Determination of the critical value of damage in a channel-die rotational compression test
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ORIGINAL RESEARCH
Determination of the critical value of damage in a channel-die rotational compression test Z. Pater 1
&
J. Tomczak 1 & T. Bulzak 1 & Ł. Wójcik 1 & P. Walczuk 1
Received: 10 April 2019 / Accepted: 30 October 2019 # The Author(s) 2019
Abstract This article describes the problems involved in modelling material cracking in skew rolling processes. The use of the popular damage criteria is impossible because of the lack of a calibration test that would make it possible to determine the critical value of material damage under conditions similar to those found in skew rolling. To fill this gap, a test called channel-die rotational compression was proposed. It consisted of rolling a disk-shaped specimen in a cavity created by two channels of cooperating tools (flat dies), which had heights smaller than the diameter of the specimen. When the rolling path was sufficiently long, a crack formed in the axial zone of the specimen. In this test, modelling using the finite element method made it possible to determine the critical values of material damage. As an illustration, the test was used to determine the critical damage value when conducting a rotational compression process on 50HS steel (1.5026) specimens formed in the temperature range of 950–1200 °C. The analysis was conducted using the Cockcroft–Latham damage criterion. Keywords Damage . Rotational compression . FEM . Experiment
Introduction Material cracking is a frequent occurrence in skew rolling. In some processes of this type, such as the Mannesmann piercing process, cracking is desirable. In others, it is unacceptable because it induces irreparable damage to the product being formed. Therefore, it is important to monitor cracking beginning at the design stage of a given manufacturing process. High hopes are being pinned on the possibilities offered by computer modelling, which is increasingly used in the analysis of skew rolling processes. The first reports on the modelling of the Mannesmann effect, which leads to the formation of a crack in the axial zone of a rolled product, were published at the beginning of the twenty-first century. Ceretti et al. [1] used Deform 2D software to model cracking (under the plane-strain assumption) in the axial zone of a part skew-rolled between flat tools. In their analysis, they adopted the theory of the maximum principal stress σ1, assuming that the critical value of this stress was * Z. Pater [email protected] 1
Lublin University of Technology, 36 Nadbystrzycka Str, 20-618 Lublin, Poland
30 MPa. When the principal stress in a given element was σ1 > 30 MPa, the element was deleted to model crack formation. This model of cracking was used by Capoferri et al. [2] in their analysis of the formation of AISI1020 steel pipes (in this case, the limit value of principal stress σ1 was assumed to be 36.5 MPa). The first attempt to model the Mannesmann piercing process under 3D deformation was made by Ceretti et al. [3]. Their analysis was carried out using the Deform 3D software and introducing several simplificat
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