Kumar Chandan, Saha P and Mishra P K, "Laser Bending of Micro tubes", All India Manufacturing Technology Design and Research Conference, Dec-2004.
Abstract: Laser bending is a non-contact flexible forming technique. It is the preferred to conventional bending techniques due to the high level of accuracy, repeatability and high degree of control offered by the process. In laser tube bending process the stresses are generated due to heating, which eventually leads to plastic deformation. The compressive plastic strain developed during the process causes the bending of the tubes in the direction of the laser beam. Thin-tube bending is rapidly finding applications in MEMS, medical and other technological fields. However, the process has yet not been studied in detail. In order to have better understanding of the parameters that govern the process of laser bending of thin tubes, experiments have been conducted to bend them using a pulsed Nd-YAG laser. The experimentations necessitated design and fabrication of a set up to facilitate the bending. The parameters involved in the bending of thin tubes have been studied in detail. The experimental results have been compared with the results obtained by simulation of the experiments, under the same conditions, by both analytical and numerical approach.
Chandan Kumar, P. Saha and P. K. Mishra, "Analytical solution for the three dimensional Temperature Distribution in a hollow cylinder in the presence of an aerial heat source", communicated to the International Journal of Thermal Sciences
Abstract: Temperature distribution plays a major role in the forming of tubes. In this work the exact solution to three dimensional transient temperature distribution in a hollow cylinder in the presence of an areal heat source has been determined. Heat flux prescribed on the outer surface has been expressed in terms of fourier series. Conduction and natural convection have been considered to be the primary heat transfer modes.
Abstract: Purpose - To calculate the volume deviation between a CAD model and built-up part in 5-axis laminated object manufacturing employing direct slicing with first-order approximation. Design/methodology/approach - It is proposed here that the deviation between the CAD model and the built-up part, which is normally calculated as a linear dimension in specific 2D sections of the CAD model, be treated as a volume (as it actually is), for higher accuracy in subsequent calculations. An algorithm has been developed and implemented for identification and calculation of volume deviation, considering all possibilities. Findings - It has been conclusively shown that volume deviation consideration results in improved feature recognition and less approximation. Research limitations/implications - Increase in complexity of the CAD model leads to a considerable increase in the volume deviation computation time. Future research in this area would focus on optimization and calculation of the slice heights based on volume deviation. Practical implications - Calculation of volume deviation would help eliminate the loss of intricate features in a complex surface and thus improve feature recognition. Slice height calculations based on volume deviation would reduce the deviation between the actual model and the built-up part. Originality/value - A new method has been developed for the calculation of volume deviation that could be implemented in the rapid prototyping software packages so as to build prototypes with higher accuracy.
Abstract: Though fusion welding is the most versatile process of joining of materials, it is fraught with change in shape and configuration of the fabricated structures due to distortion. There are some common guidelines to combat distortion of weldments. Considerable amount of literature is available on controlling distortions of butt joints but the same on T-joints is rather meager. In the present investigation, single fillet T-joints were made of mild steel plates using manual metal-arc welding process. A number of parameters including state of the base plate (such as, pre-welding stress relieving, preheating), size of flux-coated electrodes, size of the fillet weld, etc. were considered. Factorial design of experimental technique was adopted to optimize the number of experiments performed. Useful conclusions of practical significance have been drawn.