Adjusting the Residual Stress State in Wire Drawing Products via In-Process Modification of Tool Geometries.

Markus Baumann,René Selbmann,Matthias Milbrandt,Verena Kräusel,Markus Bergmann

doi:10.3390/ma14092157

Abstract

After conventional forming processes, the residual stress distribution in wires is frequently unfavorable for subsequent processes, such as bending operations. High tensile residual stresses typically occur near the wire surface and normally limit further processability of the material. Additional heat treatment operations or shot peening are often used to influence the residual stress distribution in the material after conventional manufacturing, which is time- and energy-consuming. This paper presents an approach for influencing the residual stress distribution by modifying the forming process, especially regarding die geometry. The aim is to reduce the resulting tensile stress levels near the surface. Specific forming elements are integrated into the dies to achieve this residual stress reduction. These modifications in the forming zone have a significant influence on process properties, such as plastic strain and deformation direction, but typically do not influence product geometry. This paper describes the theoretical approach and model setup, the FE simulation, and the results of the experimental tests. The characterization of the residual stress states in the specimen was carried out through X-ray diffraction using the sin2Ψ method.

Highlights

The main production processes for elongated components comprise impact extrusion and drawing methods
Compared with the extrusion same die geometries no increase in the strain is achieved with the concave with the same diewith geometries
[22], no increase [22], in the plastic strain is plastic achieved with the same dieThe geometries noover increase in the strain is the achieved wit elementelement due to the drawing force

Summary

Introduction

The main production processes for elongated components comprise impact extrusion and drawing methods. One difference between these processes lies in the point of force application. In the forming zone, a combination of tensile and compressive stresses occurs. Wire forming with tensile force application is mostly used for smaller dimensions and smaller cross-sectional changes. Residual stresses occur in the material due to the elastic-plastic material behavior after removing all external forces. These stresses influence the subsequent forming operations of the semi-finished products and the mechanical application behavior of, e.g., the wire and semi-finished products [1]. The arrow indicates the movement direction of the semi-finished product with the drawing speed and concurrent impact of the drawing force

Methods

Results

Discussion

Conclusion