Somnath Chattopadhyaya

Characterization of Friction Surfaced Coatings of AISI 316 Tool over High-Speed-Steel Substrate

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Surface Treatment of AISI 304 Using Pulsating Water Jet Peening

Water jet peening has gained attention as a potential surface treatment process for improving the fatigue life of a component. The tensile residual stress in the component initiates the stress corrosion cracking and reduces its fatigue life. The mitigation of this tensile residual stress can be effectively achieved by water jet peening process due to its resistance to corrosion, flexibility in treating complex areas and capability to maintain the eco-friendly environment. In the present work, the AISI 304 plates were treated with pulsating water jet (actuator frequency f = 20.19 Hz) at the pressure of p = 20 MPa with traverse speed of v = 0.5 mm/s and v = 2.5 mm/s using two different types of nozzles; flat nozzle of diameter d = 1 mm (HAMMELMANN) and circular nozzle of diameter d = 1.9 mm (STONEAGE). The microstructural analysis of the treated and untreated region was conducted to analyse the effect of traverse speed and the type of nozzle on the erosion process. The study revealed that more erosion occurs at lower traverse speed; however, fewer surface depressions were observed in the case of flat nozzles. The X-ray diffraction technique was also used to analyse the effect of traverse speed and the type of nozzle on the residual stress of the samples. In addition to this, the acoustic emission during the ongoing process was monitored using LabView 2012 SP1 f5 ver. 12.0.1. The results indicate that acoustically monitored pulsating water jet peening process can be used as tool for the controlled local treatment process arising from the impact of the pulsed water jet on the surface of sample.

Performance Analysis of Pulsating Water Jet Machining During Disintegration of Rocks by Means of Acoustic Emission

Over the decades, water jet cutting has been widely used for rock disintegration in mining operations and quarrying purposes. The impact of high-pressure water jet on hard material like rock, coal ruins the original structure of the material; therefore, low-pressure water jet comes into the existence. In recent year, pulsating water jet has been applied in numerous ways such as surface cleaning, exclusion of damaged material layers, preparation of surfaces, and disintegration of materials. It has also a great potential for application in hard rock breakage as conventional methods are cumbersome, not readily accessible and have economical limitations. The performance of the jet increases significantly by the generation of pulses causing disintegration of material at a relatively lower energy and costs. This paper focuses on the study of the disintegration processes of marble and granite by pulsating water jet subjected to erosion via acoustic emission. The experiments are performed by using pulsating water jet with modulation frequency of 20.20 kHz. The MVT circular nozzle with an orifice diameter of 0.9 mm, standoff distance from the target material 6 mm, traverse speed varied from 2 to 16 mm/s, and pump pressure 60 MPa was used for water jetting. The topography of granites and marble on the cut depth and surface quality were investigated by the optical profile meter. Moreover, dependable relations between some physical and mechanical properties of the rocks and the depth of cut were observed. The online monitoring of acoustic emission shows the change in response to the pulse frequency at different time intervals.

Influence of Abrasive Water Jet Turning Parameters on Variation of Diameter of Hybrid Metal Matrix Composite

Abrasive water jet turning is one of the recently developed manufacturing technologies. It has gained its importance due to its capability to machine difficult-to-cut material with advantages such as absence of thermal effects, high machining flexibility and little cutting force. In this study, the influence of water jet turning parameters such as abrasive type and abrasive mass flow rate has been analysed on the variation of diameter with the target diameter of metal matrix composite. Composite material A359/Al2O3/B4C fabricated by electromagnetic stir casting process was used in the experiment. To select the level of parameter, one-variable-at-a-time analysis was used. The results revealed that the abrasive type had a greater influence on the deviation of diameter from the target diameter as compared to mass flow rate.

Surface alloying of miniature components by micro-electrical discharge process

ABSTRACT Surface alloying is necessary to enhance the surface features of machine elements. In the present study, feasibility of micro-electric discharge machining (micro-EDM) process for surface alloying has been investigated. Experiments are conducted on Nickel sheets using tool of Ti6Al4V with EDM oil and kerosene as dielectric. The surface modification takes place by spark discharges on localized regions of the work piece and the tool surface causing melting of tool and work piece, disassociation of dielectric, alloying, and quenching in the electrolyte. The samples were analyzed by field emission scanning electron microscope equipped with energy-dispersive X-ray spectroscopy, microhardness testing machine, and X-ray diffraction. Recast layers obtained have distinct structure and composition as compared to the work piece. Average recast layer thickness varied from 10.72 to 69.8u2009µm in case of EDM oil and from 13.5 to 31.6u2009µm in case of kerosene by varying voltage, pulse duration (on time) and frequency during the experiment. The microhardness of the machined surfaces was obtained in a wide range of 161.61–338.25 HV whereas the microhardness of unaffected base metal was 132.25 HV. Titanium carbide (TiC) was deposited and consequently there was improvement in the hardness of the work piece.

Micro-electrical discharge machining of difficult-to-machine materials: A review:

Electrical discharge machining has emerged as one of the most accepted non-traditional machining methods that have the capability of attaining complex shapes and better feature size in difficult-to-machine materials. In this article, an advanced review of conventional electrical discharge machining and micro–electrical discharge machining of difficult-to-machine materials, such as nickel and its alloys, titanium alloys, stainless steel (SUS 304) and advanced ceramics, has been presented. The review begins with an introduction to the conventional electrical discharge machining and micro–electrical discharge machining processes, followed by classifications and a brief discussion on different aspects of micro-manufacturing methods. The current research trends and developments, research gaps and challenges of the conventional electrical discharge machining and micro–electrical discharge machining of nickel and its alloys, titanium alloys (Ti6Al4V), stainless steel and advanced ceramics are also discussed in depth. A brief note on future research trends, based on the available literature, has been included in the last section.

Modeling and Validation of Spindle Shaft Followed by Goal Driven Optimization

The spindle bearing system is critical component in any machining center due to its complexity and it directly affects design or selection of components. Fail-safe design is traditional design philosophy of the machine centers which leads to over-sized machine tool design including spindle bearing system. Over-sized spindle design affects the performance characteristics of the machine center and should be optimized. Therefore, this work presents a methodology for design optimization of spindle shaft that is subjected to uniformly distributed load. The deflection distribution of shaft due to given loading condition is a way for controlling the stability of spindle and its failure. In this work analytical as well as numerical methodology is presented for modeling and validation of spindle shaft deflection. The analytical modeling of spindle uses conventional beam theory whereas numerical modeling uses finite element analysis (FEA) software ANSYS. Analytical model is validated by performing static structural analysis using BEAM188 element and used further to calculate optimum bearing spacing for minimum deflection. Finally, analytically calculated optimum bearing span is used as design variable with specific range. Thus, a goal driven optimization (GDO) is performed in ANSYS with mass reduction as an objective function and deflection as design constraint.

An Acoustic Emission Study of Rock Disintegration by Pulsating Water-Jet

The collision of a high-velocity liquid mass with a solid generates short high pressures transients, which is responsible for the damage to the surface and its interior. The main advantage of the pulsating jet as compared to the continuous water-jet technology is that the impact pressure (due to hammering effect) is several times greater in pulsating water jet. The impact of the pulses induces fatigue stresses in the target material due to cyclic loading which is the most influential factor responsible for the disintegration. However, this technology is reported to the current trend of the application. During the laboratory experiments on Silesian granite were examined the relationship between the acoustic emission and parametric conditions of the pulsating water-jet. This research paper deals with an application of acoustic emission measurement as an on-line monitoring tool for analyzing the disintegration phenomenon of rock by pulsating water jet which locally affects the structural integrity of rocks. The correlation between rock disintegration and dynamic signal performance was obtained for several rock materials at various settings of jet parameters.

Additive Printing of Gold Nanoparticles on Paper Substrate Through Office Ink-Jet Printer

The article reports the synthesis of the concentrated Gold Nanoparticles (AuNPs) ink and its printing on the paper substrate through Office Ink Jet printer. Initially, AuNPs were synthesized from the precursor Gold (III) Acetate through Ultrasonic Spray Pyrolysis. Ellipsoidal shaped AuNPs with a size distribution of below 50 nm were confirmed through TEM and DLS measurement. Maximum absorbance wavelength of AuNPs measured through UV-vis spectroscopy was 532 nm. Further, the AuNPs ink was prepared through the rotavapour and filtered upto the Au concentration of 600 ppm determined through ICP-OES. The AuNPs printed patterns on the photo paper substrate were successfully printed and further analyzed with SEM.

Prediction of Tensile Failure Load for Maraging Steel Weldment by Acoustic Emission Technique

Maraging steel (Grade 250) pressurized chambers are used in booster stages for the launch vehicles and missiles. These are designed & realized with ultra high strength steels like Maraging steels in order to gain in range and pay load capabilities with optimal Factor-of-Safety(FOS). Effective manufacturing methodology and fracture control is a prime requirement however manufacturing processes give rise to defects that are inevitable. Non-Destructive Engineering techniques viz. ultrasonic testing, Radiography testing, Eddy current testing etc. address the issue of detecting passive defects only. Defects that are active i.e. critical and that could cause catastrophe shall be detected possibly during Proof pressure testing Strain gauge method adopted is restricted for strain measurements and is in-effective in detecting flaws as it is a highly localized. Acoustic Emission Technique (AET), as a whole field method, has ability to detect unstable flaws effectively. Acoustic emissions are generated due to defects, microstructural variation, presence of inclusions and second phase particles in metallic materials. AET identifies defects and discontinuities in terms of Acoustic Emission parameters. Sources of Acoustic Emission (AE) can be distinguished by their AE signature in terms of amplitude, Count and Energy. The severity can be quantified in terms of AE Parameters. In this paper an attempt is made towards predicting tensile failure load of Maraging Steel weldment with varying extents of notch thereby representing equivalent tight cracks as per Linear Elastic Fracture Mechanics (LEFM) design approach. Customized specimens were fabricated and notches were made using Electric Discharge Machining process. Tensile load has been applied to the test specimens with AE data acquisition. The AE distribution obtained from each specimen has been correlated to an equivalent Weibull distribution and represented in terms of weibull parameters. The significant Weibull parameters viz. Skewness (b value) and centroid of distribution curve (θ) are estimated. The distribution at a load of 85% of failure load is used for the prediction process. An empirical relation connecting Weibull parameters b, θ, b * θ, is proposed. It is observed that the product b * θ is linearly correlated to tensile failure load. On comparing results, predicted tensile failure load is closely matching to the recorded tensile failure load of the specimen. The average prediction capability of the proposed model is within 5–6%.