TY - BOOK

T1 - Investigation of Ball Spinning

AU - Kuss, Mario

N1 - no embargo

PY - 2016

Y1 - 2016

N2 - To manufacture lightweight tubes, fabricators increasingly use incremental forming processes like ball spinning. The use of such processes requires a profound knowledge of material properties and process understanding. This dissertation provides an overview about ball spinning and its modifications. Also a method to calculate the forming forces analytically is presented and compared to experiments and finite element simulations. A closer look to the process points out the dependence of process parameters to the damage behaviour. A 2D finite element model is presented to predict the damage during ball spinning. The results are showing the trend to modify the process parameters for a damage minimised process design. The internal stress state of products after the forming process has also become an increasing focus. This is especially important for the prediction of lifetime under fatigue conditions of the product. The effects on kinematic and isotropic hardening of high strains has a significant influence on forming processes with reversing strain hardening like ball spinning. This investigation gives a detailed view into the deformation mechanism of a ball spinning expansion process with the finite element method. A closer look taken on to the differences between kinematic and isotropic hardening to the internal stress state after the forming process. This investigation provides a method to calibrate the combination of the strain hardening parameters on the final geometry, demonstrated by an experiment. Therefore, the final internal stress state and the lifetime prediction can be computed more precisely.

AB - To manufacture lightweight tubes, fabricators increasingly use incremental forming processes like ball spinning. The use of such processes requires a profound knowledge of material properties and process understanding. This dissertation provides an overview about ball spinning and its modifications. Also a method to calculate the forming forces analytically is presented and compared to experiments and finite element simulations. A closer look to the process points out the dependence of process parameters to the damage behaviour. A 2D finite element model is presented to predict the damage during ball spinning. The results are showing the trend to modify the process parameters for a damage minimised process design. The internal stress state of products after the forming process has also become an increasing focus. This is especially important for the prediction of lifetime under fatigue conditions of the product. The effects on kinematic and isotropic hardening of high strains has a significant influence on forming processes with reversing strain hardening like ball spinning. This investigation gives a detailed view into the deformation mechanism of a ball spinning expansion process with the finite element method. A closer look taken on to the differences between kinematic and isotropic hardening to the internal stress state after the forming process. This investigation provides a method to calibrate the combination of the strain hardening parameters on the final geometry, demonstrated by an experiment. Therefore, the final internal stress state and the lifetime prediction can be computed more precisely.

KW - Metallumformung

KW - Umformtechnik

KW - Finite Elemente Methode

KW - Inkrementelle Umformung

KW - Zylinderabstreckwalzen

KW - Kugeldrücken

KW - Eigenspannungen

KW - Kinematische und Isotrope Verfestigung

KW - Schädigung

KW - Metal Forming

KW - Ball Spinning

KW - Flow Forming

KW - Finite Element Method (FEM)

KW - Incremental Forming

KW - Tube Spinning

KW - Damage

KW - Ayada

KW - Statistical Design of Experiments (DoE)

KW - Internal Stress

KW - Kinematic and Isotropic Hardening

M3 - Doctoral Thesis

ER -