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Title: The effect of midspan shroud constraint on vibration of compressor blade systems
Author: Hall, R. M.
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 1968
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This thesis is concerned with the vibration of a simplified compressor blade system which is stiffened by the introduction of a midspan shroud, or snubber, constraint. The initial investigation is concerned with the effect of different types of snubber interface constraint, namely: 1) Dry friction rubbing at the snubber interface. 2) Clearance at the snubber interface. 3) Viscoelastic shear joint at the snubber interface. The results of resonance tests carried out on a single blade for each type of constraint showed the viscoelastic shear joint to stiffen the structure, while giving higher damping than that of the other interface conditions. A more comprehensive experimental and theoretical investigation is carried out on this type of constraint on a single blade. The complex modulus model is used to describe the viscoelastic material properties which are treated as a function of frequency, and justification is given for its use in free vibration. The results show optimum positions for the snubber for maximum stiffening and damping and that they vary from mode to mode. The results also reveal that heavy damping may be obtained if the parameters are optimised correctly. The experiments verify the theoretical work satisfactorily. The investigation is extended to the study of a batch of five blades which are connected by a viscoelastic shear joint at the snubber interface. The theoretical analysis however fails to predict one of the five basic modes. The structure exhibits heavy damping with close natural frequencies. A survey of the methods for separating the response of individual modes from the total transient response of a structure, is carried out. It was found to be impossible to estimate the frequency anddamping for one of the heavily damped modes by any of the available techniques. Correlation between experimental and theoretical results is acceptable.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available