Defence Research and Development Laboratory

About: Defence Research and Development Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Turbulence & Mach number. The organization has 404 authors who have published 420 publications receiving 4183 citations. The organization is also known as: DRDL.

Prediction and optimization of weld bead geometry for electron beam welding of AISI 304 stainless steel

Abstract: Electron beam welding, though considered a sophisticated welding process, still requires the operator to first carry out several trial welds to find the right combination of welding parameters based on intuition and experience. This archaic method is often unreliable, leading to unproductive manufacturing lead time, man hours, quality control tests, and material wastage. The current study eliminates this “trial and error” method by providing a reliable model which can predict the right combination of weld parameters to achieve a high-quality weld. Beads on plate welds were carried out on AISI 304 stainless steel plates using a low-kilovolt electron beam welding (EBW) machine. A model that can predict weld bead geometry and provide optimized output for minimum weld area condition without compromising on weld quality was developed. Experimental data were collected as per full factorial design of experiments, and the levels for each input parameter were established through pilot experiments. A multivariate regression analysis has been conducted to establish a relationship between four weld input parameters (three levels each) and four weld bead responses. Response surface methodology (RSM) has been used to study the interrelationship between input parameters and their effect on each response variable. Further, minimization of weld cross-sectional area was done using genetic algorithm for maximum penetration and minimum weld area condition. The optimized mathematical model convincingly establishes that the focusing current is a significant input parameter with very high influence over the weld bead geometry. Extensive material characterization and mechanical tests have been carried out to validate the regressed input-output relationship and the optimized mathematical model.

Electron-beam welding of high-entropy alloy and stainless steel: microstructure and mechanical properties

Abstract: An autogenously dissimilar Al0.1CoCrFeNi-high entropy alloy/stainless steel (i.e., AISI 304) weld joint was produced by an electron-beam welding technique. The weld metal followed mode A of solidif...

Strain gradient torsional vibration analysis of micro/nano rods

Abstract: Fabrication, characterization and application of micro-/nanorods/wires are among the hottest topics in materials science and applied physics. Micro-/nano-rod-based structures and devices are developed for a wide-ranging use in various fields of micro-/nanoscience (e.g. biology, electronics, medicine, optics, optoelectronics, photonics and sensors). It is well known that the structure and properties of micro/nano rods depend greatly on their environment of application. Therefore, in this paper, torsional vibration of microbars is formulated based on the strain gradient theory to study the vibrational behavior at micro/nano scale. The strain gradient theory is a non-classical theory capable of capturing the sizeeffects. The governing equation and both the classical and the nonclassical boundary conditions are derived employing the Hamilton’s principle. In the free-vibration case, the characteristic equation is derived and solved analytically. The torsional free-vibration behavior of a fixedfixed strain gradient microbar is investigated and the results are compared to those evaluated by the classical and modified couple stress theories noted that the two latter theories are special cases of the strain gradient theory. The effects of the length and the radius of the micro rods on the various modes of torsional natural frequencies are investigated in detail. The results of this study can be useful in the design and analysis of the next generation micro-electro-mechanical-systems and nano-electromechanical-systems which uses the torsional vibration properties of the micro-/nano-rods.