Simultaneous Optimization of Multiple Quality Characteristics in Laser Beam Cutting Using Taguchi Method

Avanish Kumar Dubey,Vinod Yadava 한국정밀공학회 2007 International Journal of Precision Engineering and Vol.8 No.4

Taguchi methods have been used for a long time to improve the product quality and process performance of a manufacturing system. Few researchers have applied this methodology in laser beam cutting (LBC) of sheet metals and found the considerable improvement in cut qualities. In all experimental investigations of LBC so far, the objective was to optimize the single quality characteristic at a time. In this paper the simultaneous optimization of multiple quality characteristics such as Kerf width and material removal rate (MRR) during pulsed Nd: YAG LBC of thin sheet of magnetic material (high Silicon-steel) has been presented using Taguchi’s quality loss function. The results show the considerable improvement in multiple S/N ratio as compared to initial cutting condition. Also, the comparison of results from single and multi-objective optimization have been presented and it was found that the loss in quality is always possible shifting from Single quality to multiple quality optimization.

Evaluation of Machining Performance for Electrochemical Surface Grinding of Aluminium Based Hybrid MMC

Avanish Kumar Dubey,Dhruv Kant Rahi 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.9

Development of newer materials necessitates suitable machining devices which can overcome the limitations of existing conventional or unconventional machining systems. Keeping this in view, a hybrid machining set-up of electrochemical machining with surface grinding has been developed to study the machining performance of difficult-to-cut hybrid metal matrix composite Al-SiC-Gr. Effect of applied voltage, electrolyte concentration, wheel speed and work table speed on machining performance have been analysed. Material removal rate and surface finish significantly improve with increase in applied voltage or electrolyte concentration. Increase in grinding wheel speed and work table speed adversely affects the performance. Scanning Electron Microscopy images have been analysed to study the morphology of machined specimen.

Breakthrough behaviour of NBC canister against carbon tetrachloride: a simulant for chemical warfare agents

Avanish Kumar Srivastava,D. Shah,T.H. Mahato,Beer Singh,A. Saxena,A.K. Verma,S. Shrivastava,A. Roy,S.S. Yadav,A.R. Shrivastava 한국탄소학회 2012 Carbon Letters Vol.13 No.2

A nuclear, biological, chemical (NBC) canister was indigenously developed using active carbon impregnated with ammoniacal salts of copper (II), chromium (VI) and silver (I), and high efficiency particulate aerosol filter media. The NBC canister was evaluated against carbon tetra chloride (CCl4) vapours, which were used as a simulant for persistent chemical warfare agents under dynamic conditions for testing breakthrough times of canisters of gas masks in the National Approval Test of Respirators. The effects of CCl4 concentration, test flow rate, temperature, and relative humidity (RH) on the breakthrough time of the NBC canister against CCl4 vapour were also studied. The impregnated carbon that filled the NBC canister was characterized for surface area and pore volume by N2 adsorption-desorption isotherm at liquid nitrogen temperature. The study clearly indicated that the NBC canister provides adequate protection against CCl4 vapours. The breakthrough time decreased with the increase of the CCl4 concentration and flow rate. The variation in temperature and RH did not significantly affect the breakthrough behaviour of the NBC canister at high vapour concentration of CCl4, whereas the breakthrough time of the NBC canister was reduced by an increase of RH at low CCl4 vapour concentration.

Development and Evaluation of Impregnated Carbon Systems Against Iodine Vapours

Avanish Kumar Srivastava,Amit Saxena,Beer Singh,Suresh Kumar Srivas 한국탄소학회 2007 Carbon Letters Vol.8 No.4

In order to understand the breakthrough behaviour of iodine vapours on impregnated carbon systems, an active carbon, 80 CTC grade, 12×30 BSS particle size and 1104 m2/g surface area, was impregnated with metal salts such Cu, Cr, Ag, Mo and Zn, and an organic compound Triethylene diamine (TEDA) to prepare different carbon systems such as whetlerite, whetlerite/TEDA, whetlerite/KI/KOH and ASZMT. The prepared adsorbents along with active carbon were characterized for surface area and pore volume by N2 adsorption at liquid nitrogen temperature. These carbon systems were compared for their CT (concentration X time) values at 12.73 to 53.05 cm/sec space velocities and 2 to 5 cm carbon column bed heights. The carbon column of 5.0 cm bed height and 1.0 cm diameter was found to be providing protection against iodine vapours up to 5.5 h at 3.712 mg/L iodine vapour concentration and 12.73 cm/sec space velocity. The study clearly indicated the adsorption capacities of carbon systems to be directly proportional to their surface area values. Dead layer with all the prepared carbon systems was found to be less than 2.0 cm indicating it to be minimum bed height to have protection against I2 vapours. Effect of carbon bed height and flow rate was also studied. The active carbon showed maximum protection at all bed heights and flow rates in comparison to all other impregnated carbon systems, showing that only physical adsorption is responsible for the removal of iodine vapours.

Isolation of pristine MXene from Nb₄AlC₃ MAX phase: a first-principles study

Mishra, Avanish,Srivastava, Pooja,Mizuseki, Hiroshi,Lee, Kwang-Ryeol,Singh, Abhishek K. The Royal Society of Chemistry 2016 Physical Chemistry Chemical Physics Vol.18 No.16

<P>Synthesis of pristine MXene sheets from MAX phase is one of the foremost challenges in getting a complete understanding of the properties of this new technologically important 2D-material. Efforts to exfoliate Nb4AlC3 MAX phase always lead to Nb4C3 MXene sheets, which are functionalized and have several Al atoms attached. Using the first-principles calculations, we perform an intensive study on the chemical transformation of MAX phase into MXene sheets by inserting HF, alkali atoms and LiF in Nb4AlC3 MAX phase. Calculated bond-dissociation energy (BDE) shows that the presence of HF in MAX phase always results in functionalized MXene, as the binding of H with MXene is quite strong while that with F is weak. Insertion of alkali atoms does not facilitate pristine MXene isolation due to the presence of chemical bonds of almost equal strength. In contrast, weak Li-MXene and strong Li-F bonding in Nb4AlC3 with LiF ensured strong anisotropy in BDE, which will result in the dissociation of the Li-MXene bond. Ab initio molecular dynamics calculations capture these features and show that at 500-650 K, the Li-MXene bond indeed breaks leaving a pristine MXene sheet behind. The approach and insights developed here for chemical exfoliation of layered materials bonded by chemical bonds instead of van der Waals can promote their experimental realization.</P>

Development and Evaluation of Impregnated Carbon Systems Against Iodine Vapours

Srivastava, Avanish Kumar,Saxena, Amit,Singh, Beer,Srivas, Suresh Kumar Korean Carbon Society 2007 Carbon Letters Vol.8 No.4

In order to understand the breakthrough behaviour of iodine vapours on impregnated carbon systems, an active carbon, 80 CTC grade, $12{\times}30$ BSS particle size and $1104\;m^2/g$ surface area, was impregnated with metal salts such Cu, Cr, Ag, Mo and Zn, and an organic compound Triethylene diamine (TEDA) to prepare different carbon systems such as whetlerite, whetlerite/TEDA, whetlerite/KI/KOH and ASZMT. The prepared adsorbents along with active carbon were characterized for surface area and pore volume by $N_2$ adsorption at liquid nitrogen temperature. These carbon systems were compared for their CT (concentration X time) values at 12.73 to 53.05 cm/sec space velocities and 2 to 5 cm carbon column bed heights. The carbon column of 5.0 cm bed height and 1.0 cm diameter was found to be providing protection against iodine vapours up to 5.5 h at 3.712 mg/L iodine vapour concentration and 12.73 cm/sec space velocity. The study clearly indicated the adsorption capacities of carbon systems to be directly proportional to their surface area values. Dead layer with all the prepared carbon systems was found to be less than 2.0 cm indicating it to be minimum bed height to have protection against $I_2$ vapours. Effect of carbon bed height and flow rate was also studied. The active carbon showed maximum protection at all bed heights and flow rates in comparison to all other impregnated carbon systems, showing that only physical adsorption is responsible for the removal of iodine vapours.

Simultaneous Optimization of Multiple Quality Characteristics in Laser Beam Cutting Using Taguchi Method

Dubey, Avanish Kumar,Yadava, Vinod Korean Society for Precision Engineering 2007 International Journal of Precision Engineering and Vol.8 No.4

Taguchi methods have been used for a long time to improve the product quality and process performance of a manufacturing system, Few researchers have applied this methodology in laser beam cutting (LBC) of sheet metals and found the considerable improvement in cut qualities. In all experimental investigations of LBC so far, the objective was to optimize the single quality characteristic at a time. In this paper the simultaneous optimization of multiple quality characteristics such as Kerf width and material removal rate (MRR) during pulsed Nd:YAG LBC of thin sheet of magnetic material (high Silicon-steel) has been presented using Taguchi's quality loss function. The results show the considerable improvement in multiple S/N ratio as compared to initial cutting condition. Also, the comparison of results from single and multi-objective optimization have been presented and it was found that the loss in quality is always possible shifting from single quality to multiple quality optimization.

Atomistic Origin of Phase Stability in Oxygen-Functionalized MXene: A Comparative Study

Mishra, Avanish,Srivastava, Pooja,Carreras, Abel,Tanaka, Isao,Mizuseki, Hiroshi,Lee, Kwang-Ryeol,Singh, Abhishek K. American Chemical Society 2017 The Journal of Physical Chemistry Part C Vol.121 No.34

<P>Oxygen-functionalized MXene, M2CO2 (M = group III-V metals), are emergent formidable two-dimensional (2D) materials with a tantalizing possibility for device applications. Using first-principles calculations, we perform an intensive study, on the stability of fully O-functionalized (M2CO2) MXenes. Depending on the position of O atoms, the M2CO2 can a.) O atom occupies a site which is exactly on the top of the metal exist in two different structural phases. On one side of MXene, the atom from the opposite side. On the other side, the O atom can occupy either the site on the top of the metal atom of the opposite side (BB' phase) or on the top of the C atom (CB phase). We find that for M = Sc and Y the CB phase is stable, whereas for M = Ti, Zr, Hf, V, Nb, and Ta the stable phase is BB'. The electron localization function, the atom-projected density of states, the charge transfer, and the Bader charge analyses provide a rational explanation for the relative stability of these two phases and justify the ground state structure by giving information about the preferential site of adsorption for the O atoms. We also calculate the phonon dispersion relations for both phases of M2CO2. The BB'-Sc2CO2 and the CB-Ti2CO2 are found to 'be dynamically unstable. Finally, we find that the instability of BB'-M2CO2 (M = Sc and Y) originates from the weakening of M-C interactions, which manifest as a phonon mode with imaginary frequency corresponding to the motion of C atom in the a-b plane. The insight into the stability of these competing structural phases of M2CO2 presented in this study is an important step in the direction of identifying the stable phases of these 2D materials.</P>

Modeling and optimization of geometrical characteristics in laser trepan drilling of titanium alloy

Rupesh Goyal,Avanish Kumar Dubey 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.3

Laser drilling has become an alternative to drilling precise holes in advanced difficult-to-cut superalloys. Due to better hole quality and capability to generate macro-size holes, laser trepan drilling is becoming more popular as compared with laser percussion drilling. This paper presents a study of laser trepan drilling process performance in terms of geometrical quality characteristics, such as hole taper and circularity for drilling small diameter hole in difficult-to-cut Titanium alloy sheet. Due to involvement of different process parameters such as laser power, pulse width, pulse frequency, workpiece thickness, material composition, cutting speed, stand of distance and assist gas pressure, the laser cutting is a highly nonlinear and complex process. To handle this nonlinearity and complexity, genetic algorithm has been applied for the optimization. We used assist gas pressure, pulse width, pulse frequency and trepanning speed as input process parameters. The effect of significant process parameters on hole characteristics are discussed on the basis of data obtained through a well designed orthogonal array experimental matrix. Reliable empirical models have been developed for different quality characteristics. Improvements of 49% and 8% have been registered in hole taper and circularity, respectively, at optimum level of process parameters.

Computer-Aided Genetic Algorithm Based Multi-Objective Optimization of Laser Trepan Drilling

Sanjay Kumar,Avanish Kumar Dubey,Arun Kumar Pandey 한국정밀공학회 2013 International Journal of Precision Engineering and Vol. No.

The laser trepan drilling (LTD) has proven to produce better quality holes in advanced materials as compared with laser percussion drilling (LPD). But due to thermal nature of LTD process, it is rarely possible to completely remove the undesirable effects such as recast layer, heat affected zone and micro cracks. In order to improve the hole quality, these effects are required to be minimized. This research paper presents a computer-aided genetic algorithm-based multi-objective optimization (CGAMO) methodology for simultaneous optimization of multiple quality characteristics. The optimization results of the software CGAMO has been tested and validated by the published literature. Further, CGAMO has been used to simultaneously optimize the recast layer thickness (RLT) at entrance and exit in LTD of nickel based superalloy sheet. The predicted results show minimization of 99.82% and 85.06% in RLT at entrance and exit, respectively. The effect of significant process parameters on RLT has also been discussed.