Titanium alloys are used in aerospace industry owing to their high strength to weight ratio. These alloys are considered to be difficult to machine due to their rigidity and poor thermal conductivity. High-pressure jet-assisted machining of titanium alloys is beneficial. It not only increases production efficiency, by increasing the cutting speed and lowering temperature both in cutting zone and the cutting tool, but also improves chip control, and increases tool life. It also produces better surface integrity and compress residual stress, which improves the properties of work metals such as fatigue. In order to compare the effect of high-pressure jet-assisted machining on the work pieces of Ti-6Al-4V alloy, the depth profile of residual stress was measured using xray diffraction. As comparison, the depth profile of residual stress was also measured for the conventional machined work pieces. It was found that the residual stress was a function of machining parameters, such as cutting speed, feeding force and depth of cut and particularly the high-pressure jet increases the amount of residual compressional stresses in both cutting and feed direction. In the present paper, Ti6A14V rod was machined by turning in two different manners, finishing and roughing. Tests were conducted on a lathe using different cooling systems, high pressure and conventional. To illustrate the effect of high-pressure jet assisted machining on the properties of the work piece of Ti-6-Al-4V and the depth profile of its residual stress, X -ray defractometer was used. The maximal amplitude of residual stress, at both the longitude (feeding direction) and transversal (cutting) directions, the depth of compress residual stress and the depth of the total residual stress will be present as the function of the machining parameters.

Titanium alloys are widely used in aerospace industry but also in other industry sectors. Details for compressors used for generation and petrochemical plants and medical devices can be mentioned as a few examples. Plastic deformation during forming of the metals introduces residual stresses. Fatigue, creep and corrosion are typical failure mechanisms that are stopped or accelerated in the presence of tensile residual stress. Metal cutting as a manufacturing method generates residual stresses in the surface layer. The stress state in the near-surface zone of components is of special interest as the surface often suffers loads and consequently the cracks initiate and begin to grow at that location. The scope of this thesis is to investigate the properties of the machined surface with regards to measurement of residual stresses. The results achieved by X-ray diffractometry were compared with the results using a simulating method with the same cutting data for checking the accuracy of these two methods. This review highlighted the residual stress character and how they can be measured by X-ray diffractometry in two different directions, the transversal, the cutting direction, and longitudinal, the feed direction. For measurement of residual stress under the surface, the material was removed by an electro-chemical polishing method for not introducing more stress. The same procedure was checked using Finite Element simulations. The results obtained from the investigation clarified that: The residual stress measurement by X-rays was quite accurate in comparison with finite element simulation on the surface generated by turning on titanium alloy. There were compressive residual stresses in the cutting and feed directions of the cut. Residual stress is beneficial for delay of crack propagation. High-pressure cooling produced and increased compressional residual stresses.

Titanium alloys are used in aerospace industry owing to their high strength to weight ratio. These alloys are considered to be difficult to machine due to their rigidity and poor thermal conductivity. High-pressure jet-assisted machining of titanium alloys is beneficial. It not only increases production efficiency, by increasing the cutting speed and lowering temperature both in cutting zone and the cutting tool, but also improves chip control and increases tool life. It also produces better surface integrity and compress residual stress, which improves the properties of work-piece. Ti-6Al-4V (Ti-64) rod was machined by turning in two different manners, finishing and roughing. Tests were conducted on a lathe using the same cutting data and different cooling systems, high pressure and conventional. In order to illustrate the effect of high-pressure jet-assisted machining on the properties of the work-piece of Ti-6Al-4V and its residual stress, x-ray defractometery was used. The present study revealed that there were compressive residual stresses in the transversal and longitudinal directions of the cut and the residual stresses in both directions were nearly of the same magnitude. The depth profile of residual stress was measured as well after removing the material by etching. The shear stress was very low, almost negligible. High pressure cooling affected residual stresses in finishing more than in roughing.

Residual stresses from the machining process can cause severe failure due to fatigue and stress corrosion. The depth profile of residual stress was measured for high-pressure water-jet assisted machining of Ti-6Al-4V alloy using x-ray diffraction. As comparison, the depth profile of residual stress was also measured for the conventional machined work-piece. The finite element simulation, using the updated Lagrangian formulation was also used to study the dynamic transient process. It was found that the residual stress was a function of machining parameters, such as cutting speed, feed force, depth of cut and particularly the high-pressure jet increases the amount of residual compression stresses in both cutting and feed directions. It is shown that the high-pressure water-jet assisted machining of titanium alloys is beneficial. It reduces shear forces in the secondary cutting zone along the tool/chip interface, reduces the cutting force and introduces compressive residual stress in the finished work-piece.

The purpose of this literature review is to study the basics of metal cutting and investigate how a high-pressure water jet can facilitate the cutting process. The aim of this literature study is to give a summary of books , papers and reports which were searched by the key words to build up the basic for research planning to investigate the effects on the cutting zone and surface properties when applying "Jet Break" in turning of titanium and stainless steels for the aerospace industry, in comparison when using conventional coolant.