2. Worked as a Research Associate on a research contract in U.K. for a period of two years.

Department/University:

Department of Mechanical and Process Engineering, University of Sheffield

Mappin Street, Sheffield S13JD, U.K.

A View of Administrative Building of Sheffield University

Period: August 1987 to Dec. 1989

Project Title: An Investigation into the Stresses associated with Compressor and Turbine

   Blade/Disc Fixings

Project Supervisors:

Scope of Project

This is a collaborative research project between Rolls-Royce plc, Derby and Department of Mechanical Engineering, University of Sheffield, U.K. The ultimate aim of this two years investigation is to be able to calculate and interpret the stress distribution associated with the fir-tree root type of blade fixing used in aero-engine gas turbines. The fundamental problem is that of a series of loded projections and in particular, the lowest of the series of projections in such a fixing has proved to be the most difficult to analyze using simple design analysis procedures.

Typical Rolls Royce Engine: Adour Mk 804

The experimental stress analysis technique of photoelasticity is one of the most versatile methods available which enables both boundary and internal stresses to be determined.

The ultimate aim of the project is to investigate using detailed photoelastic analysis, the stress distributions around the fillet and contact zones of the fir-tree root type of blade fixing. Previous theoretical and photoelastic stress analyses of these fixings indicate that a maximum stress occurs in the root fillet radius but away from the contact zone. Failure evidence however shows that some cracks initiate from sites within the contact zone. The major aim of the project is to analyze the effect

of various parameters such as tooth geometry, load distribution along the flanks, and the frictional effects due to the relative motion between the teeth, on the stresses found in the fillet regions and the contact zones.

Extensive photoelastic investigations on simplified two-dimensional blade models with different flank angles (0°, 30° and 45°) and contact conditions were conducted. It was followed by a series of studies on the slices cut from a three dimensional stress-frozen bladed-disk photoelastic model (slices were supplied by Rolls Royce). A slice analyzer with high optical resolution was used in these investigations.

Typical results of the investigations are presented below:

Analysis on three-dimensional stress frozen model (Slice Analysis):

Publications based on the research project:

1. Kenny, B., Patterson, E. A., Said, M., Aradhya, K. S. S., 'Contact stress distributions in a turbine disc dovetail type joint - a comparison of photoelastic and finite element results', Strain, 27(1): 21 - 24.

2. B. Kenney, E.A. Patterson and K. S. S. Aradhya, 'Photoelastic analysis of dovetail joints for turbine blades', Proc., Conference on Applied Stress Analysis held at the University of Nottingham, Nottingham, N67 2RD, ENGLAND, during August 30-31, 1990.

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