Numerical contribution to segmented chip effect on residual stress distribution in orthogonal cutting of Inconel718

Yang Liu,Jinming Zhou,Aylin Ahadi,Mathias Agmell,Dongdong Xu,Jan-Eric Stahl

doi:10.1007/s00170-020-05702-2

Abstract

Segmented chip morphology has a significant influence on distribution of residual stress and surface topography on machined surface in machining difficult-to-cut materials. In this paper, Coupled Eulerian and Lagrangian (CEL) model is employed to investigate the effect of segmented chip on surface integrity (residual stress distribution and surface topography) in orthogonal machining of Inconel718 with uncoated carbide inserts. A mesh sensitivity study of chip morphology and residual stress distribution is performed by developing the following three different grid resolutions: coarse (mesh size 35 μm), medium (10 μm) and fine (5 μm). Comparing with the experimental results, it is clear that the numerical model presents reasonable results, including the chip morphology, temperature distribution, cutting forces, residual stress profile and surface fluctuation period. As for the generated surface integrity, a waved surface and cyclic residual stress distribution are found with the segmented chip due to the periodical mechanical and thermal loadings acting on the machined surface. Furthermore, the formation of single chip segment is investigated in-depth to explain the residual stress distribution generation.

Highlights

Nickel-based superalloy (e.g. Inconel718) is widely used for safety critical components manufacturing due to its high strength, corrosion resistance, weldability and long-term stability at elevated temperature
The chip morphology obtained from the experiment shows an evident segmented structure (Fig. 3a) and can be characterized with four parameters [21], the maximum tooth height, the minimum tooth height, the tooth width (e2) and the chip segmentation frequency, which is determined according to Eq (9), where λh is the chip compression ratio which can be approximately determined by a hyperbolic function λh=1.291 + 0.021/h1
It is obvious that the chip morphology is profoundly influenced by element size (Fig. 3b–d) that the chip is continuous and highly rough with the coarse mesh while the presence of shear bands is noticed with the medium mesh

Summary

Introduction

Nickel-based superalloy (e.g. Inconel718) is widely used for safety critical components manufacturing (e.g. jet engine and highspeed airframe parts) due to its high strength, corrosion resistance, weldability and long-term stability at elevated temperature. These excellent properties for applications have made it difficult to machine this group of materials. The high distorted element reaching the damage criterion will be deleted during the simulation, resulting in the absence of higher value of temperature, stress and strain material, to reduce the accuracy of the results [11].

Methods

Results

Conclusion