Change search
Link to record
Permanent link

Direct link
BETA
Svoboda, Ales
Publications (10 of 32) Show all publications
Holmberg, J., Rodriguez Prieto, J. M., Berglund, J., Svoboda, A. & Jonsén, P. (2018). Experimental and PFEM-simulations of residual stresses from turning tests of a cylindrical Ti-6Al-4V shaft. Paper presented at 4th CIRP Conference on Surface Integrity (CSI 2018), Tianjin, China, July 11-13 2018. Procedia CIRP, 71, 144-149
Open this publication in new window or tab >>Experimental and PFEM-simulations of residual stresses from turning tests of a cylindrical Ti-6Al-4V shaft
Show others...
2018 (English)In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 71, p. 144-149Article in journal (Refereed) Published
Abstract [en]

Alloy Ti-6Al-4V is a frequently used material in aero space applications due the high strength and low weight. This material is however often considered as a difficult to machine alloy due to several material properties such as the inherent characteristics of high hot hardness and strength which is causing an increased deformation of the cutting tool during machining. The thermal properties also cause a low thermal diffusion from locally high temperatures in the cutting zone that allows for reaction to the tool material resulting in increased tool wear.

Predicting the behavior of machining of this alloy is therefore essential when selecting machining tools or machining strategies. If the surface integrity is predicted, the influence of different machining parameters could be studied using Particle Finite Element (PFEM)-simulations. In this investigation the influence from cutting speed and feed during turning on the residual stresses has been measured using x-ray diffraction and compared to PFEM-simulations.

The results showed that cutting speed and feed have great impact on the residual stress state. The measured cutting force showed a strong correlation especially to the cutting feed. The microstructure, observed in SEM, showed highly deformed grains at the surface from the impact of the turning operation and the full width half maximum from the XDR measurements distinguish a clear impact from different cutting speed and feed which differed most for the higher feed rate.

The experimental measurements of the residual stresses and the PFEM simulations did however not correlate. The surface stresses as well as the sign of the residuals stresses differed which might be due to the material model used and the assumption of using a Coulomb friction model that might not represent the cutting conditions in the investigated case.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Applied Mechanics Other Materials Engineering
Research subject
Solid Mechanics; Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-69209 (URN)10.1016/j.procir.2018.05.087 (DOI)2-s2.0-85051265926 (Scopus ID)
Conference
4th CIRP Conference on Surface Integrity (CSI 2018), Tianjin, China, July 11-13 2018
Note

Konferensartikel i tidskrift;2018-06-08 (andbra)

Available from: 2018-06-08 Created: 2018-06-08 Last updated: 2018-08-17Bibliographically approved
Dini, H., Svoboda, A., Andersson, N.-E., Ghassemali, E. & Jarfors, A. E. .. (2018). Optimization and validation of a dislocation density based constitutive model for as-cast Mg-9%Al-1%Zn. Materials Science & Engineering: A, 710, 17-26
Open this publication in new window or tab >>Optimization and validation of a dislocation density based constitutive model for as-cast Mg-9%Al-1%Zn
Show others...
2018 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 710, p. 17-26Article in journal (Refereed) Published
Abstract [en]

A dislocation density-based constitutive model, including effects of microstructure scale and temperature, was calibrated to predict flow stress of an as-cast AZ91D (Mg-9%Al-1%Zn) alloy. Tensile stress-strain data, for strain rates from 10-4 up to 10-1 s-1 and temperatures from room temperature up to 190 °C were used for model calibration. The used model accounts for the interaction of various microstructure features with dislocations and thereby on the plastic properties. It was shown that the Secondary Dendrite Arm Spacing (SDAS) size was appropriate as an initial characteristic microstructural scale input to the model. However, as strain increased the influence of subcells size and total dislocation density dominated the flow stress. The calibrated temperature-dependent parameters were validated through a correlation between microstructure and the physics of the deforming alloy. The model was validated by comparison with dislocation density obtained by using Electron Backscattered Diffraction (EBSD) technique.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Other Materials Engineering
Research subject
Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-66390 (URN)10.1016/j.msea.2017.10.081 (DOI)000429888200003 ()2-s2.0-85032297009 (Scopus ID)
Note

Validerad;2017;Nivå 2;2017-11-06 (andbra)

Available from: 2017-11-06 Created: 2017-11-06 Last updated: 2018-04-27Bibliographically approved
Zamani, M., Dini, H., Svoboda, A., Lindgren, L.-E., Seifeddine, S., Andersson, N.-E. & Jarfors, A. E. .. (2017). A dislocation density based constitutive model for as-cast Al-Si alloys: Effect of temperature and microstructure. International Journal of Mechanical Sciences, 121, 164-170
Open this publication in new window or tab >>A dislocation density based constitutive model for as-cast Al-Si alloys: Effect of temperature and microstructure
Show others...
2017 (English)In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 121, p. 164-170Article in journal (Refereed) Published
Abstract [en]

The flow stress of an as-cast Al-Si based alloy was modeled using a dislocation density based model. The developed dislocation density-based constitutive model describes the flow curve of the alloy with various microstructures at quite wide temperature range. Experimental data in the form of stress-strain curves for different strain rates ranging from 10−4 to 10−1 s−1 and temperatures ranging from ambient temperature up to 400 °C were used for model calibration. In order to model precisely the hardening and recovery process at elevated temperature, the interaction between vacancies and dissolved Si was included. The calibrated temperature dependent parameters for different microstructure were correlated to the metallurgical event of the material and validated. For the first time, a dislocation density based model was successfully developed for Al-Si cast alloys. The findings of this work expanded the knowledge on short strain tensile deformation behaviour of these type of alloys at different temperature, which is a critical element for conducting a reliable microstructural FE-simulation.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Other Materials Engineering
Research subject
Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-61341 (URN)10.1016/j.ijmecsci.2017.01.003 (DOI)000395216300015 ()2-s2.0-85008703756 (Scopus ID)
Note

Validerad; 2017; Nivå 2; 2017-01-09 (andbra)

Available from: 2017-01-09 Created: 2017-01-09 Last updated: 2018-09-12Bibliographically approved
Rodriguez, J. M., Jonsén, P. & Svoboda, A. (2017). Dislocation Density Based Material Model Applied in PFEM-simulation of Metal Cutting. Paper presented at 16th CIRP Conference on Modelling of Machining Operations (16th CIRP CMMO), Cluny, France, June 15-16, 2017. Procedia CIRP, 58, 193-197
Open this publication in new window or tab >>Dislocation Density Based Material Model Applied in PFEM-simulation of Metal Cutting
2017 (English)In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 58, p. 193-197Article in journal (Refereed) Published
Abstract [en]

Metal cutting is one of the most common metal-shaping processes. In this process, specified geometrical and surface properties are obtained through the break-up and removal of material by a cutting edge into a chip. The chip formation is associated with large strains, high strain rates and locally high temperatures due to adiabatic heating. These phenomena together with numerical complications make modeling of metal cutting challenging. Material models, which are crucial in metal-cutting simulations, are usually calibrated against data from material testing. Nevertheless, the magnitudes of strains and strain rates involved in metal cutting are several orders of magnitude higher than those generated from conventional material testing. Therefore, a highly desirable feature is a material model that can be extrapolated outside the calibration range. In this study, a physically based plasticity model based on dislocation density and vacancy concentration is used to simulate orthogonal metal cutting of AISI 316L. The material model is implemented into an in-house particle finite-element method software. Numerical simulations are in agreement with experimental results for different cutting speed and feed.

Place, publisher, year, edition, pages
Elsevier, 2017
National Category
Other Materials Engineering Applied Mechanics
Research subject
Solid Mechanics; Engineering Materials
Identifiers
urn:nbn:se:ltu:diva-63646 (URN)10.1016/j.procir.2017.03.338 (DOI)000404958500033 ()2-s2.0-85029766541 (Scopus ID)
Conference
16th CIRP Conference on Modelling of Machining Operations (16th CIRP CMMO), Cluny, France, June 15-16, 2017
Note

2017-06-01 (andbra);Konferensartikel i tidskrift

Available from: 2017-06-01 Created: 2017-06-01 Last updated: 2018-07-10Bibliographically approved
Abiri, O., Wedberg, D., Svoboda, A. & Lindgren, L.-E. (2017). Non-Local Modelling of Strain Softening in Machining Simulations. Paper presented at International Conference on Materials, Alloys and Experimental Mechanics (ICMAEM-2017), Narsimha Reddy Engineering College, India, 3–4 July 2017. IOP Conference Series: Materials Science and Engineering, 225, Article ID 012053.
Open this publication in new window or tab >>Non-Local Modelling of Strain Softening in Machining Simulations
2017 (English)In: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 225, article id 012053Article in journal (Refereed) Published
Abstract [en]

Non-local damage model for strain softening in a machining simulation is presented in this paper. The coupled damage-plasticity model consists of a physically based dislocation density model and a damage model driven by plastic straining in combination with the stress state. The predicted chip serration is highly consistent with the measurement results. 

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2017
Keywords
Finite element simulation; Machining; Non-local models; Damage model; Plasticity
National Category
Applied Mechanics Other Materials Engineering
Research subject
Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-65635 (URN)10.1088/1757-899X/225/1/012053 (DOI)000412003600053 ()
Conference
International Conference on Materials, Alloys and Experimental Mechanics (ICMAEM-2017), Narsimha Reddy Engineering College, India, 3–4 July 2017
Funder
VINNOVA
Note

Konferensartikel i tidskrift

Available from: 2017-09-14 Created: 2017-09-14 Last updated: 2018-11-23Bibliographically approved
Rodriguez Prieto, J. M., Jonsén, P. & Svoboda, A. (2017). Simulation of metal cutting using the particle finite-element method and a physically based plasticity model (ed.). Computational Particle Mechanics, 4(1), 35-51
Open this publication in new window or tab >>Simulation of metal cutting using the particle finite-element method and a physically based plasticity model
2017 (English)In: Computational Particle Mechanics, ISSN 2196-4378, Vol. 4, no 1, p. 35-51Article in journal (Refereed) Published
Abstract [en]

Metal cutting is one of the most common metal-shaping processes. In this process, specified geometrical and surface properties are obtained through the break-up of material and removal by a cutting edge into a chip. The chip formation is associated with large strains, high strain rates and locally high temperatures due to adiabatic heating. These phenomena together with numerical complications make modeling of metal cutting difficult. Material models, which are crucial in metal-cutting simulations, are usually calibrated based on data from material testing. Nevertheless, the magnitudes of strains and strain rates involved in metal cutting are several orders of magnitude higher than those generated from conventional material testing. Therefore, a highly desirable feature is a material model that can be extrapolated outside the calibration range. In this study, a physically based plasticity model based on dislocation density and vacancy concentration is used to simulate orthogonal metal cutting of AISI 316L. The material model is implemented into an in-house particle finite-element method software. Numerical simulations are in agreement with experimental results, but also with previous results obtained with the finite-element method.

Place, publisher, year, edition, pages
Springer, 2017
National Category
Applied Mechanics Other Materials Engineering
Research subject
Solid Mechanics; Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-3280 (URN)10.1007/s40571-016-0120-9 (DOI)000417457300005 ()2-s2.0-85026434550 (Scopus ID)1162f8b7-aa09-4110-a750-247255072ce5 (Local ID)1162f8b7-aa09-4110-a750-247255072ce5 (Archive number)1162f8b7-aa09-4110-a750-247255072ce5 (OAI)
Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-06-05Bibliographically approved
Rodriguez Prieto, J. M., Jonsén, P. & Svoboda, A. (2016). A Particle Finite Element Method for Machining Simulations (ed.). In: (Ed.), M. Papadrakakis; V. Papadopoulos; G. Stefanou; V. Plevris (Ed.), ECCOMAS Congress 2016: VII European Congress on Computational Methods in Applied Sciences and Engineering, Crete Island, Greece, 5–10 June 2016. Paper presented at VII European Congress on Computational Methods in Applied Sciences and Engineering, Crete Island, Greece, 5–10 June 05/06/2016 - 10/06/2016 (pp. 539-553). Athens: National Technical University of Athens, 1
Open this publication in new window or tab >>A Particle Finite Element Method for Machining Simulations
2016 (English)In: ECCOMAS Congress 2016: VII European Congress on Computational Methods in Applied Sciences and Engineering, Crete Island, Greece, 5–10 June 2016 / [ed] M. Papadrakakis; V. Papadopoulos; G. Stefanou; V. Plevris, Athens: National Technical University of Athens , 2016, Vol. 1, p. 539-553Conference paper, Published paper (Refereed)
Abstract [en]

Metal cutting process is a nonlinear dynamic problem that includes geometrical, material, and contact nonlinearities. In this work a Lagrangian finite element approach for simulation of metal cutting processes is presented, based on the so-called Particle Finite Ele-ment Method (PFEM). The governing equations for the deformable bodies are discretized with the FEM via a mixed formulation using simplicial elements with equal linear interpolation for displacements, pressure and temperature. The use of PFEM for modeling of metal cutting pro-cesses includes the use of a remeshing process, α -shape concepts for detecting domain bound-aries, contact mechanics laws and material constitutive models. The merits of the formulation are demonstrated in the solution of 2D and 3D thermally-coupled metal cutting processes using the particle finite element method. The method shows good results and is a promising method for future simulations of thermally/coupled machining processes.

Place, publisher, year, edition, pages
Athens: National Technical University of Athens, 2016
National Category
Applied Mechanics Other Materials Engineering
Research subject
Solid Mechanics; Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-34341 (URN)2-s2.0-84995404839 (Scopus ID)88452a73-5c52-4c19-8e51-43441c87605e (Local ID)88452a73-5c52-4c19-8e51-43441c87605e (Archive number)88452a73-5c52-4c19-8e51-43441c87605e (OAI)
Conference
VII European Congress on Computational Methods in Applied Sciences and Engineering, Crete Island, Greece, 5–10 June 05/06/2016 - 10/06/2016
Note

Godkänd; 2016; 20160606 (parj)

Available from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-06-05Bibliographically approved
Abiri, O., Svoboda, A., Lindgren, L.-E. & Wedberg, D. (2016). Controlling Thermal Softening Using Non-Local Temperature Field in Modelling. Journal of Machining and Forming Technologies, 8(1-2), 13-28
Open this publication in new window or tab >>Controlling Thermal Softening Using Non-Local Temperature Field in Modelling
2016 (English)In: Journal of Machining and Forming Technologies, ISSN 1947-4369, Vol. 8, no 1-2, p. 13-28Article in journal (Refereed) Published
Abstract [en]

One of the aims of this work is to show that thermal softening due to the reduced flow strength of a material with increasing temperature may cause chip serrations to form during machining. The other purpose, the main focus of the paper, is to demonstrate that a non-local temperature field can be used to control these serrations. The non-local temperature is a weighted average of the temperature field in the region surrounding an integration point. Its size is determined by a length scale. This length scale may be based on the physics of the process but is taken here as a regularization parameter.

Place, publisher, year, edition, pages
Nova Science Publishers, Inc., 2016
Keywords
Finite element simulation, non-local temperature, plasticity, machining
National Category
Applied Mechanics Other Materials Engineering
Research subject
Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-63955 (URN)
Projects
LiGHTer
Funder
VINNOVA
Available from: 2017-06-13 Created: 2017-06-13 Last updated: 2017-11-24Bibliographically approved
Rodriguez Prieto, J. M., Jonsén, P. & Svoboda, A. (2016). On the Numerical Modeling of Metal Forming Processes Using the Particle Finite Elementmethod. In: Ragnar Larsson (Ed.), Proceedings of 29th Nordic Seminar on Computational Mechanics – NSCM29: . Paper presented at 29th Nordic Seminar on Computational Mechanics – NSCM29, Göteborg, Sweden, on October 26-28, 2016. Göteborg: Department of Applied Mechanics CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden 2016
Open this publication in new window or tab >>On the Numerical Modeling of Metal Forming Processes Using the Particle Finite Elementmethod
2016 (English)In: Proceedings of 29th Nordic Seminar on Computational Mechanics – NSCM29 / [ed] Ragnar Larsson, Göteborg: Department of Applied Mechanics CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden 2016 , 2016, , p. 4Conference paper, Published paper (Refereed)
Abstract [en]

In this work a Lagrangian nite element approach for simulation of metalforming is presented, based on the so-called Particle Finite Element Method (PFEM). Thegoverning equations for the deformable bodies are discretized with the FEM via a mixedformulation using simplicial elements with equal linear interpolation for displacements,pressure and temperature. The use of PFEM for modeling of metal forming processesincludes the use of a remeshing process, -shape concepts for detecting domain boundaries,contact mechanics laws and material constitutive models. The merits of the formulationare demonstrated in the solution of 2D thermally coupled metal forming processes usingthe particle nite element method. The method shows good results and is a promisingmethod for future simulations of thermally/coupled forming processes.

Place, publisher, year, edition, pages
Göteborg: Department of Applied Mechanics CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden 2016, 2016. p. 4
Series
Forskningsrapporter : tillämpad mekanik / Chalmers tekniska högskola, ISSN 1652-8549
Keywords
Particle nite element method (PFEM), metal forming. machining, cutting
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
urn:nbn:se:ltu:diva-60470 (URN)
Conference
29th Nordic Seminar on Computational Mechanics – NSCM29, Göteborg, Sweden, on October 26-28, 2016
Available from: 2016-11-15 Created: 2016-11-15 Last updated: 2018-06-05Bibliographically approved
Lindgren, L.-E., Svoboda, A., Wedberg, D. & Lundblad, M. (2016). Towards predictive simulations of machining (ed.). Paper presented at . Comptes rendus. Mecanique, 344(4-5), 284-295
Open this publication in new window or tab >>Towards predictive simulations of machining
2016 (English)In: Comptes rendus. Mecanique, ISSN 1631-0721, E-ISSN 1873-7234, Vol. 344, no 4-5, p. 284-295Article in journal (Refereed) Published
Abstract [en]

Machining simulations are challenging with respect to both numerical issues and physical phenomena occurring during machining. The latter are mainly related to the description of the bulk material behaviour (plasticity) and surface properties (friction and wear). The aim of this paper is to present what is required for predictive models, depending on their scopes, as well as the needed developments for the future. The paper includes a short review of selected works that are relevant for this purpose as well as conclusions based on our own experience

National Category
Other Materials Engineering
Research subject
Material Mechanics
Identifiers
urn:nbn:se:ltu:diva-6009 (URN)10.1016/j.crme.2015.06.010 (DOI)000373704800007 ()2-s2.0-84959449802 (Scopus ID)433a8c60-864f-40c8-8e5c-35adb78aa830 (Local ID)433a8c60-864f-40c8-8e5c-35adb78aa830 (Archive number)433a8c60-864f-40c8-8e5c-35adb78aa830 (OAI)
Note
Validerad; 2016; Nivå 2; 20160314 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Organisations

Search in DiVA

Show all publications