Abstract
Abstract:
Grade 5 titanium alloy (Ti6Al4V) is the workhorse titanium alloy used in many industrial applications including aerospace, automotive, chemical and biomedical. Its attractive mechanical properties such as high strength-to-weight ratio, low density and corrosion resistance make it eminently suitable for such applications. However, its use is limited to these specialized applications due to its high cost. This high cost is mainly due to the primary processing of the material using the Kroll process. Little can be done, currently, to reduce the primary processing cost due to the high reactivity of titanium with oxygen. However, cost reduction measures can be implemented during secondary processing to make this alloy more affordable for general engineering applications. Such measures may include powder metallurgy, laser additive manufacturing, high performance machining and high speed machining.
High speed machining (HSM) has been used to improve productivity and reduce component manufacturing costs in aerospace applications such as wing sections. HSM involves machining at high cutting speeds. Such high speed cutting can be implemented under milling or turning conditions. In this investigation, high speed cutting using turning was investigated. However, high speed machining has an effect on the surface and sub-surface condition of a machined component. This may affect the service performance of a component, especially fatigue life. Surface integrity descriptors that may be influenced by machining, and which may affect component fatigue life include surface roughness, micro hardness, microstructure and residual stresses.
The cumulative effect of HSM on the fatigue behavior and life of components is largely unknown. This work aims to redress this by conducting experimental investigations supported by numerical analysis, on the effect of HSM on the fatigue performance of turned components for finish cutting conditions of Ti6Al4V.
Literature study showed that residual stresses induced during HSM have a significant influence on fatigue performance. The effect of HSM on residual stresses was therefore investigated on specimens machined on 75 mm diameter forged bar of Ti6Al4V. The specimens were...
D.Ing. (Mechanical Engineering)