Thermal Effects on Surface and Subsurface Modifications in Laser-Combined Deep Rolling

Robert Zmich,Daniel Meyer

doi:10.3390/jmmp5020055

Abstract

Knowledge of the relationships between thermomechanical process loads and the resulting modifications in the surface layer enables targeted adjustments of the required surface integrity independent of the manufacturing process. In various processes with thermomechanical impact, thermal and mechanical loads act simultaneously and affect each other. Thus, the effects on the modifications are interdependent. To gain a better understanding of the interactions of the two loads, it is necessary to vary thermal and mechanical loads independently. A new process of laser-combined deep rolling can fulfil exactly this requirement. The presented findings demonstrate that thermal loads can support the generation of residual compressive stresses to a certain extent. If the thermal loads are increased further, this has a negative effect on the surface layer and the residual stresses are shifted in the direction of tension. The results show the optimum range of thermal loads to further increase the compressive residual stresses in the surface layer and allow to gain a better understanding of the interactions between thermal and mechanical loads.

Highlights

It is well known that during thermomechanical processes, a wide range of surface modifications result and affect the surface integrity [1]
The roughness (Ra and Rz) achieved at different temperatures and deep rolling forces are shown in Figure 2, which can be found in Supplementary Material Roughness Data
Consideration of may the roughness may indicate that the main influence

Summary

Introduction

It is well known that during thermomechanical processes, a wide range of surface modifications result and affect the surface integrity [1]. In order to make a prediction concerning the functional properties of a workpiece, it is necessary to understand the relationships between the loads and the resulting material modifications. The loads can occur individually and in combination [2]. These relationships can be determined via changes in state variables and described in models. It should be possible to adjust the required surface integrity by a targeted selection of the manufacturing process and its process parameters. This solution to the inverse problem is gaining more and more attention in both, academics and industry. The innovative approach of the so-called Process Signatures should make it possible to draw conclusions about the resulting modifications independently of the manufacturing process and only by means of internal material loads prevailing in the workpiece [3,4]

Methods

Results

Conclusion