Plastic Contact Research Articles

Development and validation of multi-analyte methods for the determination of migrating substances from plastic food contact materials by GC-EI-QqQ-MS and GC-APCI-QTOF-MS

The packaging has proven to be a source of some serious food contaminants, with several chemicals migrating from the food contact material into the food. Therefore, efficient means of control of the migration extend and identification of the migrating substances must be established. The necessity of migration tests has been underlined by the European Union (EU) Regulation No. 10/2011, requiring the evaluation of the presence of intentionally and non-intentionally added substances. To facilitate this purpose, highly sensitive, multi-analyte methods are required. Targeting a wide range of volatile migrating compounds, we developed and validated a GC-EI-QqQ-MS and a GC-APCI-QTOF-MS method for the simultaneous determination of 131 and 126 food packaging substances, respectively. Even though the GC-EI-QqQ-MS method presented increased sensitivity for several of the investigated compounds, covering the existing EU requirements and specific migration limits (SMLs) for all targeted analytes; the complementary high-resolution method inherently enables the possibility of further utilization of the obtained raw data among others for retrospective analysis. The applicability of both methods was tested using 95% v/v aqueous ethanol food simulant, representative for the worst foreseeable conditions of intended use for many food contact material applications. Real food packaging samples belonging to different types of plastic materials were tested toward chemical migration, utilizing different migration protocols, depending on the sample characteristics. The favorable analytical features of both methods enable their use for the direct analysis of the investigated food simulant, overcoming the need for sample preparation. Thus, labor intensive and/or time-consuming pre-concentration procedures, which would furthermore restrict the applicability of the methods to certain groups of analytes and add to the uncertainty of the overall results, could be eliminated.

Efficient Sub-Modeling for Adhesive Wear in Elastic–Plastic Spherical Contacts

This paper presents a novel approach for simulating adhesive wear in elastic–plastic spherical contacts using an improved finite element sub-model. Initially, a global model with a coarse mesh identifies the potential wear region under combined normal loading and tangential displacement. Subsequently, a refined mesh sub-model simulates the crack initiation and propagation until the formation of a wear particle. This refined sub-model efficiently handles a wide range of spherical radii and normal loads. An expression is derived relating the dimensionless wear volume and wear rate to the dimensionless normal load, revealing the limited effect of the sphere radius on the wear rate. The effect of the mechanical properties on the wear particle morphology is also analyzed.

CFD-DEM analysis of internal packing structure and pressure characteristics in compressible filter cakes using a novel elastic–plastic contact model

Cake-forming filtration is a proven method for separating particles from suspensions. Most filtration models are based on the simplification of incompressible and homogeneous cake structures. However, most filter cakes are in fact unevenly compressed by e.g. the high transmembrane pressures, leading to dense structures with high flow resistance at the filtration membrane. Experimental investigations of these inhomogeneous cakes are challenging due to mostly invasive procedures after filtration has already taken place. In contrast, numerical methods can provide extensive information about fluid flow, particle separation and cake formation during filtration. However, this requires that both elastic and plastic particle deformation and forces are modeled correctly. To achieve this, the present study implemented a novel elastic–plastic DEM model that only requires measurable material parameters and therefore does not need any fitting. Subsequently, previously measured material parameters for elastic–plastic cellulose-lactose pellets (MCC) were used to investigate the packing density, fluid pressure levels and contact forces inside compressible filter cakes using CFD-DEM coupling. A comparison with incompressible and elastically compressible filter cakes showed a significant difference in the filtration behavior. Due to plastic deformation, a strong increase of the packing density when nearing the filtration membrane was found, leading to higher flow resistance for the filtration process. For cyclic filtration events, only the plastically deformed cake showed reduced height recovery in a relaxed state.

Increasing Hardness and Wear Resistance of Austenitic Stainless Steel Surface by Anodic Plasma Electrolytic Treatment

The results of modifying the surface of austenitic stainless steel by anodic plasma electrolytic treatment are presented. Surface treatment was carried out in aqueous electrolytes based on ammonium chloride (10%) with the addition of ammonia (5%) as a source of nitrogen (for nitriding), boric acid (3%) as a source of boron (for boriding) or glycerin (10%) as a carbon source (for carburizing). Morphology, surface roughness, phase composition and microhardness of the diffusion layers in addition to the tribological properties were studied. The influence of physicochemical processes during the anodic treatment of the features of the formation of the modified surface and its operational properties are shown. The study revealed the smoothing of irregularities and the reduction in surface roughness during anodic plasma electrolytic treatment due to electrochemical dissolution. An increase in the hardness of the nitrided layers to 1450 HV with a thickness of up to 20–25 μm was found due to the formation of iron nitrides and iron-chromium carbides with a 3.7-fold decrease in roughness accompanied by an increase in wear resistance by 2 orders. The carburizing of the steel surface leads to a smaller increase in hardness (up to 700 HV) but a greater thickness of the hardened layer (up to 80 μm) due to the formation of chromium carbides and a solid solution of carbon. The roughness and wear resistance of the carburized surface change are approximately the same values as after nitriding. As a result of the boriding of the austenitic stainless steel, there is no hardening of the surface, but, at the same time, there is a decrease in roughness and an increase in wear resistance on the surface. It has been established that frictional bonds in the friction process are destroyed after all types of processing as a result of the plastic displacement of the counter body material. The type of wear can be characterized as fatigue wear with boundary friction and plastic contact. The correlation of the friction coefficient with the Kragelsky–Kombalov criterion, a generalized dimensionless criterion of surface roughness, is shown.

Model of Friction with Plastic Contact Nudging: Amontons-Coulomb Laws, Aging of Static Friction, and Nonmonotonic Stribeck Curves with Finite Quasistatic Limit.

We introduce a model of friction between two contacting (stationary or cosliding) rough surfaces, each comprising a random ensemble of polydisperse hemispherical bumps. In the simplest version of the model, the bumps experience on contact with each other only pairwise elastic repulsion and dissipative drag. These minimal ingredients are sufficient to capture a static state of jammed, interlocking contacting bumps, below a critical frictional force that is proportional to the normal load and independent of the apparent contact area, consistent with the Amontons-Coulomb laws of friction. However, they fail to capture two widespread observations: (i)that the dynamic friction coefficient (ratio of frictional to normal force in steady sliding) is a roughly constant or slightly weakening function of the sliding velocity U, at low U, with a nonzero quasistatic limit as U→0 and (ii)that the static friction coefficient (ratio of frictional to normal force needed to initiate sliding) increases ("ages") as a function of the time that surfaces are pressed together in stationary contact, before sliding commences. To remedy these shortcomings, we incorporate a single additional model ingredient: that contacting bumps plastically nudge one another slightly sideways, above a critical contact-contact load. With this additional insight, the model also captures observations (i) and (ii).

Release characteristics and toxicity assessment of micro/nanoplastics from food-grade nonwoven bags

Micro/nanoplastic (M/NP) contamination in food has become a global concern. Food-grade polypropylene (PP) nonwoven bags, which are widely used to filter food residues, are considered environmentally friendly and nontoxic. However, the emergence of M/NPs has forced us to re-examine the use of nonwoven bags in cooking as plastic contact with hot water leads to M/NP release. To evaluate the release characteristics of M/NPs, three food-grade PP nonwoven bags of different sizes were boiled in 500 mL water for 1 h. Micro-Fourier transform infrared spectroscopy and Raman spectrometer confirmed that the leachates were released from the nonwoven bags. After boiling once, a food-grade nonwoven bag can release 0.12–0.33 million MPs (>1 μm) and 17.6–30.6 billion NPs (<1 μm), equivalent to a mass of 2.25 − 6.47 mg. Number of M/NPs released is independent of nonwoven bag size; however, it decreases with increasing cooking times. M/NPs are primarily produced from easily breakable PP fibers, and they are not released into the water at once. Adult zebrafish (Danio rerio) were cultured in filtered distilled water without released M/NPs and in water containing 14.4 ± 0.8 mg L−1 released M/NPs for 2 and 14 days, respectively. To evaluate the toxicity of the released M/NPs on the gills and liver of zebrafish, several oxidative stress biomarkers (i.e., reactive oxygen species, glutathione, superoxide dismutase, catalase, and malonaldehyde) were measured. The ingestion of the released M/NPs by zebrafish induces oxidative stress in the gills and liver, depending on the exposure time. Food-grade plastics, such as nonwoven bags, should be used with caution in daily cooking because they release large amounts of M/NPs when heated, which can threaten human health.

Effect of Third-Particle Material and Contact Mode on Tribology Contact Characteristics at Interface

A moving pair with two-body contact is the ideal situation assumed in previous analyses. However, all moving pairs are in a three-body contact state at the start of operation or immediately after the start of operation, such as bearings, ball-screws, gears and engines. This work studies the influence of wear particles (SUJ2), environmental particles (SiO2 and Al2O3) and nano-additives (CuO) on the tribological contact characteristics under different particle concentrations, particle sizes, surface roughnesses and contact modes. The three-body microcontact analysis revealed that the differences in the real contact area, particle contact area and separation of the four-particle materials in the three-body s–s and p–s contact modes are rather small. Under the three-body hybrid contact mode, the difference is relatively large and the sequence of the real contact area value obtained due to the elastic modulus for the four-particle material at this interface is Al2O3 &gt; SUJ2 &gt; CuO &gt; SiO2. The order of the other two contact characteristics is reversed. The difference increases as the particle size or particle concentration increases. The order of the critical load required to transform three kinds of contact modes is SiO2 &gt; CuO &gt; SUJ2 &gt; Al2O3. On the nearly initial three-body hybrid contact mode, the plastic contact area ratio at the interface first increases to a critical value and then decreases as the load increases because the original plastic contact spot area and contact spot number increases with the increase in load. At the same time, the elasto-plastic contact area ratio decreases to a low value and then increases. The elastic contact area ratio at the interface decreases as the load increases. Among the four third-particle materials, the experimental results and theoretical predictions show that the environmental particles, Al2O3, cause the maximum friction and wear observed at the interface.

Numerical Analysis of the Mixed-Lubrication Performance of Staved Stern Tube Bearings Lubricated with Water

The present study aims to establish a mixed lubrication model for staved stern tube bearings lubricated with water, in which the average Reynolds equation and a KE elastic–plastic contact model are introduced to calculate the hydrodynamic pressure and contact pressure, respectively. The difference in the mixed lubrication behaviors between circular- and flat-staved bearings is compared; moreover, the effects of the number of staves on the mixed-lubrication performance of these two kinds of staved bearing are investigated. The mechanism of action of the number of staves in staved bearings on the mixed-lubrication performance is revealed. The numerical results show that the number of staves has a significant effect on the mixed-lubrication performance in circular- and flat-staved bearings. Furthermore, there is an optimal value for the number of staves, shown to be 30 in the current simulation, for improving the mixed-lubrication performance of flat-staved stern tube bearings lubricated with water.

Elastoplastic impact of a long rod on a flexible large plate

Unlike impacting a rigid substrate, a rod impacting a flexible plate generates additional dissipation in the bending wave propagating through the plate. In this paper, we present an theoretical model to study the vertical impact of a slender elastoplastic rod impacting a large flexible plate. The longitudinal vibration of the rod is described by the one-dimensional wave equation, and the vibration of the impacted plate is described by the Zener governing equation. An equivalent spring model is used to describe the plastic contact between the elastoplastic hemispherical end and the plate, thus relating the dynamics of the rod and the plate. Laplace transform is used to solve the coupled equations, and the theoretical solution in Laplace space is obtained. The displacement and velocity histories along the rod and the motion of the plate predicted by the theoretical model agree well with the corresponding finite element simulations. In addition, the proposed theoretical model is also applicable when the substrate turns rigid.

Leakage Model of Tubing and Casing Premium Connection Based on Sinusoidal Contact Simulation between Rough Surfaces

This paper proposed a semi-theoretical model to quantitatively predict leakage rate of tubing and casing premium connections. The geometric parameters of the sealing surface profile approximated by a sinusoidal micro-convex surface were first obtained based on the random normal distribution sampling method. With the actual area prediction formula for elastic–plastic contact of an axisymmetric sinusoidal micro-convex body based on the equivalent simulation principle, the circumferential leakage width and radial average leakage height of the micro-leakage channel between sealing surfaces were then acquired with the surface roughness and geometric mean contact pressure. At last, the actual micro-leakage rate of the premium connection was derived by considering the non-uniform contact pressure distribution between sealing surfaces. An example was investigated to validate the model and reveal the sealing and leakage characteristics, and anti-leakage measures were proposed. The results show that average contact pressure, circumferential leakage width, and radial average leakage height between sealing surfaces were non-uniformly distributed. The leakage rate of a premium connection decreases exponentially with an increase in radial interference between sealing surfaces. In order to reduce leakage rate, it is beneficial to increase radial interference and lower sealing surface roughness.

Flexible and Robust Triboelectric Nanogenerators with Chemically Prepared Metal Electrodes and a Plastic Contact Interface Based on Low-Cost Pressure-Sensitive Adhesive.

Triboelectric nanogenerators (TENGs) are devices that can harvest energy from mechanical motions; such devices can be used to power wearable sensors and various low-power electronics. To increase the lifetime of the device, scientists mainly use the method of making TENG in a hard skeleton to simplify the complex possible relative movements between two triboelectric parts. However, the hard skeletons cannot be embedded in soft and lightweight clothing. To make matters worse, the materials used in the garments must be able to withstand high mechanical forces when worn, such as the pressure of more than 100 KPa exerted by body pressure or everyday knocks. Notably, the TENGs are usually made of fragile materials, such as vacuum-evaporated metal electrodes and nano-sized coatings, on the contact interface; these electrodes and coatings often chip or wear off under the action of external loads. In this work, we succeeded in creating a thin, light-weight, but extremely robust garment-integrated triboelectric nanogenerator (G-TENG) that can be embedded in clothing and pass the water wash test. First, we chemically deposited a durable electrode with flexible properties for G-TENG using a novel technique called polymer-assisted metal deposition (PAMD). The as-formed metal electrodes are firmly bonded to the plastic substrate by a sub-10 nm adhesive polymer brush and can withstand a pressure of 22.5 MPa and a tear force of 0.7 MPa. We then removed the traditionally used fragile nanoparticle materials and the non-durable poly-dimethylsiloxane (PDMS) layer at the triboelectric interface, and then used a cost-effective, durable and slightly flowable pressure-sensitive adhesive to form a plastic contact interface. Such a soft plastic interface can ensure full contact of the triboelectric materials, which is excellent in complex environments and ultimately improves the power generation efficiency of the devices. The as-formed low-cost energy harvesting device could become an industry standard for future smart clothing.

Comparison of migration and cumulative risk assessment of antioxidants, antioxidant degradation products, and other non-intentionally added substances from plastic food contact materials

Antioxidants are used in the production of synthetic resins to prevent oxidative degradation. However, non-intentionally added substances (NIAS) and the degradation products of antioxidants may contaminate food contact materials (FCM) and migrate into food. Herein, NIAS and antioxidant degradation products in synthetic resins and their migration into food simulants under various conditions were evaluated. Risk assessment was performed based on the toxicity reference values or with threshold of toxicological concern (TTC) approach. The antioxidant degradation products migrated mainly to fatty-food simulants, with the highest migration in isooctane, followed by n-heptane (similar to or lower than isooctane) and 95 % ethanol. Especially, the migration of 2,4-di-tert-butylphenol was high when the FCM was used for the first time under daily use conditions such as ultraviolet sterilization or heating in a pot, oven, or microwave. In addition, 36 target substances were monitored in 142 products of 18 synthetic resins. Of these, 2,4-di-tert-butylphenol was most sensitively detected. Risk assessment demonstrated that all the investigated substances were below the toxicity reference values. However, the risk associated with polyethylene was relatively high compared to other synthetic resins. The cumulative risks of oxidizing Irgafos 168, (z)−9-octadecenamide, tri-o-tolyl phosphite, tri-p-tolyl phosphite, and 7,9-di-tert-butyl-1-oxaspiro(4,5)deca-6,9-diene-2,8-dione using the TTC approach were calculated to range from 34.81 % to 73.74 %, suggesting that the TTC is a more conservative risk assessment.

Effects of Make-Up Torque on the Sealability of Sphere-Type Premium Connection for Tubing and Casing Strings

The present investigations on sealability evaluation for tubing and casing premium connections depend on the FEM with testing. This paper proposed a theoretical model to evaluate the sealability of a sphere-type premium connection based on make-up torque, which combines Hertz contact pressure and the von Mises yield criterion for calculating elastic–plastic contact pressure distribution on sealing interface and adopts the gas sealing criterion obtained from Murtagian’s experimental results for deducing gas sealing capacity. With the proposed model, the effects of additional make-up torque from the sealing interface on the sealing contact pressure distribution and key sealability parameters, including contact width, yield width, average contact pressure and gas sealing capacity, were analyzed and compared. The results show that additional make-up torque from the sealing interface closely influenced sealability parameters’ variation and gas sealing capacity. The gas sealing index based on the sealing contact energy theory should be recommended for sealability evaluation other than average contact pressure on the sealing interface. For improving gas sealability, make-up torque should be controlled accurately for ensuring enough average contact pressure and contact width but a proper yield width, and a lager sphere radius should be selected for reducing the risk of yield sticking.

Biomechanical characteristics of self-expanding sinus stents during crimping and deployment_A comparison between different biomaterials

Self-expanding sinus stents are often used in functional endoscopic sinus surgery to treat inflamed sinuses. The PROPEL self-expanding sinus stent offers mechanical support to the sinus cavity to prevent restenosis. The stent is made of a bioabsorbable material (PLGA) that disappears after wound healing. However, complications such as foreign body sensation and severe stent migration/expulsion have been reported after implantation. Little is known about the contact characteristics of self-expanding sinus stents from when the stent is crimped into the insertion device through to deployment into the sinus cavity. This current study developed a test platform to analyze the biomechanical behavior of the stent during this process. Three common bioabsorbable materials, PLGA, PCL and Mg alloy, were evaluated to understand how the choice of material affects the biomechanical characteristics of self-expanding sinus stents. The results showed that the material can have a considerable influence on the contact characteristics during crimping and deployment. When crimped, the PLGA and Mg alloy stents showed much higher plastic strain and contact stress than the PCL stent. When deployed, the PCL stent had the largest contact area (4.3 mm2) and the lowest contact pressure (0.1 MPa) on the inner surface of the sinus canal. The results indicate that PCL could be a suitable choice for self-expanding sinus stents. This current study provides a method for observing the biomechanical characteristics of sinus stents during stent crimping and deployment.

Friction of Coated and Uncoated Rough Surfaces in Additive-Free and Fully Formulated Engine Oils Under Boundary and Mixed Lubrication Conditions

Abstract Downsizing in spark-ignited engines becomes one of the most effective concepts to achieve fuel economy and emissions requirements and drives operating conditions of major moving engine components into more mixed and boundary lubrication regimes. Piston ring design faces considerable challenge to reduce friction losses, oil consumption, blow-by, and wear. Surface coatings have received great attention in applications of automotive engine components due to their unique friction properties. In this study, an elastic–plastic contact model of rough surfaces with hard coatings is used to provide proper design of the ring coating thickness concerning the plasticity-yielding resistance of stiff coating. A diamond-like carbon (DLC) coating with surface hardness higher than current production ring coatings has been evaluated in additive-free base oil and fully formulated engine oil under boundary and mixed lubrication conditions. The friction behavior of the coated material relative to uncoated materials is compared in boundary and mixed lubrication regimes. A traction-merging rolling speed in the mixed lubrication regime is observed, at which friction coefficient is independent of applied loads. By using a mixed lubrication model previously published, calculations indicate that the lower the traction-merging rolling speed, the earlier the contact approaches elastohydrodynamic lubrication (EHL), therefore reducing the risk of asperity-interacting fatigue in boundary and mixed lubrication regimes. Effects of tribofilm on friction behavior for DLC coating and uncoated steel in fully formulated oil are investigated by using measured Stribeck curves in conjunction with the model. The results from this study analytically support one of the possible mechanisms of tribofilm-dependent friction enhancement in mixed lubrication conditions proposed in the earlier publication.

Calculation method for heat and mass transfer apparatuses with porous plastic contact devices

The development of effective contact devices for heat and mass transfer apparatuses, which allow increasing the intensity of heat and mass transfer processes, reducing the size and cost of technological equipment, is an important practical task of the modern food industry. In this regard, the high efficiency of foam contact devices is noted, due to the developed specific surface and low hydraulic resistance. In the course of the study, a general classification of these devices has been proposed; schematic diagrams of the constructions of foam packings and trays have been given, a brief comparative analysis of their application area has been carried out. The main stages of calculation of highly efficient heat and mass transfer apparatuses with cellular plastic contact devices, including the determination of the basic geometrical characteristics of cellular materials, packing height (plate thickness), number of packing sections (number of plates), hydraulic resistance of packed and plate apparatus, have been described in detail. An example of an engineering calculation of a distillation heat and mass transfer apparatus with packed and plate-shaped foam contact devices for the separation of a binary mixture "ethyl alcohol - water" has been considered. The results of the calculation are presented in tabular and graphical form and allow us to conclude that it is most expedient to use packed foam contact devices with smaller dimensions and hydraulic resistance.

Increasing Wear Resistance of Low-Carbon Steel by Anodic Plasma Electrolytic Sulfiding

The paper considers the problem of increasing the wear resistance of steel products. For the first time, the technology of anodic plasma electrolytic sulfiding is proposed to increase the wear resistance of low-carbon steel. The composition, structure, and frictional properties of modified surface layers after sulfiding have been studied. The type and mechanism of wear are determined. The influence of the sliding speed of the sample over the counter body on the friction and wear resistance of the samples after processing is analyzed. The possibility of saturation of low-carbon steel with sulfur in an electrolyte with sulfur compounds is shown. The iron sulfide FeS in the surface layer is found. It has been established that the thickness of the sulfide zone and the relative amount of FeS in it have a positive effect on reducing the coefficient of friction and mass wear. The greatest decrease in the friction coefficient by 5.5 times and weight wear by 64 times occurs after sulfiding at 500 °C for 10 min. It was found that the mechanism of wear of sulfided samples is fatigue wear during dry friction and plastic contact.

Finite element analysis of microscopic fracture process in titanium metal matrix composite shafts using a unit cell approach

The aim of this study is to investigate the microscopic fracture process in titanium metal matrix composites (TiMMC) shafts based on finite element (FE) analysis. A unit cell approach is used as a tool to design a representative volume element to explain the complex failure phenomenon on a microscopic level. FE mesh convergence is examined and validated with the equivalent plastic strain and contact pressure. The accuracy of the numerical modelling is verified by comparison with experimental investigations on fractured TiMMC shafts. The results show that FE modelling can successfully analyse the complicated fracture process that occurs on a microscopic scale of TiMMC shafts.

Nanoindentation creep behavior of diverse microstructures in a pre-strained interstitial high-entropy alloy by high-throughput mapping

Time-dependent plastic deformation, also known as creep, can occur in high-melting-point materials at room temperature when subjected to submicron plastic contact (e.g., components in micro-electronic mechanical systems) due to the extremely high stress conditions. Previous investigations of creep behavior at submicron scale mainly focus on uniform microstructures, whereas recently developed high-performance structural materials usually show complex microstructural heterogeneities. Here, we demonstrate a high-throughput nanoindentation approach to unveil the creep behavior of locally diverse microstructures, via a case study on an interstitial high-entropy alloy (iHEA). The prototype iHEA specimen was firstly pre-strained by severe cold-rolling to achieve diverse microstructure features including dense dislocations, nanotwins and nanograins. Nanoindentation mapping with 144 indents is conducted to collect creep data from all types of diverse microstructures, followed by systematical calculations based on power-law analysis. Then intuitive contour maps of nanohardness (H), strain rate (ε˙) and stress exponent (n) are attained. The individual creep mechanism of each microstructure variant is evaluated by correlating local microstructure features with corresponding creep responses from these contour maps. With the increase of n value for different sample regions, the ε˙ value inversely reduces and the corresponding dominant creep mechanism gradually converts from diffusion-mediated mode to dislocation-controlled one. The presence of nanograins and nanotwins significantly hinders dislocation interactions and promotes stress-induced diffusion. This work verifies that nanoindentation creep behavior is highly correlated with local microstructure features, and the mapping approach is feasible for evaluating creep-resistance of locally diverse microstructures under extremely high-stress conditions.

Contact Characteristics at Interface in Three-Body Contact Conditions with Rough Surfaces and Foreign Particles

Nanoparticles as lubricant additives under a certain average diameter and concentration may reduce wear, friction and scuffing damage. However, atmospheric dust particles affect not only human health but also the efficiency of components, and even cause component failures. Therefore, the contact characteristics at interfaces with foreign particles require careful investigation. In this work, a 3-body microcontact mechanics concept is used to analyze the effects of wear debris and foreign particles on real contact area, contact mode, asperity deformation type and separation at interface. The results show that the relationship profile between dimensionless real contact area (At*) and dimensionless normal contact load (Ft*) is wedge-shaped in a 3-body contact interface. Using surface-to-surface 2-body contact area as upper bound and surface-to-particle 3-body contact as lower bound, the 3-body hybrid contact situation is in between upper and lower bounds. As the dimensionless normal contact load increases, At* increases gradually as well. The order of contact mode is p-s contact, hybrid contact and then s-s contact. If the 3-body contact interface is in hybrid contact mode, the decrease in the hardness and average third body diameter will cause the At* to increase significantly at the same Ft*. Conversely, the separation and real contact area ratio of plastic deformation decrease gradually. The turning point of contact area (TPCA) occurs when the contact mode is within hybrid contact mode and the ratio of average third body diameter to the composite equivalent surface RMS roughness is about 50–70% for foreign particles and wear debris. When the Ft* is slightly larger than Ftpca*, the third body and surface share the total interface load approximately equally which will help reduce the real contact pressure and plastic contact area to improve surface performance.