| 11. |
- Fu, Qilin, 1986-
(författare)
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High dynamic stiffness nano-structured composites for vibration control : A Study of applications in joint interfaces and machining systems
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vibration control requires high dynamic stiffness in mechanical structures for a reliable performance under extreme conditions. Dynamic stiffness composes the parameters of stiffness (K) and damping (η) that are usually in a trade-off relationship. This thesis study aims to break the trade-off relationship.After identifying the underlying mechanism of damping in composite materials and joint interfaces, this thesis studies the deposition technique and physical characteristics of nano-structured HDS (high dynamic stiffness) composite thick-layer coatings. The HDS composite were created by enlarging the internal grain boundary surface area through reduced grain size in nano scale (≤ 40 nm). The deposition process utilizes a PECVD (Plasma Enhanced Chemical Vapour Deposition) method combined with the HiPIMS (High Power Impulse Magnetron Sputtering) technology. The HDS composite exhibited significantly higher surface hardness and higher elastic modulus compared to Poly(methyl methacrylate) (PMMA), yet similar damping property. The HDS composites successfully realized vibration control of cutting tools while applied in their clamping interfaces.Compression preload at essential joint interfaces was found to play a major role in stability of cutting processes and a method was provided for characterizing joint interface properties directly on assembled structures. The detailed analysis of a build-up structure showed that the vibrational mode energy is shifted by varying the joint interface’s compression preload. In a build-up structure, the location shift of vibration mode’s strain energy affects the dynamic responses together with the stiffness and damping properties of joint interfaces.The thesis demonstrates that it is possible to achieve high stiffness and high damping simultaneously in materials and structures. Analysis of the vibrational strain energy distribution was found essential for the success of vibration control.
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| 12. |
- 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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| 13. |
- Kayal, Bassam, et al.
(författare)
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An economic index for measuring firm's circularity : The case of water industry
- 2019
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Ingår i: Journal of Behavioral and Experimental Finance. - : Elsevier. - 2214-6350 .- 2214-6369. ; 21, s. 123-129
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Tidskriftsartikel (refereegranskat)abstract
- Transition toward circular-economy model is a must to sustain the planet sources. Under circular economy model wastewater is transformed from a ste into a resource. Therefore, a comprehensive circular economy dex; the Circonomics Index, is proposed to measure circularity of stewater industry. The component indicators of the index are linked rectly to the three Rs; reduce, reuse and recycle, of circular onomy. The novelty of the proposed Index is that it uses objectively nstructed weights that reflect the environmental benefits of the eatment process, and the index captures the reuse and recycling ficiency of an WWTP, which reflect the specific nature of wastewater. e findings show that treatment technology is a major factor in termining the production efficiency, reuse rate and recycling rformance of a WWTP. The results of using the Circonomics Index have ofound implication for policy makers to speed up the process of moving a circular economy.
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| 14. |
- Nicolescu, Mihai, et al.
(författare)
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New Paradigm in Control of Machining System’s Dynamics
- 2015
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Ingår i: Journal of Machine Engineering. - 1895-7595. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- The increasing demands for precision and efficiency in machining call for effective control strategies based on the identification of static and dynamic characteristics under operational conditions. The capability of a machining system is significantly determined by its static and dynamic stiffness. The aim of this paper is to introduce novel concepts and methods regarding identification and control of a machining system’s dynamics. After discussing the limitations in current methods and technologies of machining systems’ identification and control, the paper introduces a new paradigm for controlling the machining system dynamics based on design of controllable structural Joint Interface Modules, JIMs, whose interface characteristics can be tuned using embedded actuators. Results from the laboratory and industrial implementation demonstrate the effectiveness of the control strategy with a high degree of repeatability.
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| 15. |
- Pervaiz, Salman, et al.
(författare)
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A novel numerical modeling approach to determine the temperature distribution in the cutting tool using conjugate heat transfer (CHT) analysis
- 2015
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer. - 0268-3768 .- 1433-3015. ; 80:5, s. 1039-1047
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Tidskriftsartikel (refereegranskat)abstract
- This study deals with the conjugate heat transfer problem of a single point cutting tool under turning operation dissipating heat in the tool material and streams of the surrounding air. In order to estimate the cutting temperature during the turning operation, the DEFORM-3D finite element package was utilized. A machining simulation material model for Ti6Al4V was utilized using a modified Johnson–Cook equation. The maximum cutting temperature value was obtained from the finite element model. The temperature was then used as a constant heat source on the tool tip, and the conjugate heat transfer (CHT) approach was used to develop a computational fluid dynamics (CFD) model. The CFD model utilized a 3D heat and fluid flow analysis using ANSYS ® CFX. A cutting insert with a constant heat source was exposed to the stream velocities of the dry air. The numerical equations governing the flow and thermal fields in the fluid domain and energy equation in the solid domain were solved in parallel by maintaining the continuity of temperature and heat flux at the solid–fluid interface. The presented conjugate heat transfer (CHT) approach provided a very useful understanding of the temperature profile development at the cutting tool that is still a complex challenge for the existing experimental and numerical techniques.
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| 16. |
- Pervaiz, Salman, et al.
(författare)
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A numerical and experimental study to investigate convective heat transfer and associated cutting temperature distribution in single point turning
- 2018
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : SPRINGER LONDON LTD. - 0268-3768 .- 1433-3015. ; 94:1-4, s. 897-910
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Tidskriftsartikel (refereegranskat)abstract
- During the metal cutting operation, heat generation at the cutting interface and the resulting heat distribution among tool, chip, workpiece, and cutting environment has a significant impact on the overall cutting process. Tool life, rate of tool wear, and dimensional accuracy of the machined surface are linked with the heat transfer. In order to develop a precise numerical model for machining, convective heat transfer coefficient is required to simulate the effect of a coolant. Previous literature provides a large operating range of values for the convective heat transfer coefficients, with no clear indication about the selection criterion. In this study, a coupling procedure based on finite element (FE) analysis and computational fluid dynamics (CFD) has been suggested to obtain the optimum value of the convective heat transfer coefficient. In this novel methodology, first the cutting temperature was attained from the FE-based simulation using a logical arbitrary value of convective heat transfer coefficient. The FE-based temperature result was taken as a heat source point on the solid domain of the cutting insert and computational fluid dynamics modeling was executed to examine the convective heat transfer coefficient under similar condition of air interaction. The methodology provided encouraging results by reducing error from 22 to 15% between the values of experimental and simulated cutting temperatures. The methodology revealed encouraging potential to investigate convective heat transfer coefficients under different cutting environments. The incorporation of CFD modeling technique in the area of metal cutting will also benefit other peers working in the similar areas of interest.
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| 17. |
- Pervaiz, Salman, et al.
(författare)
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Influence of rake angle on the cutting energy when modeling the machining of Ti6Al4V
- 2015
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Ingår i: 2015 10th International Symposium on Mechatronics and its Applications (ISMA). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781467377973
-
Konferensbidrag (refereegranskat)abstract
- The finite element based machining simulations have been used widely in industry and academia to analyze the machining process. These virtual machining simulations have advantages over the real machining experiments due to the immense potential of saving time and expenses. The simulation techniques are even more popular when machining difficult to cut materials such as titanium alloy (Ti6Al4V). In order to make machining process sustainable in nature, energy consumption during the cutting process should be optimized accordingly. The present study aims to provide an insight towards the relation of cutting energy with respect to the different cutting tool geometries. The study used finite element based simulations to investigate the effect of rake angle on the cutting energy. Based on the cutting energy outcomes different suggestions were made to minimize the cutting energy.
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| 18. |
- Pervaiz, Salman, et al.
(författare)
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Minimal quantity cooling lubrication in turning of Ti6Al4V : Influence on surface roughness, cutting force and tool wear
- 2017
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Ingår i: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture. - : Sage Publications. - 0954-4054 .- 2041-2975. ; 231:9, s. 1542-1558
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Tidskriftsartikel (refereegranskat)abstract
- Titanium alloys generally show low machinability ratings. They are referred as difficult-to-cut materials due to their inherent properties such as low thermal conductivity, high chemical reactivity and high strength at elevated temperatures. Cooling strategies play an important role to improve the machining performance of the cutting process. In order to facilitate the heat dissipation from the cutting zone, generous amount of coolant is used when machining highly reactive metals such as titanium alloys. Generally, cutting coolants are nominated as pollutants due to their non-biodegradable nature. This article presents experimental evaluation of a minimal quantity cooling lubrication system. The study investigates a combination of sub-zero-temperature air and vegetable oil-based mist as possible environmentally benign alternative to conventional cooling methods. The results are compared with the dry and flood cutting environments as well. Machinability was evaluated experimentally by considering the surface finish, cutting forces, tool life and their associated tool wear mechanisms. It was concluded from the results obtained from the surface roughness, cutting force and tool life investigation that minimal quantity cooling lubrication (internal) cooling strategy has encouraging potential to replace the conventional flood cooling method.
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| 19. |
- Pervaiz, Salman
(författare)
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Numerical and Experimental Investigations of the Machinability of Ti6AI4V : Energy Efficiency and Sustainable Cooling/ Lubrication Strategies
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Titanium alloys are widely utilized in the aerospace, biomedical,marine, petro-chemical and other demanding industries due to theirdurability, high fatigue resistance and ability to sustain elevateoperating temperature. As titanium alloys are difficult to machine, dueto which machining of these alloys ends up with higher environmentalburden. The industry is now embracing the sustainable philosophy inorder to reduce their carbon footprint. This means that the bestsustainable practices have to be used in machining of titanium alloys aswell as in an effort to reduce the carbon footprint and greenhouse gas(GHG) emissions.In this thesis, a better understanding towards the feasibility of shiftingfrom conventional (dry and flood) cooling techniques to the vegetableoil based minimum quantity cooling lubrication (MQCL) wasestablished. Machining performance of MQCL cooling strategies wasencouraging as in most cases the tool life was found close to floodstrategy or sometimes even better. The study revealed that theinfluence of the MQCL (Internal) application method on overallmachining performance was more evident at higher cutting speeds. Inaddition to the experimental machinability investigations, FiniteElement Modeling (FEM) and Computational Fluid Dynamic (CFD)Modeling was also employed to prediction of energy consumed inmachining and cutting temperature distribution on the cutting tool. Allnumerical results were found in close agreement to the experimentaldata. The contribution of the thesis should be of interest to those whowork in the areas of sustainable machining.
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| 20. |
- Pervaiz, Salman, et al.
(författare)
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Prediction of energy consumption and environmental implications for turning operation using finite element analysis
- 2015
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Ingår i: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture. - : Sage Publications. - 0954-4054 .- 2041-2975. ; 229:11
-
Tidskriftsartikel (refereegranskat)abstract
- This article is concerned with the experimental and numerical investigation of energy consumption involved in the turning of Ti6Al4V titanium alloys. Energy consumption of a machining process is considered as an important machining performance indicator. This article aims to propose an approach for the prediction of energy consumption and related environmental implications using finite element modeling simulations. Machining experiments were conducted using uncoated carbide tools under dry cutting environment. DEFORM-3D software package was utilized to simulate finite element–based machining simulations. Experimental validation was mainly conducted by focusing on the cutting forces and power consumption measurements. Simulated results of the cutting force and power consumption were found in a good agreement with the experimental findings. The amount of CO2 emission resulting from energy consumption during the machining phase is highly dependent on the geographical location. This study also incorporated the energy mix of United Arab Emirates for the environmental calculations. Finally, in the light of proposed methodology, possible future directions and recommendations have also been presented.
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