Krishnaraj Vijayan - Academia.edu (original) (raw)
Papers by Krishnaraj Vijayan
This paper reviews the challenges during drilling of composite, titanium, and aluminium stacks. T... more This paper reviews the challenges during drilling of composite, titanium, and aluminium stacks. The machinability aspects of these three material stacks commonly used in aerospace applications are reviewed individually based on influence of drill material, drill geometries, and drilling parameters. Composite material requires high speed and low feed rate, drilling titanium requires low speed and high feed rate whereas drilling aluminium requires a balance between speed to feed rate. The review reports critical results and gap in the literature for composite, titanium and aluminium. Drilling of multimaterial stacks require a compromise between many parameters. The problems and solutions related to drilling of multimaterial stacks are discussed and the directions in which the research on drilling of multimaterials may be carried out are suggested in this paper.
ABSTRACT Titanium and its alloys are attractive materials due to their unique high strength-weigh... more ABSTRACT Titanium and its alloys are attractive materials due to their unique high strength-weight ratio that is maintained at elevated temperatures. Ti-6Al-4V alloy are notorious for their poor thermal properties and are classified as difficult-to-machine materials. Drilling is an important machining process since it is involved in nearly all titanium applications. It is desirable to develop optimised drilling processes for Ti and/or improve the hole characteristics such as hole diameter, circularity and exit burr of currently available processes. Due to the low machinability of the alloy under study, selecting the machining conditions and parameters is crucial. The hole quality, thrust force, torque and exit burr were evaluated at various spindle speeds, feed rates combinations. The optimised parameter is chosen using the multi-objective weighted sum optimisation technique. The tool life for the optimised parameter was studied and the life of the carbide drill was observed to be 140 holes in drilling of titanium.
The thrust force and surface roughness of plain carbide drill (K20) with drill parameters (drill ... more The thrust force and surface roughness of plain carbide drill (K20) with drill parameters (drill diameter, spindle speed and feed rate) in drilling carbon fibre reinforced plastic (CFRP) laminate/aluminum (Grade 2024) stack was experimentally investigated in this study. A L27 orthogonal array and signal-to-noise (S/N) were employed to analyze the effect of drill parameters. Using Taguchi method for design of a robust experiment, the interactions among factors are also investigated. The analysis of variance (ANOVA) shows that the feed rate and drill diameter are the most significant parameters to the overall performance while drilling CFRP/al stack. These results are in good agreement with Signal/Noise (S/N) ratio of Taguchi analysis. Hole diameter of CFRP is found to be less (10μm) than the nominal diameter of drill. Circularity is found to be around 6μm at low feed rates in CFRP. When the feed is increased, the circularity increases to 25 μm.
Fiber-metal compound materials are characterized by excellent mechanical properties and enable in... more Fiber-metal compound materials are characterized by excellent mechanical properties and enable innovative and new designs, which are increasingly used e.g. in the aircraft industry. In modern aircraft structures, two materials are stacked, and then a hole is drilled and a fastener is inserted, thus fastening them together. In areas of high load and stress, CFRP is stacked with titanium or aluminum. Due to the considerably different machining properties of CFRP and metallic materials the drilling process of compound stacks is a very challenging task. In this study, dry and minimum quantity lubrication (MQL) drilling of CFRP/Ti alloy stacks used in aerospace applications have been studied. The maximum thrust forces developed were measured for both the cases .The effects of machining parameters (feed rate and spindle speed) and effect of tool point angles on thrust force and hole quality under dry and lubricating conditions were also investigated. Acoustic emission (AE) signals, genera...
Volume 2A: Advanced Manufacturing, 2014
ASME 2012 International Manufacturing Science and Engineering Conference, 2012
ABSTRACT Carbon fibre reinforced plastics (CFRP) and titanium (Ti) stacks have been steadily repl... more ABSTRACT Carbon fibre reinforced plastics (CFRP) and titanium (Ti) stacks have been steadily replacing metals as choice for engineering materials in aerospace applications. Although materials can be manufactured separately and stacked together to attain a near-net shape, it still involves post processing operations such as trimming and drilling. In order to drill holes efficiently without defects (delamination, circularity, variation in hole diameter) in the CFRP/Ti stacks, it is essential to understand the machining behavior of stacks. An experimental study on the drilling of CFRP/Ti stacks was conducted using K20 carbide drill. The drilling characteristics were evaluated for drilling force and torque, delamination in CFRP, drilled-hole quality (hole diameter and circularity) and exit burr height in Ti. This paper describes an attempt made to maximize the hole quality parameters by employing multi-objective optimization using weighted sum method.
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2006
... email: basavarajappas@yahoo.com JEM304 © IMechE 2006 Proc. IMechE Vol. 220 Part B: J. Enginee... more ... email: basavarajappas@yahoo.com JEM304 © IMechE 2006 Proc. IMechE Vol. 220 Part B: J. Engineering Manufacture REVIEW ARTICLE 1189 ... From 1190 S Basavarajappa, G Chandramohan, KV Narasimha Rao, R Radhakrishanan, and V Krishnaraj Proc. IMechE Vol. ...
International Journal of Materials, Mechanics and Manufacturing, 2014
Volume 2A: Advanced Manufacturing, 2014
Materials Science Forum, 2013
ABSTRACT Titanium alloys present superior properties like resistance to corrosion, high strength ... more ABSTRACT Titanium alloys present superior properties like resistance to corrosion, high strength to weight ratio etc, but possess poor machinability. Titanium alloy Ti-6Al-4V is the most commonly used titanium alloy in aerospace and medical device industries. Titanium and its alloys are notorious for their poor thermal properties and are classified as difficult-to-machine materials. Drilling is an important machining process since it is involved in nearly all titanium applications. It is desirable to develop optimized drilling processes for Ti and improve the hole characteristics such as hole diameter, circularity and exit burr of currently available processes. Due to the low machinability of the alloys under study, selecting the machining conditions and parameters is crucial. The range of spindle speed and feed rate, which provide a satisfactory tool life, is very limited. The hole quality (hole diameter and circularity), thrust force, torque and exit burr were evaluated at various spindle speeds, feed rates combinations. The optimized parameter is chosen using the multi-objective weighted sum optimization technique.
Procedia Engineering, 2014
Titanium alloys are widely used in aerospace industries, due to its high strength to weight ratio... more Titanium alloys are widely used in aerospace industries, due to its high strength to weight ratio and light weight. This paper investigates high speed end milling of titanium alloy (Ti-6% Al-4% V) using carbide insert based end mill cutter. Effects of cutting forces during high speed machining of titanium alloys have got higher attention in selecting the optimal cutting conditions to improve the production and tool life. Due to Titanium alloy's low thermal conductivity, more heat concentration takes place on cutting tool during rough machining. The heat generated increases the temperature of the cutting tool and affect the surface integrity of the workpiece and also cause tool wear. In this study experiments have been carried out under dry cutting conditions. The cutting speeds selected for the experiments are 120, 150 and180 m/min. The depth of cuts and feed rate were selected to suit finish machining. For conducting the experiments single insert based cutting tool is used. Experiments were conducted based on the Taguchi's design of experiments, in order to analyse the effect of cutting parameters on cutting force, temperature and surface roughness. From this study it is found that depth of cut and feed rate have higher effect on cutting forces when compared to cutting speed whereas the effect of cutting speed has higher effect on temperature.
Materials Science Forum, 2013
This paper reviews the challenges during drilling of composite, titanium, and aluminium stacks. T... more This paper reviews the challenges during drilling of composite, titanium, and aluminium stacks. The machinability aspects of these three material stacks commonly used in aerospace applications are reviewed individually based on influence of drill material, drill geometries, and drilling parameters. Composite material requires high speed and low feed rate, drilling titanium requires low speed and high feed rate whereas drilling aluminium requires a balance between speed to feed rate. The review reports critical results and gap in the literature for composite, titanium and aluminium. Drilling of multimaterial stacks require a compromise between many parameters. The problems and solutions related to drilling of multimaterial stacks are discussed and the directions in which the research on drilling of multimaterials may be carried out are suggested in this paper.
Key Engineering Materials, 2010
ABSTRACT
Wear, 2013
This article presents an experimental analysis of drilling using carbide drills on carbon fiber r... more This article presents an experimental analysis of drilling using carbide drills on carbon fiber reinforced plastic (CFRP) laminates specially made with copper mesh on one side and woven carbon fabric on the other side using carbide drills. The objective of this study was to improve the machining performance during drilling of sandwiched composite using various dimensions of double cone drill. The drill design in terms of its tribological characteristics (i.e. friction, wear) are analyzed including cutting force, life, chip form and hole quality. Results have shown that double cone drills generated less thrust force compared to standard twist drills. No delamination was found in the holes at high feed rates (above 0.1 mm/rev). This could be attributed to the presence of thermoplastic nodules between the layers of the CFRP laminate and the presence of woven fabric ply at the bottom of the laminate. Furthermore a relationship between the feed per cutting edge and the thickness of the thermoplastic layer has been developed to promote the formation of continuous chips during drilling. Finally, SEM observations reveal several damage when standard twist drills were used and less damage was observed with double cone drills. These damaged areas were observed in the plies of fibers oriented at À 451 and 901 compared with peripheral cutting speed of the drill.
Procedia Engineering, 2013
Procedia Engineering, 2013
Composites are used in conjunction with another material to form a multi-material stack-up, which... more Composites are used in conjunction with another material to form a multi-material stack-up, which results in greater strength to weight ratios. In a wide range of aerospace applications dissimilar material stack-ups of composites and aluminium and/or titanium are used. Drilling is probably the most common machining operation applied to composites since components made out of composite materials are usually near net shaped and require only holes for assembly integration. In this investigation, experiments were conducted by varying the drilling parameters and determining the optimum cutting conditions for drilling of CFRP/Ti stacks using Genetic Algorithm (GA) optimization technique. Tool wear study was performed by drilling 100 holes each with 118° and 130° point angle drills. Less progressive tool wear and better chip evacuation was achievable in 130° point angle drills when compared with 118°point angle drills.
Procedia Engineering, 2013
International Journal of Materials and Product Technology, 2008
Aircraft manufacturing involves drilling of large number of holes, in which the joint can be crit... more Aircraft manufacturing involves drilling of large number of holes, in which the joint can be critically affected by the quality of the hole. Effect of drill geometry on drilling of glass/epoxy laminates using twist, Zhirov and Multifaceted Drills (MFD), has been studied. The thrust force and hole quality were compared for each drill geometry. Zhirov drill cuts the hole with less force and best surface finish. MFD produces less delamination when compared with the other geometries. ANOVA was used to study the effect of drill geometries, spindle speed, and feed rate on thrust force, surface finish and delamination factor.
This paper reviews the challenges during drilling of composite, titanium, and aluminium stacks. T... more This paper reviews the challenges during drilling of composite, titanium, and aluminium stacks. The machinability aspects of these three material stacks commonly used in aerospace applications are reviewed individually based on influence of drill material, drill geometries, and drilling parameters. Composite material requires high speed and low feed rate, drilling titanium requires low speed and high feed rate whereas drilling aluminium requires a balance between speed to feed rate. The review reports critical results and gap in the literature for composite, titanium and aluminium. Drilling of multimaterial stacks require a compromise between many parameters. The problems and solutions related to drilling of multimaterial stacks are discussed and the directions in which the research on drilling of multimaterials may be carried out are suggested in this paper.
ABSTRACT Titanium and its alloys are attractive materials due to their unique high strength-weigh... more ABSTRACT Titanium and its alloys are attractive materials due to their unique high strength-weight ratio that is maintained at elevated temperatures. Ti-6Al-4V alloy are notorious for their poor thermal properties and are classified as difficult-to-machine materials. Drilling is an important machining process since it is involved in nearly all titanium applications. It is desirable to develop optimised drilling processes for Ti and/or improve the hole characteristics such as hole diameter, circularity and exit burr of currently available processes. Due to the low machinability of the alloy under study, selecting the machining conditions and parameters is crucial. The hole quality, thrust force, torque and exit burr were evaluated at various spindle speeds, feed rates combinations. The optimised parameter is chosen using the multi-objective weighted sum optimisation technique. The tool life for the optimised parameter was studied and the life of the carbide drill was observed to be 140 holes in drilling of titanium.
The thrust force and surface roughness of plain carbide drill (K20) with drill parameters (drill ... more The thrust force and surface roughness of plain carbide drill (K20) with drill parameters (drill diameter, spindle speed and feed rate) in drilling carbon fibre reinforced plastic (CFRP) laminate/aluminum (Grade 2024) stack was experimentally investigated in this study. A L27 orthogonal array and signal-to-noise (S/N) were employed to analyze the effect of drill parameters. Using Taguchi method for design of a robust experiment, the interactions among factors are also investigated. The analysis of variance (ANOVA) shows that the feed rate and drill diameter are the most significant parameters to the overall performance while drilling CFRP/al stack. These results are in good agreement with Signal/Noise (S/N) ratio of Taguchi analysis. Hole diameter of CFRP is found to be less (10μm) than the nominal diameter of drill. Circularity is found to be around 6μm at low feed rates in CFRP. When the feed is increased, the circularity increases to 25 μm.
Fiber-metal compound materials are characterized by excellent mechanical properties and enable in... more Fiber-metal compound materials are characterized by excellent mechanical properties and enable innovative and new designs, which are increasingly used e.g. in the aircraft industry. In modern aircraft structures, two materials are stacked, and then a hole is drilled and a fastener is inserted, thus fastening them together. In areas of high load and stress, CFRP is stacked with titanium or aluminum. Due to the considerably different machining properties of CFRP and metallic materials the drilling process of compound stacks is a very challenging task. In this study, dry and minimum quantity lubrication (MQL) drilling of CFRP/Ti alloy stacks used in aerospace applications have been studied. The maximum thrust forces developed were measured for both the cases .The effects of machining parameters (feed rate and spindle speed) and effect of tool point angles on thrust force and hole quality under dry and lubricating conditions were also investigated. Acoustic emission (AE) signals, genera...
Volume 2A: Advanced Manufacturing, 2014
ASME 2012 International Manufacturing Science and Engineering Conference, 2012
ABSTRACT Carbon fibre reinforced plastics (CFRP) and titanium (Ti) stacks have been steadily repl... more ABSTRACT Carbon fibre reinforced plastics (CFRP) and titanium (Ti) stacks have been steadily replacing metals as choice for engineering materials in aerospace applications. Although materials can be manufactured separately and stacked together to attain a near-net shape, it still involves post processing operations such as trimming and drilling. In order to drill holes efficiently without defects (delamination, circularity, variation in hole diameter) in the CFRP/Ti stacks, it is essential to understand the machining behavior of stacks. An experimental study on the drilling of CFRP/Ti stacks was conducted using K20 carbide drill. The drilling characteristics were evaluated for drilling force and torque, delamination in CFRP, drilled-hole quality (hole diameter and circularity) and exit burr height in Ti. This paper describes an attempt made to maximize the hole quality parameters by employing multi-objective optimization using weighted sum method.
Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture, 2006
... email: basavarajappas@yahoo.com JEM304 © IMechE 2006 Proc. IMechE Vol. 220 Part B: J. Enginee... more ... email: basavarajappas@yahoo.com JEM304 © IMechE 2006 Proc. IMechE Vol. 220 Part B: J. Engineering Manufacture REVIEW ARTICLE 1189 ... From 1190 S Basavarajappa, G Chandramohan, KV Narasimha Rao, R Radhakrishanan, and V Krishnaraj Proc. IMechE Vol. ...
International Journal of Materials, Mechanics and Manufacturing, 2014
Volume 2A: Advanced Manufacturing, 2014
Materials Science Forum, 2013
ABSTRACT Titanium alloys present superior properties like resistance to corrosion, high strength ... more ABSTRACT Titanium alloys present superior properties like resistance to corrosion, high strength to weight ratio etc, but possess poor machinability. Titanium alloy Ti-6Al-4V is the most commonly used titanium alloy in aerospace and medical device industries. Titanium and its alloys are notorious for their poor thermal properties and are classified as difficult-to-machine materials. Drilling is an important machining process since it is involved in nearly all titanium applications. It is desirable to develop optimized drilling processes for Ti and improve the hole characteristics such as hole diameter, circularity and exit burr of currently available processes. Due to the low machinability of the alloys under study, selecting the machining conditions and parameters is crucial. The range of spindle speed and feed rate, which provide a satisfactory tool life, is very limited. The hole quality (hole diameter and circularity), thrust force, torque and exit burr were evaluated at various spindle speeds, feed rates combinations. The optimized parameter is chosen using the multi-objective weighted sum optimization technique.
Procedia Engineering, 2014
Titanium alloys are widely used in aerospace industries, due to its high strength to weight ratio... more Titanium alloys are widely used in aerospace industries, due to its high strength to weight ratio and light weight. This paper investigates high speed end milling of titanium alloy (Ti-6% Al-4% V) using carbide insert based end mill cutter. Effects of cutting forces during high speed machining of titanium alloys have got higher attention in selecting the optimal cutting conditions to improve the production and tool life. Due to Titanium alloy's low thermal conductivity, more heat concentration takes place on cutting tool during rough machining. The heat generated increases the temperature of the cutting tool and affect the surface integrity of the workpiece and also cause tool wear. In this study experiments have been carried out under dry cutting conditions. The cutting speeds selected for the experiments are 120, 150 and180 m/min. The depth of cuts and feed rate were selected to suit finish machining. For conducting the experiments single insert based cutting tool is used. Experiments were conducted based on the Taguchi's design of experiments, in order to analyse the effect of cutting parameters on cutting force, temperature and surface roughness. From this study it is found that depth of cut and feed rate have higher effect on cutting forces when compared to cutting speed whereas the effect of cutting speed has higher effect on temperature.
Materials Science Forum, 2013
This paper reviews the challenges during drilling of composite, titanium, and aluminium stacks. T... more This paper reviews the challenges during drilling of composite, titanium, and aluminium stacks. The machinability aspects of these three material stacks commonly used in aerospace applications are reviewed individually based on influence of drill material, drill geometries, and drilling parameters. Composite material requires high speed and low feed rate, drilling titanium requires low speed and high feed rate whereas drilling aluminium requires a balance between speed to feed rate. The review reports critical results and gap in the literature for composite, titanium and aluminium. Drilling of multimaterial stacks require a compromise between many parameters. The problems and solutions related to drilling of multimaterial stacks are discussed and the directions in which the research on drilling of multimaterials may be carried out are suggested in this paper.
Key Engineering Materials, 2010
ABSTRACT
Wear, 2013
This article presents an experimental analysis of drilling using carbide drills on carbon fiber r... more This article presents an experimental analysis of drilling using carbide drills on carbon fiber reinforced plastic (CFRP) laminates specially made with copper mesh on one side and woven carbon fabric on the other side using carbide drills. The objective of this study was to improve the machining performance during drilling of sandwiched composite using various dimensions of double cone drill. The drill design in terms of its tribological characteristics (i.e. friction, wear) are analyzed including cutting force, life, chip form and hole quality. Results have shown that double cone drills generated less thrust force compared to standard twist drills. No delamination was found in the holes at high feed rates (above 0.1 mm/rev). This could be attributed to the presence of thermoplastic nodules between the layers of the CFRP laminate and the presence of woven fabric ply at the bottom of the laminate. Furthermore a relationship between the feed per cutting edge and the thickness of the thermoplastic layer has been developed to promote the formation of continuous chips during drilling. Finally, SEM observations reveal several damage when standard twist drills were used and less damage was observed with double cone drills. These damaged areas were observed in the plies of fibers oriented at À 451 and 901 compared with peripheral cutting speed of the drill.
Procedia Engineering, 2013
Procedia Engineering, 2013
Composites are used in conjunction with another material to form a multi-material stack-up, which... more Composites are used in conjunction with another material to form a multi-material stack-up, which results in greater strength to weight ratios. In a wide range of aerospace applications dissimilar material stack-ups of composites and aluminium and/or titanium are used. Drilling is probably the most common machining operation applied to composites since components made out of composite materials are usually near net shaped and require only holes for assembly integration. In this investigation, experiments were conducted by varying the drilling parameters and determining the optimum cutting conditions for drilling of CFRP/Ti stacks using Genetic Algorithm (GA) optimization technique. Tool wear study was performed by drilling 100 holes each with 118° and 130° point angle drills. Less progressive tool wear and better chip evacuation was achievable in 130° point angle drills when compared with 118°point angle drills.
Procedia Engineering, 2013
International Journal of Materials and Product Technology, 2008
Aircraft manufacturing involves drilling of large number of holes, in which the joint can be crit... more Aircraft manufacturing involves drilling of large number of holes, in which the joint can be critically affected by the quality of the hole. Effect of drill geometry on drilling of glass/epoxy laminates using twist, Zhirov and Multifaceted Drills (MFD), has been studied. The thrust force and hole quality were compared for each drill geometry. Zhirov drill cuts the hole with less force and best surface finish. MFD produces less delamination when compared with the other geometries. ANOVA was used to study the effect of drill geometries, spindle speed, and feed rate on thrust force, surface finish and delamination factor.