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| 2. |
- Cedergren, Stefan, 1982
(författare)
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Influence of Material Variations on Machinability - Machining Difficult-to-Machine Alloys
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this study is to investigate the effect of work material variations on machinability. Improved knowledge in this respect supports the development of sustainable production both from resource and economical points of view.The properties of work materials vary greatly depending on how they were manufactured. Castings generally have coarse microstructure compared to wrought material, where the added thermo-mechanical processing steps in the latter produce finer microstructure. Local within-part variations in microstructure are found in both castings and wrought material. In cast material this varies due to factors such as undercooling and cooling rate. In wrought material local variations in process parameters, such as deformation and temperature produce different microstructures.Within-process variations during machining also exist, where surfaces deformed during cutting are left to subsequent cuts. The same occurs when machining sheet metal, where degree of deformation also may vary due to local variations in strain. In this work differences in both microstructure and deformation has been investigated for three work materials; nickel-iron based Alloy 718, titanium alloy Ti-6Al-4V and the stainless steel 316L. It was found that coarse microstructures result in anisotropic chip formation, where chips had a non-periodic serrated appearance in both Alloy 718 and Ti-6Al-4V. Both alloys are known to produce continuous chips at low feed rates and cutting speeds, with a transition to serrated chips as these parameters are increased, due to instability in the cutting process. The serrations due to this instability show a more periodic appearance, clearly distinguishable to the serrations due to anisotropy.In Alloy 718 coarse microstructure was also found to produce large burrs, that were continuously built-up during machining, as well as increase notch wear at the depth-of-cut on the cutting tool. In Ti-6Al-4V the anisotropic chip formation behavior found in coarse microstructure was connected to orientations of alpha colonies, i.e. where some orientations produce highly localized deformation and others were homogeneously deformed at all feed rates and speeds investigated. Chip breakability was found to increase with size of alpha colonies, aided by the colonies that had highly localized deformation. The influence of the less periodic serrations found in coarse microstructure was also found to produce vibrations over a wider cutting speed range compared to the periodic serrations in finer microstructures.In both Alloy 718 and stainless steel 316L cutting forces were reduced when the work material had been deformed prior to machining, compared to annealed material.
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| 3. |
- Cedergren, Stefan, 1982, et al.
(författare)
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Influence of work material microstructure on vibrations when machining cast Ti-6Al-4V
- 2016
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Ingår i: The International Journal of Advanced Manufacturing Technology. - London : Springer. - 0268-3768 .- 1433-3015. ; 84:9-12, s. 2277-2291
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Tidskriftsartikel (refereegranskat)abstract
- Titanium alloys are known to produce shear-localized chips during machining, resulting in cyclic variations in cutting forces which in turn could cause severe problems with vibrations. However, at low cutting speeds and feed rates, continuous chips are formed, with an increase in both parameters favoring the transition to shear-localized chips. This transition is affected by work material microstructure, where a coarse microstructure gives anisotropic effects, e.g., when the size of alpha colonies is on the same order of magnitude as the primary cutting zone. The change in chip morphology with an increase in cutting parameters will then be dependent on the orientation of alpha colonies within the cutting zone. The microstructure of work material can show large variations depending on product form, e.g., cast, wrought, or sheet material, thus affecting whether the chip formation is isotropic or anisotropic. Other sources of variations also exist that can be found within the same component, such as segregation of alloying elements and differences in thermo-mechanical history during processing due to geometry. In this study, the interaction between work material microstructure, process parameters, and the machining system’s structural characteristics is studied. The aim is to further increase the knowledge about vibrations during machining of titanium and the role of microstructure and machining system properties. Different microstructures were produced by adding boron to cast Ti-6Al-4V material, where the resulting colony sizes gave both isotropic and anisotropic chip formation within the chosen cutting data range. The machining systems dynamic properties were varied by using different tool overhangs, thereby simulating different configurations of natural frequencies and stiffness. The results show the influence of both microstructure and machining system’s structural characteristics on the dynamic response of the system for different process parameters. This information can be used to increase robustness of machining operations taking into consideration this three-way relationship.
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| 4. |
- Eynian, Mahdi, 1980-, et al.
(författare)
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New methods for in-process identification of modal parameters in milling
- 2018
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Ingår i: Procedia CIRP. - : Elsevier. - 2212-8271 .- 2212-8271. ; 77, s. 469-472
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Tidskriftsartikel (refereegranskat)abstract
- Chatter vibrations encountered in machining can degrade surface finish and damage the machining hardware. Since chatter originates from unstable interaction of the machining process and the machining structure, information about vibration parameters of the machining structure should be used to predict combinations of cutting parameters that allow stable machining. While modal test methods, for example those with impact hammers, are widely used to identify structural parameters; the need for sophisticated test equipment is prohibitive in their use. Furthermore, dynamic properties of critical components of a machine tool may change as they get affected by cutting loads, material removal and spindle rotation. Recently few algorithms have been proposed that identify the in-process dynamic parameters by frequency measurements, thus avoiding these problems. In this paper, some of these algorithms are reviewed and their capabilities and limitations in processing am experimental data set are compared and discussed. © 2018 The Authors. Published by Elsevier Ltd.
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| 5. |
- Fotedar, Sunney, 1989, et al.
(författare)
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Mathematical optimization of the tactical allocation of machining resources for an efficient capacity utilization in aerospace component manufacturing
- 2019
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Ingår i: Proceedings of the 10th Aerospace Technology Congress. - : Linköping University Electronic Press. - 1650-3686 .- 1650-3740. - 9789175190068 ; , s. 183-188
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Konferensbidrag (refereegranskat)abstract
- In the aerospace industry, with low volumes and many products, there is a critical need to efficiently use available manufacturing resources. Currently, at GKN Aerospace, resource allocation decisions that in many cases will last for several years are to some extent made with a short-term focus so as to minimize machining time, which results in a too high load on the most capable machines, and too low load on the less capable ones. This creates an imbalance in capacity utilization that leads to unnecessary queuing at some machines, resulting in long lead times and in an increase in tied-up capital. Tactical resource allocation on the medium to long-range planning horizon (six months to several years) aims to address this issue by allocating resources to meet the predicted future demand as effectively as possible, in order to ensure long range profitability. Our intent is to use mathematical optimization to find the best possible allocations.
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| 6. |
- Hoier, Philipp, 1988, et al.
(författare)
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Microstructural characteristics of Alloy 718 and Waspaloy and their influence on flank wear during turning
- 2018
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Ingår i: Wear. - : Elsevier BV. - 0043-1648. ; 400-401, s. 184-193
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Tidskriftsartikel (refereegranskat)abstract
- The present study deals with the influence of the microstructures of two wrought superalloys on the flank wear of uncoated cemented tungsten carbide tools in turning. Tool life tests have been performed in order to compare the flank wear development during machining of Alloy 718 and Waspaloy. Additionally, microstructural aspects, such as hardness, grain size as well as types and quantities of hard, abrasive phases have been determined and compared for both machined superalloy workpieces. The results show that Alloy 718 is associated with faster flank wear progression as compared with Waspaloy. The difference in wear is not likely to be the result of higher thermal and mechanical loads on the tool during machining Alloy 718. Characterization of obtained flank wear topographies after removal of adhered workpiece material revealed that abrasive wear is the dominant wear mechanism during machining both superalloys with the investigated cutting parameters. Varying extents of abrasive tool wear during cutting of the two alloys are therefore the likely reason for the different wear rates. In connection to that, significantly larger quantities of hard phases, specifically primary MC-type carbides and TiN-inclusions were found in the Alloy 718 workpiece which can explain the faster flank wear progression during machining this alloy.
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| 7. |
- Johansson, Peter E., Associate professor, 1978-, et al.
(författare)
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Let us measure, then what? : Exploring purposeful use of innovation management self-assessments.
- 2019
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Ingår i: International Journal of Quality & Reliability Management. - 0265-671X .- 1758-6682. ; 36:10, s. 1734-1749
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Tidskriftsartikel (refereegranskat)abstract
- PurposeThe purpose of this paper is to increase the understanding regarding how managers attempt to make purposeful use of innovation management self-assessments (IMSA) and performance information (PI).Design/methodology/approachAn interpretative perspective on purposeful use is used as an analytical framework, and the paper is based on empirical material from two research projects exploring the use of IMSA and PI in three case companies. Based on the empirical data, consisting of interviews and observations of workshops and project meetings, qualitative content analysis has been conducted.FindingsThe findings of this paper indicate that how managers achieve a purposeful use of PI is related to their approach toward how to use the specific PI at hand, and two basic approaches are analytically separated: a rule-based approach and a reflective approach. Consequently, whether or not the right thing is being measured also becomes a question of how the PI is actually being interpreted and used. Thus, the extensive focus on what to measure and how to measure it becomes edgeless unless equal attention is given to how managers are able to use the PI to make knowledgeable decisions regarding what actions to take to achieve the desired changes.Practical implicationsGiven the results, it comes with a managerial responsibility to make sure that all managers who are supposed to be engaged in using the PI are given roles in the self-assessments that are aligned with the level of knowledge they possess, or can access.Originality/valueHow managers purposefully use PI is a key to understand the potential impact of self-assessments.
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| 8. |
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| 9. |
- Malakizadi, Amir, 1983, et al.
(författare)
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Inverse identification of flow stress in metal cutting process using Response Surface Methodology
- 2016
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Ingår i: Simulation Modelling Practice and Theory. - : Elsevier BV. - 1569-190X. ; 60, s. 40-53
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a methodology was presented to determine the flow stress behaviour of the work material within the range of strain, strain rate and temperature encountered during chip formation process by means of inverse modelling of orthogonal cutting operations. This approach was based on the concept of Design of Experiments (DOEs) and Response Surface Methodology (RSM). Initially, an extension of Oxley's machining theory incorporating the Johnson-Cook material model was integrated with RSM to accomplish a fast assessment of the material parameters. Having provided the material parameters by Oxley's machining theory, the optimum set of friction coefficients were determined through evaluation of the Finite Element (FE) simulation results. The final step involved direct integration of 2D FE models incorporating the optimum frictional boundary conditions with RSM to reassess the optimum set of material parameters. This approach was implemented to determine the constitutive parameters for wide range of materials including Inconel 718 in aged condition, AISI 1080 plain carbon steel and AA6082-T6 aluminium alloy. The calibration of material models using the presented inverse methodology led to a significant improvement in simulation results. The reasons for the robustness of the proposed inverse methodology were discussed.
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| 10. |
- Parida, Vinit, et al.
(författare)
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A study of how ICT capabilities can influence dynamic capabilities
- 2016
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Ingår i: Journal of Enterprise Information Management. - : Emerald Group Publishing Limited. - 1741-0398 .- 1758-7409. ; 29:2, s. 179-201
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Tidskriftsartikel (refereegranskat)abstract
- Purpose - Prior studies have argued that small firms with dynamic capabilities can revise and reconfigure their internal resources to meet the uncertainties of their business environment. However, there is a lack of understanding of how they can develop such critical capabilities. In this study, we propose that small firms can employ information and communication technology (ICT) capabilities as a facilitator for developing dynamic capabilities. Thus, the study builds on resource-based view (RBV) literature and and information systems (IS) literature by examining the influence of ICT capabilities on the dynamic capabilities of small firms.Design/methodology/approach - Several hypotheses were tested by analyzing the survey data from 291 small high-technology firms in Sweden.Findings - The results reveal that ICT capabilities influence dynamic capabilities of small firms. More specifically, the ICT use for internal efficiency positively influences adoptive capabilities, collaborative use of ICT positively influences networking capabilities, and ICT use for communications positively influences both adaptive and innovation capabilities. Consequently, the results suggest that the different components of ICT capabilities facilitate the development of the different organizational capabilities that together represent dynamic capabilities and thus, can contribute to a small firm’s competitive advantage.Practical implications - This study has few implications for the managers and CEO’s of small high-technology firms. Firstly, by prioritizing ICT capabilities, small firms can benefit from the development of dynamic capabilities that will support them to meet the challenges of turbulent business environment. Secondly, because small firms usually lack internal resources (i.e., financial resources and competence), the study provides more specific direction on how they can strategically invest and build different components of ICT that will positively influence their adaptive, absorptive, innovative and network capabilities.Originality/value – The study provides an alternative view of how ICT capabilities influence the performance of small firms, and outlines how such capabilities influence the development of dynamic capabilities. Therefore, the study in hand contributes to the RBV and IS literature by specifically linking the components of ICT capabilities to dynamic capabilities and its related sub-capabilities.
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| 11. |
- Schaeffer, Jennie, 1974-, et al.
(författare)
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Presencing and Downloading : in Photo-supported Group Discussions on Innovation
- 2017
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Ingår i: XXVIII ISPIM Innovation Conference ISPIM 2017.
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Konferensbidrag (refereegranskat)abstract
- Abstract: The overall research focus in the study is how photographs can be used in workplace innovation processes. This work-in-progress paper discusses photo-supported group discussions on innovation as an approach to incorporate employees in the development of a radically innovative culture. The method involves managers and engineers in a process that transforms their conceptions of innovation into visuals and words, and provides a possibility for collective reflection based on these formulations. Enabling all employees to use their experiences and knowledge in workplace innovation is an opportunity being pursued in Sweden. The paper is a starting point to discuss whether or not the method of photo supported discussion on innovation could be helpful to support a shift to a radically innovative culture. The concepts of downloading or presencing are introduced to analyse the method.
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