Applied Mechanics and Materials Vol. 787

Abstract: Friction stir welding (FSW) is a relatively better joining technique particularly for magnesium and aluminum alloys that are difficult to weld by fusion welding techniques. Fusion welding of these alloys is not preferable due to hot cracking, formation of porosity, etc. However solid state welding techniques, such as, friction sitr welding are found to offer solution to the above problems. Many research papers available in open literature focusing tensile properties, microstructural characteristics, and corrosion behaviour of friction stir welded AZ31B magnesium alloys but fatigue behaviour of these welds are not yet investigated. Hence, in this investigation, an attempt has been made to evaluate fatigue behaviour of friction stir welded rolled plates of AZ31B magnesium alloys.Fatigue experiment was conducted using servo hydraulic controlled fatigue testing machine. Fatigue strength, fatigue notch factor and notch sensitivity factor were evaluated. It is found that the fatigue strength of AZ31B welded joints is 46 MPa at 2x10⁶ cycles which is approximately 34 % lower than that of the base metal fatigue strength.

Abstract: In modern machining processes, there are continuous cost pressures and high quality expectations in the product. Hence, it is required to explore the techniques that can reduce the cost and also increase the quality of the product. In the present work, machining performance of AISI 316L SS is assessed by the performing turning operation under nano cutting environment. Experiments have been carried out by plain turning of 48mm diameter and 600mm long rod of AISI 316L stainless steel on all geared lathe at different cutting velocities and feeds under wet machining with and without Carbon nano Tubes (CNT) inclusions using carbide inserts. The effect of cutting speed, feed rate, depth of cut on tool chip interface temperature and surface roughness are analysed using Taguchi method. Furthermore, using analysis of variance method, significant contributions of process parameters have been determined. Experimental results reveal that feed rate and cutting speed are the dominant variables on responses.

Abstract: NiTi alloys possess superior material properties such as high specific strength, high corrosion resistance, high wear resistance and high anti-fatigue property. Due to these properties it is difficult to machine these alloys using conventional machining process. Nowadays non-conventional machining processes are widely used for machining such adavanced materials. Electrical Discharge machining (EDM) is one such non-conventional process, which can machine electrically conductive materials of any hardness values. Present study aims at drilling mesoscale 3 mm square holes on NiTi alloy by varying the electrical parameters namely, gap current, pulse on time and pulse off time. Additional, the present work includes finding out the effect of cryogenic treatment of NiTi work material on electrical discharge machining performance measures namely material removal rate (MRR) and tool wear rate (TWR). Based on experiments conducted, it can be concluded that with increase in current both material removal rate and tool wear rate increases. It is also noted that cryo-treatment of workpiece material improves MRR with respect to gap current. Similarly there is an increase in MRR with respect to pulse on time and pulse off time for cryo-treated workpiece material. There is a slight improvement of TWR with respect to gap current, pulse on time and pulse off time for cryo-treated workpiece material.

Abstract: Monel alloys are pioneering materials which have exceptional engineering properties such as corrosion resistance, high toughness and show good response to cryogenic treatment. It finds uses in ship building, nuclear aerospace, missile and valve industries. These materials shows strain hardening effect which results in tool wear and in some cases tool breakage when machined by conventional methodshence, unconventional machining such as electrical discharge machining (EDM)discoverspurpose for machining of such materials. Researchers have recognized relation between electrical input process parameters of EDM process and output parameters of EDM process. But researchers have not investigated the influence of external magnetic field and cryo-treatment of work piece on EDM performance measures namely material removal rate (MRR) and tool wear rate (TWR). In vision of this the objective of present work was to study the effect of gap current, external magnetic field and cryogenic treatment of work part on MRR and TWR. Experiments were carried out by creating a 3 mm square hole on Monel400 alloys. Based on experimental results it was found that as gap current increases the MRR and TWR increases for untreated work part. For treated work part MRR increases and TWR decreases with increasein gap current. MRR and TWR increases with constant gap current for untreated work part, as magnetic field increases. For treated work part MRR increases and TWR decreases with increase in magnetic field at constant gap current.

Abstract: To Acompany the novel technology advancement demands for advance materials. Beryllium copper is such solitary material which has conspicuous material properties, to be pricise good wear resistance, corrosion resistance and high fatigue strength. But the concern with this is machining by treditional machining processes. To defeat this problem Powder Mixed Electric Discharge Machining(PMEDM) is a surrogate technology, which is acquiring much importance in machining such materials. As compared to convenctional electric discharge machining the powder mixed electric discharge machining has delivered much efficiency because of the addition of fine powder particles in dielectric media. It increases the steadiness and concentrated sparking on the work piece material. This study aims at machining beryllium copper alloys using powder mixed electric discharge machining. The electric parameters namely pulse on time, pulse off time, and gap voltage are retained constant throughout the experimentation. Copper electrode of 3 mm square tip was used for machining of beryllium copper work piece. Gap current is varied as 8 A, 10 A, 12 A and 14 A whereas powder concentration is varied as 2 gm/litre, 4 gm/litre and 6 gm/litre. Material removal rate (MRR) and tool wear rate (TWR) were considered as electric discharge machining output measures for the study. It was observed that the efficiency of powder mixed electric discharge machining improved by using powder mixed dielectric. It was found that the MRR improves as the gap current is increased by the increament of 2A. One more obeservation found was the improvement in the both MRR and TWR with the increase in the powder concentration . Tool wear rate increases due to the truth that as the depth of machining increases the efficiency of flushing reduces hence leading to higher tool wear rate.

Abstract: The aim of the present study is to investigate on mechanical and microstructural properties of Friction Stir Welded 316 L austenitic stainless steel. Defect free weld were produced at a tool rotational speed (N) of 600 rpm, transverse speed (V) of 45 mm/min, axial force (F) of 11 kN and tool tilt angle (T) of 1.5⁰.Mechanical properties such as Ultimate Tensile strength (UTS), Percentage Elongation (PE), Impact Strength (IS) were evaluated on the welded specimen. Further,micro hardness and microstructural analysis were carried out the transverse direction to the welded specimen. No significance of HAZ in the welded joint with observation of sigma phase precipitation revealed by Groesbeck and Modified Mukrami reagent. Further,FESEM with Electron Dispersive Spectroscopy (EDS) were obtained at the stir zone to ensure constituent of alloying elements present and ensuring no secondary phases found in the stir zone.

Abstract: Beryllium copper possesses high strength which produces severe problem of surface integrity and tool wear during machining by conventional machining process. Electrical discharge machining is a practically viable option to solve this problem. The present study investigates the effect of cryogenic treatment of work part along with gap current and external magnetic field on material removal rate (MRR) and tool wear rate (TWR). Blind 3 mm square holes were produced using electrolytic copper tool electrode to machine cryo-treated BeCu and untreated BeCu. Gap current is varied from 8 A to 16 A in a step of 2 amperes and magnetic strength is varied from 0 to 0.496 T in a step of 0.124 T. Based on the experimental results it was found that MRR increases with increase in gap current for both untreated BeCu and treated work part. Plotted graphs of cryo-treated work part showed high values of MRR in comparison to untreated work part. TWR increases for both treated and untreated BeCu work part with increase in gap current. But the TWR was less for cryo-treated work part in comparison to untreated work part. MRR and TWR increases for both treated and untreated BeCu work part with increasing magnetic strength. Again the MRR was found higher with lower TWR for treated workpiece with regard to magnetic strength. Thus it can be concluded that cryogenic-treatment with magnetic strength improves EDM machining efficiency.

Abstract: Manufacturing industries are presently using many tool materials, such as high speed steel, carbide tool and diamond tools etc. The most widely and commonly used tool in the engineering industries is high speed steel (HSS). The HSS tools are the cheapest and reliable for medium and small scale industries. In this work, the HSS single point cutting tool is taken as substrate material and coated with two different combinations of TiAlN composite coating using Physical vapour deposition (PVD) technique. Also, Tool life was calculated and compared with uncoated HSS tool. The hardness and surface roughness value for both the tools have been taken under same condition. The loss of weight in the tool after machining has been weighed using standard equipments. The differences have been closely observed with sufficient trials and find out the loss in weight in both the tools. The weight loss percentage was calculated after proper machining trials. The tool life of the Titanium Aluminium Nitride (Ti 70%, Al 25%) coated tool has been increased by 3.74 times than that of uncoated tool. The surface finish for TiAlN (Ti 70%, Al 25%) coating is better than the uncoated tool. The PVD coated tools having better performance comparing with uncoated HSS tool.

Abstract: Design structures made of aluminium alloy and steel are useful to meet the needs of automotive industry such as light weight and higher strength. An effective joining technique to join light weight metals such as aluminium alloys with steel is required. Friction stir spot welding (FSSW) is relatively a new solid state process and it is a derivative of Friction Stir Welding. It creates a spot, lap joint weld without bulk melting. The FSSW parameters such as tool rotational speed, plunge depth, and dwell time plays a major role in determining the strength of the joints and need to be optimized to get quality joints. In this investigation, a central composite rotatable design with three factors and five levels was chosen to minimize the number of experimental conditions. Response surface methodology (RSM) was applied to optimize the FSSW parameters to attain maximum lap shear strength of the spot weld.

Abstract: An attempt is made to reduce the process forces and tool wear during friction stir welding of 409M ferritic stainless steel and to enhance the mechanical properties by induction preheating of base metal with different preheating temperatures at the leading of tool. It is observed that the preheating significantly decreased the longitudinal and axial forces. Tool degradation analysis was carried out to find out the loss of tool profile and material. Mechanical properties especially impact toughness values were increased due to significant reduction in the tool wear.