Manufacturing Technology Today

K. I. V. Vandana ¹, K. V. Ramana ¹

Affiliations
1 Dept. of Industrial & Production Engg., Koneru Lakshmaiah College of Engineering, Vaddeswaram, P.O. Guntur Dt-522502, IN

Abstract

With the increasing demand for accurate engineering products, the control of surface texture has become vital. Surface roughness of machined parts need to be specified on the basis of their use and application environment. The geometrical and material properties of surface can significantly affect the friction, wear, fatigue and corrosion of that part. Hence evaluation of surface roughness and characterization of that surface has become essential for design, manufacturing and inspection. Many methods of measuring surface finish have been investigated ranging from simple touch comparator to sophisticated optical techniques. The latest technology of measuring surface roughness is the combination of optical techniques and computer vision systems. In this paper an attempt has been made to develop an experimental technique to measure the surface roughness based on the analysis of the intensity distribution of scattered light from the surface. For this purpose a low cost vision system is proposed. By impinging a laser beam at an angle on the machined surface, a random pattern of bright and dark regions known as speckle is observed. These speckle images are captured using charge coupled device (CCD) camera and are stored in digital format. Further a source code In C++ is developed to read the image data and to compute optical roughness values from stored images. Since the results obtained through this technique are encouraging, this method is well adapted for measurement of rough surface that fall within the range of engineering surface generated by common machining process like grinding, turning and milling. A few conclusions are drawn on the effectiveness of adopting the proposed system.

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M. Gopi Krishna ¹, K. V. Ramana ¹

Affiliations
1 Department of Mechanicai Engineering, K.L. College of Engg. Green fieids, Vaddeswaram, Guntur-522501, IN

Abstract

Present day state of the art in the design of turbo machines has given much scope to the flexible rotor bearing system. The most recurring problem in rotor dynamics is the excessive steady state synchronous vibration levels. Squeeze film dampers (SFD) are the essential components of high-speed turbomachines since they offer the advantage of dissipation of vibration energy and hence prevent rotor dynamic instabilities. A squeeze film damper is used between the bearing and its foundation to reduce the unbalance forces transmitted to the pedestal by introducing an additional damping and there by reduce the amplitude of vibration to acceptable limit. This work highlights the design and development of squeeze film dampers for high-speed machines in a more generic way. The first phase of the work involves the study of the effect of SFD on rotor dynamics based on the parameters like, damping ratio, logarithmic decrement and Transmissibility. A theoretical model Is generated incorporating the said parameters. The dynamic analysis, which is of two fold. Is carried out using ARMD software. The rotor dynamic effects are found without SFD and with SFD. The second phase of the work deals with experimental investigation on a journal-bearing test rig with SFD supports up to a speed of 1800 rpm. At the end, the vibrations obtained through theoretical analysis and experimental investigations are tabulated. It Is concluded that vibration levels are reduced using SFD for the specified optimum inputs.

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