| 1. |
- Abdullah Asif, Farazee Mohammad, et al.
(författare)
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System dynamics models for decision making in product multiple lifecycles
- 2015
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Ingår i: Resources, Conservation and Recycling. - : Elsevier BV. - 0921-3449 .- 1879-0658. ; 101, s. 20-33
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Tidskriftsartikel (refereegranskat)abstract
- The main drivers for adopting product multiple lifecycles are to gain ecological and economic advantages. However, in most of the cases it is not straight forward to estimate the potential ecological and economic gain that may result from adopting product multiple lifecycles. Even though many researchers have concluded that product multiple lifecycles result in gain, there are examples which indicate that the gain is often marginal or even none in many cases. The purpose of this research is to develop system dynamics models that can assist decision makers in assessing and analysing the potential gain of product multiple lifecycles considering the dynamics of material scarcity. The foundation of the research presented in this paper is laid based on literature review. System dynamics principles have been used for modelling and simulations have been done on Stella iThink platform. The data used in the models have been extracted from different reports published by World Steel Association and U.S. Geological Survey. Some of the data have been assumed based on expert estimation. The data on iron ore reserves, iron and steel productions and consumptions have been used in the models. This research presents the first system dynamics model for decision making in product multiple lifecycles which takes into consideration the dynamics of material scarcity. Physical unavailability and price of material are the two main factors that would drive product multiple lifecycles approach and more sustainable decisions can be made if it is done by taking holistic system approach over longer time horizon. For an enterprise it is perhaps not attractive to conserve a particular type of material through product multiple lifecycles approach which is naturally abundant but extremely important if the material becomes critical. An enterprise could through engineering, proper business model and marketing may increase the share of multiple lifecycle products which eventually would help the enterprise to reduce its dependency on critical materials.
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| 2. |
- Adane, Tigist Fetene, et al.
(författare)
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Application of system dynamics for analysis of performance of manufacturing systems
- 2019
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Ingår i: Journal of manufacturing systems. - : Elsevier BV. - 0278-6125 .- 1878-6642. ; 53, s. 212-233
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Forskningsöversikt (refereegranskat)abstract
- Machining of parts by using dedicated production systems has been, and continues to be, a viable manufacturing method. There are situations, however, where this type of system is not feasible due to changes in product type, customer demand, work-piece material, or design specification. From a competitive manufacturing environment, production system selection is a crucial issue for all component manufacturing companies. Improper selections could negatively affect the overall performance of a manufacturing system, for instance the productivity, as well as the cost and quality of manufactured components. In this paper, the application of system dynamics modelling and simulation of a complex manufacturing process is presented as a potential tool to investigate and analyse the performance of manufacturing system in response to disturbances in the system's inputs (e.g., volume of products). In order to investigate the model soundness, a case study applied to the manufacturing of an engine block will be examined. The model presented here has been developed based on current engine block production for the vehicle manufacturing industry. Such a model can assist manufacturing system selection-centered round the capacity to control machining system parameters -as a testable way to choose a machining strategy from pre-selected performance criteria. More specifically, the benefit of this research lies in the fact that it will enable companies to implement improved potential manufacturing system optimization that responds during unexpected demand fluctuations. In addition, it will help in understanding the complex interaction between the process and operational parameters of a manufacturing system and help identify those critical parameters, ones that can lead to an optimizing strategy in the manufacturing standards of engine block production.
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| 3. |
- Adane, Tigist Fetene
(författare)
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Manufacturing Dynamics and Performance Evaluation
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Manufacturing companies are striving to remain competitive in the market and maintain their economic growth and productivity. Uncertainties regarding the changes in product demand, workpiece material, product design, and technological advancement, have imposed pressure on manufacturing systems. Market uncertainties force manufacturing companies to be flexible and responsive in producing different parts, by adapting the existing system without the need for a substantial investment. The market is characterized by time variations in product quantities and varieties while manufacturing systems remain inherently fixed. To sustain competitive manufacturing, a company has to adopt to new production requirements and be responsive to market changes quickly. Conscious decisions have to be made for a system to respond to market fluctuations. In order to respond to the dynamic changes, there is a need for developing methodologies that analyse, evaluate and control performance of manufacturing system at the system and/or process levels.The primary focus of the thesis is to develop a novel generic framework for modelling and controlling manufacturing systems intending for improvement of the performance of manufacturing and make companies more competitive. The framework incorporates the complex interrelations between the process and system parameters, i.e., the dynamics of the system. Thus, provides a quantitative and qualitative analysis for performance evaluation and for optimizing performance of manufacturing system. The generic framework can further be adapted for studying specific manufacturing systems in discrete manufacturing. Three case studies are presented. The case studies are performed in an automotive company where the effect of various levels of control is investigated in manufacturing systems configured as transfer line or as a flexible manufacturing system.Two aspects of the dynamic nature of manufacturing system are investigated in this thesis: (1) The engineering nature of the system, i.e., the selection of appropriate process parameters to manufacture a product according to the design specification, and (2) The business nature of the system, i.e., the selection of system parameters with respect to the way the product is manufactured. At the process level, the parameters are controlled within the process capability limits to adapt to the changes of the system parameters in response to the market dynamics. At the system level, operational parameters are controlled to satisfy performance criteria.A case study for resource use analysis during primary processes has also been investigated and presented. The critical operations and the operations that have the highest energy consumptions and the potential for energy savings have been identified.The methodology developed for analysing the performance of the dynamic manufacturing system is based on a system dynamics modelling approach. Results obtained from different modelling approaches are presented and compared based on the selected performance metrics.
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| 4. |
- Adane, Tigist Fetene, et al.
(författare)
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Performance evaluation of machining strategy for engine-block manufacturing
- 2015
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Ingår i: Performance evaluation of machining strategy for engine-block manufacturing. - 1895-7595 .- 2391-8071. ; 15:4, s. 81-102
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Tidskriftsartikel (refereegranskat)abstract
- This paper will introduce a novel methodology for the performance evaluation of machining strategies of engine block manufacturing. The manufacturing of engine components is vital to the automotive and vehicle manufacturing industries. Machining is critical processes in the production of these parts. To survive and excel in the competitive manufacturing environment, companies need to improve as well as update their machining processes and evaluate the performance of their machining lines. Moreover, the lines and processes have to be robust in handling different sources of variation over time that include such examples as demand fluctuations, work-piece materials or even any changes in design specifications. A system dynamics modelling and simulation approach has been deployed to develop a methodology that captures how machining system parameters from the machining process are interacted with each other, how these connections drive performance and how new targets affect process and machine tool parameters through time. The developed model could provide an insight of how to select the crucial machining system parameters and to identify the effect of those parameters on the output of the system. In response to such an analysis, this paper provides (offers) a framework to examine machining strategies and has presented model that is useful as a decision support system for the evaluation and selection of machining strategies. Here a system dynamics methodology for modelling is applied to the milling operation and the model is based on an actual case study from the engine-block manufacturing industry.
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| 5. |
- Adane, Tigist Fetene, et al.
(författare)
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System dynamics as a decision support system for machine tool selection
- 2016
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Ingår i: Journal of Machine Engineering. - : Editorial Institution of Wrocaw Board of Scientific. - 1895-7595 .- 2391-8071. ; 16:3, s. 102-125
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Tidskriftsartikel (refereegranskat)abstract
- The worldwide competitive economy, the increase in sustainable issue and investment of new production line is demanding companies to choose the right machine from the available ones. An improper selection can negatively affect the overall performance of the manufacturing system like productivity, quality, cost and company’s responsive manufacturing capabilities. Thus, selecting the right machine is desirable and substantial for the company to sustain competitive in the market. The ultimate objective of this paper is to formulate a framework for machining strategy and also provide methodology for selecting machine tool from two special purpose machine tools in consideration of interaction of attributes. A decision support system for the selection of machine tool is developed. It evaluates the performance of the machining process and enhances the manufacturer (decision maker) to select the machine with respect to the performance and the pre-chosen criteria. Case study was conducted in a manufacturing company. A system dynamics modelling and simulation techniques is demonstrated towards efficient selection of machine tool that satisfy the future requirement of engine-block production.
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| 6. |
- Adane, Tigist Fetene, et al.
(författare)
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Towards a Generic Framework for the Performance Evaluation of Manufacturing Strategy : An Innovative Approach
- 2018
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Ingår i: JOURNAL OF MANUFACTURING AND MATERIALS PROCESSING. - : MDPI AG. - 2504-4494. ; 2:2
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Tidskriftsartikel (refereegranskat)abstract
- To be competitive in a manufacturing environment by providing optimal performance in terms of cost-effectiveness and swiftness of system changes, there is a need for flexible production systems based on a well-defined strategy. Companies are steadily looking for methodology to evaluate, improve and update the performance of manufacturing systems for processing operations. Implementation of an adequate strategy for these systems' flexibility requires a deep understanding of the intricate interactions between the machining process parameters and the manufacturing system's operational parameters. This paper proposes a framework/generic model for one of the most common metal cutting operations-the boring process of an engine block machining system. A system dynamics modelling approach is presented for modelling the structure of machining system parameters of the boring process, key performance parameters and their intrinsic relationships. The model is based on a case study performed in a company manufacturing engine blocks for heavy vehicles. The approach could allow for performance evaluation of an engine block manufacturing system condition. The presented model enables a basis for other similar processes and industries producing discrete parts.
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| 7. |
- Archenti, Andreas, 1973-, et al.
(författare)
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A top-down equivalent stiffness approach for prediction of deviation sources in machine tool joints
- 2017
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Ingår i: CIRP annals. - : Elsevier. - 0007-8506 .- 1726-0604.
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Tidskriftsartikel (refereegranskat)abstract
- The accuracy of machine tools is affected to a large extent by the behavior of the system's joints. In this paper the equivalent stiffness approach identifies and calculates the contribution of joint error sources to the total deviation measured between toolholder and workpiece under loaded conditions. The force–deviation functions are measured at different locations in the machine workspace. Joint deviations are then computed and compared with results obtained from measurements. The results show the effectiveness of the proposed method in determining joint errors in machines.
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| 8. |
- Archenti, Andreas, 1973-, et al.
(författare)
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Statistical dynamics – analysis of machining systems operational conditions
- 2019. - 1
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Ingår i: Leading-edge research and engineering development whithin advanced chatter vibration theoryY. - Japan : Machine Tool Engineering Foundation. - 9784909859013 ; , s. 118-191
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Bokkapitel (refereegranskat)abstract
- In this chapter the subject of statistical dynamics are discussed and non-parametric and parametric models for machining system identification are derived. The common characteristic for all discussed models is that they may be used for computing the operational dynamic parameters (ODP) of the closed loop machining system. Though the input to these models originates from the machining operations, not all models can be implemented for real-time identification. Generally, non-parametric models may be used solely for off-line identification, i.e., first recording the vibration signal from machining operations and then analysing the signal and identifying the nature of the excitation. Parametric models implemented in recursive algorithms are used for real-time identification of machining systems dynamic characteristics. The main objectives of the chapter are: (i) the development of parametric and non-parametric models based on identification techniques with the purpose of integrating into a single step within the estimation of dynamic parameters characterising the machining system, (ii) in non-parametric identification, implementing techniques for ODPs and random excitation estimation, (iii) in parametric identification, the development of the recursive computational model of the machining system based on the data obtained during the actual operational regime. Through these contributions, a step is taken beyond the classical approach to analyse the dynamics of a machining system by separately identifying the structural and process parameters. In the proposed process, the two substructures, tool/toolholder and workpiece/fixture, are coupled, in addition to the open loop (elastic structure of the machine tool), by a feedback loop closing the energy loop, through the thermoplastic chip formation mechanism.The machining system can only be completely analysed only in closed loop i.e. in operational conditions since specially designed off-line experiments with controlled input, such as modal testing, give the response from only the open loop.
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| 9. |
- Frangoudis, Constantinos, et al.
(författare)
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Development and analysis of a consciously designed Joint Interface Module for improvement of a machining system's dynamic performance
- 2017
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Ingår i: The International Journal of Advanced Manufacturing Technology. - : Springer London. - 0268-3768 .- 1433-3015. ; 88:1-4, s. 507-518
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Tidskriftsartikel (refereegranskat)abstract
- Machining vibrations and dynamic instability of machine tools is an important consideration in machining systems. Common approaches for improving their dynamic performance target either the process, or intelligent, yet complex control systems with actuators. Given that machine tools' dynamic characteristics are largely defined by the characteristics of the joints, this article proposes a novel concept, attempting to create a new paradigm for improving the dynamic behaviour of machine tools-introducing modular machine tools components (Joint Interface Modules-JIMs) with joints deliberately designed for increasing dynamic stiffness and enhancing damping with the use of viscoelastic materials. Through a systematic model-based design process, a prototype replicating a reference tool holder was constructed exploiting viscoelastic materials and the dynamic response of the machining system was improved as a result of its introduction; in machining experiments, the stability limit was increased from around 2 mm depth of cut to 4 mm depth of cut, without compromising the rigidity of the system or changing the process parameters. The article also includes the results of investigations regarding the introduction of such prototypes in a machine tool and discusses the shortcomings of the stability lobe diagrams as a method for evaluating the performance of machine tool components with viscoelastically treated joints.
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| 10. |
- 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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