Informatics Publishing Limited

V. Bharathi ¹, M. Ramachandra ¹, S. Srinivasa ¹, P. Sampathkumaran ², S. Vynatheya ², Seetharamu S. ²

Affiliations
1 Department of Mechanical Engineering, BMS College of Engineering, Bangalore-560019, IN
2 Materials Technology Division, Central Power Research Institute, Bangalore – 560 080, IN

Abstract

The comparative performance of plain Glass-Epoxy (G-E) system with graphite(2.5wt.%) as filler has been reported for slide wear and friction behavior using pin-on-disc setup under varying loads and sliding velocities. This material is intended for use in coal handling systems. Besides slide wear and coefficient of friction (μ) measurements, examination of worn surface features by scanning electron microscope has been carried out to support the slide wear data. The slide wear data reveal that with increase in sliding speed, wear loss of both G-E composite and G-E plain system increase. Further it is seen that the G-E graphite filled system shows the least wear loss compared to plain G-E system. This trend is observed for all the three loads employed in this work. It is observed that the graphite bearing and plain G-E samples display a rise in the value of μ, when both load and sliding velocity are increased. The coefficient of friction of graphite G-E shows the least compared to plain G-E system irrespective of the load and the sliding velocity employed.

Keywords

Glass-epoxy (G-E), Pin-on-disc, Sliding wear, Graphite filler, SEM observations

Full Text

     

K. Narasimha Murthy ¹, P. Sampathkumaran ², Seetharamu S. ², R. K. Kumar ²

Affiliations
1 Department of Mechanical Engineering, CMR Instituteof Technology, Bangalore, IN
2 Central Power Research Institute, Bangalore - 560 010, IN

Abstract

The influence of 2.0% nickel on thin and section permanent molded austempered ductile iron samples were investigated for abrasion and erosion behavior. The section sizes of samples were varied at two levels viz. 25 mm and 50 mm. Wind turbine hubs which were subjected to wear and erosion were made from thin and thick section PMADI castings. The austempering temperature and time were optimized for improved wear behavior and strength at 3000 C for 60 mins. Nickel additions showed about 7% improvement in the wear resistance of thin section PMADI samples over unalloyed PMADI samples. For the purpose of comparison, sand-cast austempered ductile iron was also evaluated for abrasion, erosion resistance. Thin section (25 mm) PMADI samples subjected to austempering at 3000 C for 60 mins showed improved abrasion and erosion behavior in addition to higher strength values over thick section (50 mm) PMADI and sand cast ADI samples. Further these data were analyzed with structure property correlation and were well supported by light photomicrographs.

Keywords

PMADI, Thin/thick section, Abrasion\erosion and Wind turbine hubs

Full Text

     

B. Gurudatt ¹, S. Seetharamu ², P. Sampathkumaran ³, Vikram Krishna ⁴

Affiliations
1 Professor, Dept of Mechanical Engg., Bangalore Institute of Technology, Bangalore-560004, IN
2 Additional Director, MTD, Central Power Research Institute, Bangalore-560080, IN
3 Joint Director, MTD, Central Power Research Institute, Bangalore-560080, IN
4 Research Associate, RSOP Project of CPRI (Govt. of India), Bangalore-560004, IN

Abstract

Vibration is the default state of all mechanical systems that causes them to possess a natural frequency. The significance of natural frequency cannot be emphasised enough, considering the fact that its study is essential in averting resonance which causes violent swaying motions and catastrophic failures in improperly constructed structures. In case of rotating structures, the study of natural frequency is incomplete without the understanding of spin softening. This paper presents an ANSYS based analysis to study natural frequency variation due to spin softening, but in a faster and more accurate way than conventional GUI-based ANSYS analysis. The conventional GUI based ANSYS procedure is a laborious time consuming process, with the user having to perform multiple iterations of model analysis involving different rotational velocities to examine the variation of natural frequencies of the system. Through this paper, a novel way has been suggested to bring down the time and effort involved in such a study by using an advanced ANSYS feature called ANSYS Parametric Design Language (APDL). The results obtained have been found to validate spin softening.

Keywords

Finite Element Method, ANSYS Parametric Design Language, Natural Frequency, Spin Softening, Vibrations, Nelson Rotor.

Full Text

     

B. Gurudatt ¹, S Seetharamu ², P. Sampathkumaran ², Vikram Krishna ³

Affiliations
1 Department of Mechanical Engineering, Bangalore Institute of Technology, Bangalore-560004, IN
2 Central Power Research Institute, Bangalore-560080, IN
3 M S Ramaiah Institute of Advanced Studies, Bangalore, IN

Abstract

Resonance is a common thread that runs through almost every branch of engineering. Yet, this phenomenon often goes unnoticed, silently resulting in inconveniences, such as causing a bridge to collapse or a helicopter to fl y apart, to name a few. It is, therefore, of utmost importance to avert resonance, for which determining the frequency of the system becomes indispensible. In complex rotating structures, as one considered in this paper, theoretical determination of frequency is as diffi cult and laborious as a task can be. Finite element analysis has proven to be an effective tool to handle such a task. Resonant vibrations incited by the running speed harmonic excitations, steam impinging frequency, engine order excitations are fundamental causes for failure of turbine components. The mainstream discipline that is encompassed by this paper is the modal analysis. Modal analysis is performed to estimate the critical speeds and study the mode shapes of the bladed rotor disc under prestressed condition.

Keywords

Resonance, Steam turbines, Blade vibration, Disc vibration, Finite Element Analysis (FEA).

Full Text

     

B. Suresha ¹, P. Sampathkumaran ², S. Seetharamu ², Kishore ³

Affiliations
1 Department of Mechanical Engineering, National Institute of Engineering, Mysore - 570 008, IN
2 Materials Technology Division, Central Power Research Institute, Bangalore - 560 080, IN
3 Department of Materials Engineering, Indian Institute of Science, Bangalore - 560 012, IN

Abstract

Woven fabric reinforced polymer composites are attracting the attention of material scientists in recent years in view of enhancement in physical and mechanical properties as well as ease in processing. Though woven fabric type and lay out of composite is known to control the properties, the information on the tribo-performance of the woven fabric reinforced vinyl ester composites in the literature is scanty. Hence, the present investigation focuses on the vinyl ester based composite reinforced with glass fibers in one case and carbon fibers in the other case. They were made by vacuum assisted resin transfer moulding process. Further, the samples were characterized for three-body abrasive wear behaviour using dry sand rubber wheel abrasion tester with two different abrasives (silica sand and quartz). The wear data revealed that the C-V composite showed lower abrasion loss compared to G-V composite. The scanning electron microscopic pictures depicting the worn surface features supported the wear data.

Keywords

Woven Fabric Reinforced Vinyl Ester Composites, Abrasives, Three-Body Abrasive Wear, Scanning Electron Microscopy.

Full Text

     

P. Sampathkumaran ¹, S. Seetharamu ¹, C. Ranganathaiah ², P. K. Pujari ³, Kishore ⁴

Affiliations
1 Materials Technology Division, Central Power Research Institute, Bangalore-560080, IN
2 Department of Studies in Physics, University of Mysore, Mysore-570006, IN
3 Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai-400085, IN
4 Department of Materials Engineering, Indian Institute of Science, Bangalore-560012, IN

Abstract

The wear-resistant high chromium (Cr: 16–19 %) iron alloyed with 5 % and 10 % manganese (Mn) was produced in metal and sand moulds by induction melting technique. The erosion resistance, hardness and microstructure were evaluated both in the as-cast and heat, treated conditions. The advanced nondestructive test (NDT) methods, namely Positron Lifetime Spectroscopy (PLS) and Doppler Broadening annihilation radiation (DBAR) studies, using variable energy positron beam were made use of to study the infl uence of metallurgical parameters on the defect sensitivity in the bulk and surface of the alloy. The data reveals that as the mould type is changed from metal to sand, the hardness decreases irrespective of the sample condition (i.e. as-cast or heat treated), whereas the erosion volume loss shows an increasing trend. The light and scanning electron microscopies give good support to these data fi ndings. It is observed that faster the cooling rate (metal mould), fi ner is the carbide size precipitation on the surface of the sample. The PLS data reveals that the defect size and its concentration are higher for sand mould alloy compared to metal mould. Reasons for lower erosion loss and fewer defects of smaller sizes in metal mould are attributed to faster heat transfer in the metal mould compared to the sand mould. Further, heat treatment of the samples yielded spherodization of carbides in the matrix and some of the defects seem to have been annealed out leaving only fewer defects of smaller size in the alloy. The S-parameter profi les of 10 % Mn both in AC and HT samples are almost identical indicating near absence of any modifi cation of defect structure near the surface following heat treatment in 10 % Mn sample, while 5 % Mn samples exhibit less defect concentration both at the surface as well as in bulk which agrees with the PLS results. Hence, the 5 % Mn bearing metal mould sample in the heat-treated condition is preferred choice as it shows higher hardness, lower erosion loss as well as least defect concentration with smaller defect sizes. Based on this investigation, a good correlation among erosion loss, DBA and PLS data has emerged.

Keywords

Cr–Mn cast iron, Metal mould, Sand mould, As-cast, Heat treatment, Hardness, Erosion, Positron lifetime spectroscopy, Doppler broadening spectroscopy.

Full Text