Professor Arthur Lees
Professor Emeritus (Engineering)
Engineering
Telephone: (01792) 295514

Specialist Subjects:

Structural Dynamics
Rotor Dynamics
Condition Monitoring
Inverse Problems
System Identification

B.Sc., Ph.D., D.Sc., C.Eng., C.Phys., F.IMech.E, F.Inst.P.

Publications

  1. & Estimating unbalance and misalignment of a flexible rotating machine from a single run-down. , 967-989.
  2. Guidelines for the implementation of the CWELD and ACM2 spotweld models in structural dynamics. , 193-210.
  3. & Detection of severe sliding and pitting fatigue wear regimes through the use of broadband acoustic emission. , 85-98.
  4. & Estimating the static load on the fluid bearings of a flexible rotating machine from run-down data. , 1349-1368.
  5. Heat transfer and pressure drop in furrowed channels with transverse and skewed sinusoidal wavy walls. International Journal of Heat and Mass Transfer

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Research

A central theme of my professional career has been the application of physical principals to optimise the performance of equipment and plant. Apart from a brief period in the Electronics Industry, the industrial part of my experience has been in the power generation industry mainly the Central Electricity Generating Board and later with Nuclear Electric plc. The work could loosely be described as condition monitoring, but always with the emphasis firmly placed on the physics of processes giving rise to observed phenomena. The work I have carried out has focused largely, but not exclusively on vibration and in the early year the emphasis was on modelling. More recently the main challenge has been on inverse problems but of course this builds on the experiences of direct modelling. My change in emphasis reflects a general shift in direction in the study of vibration, and I can claim some influence on this shift.
 
Major problems were also being experienced at two Power Stations with main boiler feed pumps. Theses pumps had a gearbox which exhibited a number of failures. Despite a number of conventional investigations the problems were not understood. High fluctuations in transmitted torque were causing the gear teeth to loose contact, and the re-meshing of the gears gave rise to very high stresses which led to tooth failure. A model was developed from first principles to describe the torque variations as a function of speed. The model was described in terms of the geometric and material properties of the shaft components together with the declared manufacture tolerances of the gears. This model led to a successful redesign of the system and publication of the calculation method.
 
As a result of a number of investigations, I became acutely aware although modelling of systems is invaluable in gaining insight into a system’s behaviour, it is rare to have adequate data in practice. With this realisation, my interest in inverse problems began and this is an area in which I am still engaged. With this viewpoint I began to re-formulate the problem of machine vibration with flexible supports. The treatment results in a very large least square problem which can yield the effective properties of the supporting structure - properties which are required for accurate condition diagnosis. This formulation was published, but investigation of the detailed issues was suspended when I moved into a more managerial position.
 
I became Head of the Heat and Fluids section and was responsible for the work of 18 staff. This was the beginning of a nine year period during which I was managing the work through various re-organisations of between 12 and 30 staff. Throughout this period I had considerable managerial responsibility including the separation of part of my group to PowerGen in 1989 and later with the approach of privatisation of Nuclear Electric. During my time in the Power Industry, I was author/co-author of about 85 format reports, notes and memoranda in addition to 15 published papers.