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3032 KiB

Open AccessArticle

The Analysis of Three-Body Contact Temperature under the Different Third Particle Size, Density, and Value of Friction

by Horng-Wen Wu, Yang-Yuan Chen and Jeng-Haur Horng

Micromachines 2017, 8(10), 302; https://doi.org/10.3390/mi8100302 - 11 Oct 2017

Cited by 16 | Viewed by 4178

Recently, many studies have investigated the friction, wear, and temperature characteristics of the interface between two relative movements. Such analyses often set the coefficient of friction as a fixed value and are analyzed in cases of two-body contact; however, the interface is often [...] Read more.

Recently, many studies have investigated the friction, wear, and temperature characteristics of the interface between two relative movements. Such analyses often set the coefficient of friction as a fixed value and are analyzed in cases of two-body contact; however, the interface is often a three-body contact and the coefficient of friction varies depending on the operating conditions. This is a significant error in the analysis of contact characteristics, therefore, in this study, the actual interface and the change of the coefficient of friction were analyzed based on three-body micro-contact theory where the contact temperature was also analyzed and the difference between the generally assumed values were compared. The results showed that under three-body contact, the coefficient of total friction increased with an increase in particle size; and at a different particle size and area density of particles, the surface contact temperature increased with the plasticity index and load increases, and the particle contact temperature increased with the increasing particle size. The surface temperature rise was mainly affected by the ratio of the average temperature between surface 1 and surface 2 to the multiplication between the 100th root of the area density of particles and the square root of the equivalent surface roughness (T_s_{1s2_ave}^*/η_a^0.01σ^0.5) and the ratio of the 10th root of the mean particle diameter to the 100th root of the equivalent surface roughness (x_a^0.1/σ^0.001). Particle temperature was mainly affected by the ratio of the 10th root of the mean particle diameter to the 100th root of the equivalent surface roughness (x_a^0.1/σ^0.001) and the area density of particles η_a. Our study indicated that when the contact of surface with surface and the contact of the particles with the surface, the resulting heat balance was assigned to the particles and the surface in a three-body contact situation. Under this contact behavior, it could avoid a too high a rise in micro-contact temperature to achieve the material failure temperature. Full article

(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)

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6515 KiB

Open AccessArticle

Effects of Environmental Gas and Trace Water on the Friction of DLC Sliding with Metals

by Yoshihiro Kurahashi, Hiroyoshi Tanaka, Masaya Terayama and Joichi Sugimura

Micromachines 2017, 8(7), 217; https://doi.org/10.3390/mi8070217 - 11 Jul 2017

Cited by 15 | Viewed by 4937

Abstract

This paper describes an experimental study on the friction of a-C:H diamond-like carbon (DLC) and ta-C DLC coatings in gas with different concentration of trace water. Pin-on-disk sliding experiments were conducted with DLC coated disks and aluminum pins in hydrogen, nitrogen, and argon. [...] Read more.

This paper describes an experimental study on the friction of a-C:H diamond-like carbon (DLC) and ta-C DLC coatings in gas with different concentration of trace water. Pin-on-disk sliding experiments were conducted with DLC coated disks and aluminum pins in hydrogen, nitrogen, and argon. Trace oxygen was eliminated to less than 0.1 ppm, while water in the gas was controlled between 0 and 160 ppm. Fourier transform infrared spectroscopy (FT-IR) and laser Raman spectroscopy were used to analyze the transfer films on the metal surfaces. It was found that trace water slightly increased friction in hydrogen gas, whereas trace water caused a significant decrease in the friction coefficient in nitrogen and argon, particularly with a-C:H DLC. The low friction in hydrogen was brought about by the formation of transfer films with structured amorphous carbon, but no differences in the structure and contents of the films were found in the tests with and without trace water. In nitrogen and argon, the low friction with a-C:H DLC was achieved by the gradual formation of transfer films containing structured amorphous carbon, and FT-IR spectra showed that the films contained CH, OH, C–O–C, and C–OH bonds. Full article

(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)

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4139 KiB

Open AccessArticle

Motor Power Signal Analysis for End-Point Detection of Chemical Mechanical Planarization

by Hongkai Li, Xinchun Lu and Jianbin Luo

Micromachines 2017, 8(6), 177; https://doi.org/10.3390/mi8060177 - 5 Jun 2017

Cited by 7 | Viewed by 6512

Abstract

In the integrated circuit (IC) manufacturing, in-situ end-point detection (EPD) is an important issue in the chemical mechanical planarization (CMP) process. In the paper, we chose the motor power signal of the polishing platen as the monitoring object. We then used the moving [...] Read more.

In the integrated circuit (IC) manufacturing, in-situ end-point detection (EPD) is an important issue in the chemical mechanical planarization (CMP) process. In the paper, we chose the motor power signal of the polishing platen as the monitoring object. We then used the moving average method, which was appropriate for in-situ calculation process and made it easy to code for software development, to smooth the signal curve, and then studied the signal variation during the actual CMP process. The results demonstrated that the motor power signal contained the end-point feature of the metal layer removal, and the processed signal curve facilitated the feature extraction and it was relatively steady before and after the layer transition stage. In addition, the motor power signal variation of the polishing head was explored and further analysis of time delay was performed. Full article

(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)

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10842 KiB

Open AccessArticle

Hydrodynamic Simulation of an Orbital Shaking Test for the Degradation Assessment of Blood-Contact Biomedical Coatings

by Wen-Jin Cherng, Zuo-Syuan Dong, Chau-Chang Chou, Chi-Hsiao Yeh and Yu-Heng Pan

Micromachines 2017, 8(4), 132; https://doi.org/10.3390/mi8040132 - 19 Apr 2017

Cited by 8 | Viewed by 5777

Abstract

Biomedical coatings are used to promote the wear resistance and the biocompatibility of a mechanical heart valve. An orbital shaking test was proposed to assess the durability of the coatings by the amount material eroded by the surrounding fluid. However, there is still [...] Read more.

Biomedical coatings are used to promote the wear resistance and the biocompatibility of a mechanical heart valve. An orbital shaking test was proposed to assess the durability of the coatings by the amount material eroded by the surrounding fluid. However, there is still a lack of understanding with regards to the shaker’s rotating conditions and the corresponding physiological condition. This study implemented numerical simulations by establishing a fluid dynamic model to evaluate the intensity of the shear stress under various rotating speeds and diameters of the shaker. The results are valuable to conduct in vitro tests for estimating the performance of biomedical coatings under real hemodynamic conditions and can be applied to other fluid-contact implants. Full article

(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)

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4188 KiB

Open AccessArticle

Design and Construction of a Micro-Tribotester for Precise In-Situ Wear Measurements

by Oleksiy V. Penkov, Mahdi Khadem, Andy Nieto, Tae-Hyeong Kim and Dae-Eun Kim

Micromachines 2017, 8(4), 103; https://doi.org/10.3390/mi8040103 - 28 Mar 2017

Cited by 23 | Viewed by 5035

Abstract

Extensive research efforts have been devoted to understand the complex mechanisms of wear with the aim to minimize wear in sliding systems. Improvements in the instruments used for the characterization of the wear phenomenon are required to enhance the effectiveness of research method. [...] Read more.

Extensive research efforts have been devoted to understand the complex mechanisms of wear with the aim to minimize wear in sliding systems. Improvements in the instruments used for the characterization of the wear phenomenon are required to enhance the effectiveness of research method. In this paper, we report the design of an experimental platform that enables in-situ observation of the surface topography evolution during the evaluation of the tribological behavior of surfaces in dry and lubricated conditions. Use of state-of-the-art components for surface topography measurement, planar positioning, and force sensing allowed for the improvement of sensitivity and resolution compared with the previously reported systems. The effectiveness of the tribotester was demonstrated through friction and wear tests performed using a stainless-steel ball and a silicon wafer coated with SiO₂. It was found that transition of the wear mechanism from adhesive to abrasive wear took place when a significant amount of wear debris was formed as evidenced by the in-situ observation of removal of the coating and exposure of the Si substrate. The in-situ observation of wear phenomena enabled a robust and in-depth elucidation of wear mechanisms. Full article

(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)

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9158 KiB

Open AccessArticle

Large-Area Piezoelectric PVDF Fibers Fabricated by Near-Field Electrospinning with Multi-Spinneret Structures

by Cheng-Tang Pan, Kuo-Chang Tsai, Shao-Yu Wang, Chung-Kun Yen and Yan-Liang Lin

Micromachines 2017, 8(4), 97; https://doi.org/10.3390/mi8040097 - 24 Mar 2017

Cited by 13 | Viewed by 6097

Abstract

In the study, we improved the near-field electrospinning (NFES) by multi-spinnerets with a cylindrical collector to fabricate a large area permanent piezoelectric of polyvinylidene fluoride (PVDF) fibers array. We designed multi-spinnerets by using printed circuit board (PCB) and drilled spinnerets on the solder [...] Read more.

In the study, we improved the near-field electrospinning (NFES) by multi-spinnerets with a cylindrical collector to fabricate a large area permanent piezoelectric of polyvinylidene fluoride (PVDF) fibers array. We designed multi-spinnerets by using printed circuit board (PCB) and drilled spinnerets on the solder balls. With different process parameters, we can obtain different diameters of PVDF fibers. By using the Taguchi method analysis, we found that the optimum sample of PVDF fiber arrays were manufactured by an electrical field of 1.6 × 10⁷ V/m. The cylindrical collector with high tangential velocity of 1779.9 mm/s and the heat treatment temperature of 65 °C for one hour. In addition, we used X-ray diffraction (XRD) and scanning electron microscopy (SEM) to analyze β-phase crystal quality and the surface character of PVDF fibers, respectively. From the observation of XRD, it revealed a high diffraction peak at 2θ = 20.6° of piezoelectric crystal β-phase structure. As PVDF solution with concentration of 18 wt % and the conductivity of 44.2 μS/cm was electrospun via NFES with multi-spinneret structure, we obtained a smooth manufacturing process. When the periodical tapping frequency was applied with 9 Hz, the maximum peak voltage of 86.9 mV was generated. In a cicada’s wing test, when the tapping frequency input was applied during 10–50 Hz, the maximum output voltage signals of 6.2 mV were generated. Full article

(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)

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4764 KiB

Open AccessArticle

Effects of Doping Elements on the Friction and Wear of SUJ2 Steel Sliding against Aluminum Alloys

by Yuh-Ping Chang, Zi-Wei Huang and Huann-Ming Chou

Micromachines 2017, 8(4), 96; https://doi.org/10.3390/mi8040096 - 23 Mar 2017

Cited by 8 | Viewed by 3744

Abstract

Damage to mechanical components caused by wear is considered to be an important issue for mechanical engineers. For the purpose of wear resistance, it is necessary to improve the material properties of the mechanical elements. Furthermore, low friction plays an important role in [...] Read more.

Damage to mechanical components caused by wear is considered to be an important issue for mechanical engineers. For the purpose of wear resistance, it is necessary to improve the material properties of the mechanical elements. Furthermore, low friction plays an important role in saving energy. Hence, it is important to establish a key technology for wear resistance and low friction through appropriate materials science for related industries. In general, the tribological properties of aluminum alloys are very different from those of steels. Hence, aluminum alloys should be specially considered and clarified for their tribological properties before being applied industrially. This paper therefore aims to further investigate the effects of the content of doping elements on the friction and wear of the selected aluminum alloys. From the experimental results, it can be concluded that the higher the Si content, the smaller the friction coefficient, and the milder the variation. The higher the content of iron and copper, the more materials are removed, showing better machinability. Moreover, three frictional models and wear mechanisms that describe the effects of the content of doping elements on the friction and wear are proposed. The wear mechanisms change as the silicon content increases, from the junction growth to the wedge and the ploughing particles. As a result, better choices of aluminum alloys with regards to friction and wear can then be made. These results have great practical importance. Full article

(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)

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5445 KiB

Open AccessArticle

Investigation of Adhesive Resistance of Aluminum Alloy by Sandblasting and Electrochemical Machining

by Jianbing Meng, Xiaojuan Dong, Haian Zhou, Weihong Liu and Zhanmin Yin

Micromachines 2017, 8(3), 91; https://doi.org/10.3390/mi8030091 - 17 Mar 2017

Cited by 4 | Viewed by 5879

Abstract

A novel method for fabricating an adhesive resistance surface is presented. Sandblasting and electrochemical machining were introduced to prepare micro-nano structures on the sample surface. Then, the prepared sample was immersed in a tridecafluoroctyltriethoxysilane ethanol solvent. The surface of the aluminum alloy sample [...] Read more.

A novel method for fabricating an adhesive resistance surface is presented. Sandblasting and electrochemical machining were introduced to prepare micro-nano structures on the sample surface. Then, the prepared sample was immersed in a tridecafluoroctyltriethoxysilane ethanol solvent. The surface of the aluminum alloy sample roughened and covered with low-surface-energy chemical groups was examined by scanning electron microscope (SEM) and atomic force microscope (AFM). Surface wettability and adhesive resistance of the treated sample were characterized by water contact angles, area fraction, sliding angle and solid surface energy. Furthermore, the effects of some process parameters, such as sand size, current density, electrochemical machining time, and electrolyte concentration, on the contact angle, area fraction, sliding angle and the solid surface-energy of the modified sample surfaces were provided. The results show that the combination of binary micro-structures and surface modification of tridecafluoroctyltriethoxysilane plays a role to improve adhesive resistance of the aluminum alloy surface. Full article

(This article belongs to the Special Issue Microtribology, Adhesion and Surface Engineering)

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