• A K Nath

      Articles written in Sadhana

    • Laser power coupling efficiency in conduction and keyhole welding of austenitic stainless steel

      A K Nath R Sridhar P Ganesh R Kaul

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      Laser welding of thin sheets of AISI 304 stainless steel was carried out with high power CW CO2 laser. The laser power utilized in the welding process was estimated using the experimental results and the dimensionless parameter model for laser welding; and also the energy balance equation model. Variation of laser welding efficiency with welding speed and mode of welding was studied. Welding efficiency was high for high-speed conduction welding of thin sheets and also in keyhole welding process at high laser powers. Effect of pre-oxidization of the surface and powder as filler material on laser power coupling is also reported. The paper also discusses effect of microstructure on the cracking susceptibility of laser welds.

    • Melt flow characteristics in gas-assisted laser cutting

      B Tirumala Rao A K Nath

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      We present a study on laser cutting of mild steel with oxygen as an assist gas. We correlate the cut surface quality with the melt film thickness. We estimate the optimum pressure required for melt ejection under laminar flow regime. The thickness of melt film inside the kerf is estimated using mass balance and the shear force acting on the cutting front assuming melt flow profile as linear. The dependence of melt film thickness on gas pressure, cutting velocity and work piece thickness is estimated and compared with experimental results.

    • Design and development of long-period grating sensors for temperature monitoring

      Smita Chaubey Purushottam Joshi Manoj Kumar Rajesh Arya A K Nath Sanjay Kher

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      Long Period Gratings (LPGs) have been developed using carbon dioxide laser in a standard optical fibre. LPGs with a periodicity of 600 𝜇m and grating length of 24 mm have been inscribed on standard single mode fibre. Such gratings have been used in designing temperature sensors and temperature is monitored up to 80°C. The sensitivity of such type of sensor is 0·06 nm/° C where as for standard Fibre Bragg Grating (FBG) it is 0·011 nm/°C. The LPG performance is also evaluated after 𝛾-ray irradiation for total dose of 5 KGy and has not shown any effect on transmission spectrum.

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