Papers by Keyword: Surface Topography

Abstract: The properties of graphene chips with low reproducibility (LR) after photolithography (PLG) and graphene functionalization have been studied. It is shown that the introduction of additional cleaning after PLG can significantly increase the reproducibility of the parameters of processed graphene in biosensors. The use of dilute PBS solutions for virus detection makes it possible to increase the relative concentration sensitivity of biosensors by several times.

Abstract: The generation of the surface topography in machining is a complex process whereby the dynamics of the machine-tool and the kinematics of the cutting process are combined. The purpose of developing a surface topography simulation model in turning is to predict the combined effect of the tool geometry, process parameters, and relative tool-workpiece vibration. The simulations demonstrate that a single vibration frequency can generate multiple wavelengths on the workpiece profile. The correlation between machine-tool vibrations and surface topography is applied to accurately diagnose the machine defect that results in poor surface quality in a cylindrical turning process.

Abstract: Paperboard based packaging products are renewable alternatives for packages made traditionally from oil-based polymer materials and can be used for packaging of various products [1]. Embossing is used in packaging solutions to increase the functionality and appearance of the products. It can also be used to increase product safety by improving distinctiveness and identifiability of packages [2]. The aim of the study was to evaluate the patternability of various fibre-based materials. It was desired that the accuracy and details of the embossed pattern would be the same in all samples, regardless of their different material properties. The realization of this was evaluated by several analyses related to the performance of the materials in the embossing process. Eleven different sample materials were collected for the experiments so that the patternability could be studied extensively. The common denominator of the materials selected for testing was that they were all fibre-based paper and paperboard materials used in the packaging industry. Set of embossing tools were developed, and precision machined from brass, for the experiments. A laboratory scale mechanical embossing device was utilized in modification of sample surfaces to study patternability of selected fibre-based sample materials. The main variables in the forming experiments were pressing force and tool temperature. The samples were observed primarily visually - with the naked eye, with a scanning electron microscope and a 3D-profilometer which was used in the topography analysis of the achieved patterns. The results of the embossing test series confirmed that the height of the pattern increased as a function of pressing force and plate temperature and spring back occurred in all materials after the tool plates opened. It was deduced that the pattern dimensions of the embossing plate somewhat determined the achievable pattern height in the fibre-based sample materials, but the amount of springback did not change as a function of material thickness. Despite this finding, it was consistent that the amount of spring back was regularly reduced with higher tool temperatures. The optimization study of the magnitude of the forming force showed that excessive use of force is not required, which is beneficial in reducing the risk of material damage during processing and adjustment of embossing devices. All samples differing significantly from each other were found to be suitable for embossing, indicating that patterns such as those tested could be added to a variety of packaging applications.

Abstract: In order to study the influence of different initial topography on the molten pool flow under a moving heat source, the finite element analysis method was used to establish a two-dimensional transient model of laser polishing to simulate the evolution of the surface topography of the material during laser polishing. In the simulation process, a moving laser beam was used as the heat source, and the free surface of the actual material was profiled through a three-dimensional profiler. A very similar simulation model surface was constructed, coupled with the flow field and temperature field in the laser polishing process, and the capillary force was considered comprehensively. Combined with thermocapillary force. The results show that under the combined action of capillary force and thermocapillary force, the surface of the polished material has a peak-filling effect, which makes the surface of the material achieve a good polishing effect. The initial shape will affect the polishing effect, the greater the curvature, the faster the flow rate of the molten pool. In molten pools with large spatial curvatures, capillary forces dominate. Keywords: Laser polishing; molten pool; surface topography; numerical analysis; capillary force; thermocapillary force.

Abstract: Due to experimental limitations, sometimes it is challenging to tackle the thorough change in asperity characteristics (contact pressure, real area of contact, asperity radius), which demands a more suitable analytical model for prediction of such characteristics. This work demonstrates an approach for modeling sliding wear that provides an insight into the evolution of surface topography with operational cycles. The wear model is applied on various engineered surfaces to study the change in surface topography with wear cycles. It is concluded that different engineered surfaces nearly with same roughness demonstrate totally different behavior during sliding wear. It is observed that milled surface in comparison to turned, honed and grinding surfaces experiences minimum contact pressure due to very high correlation length. Within the range of wear cycles, maximum increase in the asperity radius is observed for milled surface.

Abstract: Surface topographies play a critical role in controlling friction, surface damage and transfer layer formation in engineering applications; hence understanding this is of great importance. In this work, experimental studies were carried out to understand the influence of surface topography on friction, scuffing and transfer layer formation in completely immersed lubricated sliding interactions. For this, sliding experiments were carried out in sphere on flat configuration using EN31 steel flats and Tungsten Carbide pin countersurface. Perpendicular and parallel surface topographies were induced onto the steel flats. Experiments were conducted at high normal loads of 1000N, 2000N and 3000N. The results show that Surface topography has a significant influence on the frictional response. When the topography directionality was perpendicular to the sliding direction, scuffing was observed only at a high load of 3000N. A ‘peak friction’ was also observed during the occurrence of scuffing. When the directionality in topography was parallel to sliding direction, scuffing and surface damage occurred from 2000N itself, accompanied by a high amount of transfer layer formation. This can be attributed to the directionality of parallel topography, which displaces away the lubricant during sliding interaction, creating metal-to-metal contact and hence leading to scuffing and higher transfer layer formation.

Abstract: The influence of surface topography on the corrosion behaviors of DP590 steel was studied by damp heat tests and electrochemical measurements in this paper. Results show that the corrosion behaviors of DP590 steel cannot be evaluated by using average surface roughness (Sa) due to the little difference of surface roughness. Reduced valley depth (Svk) showed a good correlation with corrosion resistance in the potentialdynamic polarization test, and the greater Svk, the better the corrosion resistance. Furthermore, DP590 sample with higher proportion of peak on the surface tended to have more corrosion points during the damp heat test since peaks were electrochemically active.

Abstract: This paper presents the experimental work of the surface roughness, surface topography, elementary analysis and microhardness of wire electro-discharge (WEDM) machining of grade 5 titanium alloy (Ti-6Al-4V). Ti-6Al-4V has wide range of application in alloys due to its superior mechanical properties such as corrosion resistance, high tensile strength and toughness. Based on its great hardness value, conventional machining leads to high rates of tool wear, thus, WEDM is an alternative to manufacture Ti-6Al-4V, in which better surface characteristics can be produced. This work explores the surface integrity of Ti-6Al-4V alloy after WEDM in different input parameter. From the experimental work, good surface integrity can be achieved with low peak current. The scanning electron microscope (SEM) analysis depicted the appearance of craters, crack, recast layer and globule of debris on the machined surface. Within the chemical composition on the machined surface, titanium seizes the highest percentage as there is no alternation of the metallurgical structure of the parent material. The microhardness value gradually increases from the machined surface to the parent material of Ti-6Al-4V due to over-aging of the machined surface and the work hardening during the process.

Abstract: A resistance of cavitation erosion-corrosion of the AISI 420 martensitic stainless steel was evaluated in this study. The cavitation resistance of this stainless steel has been examined using an ultrasonic vibratory method by applying water-voltage combination effect. The curves of cumulative material loss and erosion rate were attained and discussed. In addition, surface topography and scanning electron microscope (SEM) micrographs have been utilized to characterize the eroded surface after the cavitation test. The results have been compared with previously obtained results for the AISI 1040 steel. The cavitation results showed that the AISI 420 steel has exhibited the better resistance to cavitation comparing with the AISI 1040 steel under the similar test conditions. The total cumulative material loss of the AISI 420 was approximately three times less than that of the AISI 1040. Surface topography and SEM micrographs showed that the severity of damage of the AISI 1040 was found to be a higher compared to that of the AISI 420 steel.

Abstract: In this study, two Ni-based coating materials, namely NiCrMoNb and NiCrBSi, have been applied using High Velocity Air Fuel (HVAF) thermal spraying process. The performance of the coated surface in resistance to cavitation erosion-corrosion of both coating materials, has been evaluated using an ultrasonic vibratory method. The cumulative material loss and erosion rate curves of the two coatings have been discussed. Surface topography, microhardness, macroscopic images, and scanning electron microscope (SEM) micrographs were used to characterize the coatings before and after the cavitation test. The cavitation results showed that the NiCrMoNb coating surface has exhibited better performance than the NiCrBSi coating surface under the same test conditions. The total cumulative weight loss of the NiCrMoNb coating was about 1/3 that of the NiCrBSi coating. SEM micrographs of the eroded surfaces showed that the surface layer of the NiCrBSi coating was more damaged, compared to layer of the NiCrMoNb coating. Overall, the NiCrMoNb coating can be effectively used against the cavitation wear, due to its superior performance.