Comprehensive study of the seamless tube cross-roll piercing process by means of FEM simulation
No hay miniatura disponible
Fecha
2019-03-15
Autores
Título de la revista
ISSN de la revista
Título del volumen
Editor
Universidad de Deusto
Resumen
This dissertation reports the study of the cross-roll piercing (CRP) process for the manufacturing
of seamless tubes, aiming to identify the key parameters of the process and to analyse the
development of the wall thickness eccentricity defect (WTE) and the undesired redundant
deformation in the tube, by means of the process finite element (FE) simulation.
First, a preliminary simplified FE model has been proposed for the characterisation of the most
important contact present in the process, namely, the contact between the billet and the rolls.
The viscoplastic friction model approach with regards to the relative velocity at the interface is
concluded as the most appropriate for the roll-billet contact. Then, on the basis of the simplified
model, an advanced FE simulation has been developed including all the elements of the piercing
mill. A methodology in which industrial data is used for the validation of the FE model has been
proposed. The validation is accomplished through the correlation of the power consumed by the
rolls, forces exerted by the Dieschers, process time and longitudinal shear deformation with the
experimental measures.
The analysis of the material state serves to confirm the severe action of the rolls on the material,
given that the exterior region of the material is deformed at a higher rate and presents the
highest effective strain value. Regarding the temperature distribution in the tube section, a
realistic temperature profile has been considered so as to be able to analyse the cause of the
WTE defect. The combination of an uneven temperature distribution in the billet cross section
and the bending of the plug is identified as fundamental requirement for the development of
the WTE defect. Therefore, the suppression of this defect would be possible whenever the plug
stiffness were increased enough or the temperature distribution made homogeneous. Regarding
the misalignment of the piercing mill elements, their impact on the WTE of the tube is not
significant.
Furthermore, the redundant shear deformation has been addressed. The longitudinal twisting of
the material is considered as an undesired strain that should be minimised, but the circumferential
twisting is also associated to the apparition of inside bore defects in the tube. The separation
of the Dieschers has a severe impact in the circumferential twisting of the material, whilst the
plug position modifies substantially the longitudinal redundant shear deformation.
The constitutive model used in this study has shown a good performance. However, high transient
loading and deformation conditions have been identified in this industrial process. Therefore,
a physically-based constitutive model conceived particularly for those deformation conditions
has been developed. First, this formulation has been validated in a compression test simulation,
yielding better results than the homologous phenomenological constitutive model. Then, it has
been implemented in the simulation of the CRP process, showing its validity for the simulation of
complex industrial processes in which transient deformation conditions are present.
Palabras clave
Descripción
Materias
Matemáticas
Ciencias tecnológicas
Ciencia de los ordenadores
Tecnología industrial
Tecnología de materiales
Tecnología e ingeniería mecánicas
Tecnología metalúrgica
Ciencias tecnológicas
Ciencia de los ordenadores
Tecnología industrial
Tecnología de materiales
Tecnología e ingeniería mecánicas
Tecnología metalúrgica