F 2018134085 Abdullah Shebih RESEARCH ARTICLE REVIEW 1 TITANIUM ALLOY MACHINING TOOL LIFE WITH RESPECT TO PRESSURE COOLANT Research by: Rosemar B.da Silva Federal University of Uberlândia, Faculty of Mechanical Engineering, Uberlândia, MG, Brazil. The primary objective of this study was to investigate the behavior of Polycrystalline Diamond (PCD) tools when machining Ti–6Al–4V titanium alloy at high speed conditions using high pressure coolant supplies. Tool performance under different conditions and the dominant wear mechanisms were investigated. Increase in coolant pressure tends to improve tool life and reduce the adhesion tendency, accelerated by the susceptibility of titanium alloy to gall during machining. Adhesion and attrition were observed to be the dominant wear mechanisms when machining at the cutting conditions, which was investigated in this research. Titanium alloys are utilized in many aerospace applications due to a combination of properties such as high strength at elevated temperatures and relatively low density hence used in air crafts meant for high altitude like SR 71 Blackbird. These materials are problematic to machine and are therefore referred to as difficult-to-cut. Several studies have been conducted to improve the machinability of titanium alloys generally covering the usage of new tool materials, tool geometry, cutting conditions and cutting fluids The principal focus of this study is to reduce the shear stress at the secondary shear zone, consequently lowering the heat generated and tool wear during machining. One way of achieving this is to create a thin stable interfacial layer with low shear strength between the chip and tool by coating the tool, using coating techniques such as physical vapor deposition (PVD) or F 2018134085 Abdullah Shebih chemical vapor deposition (CVD). These studies have not produced any credible results mainly because of the chemical elements applied as coatings. Most of them are based on titanium and aluminum which have high chemical affinity with the titanium alloy work piece. Another way is to use cutting fluids. Normally access of cutting fluids into the sliding zone reduces the friction coefficient and heat generation. However, when machining titanium alloys, problems still remain, as the access of cutting fluid to the cutting interfaces cannot be maintained due to the instability of the interfacial layer. In this study, PCD tools were evaluated in finish turning of Ti–6Al–4V alloy at high speed machining conditions. Emulsion based cutting fluid at 6% concentration was applied at conventional low pressure flow rate from the overhead direction (Fig. 1A) and at higher pressures (7, 11 and 20.3 MPa) directed against the chip flow direction on the tool rake face (direction B of Fig. 1) in order to study the behavior of the tribological system at these conditions. Fig 1A The machining trials were carried out on a CNC lathe, with an 11 kW motor drive with a maximum torque of 1411 Nm. The spindle rotation speed ranges from 18 to 1800 rpm. The high pressure coolant delivery system has a power of 30 HP, a maximum flow rate of 93.6 L/min and maximum pressure of 21 MPa. The cutting fluid is a high lubricity emulsion. Fig. 2 below shows recorded tool life when machining titanium-base alloy with PCD inserts at various cutting speeds under conventional coolant flow and at high pressure coolant supplies of 7, 11 and 20.3 MPa. Flank and nose wear are typical wear patterns observed when machining Ti–6Al–4V alloy with PCD tools. Flank wear rate is generally lower than the nose wear rate hence nose wear was the dominant failure mode in all the cutting conditions investigated in this study. Nose wear rate increased with increasing cutting speed and with prolonged machining using all the coolant supplies investigated. Tool life generally decreased with increasing cutting speed when machining with both conventional and high pressure coolant supplies. this relation F 2018134085 Abdullah Shebih between cutting speed and tool life is due to the reduction in the tool-chip contact length and the consequent increase in temperature, as well as increase in both normal and shear stresses at the tool tip/cutting region. Fig 2 After many test with PCD and different coolant pressure trials the author can say that the best results were encountered with the highest (20.3 MPa) coolant pressure at lower speed conditions. There is no significant difference in tool performance when machining at higher speed conditions. Flank (and nose) wear are the dominant failure modes when machining the titanium, Ti–6Al–4V, alloy with PCD inserts using conventional and high pressure coolant supplies. Adhesion and attrition are dominant wear mechanisms at the cutting conditions investigated. Substantial improvement in tool life ranging from 9 to 21 folds, can be obtained when machining Ti–6Al–4V alloy with PCD tools with high pressure coolant supplies relative to conventional coolant supply. It also came to knowledge by the end of this research that segmented chips were generated when machining with high pressure coolant supply, while long continuous chips were generated when machining with conventional coolant flow. F 2018134085 Abdullah Shebih ARTICLE REVIEW 2 COOLANT EFFECT ON MACHINING Li of K.S lee Department of Mechancial and Production Engineering, National University of Singapore This article was written for machining measure in which the machining of hard metallic workpieces leads to the tool life decreasing. The use of coolant during any machining activity is known to decrease tool wear. So writer further clarifies the article that in an ordinary machining activity, the tool cuts material from the workpiece through direct contact. The utilization of coolant during a machining activity is accepted to decrease tool wear and during the cutting the coolant liquid makes it easier for the tool to cut and faster too. The article further shows how heat is produced. The cause of heat is the work done on the work piece. Expulsion of high temperature from the machining process is fundamental on the grounds that at high temperatures, the tool encounters a decrease in hardness and wear obstruction. The materials and machines utilized in the trial were done on a Colchester Mascot 1600 machine. The workpiece materials used were ASSAB 705and ASSAB 760 steel. The coolant utilized was a Swiss made water-dissolvable foamy lubricant cutting coolant called Blasocut 2000 Universal and was provided by a 3-hp siphon to the instrument through a spout of 8 mm breadth, at a flowrate of 2.5 - 3.0 I/min. Cutting fluid applied from overhead tends to boil and vaporize on contact with the high temperatures at the primary shear zone. This phenomenon did hinder access of fresh coolant to the cutting interfaces. This constitutes a negative behavior from heat transfer standpoint. However, cutting fluid applied at high pressures can minimize or completely eliminate this negative effect by accessing very close to the cutting edge to provide a better cooling effect. The lowest tool life was recorded with conventional overhead coolant application. Over 20 fold improvement in tool life was achieved during machining. In the end we can come to a conclusion of this research that The use of coolant doesn't really decrease apparatus wear as much as we expect it too. Under certain conditions, particularly those under which this researcher did the trials, the utilization of coolant obviously stops tool wear. Further exploration is expected to additionally affirm under what conditions will the utilization of coolant be helpful to the machining cycle and how the temperature dispersion during machining on workpiece is can be achieved fully. F 2018134085 Abdullah Shebih ARTICLE REVIEW 3 CRYOGENIC MACHINING OF HARD MATERIALS Ganesh B.Narkhede1, Assistant Professor and Mechanical Department and AISSMS College of Engineering, Pune This research explores the effect of cryogenic coolant in machining of hard from an industrial perspective with emphasis on higher productivity, greater tool life and reliable performance characteristics, as the author of this research states that with fast growing industry advancement it is hard to compete with machine industries and keep pace with them so steps need to be taken to maximize output and decrease losses. Hence this research was an attempt to analyze the tool wear by controlling the variable parameters such as speed, feed and depth of cut. The combined effects of these parameters on tool wear were observed. In cryogenic machining process a modest amount jet of liquid nitrogen is injected onto the rake face of cutting tool during the cutting process. After machining, investigation of tool wear, surface finish and cutting forces are observed. The author states that the coolants help minimize the stresses and carry away chips produced during the material removal process. Mostly, oils are used as coolants in wet turning and they have low ignition or flash point characteristics to minimize fire hazards. Author states that use of oil based cooling lubricants causes the health problems for workers doing or handling the machining process. Hence according to the researcher therefore it is important to introduce a new technology which is environmentally viable and also carries the pros of conventional coolants. Many problems that arise during machining are result of the heat generation and high temperatures associated with it. The article states that increase in cutting forces, more than expected tool wear, poor surface finish and poor dimensional stability, etc. are known to be temperature dependent side effects. These drawbacks that are stated can be eliminated in cryogenic machining by using liquid nitrogen as coolant where maximum heat is carried away from the cutting zone where the heat is generated. The temperature of liquid nitrogen used is around -150o C F 2018134085 Abdullah Shebih THE THREE COMPONENTS OF CUTTING FORCES(THE THREE COMPONENTS OF CUTTING FORCES The author uses amplifier and computer setup for measuring force components F 2018134085 Abdullah Shebih And below is the setup the author uses to conduct the test which includes the cryogenic insert nozzle The author also stated that he used a dynamometer which is a device used to measure force, moment of force and power produced during actual cutting operation. Various types of dynamometers are available ; In this study Kistler dynamometer 9257B is being used. A comparison between cryogenic and dry turning is shown below by the researcher with respect to cutting force FX F 2018134085 Abdullah Shebih And the graph below shows with respect to feed force FY This graph showed the behavior of feed force of FY in dry and cryogenic turning, the overall reduction in the feed force is shown as 61%. Also we see below graph comparing the temperatures With the data above all provided from the research the conclusion I come to is that cryogenic machining can be presented and used as a viable and sustainable machining technology in comparison to older conventional machining. By seeing numbers of cryogenic and dry turning F 2018134085 Abdullah Shebih trials, it is proved that transitioning from oil based CLFs to LN used in cryogenic machining is a positive move towards more sustainable machining, which not only results in a significant reduction in solid waste but also water usage, global warming potential, acidification etc. Hence based on this comparative analysis, it is proved that cryogenic machining can be more energy efficient than older conventional methods for machining.
