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)

Comparison of the machinabilities of Ti6Al4V and TIMETAL® 54M using uncoated WC–Co tools

Surgical procedures that affect the human body's bone structure, often entail cutting, drilling or screwing operations of bone. The post-operative success of these procedures is largely dependent on the degree of damage introduced by the process. In this article, the influence of the rotational velocity, feed per tooth and two drill bit type on workpiece temperatures and cutting forces when drilling bovine cortical bone has been studied. The purpose is to find the optimum cutting conditions that will generate the lower temperatures and cutting forces. The measurement of temperatures has been carried out with an infrared thermography camera, and a piezoelectric dynamometer has been employed to obtain forces. A model has been developed from which heat flow into the drilled bone can be estimated from specific cutting force and the fraction of total heat generated that flows into the bone. This fraction has been shown to depend on the Peclet number for the process, proportional to the drill rotation speed, th...

Effects of rotational speed, feed rate and tool type on temperatures and cutting forces when drilling bovine cortical bone

Effect of heat treatment conditions on the machinability of Ti64 and Ti54M alloys

Surgical procedures that affect the human bone structure often entail drilling operations of bone. The post-operative evolution of these interventions is conditioned largely by the damage generated during the operation. The aim of this study was to determine clearly the influence of the cutting conditions on temperatures and forces when drilling bovine cortical bone, in the interests of further optimization of cutting conditions to minimize the generated damage. The infrared thermography technique and a piezoelectric dynamometer were employed as measurement devices. It was observed that the main parameter affecting temperatures was the feed per tooth. The temperatures obtained were lower when drilling with high feed per tooth, even though an opposite effect was noticed on the feed force and torque, with an increase of them. From the experimental results, prediction models of temperature rise, feed force and cutting torque were created, in order to predict the response based on the selected cutting conditions.

L.-M. Iriarte

Papers

Machinability of titanium alloys (Ti6Al4V and Ti555.3)

Comparison of the machinabilities of Ti6Al4V and TIMETAL® 54M using uncoated WC–Co tools

Effects of rotational speed, feed rate and tool type on temperatures and cutting forces when drilling bovine cortical bone

Effect of heat treatment conditions on the machinability of Ti64 and Ti54M alloys

Effects of rotational speed and feed rate on temperature rise, feed force and cutting torque when drilling bovine cortical bone