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Symulacje numeryczne procesu obciskania obrotowego wielostopniowego wałka drążonego

100%

Tomczak J. , Pater Z.

tom nr 2

37-41

W artykule przedstawiono wyniki analizy numerycznej nowatorskiego procesu obciskania obrotowego wielostopniowego wałka drążonego. Symulacje numeryczne procesu wykonano metodą elementów skończonych w warunkach przestrzennego stanu odkształcenia z uwzględnieniem zjawisk termicznych. Podczas obliczeń określono parametry geometryczne otrzymanych wyrobów, wyznaczono rozkłady naprężeń, odkształceń, temperatur oraz momentów kształtowania. Omówiono modele geometryczne zastosowane w symulacjach MES. W wyniku badań stwierdzono możliwość kształtowania osiowosymetrycznych odkuwek drążonych metodą obciskania narzędziami obrotowymi.

Results of numerical analysis of a novel multistage process of rotational compression of hollow shaft were presented. Numerical simulations of the process were carried out with the use of finite element method in terms of spatial state of strain, taking into account thermal phenomena. During the calculations, geomet-ric parameters of derived products were evaluated, as well as distributions of stress, strain, temperature and forming moments. Geometric models used in the FEM simulations were discussed. The research revealed the possibility of forming axially-symmetrical forgings hollowed out by the method of rotational compression.

Numerical and experimental research on cross wedge rolling hollow shafts with a variable inner diameter

84%

Shen J. , Wang B. , Zhou X. , Li J.

tom Vol. 19, no. 4

1497--1510

The precise forming of inner hole has been a major technical difficulty in the cross wedge rolling (CWR) of hollow shaft. This paper proposes a new process to form hollow shafts with variable inner diameters by using the CWR with mandrel control. The forming characteristics and dimension precision of this process are analyzed by combining finite element modelling (FEM) and forming trials. The hole step of hollow shaft with variable inner diameter is formed in a spiral pattern. The helixes result in many micro-steps in hole step when forming the right-angle inner step. The metal flow lines demonstrated that mandrel step hindered the axial metal flow of inner hole and the metals were accumulated in hole step. The rolling load increases in the process of forming hole step. The mandrel is subjected to axial load when hole contacts the mandrel step. The roundness can be improved by reducing the mandrel diameter in knifing position. The axial accuracy of inner diameter can be classed as three parts: hole expansion, stable rolling, hole shrinkage. The compensated mandrel was designed to improve axial precision of inner diameter. The results showed that the inner hole dimension can be effectively controlled.

Numerical and experimental study on the inner diameter uniformity of hollow shafts in cross-wedge rolling with mandrel

84%

Zhou J. , Shen J. , Wang B. , Huang X. , Guo W.

tom Vol. 21, no. 3

321--336

The precision forming of inner hole is one of technological bottlenecks in Cross-wedge Rolling (CWR) of hollow shaft with mandrel. The inner diameters show signs of characteristic fluctuation despite under the control of mandrel. The uniformity of inner diameter was investigated by finite element simulation and experiments in this study. The inner hole expands at the knifing stage and shrinks at the sizing stage. The dimensional fluctuation of inner diameter is mainly resulting from the improper metal flow. The radial and axial metal flows are insufficient at the knifing stage, which resulting in the hole expansion at knifing zone. The hole shrinkage is caused by the relatively adequate radial metal flow at sizing stage. The experiment results show that the hole expansion increases with the increasing stretching angle and mandrel diameter and decreases with the increasing forming angle and initial wall thickness. The hole expansion first increases and then decreases with the increasing reduction ratio. The hole shrinkage has positive correlations with forming angle, reduction ratio and initial wall thickness, and negatively correlates with stretching angle and relative mandrel diameter. A modified CWR roll with the curved-surface knife is proposed to get rid of the hole expansion. Based on experiments and simulations, the most suitable geometric parameters of the curved-surface knife are determined. Using mandrel diameter compensation can reduce the phenomenon of hole shrinkage. These methods were applied to the trial rolling of a half-shaft sleeve part, and the results show that the methods significantly restrain the inner diameter fluctuation.