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|Title: ||Design of high power ultrasonic manufacturing tools : a systems approach|
|Authors: ||Smith, Andrew Charles|
|Issue Date: ||1997|
|Publisher: ||© Andrew Charles Smith|
|Abstract: ||High power ultrasonics is currently under-utilised as a manufacturing technology.
The potential of the technology in areas such as welding, fastening and cutting has
not been fully realised because the beneficial mechanisms available in ultrasonic
systems are not always understood and therefore are not fully utilised. The
empirical approach to much of the design process often results in unreliable
operating performance in customised tools. The aim of the research reported in this
thesis, is to develop a structured approach to the design and optimisation of high
power ultrasonic systems. Furthermore, this research demonstrates how the use of
such an approach can benefit the understanding of the fundamental ultrasonic
process, which in turn leads to more informed system design criteria.
Initially a combined analytical and experimental approach is proposed and is
demonstrated using an ultrasonic welding tool as the focus. Finite element analysis
is used to predict the vibration behaviour of the welding tool and models are
validated by experimental vibration analysis techniques; electronic speckle pattern
interferometry and experimental modal analysis. It is determined that the
problematic behaviour of the welding tool results from high modal density and
modal coupling, both of which are common problems associated with high power
ultrasonic tooling. Sensitivity analysis with degree of freedom ranking using finite
element analysis, detunes the coupled flexural vibration from the operating
frequency of the system, successfully isolating the required response. The approach
is extended to ultrasonic fastening, whose performance is known to be influenced
greatly by fastener geometry. The technique is applied to develop a series of
fasteners, each having an alternative critical vibration parameter during insertion.
Insertion tests demonstrate that a particular torsional mode family promotes
improved insertion performance and resulting join quality.
Finally the approach is extended to a novel ultrasonic cutting application. The
potential of the cutting process is assessed using finite element analysis to verify
the cutting mechanism as one of controlled crack propagation which is dependent
on the vibration characteristics of the cutting blade. Using a combination of
vibration analysis and fracture analysis, the ultrasonic cutting process is optimised
for blade mode of vibration, leading to improved cutting performance and control.
A significant advance is made in the understanding of the fundamental
mechanisms of ultrasonic cutting and in cutting system design.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Mechanical, Electrical and Manufacturing Engineering)|
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