Sliding Wear Mode Research Articles

Comparative study on tribological behaviors of interproximal tooth enamel against zirconia under fretting and sliding conditions

Interproximal contact loss (ICL) between zirconia crown and adjacent natural teeth is a common complication that could lead food impaction and compromise the periodontal/peri-implant tissue health and patient’s satisfaction. Both fretting and sliding wear mode can be found in the frictional pair between zirconia crown and interproximal enamel during mastication. In this study, fretting and sliding wear behavior of interproximal enamel against zirconia in artificial silva was investigated. The wear damage of the interproximal enamel in a sliding movement was higher than in a fretting movement. In fretting mode, the running condition fretting map (RCFM) composed of partial slip regime (PSR), gross slip regime (GSR), and mixed fretting regime (MFR) was constructed depending on different normal loads and displacement amplitudes. Intact surface was observed in the PSR. Plastic deformation at contact center and microcracks at contact margin were detected in the MSR. Severe wear damage occurred in the GSR, predominated by microfracture, brittle deformation. Macroparticles generation, fatigue delamination and abrasive wear prevailed in sliding mode. In contrast, enamel debris could be transferred on zirconia surface while the material loss of the antagonist zirconia was negligible in both fretting and sliding test.

Study on Mechanical and Tribological Characteristics of Epoxy Composites Reinforced with Short Areca-catechu Fibers

ABSTRACT This paper reports on the dry-sliding wear behavior of natural fiber fortified polymer composites. Such composites are fabricated using epoxy as the matrix and short areca-catechu fibers as the reinforcing element through the conventional hand lay-up route. Four different fiber loadings (0, 2, 4, 6 wt.%) are considered to get samples of different compositions. Physical and mechanical characteristics like density, porosity, and tensile strength are measured. Digimat-FE software is also used to determine the density and stress distribution of the composites. It is found that the tensile strength of composite increases about 47% compared to neat epoxy resin when with the addition of 6 wt.% fiber content. Dry sliding wear tests are carried out using a pin-on-disc test rig according to ASTM standards. Different sliding velocities, sliding distances, and normal loads are considered. Tests are designed as per Taguchi’s L16 orthogonal array and a specific wear rate for each test run is obtained. Noticeable control factors influencing the wear rate are pointed out and ranked. It is found that the reinforcement of short areca-catechu fibers helps in improving the wear resistance of epoxy in dry sliding wear mode. An optimum factor condition for the lowest wear rate is determined. Based on the data obtained from experiments, a predictive equation is proposed to find the specific wear rate of such composites under varied test conditions. The outcomes predicted by this proposed correlation are found to be in a great settlement with the experimental ones.

Deposition of Amorphous Hardening Coatings by Electrospark Treatment in a Mixture of Crystalline Granules

This article is devoted to the formation of amorphous coatings on the steel 35 surface by electrospark treatment in a mixture of crystalline granules. It is revealed by the energy dispersive X-ray spectroscopy (EDS) that formed coatings contain W, Mo, Co, and Ni in various ratios. The weight of granules of various compositions decreases by 11–16 wt % for 6-h treatment due to electric erosion. The mass transfer coefficient varies in a range from 33 to 54%. X-ray structural analysis showed the prevalence of an amorphous phase (81–99%) in the structure of deposited layers. Annealing of coatings at a temperature above 1150°C leads to the crystallization of the amorphous phase into boron carbide of the M23(C, B)6 type, as well as into α-Fe. The coatings have an increased hardness of 10–15 GPa, while their wear resistance in the dry sliding wear mode under loads of 10 and 50 N is higher than for steel 35 by a factor of 3.3 and 1.6. The coating friction coefficient is lower than for steel 35 by 13–30% and was 0.27–0.31. The wear resistance of coatings in a dry abrasive wear mode is higher by a factor of 3–5 when compared with uncoated steel 35. The best characteristics are inherent without nickel and worst are inherent without cobalt. Thus, it is established that tungsten and cobalt increase the wear resistance of iron-based amorphous alloys, while nickel and molybdenum tend to worsen their tribotechnical behavior.

Corrosion, Mechanical and Catalytic Properties of Coatings Based on FeNiCrWMoCoCB Metallic Glasses

This work is devoted to the deposition of coatings based on FeNiCrWMoCoCB metallic glasses on a surface made of 35 steel; the deposition is carried out by electrospark machining in a medium of granules of metals and alloys used as electrode materials. X-ray diffraction analysis showed that an amorphous phase is predominant in the composition of coatings. At a temperature of 1100°C, the amorphous phase crystallizes in borocarbide of the M23(C,B)6 type, an intermetallic of iron, nickel, and chromium, and αFe phase. Polarization tests of the coating in the NaCl solution (3.5%) demonstrate a lower corrosion current and a higher polarization resistance compared with the 35 steel. It is found during the study of a heat resistance at 600, 700, and 800°C that the use of the FeNiCrWMoCoCB coating on the 35 steel enhances a resistance of its surface to a high-temperature gas corrosion in 8.7, 6.3, and 3.0 times, respectively (the experiment time was 40 h). The wear resistance of the FeNiCrWMoCoCB coatings in a dry sliding wear mode at loadings of 10 and 25 N was 2.2 and 1.7 times higher than for the 35 steel. The samples with the coatings based on the FeNiCrWMoCoCB metallic glasses show a high catalytic activity for a decomposition of a methylene blue solution as at the presence of hydrogen peroxide, as well as without it.

Effect of Grain Boundary on the Wear Behaviour of NiTi Shape Memory Alloys When Mf < T < Af

Wear behaviour of NiTi SMA is closely corresponds to deformation mechanisms associated with different plastic strain accumulation process. Plastic strain accumulation is achieved by dislocation motion; however, grain boundary acts as a strong barrier. In this work, wear behaviour of single-crystalline and polycrystalline NiTi SMAs was studied to understand the effect of grain boundary on the plastic strain accumulation in the wear process. Wear tests were conducted at Mf < T < Af, where phase boundary exists between martensitic and austenitic phases. Tests were conducted under ball-on-disc sliding wear mode, and alumina (Al2O3) counter-body was used. For single-crystalline NiTi SMA, transition wear occurred even when the applied load was relatively low (i.e., 100 mN). For polycrystalline NiTi SMA, with increasing applied load and wear cycles, the wear has shifted from near-zero wear stage to severe wear stage; no transition behaviour was observed. Significant differences in the wear process were discussed with respect to deformation mechanisms associated with dislocation motion in the single-crystalline and polycrystalline NiTi SMAs.

Friction Behavior at the Interface Between Surgical Sutures and Tissues

In the process of surgical suturing, friction phenomena at the interface between sutures and tissues can seriously affect the suturing efficiency. However, few studies have assessed the detailed effects of types of sutures or tissues and stitching parameters on the friction behavior. In this paper, the different factors affecting the friction behaviors between sutures and tissues were studied. The unidirectional sliding wear mode in a line-on-flat configuration was selected to simulate the real surgical suturing by using a UMT-II Micro-Tribometer. Artificial skin, porcine muscle and porcine liver were used as experimental samples. Three different surface morphology and structure sutures: multifilament suture (silk), monofilament suture (prolene) and multifilament suture with coating (vicryl), were investigated in this study. The normal load was from 0.1 to 0.5 N, and the unidirectional sliding (suturing) speed was from 5 to 25 mm/s to simulate the suturing operation. Results showed that the friction coefficient at the suture–tissue interface decreased with the increase in normal load and increased with the increase in suturing speed due to the nonlinear viscoelasticity and deformation hysteresis of the soft tissues. The sutures with monofilament structure or coating could effectively reduce the friction coefficient of the suture–tissue interface. Compared to the artificial skin, the porcine tissues had the lower friction coefficients because of 30% blood and 17% interstitial fluid filled in liver and muscle, respectively, which acted as lubricants and reduced the adhesion friction coefficient of the suture–tissue interface. The results can provide guidance for the surgical suture manufacture and the surgical manipulation skills.

Effect of Deformation Mode on the Wear Behavior of NiTi Shape Memory Alloys

Owing to good biocompatibility, good fatigue resistance, and excellent superelasticity, various types of bio-medical devices based on NiTi shape memory alloy (SMA) have been developed. Due to the complexity in deformation mode in service, for example NiTi implants, accurate assessment/prediction of the surface wear process is difficult. This study aims at providing a further insight into the effect of deformation mode on the wear behavior of NiTi SMA. In the present study, two types of wear testing modes were used, namely sliding wear mode and reciprocating wear mode, to investigate the effect of deformation mode on the wear behavior of NiTi SMA in both martensitic and austenitic states. It was found that, when in martensitic state and under high applied loads, sliding wear mode resulted in more surface damage as compared to that under reciprocating wear mode. When in austenitic state, although similar trends in the coefficient of friction were observed, the coefficient of friction and surface damage in general is less under reciprocating mode than under sliding mode. These observations were further discussed in terms of different deformation mechanisms involved in the wear tests, in particular, the reversibility of martensite variant reorientation and stress-induced phase transformation, respectively.

Influence of exfoliating facial cleanser on the bio-tribological properties of human skin

In daily life, cosmetics can play important roles in facial skin moisturizing, whitening and sun protecting. Unfortunately, the aged skin stratum corneum (SC) often impedes the penetration for cosmetics. Regular removal of the extra aged horny cells can facilitate the penetration for cosmetics and improve the performance of the skin. However, no study has assessed the detailed effects of exfoliating facial cleanser on the friction properties of human skin and the degree of aged SC removal. In this paper, the effects of three kinds of scrub facial cleanser with different sizes, amounts and hardness scrub particles on the tribological properties of human skin have been investigated in vivo using a UMT-II tribometer under the simulated face washing conditions. The hardness of the scrub particles were measured by using a Nano-Hardness/Scratch Tester. The results showed that the aged SC has all been removed by the three kinds of scrub cleanser under the reciprocating sliding wear mode, which resulted in decrease of skin surface roughness and increase of skin conductance and hydration. Thus, the adhesion force and friction coefficient between the hydrated skin and a probe increased due to the increased contact area and skin hydration. Compared with the other two cleansers, the cleanser with two kinds of size and moderate hardness scrub particles made the skin to deform more elastically and removed more aged SC, which led to greater decrease in skin surface roughness and greater increase in skin conductance, hydration and adhesion. Hence the skin friction coefficient and penetration were higher and the moisturizing persistence lasted longer time after the same moisturizer was used. This indicated that the properties of scrub particles in cleanser played important roles in skin tribological behavior and penetration. The results may be instrumental in developing and testing skin cosmetics.

Influence of wood flour loading on tribological behavior of epoxy composites

AbstractA series of wood flour (WF) filled epoxy composites consisting of five samples were prepared by varying the concentration of WF in step of 10 wt%. These samples were characterized for its wear behavior in abrasive and sliding wear modes to study the influence of WF. It was observed that specific wear rate (k0) of all the composites decreased with increasing load in sliding wear mode. Specific wear rate was of the order of 10−10 m3/Nm in abrasive wear mode and ∼10−14 m3/Nm in sliding wear mode. Composite containing 40 wt% WF exhibited the lowest specific wear rate in abrasive wear mode. While composite containing 20 wt% WF exhibited lowest specific wear rate in sliding wear mode. This was attributed to the fact that in abrasive wear mode, the wear debris consisting of mainly WF particles was maximum for 10 wt% composite and minimum for 40 wt% composite. In sliding wear mode, the exposed WF particles caused maximum roughening of steel counterface in the case of composite containing higher concentration of WF particles. Hence, they exhibited a higher value of specific wear rate. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Friction and wear properties of TiB2P/Al composite

Abstract The dense and homogeneous 30 vol.%TiB2P/Al composite was successfully fabricated by squeeze casting technology, and its friction and wear properties were investigated. Results show that in dry sliding wear mode, friction coefficient of TiB2P/Al composite at the steady stage was only about 0.16–0.17, while that of SiCP/Al composite fabricated by the same method was 0.7. In addition, wear volume of TiB2P/Al composite was less than that of SiCP/Al composite. The TiB2P/Al composites exhibited higher wear resistance. No obvious characteristics of adhesion or abrasion wear were observed on worn surfaces of TiB2P/Al composites. All of these properties might be attributed to the oxidation of TiB2 and the formation of boric acid film on the sliding surfaces.

Predicting Sliding Wear Behaviour of a Tin-Based White Metal Under Varying Pressure and Speed Conditions

To determine the effects of loading on the sliding wear behaviour of a tin-based white bearing metal JIS WJ2, experiments were performed over a range of pressures and speeds. A linear relation between stress and cut-off life was obtained on the log-log plot at constant shaft speed. These relations were expressed as different straight lines on the log-log plot, which depend on the shaft speed. However, there is a unique curve in the relation, frictional stress versus cut-off life, regardless of the shaft speeds. To establish a quantitative method of analysing the steady-state sliding wear mode, the following constitutive relation was proposed d w/d N = A(τ – τth)2 where w is the amount of wear, N the number of shaft rotations, A the material constant, τ the interfacial shear stress, and τth the threshold level for wear damage. The aforementioned equation has been used as a basis for estimating wear life. Good agreement between the predictions and the experimental results was obtained.

Role of fabric reinforcement on the low amplitude oscillating wear of polyetherimide composites

Influence of fabric reinforcement in polymers is well investigated in the unidirectional sliding wear mode leading to adhesive wear of the composites, but not in the case of low amplitude oscillating (fretting or reciprocating) wear mode. In the authors’ laboratory, series of polyetherimide (PEI) composites reinforced with fabrics of carbon and glass were investigated in this respect. In this paper, results on the low amplitude oscillating wear of three composites, viz. C CF, C AF and C HY containing fabrics of carbon (CF), aramid (AF) and combination of both (hybrid, HY) based on PEI matrix are presented. After characterizing for physical and mechanical properties, these composites along with the unfilled PEI (C 0) were evaluated for their low amplitude oscillating wear performance on SRV optimol tester under different loads and temperatures using ball-on-pin configuration. It was concluded that the carbon fabric proved to be significantly beneficial in improving the friction and wear performance of PEI under all loads and temperatures. AF inclusion on the other hand, proved beneficial for improving the friction behaviour moderately. It also improved the wear performance of PEI under high loading conditions but not under high temperature conditions. At 100 °C, the wear performance was poorer than that of unfilled PEI. Interestingly, friction behaviour of hybrid composite was almost similar to that of C AF but not the wear behaviour. The wear performance of C HY under high loading condition was little lower than that of C AF, but significantly better than that of unfilled PEI. The C HY had clear edge over C AF in the high temperature wear performance. At temperatures up to 150 °C, it exhibited improved wear performance unlike C AF. Beyond that, however, the performance deteriorated. SEM studies proved to be helpful in understanding the wear mechanism.

Analysis of sliding wear mode on annealed steel by X-ray diffraction technique

It is known that identifying the wear mode on worn surface is very important to improve the tribological performance of machinery or structural applications. In adhesive wear, unlike abrasive wear, the wear mode can be characterized by the amount of plastic deformation on the worn surface because wear occurs as a result of the shearing action around the adhesive area. Therefore, wear mode on actual worn surface must be related to the strain measured by X-ray diffraction on it. In this study, several sliding wear tests using the annealed plain carbon steel were carried out under several different sliding speeds in a pin-on-disc test. The plastic deformation on the worn surfaces was examined by the X-ray diffraction technique. The result of this study indicated that the state of strain on the worn surface measured by X-ray diffraction had a good relationship with the state of wear. The magnitude of strain on worn surfaces corresponds to the wear rate, and the increasing rates of strain with sliding distance correspond to the wear modes. It was also observed that the half-value width of the X-ray diffraction profile on worn surfaces under steady state condition had a good correlation with the wear rate at the corresponding wear mode, regardless of the measuring direction.

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In daily life, cosmetics can play important roles in facial skin moisturizing, whitening and sun protecting. Unfortunately, the aged skin stratum corneum (SC) often impedes the penetration for cosmetics. Regular removal of the extra aged horny cells can facilitate the penetration for cosmetics and improve the performance of the skin. However, no study has assessed the detailed effects of exfoliating facial cleanser on the friction properties of human skin and the degree of aged SC removal. In this paper, the effects of three kinds of scrub facial cleanser with different sizes, amounts and hardness scrub particles on the tribological properties of human skin have been investigated in vivo using a UMT-II tribometer under the simulated face washing conditions. The hardness of the scrub particles were measured by using a Nano-Hardness/Scratch Tester. The results showed that the aged SC has all been removed by the three kinds of scrub cleanser under the reciprocating sliding wear mode, which resulted in decrease of skin surface roughness and increase of skin conductance and hydration. Thus, the adhesion force and friction coefficient between the hydrated skin and a probe increased due to the increased contact area and skin hydration. Compared with the other two cleansers, the cleanser with two kinds of size and moderate hardness scrub particles made the skin to deform more elastically and removed more aged SC, which led to greater decrease in skin surface roughness and greater increase in skin conductance, hydration and adhesion. Hence the skin friction coefficient and penetration were higher and the moisturizing persistence lasted longer time after the same moisturizer was used. This indicated that the properties of scrub particles in cleanser played important roles in skin tribological behavior and penetration. The results may be instrumental in developing and testing skin cosmetics.

Wear Map of Ceramics. 2nd Report. Construction of Mild-Severe Wear Mode Map.

The overall objective of this study is to introduce a wear map of ceramics which shows the regions of dominant wear modes obtained in a wide range of materials and operating conditions. In the 1st report, it was clarified that the sliding wear mode of ceramics observed under various contact pressures, sliding velocities and temperatures can be classified into two types called "mild wear" and "severe wear" based on the ratio of worn surface roughness, Ry, to mean grain size, Dg, and specific wear amount, Ws. In this paper, the critical condition of the mild and severe wear is analyzed using an intergranular fracture model from both the view points of mechanical and thermal aspects, and a wear map of ceramics, which can define the regimes of mild and severe wear, is introduced; it uses two dimensionless parameters named as the mechanical severity of contact Sc, m and the thermal severity of contact Sc, t, as the vertical and horizontal axes, respectively. The availability of the wear map constructed in this way can be proved by the experimental results observed over a wide range of materials and operating conditions.

The wear of diamonds in impregnated diamond bit drilling

The wear of diamonds in impregnated diamond microbits was investigated in the laboratory by drilling a variety of rock types. The wear was studied by optical and scanning electron microscopy after drilling under a range of bit pressures, rates of advance, and rotational velocities using bits of different diamond size and concentration. The nature of the diamond wear modes did not vary with the drilling conditions but the relative proportions of different types of diamond wear changed with drilling performance. For stable drilling in any given rock type a characteristic threshold pressure existed above which desirable microfracture of the exposed diamonds was promoted over undesirable wear flat generation. The flats are produced by a sliding wear mode with the silicate minerals ploughing plastic grooves in the heated surfaces of the diamonds. Microfracture mode is the result of progressive growth and coalescence of cleavage microcracks promoted by the cyclical stresses experienced by the diamonds at pressures sufficient to cause indentation of the rock.

Implantation of Ti + C for reduced friction and wear of steels

A review of various types of friction and wear tests of ion-implanted steels with 10–30 at% Ti and C shows that the implantation reduces wear and unlubricated friction for every steel examined, even for Hertzian contact stresses in excess of the bulk yield strength. The microscopic information on implanted Fe and steels obtained by TEM, Auger analysis and ion beam analysis is presented, and the near-surface amorphous alloy discovered in similarly implanted Fe is shown to be closely associated with the benefits obtained with the Ti + C treatment of steels. The implanted layer changes the unlubricated sliding wear mode from adhesive to abrasive, and the increased hardness of the amorphous alloy then promotes wear resistance. Recent results suggest that the optimum alloy is obtained by using a high Ti concentration (~ 30 at%) and by implanting C to produce as thick an amorphous layer as possible.