Research Article Analytical and Numerical Investigation of Lacing Wire Damage Induced Mistuning in Turbine Blade Packet Mangesh S. Kotambkar and Animesh Chatterjee Department of Mechanical Engineering, Visvesvaraya National Institute of Technology, Nagpur 440010, India Correspondence should be addressed to Mangesh S. Kotambkar; mskotamb@yahoo.com Received 15 August 2014; Accepted 12 November 2014; Published 9 December 2014 Academic Editor: Abdelkrim Khelif Copyright © 2014 M. S. Kotambkar and A. Chatterjee. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Investigations of modal parameters for a mistuned packet of turbine blades due to lacing wire damage are reported using analytical and numerical studies with a simplifed model. Te turbine blade is assumed to be an Euler-Bernoulli beam connected with a lacing wire which is modeled as a mass less linear elastic spring. Tus, the blade is considered as a continuous system and lacing wire as a discrete system. Te analytical results using Eigen value analysis are compared with numerical results obtained using commercial fnite element package. In real life situation, though not reported in the literature, it is the failure of lacing wire that occurs quite ofen compared to the turbine blade and acts as precursor to the subsequent blade damage if it goes undetected. Terefore, studying the modal parameters of the grouped turbine blades in the context of lacing wire failure becomes important. Te efect of variation of lacing wire location and stifness indicative of damage resulting in the loss of stifness on modal parameters is investigated. Te study reveals a lot of fundamental understandings pertaining to dynamic behavior of grouped blades compared to the stand-alone blade under the infuence of damaged lacing wire. 1. Introduction Turbine is the most widely used prime movers in power plants, turbo engines, and compressors in aircrafs and also in auxiliary turbo driven equipment such as turbo pumps. Tur- bine blade vibration and its failure under high cycle fatigue is an important area of research studies due to its critical applications. Te blade failures are mainly due to resonant stresses when one of the natural frequencies of blade-disk system matches the nozzle passing frequency. Design of these turbomachine blades thus critically depends on accurate understanding of the blade vibration characteristics under varied operating conditions. However, modeling and analysis of turbine blade vibration becomes quite complex due to continuously tapered and twisted cross-section and blade to blade dynamic coupling through lacing wire or shroud rings. Almost 50% of low pressure steam turbine blade failure is due to fatigue caused by vibration [1]. A turbine blade is a complex geometry having aerofoil shape with varying width and thickness along its length. Most of the early research works have been based on simplifed cantilever beam modeling where efects of root fexibility and crack in the stand-alone blade have been studied [2–9]. However, the dynamics of grouped blades is even more complex than a free stand-alone blade. Rao [10] has summarized the vibration behavior of turbine blades studied numerically and experimentally in the past in his book. In the recent past, research on turbine blade has focused on blades in a packet. Tere are many advantages of packeted turbine blades connected with lacing wire. For instance, resultant natural frequency increases with the number of blades in group and stifening due to interconnection of blades with the lacing wire. Smith [11] has made signifcant contribution in deter- mining the group frequencies and mode shapes of a blade packet. He also discussed the use of lacing wire in turbine blade groups. Ellington and McCallion [12] simplifed Smith’s analysis by using fnite diference calculus to the special case of blade group with a tie wire which joins the blade tips together. Prohl [13] used lumped parameter approach by consider- ing series of concentrated masses and concentrated stifness Hindawi Publishing Corporation Advances in Acoustics and Vibration Volume 2014, Article ID 164638, 16 pages http://dx.doi.org/10.1155/2014/164638