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Walace Hirst (1916–1997)
WEAR ELSEVIER
Wellr 2 12 ( I9971268-269
Wallace Hint (19164997) The death of Wallace Hirst on 27th June this year is a pertinent reminder of the strength of tribology in Britain in the years before the word was invented. After graduating in physics from Birmingham University with c PhD in 1938 (at the age of 22), he joined Philip Bowden in Cambridge, taking over a research grant just relinquished by David Tabor. During the war he was worked for the British Coal Utilisation Association, but the year in Cambridge had fired his interest in the contact of surfaces and imbued him with the importance of surfax roughness and ‘real’ &area of contact. The opportunity came in 1947 to pursue this interest when he was invited to set up a Surface Physics group at the new longterm research laboratory of the AEI company, under the inspiied direction of T.E. Allibone FRS. It was situated, away from the manufacturing plants, in Aldermaston in rural Berkshire (not to be confused with the Atomic Weapons Establishment). Hirst recruited a team, mainly educated in physics, whose names rapidly came to dominate publications on contact, friction and wear: Archard, Cocks, Halliday, Hamilton, Kerridge, Lancaster and Welsh. Hirst was closely involved in all their activities, but encouraged them to publish under their own names. While maintaining the importance of surface roughness, Hirst and his colleagues were sceptical of Bowden’s insistence on fully plastic deformation and adhesion of asperities. Ciose contact with the engineering activities of the company, notably heavy marine gearing, focused attention on steel as a material, intentionally or unintentionally contaminated with grease, in repeated sliding contact. Archard argued &at, under these circumstances, asperities would ‘run in’ or, as we say now, ‘shakedown’ to a predominantly elastic state of stress. He was the first to show that, in a multi-asperity contact, plastic deformation was not a necessary requirement for the real contact area to be proportional to the load and that the intensity of contact stress was proportional to the s10pe of the asperities. The early work on wear of steel and other ‘practical’ metals with Hirst, Kerridge, Lanczter and Welsh led to Archard’s ubiquitous wear law, and to the concepts of ‘mild’ and ‘severe’ wear and wear transitions. My association with the group followed the discovery by Crook and Welsh in 1959 of the accumulation of plastic strain in repeatedrolling and sliding contact which, as a mechanism ( ‘ratchetting’ ) of wear and contact fatigue, has been one of my continuing interests. Along with F.T. Barwell of the National Engineering Laboratory, Hirst recognised that gear teeth were effectively lubricated under conditions of load and speed denied by contemporary lubrication theory which neglectedthe contactdeformation.Hirst’s group set about this problem with energy, both experimentally and theoretically. Crook’s four papers in Phil. Tmzs. Ruy. Sot. ( 1958-63) are classics. They showed that the film thickness was established by conditions at the inlet; not only the thickness, but also the shape of the film was measured: the temperature in the nip was estimated by an analysis which is still used today. by developing a novel 4disc machine Crook was able to measure frictional traction as a function of slip between the surfaces of the discs. Meanwhile the elastohydrodynarnic line contact problem was attacked, first using an analogue computing technique comprising an electrical resistance network and then by using an early digital computer housed at AEI Manchester. The results were published in a much neglected paper ( Archard, Gair & Hirst, 196 I ), three years after Dowson & Higginsons’ pioneering paper, but probably the first to employ a fully automated iterative procedure. In the early 60s the AEI company found itself in F.nanciaI difficulties, eventuaily to be taken over by GEC. The Al&rmaston Laboratory was closed. Hirst’s group scattered to find employment: Hirst and Hamilton to Reading University, Archard to Leicester University, Lancaster to the Royai Aircraft Establishment and some to different parts of the company: Crook to become Chief Mechanical Engineer of the Turbine Division. The demise of the AEI laboratory and, at the same time, that of Barwell’s Lubrication Division at NEL acted as a significant stimulant to the enquiry being conducted at that time into matters relating to lubrication and wear, which led to coining the name ‘tribology’ and to the publication of the Jest Report in 1966. Hirst’s own account ’ of the work of the group provides a case history of a very successful industrial long-term research group which would make instructive reading for some of today’s Technical Directors. When Hirst moved to Reading University there was no engineering and little applied science. His appointment was to a new Department of Applied Physical Sciences which eventually became Engineering. The establishment of a small but ’ W. Hirst, ‘The AEI long-termresearchlaboratory:from surfacephysicsto uibolo~y’, Tritdugy It~remariond, 28,245-2X Elsevier ScienceS.A.
I995
Obinkury / Weur 212 (I 997) 26&t&J
thriving Department of Engineering Science is in large measure due to Wallace Hirst. He and Hamilton were at first occupied which setting up new courses, but eventually were able to build up a team to funher research in tribology. ’ Some work on contact and wear was restarted and notable contributions made on the wear of diamond (with Crompton and Howse) and on criteria to predict the onset of scuffing in conditions of boundafiy lubrication (with A,E. Hollander), a paper which is still frequently quoted. However, Hirst’s principal concern during his time at Reading was to reconcile Crook’s measurements of EHD traction with lubrication theory. We in Cambridge had already shown that Crook’s hypothesis, that the observed traction could be accounted for by the effect cf frictional heating on Newtonian viscosity, could not be sustained at higher pressure. This
was strong evidence for non-Newtonian behaviour of the lubricant, and it was Hirst who showed that the shear thinning revealed by the traction experiments could be explained by the Eyring theory of fluid Pow. From then an there was close collaboration between Hirst and his student/research assistant A.J. Moore in Reading and ourselves in Cambridge. In spite of its dubious physical basis and more recent debates (not wholly resolved) about changes of state at the highest pressures, the Eyring theory ctoes provide a self-consistent model of the transition in viscosity with increasing pressure; from a thermally activated process at low pressure (varying exponentially with pressure) to a stress driven process (varying proportionally with pressure). Hirst formally retired at the end of 1980. He continued to supervise research students for a white but, regarding the EHD traction probfem to be largely solved, felt that he could retire to the country and indulge in his many hobbies, notably gardening and playing the organ. He finished with a bang, being awarded (with J. Richmond) in 1988 the I.Mech.E. Thomas Bernard HaIl FVizc.He is survived by his wife, Muriel, whom he met during his time at Reading University and happily married in 1970. To his colleagues, on the other hand, Hirst was a very shy and private person with whom it was difficult to become intimate or to feel completely at ease. He did not enjoy conferences and did not perform well at the few he attended. This must have contributed to what some of us, who worked with him and read his papers with admiration, regard as a lack of recognition of his major contribution to the subject of tribology. K.L* Johnson Cambridge. August, 1997.
z W.
Hirst. Twenty
five years
af Tribology’
Tribology
hremariorraf,
28.23-27,
1995.
Wellr 2 12 ( I9971268-269
Wallace Hint (19164997) The death of Wallace Hirst on 27th June this year is a pertinent reminder of the strength of tribology in Britain in the years before the word was invented. After graduating in physics from Birmingham University with c PhD in 1938 (at the age of 22), he joined Philip Bowden in Cambridge, taking over a research grant just relinquished by David Tabor. During the war he was worked for the British Coal Utilisation Association, but the year in Cambridge had fired his interest in the contact of surfaces and imbued him with the importance of surfax roughness and ‘real’ &area of contact. The opportunity came in 1947 to pursue this interest when he was invited to set up a Surface Physics group at the new longterm research laboratory of the AEI company, under the inspiied direction of T.E. Allibone FRS. It was situated, away from the manufacturing plants, in Aldermaston in rural Berkshire (not to be confused with the Atomic Weapons Establishment). Hirst recruited a team, mainly educated in physics, whose names rapidly came to dominate publications on contact, friction and wear: Archard, Cocks, Halliday, Hamilton, Kerridge, Lancaster and Welsh. Hirst was closely involved in all their activities, but encouraged them to publish under their own names. While maintaining the importance of surface roughness, Hirst and his colleagues were sceptical of Bowden’s insistence on fully plastic deformation and adhesion of asperities. Ciose contact with the engineering activities of the company, notably heavy marine gearing, focused attention on steel as a material, intentionally or unintentionally contaminated with grease, in repeated sliding contact. Archard argued &at, under these circumstances, asperities would ‘run in’ or, as we say now, ‘shakedown’ to a predominantly elastic state of stress. He was the first to show that, in a multi-asperity contact, plastic deformation was not a necessary requirement for the real contact area to be proportional to the load and that the intensity of contact stress was proportional to the s10pe of the asperities. The early work on wear of steel and other ‘practical’ metals with Hirst, Kerridge, Lanczter and Welsh led to Archard’s ubiquitous wear law, and to the concepts of ‘mild’ and ‘severe’ wear and wear transitions. My association with the group followed the discovery by Crook and Welsh in 1959 of the accumulation of plastic strain in repeatedrolling and sliding contact which, as a mechanism ( ‘ratchetting’ ) of wear and contact fatigue, has been one of my continuing interests. Along with F.T. Barwell of the National Engineering Laboratory, Hirst recognised that gear teeth were effectively lubricated under conditions of load and speed denied by contemporary lubrication theory which neglectedthe contactdeformation.Hirst’s group set about this problem with energy, both experimentally and theoretically. Crook’s four papers in Phil. Tmzs. Ruy. Sot. ( 1958-63) are classics. They showed that the film thickness was established by conditions at the inlet; not only the thickness, but also the shape of the film was measured: the temperature in the nip was estimated by an analysis which is still used today. by developing a novel 4disc machine Crook was able to measure frictional traction as a function of slip between the surfaces of the discs. Meanwhile the elastohydrodynarnic line contact problem was attacked, first using an analogue computing technique comprising an electrical resistance network and then by using an early digital computer housed at AEI Manchester. The results were published in a much neglected paper ( Archard, Gair & Hirst, 196 I ), three years after Dowson & Higginsons’ pioneering paper, but probably the first to employ a fully automated iterative procedure. In the early 60s the AEI company found itself in F.nanciaI difficulties, eventuaily to be taken over by GEC. The Al&rmaston Laboratory was closed. Hirst’s group scattered to find employment: Hirst and Hamilton to Reading University, Archard to Leicester University, Lancaster to the Royai Aircraft Establishment and some to different parts of the company: Crook to become Chief Mechanical Engineer of the Turbine Division. The demise of the AEI laboratory and, at the same time, that of Barwell’s Lubrication Division at NEL acted as a significant stimulant to the enquiry being conducted at that time into matters relating to lubrication and wear, which led to coining the name ‘tribology’ and to the publication of the Jest Report in 1966. Hirst’s own account ’ of the work of the group provides a case history of a very successful industrial long-term research group which would make instructive reading for some of today’s Technical Directors. When Hirst moved to Reading University there was no engineering and little applied science. His appointment was to a new Department of Applied Physical Sciences which eventually became Engineering. The establishment of a small but ’ W. Hirst, ‘The AEI long-termresearchlaboratory:from surfacephysicsto uibolo~y’, Tritdugy It~remariond, 28,245-2X Elsevier ScienceS.A.
I995
Obinkury / Weur 212 (I 997) 26&t&J
thriving Department of Engineering Science is in large measure due to Wallace Hirst. He and Hamilton were at first occupied which setting up new courses, but eventually were able to build up a team to funher research in tribology. ’ Some work on contact and wear was restarted and notable contributions made on the wear of diamond (with Crompton and Howse) and on criteria to predict the onset of scuffing in conditions of boundafiy lubrication (with A,E. Hollander), a paper which is still frequently quoted. However, Hirst’s principal concern during his time at Reading was to reconcile Crook’s measurements of EHD traction with lubrication theory. We in Cambridge had already shown that Crook’s hypothesis, that the observed traction could be accounted for by the effect cf frictional heating on Newtonian viscosity, could not be sustained at higher pressure. This
was strong evidence for non-Newtonian behaviour of the lubricant, and it was Hirst who showed that the shear thinning revealed by the traction experiments could be explained by the Eyring theory of fluid Pow. From then an there was close collaboration between Hirst and his student/research assistant A.J. Moore in Reading and ourselves in Cambridge. In spite of its dubious physical basis and more recent debates (not wholly resolved) about changes of state at the highest pressures, the Eyring theory ctoes provide a self-consistent model of the transition in viscosity with increasing pressure; from a thermally activated process at low pressure (varying exponentially with pressure) to a stress driven process (varying proportionally with pressure). Hirst formally retired at the end of 1980. He continued to supervise research students for a white but, regarding the EHD traction probfem to be largely solved, felt that he could retire to the country and indulge in his many hobbies, notably gardening and playing the organ. He finished with a bang, being awarded (with J. Richmond) in 1988 the I.Mech.E. Thomas Bernard HaIl FVizc.He is survived by his wife, Muriel, whom he met during his time at Reading University and happily married in 1970. To his colleagues, on the other hand, Hirst was a very shy and private person with whom it was difficult to become intimate or to feel completely at ease. He did not enjoy conferences and did not perform well at the few he attended. This must have contributed to what some of us, who worked with him and read his papers with admiration, regard as a lack of recognition of his major contribution to the subject of tribology. K.L* Johnson Cambridge. August, 1997.
z W.
Hirst. Twenty
five years
af Tribology’
Tribology
hremariorraf,
28.23-27,
1995.