult to access the region and evaluate their tribological properties. To overcome this issue, in the author's earlier work, a new ‘pin-on-workpiece’ tribometer was developed that replicates machining tribological conditions and evaluates the velocity-dependent adhesive coefficient of friction (CoF) and heat partition ratio (HPR). In this work, a 2-D finite element model for orthogonal cutting is developed using ABAQUSTM that takes into account the effect of variable CoF and HPR and assesses their effect on cutting forces and temperature. It is observed that as feed rate increases, the location of maximum temperature along chip-tool interface shifts from 1 mm away from the tool-tip, to closer to the tool-tip. Using the variable CoF, the maximum tool temperature reduces to 490 ∘C from 750 ∘C using the constant friction condition. Also, using the variable CoF, the error in cutting force model is reduced to 13 % from 22 % for the constant friction model.

The effect of surface roughness on normal restitution coefficient, adhesion force and friction coefficient of the particle-wall collision

The normal restitution coefficient is an important parameter in particle deposition which is widely used in industrial fields. The normal restitution coefficient can be affected by many factors, and a typical factor is the surface roughness. Furthermore, a rough surface will influence the adhesion force and friction coefficient. The adhesion force and friction coefficient have effects on the normal restitution coefficient. However, the relationship between the normal restitution coefficient and the surface roughness has not been obtained. Therefore, an experimental study of microspheres impact on a rough surface is developed. The normal restitution coefficient decreases with the increasing surface roughness. The adhesion force is calculated by the Rabinovich model, and the results indicated that the adhesion force increases with the increasing surface roughness within the surface roughness range in this paper. Moreover, the adhesion energy and friction coefficient dissipation increase with the increasing surface roughness.

Analysis of critical negative rake angle and friction characteristics in orthogonal cutting of AL1060 and T2.

The stagnant region often appears in front of the tool cutting edge, which is caused by mechanical inlay and excessive pressing in plastic metal cutting with large negative rake angle tools at a low speed. It results in the change of the effective negative rake angle which can affect the flow characteristics of material, the quality of machined surface and the abrasion loss of cutting tools. However, the critical negative rake angle model based on the existence of the stagnant region has not been reported yet. Therefore, in order to investigate the critical negative rake angle value considering the stagnant region, a critical negative rake angle model based on the principle of minimum required energy is established, and the correctness of the theoretical model is verified by orthogonal cutting experiments. At the same time, the influence of the critical value of the large negative rake angle tool on the machined surface quality is studied through different cutting experiments. These experimental results show that the deviations of both experimental and theoretical critical negative rake angle are less than 5% during the orthogonally cutting of the aluminium (AL1060) and copper (T2) materials by the negative rake angle tool. Meanwhile, the critical negative rake angle is related to the adhesive friction coefficient of tool-workpiece contact surface. The analysis of friction characteristics shows that the deviation values of both theoretical and experimental critical negative rake angle are proportional to the coefficient of adhesive friction and the thickness of the stagnant region. Critical negative rake angle has a significant effect on roughness and residual stress of the machined surface.

Reducing the adhesion effect of aluminum alloy by cutting tools with microgroove texture

Aluminum alloy is widely used in industry. However, due to the low melting point and high toughness of aluminum alloy, the tool adhesive effect often occurs when cutting aluminum alloy, which may lead to tool failure. In this paper, the surface texture technology was used to solve this problem. Microgrooves with five different sizes were fabricated on the rake face of the cutting insert by femtosecond laser. Then, dry cutting experiments and simulation were conducted with different texture inserts. The results indicate that adhesion of workpiece on the rake face can be improved compared with plane cemented carbide cutting tool in a certain range size (7–15 μm). The decrease of tool–chip contact area and large shear angle have a positive effect on reducing the adhesion area and friction coefficient on the cutting experiment.

Mechanical and Tribological Properties of CrN Coated Inconel X750

Three CrN coatings were deposited on the Inconel X750 through the metal vapor vacuum arc ion implantation and the magnetic filtered cathodic vacuum arc deposition system (MEVVA-FCVA) with the N2 flow rates of 10, 50, and 100 sccm, respectively. The surface morphologies and cross-section morphologies of the CrN coatings were obtained through scanning electron microscopy (SEM) and an optical profilometer. The microstructures of the coatings were characterized through X-ray diffraction (XRD). The hardness and the elastic modulus of the coatings were tested by a nano-hardness tester. The adhesion strength and friction coefficients were investigated through scratch tests and ball-on-disk tests and the wear tracks were tested by the optical profilometer. The experimental results indicate that the CrN coating deposited on the Inconel X750 substrate displays a uniform thickness and a smooth surface. The mechanical properties behaves well as the N2 flow rate varies. The CrN coating significantly reduces the friction coefficient fluctuation and improves the antiadhesion and anti-wear properties of the Inconel X750.

Microstructure, composition and properties of Cr–GLC graded coating deposited by unbalanced magnetron sputtering

Cr doped graphite-like carbon (Cr–GLC) graded coating with Cr bottom layer, Cr/C composition gradient layer and Cr–GLC top layer was deposited by unbalanced magnetron co-sputtering of pure chromium and graphite targets. The microstructure, composition and properties including adhesion strength, wear resistance of the as-fabricated Cr–GLC graded coating were investigated by TEM, XPS, scratch test and sliding friction test. Three kinds of phases are detected in the graded layer: pure Cr, a Cr/C nanocrystalline/amorphous phase and amorphous carbon. The HRTEM observation for Cr–GLC top layer with 3 at% Cr indicates that Cr-enriched clusters are embedded in an amorphous carbon matrix. Results of the investigation demonstrate that strong adhesion and stable friction coefficient of the Cr–GLC graded coating are attributed to the consecutive interface microstructure in the coating caused by the interlayer design.