Jumping Wave Characteristic during Low Plasticity Burnishing Process

During the low plasticity burnishing process of soft materials such as carbon steel with a hardness of up to 40 HRC (Rockwell grade) a raised structure of the material known as the Jumping Wave forms in front of the tool roll. This phenomenon significantly disturbs the burnishing process, but is very poorly described in the literature. This article presents studies of this phenomenon on the example of burnished 1.0562 steel. The research concerns the changes in the surface structure of the processed material as well as changes in the structure of the material during this process. The research shows changes in the geometric structure of the surface made in the 3D system and their parametric description. Moreover, the work presents an analysis of the metallographic structure in the tool zone. The research showed occurrence of material slippages in the wave in front of the tool, which creates an additional structure on the surface. These tests make it possible to better understand the process of changes that take place in the surface layer of the processed element in the low plasticity burnishing process.

Residual Stress Regenerated on Low Plasticity Burnished Inconel 718 Surface After Initial Turning Process

Low plasticity burnishing (LPB) has been extensively employed in aero-industry to enhance fatigue performance of machined components by introducing compressive residual stress. Effects of various parameters on the residual stress field induced by low plasticity burnishing have been investigated by many researchers. However, initial residual stresses induced by machining are one of the important factors which affect the residual stress regenerated by the LPB process. The present work aims to develop an analytical model which takes into account the initial residual stress and burnishing parameters to predict residual stress field of workpiece material Inconel 718 based on Hertz contact theory and elastic–plastic theory. Initial residual stress fields were produced by turning of Inconel 718 and were measured by using X-ray diffraction technique. Two types of material constitutive models such as the linear hardening model and isotropic–kinematic model were employed to describe the elastic–plastic behavior of workpiece material Inconel 718. An analytical study was performed to analyze the effect of the initial residual stress field and burnishing parameters on residual stress induced by low plastic burnishing. The results of analytical model were verified by conducting the LPB experiments on initial turned Inconel 718. The results showed that the shape and magnitude of the residual stress field obtained with considering the effect of initial residual stress field was in good accordance with experimental measurements.

Multiparametric Optimization of Low Plasticity Burnishing Process for AISI 4340 by using Utility Concept

Low plasticity burnishing (LPB®) is an innovative method which provides deep and stable compressive residual stresses. It improves surface characteristic such as low and high cycle fatigue strength, surface finish, microhardness, wear resistance, corrosion resistance, etc. The objective of the multi parametric process optimization for LPB is to find out appropriate levels of process variables i.e. ball diameter, pressure, speed, initial surface roughness and number of passes for achieving optimum values of surface roughness, hardness and fatigue life simultaneously. Considering multiple output responses in the present study, multi response optimization is essential. This paper deals with multi objective LPB process optimization problem of response characteristics with Utility concept for AISI 4340 steel alloy