Recent advances in the development of aerospace materials

Titanium alloys present superior properties such as high strength-to-weight ratio and resistance to corrosion but, possess poor machinability. In this study, influence of material constitutive models and elastic–viscoplastic finite element formulation on serrated chip formation for modeling of machining Ti–6Al–4V titanium alloy is investigated. Temperature-dependent flow softening based modified material models are proposed where flow softening phenomenon, strain hardening and thermal softening effects and their interactions are coupled. Orthogonal cutting experiments have been conducted with uncoated carbide (WC/Co) and TiAlN coated carbide cutting tools. Temperature-dependent flow softening parameters are validated on a set of experimental data by using measured cutting forces and chip morphology. Finite Element simulations are validated with experimental results at two different rake angles, three different undeformed chip thickness values and two different cutting speeds. The results reveal that material flow stress and finite element formulation greatly affects not only chip formation mechanism but also forces and temperatures predicted. Chip formation process for adiabatic shearing in machining Ti–6Al–4V alloy is successfully simulated using finite element models without implementing damage models.

Modified material constitutive models for serrated chip formation simulations and experimental validation in machining of titanium alloy Ti–6Al–4V

This paper presents an overview of the recent advances in high performance cutting of aerospace alloys and composite currently used in aeroengine and aerostructure applications. Progress in cutting tool development and its effect on tool wear and surface integrity characteristics of difficult to machine materials such as nickel based alloys, titanium and composites is presented. Further, advances in cutting technologies are discussed, focusing on the role of hybrid machining processes and cooling strategies (MQL, high pressure coolant, cryogenic) on machining performance. Finally, industrial perspectives are provided in the context of machining specific components where future challenges are discussed.

High performance cutting of advanced aerospace alloys and composite materials

Titanium alloys are known as difficult-to-machine materials The problems of machining titanium are many folds which depend on types of titanium alloys This paper investigates the underlying mechanisms of basic challenges, such as variation of chip thickness, high heat stress, high pressure loads, springback, and residual stress based on the available literature These are responsible for higher tool wear and worse machined surface integrity In addition, many cutting tool materials are inapt for machining titanium alloys as those materials are chemically reactive to titanium alloys under machining conditions To address these problems, latest techniques such as application of high pressure coolant, cryogenic cooling, tap testing, thermally enhanced machining, hybrid machining, and use of high conductive cutting tool and tool holder have also been discussed and correlated It seems that all the solutions are not yet well accepted in the industrial domain; further advancement in those fields are required to reduce the machining cost of titanium alloys

Problems and solutions in machining of titanium alloys

Welding and Joining of NiTi Shape Memory Alloys: A Review

https://hal.archives-ouvertes.fr/hal-01002827/document

Machinability of titanium alloys (Ti6Al4V and Ti555.3)

Numerical cutting modeling provides understanding and prediction of chip formation process variables such as stress, temperature, cutting forces…  Thus, it could help to improve several areas related to the cutting process as cutting tool development, machining parameter set up, material development and so on However, several aspects as numerical model definition, validation of numerical results and identification of entry parameters should be improved prior to offering it as a robust and reliable tool to the industry This paper deals with workpiece material flow stress identification Several aspects are pointed out : the difficulty to validate numerical results, the influence of the material flow stress, the need to establish tolerances during parameter identification and the difficulty to properly identify by inverse simulation material flow stress coefficients

F. Le Maître

Papers

Machinability of titanium alloys (Ti6Al4V and Ti555.3)

Material Flow Stress Sensitivity Analysis in Numerical Cutting Modeling