| 1. |
- Bonilla Hernández, Ana Esther
(författare)
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Analysis and direct optimization of cutting tool utilization in CAM
- 2015
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The search for increased productivity and cost reduction in machining can be interpreted as the desire to increase the material removal rate, MRR, and maximize the cutting tool utilization. The CNC process is complex and involves numerous limitations and parameters, ranging from tolerances to machinability. A well-managed preparation process creates the foundations for achieving a reduction in manufacturing errors and machining time. Along the preparation process of the NC-program, two different studies have been conducted and are presented in this thesis. One study examined the CAM programming preparation process from the Lean perspective. The other study includes an evaluation of how the cutting tools are used in terms of MRR and tool utilization.The material removal rate is defined as the product of three variables, namely the cutting speed, the feed and the depth of cut, which all constitute the cutting data. Tool life is the amount of time that a cutting tool can be used and is mainly dependent on the same variables. Two different combinations of cutting data might provide the same MRR, however the tool life will be different. Thereby the difficulty is to select the cutting data to maximize both MRR and cutting tool utilization. A model for the analysis and efficient selection of cutting data for maximal MRR and maximal tool utilization has been developed and is presented. The presented model shortens the time dedicated to the optimized cutting data selection and the needed iterations along the program development.
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| 2. |
- Bushlya, Volodymyr, et al.
(författare)
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On the Analytical Representation of Chip Area and Tool Geometry when Oblique Turning with Round Tools. Part 1: Chip Area Parameters under Variation of Side and Back Rake Angle
- 2015
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Ingår i: 15th CIRP Conference on Modelling of Machining Operations (15TH CMMO). - : Elsevier BV. - 2212-8271. ; 31, s. 417-422
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Konferensbidrag (refereegranskat)abstract
- Chip area parameters, such as undeformed chip thickness, equivalent chip thickness, contact edge length, etc., along with tool angles are among defining for the mechanical and thermal conditions of the cutting process. This paper considers the case of external turning with a round insert under variation, in wide range, of back and side rake angles and their influence on the main chip area and surface roughness parameters. Influence of other process variables, such as feed, depth-of-cut and nose radius, is also studied. The developed analytical models and algorithms allow, not only to study the fundamental relationships, but to apply them in the design of new tools for conventional and rotary turning.
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| 3. |
- Bushlya, Volodymyr, et al.
(författare)
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On the Analytical Representation of Chip Area and Tool Geometry when Oblique Turning with Round Tools. Part 2: Variation of Tool Geometry along the Edge Line
- 2015
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Ingår i: 15th CIRP Conference on Modelling of Machining Operations (15TH CMMO). - : Elsevier BV. - 2212-8271. ; 31, s. 423-428
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Konferensbidrag (refereegranskat)abstract
- This paper presents the models, analytical equations and results of analysis for determination of major cutting edge, orthogonal and normal clearance and rake angles, and cutting edge inclination angle. The analysis is carried for variable side and back rake angles used by the tool manufacturers and a corresponding variation of the geometry along the edge line for the case of round tools. The influence of tool nose radius, chamfer/chipbreaker angle and depth-of-cut was considered as well. Significant variation in orthogonal geometry from that stated in catalogues was found in most cases. The developed analytical solutions and algorithms allow the establishment of fundamental geometrical relationships and giving a correct prediction when developing new tools for conventional and rotary turning. (C) 2015 The Authors. Published by Elsevier B.V.
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| 4. |
- Chen, Ling, et al.
(författare)
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Analysis of In Situ Mechanical Properties of Phases in High-Alloyed White Iron Measured by Grid Nanoindentation
- 2015
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Ingår i: Journal of Materials Engineering and Performance. - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 24:10, s. 4022-4031
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Tidskriftsartikel (refereegranskat)abstract
- The paper presents an analysis of the in situ mechanical properties (e.g., hardness, elastic modulus, and volume fraction) of phases in high-alloy white iron measured by grid nanoindentation statistically, to reveal the contributions of individual phase properties to the global properties of the material. The in situ mechanical properties of phases measured by grid indentation were validated through targeted indentation. Gaussian and Weibull mixture models were used in analyzing the grid nanoindentation measurements to assess the goodness-of-fit of the indentation data. The nanohardness and indentation modulus measured by grid nanoindentation were directly correlated to the microstructural characteristics of the sample materials. The statistical analysis results were also compared with the mechanical properties and volume fractions obtained using targeted indentation and quantitative metallography based on microstructure analysis to validate the statistical results. The influences of heat treatment on the microstructure, hardness, and elastic modulus of individual phases in the material are also discussed.
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| 5. |
- Chen, Ling, et al.
(författare)
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Assessment on abrasiveness of high chromium cast iron material on the wear performance of PCBN cutting tools in dry machining
- 2018
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Ingår i: Journal of Materials Processing Technology. - : Elsevier BV. - 0924-0136. ; 255, s. 110-120
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Tidskriftsartikel (refereegranskat)abstract
- Polycrystalline Cubic Boron Nitride (PCBN) has been considered as the main cutting tool material for hard turning, which has the comparable surface finish quality as grinding, and high efficiency, economical technology in production. It is well known that the abrasiveness of the workpiece have the very important role of the machinability of the materials. Therefore, the tool wear of the PCBN insert correlates with abrasiveness of the materials very much. In the presented paper, the influence of the micro hardness distribution is used to explain the wear mechanism in machining of the high abrasive materials and proposed a model to predict the abrasiveness. The work material is high chromium cast iron and cutting tool material is PCBN. Abrasiveness are evaluated from the micro hardness distribution by nanoindentation for the distinguish microstructure with hardness. The mapping image of the micro hardness showed the matched features with microstructure images from the scanning electron microscope (SEM). The different chemical composition groups are presented as three heat treatment conditions in experiments, which are as-cast, annealed and hardened. Based on the hardness distribution, this paper presented a model to evaluate the abrasiveness index of the material. The high performance machining is done on six material. The wear mechanism is abrasion in tool wear dominantly and flank wear showed the linear relationship with abrasiveness index. The abrasive wear on the cutting edge suggests that sliding and chipping are the main wear modes which is caused by the combination effect of carbides and matrix. The four mechanisms of diffusion, chemical, abrasive and micro chipping are happening in the tool wear of hard turning. In the dry machining by PCBN insert, abrasiveness is correlated with abrasive and chipping very much and accelerated the crater wear in machining. Abrasiveness index of the material has ability to predict wear performance in dry machining of HCWCI materials by PCBN inserts. The application of the abrasiveness is a potential parameter of machinability to improve the machining efficiency and reduce the cost of machining.
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| 6. |
- Chen, Ling, et al.
(författare)
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Characterization of Microstructure and Mechanical Properties of High Chromium Cast Irons Using SEM and Nanoindentation
- 2015
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Ingår i: Journal of Materials Engineering and Performance. - : Springer Science and Business Media LLC. - 1059-9495 .- 1544-1024. ; 24:1, s. 98-105
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Tidskriftsartikel (refereegranskat)abstract
- The effects of composition changes and heat treatment on the microstructure and mechanical properties of high-chromium white cast irons were studied in order to characterize possible improvements in product performance and machinability. Materials characterization was performed using nanoindentation, SEM, and EDS techniques. Present results show that changes in carbon and silicon contents as well as heat treatment strongly affect the mechanical properties and their variation in the material. In the as-cast condition, the sample with relatively lower carbon and silicon contents has an austenite-martensite matrix and is much harder than the sample with relatively higher carbon and silicon contents having more eutectic carbides in a bainite matrix. Annealing leads to softening of the materials relative to the as-cast condition, with the relatively higher carbon-silicon material being marginally harder due to the presence of more eutectic carbides. A similar trend is seen after the hardening treatment, and the presence of primary carbide can restrict the extent of hardening due to the loss of alloying elements from the matrix.
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| 7. |
- Chen, Ling, et al.
(författare)
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Influences of micro mechanical property and microstructure on performance of machining high chromium white cast iron with cBN tools
- 2015
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Ingår i: 15th CIRP Conference on Modelling of Machining Operations (15TH CMMO). - : Elsevier BV. - 2212-8271. ; 31, s. 172-178
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Konferensbidrag (refereegranskat)abstract
- The variation of the micro mechanical properties, such as hardness and modulus, of the material is important potential factor influencing the machinability of the material. The presented paper is to study the influence of variation in micro hardness and microstructure of the materials on machining performance in terms of tool wear and tool life, cutting forces and surface quality. The work material is high chromium white cast iron and material of cutting tool is cBN. The variation of micro hardness were measured and analyzed by grid nano indentation approach. Volume fraction phases of the material were identified through Weibull mixture distribution from result of grid nano indentation. High chromium white cast irons were prepared with two groups of composition, lower carbon silicon and higher carbon silicon, in the state of as-cast and hardened condition. Results from the machining test indicate that the variation of micro hardness of the work materials show significant impacts on cutting tool wear, tool life, cutting forces and surface quality in the machining of these materials. The effect of micro mechanical properties needs to be taken into account in the modelling and predicting tool life and surface quality. In addition, the mechanism of interaction between the cBN tool and the high chromium white cast iron under the range of machining parameters was also addressed. Lastly, surface roughness measurements complemented the results and a qualitative relationship between the surface roughness generated during the machining and the materials is also laid out. (C) 2015 The Authors. Published by Elsevier B. V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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| 8. |
- Chen, Ling, et al.
(författare)
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Performance assessment of pCBN and bCBN tools in machining of high-chromium white cast iron
- 2015
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Ingår i: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 79:1-4, s. 635-644
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an experimental evaluation of the performance of cubic boron nitride (CBN) tools in the machining of high-chromium white cast iron. Two types of CBN tool materials were evaluated in the tests, including polycrystalline cubic boron nitride (pCBN) and binder-less crystalline cubic boron nitride (bCBN). Performance in terms of the levels of cutting forces, tool wear, surface roughness and process stability was evaluated during and after cutting tests. The work materials used in the cutting tests included two groups with chemical compositions of two levels of carbon silicon (lower C-Si and higher C-Si) in as-cast and hardened states, respectively. Test results indicate that the cutting tool materials clearly exhibited different behaviour in the machining of high-chromium white cast iron. The pCBN tools demonstrated lower tool wear rates than the bCBN tools but had higher roughness levels on the workpiece surfaces. The cutting tools also behaved differently according to the different levels of C-Si content and heat treatment of the work materials. In addition, the study reveals the mechanism of the interactions between CBN tools and high-chromium white cast iron under a range of machining parameters.
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| 9. |
- CHEN, LING, et al.
(författare)
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Quantitative study of roughness effect in nanoindentation on AISI316L based on simulation and experiment
- 2017
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Ingår i: Proceedings of the Institution of Mechanical Engineers. Part C: Journal of Mechanical Engineering Science. - : SAGE Publications. - 0954-4062 .- 2041-2983. ; 231:21, s. 4067-4075
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Tidskriftsartikel (refereegranskat)abstract
- In nanoindentation, roughness of the sample surface can be a severe source of error in the determination of properties from indentation tests. Recently, roughness was also considered as a crucial issue in understanding the indentation size effect where a significant increase in hardness was seen with the decrease of depth. A three-dimensional roughness model with the Johnson–Cook material model is employed to study the roughness effect in nanoindentation on AISI316L stainless steel by use of finite element method. The rough surface is obtained by generating a random function in Matlab and then applying fast Fourier transform. With the quantitative analysis the mechanical properties such as the hardening and variation of the reduced modulus are found. From both the experimental and simulation results, the hardness distribution shows strengthening effect with the increased surface roughness. Both the scatter of hardness and indentation modulus increases with the increased roughness. In addition, the dependence of the pile-up effect and the contact area on the roughness is studied and analyzed.
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| 10. |
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