| 1. |
- Azizoğlu, Yağız, et al.
(författare)
-
Finite element modeling of tube deformation during cold pilgering
- 2016
-
Ingår i: MATEC Web of Conferences. - : EDP Sciences. ; , s. 1-8
-
Konferensbidrag (refereegranskat)abstract
- A three-dimensional finite element model of cold pilgering of stainless steel tubes is developed in this paper. The objective is to use the model to increase the understanding of forces and deformations in the process. The focus is on the influence of vertical displacements of the roll stand and axial displacements of the mandrel and tube. Therefore, the rigid tools and the tube are supported with elastic springs. Additionally, the influences of friction coefficients in the tube/mandrel and tube/roll interfaces are examined. A sensitivity study is performed to investigate the influences of these parameters on the strain path and the roll separation force. The results show the importance of accounting for the displacements of the tube and rigid tools on the roll separation force and the accumulative plastic strain.
|
|
| 2. |
- Azizoğlu, Yağız, et al.
(författare)
-
Finite element modelling of cold pilgering of tubes
- 2015
-
Ingår i: Proceedings of the 8th International Conference on Computational Plasticity - Fundamentals and Applications, COMPLAS 2015. - Barcelona : International Center for Numerical Methods in Engineering (CIMNE). - 9788494424465 ; , s. 716-726
-
Konferensbidrag (refereegranskat)abstract
- Cold pilgering is a cold forming process used during manufacturing of seamless tubes. The tube with a mandrel inside is fed forward and rotated in stepwise increments, while the roll stand moves back and forth. The total plastic deformation of the tube is such that the cross-sectional area of the tube decreases and the length of the tube increases during the process. However, this is performed in many small incremental steps, where the direction of deformation in a material point changes at each stroke. Most published models of cold pilgering use simplified material models. In reality, the flow stress is dependent on temperature, strain rate, strain history and microstructure. In this work, temperature and strain rate distributions are computed, using a 3D thermo-mechanical FE model, and the influence of temperature and strain rate on the rolling force is investigated. The Johnson-Cook model is employed to describe the flow stress using isotropic hardening. The results show that strain rate and temperature have a significant influence on the roll separation force.
|
|
| 3. |
- Fisk, Martin, et al.
(författare)
-
FE-Simulation of combined induction heating and extrusion in manufacturing of stainless steel tubes
- 2009
-
Ingår i: Computational Plasticity X. - Barcelona : International Center for Numerical Methods in Engineering (CIMNE). - 9788496736696
-
Konferensbidrag (refereegranskat)abstract
- The manufacturing process chain for extrusion of AISI 316L tubes is simulated using the finite element method. Models of induction heating and expansion is included and the temperature field in the billet before extrusion is calculated. It is shown that a correct initial temperature of the billet is needed in order to predict the extrusion force curve in the initial stage of the process.
|
|
| 4. |
- Gyhlesten Back, Jessica, et al.
(författare)
-
Influence of prior deformation in austenite on the martensite formation in a low-alloyed carbon steel
- 2019
-
Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 941, s. 95-99
-
Tidskriftsartikel (refereegranskat)abstract
- The current work aims at developing models supporting design of the rolling and quenching processes. This requires a martensite formation model that can account for effect of previous plastic deformation as well as evolution of stress and temperature during the quenching step. The effect of deformation prior to the cooling on the transformation is evaluated. The experimental result shows that prior deformation impedes the martensite transformation due to the mechanical stabilisation of the austenite phase. Larger deformation above 30 % reduces the effect of the mechanical stabilisation due to increase in martensite nucleation sites. The computed transformation curves, based on an extended version of the Koistinen-Marburger equation, agree well with experimental results for pre-straining less than 30 %.
|
|
| 5. |
|
|
| 6. |
- Hansson, Sofia
(författare)
-
Modeling of the Stainless Steel Tube Extrusion Process
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Seamless tubes of stainless steel can be extruded using glass as a lubricant in the Ugine-Sejournet process. The process is performed at high temperature and is associated with large deformations and high strain rates. The use of finite element modeling (FEM) in the analysis and design of extrusion and other metal forming processes is constantly increasing. Computer models that with adequate accuracy can describe the material behavior during extrusion can be very useful for product and process development. The process development in industrial extrusion today is, to a great extent, based on trial and error. This often involves full size experiments which are expensive, time consuming and interfere with the production. It would be of great value if these experiments could be performed in a computer. In this work, FE models of the stainless steel tube extrusion process were developed and used. Simulations were carried out for different tube dimensions and three different materials: two austenitic stainless steels and one duplex (austenitic/ferritic) stainless steel. The models were validated by comparing the predicted values of extrusion force with measurements from production presses. A large number of input parameters are used in a FE analysis of extrusion. This includes boundary conditions, initial conditions and parameters that describe the mechanical and thermal properties of the material. The accuracy of the extrusion simulation depends, to a large extent, on the accuracy of these parameters. Experimental work, both in the form of material testing and production trials, was performed in order to give an accurate description of the input parameters in these extrusion models. A sensitivity analysis was performed for one of the models and the results showed that the initial billet temperature is the parameter that has the strongest impact on the extrusion force. In order to study the temperature evolution in the billet during manufacturing, the entire process chain at extrusion of stainless steel tubes was simulated using FEM. This process flow model includes sub-models of induction heating, expansion and extrusion. The work includes the use of a dislocation density-based material model for the AISI type 316L stainless steel. It is expected that this physically based model can be extrapolated to a wider range of strains, strain rates and temperatures than an empirical model, provided that the correct physical processes are described by the model and that no new phenomena occur. This is of interest for steel extrusion simulations since this process is carried out at higher strains and strain rates than what are normally used in mechanical laboratory tests. The developed models have given important contributions to the understanding of different phenomena that occur during extrusion of stainless steel tubes, and can be used to analyze how different process parameters affect the extrusion process.
|
|
| 7. |
|
|
| 8. |
- Hansson, Sofia, et al.
(författare)
-
Sensitivity analysis of a finite element model for the simulation of stainless steel tube extrusion
- 2010
-
Ingår i: Journal of Materials Processing Technology. - : Elsevier. - 0924-0136 .- 1873-4774. ; 210:10, s. 1386-1396
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, a sensitivity analysis has been performed on a finite element model of glass-lubricated extrusion of stainless steel tubes. Fifteen model parameters, including ram speed, billet and tool temperatures, friction coefficients and heat transfer coefficients, were considered. The aim of the study was to determine the parameters that are most important for the response of the extrusion force. The relationship between the model parameters and the responses was analyzed by a calculation of two different regression models: one linear polynomial model and one model that includes interaction terms. Additional simulations were then carried out to validate the regression models. The results show that the initial billet temperature is the factor that has the strongest impact on the extrusion force within the parameter ranges studied in this work. The goodness of prediction and goodness of fit are very good for both regression models.
|
|
| 9. |
- Hansson, Sofia, et al.
(författare)
-
Simulations and measurements of combined induction heating and extrusion processes
- 2010
-
Ingår i: Finite elements in analysis and design (Print). - : Elsevier. - 0168-874X .- 1872-6925. ; 46:10, s. 905-915
-
Tidskriftsartikel (refereegranskat)abstract
- The manufacturing process chain at glass-lubricated extrusion of stainless steel tubing is simulated using the finite element method. The developed model includes sub-models of induction heating, expansion and extrusion. An in-house mapping tool is used to transfer the temperature fields between the electromagnetic-thermal and thermo-mechanical analyses. Using the combined model it is possible to study the influence of different process parameters on the temperature distribution in the billet, and how this affects the final extrusion properties. In this study, the model is applied to two cases of tube extrusion, one using an austenitic stainless steel and one using a duplex, austenitic/ferritic, stainless steel. It is shown that the induction heating model successfully predicts the temperatures obtained experimentally from thermocouples placed in the steel billets during heating. The agreement between models and experiments regarding extrusion force and expansion force is satisfactory.
|
|
| 10. |
|
|
