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Improved finite element modelingfor chip morphology prediction inmachining of C45E steel
University West, Department of Engineering Science, Research Enviroment Production Technology West. (PTW)ORCID iD: 0000-0003-3877-9067
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Within the manufacturing of metallic components, machining plays an important role and is of vital significance to ensure process reliability. From a cutting tool design perspective, physics-based numerical modeling that can predict chip morphology is highly necessary to design tool macro geometry. The chip morphology describes the chip shape geometry and the chip curl geometry. Improved chip morphology prediction increases process reliability by improved chip breakability and effective chip evacuation.

To this end, in this work, a platform is developed to compare a numerical model'schip morphology prediction with experimental results. The investigated cuttingprocesses are orthogonal cutting process and nose turning process. Numerical models that simulate the chip formation process are used to predict the chip morphology accompanied by machining experiments. Computed tomography isused to scan the chips obtained from machining experiments evaluating its ability to capture the chip morphology variation. For the nose turning process, chip curl parameters need to be calculated during the cutting process. Kharkevich model is utilized in this regard for calculating the 'chip in process' chip curl parameters. High-speed videography is used to measure the chip side-flow angle during thecutting process experiments enabling comparison with physics-based model predictions.

With regards to chip shape predictability, the numerical models that simulate the chip formation process are improved by improving the flow stress models and evaluating advanced damage models. The workpiece material, C45E steel, arecharacterized using Gleeble thermo-mechanical simulator. The obtained flow stress is modeled using phenomenological flow stress models. Existing phenomenological flow stress models are modified to improve their accuracy. The fracture initiation strain component of damage models' influence on the prediction of transition from continuous chip to segmented chip is studied. The flow stress models and the damage models are implemented in the numerical models through FORTRAN subroutines. The prediction of continuous to segmented chip transitions are evaluated for varying rake angles and feed rate ata constant cutting velocity.

The results from the numerical model evaluation platform show that the methodology provides the framework where an advance in numerical models is evaluated reliably from a 'chip morphology prediction capability' viewpoint forthe nose turning process. The numerical modeling results show that the chip curl variation for varying cutting conditions is predicted qualitatively. The flow stress curves obtained through Gleeble thermo-mechanical simulator show dynamic strain aging presence in specific temperature -strain rate ranges. The results of the phenomenological model modification show their ability to incorporate the dynamic strain aging influence. The modified phenomenological model improvesthe accuracy of the numerical models' prediction accuracy. The flow stress models combined with advanced damage model can predict the transition from continuous to segmented chip. Within damage model, the fracture initiation strain component is observed to influence the continuous chip to segmented chip transition and chip segmentation intensity for varying rake angle and feed rate and at a constant cutting velocity.

Abstract [sv]

Populärvetenskaplig Sammanfattning

Bearbetning är en 150-årig tillverkningsprocess som återfinns antingen direkt eller indirekt i nästan allt som tillverkas. I dagsläget med den snabba omställning motmer digitala arbetssätt riskerar allt som inte digitaliseras med stor sannolikhet att bli kvarlämnat. Två aspekter mot digitaliseringen av skärande bearbetningsprocesser har genomförts i detta arbete. Den första var en utvärdering av befintliga metoder och utvecklingen av nya metoder för att digitalisera komplexa spångeometrier som återfinns i bearbetningsprocessen, vilket inte tidigare gjorts. Nästa steg är att fånga fysiken som är involverad i en skärprocess för att kunna simulera denna med högre noggrannhet. I denna del av arbetet har inriktats till att urskilja små förändringar i ingångsförhållandena i dess relation till spånformning.

En spånans ytstruktur kan vara antingen slät eller korrugerad. Att veta vilken spånform som kommer att skapas ger oss förmågan att bättre kontrollera bearbetningsprocessen. I det genomförda arbetet har det skapats förbättrande materialmodeller som möjliggör en ökad noggrannhet vad gäller möjligheten att simulera spånformen vid skärande bearbetning. En stor del av arbetet här harägnats åt en ökad förståelse av ett materials uppträdande, i detta fall stål, vid skärande bearbetning. Detta har skett genom omfattande materialtestning där testresultaten har presenterats i form av matematiska ekvationer i de numeriska modellerna. Övriga metoder som har används för att skapa dessa digitala spånor inkluderar datortomografi, höghastighetsvideografi och matematiska modeller. När dessa kombineras med datorgrafik kan man erhålla numeriska modeller för att simulera skärande bearbetning.

Resultatet av denna förbättring av befintliga numeriska modeller är förmågan att se påverkan av hur små förändringar i skärverktygets geometri kan påverka formen på den av skärprocessen skapade spånan. Sammantaget kan resultatet av den genomförda forskningen bidra till att skapa ett obrutet virtuellt arbetssätt vidproduktutveckling av skärande verktyg.

Place, publisher, year, edition, pages
Trollhättan: University West , 2020. , p. 93
Series
PhD Thesis: University West ; 34
Keywords [en]
Chip curl, Chip flow, Chip segmentation, Computed Tomography, Damage modeling, Flow stress modeling, Machining
Keywords [sv]
Spånkrökning; Spånflöde; Spånsegmentering; Datortomografi; Skademodelleringen; Modellering av Flytspänning; Bearbetning
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
URN: urn:nbn:se:hv:diva-14979ISBN: 978-91-88847-52-2 (print)ISBN: 978-91-88847-51-5 (electronic)OAI: oai:DiVA.org:hv-14979DiVA, id: diva2:1394457
Public defence
2020-02-12, Albertssalen, 10:00 (English)
Opponent
Supervisors
Available from: 2020-02-19 Created: 2020-02-19 Last updated: 2020-02-19Bibliographically approved
List of papers
1. Quantitative Characterization of Chip Morphology Using Computed Tomography in Orthogonal Turning Process
Open this publication in new window or tab >>Quantitative Characterization of Chip Morphology Using Computed Tomography in Orthogonal Turning Process
2015 (English)In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 33, p. 299-304Article in journal (Refereed) Published
Abstract [en]

Abstract The simulation of machining process has been an area of active research for over two decades. To fully incorporate finite element (FE) simulations as a state of art tool design aid, there is a need for higher accuracy methodology. An area of improvement is the prediction of chip shape in FE simulations. Characterization of chip shape is therefore a necessity to validate the FE simulations with experimental investigations. The aim of this paper is to present an investigation where computed tomography (CT) is used for the characterization of the chip shape obtained from 2D orthogonal turning experiments. In this work, the CT method has been used for obtaining the full 3D representation of a machined chip. The CT method is highly advantageous for the complex curled chip shapes besides its ability to capture microscopic features on the chip like lamellae structure and surface roughness. This new methodology aids in the validation of several key parameters representing chip shape. The chip morphology’s 3D representation is obtained with the necessary accuracy which provides the ability to use chip curl as a practical validation tool for FE simulation of chip formation in practical machining operations. The study clearly states the ability of the new CT methodology to be used as a tool for the characterization of chip morphology in chip formation studies and industrial applications.

Keywords
validation, Finite lement method, Computed Tomography
National Category
Manufacturing, Surface and Joining Technology Other Mechanical Engineering
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-7888 (URN)10.1016/j.procir.2015.06.053 (DOI)000360312600051 ()2-s2.0-84939796397 (Scopus ID)
Conference
9th CIRP Conference on Intelligent Computation in Manufacturing Engineering - CIRP ICME ’14, Capri, ITALY, JUL 23-25, 2014
Available from: 2015-08-13 Created: 2015-08-13 Last updated: 2020-02-20Bibliographically approved
2. Modeling of Chip curl in Orthogonal Turning using Spiral Galaxy describing Function
Open this publication in new window or tab >>Modeling of Chip curl in Orthogonal Turning using Spiral Galaxy describing Function
2016 (English)In: Proceedings International Conference on competitive Manufacturing: 27 January - 29 January 2016 Stellenbosch, South Africa organised By The department Of Industrial Engineering Stellenbosch University / [ed] Dimiter Dimitrov & Gert Adriaan Oosthuizen, Global Competitiveness Centre in Engineering Department of Industrial Engineering Stellenbosch University , 2016, p. 33-38Conference paper, Published paper (Refereed)
Abstract [en]

With advances in modeling of machining process, a methodology for quantitative evaluation of the chip curl shape in orthogonal turning process is highly desired. To achieve this, a function to fit the varying chip curl was required. A mathematical function which is used to describe spiral galaxies is employed in this work which is able to accurately model wide variety of chip curl shapes. The function is employed to compare the chip curl predicted by numerical models with experimental investigations and it should be able to capture the variation of chip curl for varying cutting conditions ranging from tightly wound springs to comma shapes and the transition between them. This provides insights into the evaluation of cutting models from a practical view point. Finite element simulations were performed to predict the chip shape for varying tool rake angles and feed rates in orthogonal cutting process. The results show that the mathematical function was capable to model the wide variety of chip curl shapes encountered in orthogonal turning process.The chip curl predicted by the simulations show that numerical simulations need advanced models to depict work piece material behaviour, heat transfer behaviour and friction behaviour to predict the variation in chip curl shapes accurately for an orthogonal turning process.

Place, publisher, year, edition, pages
Global Competitiveness Centre in Engineering Department of Industrial Engineering Stellenbosch University, 2016
Keywords
Chip curl, machining, finite element simulation
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-8668 (URN)978-0-7972-1602-0 (ISBN)
Conference
6th International Conference on Competitive Manufacturing – COMA ‘16”in Stellenbosch, South Africa 2016
Note

Ingår i Licentiatuppsats

Available from: 2015-11-14 Created: 2015-11-14 Last updated: 2020-02-19Bibliographically approved
3. Characterization of Chip Morphology in Oblique Nose Turning employing High Speed Videography and Computed Tomography Technique
Open this publication in new window or tab >>Characterization of Chip Morphology in Oblique Nose Turning employing High Speed Videography and Computed Tomography Technique
2016 (English)In: Proceedings International Conference on competitive Manufacturing: 27 January - 29 January 2016 Stellenbosch, South Africa organised By The department Of Industrial Engineering Stellenbosch University / [ed] Dimiter Dimitrov & Gert Adriaan Oosthuize, Department of Industrial Engineering Stellenbosch University , 2016, p. 249-254Conference paper, Published paper (Refereed)
Abstract [en]

Simulation of industrial cutting processes employing physics based numerical models provide valuable insights into its deformation mechanics. Evaluating such models through chip studies require characterizing complex geometric features like chip shape, and chip curl. In this study, a characterization methodology is developed employing tools like computed tomography (CT) and high speed imaging. The methodology is used to characterize chip curl parameters such as chipside flow angle, chip up curl and chip side curl in oblique nose turning process. To evaluate the methodology, AISI 1045 steel is machined over a range of machining parameters and the chips obtained are characterized. The study shows that the employed methodology can be used to characterize varying chip curl geometries in nose turning process. CT technique is additionally employed when the chips are significantly deformed. The study also shows that the developed characterization methodology could be used to evaluate physics based numerical models.

Place, publisher, year, edition, pages
Department of Industrial Engineering Stellenbosch University, 2016
Keywords
Chip curl, high speed videography, computed tomography
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-8669 (URN)978-0-7972-1602-0 (ISBN)
Conference
International Conference on Competitive manufacturing – COMA ‘16”in Stellenbosch, South Africa 2016
Note

Ingår i licentiatuppsats

Available from: 2015-11-14 Created: 2015-11-14 Last updated: 2020-02-19Bibliographically approved
4. FE Modelling and Characterization of Chip Curl in Nose Turning process
Open this publication in new window or tab >>FE Modelling and Characterization of Chip Curl in Nose Turning process
(English)In: International Journal of Machining and Machinability of Materials, ISSN 1748-572XArticle in journal (Refereed) Submitted
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology
Identifiers
urn:nbn:se:hv:diva-8670 (URN)
Note

Inågr i licentiatuppsats

Available from: 2015-11-14 Created: 2015-11-14 Last updated: 2020-03-16Bibliographically approved
5. Finite Element Modeling and Validation of Chip Segmentation in Machining of AISI 1045 Steel
Open this publication in new window or tab >>Finite Element Modeling and Validation of Chip Segmentation in Machining of AISI 1045 Steel
Show others...
2017 (English)In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 58, p. 499-504Article in journal (Refereed) Published
Abstract [en]

The finite element (FE) method based modeling of chip formation in machining provides the ability to predict output parameters like cutting forces and chip geometry. One of the important characteristics of chip morphology is chip segmentation. Majority of the literature within chip segmentation show cutting speed (vc) and feed rate (f) as the most influencing input parameters. The role of tool rake angle (α) on chip segmentation is limited and hence, the present study is aimed at understanding it. In addition, stress triaxiality’s importance in damage model employed in FE method in capturing the influence of α on chip morphology transformation is also studied. Furthermore, microstructure characterization of chips was carried out using a scanning electron microscope (SEM) to understand the chip formation process for certain cutting conditions. The results show that the tool α influences chip segmentation phenomena and that the incorporation of a stress triaxiality factor in damage models is required to be able to predict the influence of the α. The variation of chip segmentation frequency with f is predicted qualitatively but the accuracy of prediction needs improvement. © 2017 The Authors.

Keywords
Cutting; Forecasting; Machining centers; Scanning electron microscopy; Shear stress, Chip morphologies; Chip segmentation; Cutting conditions; Damage model; Microstructure characterization; Output parameters; Stress triaxiality; Stress triaxiality factor, Finite element method
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-11909 (URN)10.1016/j.procir.2017.03.259 (DOI)000404958500085 ()2-s2.0-85029738278 (Scopus ID)
Conference
16th CIRP Conference on Modelling of Machining Operations (16th CIRP CMMO), 15-16 June 2017, Cluny, FRANCE
Funder
Knowledge Foundation, 20110263, 20140130.
Note

Funders: Sandvik Coromant

Available from: 2017-12-13 Created: 2017-12-13 Last updated: 2020-02-19Bibliographically approved
6. A modified Johnson-Cook model for ferritic-pearlitic steel in dynamic strain aging regime
Open this publication in new window or tab >>A modified Johnson-Cook model for ferritic-pearlitic steel in dynamic strain aging regime
Show others...
2019 (English)In: Metals, ISSN 2075-4701, Vol. 9, no 5, article id 528Article in journal (Refereed) Published
Abstract [en]

In this study, the flow stress behavior of ferritic-pearlitic steel (C45E steel) is investigated through isothermal compression testing at different strain rates (1 s-1, 5 s-1, and 60 s-1) and temperatures ranging from 200 to 700 °C. The stress-strain curves obtained from experimental testing were post-processed to obtain true stress-true plastic strain curves. To fit the experimental data to well-known material models, Johnson-Cook (J-C) model was investigated and found to have a poor fit. Analysis of the flow stress as a function of temperature and strain rate showed that among other deformation mechanisms dynamic strain aging mechanism was active between the temperature range 200 and 400 °C for varying strain rates and J-C model is unable to capture this phenomenon. This lead to the need to modify the J-C model for the material under investigation. Therefore, the original J-C model parameters A, B and n are modified using the polynomial equation to capture its dependence on temperature and strain rate. The results show the ability of the modified J-C model to describe the flow behavior satisfactorily while dynamic strain aging was operative. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

Place, publisher, year, edition, pages
MDPI AG, 2019
Keywords
flow stress; modified Johnson-Cook model; dynamic strain aging
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13989 (URN)10.3390/met9050528 (DOI):000478818700046 ()2-s2.0-85066741813 (Scopus ID)
Funder
Swedish Research Council, 20110263, 20140130
Available from: 2019-06-20 Created: 2019-06-20 Last updated: 2020-02-19Bibliographically approved

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