For his outstanding contributions to tribology, particularly in the field of contact mechanics.
Kenneth Langstreth Johnson (born 1925) was educated at Barrow Grammar School and at the University of Manchester, where he obtained his BSc degree in 1944 and his MSc(Tech) in 1947. After five years in industry with Rotol Ltd, on vibration and propeller research, he was appointed Assistant Lecturer at the Manchester College of Technology (now UMIST), where he received the degree of PhD for his research project on “Surface Interactions between Elastically Loaded Bodies under Tangential Forces”, which marked the beginning of his interest in contact mechanics. In 1954 he moved to Cambridge University, where he has remained, being appointed Professor of Engineering in 1977.
Professor Johnson’s work in the field of frictionless and frictional contact of unlubricated deformable bodies is both original and eminent. From 1958 to 1964 he conducted experiments on rolling contact with creep and spin. The quality of these pioneering experiments was of such excellence that it has never been surpassed. He also discovered the spin effect in rolling contact. Professor Johnson’s experiments have decisively influenced the theoretical-numerical work in this area, as they provide the indispensable background of experience which is so necessary for the theoretician.
Together with Bentall, Johnson conducted numerical work on two-dimensional rolling contact, in which they attacked the problem of the stress at the interface of two elastically dissimilar rollers, and of an elastic strip between them and produced a complex solution to the problem of the elastic strip that to date has never been calculated more perfectly.
Professor Johnson’s qualitative-analytical work, in which he proposes simple laws for complex problems, is well recognised. Areas in which he has given approximations include his theories of plastic rolling, shake-down in rolling contact (particularly notable) and adhesion in contact due to surface energy dominated phenomena.
In 1967, Professor Johnson began research into the phenomena associated with lubricated rolling contact traction. The ultimate result of this research is a constitutive equation for the fluid film referred to as the Johnson-Tevaarwerk Model; it is used by many of the major industries, involved in the design and development of rolling element bearings, transmissions and traction drives. In parallel with this work, Professor Johnson published papers on the regimes of elastrohydrodynamic lubrication, the lubrication of rough spheres, shake-down limits of plastic contacts and many others of great interest to the tribology world, earning him great respect from researchers all over the world.
Another major field of study in tribology has been the investigation of lubricant rheology in concentrated contacts. This study has enabled elastrohydrodynamic theory (which determines the overall film shape and pressure distributions in highly stressed conjunctions) to be utilised with confidence in the predictions of traction coefficients and power loss.
Professor Johnson’s other contributions in tribology research include studies of surface interactions involving both elastic and plastic contact; his work on the contact between railway wheels and tracks in recent years is widely recognised internationally. All his contributions are marked by remarkable clarity of thought and the ability to identify the essential features of complex problems involving interacting surfaces.
Professor Johnson has published a large number of major papers, especially in the Proceedings of The Royal Society and The Institution of Mechanical Engineers. He received an IMechE James Clayton Prize in 1961 for his paper on “Energy Dissipation at Spherical Surfaces in Contact” and another in 1969 for his paper on “Residual Stresses in Rolling Contacts”. In 1982 he gave a Memorial Lecture at The Institution of Mechanical Engineers on “One Hundred Years of Hertz Contact” in which he outlined the theory of contact mechanics proposed by Heinrich Hertz in 1882 and discussed its application to mechanical engineering pro9blems during the following hundred years. Professor Johnson’s major interests in contact mechanics are fully reflected in his outstanding book of that title, published early in 1985, a book that is likely to remain a basic work of reference for many years to come.
Professor Johnson has been a Fellow of Jesus College, Cambridge since 1957. In 1982 he was made a Fellow of The Royal Society and in 1983 the American Society of Lubrication Engineers presented him with their national award in recognition of his outstanding contribution to tribology.
Professor Johnson’s approach is engineering science at its best, involving simple physical assumptions, thorough and penetrating analysis and, where necessary, critical and elegant experiments. It is certain that his work in contact mechanics will be of permanent importance, and in this area he is internationally regarded as an outstanding figure.
Professor Kenneth Langstreth Johnson is a most worthy recipient of tribology’s highest award, the Tribology Gold Medal.