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2 Journal of Achievements in Materials and Manufacturing Engineering

2 2015

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FEM model of induction hardening of gear of mixture material

100%

Hodek J. , Shykula P.

2015

tom Vol. 71, nr 2

87--92

Purpose: The purpose of this article is to describe the construction of an FEM model for computing residual stresses generated by induction hardening of a high-carbon steel gear. Design/methodology/approach: The 3D FEM model comprised two parts. The first one which dealt with induction heating was prepared using MSC Marc commercial software. The second one, a model of temperature and deformation fields, was developed with the aid of DEFORM 3D commercial software. Material data was considered to be temperature-dependent. In the second part of the model, the material data was defined on the mixture basis: a separate temperature-dependent data set was specified for each phase, including transformation rules. The data was obtained in part by measuring and in part by calculation using JMatPro commercial software. Temperatures during heating and cooling were measured by means of thermocouples. The convection heat transfer coefficient was determined and the model of induction heating validated using the measured data. The thickness of the martensitic layer upon heat treatment was measured to validate the model. Findings: The 3D FEM model described here predicts the temperature distribution during heat treatment and the thickness of the martensitic layear upon heat treatment accurately. It was thus deduced that this material model was defined correctly and that the calculation of residual stresses would correspond to the reality. Practical implications: Future work should focus on refining the model, e.g. on incorporating transformation plasticity and on analysing the relationship between the residual stress distribution upon heat treatment and the part’s fatigue. Originality/value: The material model described in this article takes into account phase transformations which have a substantial impact on the post-treatment distribution of residual stresses. The 3D FEM model with this type of definition of material provides good predictions of residual stress distribution in the gear.

Continuous extrusion of commercially pure titanium GRADE 4

70%

Palan J. , Taboada J. V. , Kubina T. , Malecek L. , Hodek J.

tom Vol. 69, nr 1

33--37

Purpose: Continuous extrusion of metals using Conform™ machine is used to introduce severe plastic deformation and to improve mechanical properties of metals by reducing their grain size. This paper describes a development of a continuous extrusion sequence for Ti grade 4 in the CONFORM 315i machine. Design/methodology/approach: The influence of material flow conditions on the surface quality of final extruded rods was analyzed with the FEM-based DEFORMTM software. Findings: During the development, several process parameters were varied, such as the die chamber temperature and the extrusion velocity. Research limitations/implications: The goal was to conduct the experiment at the lowest possible temperature in order to achieve a maximum strain hardening effect. The material’s mechanical properties and its flow through the die chamber were studied. The homogeneity of the material flow and the surface quality of final rods were then optimized. Originality/value: The effort led to improvements in the analytical model used in the FEM simulation so that the surface quality can now be optimized more efficiently.