| 1. |
- Abiri, Olufunminiyi, et al.
(författare)
-
Controlling Thermal Softening Using Non-Local Temperature Field in Modelling
- 2016
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Ingår i: Journal of Machining and Forming Technologies. - : Nova Science Publishers, Inc.. - 1947-4369. ; 8:1-2, s. 13-28
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Abiri, Olufunminiyi, et al.
(författare)
-
Non-Local Modelling of Strain Softening in Machining Simulations
- 2017
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Ingår i: IOP Conference Series. - : Institute of Physics (IOP). - 1757-8981 .- 1757-899X. ; 225
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Babu, Bijish, Tec. Lic. 1979-, et al.
(författare)
-
Dislocation density based plasticity model extended to high strain rate deformation of Ti-6Al-4V
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 4. |
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| 5. |
- Dini, Hoda, 1984-, et al.
(författare)
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Optimization and validation of a dislocation density based constitutive model for as-cast Mg-9%Al-1%Zn
- 2018
-
Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 710, s. 17-26
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 6. |
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| 7. |
- Jeppsson, Peter, et al.
(författare)
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Integrated design and verification system for finite element modelling
- 1993
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Ingår i: Concurrent Engineering - Research and Applications. - 1063-293X .- 1531-2003. ; 1:4, s. 213-217
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Lindgren, Lars-Erik, et al.
(författare)
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Challenges in finite element simulations of chain of manufacturing processes
- 2013
-
Ingår i: Physical and numerical simulation of materials processing VII. - Durnten-Zurich : Trans Tech Publications Inc.. - 9783037857281 ; , s. 349-353
-
Konferensbidrag (refereegranskat)abstract
- 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
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| 9. |
- Lindgren, Lars-Erik, et al.
(författare)
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Towards predictive simulations of machining
- 2016
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Ingår i: Comptes rendus. Mecanique. - : Elsevier BV. - 1631-0721 .- 1873-7234. ; 344:4-5, s. 284-295
-
Tidskriftsartikel (refereegranskat)abstract
- 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
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| 10. |
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| 11. |
- Norman, Peter, et al.
(författare)
-
A sophisticated platform for characterization, monitoring and control of machining
- 2006
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Ingår i: Measurement science and technology. - BRISTOL, ENGLAND : IOP Publishing. - 0957-0233 .- 1361-6501. ; 17:4, s. 847-854
-
Tidskriftsartikel (refereegranskat)abstract
- 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
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| 12. |
- Rodríguez, Juan Manuel, et al.
(författare)
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A particle finite element method applied to modeling and simulation of machining processes
- 2017. - 1 ed
-
Ingår i: Advanced Machining Processes. - Boca Raton : CRC Press. - 9781138033627 - 9781315305271 ; , s. 1-24
-
Bokkapitel (refereegranskat)abstract
- Metal cutting process is a nonlinear dynamic problem that includesgeometrical, material, and contact nonlinearities. In this work, aLagrangian finite element approach for the simulation of metal cuttingprocess is presented based on the so-called particle finite element method(PFEM). The governing equations for the deformable bodies are discretizedwith the finite element method (FEM) via a mixed formulationusing simplicial elements with equal linear interpolation for displacements,pressure, and temperature. The use of PFEM for modeling ofmetal cutting processes includes the use of a remeshing process, α-shapeconcepts for detecting domain boundaries, contact mechanics laws, andmaterial constitutive models. In this chapter, a 2D PFEM-based numericalmodeling of metal cutting processes has been studied to investigate theeffects of cutting velocity on tool forces, temperatures, and stresses inmachining of Ti–6Al–4V. The Johnson–Cook plasticity model is usedto describe the work material behavior. Numerical simulations are inagreement with experimental results.
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| 13. |
- Rodriguez, Juan Manuel, et al.
(författare)
-
Dislocation Density Based Material Model Applied in PFEM-simulation of Metal Cutting
- 2017
-
Ingår i: Procedia CIRP. - : Elsevier. - 2212-8271 .- 2212-8271. ; 58, s. 193-197
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 14. |
- Rodriguez Prieto, Juan Manuel, et al.
(författare)
-
A Particle Finite Element Method for Machining Simulations
- 2016
-
Ingår i: ECCOMAS Congress 2016. - Athens : National Technical University of Athens. ; , s. 539-553
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 15. |
- Rodriguez Prieto, Juan Manuel, et al.
(författare)
-
Numerical modeling of metal cutting processes using the particle finite element method (PFEM) and a physically based plasticity model
- 2015
-
Ingår i: Particle-based Methods IV. - Barcelona : International Center for Numerical Methods in Engineering (CIMNE). - 9788494424472 ; , s. 1066-1072
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 16. |
- Rodriguez Prieto, Juan Manuel, et al.
(författare)
-
On the Numerical Modeling of Metal Forming Processes Using the Particle Finite Elementmethod
- 2016
-
Ingår i: Proceedings of 29th Nordic Seminar on Computational Mechanics – NSCM29. - Göteborg : Department of Applied Mechanics CHALMERS UNIVERSITY OF TECHNOLOGY Göteborg, Sweden 2016.
-
Konferensbidrag (refereegranskat)abstract
- 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.
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| 17. |
- Rodriguez Prieto, Juan Manuel, et al.
(författare)
-
Simulation of metal cutting using the particle finite-element method and a physically based plasticity model
- 2017
-
Ingår i: Computational Particle Mechanics. - : Springer. - 2196-4378 .- 2196-4386. ; 4:1, s. 35-51
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 18. |
- Salomonsson, Kent, et al.
(författare)
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Modeling and Analysis of a Screw Fitting Assembly Process Involving a Cast Magnesium Component
- 2020
-
Ingår i: Frontiers in Materials. - : Frontiers Media S.A.. - 2296-8016. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- A finite element analysis of a complex assembly was made. The material description used was a physically based material model with dislocation density as an internal state variable. This analysis showed the importance of the materials’ behavior in the process as there is discrepancy between the bolt head contact pressure and the internals state of the materials where the assembly process allows for recovery. The end state is governed by both the tightening process and the thermal history and strongly influenced by the thermal expansion of the AZ91D alloy.
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| 19. |
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| 20. |
- Svoboda, Ales
(författare)
-
Computational modelling of hot isostatic pressing
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 21. |
- Svoboda, Ales, et al.
(författare)
-
Determination of material parameters for simulation of hot isostatic pressing
- 1995
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Ingår i: Computational Methods and Experimental Measurements VII, 16-18 May 1995, Italy. - Southampton : WIT Press. - 1853123137 ; , s. 29-29
-
Konferensbidrag (refereegranskat)abstract
- 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
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| 22. |
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| 23. |
- Svoboda, Ales
(författare)
-
Finita element simulering av plåtformning : förstudie
- 2001
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 24. |
- Svoboda, Ales, et al.
(författare)
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Integrated approach for prediction of stability limits for machining with large volumes of material removal
- 2008
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 46:12, s. 3207-3222
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 25. |
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| 26. |
- Svoboda, Ales, et al.
(författare)
-
Simulation of hot isostatic pressing of a powder metal component with an internal core
- 1997
-
Ingår i: Computer Methods in Applied Mechanics and Engineering. - 0045-7825 .- 1879-2138. ; 148:3-4, s. 299-314
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 27. |
- Svoboda, Ales, et al.
(författare)
-
Simulation of hot isostatic pressing of metal powder components to near net shape
- 1996
-
Ingår i: Engineering computations. - : Emerald. - 0264-4401 .- 1758-7077. ; 13:5, s. 13-37
-
Tidskriftsartikel (refereegranskat)abstract
- 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
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| 28. |
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| 29. |
- Svoboda, Ales, et al.
(författare)
-
Simulation of metal cutting using a physically based plasticity model
- 2010
-
Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 18:7
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 30. |
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| 31. |
- Svoboda, Ales, et al.
(författare)
-
The effective stress function algorithm for pressure‐dependent plasticity applied to hot isostatic pressing
- 1998
-
Ingår i: International Journal for Numerical Methods in Engineering. - 0029-5981 .- 1097-0207. ; 43:4, s. 587-606
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 32. |
- Wedberg, Dan, et al.
(författare)
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Modelling high strain rate phenomena in metal cutting simulation
- 2012
-
Ingår i: Modelling and Simulation in Materials Science and Engineering. - : IOP Publishing. - 0965-0393 .- 1361-651X. ; 20:8, s. 85006-
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 33. |
- Wikman, Bengt, et al.
(författare)
-
A combined material model for numerical simulation of hot isostatic pressing
- 2000
-
Ingår i: Computer Methods in Applied Mechanics and Engineering. - 0045-7825 .- 1879-2138. ; 189:3, s. 901-913
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 34. |
- Zamani, Mohammadreza, et al.
(författare)
-
A dislocation density based constitutive model for as-cast Al-Si alloys : Effect of temperature and microstructure
- 2017
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 121, s. 164-170
-
Tidskriftsartikel (refereegranskat)abstract
- 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.
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