Materials Science Forum Vols. 830-831

Abstract: Particle Reinforced Metal Matrix Composites (PRMMC's) have proved to be extremely difficult to machine using conventional manufacturing processes due to heavy tool wear caused by the presence of the hard reinforcement. This paper presents details and results of an investigation into the machinability of SiC particle reinforced aluminium matrix composites using Abrasive Water Jet Machining (AWJM). Al-SiC MMC specimens, prepared with stir casting method. The surface roughness of the composite material for these different compositions are examined and compared. The influence of the ceramic particle reinforcement on the machining process was analyzed.

Abstract: The prime rationale for designers to choose titanium in their designs for aerospace applications is its relative low weight for a given strength level and its relative resistance to high temperature. Excellent biocompatibility makes titanium as ideal material for many biomedical applications. Even though the titanium products are either sintered or cast into required shape, there is a need for machining in order to produce intricate shapes. However machining of titanium alloys poses many serious problems owing to the reactivity of titanium at high cutting temperatures and rapid tool wear. An alternative method to overcome this is by reducing the cutting zone temperature. This can be achieved by the addition of solid lubricants to regular cutting liquids and using it as minimum quantity lubrication (MQL) strategy. In this study, hexagonal boron nitride (hBN) powder with different concentrations (5, 10, 15 wt %) was mixed with water and used as a lubricant. Turning experiments were performed with TiAlN coated Tungsten carbide insert for a constant speed and variable feed rates. For comparison purpose, machining was carried out under dry conditions. Results indicate that the cutting zone temperature reduced drastically on addition of solid lubricant hBN with water. MQL conditions showed that cutting zone temperature decreased by several folds when compared to dry machining. However there was no significant decrease in temperature between 10 and 15 wt% hBN additions which indicates that 10% hBN addition proves to be optimal. This type of machining thereby paves way for sustainable manufacturing.

Abstract: The Al-Si alloy is a structural material which generally consists of two or more particulates. However, Al-Si alloys are the most common alloys and commercially available ones due to their economical production. The utilization of Al-Si alloys has given the scope of study to improve in its properties using some grain refiner like Al-5Ti-1B, Al-3B and modifiers like Al-10Sr. The Al alloys were selected based on the economical uses and also, on the basis such that hypoeutectic (i.e., LM-25), eutectic (i.e., LM-6) and hypereutectic (i.e., LM-30). This project aimed to synthesize Al alloys (LM-6, LM-25 and LM-30) by melt stirring method with varying amount of grain refiners and / or modifier. The Prepared composites were characterized for machining properties. Alloys were evaluated for their machining properties which include surface roughness, lathe and drill tool dynamometer and comparing the machining properties with the minor addition of grain refienrs and/or modifier. The study concluded that, the addition of Al-3B to eutectic (i.e., LM-6) alloys has better surface finish.

Abstract: In the olden days the motto was "I designed it; you build it!" Design engineers worked alone and Designs were then thrown over the wall leaving manufacturing people with the dilemma how to manufacture. Often this delayed both the product launch and the time to ramp up to full production. In the new good days manufacturability can be assured by developing products in multi-functional teams with early and active participation from Manufacturing, Marketing (and even customers), Finance, Industrial Designers, Quality, Service, Purchasing, Vendors and factory works. The need for a holistic approach between design and manufacturing is required. The two concepts Design for Manufacturing & Design for Assembly has become the need of the hour. The heart of any design for manufacturing system is a group of design principles or guidelines that are structured to help the designer reduce the cost and difficulty of manufacturing an item.Realisation of Cryogenic thrust chamber includes various manufacturing processes like Forming, Welding, Machining and Brazing. During initial stages of Thrust chamber realisation problems like Forming of 1.7m long nozzle divergent from thin sheets, welding of various intricate geometries & assembly of critical parts were observed. Subsequently these problems were studied based on the holistic approach of Design for manufacturing & design for assembly. Improvements based on the above study were considered in design & critical processes modifications resulting in successful and timely realization of the thrust chamber.

Abstract: The form, shape and dimensions of the scaled down winglet model become small and thin bringing complexity to manufacturing. The trailing edge tapers to a thickness varying from 0.065mm to 0.099mm along its length. The mounting portion of the winglet is provided with a close tolerance having a slot gap of 5mm and a depth of 35 mm with an angle. Additionally, wind tunnel models require good surface finish on the aerodynamic surfaces and this involves adopting a manufacturing strategy with a control over on the metal cutting parameters to be implemented on a three axes CNC machining centre. The winglet surface is divided into segments in order to handle the cutting forces on the varying aerodynamic cross section. Various metal cutting parameters such as tool path, cutter diameter, feed rate, depth of cut, spindle speed, etc., are evaluated by monitoring segments where the metal cutting is carried out [1] and flow of chips observed. Fixtures and lugs are planned effectively to accommodate the machining of the angular slot in a three axes machining centre itself. Routing of operations to handle the varying thin sections and realisation of the close tolerance slot has enabled a reliable manufacturing approach in an economical way.

Abstract: In the present paper, a two dimensional numerical model has been developed using the finite element method (FEM) for predicting the material removal mechanism in micro EDM process in single spark with the assistance of magnetic field. The work piece material selected for the present study is grade 5 titanium material. The model developed by not considering magnetic field, first calculates the temperature distribution in the work piece material using the commercial software ANSYS. The crater shape is developed using the simulated temperature profiles to estimate the volume of material removed in a single spark, by considering the melting point and vaporization temperature. The model has been validated by comparing the theoretical MRR with the experimental results which is already established. The use of magnetic field which can provide an additional Lorentz force in the melt pool could aid in ejection of material from the discharge crater, thereby improving MRR. This concept is established through the coupling of magnetic and structural fields.

Abstract: This paper presents a study on minimum quantity lubrication wherein the metal working fluid is injected individually at multiple points in cutting zone, namely, rake face, back of chip and at flank face. A special attachment is developed for injecting aerosol at all possible combinations of one, two, or three forgoing points of injection. A case study on machining of Ti-6Al-4V showing effect of injection schemes on cutting force and surface roughness is presented. Comparison of multi-point injection with dry and flood cooling indicates reduction in cutting force and surface roughness while using different combinations of fluid injection.

Abstract: In present scenario most of airframe components employ aluminum alloy materials having wall thickness of 1.2 to 3mm. With advancement of manufacturing techniques such as high speed machining, it is possible to machine components with wall/floor thickness up to 0.3 to 0.5 mm with high aspect ratio. The aim of making such parts is to reduce weight of payload. The machining of monolithic structure involves removing of material up to 95% from the raw material. The objective of the study is to achieve maximum material removal rate without compromise on geometry, dimensional accuracy while machining the part. This paper proposes a working methodology for high speed machining which includes efficient process planning, based on static and dynamic analysis. This paper provides insight knowledge of selection of cutting tool, fixture design, clamping method, cutting process parameters; machine tool and computer aided manufacturing (CAM) strategy, optimum stock for minimal bending and distortion. This technology has been demonstrated in hexagonal test specimen of 0.5 mm thin wall and also proven on the indigenous developed global positioning system (GPS) components.

Abstract: Quality control is important aspect of manufacturing process. The quality of product in injection moulding is influenced by injection moulding process parameter. A study of the influence of process parameters on the injection moulding process is presented. Statistically based model approach were studied. In this the process parameter that affect the injection moulding process are like injection time, injection pressure, packing pressure, packing time, cooling time, coolant temperature mold temperature, melt temperature are studied and compared. This paper deals with design of experiment approach to fine out optimal parameter setting. The comparison shows effect of parameters on injection moulding process.Key words: Plastic injection moulding, Orthogonal array, Cycle time

Abstract: Titanium alloys are widely used in aerospace industry in the areas of pressure vessels, airframe structures, landing gears, aeroengine compressor blades etc. The principal qualities of titanium alloys required for these applications are high specific strength, low density and high specific modulus. Among the families of Ti alloys, high strength titanium alloys come under martensitic α + β and metastable β alloys. Titanium alloy Ti-5Al-5V-2Mo (BT-23) is an important example of martensitic α + β alloy similar to the work horse Ti6Al4V alloy which exhibits good combination of strength and ductility in solution treated and aged conditions. But due to quenching from solution treatment temperature, the alloy tends to retain good amount of residual stresses. The severity of residual stress increases with increase in solution treatment temperature as well as severity of quench. An attempt has been made to study the effect of air cooling subsequent to solution treatment to compare the strength of the alloy vis-à-vis that achievable during water quenching. An attempt has also been made to correlate the microstructure evolution, hardness with variation in solution treatment temperature and quench severity in titanium alloy Ti-5Al-2Mo-5V. Samples subjected to air cooling subsequent to solution treatment exhibited higher microhardness when compared to water quenched samples. It is proposed that dynamic aging and/ or stress relieving occurs during air cooling from solution treatment temperature down to room temperature. Also the fine α precipitates formed during air cooling may be resulting in higher hardness compared to the α’’/α’ formed during water quenching. The same has been supported by thermal analysis of air cooling and water quenching processes employed subsequent to solution treatment.