| 1. |
- Frangoudis, Constantinos, et al.
(författare)
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Experimental analysis of the CNx nano-damping material’s effect on the dynamic performance of a milling process
- 2013
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Ingår i: Proceedings of the International Conference on Advanced Manufacturing Engineering and Technologies. - Stockholm : KTH Royal Institute of Technology. - 9789175018928 ; , s. 293-302
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Konferensbidrag (refereegranskat)abstract
- Vibration phenomena are a main consideration during the material removal operation, as it has prominent effects on the product quality, cutting tool life, and productivity of that machining operation. Within the context of machining performance, role of enhanced stiffness and damping on the dynamic behaviour of machining systems such as turning and milling is well established. In this experimental analysis, investigations have been conducted for identifying the natural characteristics and dynamic responses of a milling process with the application of a novel carbon based (CNx) nano-composite damping material. TheCNx material has been applied into the joint interface of a workholding device with adaptive dynamic stiffness. Prior investigations of this material, produced by theplasma enhanced chemical vapor (PECVD) process, showed inherent damping capacity via interfacial frictional losses of its micro-columnar structures. For thisstudy, natural characteristics of the workholding system have been characterized bythe modal impact testing method. Dynamic responses during the machining processhave been measured through the vibration acceleration signals. The ultimate objective of this study is to comprehend the potentiality of CNx coating material forimproving machining process performance by analyzing the frequency response functions and measured vibration signals of the investigated milling process with varying stiffness and damping levels.
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| 2. |
- Fu, Qilin, 1986-, et al.
(författare)
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High dynamic stiffness mechanical structures with nanostructured composite coatings deposited by high power impulse magnetron sputtering
- 2016
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Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 98, s. 24-33
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Tidskriftsartikel (refereegranskat)abstract
- Nanostructured Cu:CuCNx composite coatings with high static and dynamic stiffness were synthesized by means of plasma-enhanced chemical vapor deposition (PECVD) combined with high power impulse magnetron sputtering (HiPIMS). Scanning electron microscope (SEM) images and energy-dispersive X-ray spectroscopy (EDS) mapping from cross-sectioned samples reveals a multi-layered nanostructure enriched in Cu, C, N, and O in different ratios. Mechanical properties of the coatings were investigated by Vickers micro-indention and model tests. It was observed that copper inclusions as well as copper interlayers in the CNx matrix can increase mechanical damping by up to 160%. Mechanical properties such as hardness, elastic modulus and loss factor were significantly improved by increasing the discharge power of the sputtering process. Moreover the coatings loss modulus was evaluated on the basis of indentation creep measurements under room temperature. The coating with optimum properties exhibited loss modulus of 2.6 GPa. The composite with the highest damping loss modulus were applied on the clamping region of a milling machining tool to verify their effect in suppressing regenerative tool chatter. The high dynamic stiffness coatings were found to effectively improve the critical stability limit of a milling tool by at least 300%, suggesting a significant increase of the dynamic stiffness.
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| 3. |
- Fu, Qilin, 1986-, et al.
(författare)
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Suppressing tool chatter with novel multi-layered nanostructures of carbon based composite coatings
- 2015
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136 .- 1873-4774. ; 223, s. 292-298
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Tidskriftsartikel (refereegranskat)abstract
- Multi-layered nanostructured Cu and Cu-CNx composites synthesized by plasma-enhanced chemical vapour deposition were applied in the clamping area of a milling tool to suppress regenerative tool chatter. Scanning electron microscopy analysis showed a multi-layered nanostructure with excellent conformality, i.e. coating is not only uniform on planar surfaces but also around corners of the substrate. Cu:CuCNx nanostructured multilayers with thicknesses of approximately 0.5:1.6 mu m were obtained. With a diameter of 20 mm, the milling tool performed slotting processes at an overhang length of 120 mm. Modal analysis showed that a coating, with a thickness of approximately 300 mu m, can add sufficient damping without losing stiffness of the tool, to increase the critical stability limit by 50% or 100% depending on cutting direction.
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| 4. |
- rashid, Md.Masud-Ur, et al.
(författare)
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Manufacturing and Characterization of a Carbon-Based Amorphous (a-CNX) Coating Material
- 2018
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Ingår i: Nanomanufacturing and Metrology. - Singapore : Springer. - 2520-8128 .- 2520-811X. ; 1:1, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- A thick 400-micron amorphous carbon nitride (a-CNX ) coating material was synthesized by means of plasma-enhanced chemical vapor deposition process. High-power impulse magnetron sputtering technique was used to sputter a pure graphite target plate in reactive argon (Ar), nitrogen (N2 ) and acetylene (C2 H2 ) environment for depositing the omposite coating. Structural and chemical/elemental composition of the a-CNX composite material was investigated by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and micro-Raman spectroscopy. The rootmean-square surface roughness (Sq ) and structure were estimated by atomic force microscopy. Mechanical properties such as hardness and Young’s modulus (Oliver–Pharr method) at room temperature were characterized by Vickers microindentation test. Operational temperature test of the deposited a-CNX coating reveals that it can withstand up to 400 C without cracking. An inverted shaker test, based on central impedance method, was adopted to investigate the dynamic damping property of the coating material, and it was found that the first bending mode damping lossfactor of the reported a-CNX coating is 0.015 ± 0.001 and corresponding loss modulus (Young’s modulus multiplied by lossfactor) is 0.234 ± 0.011 GPa.
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| 5. |
- Shariful Islam, Md, et al.
(författare)
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Cigarette smoking and associated factors among men in five South Asian countries: A pooled analysis of nationally representative surveys
- 2022
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Ingår i: PLOS ONE. - : PLoS. - 1932-6203. ; 17:11
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Tidskriftsartikel (refereegranskat)abstract
- Smoking is one of the leading causes of premature deaths worldwide. The cigarette is the commonest form of tobacco smoking. This study investigated the factors associated with cigarette smoking among men in five South Asian countries. We analyzed nationally representative cross-sectional study (Demographic and Health Survey) data conducted in Afghanistan, India, Maldives, Nepal, and Pakistan from 2015–2018. Our study population was men aged between 15 and 49 years. The outcome variable was the prevalence of cigarette smoking. We performed both pooled and country-specific analyses using multivariable logistic regression. The prevalence of cigarette smoking among men is the highest (41.2%) in the Maldives and the lowest (20.1%) in Pakistan. Our pooled analysis found that higher age, lower education, lower wealth status, and involvement in any occupations were strongly associated with cigarette smoking (p-value <0.001). However, we did not find a significant association between age and wealth status in Afghanistan, occupations in Nepal and Pakistan, and education in Pakistan with cigarette smoking when country-specific analyses were performed. In this study, socioeconomic position, age, and urban area are strongly associated with cigarette smoking in South Asian countries. The country-specific circumstances should be considered in planning and designing national smoking control strategies and interventions. However, improving access to smoking cessation services could be an effective intervention for all studied countries, Afghanistan, India, Maldives, Nepal, and Pakistan.
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