International Journal of Surface Science and Engineering (13 papers in press)
A Study of Recognizing the Friction State of Revolute Pairs Based on the Motor Current Signature Analysis
by Naiming JIANG, Guofu Li
Abstract: The recognition of the friction state of revolute pairs can help with the monitoring of their operating conditions to avoid equipment fault and other problems due to their failure. A new method for recognizing the friction state of revolute pairs based on motor current signature analysis was proposed in this paper to solve the problems of current common means for monitoring friction state, such as involving too many devices, high costs, difficult field application and low accuracy. Current signals were decomposed and multidimensional features were extracted by variational mode decomposition, and a method for searching the extreme point was proposed according to fast Fourier transform to determine the adaptive parameter selection strategy for variational mode decomposition parameters and extract the friction features of time-frequency domain. Meanwhile, the enhanced recognition of features of time domain and frequency domain was extracted, feature redundancy was reduced by principal component analysis, and the dimension reduction sample intervals were categorized according to the variation tendency of first principal component features after dimension reduction as the training sample for the support vector machine classifier. The support vector machine was trained by ensemble learning, a combined classifier was built and the penalty factors and kernel parameters of the support vector machine were optimized by quantum particle swarm optimization algorithm to further improve recognition accuracy and thus evaluate the time period of the friction state of revolute pairs a certain point of time. The friction state of revolute pairs at this moment could be evaluated precisely after their friction feature signal was recognized by multiple types of classifiers with different classification intervals, and the time before dry friction could be preliminarily estimated. The results indicate that, the friction fluctuation during movement of revolute pairs could lead to amplitude and phase modulation of the motors stator current signal, and the modulated signal was more obvious near the baseband signal while the first principal component of multi-domain and multi-dimensional features decreased before increasing after dimension reduction, reflecting the variation of the friction state of revolute pairs. The change of the friction state of revolute pairs could be represented completely by analyzing the stator current features of the motor driving the revolute pairs and extracting the multi-domain and multi-dimensional friction features. A new idea was provided for monitoring the operating conditions of revolute pairs and related mechanisms by machine learning and recognition of the friction state of revolute pairs by multiple classifiers and classification intervals.
Keywords: revolute pairs;motor current signal;friction feature;variational mode decomposition;support vector machine.
An indentation hardness-testing temperature model for ceramics and tungsten carbides
by Jeongki Jang, Kyungmok Kim
Abstract: This article describes an indentation hardness-temperature model based on a Kachanov-type damage law. The indentation hardness of materials varies with testing temperature. It is found that the surface area of the indentation increases exponentially with the testing temperature during hardness measurements. The change rate of the total contact area of the resulting indentation can be described as a function of the indentation area itself. Two parameters, a softening coefficient and an exponent, are able to determine the change rate of the indentation area with the testing temperature. In particular, the softening coefficient is found to increase as the film thickness increases. This proposed model will enable tribologists to predict the indentation hardness of materials and quantify the influence of various factors affecting indentation hardness.
Keywords: Indentation hardness; Vickers; Temperature; Kachanov damage; Film.
Effects and characterizations of pulse electrodeposition parameters of silver in terms of scattering parameter and surface roughness for waveguides operating at high frequencies
by Caner Basaran, Ishak Karakaya
Abstract: The signal quality of antennas and waveguides in the transmission of electromagnetic waves are very much dependent on the surface finish of these devices. The use of pulse current produces homogenous deposits of better surface finish than direct current. Effects of pulse parameters on the surface properties of silver coatings of the copper substrates have been analyzed in terms of surface roughness and S-parameter (scattering parameter). Grain size and morphology of silver coatings were characterized by SEM and XRD. The duty cycle, frequency and average current density were used as three pulse parameters. Three levels were selected for each parameter in the experimental design. The surface finish was found to be directly proportional to duty cycle and average current density but inversely proportional to frequency. The S11 scattering parameter observations were made relative to a gold-plated reference coupon. It was analyzed that the smoother surface had more reflection power in terms of S11 parameter thus decreasing the loss of radiation. Scanning Electron Microscope (SEM) was used to characterize the microstructure of silver plating. As a result of SEM analysis, pyramidal growth was obtained with pulse electrodeposition. Smaller grains and fewer valleys in the grain morphology were detected with the increasing average current density at high frequencies and high duty cycles. Irregularity was observed in the grain structure with decreasing average current density. According to X-Ray diffraction (XRD) analysis, smaller silver grains were observed at high duty cycle, high frequency and high average current density. Effects of pulse parameters on the diffusion of silver into the copper base material were analyzed by Energy-dispersive spectrometer (EDS) line analysis.
Keywords: Silver plating; pulse electrodeposition; morphology; grain size; scattering parameter; return loss.
An Experimental Study on the Surface Roughness of Galvannealed Low Carbon Al-killed and Ti-Nb Stabilized Interstitial Free Steels
by Candan Sen Elkoca, Bulent Ekmekci, Oktay Elkoca
Abstract: This study elucidates the surface microstructures forming surface roughness during the galvannealing process and establish relations between surface roughness, galvannealing process parameters, and coating iron content. Galvannealed low carbon Al-killed (AK) and Ti-Nb stabilized interstitial free (IF) steels were used to simulate the industrial galvannealing process using different annealing temperatures and times.
The craters were observed on the galvannealed coatings, resulting in high surface roughness. An exponential behaviour of the surface roughness was displayed with increasing annealing time at each annealing temperature in both steel coatings, which was in an increasing order in the AK steel coating, whereas in a reverse order in IF one. The increasing iron content in the coatings indicates a decrease in surface roughness with the cubic ?1k phase, favourable for the subsequent forming process.
Keywords: galvannealing; hot-dip galvanizing; Fe-Zn phases; surface roughness; surface morphology.
Electric Discharge Coating process variation and its wear Properties
by Ilangovan Arun, Yuvaraj C, Chandra Sekhar Reddy G
Abstract: In the present study elaborates about process variation of Electrical Discharge coating process through powder mixed and powder metallurgy (semi-sintered) electrode that influences mechanical and metallurgical properties of over duplex stainless are compared. Occurrences of surface roughness, poke, splatters and carters are minimal in deposition of pyrolysis carbon while using the powder metallurgical electrode process of deposition than powder mixed. Coating layer thickness and porosity are greater in powder mixed having similar decarburizing depth that deserves hardness values with an average of 1001HV to 1010HV across its section. Pyrolysis carbon restricts alloying element deposition that reduced frictional coefficient with greater wear rate compared with powder metallurgical process. The metallurgical characterization are performed through scanning electron microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Phase identification through X-ray powder diffraction (XRD), Optical Microscope (OM), mechanical testing through Vickers Microhardness, and wear testing by Pin-On-Disc (POD) tribometer.
Keywords: Electrical Discharge Coating; Porosity; decarburizing depth; phase transformation carbon flakes; hardness; wear.
Comparative EIS study of Titanium based materials in high corrosive environments
by Pedro P. Socorro Perdomo, Nestor R. Florido Suárez, Amparo Verdú-Vazquez, Julia C. MIrza Rosca
Abstract: Electrochemical Impedance Spectroscopy (EIS) is a technique relatively complex and modern that owes its existence to the emergence of electronic circuits. In this work, the behavior in HCl 20% of three materials, Ti, Ti-15 Mo and Ti-15Mo-5Al fabricated by laser beam melting, was analyzed using EIS. Impedance spectra have been obtained at various potentials, from open circuit potential to +2.0 V vs. Ref. Once the profiles of the impedance spectra were analyzed, the experimental data were adjusted to an equivalent electrical model. Two models of equivalent circuits were presented: at Ecorr simple circuit is used while in the passive potential range an equivalent circuit with 2 time constants was used for fit the experimental data. It was concluded that titanium and studied titanium alloys undergo spontaneous passivation due to the oxide film formed on their surface in the reducing acid solution
Keywords: Titanium; Titanium alloys; equivalent circuit; EIS; HCl; corrosión.
Fretting behavior of textured Ti-6Al-4V alloy under oil lubrication
by Wenhui Cao, Tianchang Hu, Hengzhong Fan, Qi Ding, Litian Hu
Abstract: The micro-textures with different dimples densities and diameters are prepared on the Ti-6Al-4V surfaces. The influences of surface texture parameters on the fretting wear behaviors of TC4 self-matching pair have been investigated by using a pin-on-disk machine in a reciprocating sliding mode under different applied loads and fretting frequencies at oil lubrication. Results indicated that the proper texture on titanium alloy can greatly improve the fretting tribological properties under different loads. The 10% texture density surface showed the minimum wear volume at a low fretting frequency, whereas the 20% texture density surface had the lowest wear volume at a high fretting frequency. Under the tested condition, the surface with dimple diameter of 50 ?m had the best anti-fretting wear performance under the applied fretting frequencies. In addition, the mechanisms for friction-reducing and anti-wear were discussed. The existence of surface texture promoted the transition from dry friction to boundary lubrication state under high fretting frequency, and the dimples can effectively capture wear debris to alleviate the abrasive wear of the material.
Keywords: Metal wear; Fretting; Surface texture; Oil lubrication.
System kinetics characteristics of multi-parameter coupling of rolling mill based on mixed lubrication process of rolling interface
by Qiaoyi Wang, Pengcheng Yu, Han Wang, Xin Jiang, Huijun Zhao
Abstract: Based on the theories of rolling, hydromechanics and vibration, a multi-parameter coupling kinetic model was established, in which the interface friction, geometric constraint and stress distribution were modeled for dynamic roll gap. A quantitative analysis was performed on the key parameters affecting the amplitude and critical speed of vertical vibration of the rolling mill. The variation of friction stress and compressive stress in the work zone with time was analyzed systematically when the rolling mill was in the mixed lubrication state with a constant reduction rate and surface roughness. The results reveal that the critical vibration speed is directly proportional to the thickness of the workpiece in the outlet zone, the surface roughness of the roll and workpiece, and the roll radius, but inversely to the lubricant viscosity and the thickness of the workpiece in the inlet zone. The amplitude is proportional to the rolling speed, and the compressive and frictional stresses are inversely proportional to the post-tensile stress.
Keywords: rolling interface; mixed lubrication; multi-parameter coupling; kinetics characteristics; reduction rate.
Enhanced hardness and friction behavior of 40Cr steel by Laser Surface Texturing after Ultrasonic Surface Rolling
by Yang Zhou, Genshang Wu, Jinggan Shao
Abstract: This paper construct a new type of wear-resistant layer on material surface by laser surface texturing and ultrasonic surface rolling. Different from the traditional anti-wear layer, there is no obvious mechanical property difference between the anti-wear layer and material matrix, which can effectively prevent the anti-wear layer falling off and improve fatigue life of material. Meanwhile, the anti-wear layer can also collect wear debris. A hardening layer is formed on the material surface by ultrasonic rolling, and then the surface texturing is machined on the hardening layer by laser. The friction behavior of anti-wear layer is studied by friction and wear experiment. The experimental results show that the new anti-wear layer has low friction coefficient and surface roughness. The specimen with Laser Surface Texturing(LST) and Ultrasonic Surface Treatment(USR) has more smaller wear depth under the same conditions.
Keywords: Laser Surface Texturing; Ultrasonic Surface Rolling; anti-wear layer; friction coefficient; wear depth.
Coatings with embedded particles to increase interfacial anchorage of steel and GFRP rebars in concrete
by Jose De Jesus Perez Bueno, Jorge Luis Soto Corral, José Luis Reyes Araiza, Maria Luisa Mendoza López, Alejandro Manzano-Ramírez
Abstract: The conventional structures of concrete are reinforced and pre-strengthened with rebars and steel wires. Initially, the steel is protected against corrosion by forming a passive layer due to the alkalinity of the concrete. Nevertheless, once it was lost, either by carbonation or another factor, the corrosion is reactivated, propitiating the flaw of the reinforcement element. This can cause concrete breakage due to increased volume for transforming the metallic iron into iron oxides. In this research, three different types of coatings were studied: sol-gel silica, an organic polymer (bisphenol A-fumarate), and an organic-inorganic hybrid nanometric compound. This work proposes the addition of particles of about 5 mm in size, heterogeneously distributed, such as recycled glass on the coatings or sand to gain mechanical anchorage between the coated steel rebars and the concrete. This surface change was tested in rebars of fiber-reinforced polymer (GFRP) with fiberglass. The result was that this factor increased the force required for the extraction of the rebars. The low thickness of sol-gel SiO2 coatings made with TEOS did not turn out to be suitable for this application. The coatings with polymeric resin were suitable, offering protection against corrosion in an economical and straightforward form. The organic-inorganic hybrid coatings, possessing properties of organic and inorganic constituents, and using silane coupling agents, provide coatings with adequate protection but depending on the preparation process and a cost increase regarding the polymeric resin.
Keywords: Hybrid coatings; Concrete; Sol-gel; Corrosion; Fly ash.
Metallization of High Density Polyurethane Surfaces
by Busra Unlu, Yahya Oz, Metehan Erdogan, Ishak Karakaya
Abstract: Electroplating onto polymeric materials is required for different purposes in various applications. Commercial polyurethanes (PU) are electrically insulator materials and durable at high temperatures. Nevertheless, the PU used in this study has a relatively higher electrical conductivity, lower thermal expansion and is a high density foam. In this work, surface metallization of PU foam was studied to prepare the surface for subsequent electroplating processes. Surface metallization was carried out by sensitization, activation and electroless nickel (Ni) plating. Metallized surfaces were characterized according to surface morphologies after electrochemical Ni plating at different current densities and surface preparations. Roughness as well as electrical conductivity of the coatings were investigated. The results show that increasing current density adversely affects the surface morphology and metallization processes enhance the surface conductivity of the foam.
Keywords: Aerospace Engineering; Electroless Plating; Foam Surface; Metallization; Nickel Coating; Tool Materials.
Improving the Abrasion Resistance of AISI 304L Metallic Biomaterial by Microwave Boriding
by Dilek Arslan, Recep Onur Uzun
Abstract: Metallic materials are used as biomaterials thanks to their high mechanical properties. However, their low resistance to corrosion and abrasion reduces the biocompatibility of metallic biomaterials. In this study, the abrasion resistance of AISI 304L stainless steel material, which is a widely used metallic biomaterial, was improved by pack-boriding with microwave hybrid heating. For this purpose, AISI 304L SS material was pack-borided by using EKABOR II boriding powder for 2, 4 and 6 hours in a microwave oven with a power of 2.9 kW and a frequency of 2.45 GHz at temperatures of 850, 900 and 950
Keywords: microwave hybrid heating; pack-boriding; metallic biomaterial; abrasion resistance.
Influence of silica surface modification on poly(butyl acrylate-co-methyl methacrylate)/silica emulsion stability
by Zrinka Buhin Sturlic, Mirela Leskovac, Sanja Lucic Blagojevic
Abstract: The application of emulsion polymerization for nanocomposite material synthesis is still a problem since it is difficult to achieve emulsion stability and desirable morphology. In this work, the in situ emulsion polymerization procedure was optimized in order to prepare stable polyacrylate (PA) systems with 15 wt % of modified silica. The surface of the silica was modified with nonionic emulsifier (NE), cationic initiator 2,2'-azobis(2-amidinopropane) dihydrochloride (AIBA) and 3-methacryloxypropyltrimethoxysilane (MPS). The adsorption conditions, the influence of monomer mode addition, the rate of pre-emulsion addition, monomer/water ratio, the pH and the amount of anionic emulsifier (SDS) on polyacrylate/silica emulsion stability were investigate. The results showed that the most significant influence on emulsion stability have the amount of anionic emulsifier and silica surface modification. This work contains practical knowledge regarding adsorption of nonionic emulsifier, emulsion stability, filler surface modification and in situ emulsion polymerization with high amount of modified silica (15 wt %) and monomer/water ratio 70/100.
Keywords: emulsion polymerization; polyacrylate; nanosilica; surface modification.