Sliding wear

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Effect of vanadium carbide on dry sliding wear behavior of powder metallurgy AISI M2 high speed steel processed by concentrated solar energy

Effect of vanadium carbide on dry sliding wear behavior of powder metallurgy AISI M2 high speed steel processed by concentrated solar energy

For composite with 10 wt.% of VC drag material and accumulation of debris increased (Fig. 11e). The EDX analysis of these areas indicated a higher oxygen and carbon content than the adjacent matrix. Conse- quently, oxidation and precipitates release took place during sliding. EDX con fi rmed that some black and small spots observed on the SEM micrographs corresponded to trapped alumina particles, which agrees with the fact that there is some volume loss of the pin. During the sliding wear test, the hard phase was detached on the sliding contact, which produced a three-body abrasive wear mechanism. The high hardness of this particles produce abrasive wear on the pin and therefore alumina particles can be incorporated to the debris. Because of the high contact pressure between pin and disk, these particles are encrusted in matrix. Fig. 12 shows SEM micrographs after linearly reciprocating wear for composites with 3 wt.% of VC sintered by solar energy. The wear track width is higher than the observed on rotating wear although the scar depth is clearly lower. Fig. 12a shows the scratches in the wear track of a composite sintered in PSA but much less intensive than the ob- served on rotating wear. The amount of wear debris was also small. Fig. 12b shows primary carbides and secondary particles remaining in the wear track and helping to withstand the wear. This behavior is pos- sible because these particles are well linked to the matrix and cannot be easily detached. Similar observations can be done for composite sintered in HSO but in this case, more evidences of deformation of the matrix and lower amount of debris was found, Fig. 12c. These observa- tions agree with the lowest wear rates registered for reciprocating tests. Similar observations can be done for samples sintered in TF, but in this case, there is more abrasive wear that can explain the highest wear coef fi cients especially for M2 sample, Fig. 13a. Signi fi cant Table 4
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12 Lee mas

SLIDING WEAR CHARACTERIZATION OF CEMENTED CARBIDES FOR HIGH PERFORMANCE CUTTING TOOLS

SLIDING WEAR CHARACTERIZATION OF CEMENTED CARBIDES FOR HIGH PERFORMANCE CUTTING TOOLS

In general, friction and wear is believed to result from three components: adhesion, ploughing and asperity deformations [7], several mechanisms have been proposed to explain how material is removed from the surface of WC-Co during sliding test because friction contacting bodies is a complicated phenomenon. The applied load is initially carried by only a few surface asperities, as sliding proceeds, the load is distributed over a large contact area since the surface roughness decreases. As indicated by [5,7,8] and based on the recorded responses from the sliding test, the wear resistance of WC based cemented carbides generally increases with reduced carbide grain size and decrease binder content, and thus, with increases hardness. Fig. 7 shows the values of friction coefficient, the 2608 grade have the lowest friction coefficient and the highest hardness (Fig 6), it is well know that coarse- grained cermets usually have lower abrasive wear resistance than that of fine or medium grain size and it is clear that the heterogeneity in the particles morphology and the gaps between them is obviously related to the sizes and all this is critical to the wear behavior and coefficient of friction observed in WC-Co structure. Based on the experiments completed during this test program and the interpretation of the sliding tribological testing, the following is a summary obtained in this investigation:
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8 Lee mas

Wear resistance of thermal spray WC Co VC nanostructured coatings

Wear resistance of thermal spray WC Co VC nanostructured coatings

As final conclusion, the friction coefficient of bimodal WC-Co + 2% VC coatings was less than the commercial coatings. The addition of VC in bimodal coatings resulted in a slight increase in the mechanical and wear resistance properties. The same behavior is described by Guile- many et al. [25] for bimodal WC-Co coatings, who showed lower values of friction coefficient (μ) in nanostructured systems and in commercial, both with the same chemical composition. The wear resistance of WC-Co coatings can be explained by the limited amount of debris removed during the sliding wear tests, the nanostructured WC-Co coatings contain a lower volume fraction of cobalt than commercial coatings. Therefore, it has been shown in various studies that a bimodal particle size distribution of WC improves response to wear on WC-Co coatings use conditions without lubrication (Luyckx and Machio [39]). Therefore, this work shows that a combination of micro- and nanostructures is beneficial to improve the wear resistance of WC-Co coatings.
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17 Lee mas

Wear resistant coatings: Silica sol¿gel reinforced with carbon nanotubes

Wear resistant coatings: Silica sol¿gel reinforced with carbon nanotubes

Pin-on-disc wear experiments have been carried out on sol – gel silica coatings reinforced with 0.1 wt.% carbon nanotubes (CNTs) deposited on WE54 magnesium alloy substrates by the dip-coating technique. Sol–gel solutions were fabricated using two different procedures: mechanical mixing (MM) and ultrasonic probe mixing. Dry sliding wear tests have been carried out at load of 1 N, speed of 0.1 m/s and sliding distance of 60 m. Friction coefficients were obtained from the tests and the specific wear rates (k) were calculated. The fabrication procedure of the coating influences its morphology and wear resistance. Friction coefficient was found to vary slightly with the addition of the CNTs. The wear volume of the magnesium substrate coated decreased by 40% and 80%, in terms of k, by using unreinforced and CNT-reinforced MM coatings, respectively. In MM layers reinforced with CNT uniform dispersion of the nanotubes was reached and toughening of the ceramic coating by pull-out and crack bridging mechanisms was observed.
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7 Lee mas

Wear mechanisms experienced by an automotive grade Al-Si-Cu alloy under sliding conditions

Wear mechanisms experienced by an automotive grade Al-Si-Cu alloy under sliding conditions

Various investigations have been developed to understand the effect element additions on the wear resistance of aluminium alloys. For example, Wu and Zhang[4] studied the effect of Sn on the wear characteristics of hypereutectic alloys finding that the presence of this element increased its wear resistance and modified the wear mechanisms experienced under dry sliding conditions. In a different study, Goto et al [5] found that the wear and friction of graphite impregnated aluminium-silicon alloys is considerably low under lubricated conditions which makes this material suitable for automotive applications. Al- ternatively, Clarke and Sarkar[6] found a considerable incre- ment on the wear resistance of aluminium alloys having silicon contents near to 12.6 %wt. For wear resistance applications in the automotive industry, hypereutectic aluminium alloys with silicon additions are commonly used[6-11]. It has been repor- ted that the precipitation of primary silicon particles during the solidification, increases the load bearing capacity during sliding wear of these alloys[12,13]. Even tough the existence of large primary silicon particles in hypereutectic Al-Si alloys improves wear resistance; the presence of these phases in the alloy increases considerably the cost of the final product regar- ding tooling damage during the machining practices experien- ced on the components made from this material. In addition to the silicon content in the alloy, the size and distribution of the silicon particles in the matrix also play a key role in alloy de- sign. It has been found that alloys containing small, better dis- persed silicon particles resulted with superior wear resistance, compared with alloys that did not include them[14-18]. This phenomenon is normally caused by the addition of strontium, as an element that promotes the formation of numerous nuclei, favouring silicon modification and particle dispersion. Another important aspect that promotes
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7 Lee mas

Cast Iron and the Self-Lubricating Behaviour of Graphite Under Abrasive Wear Conditions

Cast Iron and the Self-Lubricating Behaviour of Graphite Under Abrasive Wear Conditions

It has been accepted that the improvements in tribological performance is achieved when the graphite is continuously supplied into the sliding surfaces. 11 The graphite lubricating effects were investigated by Rohatgi et al. 7 on aluminium alloy-graphite particle composite, and Sarmadi et al. 12 on copper–graphite composites. They indicated that the surface and subsurface deformation, which occurred as a result of sliding; had a major influence on graphite film formation between the sliding parts. One of the main difficulties in describing the influence of matrix deformation and how it contributes to from the lubricating film is connected to the 3D complex configuration of the graphite which makes the present interpretation a little bit difficult. One of the most important factors in controlling the wear surface appearance during sliding is the hard particles. The significance of these particles was discussed elsewhere. 13 These particles are hard enough to indent and scratch the mating surfaces during the sliding condition. Therefore, micro-indentation tests were carried out close to the several graphite lamellas in order to better understanding of graphite film formation and its contribution to sliding wear.
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7 Lee mas

Study of the wear resistance due to sliding of tungsten carbide coatings.

Study of the wear resistance due to sliding of tungsten carbide coatings.

In this work tungsten carbide coatings have been deposited onto AISI/SAE 1018 steels by using a thermal spray process and by setting three types of flames viz. reducing, neutral and oxidizing. Results indicated that percent of porosity is lower in specimens made upon reducing type of flame and the microstructure is composed of semi- molten and un-molten particles, non-lamellar structure, and with presence of oxide stringers. Hardness measurements upon reducing condition resulted above 1000Hv due to presence of hard particles of WC and W 2 C. Moreover, the sliding wear resistance upon reducing condition was acceptable according to the analysis made under different testing conditions of loading and sliding time. Finally, it is concluded that tungsten carbide particles and the relatively high hardness value has strong influence on the sliding wear resistance in spite of the observed porosity.
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8 Lee mas

A sliding window based management traffic clustering algorithm for 802.11 WLAN intrusion detection

A sliding window based management traffic clustering algorithm for 802.11 WLAN intrusion detection

Abstract. This paper introduces a novel Management Traffic Clustering Algorithm (MTCA) based on a sliding window methodology for intrusion detection in 802.11 networks Active attacks and other network events such as scanning, joining and leaving in 802.11 WLANs can be observed by clustering the management frames in the MAC Layer. The new algorithm is based on a sliding window and measures the similarity of management frames within a certain period by calculating their variance. Through filtering out certain management frames, clusters are recognized from the discrete distribution of the variance of the management traffic load. Two parameters determine the accuracy and robustness of the algorithm: the Sample Interval and the Window Size of the sliding window. Extensive tests and comparisons between different sets of Sample Intervals and Window Sizes have been carried out. From analysis of the results, recommendations on what are the most appropriate values for these two parameters in various scenarios are presented.
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11 Lee mas

Tool wear monitoring using neuro-fuzzy techniques: a comparative study in a turning process

Tool wear monitoring using neuro-fuzzy techniques: a comparative study in a turning process

A four-input (i.e., time, cutting forces, vibra- tions and acoustic emissions signals) single-output (tool wear rate) model is designed and implemented on the basis of three neuro-fuzz[r]

14 Lee mas

Instrument Landing System Lateral Beam Guidance System Based on Sliding Mode Control Technique

Instrument Landing System Lateral Beam Guidance System Based on Sliding Mode Control Technique

In order to make the system more stable, the sliding mode control technique was implemented. The results showed a stable system even for low altitudes and considering external disturbances. The sliding mode controller is precise because it was designed considering the non linearities of the plant. The sliding mode control gave better results. It is recommendable to try more non linear techniques like fuzzy or H infinity which would improve the stability and the robustness as well.

7 Lee mas

Airflow patterns through a sliding door during opening and foot traffic in operating rooms

Airflow patterns through a sliding door during opening and foot traffic in operating rooms

a variety of scenarios without ventilation. They conclude that contaminant entrainment in the wake induced by human motion is the dominant transport mechanism, although backward transport (opposite to the walking motion) can also occur due to downwash effects and tip vortex formation. They also noted that transport of contaminants in the direction of movement continues due to inertia even when the subject stops. In a subsequent study, the same authors [31] simulate a human walking from a contaminated room to a clean room through a vestibule and through two hinged or sliding doors. This simulation also includes ventilation with an exhaust in the vestibule and small gaps below the doors. The authors quantify the effects of door type and walking speed on contaminant transport although they point out that pressure effects are complex. Saarinen et al. [39] use LES to investigate the transient airflows generated during human passage through a hinged and sliding door between two rooms in an isothermal environment without ventilation. They compare the results with experimental measurements taken using real scale tracers. Shih et al. [40] use the RANS method to investigate the effects of a moving person and the opening and closing of a sliding door on room pressure and velocity distributions in an isolation room with anteroom. They indicate that the internal pressure within the isolation room rises suddenly the instant the door is opened and reaches the pressure of the anteroom one second after the door is opened. When the door is closing, the internal pressure drops quickly and becomes negative again. At the instant the door is completely closed, the internal room pressure is lower than the specified negative internal pressure and then rises rapidly to achieve the specified negative internal pressure. The only study found to date which explores these phenomena in an OR was published by Balocco et al. [41]. They use the RANS method to analyse the effects on OR climate, airflow patterns and indoor pressure, of a sliding door combined with people crossing through and people carrying a stretcher. The results obtained by these authors show disruptions of the airflow inside the OR and different airflow displacement and distribution caused by surgical staff movements and sliding door opening and closing, but, in particular, static pressure changes in the HVAC plant system with important effects on ventilation system working conditions.
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20 Lee mas

Filtrado adaptativo local en el dominio de transformadas deslizantesLocal adaptive image processing in a sliding transform domain

Filtrado adaptativo local en el dominio de transformadas deslizantesLocal adaptive image processing in a sliding transform domain

Local adaptive filtering in a sliding transform domain for noise suppression, image restoration and enhancement with preservation of edges and detail boundaries represents a substantial advance in the development of signal and image processing techniques, thanks to its robustness to signal imperfections, local adaptivity (context sensitivity). Local filters in the domain of an orthogonal transform at each position of a moving window modify the orthogonal transform coefficients of a signal to obtain only an estimate of the central pixel of the window. The choice of orthogonal transform for sliding signal processing depends on many factors. The discrete cosine transform (DCT) is one the most appropriate transform with respect to the accuracy of power spectrum estimation from the observed data that is required for local filtering, the filter design, and computational complexity of the filter implementation. A minimum mean-square error estimator in the domain of a sliding DCT for noise removal and restoration is derived. This estimator is based on a fast inverse sliding DCT transform. Local contrast enhancement is performed by nonlinear modification of noised local DCT coefficients. To provide image processing at a high rate, a fast recursive algorithm for computing the sliding DCT is utilized. The algorithm is based on a recursive relationship between three subsequent local DCT spectra. Computer simulation results using real images are provided and discussed.
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138 Lee mas

Wear of the cutting tool in turning dry steel AISI 316L

Wear of the cutting tool in turning dry steel AISI 316L

The present experimental study focuses on determin- ing statistical models to predict flank wear during dry turning of AISI 316L stainless steel using two cutting inserts. Cutting parameters were compared using analysis of variance and simple regression. As a main result the significant effect of cutting feed and main time was found. Statistical models were used to estimate flank wear, as well as the mean ab- solute errors of each equation. The best performance corresponded to the GC2015 insert according to the regression equations.

6 Lee mas

Use-wear and fatty acids analyses of flaked lithic tools

Use-wear and fatty acids analyses of flaked lithic tools

El segundo es el único antecedente del cruce metodológico entre el análisis funcional y el de sustancias grasas junto al análisis de microfósiles para conocer la historia de[r]

14 Lee mas

Wear and cavitation effect in an epoxy filled with boron and silicon nanocarbides

Wear and cavitation effect in an epoxy filled with boron and silicon nanocarbides

This behaviour can be explained in terms of wear mechanisms, as anchoring between nanoparticles and resin plays a very important role. In general wear tracks present abrasive wear, as it is observed in Fig. 3, where abrasion lines are found. These abrasion lines are defined more clearly in clear resin and nanocomposites with 12% of particles, which derives in high friction coefficients. Small cracks (produced by fatigue) are also found in clear resin and 12%-addition nanocomposites (Fig. 3 A, D and E). However in nanocomposites with 6% of filler, adhesive wear also takes place. Therefore they have low wear and friction coefficient (Fig. 2). The difference found between E12SC and E12BC is due to anchoring of nanoparticles (Fig. 3 D and E). The B 4 C nanoparticles have some hydroxyls groups in their surface; these
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7 Lee mas

Prediction of Die Wear in Warm Forging Process with Forward Extrusion Operations-Edición Única

Prediction of Die Wear in Warm Forging Process with Forward Extrusion Operations-Edición Única

Table 5.3 shows the die wear depth predictions for the three press speed simulations. It can be seen that die performance is improved in the 40 spm configuration, but die life decreases in the 30 spm set up. Contact time is the parameter that influences the most in the predictions. Longer contact time reduces sliding velocity and therefore benefits the die life. However, if contact time is inappropriately long, then the factor t in the wear model affects the heat transfer and consequently die life. The mechanical press works intermittently at 50 spm, meaning that a change to a lower press speed would not represent a dramatic modification and production would not be compromised. Unfortunately die life improvement, when a 40 spm set up is used, is not significant.
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94 Lee mas

STEEL FLAT RAIL TOP MOUNT. Sliding Door Hardware Steel Flat Rail Top Mount, 96"

STEEL FLAT RAIL TOP MOUNT. Sliding Door Hardware Steel Flat Rail Top Mount, 96"

Se recomienda utilizar una guía para taladro • Fije los carros a la puerta utilizando los tornillos provistos. • Fije el tope antisalto en la parte superior de la puerta enel lado [r]

13 Lee mas

Diseño y Construcción de una Herramienta para la Simulación de los Métodos de Control PID y SLIDING Mode Control (SMC) Aplicado a un Motor BLDC

Diseño y Construcción de una Herramienta para la Simulación de los Métodos de Control PID y SLIDING Mode Control (SMC) Aplicado a un Motor BLDC

The PID and SMC (Sliding Mode Control) controllers allow a particular system to reach a desired state through feedback. This project presents the design and construction of a control test bench for the simulation of these methods through a physically stabilized balance system with a Brushless DC motor. The project development integrates the construction, electronic components, mathematical models, plant control systems and graphic interface (HMI).

75 Lee mas

Un vistazo. Inicio. Android Wear. Motorola Connect. Funciones. Correas del reloj. Deseas más? Solución de problemas. Seguridad.

Un vistazo. Inicio. Android Wear. Motorola Connect. Funciones. Correas del reloj. Deseas más? Solución de problemas. Seguridad.

Selecciona la aplicación Moto Body para contar tus pasos: en tu teléfono, presiona Aplicaciones > Android Wear , desplázate hacia abajo hasta Realizar acción con. aplicaciones del [r]

20 Lee mas

TítuloDental wear and grit ingestion in extant and extinct bears from Northern Spain

TítuloDental wear and grit ingestion in extant and extinct bears from Northern Spain

with the 13,19% tubers and roots that they are known to ingest yearly (COUTURIER, 1954), it has to be con- cluded that the consumption of these foods by the cave bear Ursus spelaeus was much lower and indeed negligible, and can not be the cause of the intense wear seen on cave bears.

7 Lee mas

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