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  • 1.
    Abiri, Olufunminiyi
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials. University of Johannesburg, South Africa.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Wedberg, Dan
    Controlling Thermal Softening Using Non-Local Temperature Field in Modelling2016In: Journal of Machining and Forming Technologies, ISSN 1947-4369, Vol. 8, no 1-2, p. 13-28Article in journal (Refereed)
    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.

  • 2.
    Abiri, Olufunminiyi
    et al.
    Institute of Intelligent Systems, University of Johannesburg.
    Wedberg, Dan
    AB Sandvik Coromant.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Non-Local Modelling of Strain Softening in Machining Simulations2017In: IOP Conference Series: Materials Science and Engineering, ISSN 1757-8981, E-ISSN 1757-899X, Vol. 225, article id 012053Article in journal (Refereed)
    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. 

  • 3.
    Babu, Bijish
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Ghassemali, Ehsan
    School of Engineering, Jönköping University..
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Dislocation density based plasticity model extended to high strain rate deformation of Ti-6Al-4VManuscript (preprint) (Other academic)
    Abstract [en]

    One of the main challenges in the simulation of machining is accurately describing the material behavior during severe plastic deformation at strain rates ranging six orders of magnitude and temperature between room temperature to nearly melting temperature. High strain rate measurements are performed using Split-Hopkinson Pressure Bar (SHPB) technique at a range of temperatures. The temperature change during deformation is included by computing the plastic work converted to heat energy. A physics-based material model published earlier (Babu and Lindgren, 2013) is extended in this paper to include the high strain rate mechanisms of phonon and electron drag. Characterization of the microstructure is performed using Electron Backscatter Diffraction (EBSD), and a novel method is proposed in this work to quantify the extent of globularization which is compared with model predictions.

  • 4.
    Dini, Hoda
    et al.
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Andersson, Nils-Eric
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Ghassemali, Ehsan
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Jarfors, Anders E.W.
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Optimization and validation of a dislocation density based constitutive model for as-cast Mg-9%Al-1%Zn2018In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 710, p. 17-26Article in journal (Refereed)
    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.

  • 5.
    Gedda, Hans
    et al.
    Luleå tekniska universitet.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    FE-analysis of laser spot welding of microelectronics devices2003In: Proceedings of the 16th Meeting on Modelling, Simulation, Virtuality in High Power Laser Technology, M4PL 16: Igls/Innsbruck, 22.01.2003-24.01.2003 / Vienna University of Technology, Department of Nonconventional Processing, Forming and Laser Technology / [ed] D. Schöcker, 2003Conference paper (Refereed)
  • 6.
    Holmberg, Jonas
    et al.
    Swerea IVF AB.
    Rodriguez Prieto, Juan Manuel
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Berglund, Johan
    Swerea IVF AB.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Experimental and PFEM-simulations of residual stresses from turning tests of a cylindrical Ti-6Al-4V shaft2018In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 71, p. 144-149Article in journal (Refereed)
    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.

  • 7.
    Jeppsson, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Integrated design and verification system for finite element modelling1993In: Concurrent Engineering - Research and Applications, ISSN 1063-293X, E-ISSN 1531-2003, Vol. 1, no 4, p. 213-217Article in journal (Refereed)
    Abstract [en]

    This paper presents a computer-integrated system for design, manufacturing simulation, and inspection using a coordinate measurement machine (CMM). The work is concerned with the problem of predicting the shape of the container for hot isostatic pressing (HIP) and it focuses on the verification of a finite element (FE) simulation model for HIP. The verification is performed by comparing the simulated geometry of a real component produced by HIP. The geometry of the HIP component is measured by a CMM. The whole process from design and manufactunng simulation to inspection and geometry verification is performed within a computer-aided concurrent engineering (CACE) system. The system is built on both commercial and non-commercial software. The communication between a CMM, a geometnc modelling system, and the finite element simulation codes is developed. The manufacturing of a turbine component to net shape geometry using HIP is chosen as a demonstrator example. The benefits of the presented CACE system are time and cost savings as well as higher product quality.

  • 8.
    Lindgren, Lars-Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lundbäck, Andreas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Edberg, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Challenges in finite element simulations of chain of manufacturing processes2013In: Physical and numerical simulation of materials processing VII: selected, peer reviewed papers from the 7th International Conference on Physical and Numerical Simulation of Materials Processing (ICPNS'13), June 16-19, 2013, Oulu, Finland / [ed] L. Pentti Karjalainen; David A. Porter; Seppo A. Järvenpää, Durnten-Zurich: Trans Tech Publications Inc., 2013, p. 349-353Conference paper (Refereed)
    Abstract [en]

    Simulation of some, or all, steps in a manufacturing chain may be important for certain applications in order to determine the final achieved properties of the component. The paper discusses the additional challenges in this context

  • 9.
    Lindgren, Lars-Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Wedberg, Dan
    AB Sandvik Coromant, Metal Cutting Research, Sandviken.
    Lundblad, Mikael
    AB Sandvik Coromant, Metal Cutting Research, Sandviken.
    Towards predictive simulations of machining2016In: Comptes rendus. Mecanique, ISSN 1631-0721, E-ISSN 1873-7234, Vol. 344, no 4-5, p. 284-295Article in journal (Refereed)
    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

  • 10.
    Lindgren, Lars-Erik
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Wedberg, Dan
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Verification and validation of machining simulations for sufficient accuracy2009In: Computational Plasticity X: fundamentals and applications ; proceedings of the X International Conference on Computational Plasticity - fundamentals and applications held in Barcelona, Spain, 02 - 04 September 2009 / [ed] E. Onate, International Center for Numerical Methods in Engineering (CIMNE), 2009Conference paper (Refereed)
  • 11.
    Norman, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Bäckström, Mikael
    Luleå tekniska universitet.
    Rantatalo, Matti
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Operation, Maintenance and Acoustics.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Kaplan, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    A sophisticated platform for characterization, monitoring and control of machining2006In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 17, no 4, p. 847-854Article in journal (Refereed)
    Abstract [en]

    The potential for improving the performance of machine tools is considerable. However, for this to be achieved without tool failure or product damage, the process must be sufficiently well understood to enable real-time monitoring and control to be applied. A unique sophisticated measurement platform has been developed and applied to two different machining centres, particularly for high-speed machining up to 24 000 rpm. Characterization and on-line monitoring of the dynamic behaviour of the machining processes has been carried out using both contact-based methods (accelerometer, force sensor) and non-contact methods (laser Doppler vibrometry and magnetic shaker) and numerical simulation (finite element based modal analysis). The platform was applied both pre-process and on-line for studying an aluminium testpiece based on a thin-walled aerospace component. Stability lobe diagrams for this specific machine/component combination were generated allowing selection of optimal process parameters giving stable cutting and metal removal rates some 8-10 times higher than those possible in unstable machining. Based on dynamic characterization and monitoring, a concept for an adaptive control with constraints based machine tool controller has been developed. The developed platform can be applied in manifold machining situations. It offers a reliable way of achieving significant process improvement

  • 12.
    Rodriguez, Juan Manuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Dislocation Density Based Material Model Applied in PFEM-simulation of Metal Cutting2017In: Procedia CIRP, ISSN 2212-8271, E-ISSN 2212-8271, Vol. 58, p. 193-197Article in journal (Refereed)
    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.

  • 13.
    Rodriguez Prieto, Juan Manuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    A Particle Finite Element Method for Machining Simulations2016In: 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 (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.

  • 14.
    Rodriguez Prieto, Juan Manuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Numerical modeling of metal cutting processes using the particle finite element method (PFEM) and a physically based plasticity model2015In: Particle-based Methods IV: Fundamentals and Applications : Proceedings of the IVInternational Conference on Particle-Based Methods–Fundamentals and Applications held in Barcelona, Spain, 28-30September 2015 / [ed] E. Oñate; M. Bischoff; D.R.J. Owen; P. Wriggers; T. Zhodi, Barcelona: International Center for Numerical Methods in Engineering (CIMNE), 2015, p. 1066-1072Conference paper (Refereed)
    Abstract [en]

    Metal cutting is one of the most common metal shaping processes. Specified geometrical and surface properties are obtained by break-up of material and removal by a cutting edge into a chip. The chip formation is associated with large strain, high strain rate and locally high temperature due to adiabatic heating which make the modeling of cutting processes difficult. Furthermore, dissipative plastic and friction work generate high local temperatures. 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 magnitude of strain and strain rate involved in metal cutting are several orders 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.

  • 15.
    Rodriguez Prieto, Juan Manuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    On the Numerical Modeling of Metal Forming Processes Using the Particle Finite Elementmethod2016In: 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 (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.

  • 16.
    Rodriguez Prieto, Juan Manuel
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Simulation of metal cutting using the particle finite-element method and a physically based plasticity model2017In: Computational Particle Mechanics, ISSN 2196-4378, Vol. 4, no 1, p. 35-51Article in journal (Refereed)
    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.

  • 17.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Computational modelling of hot isostatic pressing1997Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The objective of this work was the development of a computer aided concurrent engineering system (CACE) for manufacturing simulation with particular application to hot isostatic pressing (HIP). The physical and mechanical phenomena connected with the hot isostatic pressing of powder metallurgical materials are analysed. During the HIP process the initial porosity in the powder material is eliminated due to the simultaneous application of heat and pressure, and the powder is compacted into a fully dense material. Due to effects of container rigidity and nonuniform distribution of temperature and relative density during the HIP process, the final shape and size of a component often differ from the required shape and size. For the successful application of HIP technology in industry, it is important to obtain HIP products with near net shape (NNS) geometry in order to reduce the costs of extra machining, especially in the case of difficult to machine materials. It is difficult for designers to predict the size and shape of a container in order to achieve the required geometry of a component. The work presented here is concerned with the problem of prediction the shape of the container for the HIP process. The complex thermal and deformation histories which occur in this process have been simulated by means of implicit, finite element codes. An efficient solution of this problem is necessary to make large and complex analyses feasible. Two algorithms for the accurate and effective integration of pressure sensitive constitutive equations are presented in this study. A macromechanical approach using constitutive equations was able to correctly represent the densification behaviour of a powder material during the whole HIP cycle, provided that these equations are properly fitted to experimental data. An experimental program was carried out to identify material parameters for a gas atomized martensitic stainless steel powder, denoted APM 2390. A nonlinear least squares method was applied to the problem to determine the parameters of the constitutive law. In the CACE system, data from a coordinate measuring machine (CMM) was used to verify the accuracy of the simulated geometry in comparison with the final geometry of the HIPed products. The accurate simulation of HIP process allows optimization of the HIP process parameters which is essential for the cost effective manufacture of parts with complex geometry.

  • 18.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Finita element simulering av plåtformning: förstudie2001Report (Other academic)
    Abstract [sv]

    Förstudien sammanfattar erfarenheter från applikationer med finita element metoden inom simulering av plåtformning. Som simuleringsverktyg inom virtuell verifiering vid Avdelningen för produktionsutveckling, Luleå tekniska universitet har PAM-STAMP anskaffats. Programmet har testats och utvärderats. De första erfarenheterna av PAM-STAMP tyder på att programvara är väl anpassad och direkt användbar för simulering av formningsprocesser.Förstudie har genomförts med ekomoniskt stöd från Pressoform AB.

  • 19.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Modelling and simulation of hot isostatic pressing of metal powder1994Licentiate thesis, comprehensive summary (Other academic)
  • 20.
    Svoboda, Ales
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Björk, L.
    Häggblad, Hans-åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Determination of material parameters for simulation of hot isostatic pressing1995In: Computational Methods and Experimental Measurements VII, 16-18 May 1995, Italy / [ed] G.M. Carlomagno; C.A. Brebbia, Southampton: WIT Press, 1995, p. 29-29Conference paper (Refereed)
    Abstract [en]

    HIP is an established process for compacting powder metallurgical materials. The numerical analysis of HIP of metal powder requires accurate material models of the technologically applied powder materials. In order to show correct behavior, the constitutive models have to be based on proper experimental procedures. An investigation of the transient densification behavior of a martensitic stainless steel powder during the HIP process and development of a tool for determination of material parameters of the related constitutive model has been carried out. The work concludes with the usefulness of optimization methods combined with HIP dilatometry in fitting material parameters for complex material models

  • 21.
    Svoboda, Ales
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Häggblad, Hans-Åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Jonsén, Pär
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Simulations of hot isostatic powder pressing for near net shaped components2014In: 11th International Conference on Hot Isostatic Pressing 2014: HIP'14 in Stockholm, Sweden 9 - 13, 2014, Stockholm: Jernkontoret , 2014, p. 80-87Conference paper (Refereed)
  • 22.
    Svoboda, Ales
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Häggblad, Hans-åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Karlsson, Lennart
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Simulation of hot isostatic pressing of a powder metal component with an internal core1997In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 148, no 3-4, p. 299-314Article in journal (Refereed)
    Abstract [en]

    This paper presents a finite element simulation of the thermomechanical phenomena occurring during Hot Isostatic Pressing (HIP) of a powder metal component which includes a graphite core. The thermomechanical coupling is achieved in a staggered step manner. The staggered step approach considers the coupled thermomechanical response of solids, including nonlinear effects in both the thermal and mechanical analyses. The creep behaviour of the powder material during densification is modelled using the constitutive equations of thermal elasto-viscoplastic type with compressibility. The various mechanical material properties are assumed to be functions of temperature and relative density. The mechanical solution also includes large deformation and strains. The thermal problem includes temperature and relative density dependent specific heat and thermal conductivity. The constitutive equations and relations for thermal characteristics are implemented into the implicit nonlinear finite element code, PALM2D. The simulation of the HIP process of a component with internal core is chosen as an application example. The component, injection molding tool, is produced of a hot isostatically pressed stainless tool steel with an internal cavity which is achieved by inserting a graphite core into the HIP container. To verify the result of the simulation, the geometry of the capsule and the coated core are measured both before and after pressing using a computer controlled measurement machine (CMM). The measured geometry is compared with the simulated final shapes of the container and internal core. A computer-aided concurrent engineering system (CACE) is used for the complete manufacturing process from the design of the component and finite element simulation to the inspection of the final geometry.

  • 23.
    Svoboda, Ales
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Häggblad, Hans-åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Laptev, A.
    Bouaziz, O.
    Dellis, C.
    Experimental characterisation of powder for use in simulation of hot isostatic pressing1997In: Proceedings of International workshop on Modelling of Metal Powder Forming Processes, Grenoble, France, 1997Conference paper (Refereed)
  • 24.
    Svoboda, Ales
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Häggblad, Hans-åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Näsström, Mats
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Simulation of hot isostatic pressing of metal powder components to near net shape1996In: Engineering computations, ISSN 0264-4401, E-ISSN 1758-7077, Vol. 13, no 5, p. 13-37Article in journal (Refereed)
    Abstract [en]

    Presents a finite element formulation of hot isostatic pressing (HIP) based on a continuum approach using thermal-elastoviscoplastic constitutive equations with compressibility. The formulation takes into consideration dependence of the viscoplastic part on the porosity. Also takes into account the thermomechanical response, including nonlinear effects in both the thermal and mechanical analyses. Implements the material model in an implicit finite element code. Presents experimental procedures for evaluating the inelastic behaviour of metal powders during densification and experimental data. Chooses the simulation of the dilatometer measurement of a cylindrical component during HIP and manufacturing simulation of a turbine component to near net shape (NNS) as a demonstrator example. Both components are made of a hot isostatically pressed hot-working martensitic steel. Compares the result of the simulation in the form of the final geometry of the container with the geometry of a real component produced by HIP. Makes a comparison between the calculated and measured deformations during the HIP process for the cylindrical component. Measures the final geometry of the turbine component by means of a computer controlled measuring machine (CMM). Performs the complete process from design and simulation to geometry verification within a computer-aided concurrent engineering (CACE) system

  • 25.
    Svoboda, Ales
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lindgren, Lars-Erik
    Oddy, Alan S.
    Oddy/McDIll Numerical Investigations Sciences, Inc..
    Effective stress function algorithm for pressure-dependent plasticity applied to hot isostatic pressing1998In: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 43, no 4, p. 587-606Article in journal (Refereed)
    Abstract [en]

    An algorithm for unconditionally stable and accurate integration of elasto-viscoplastic pressure-dependent constitutive model is presented. Rate form constitutive equations of thermal-elastoviscoplastic type with compressibility take into account the changes in relative density. The algorithm computes the deviatoric and volumetric creep strains by finding the value of the effective stress which satisfies the functional relationship, the effective stress function. Thus, one non-linear scalar equation is solved to find the unknown volumetric and deviatoric components of creep strain tensor. The tangent modulus is evaluated consistent with the integration algorithm. The application of the method to the simulation of hot isostatic pressing of metal powder is shown. The paper presents the solution of the verification problem and comparison with the experimental result.

  • 26.
    Svoboda, Ales
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Tatar, Kourosh
    Norman, Peter
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Product and Production Development.
    Bäckström, Mikael
    Luleå tekniska universitet.
    Integrated approach for prediction of stability limits for machining with large volumes of material removal2008In: International Journal of Production Research, ISSN 0020-7543, E-ISSN 1366-588X, Vol. 46, no 12, p. 3207-3222Article in journal (Refereed)
    Abstract [en]

    High-speed machining of thin-walled structures is widely used in the aeronautical industry. Higher spindle speed and machining feed rate, combined with a greater depth of cut, increases the removal rate and with it, productivity. The combination of higher spindle speed and depth of cut makes instabilities (chatter) a far more significant concern. Chatter causes reduced surface quality and accelerated tool wear. Since chatter is so prevalent, traditional cutting parameters and processes are frequently rendered ineffective and inaccurate. For the machine tool to reach its full utility, the chatter vibrations must be identified and avoided. In order to avoid chatter and implement optimum cutting parameters, the machine tool including all components and the work piece must be dynamically mapped to identify vibration characteristics. The aim of the presented work is to develop a model for the prediction of stability limits as a function of process parameters. The model consists of experimentally measured vibration properties of the spindle-tool, and finite element calculations of the work piece in (three) different stages of the process. Commercial software packages used for integration into the model prove to accomplish demands for functionality and performance. A reference geometry that is typical for an aircraft detail is used for evaluation of the prediction methodology. In order to validate the model, the stability limits predicted by the use of numerical simulation are compared with the results based on the experimental work.

  • 27.
    Svoboda, Ales
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Wedberg, Dan
    Lindgren, Lars-Erik
    Simulation of metal cutting using a physically based plasticity model2010In: Modelling and Simulation in Materials Science and Engineering, ISSN 0965-0393, E-ISSN 1361-651X, Vol. 18, no 7Article in journal (Refereed)
    Abstract [en]

    Metal cutting is one of the most common metal shaping processes. Specified geometrical and surface properties are obtained by break-up of the material removed by the cutting edge into a chip. The chip formation is associated with a large strain, high strain rate and a locally high temperature due to adiabatic heating which make the modelling of cutting processes difficult. This study compares a physically based plasticity model and the Johnson-Cook model. The latter is commonly used for high strain rate applications. Both material models are implemented into the finite element software MSC.Marc and compared with cutting experiments. The deformation behaviour of SANMAC 316L stainless steel during an orthogonal cutting process is studied.

  • 28.
    Svoboda, Ales
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Wedberg, Dan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Kalhori, Vahid
    AB Sandvik Coromant, Sandviken.
    Lundblad, Mikael
    AB Sandvik Coromant, Sandviken.
    Simulation of mechanical cutting using a material model based on dislocation density2007In: Computational plasticity X: Fundamentals and Applications, International Center for Numerical Methods in Engineering (CIMNE), 2007, Vol. 1, p. 330-334Conference paper (Refereed)
  • 29.
    Svoboda, Ales
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Wikman, Bengt
    Häggblad, Hans-åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    A coupled plastic and viscoplastic model for modelling of hot isostatic pressing1998In: First ESAFORM Conference on Material Forming : Sophia-Antipolis (France), 17 - 20 March 1998, European Scientific Association for Material Forming Centre de Mise en Forme des Matériaux , 1998Conference paper (Refereed)
  • 30.
    Wedberg, Dan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Modelling high strain rate phenomena in metal cutting simulation2012In: Modelling and Simulation in Materials Science and Engineering, ISSN 0965-0393, E-ISSN 1361-651X, Vol. 20, no 8, p. 85006-Article in journal (Refereed)
    Abstract [en]

    Chip formation in metal cutting is associated with large strains and high strain rates, concentrated locally to deformation zones in front of the tool and beneath the cutting edge. Furthermore, dissipative plastic work and friction work generate high local temperatures. These phenomena together with numerical complications make modelling of metal cutting difficult. Material models, which are crucial in metal cutting simulations, are usually calibrated based on data from material testing. Nevertheless, the magnitude of strains and strain rates involved in metal cutting are several orders higher than those generated from conventional material testing. A highly desirable feature is therefore a material model that can be extrapolated outside the calibration range. In this study, two variants of a flow stress model based on dislocation density and vacancy concentration are used to simulate orthogonal metal cutting of AISI 316L stainless steel. It is found that the addition of phonon drag improves the results somewhat but the addition of this phenomenon still does not make it possible to extrapolate the constitutive model reliably outside its calibration range.

  • 31. Wikman, Bengt
    et al.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Häggblad, Hans-åke
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    A combined material model for numerical simulation of hot isostatic pressing2000In: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 189, no 3, p. 901-913Article in journal (Refereed)
    Abstract [en]

    In modelling of hot isostatic pressing (HIP) of powder materials the constitutive model should be able to describe different deformation mechanisms during the consolidation process. In the early stage, the consolidation is dominated by granular behaviour. As temperature and pressure increase in the powder the deformation can be described by a viscoplastic model. Experimental observations show substantial time-independent deformation in the early stage. At this stage of the densification process, pores in the powder are still interconnected. This cannot be described properly by a viscoplastic model. The inconsistency between the deformation mechanisms can be treated by a combined elasto-plastic and elasto-viscoplastic model. Here a granular plasticity model is combined with a viscoplastic model. In previous works the viscoplastic model, power-law breakdown, has been used to describe the entire deformation process. The combined model is implemented into an in-house finite deformation code for the solution of coupled thermomechanical problems. The simulation of a hot isostatic pressing test with dilatometer is performed in order to compare calculated results with the experimental measurement. The results from previously performed analysis carried out with a viscoplastic model only are also compared. Analysis with the combined material model shows good agreement with the experiment for the whole densification process.

  • 32.
    Zamani, Mohammadreza
    et al.
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Dini, Hoda
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Svoboda, Ales
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Lindgren, Lars-Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mechanics of Solid Materials.
    Seifeddine, Salem
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Andersson, Nils-Eric
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    Jarfors, Anders E.W.
    Department of Materials and Manufacturing, School of Engineering, Jönköping University.
    A dislocation density based constitutive model for as-cast Al-Si alloys: Effect of temperature and microstructure2017In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 121, p. 164-170Article in journal (Refereed)
    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.

1 - 32 of 32
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