All in an engineer’s life
2002; American Society of Mechanical Engineers; Volume: 55; Issue: 4 Linguagem: Inglês
10.1115/1.1481373
ISSN2379-0407
Autores Tópico(s)Fire effects on concrete materials
ResumoSir Bernard CrosslandBernard Crossland was born in Sydenham, South London in 1923. On leaving grammar school, aged 16, he was apprenticed to Rolls Royce Ltd, Derby. He was awarded an External University of London BSc (Eng) before he was 20. Subsequently, he served as a vibration engineer, and for his work on the axial vibration of crankshafts he was awarded an External University of London MSc (Eng). In 1946 he became involved in high-pressure research at pressures up to 7 kbar under Professor JLM Morrison at the University of Bristol. In 1953, he gained a PhD from the University of Bristol for research on the effect of high-pressure on the shear strength of metals and, subsequently, was awarded a DSc from the University of Nottingham in 1960. In 1959, he was appointed Professor and Head of the Department of Mechanical Engineering, Queen’s University, Belfast, where he instituted research into the peaceful use of high explosives in metal forming of stainless steel denture plates, and the welding of dissimilar metals. He served for a period as Dean and Senior Pro-Vice-Chancellor before retiring in 1984, and continued with high-pressure research but at pressures up to 20 kbar. After retiring he became extensively involved in the investigation of several major accidents, such as the King’s Cross Underground Fire. In 1986–87, he was President of the Institution of Mechanical Engineers and from 1995–98, President of the Welding Institute. He has served on and chaired several major Government Committees in Northern Ireland and Great Britain. Professor Crossland was elected Member of the Royal Irish Academy and in 1979 was elected Fellow of the Royal Academy of Engineering and Fellow of the Royal Society. He has been elected Honorary Member of ASME and Honorary Fellow of IMechE, WI, IstructE and IEI. He has been awarded the Kelvin Medal of the Institution of Civil Engineers, the Dickenson Medal of the Newcomen Society, the James Watt International Gold Medal of the IMechE, the Cunningham Medal of the Royal Irish Academy and, with others, the George Stephenson Research Prize and the Hawksley Gold Medal of the Institution of Mechanical Engineers. He has given named lectures including the Calvin Rice Lecture of ASME and has been awarded nine honorary doctoral degrees. Queen Elizabeth II made him a Commander of the British Empire in 1980 and a Knight Batchelor in 1990 for services to education and industry. by Norman Jones and Arthur LeissaBefore the Second World War, Great Britain had a very stratified society, and I came from a working class family with no tradition of university education. At the age of 16 at the beginning of the Second World War, I left grammar school in Canterbury to take up an Engineering Apprenticeship at Rolls Royce Ltd, Derby, which meant my leaving home. At that time, the factory was working a seven-day week with overtime on five nights and a half a day off per fortnight. I was released one day a week and was expected to attend four evenings at the Derby Regional Technical College to study for an External London University degree in Mechanical Engineering. It was a tough life, but the combination of theory and practice produced excellent practically oriented engineers. Many eminent engineers in the UK came up that route. In 1941 at the age of 17, I passed my External London University Intermediate BSc (Eng). Fortunately it coincided with recognition by the Government that there was a desperate shortage of graduate engineers particularly in the armed services. They introduced a State Bursary Scheme and I was awarded one, which allowed me to study full time in the Nottingham University College, a recognized college of the University of London. My professor was Charles Henry Bulleid, an inspirational teacher, who had at the beginning of the century been a Technical Assistant to Charles Parsons, who had invented, developed and exploited the reaction steam turbine. In 1943 while still under 20 years old, I was awarded an honors BSc (Eng) External London degree, while having gained 112 years of industrial experience. Having discovered rather belatedly that I was medically unfit, the Joint Recruiting Board directed me back to Rolls Royce to complete my training. There I was directed to work in the Experimental Vibration Department under Harold W Shaw. The Department was just at the stage of moving from optical/mechanical vibration instrumentation to electronic recording systems, which were mainly designed and built in-house as there were no established external providers. We even made our own strain gauges until they became commercially available. It was an excellent training in what was then leading edge instrumentation systems, which stood me in good stead when I moved into the university world. Our work, to begin with, was devoted to the severe vibration problems experienced with high performance internal combustion aircraft engines such as the world famous Merlin, and the Griffon and Eagle engines. The main, but not only, problem was the torsional vibration of the crankshaft propeller system. The experimentally determined impedance of the propeller was used to calculate the overall torsional vibration characteristics. Experimentally electromagnetic seismic torsiographs or eddy current torsiographs were used, and sometimes the propeller was strain gauged and silver carbon brushes on silver slip rings were used to connect them to the recording system. Later on attempts were made to mount resistance strain gauges in ceramic paint on gas turbine blades, and I developed a multi-channel mercury slip ring for that purpose. Sometime in 1943–44, I became involved with work associated with the first Rolls Royce designed jet engine, the Derwent, to determine the natural frequencies of turbine discs by using the Rayleigh-Ritz iterative analysis. But with the limitations imposed by the electro-mechanical calculators then available, it proved extremely time consuming. So, ultimately, I determined the frequencies experimentally using a cello bow to excite vibration of a disc, and fine silver sand to establish the nodal pattern, and an electromagnetic pick-up to produce a signal which could be analyzed to give the frequency. For turbine blades, we used a violin bow or sometimes carbon dioxide ice, which can be used to excite vibration. Later on, we built electromagnetic exciters with a variable frequency oscillator to excite vibrations in a more controlled way. In 1944, work was continuing on developing larger internal combustion engines, as gas turbines had not yet been sufficiently developed or accepted as the future propulsion unit for aircraft. It was feared with these larger engines that axial vibrations of crank shafts might pose a problem. Consequently, I was released one day a week to return to Nottingham University College to work under Professor CH Bulleid to investigate the axial vibration of crankshafts, which led to the award of an MSc (Eng) External London in 1946. In 1944, I was also loaned to Lloyds Register who was examining the vibration of reduction gears fitted to destroyers, which had been manufactured by BTH on a gear hobbing machine with a periodic fault in its master gear. I carried out tests on a reduction gear in the HMS Cavalier, a destroyer built by John Samuel White’s shipyard at Cowes on the Island of Wight. This involved unescorted and unarmed high speed trials in the English Channel, which was an interesting if scary experience. My memory was of the excellent breakfast in the officer’s mess; the best I had for the entire duration of the war. With the end of the war in 1945, I became convinced that there was little future in the aircraft engine industry, which mainly depended on military orders. It demonstrates how wrong one can be in forecasting the future. But I could hardly have foreseen that within a year or two the cold war would break out, and the arms race would reignite. Perhaps more surprisingly nobody at that time had any inkling of the enormous and never ending increase in air travel. Having crammed in a wonderful experience and education within five short years I decided to move on into higher education. After a year as a lecturer in the Luton Regional Technical College, now the University of Luton, I moved on to an Assistant Lecturer post—the lowest of the low—in the Department of Mechanical Engineering in the well recognized University of Bristol. I thought it gave a better opportunity for research. I was appointed by Professor Andrew Robertson FRS who was Dean of the Faculty of Engineering and Principal of the Merchant Venturers Technical College in which the Faculty had been housed since 1908. The origins of the Merchant Venturers Technical College could be traced back to a School of Navigation set up by the Society of Merchant Venturers in the 16th century. Robertson had carried out extensive work on the properties of materials, and for my generation his name was associated with the Perry-Robertson strut formula. He was also an excellent designer who, with his colleague John LM Morrison, had designed the very successful FNF knitting machine, extensively exploited after the war in producing lock-knit fabric. Morrison was appointed to the Chair of Mechanical Engineering and as Head of Department in the year I was appointed an Assistant Lecturer. He had followed in Robertson’s footsteps in carrying out experimental work on the yield of steels, the effect of strain rate on yield, and the plastic flow of materials following a complex strain path. During the war, he had carried out instrumented high-pressure cycling tests on autofrettaged gun barrels, to examine the stability of the residual stresses. After 2000 cycles, a fatigue failure, initiated at a radial hole in the cylinder wall was experienced; the first to be reported in the UK. Morrison was an extremely careful and meticulous experimenter, and I doubt that his experimental data have ever been bettered. As a very young Assistant Lecturer (I was only 23), I was heavily loaded with lectures and laboratory supervision. After a few years, I was also responsible for supervising many final year research projects, which formed an important component of the assessment of students. It was soon clear to me that our workshop, equipped with essentially Boer War machine tools, was completely inadequate to support final year project work and, much more, postgraduate research. Having expressed my concern, I found myself made responsible for modernizing the workshop and taking on additional mechanics. It is my strongly held view that research in mechanical engineering demands adequate workshop support. I soon recognized that there was nobody in Bristol who was able to supervise my research interest in the vibration of turbine discs and blades. I concluded that, when in Bristol, there was no alternative to carrying out research into materials. Fortunately at that juncture, Morrison was approached by WRD Manning, Dermot, to carry out research on the fatigue of thick-walled cylinders subjected to cyclic high pressure. Dermot was the Assistant Chief Engineer of the Plastics Division of Imperial Chemical Industries, ICI. In the late 1920s, he became involved in the design of high pressure laboratory equipment, which led to the accidental discovery of polyethylene in 1933. Polyethylene was found to have excellent dielectric properties, which made it ideal for the insulation of high frequency cables needed for radar then in the early stages of development. Dermot was responsible for the design of the first continuous flow plant for the production of polyethylene, which came on line in 1938, in time for the unprecedented demand in the war. Dermot paid considerable attention to the design of the high pressure autoclave and compressor cylinder, and in particular the possibility of fatigue under repeated pressure. Despite this, fatigue failures were experienced, particularly in the cylinder of the mercury lute high-pressure gas compressor. This led to the approach to Morrison to investigate the fatigue of gun steel cylinders subjected to repeated internal pressures of up to 3 kbar (≅20tonf/in2 or 45000lbf/in2). John SC Parry was probably the first postgraduate research student to be appointed in mechanical engineering in Bristol, and I also became heavily involved. Morrison supervised the pair of us. Ultimately, after two years and many vicissitudes, we developed a repeated pressure machine which could apply a repeated pressure of 3 kbar at 1000 cycles/min. Even then tests to ten million cycles, required to establish the fatigue limit, took seven days. An extensive series of tests on cylinders with a K (OD/ID) ranging from 1.2 to 3 were carried out. Surprisingly, it was found that the fatigue limit of all the cylinders was dependent on a critical value of the shear stress at the bore PK2/K2−1. In 1956, the three of us were awarded the George Stephenson Research Prize of the Institution of Mechanical Engineers, for the development of the machine and preliminary results. This was the beginning of an extensive research program involving our ever increasing expertise in high pressure research. Morrison did not believe in two–handed research projects leading to the award of PhDs to both individuals. So I decided to investigate the effect of high pressure on the shear strength of metals, which involved the design of a torsion machine operating at high ambient pressure. This was following very much in the footsteps of the great Nobel Laureate, PW Bridgman, who had carried out extensive tension tests on materials under very high ambient pressure. The advantage of torsion tests was that it was easier to measure the stress strain relationship up to failure, as there was no necking as in tension. As with Bridgman, I found large increases in strain to failure with pressure. With white cast iron I observed the effect of coating the specimen with a thin film of rubber by dipping the specimen in rubber solution. Without protection the specimens failed with negligible plasticity, but with protection large strains to failure were observed with increasing pressure. This mirrored Bridgeman’s experience with tension tests on glass under pressure. I had designed a 7-kbar automatic intensifier with a rotating piston dead weight pressure tester to control and measure the pressure. This was extensively used for project work including bursting tests on steel cylinders, which was started by JA Bones, a final year project student. Bursting pressure was of considerable interest to ICI as it was one of their design criteria. Diametrical and axial optical extensometers were designed, which were very sensitive; at that time there was no proven electronic alternative. The correlations between the experimentally determined pressure expansion curve for cylinders with a K of up to 8 and the calculated curves based on torsion data was excellent. This work and further experimental work sponsored by Foster Wheeler was published. For the 1956 International Conference on the fatigue of metals, the group under Morrison published four papers, and our laboratories were thrown open to the delegates. John Parry reported on the continuing program of repeated pressure tests on cylinders including autofrettaged cylinders. I reported on the design of a high pressure torsional fatigue machine and preliminary results on an alloy steel. My first tests showed, unexpectedly, a declining fatigue limit as the ambient pressure was raised. But specimens protected by a thin rubber film showed an increase in the fatigue limit with ambient pressure, ultimately being limited by the plastic yield stress. This led to a fuller understanding of the unexpected low fatigue limit of thick-walled cylinders subjected to repeated pressure. Tests on cylinders with a thin rubber film protecting their bores gave significantly higher results. This suggested that without protection the fluid pressure was able to exert pressure on the flanks of small surface defects or embryo fatigue cracks. This effectively increased the hoop tension stress at the base to 2PK2/K2−1 or twice the shear stress. It suggested that the critical stress at the fatigue limit was in fact the tensile hoop stress at the bore, not the shear stress. With another postgraduate research student, DJ White, we built a slipping clutch resonance push-pull fatigue machine operating at high ambient pressure. This was a very substantial design which worked wonderfully well. It was used to investigate the effect of high pressure on the push-pull fatigue of an alloy steel. This again substantiated the effect of protecting the surface of the specimens, and the limitation of the increase of the fatigue limit to the plastic yield stress. Another final year student, DS Dugdale, built a high pressure falling ball viscometer, with detectors, to time the ball in flight. He carried out tests on castor oil to pressures up to 3 kbar and temperatures up to 100°C. Many years later, I found that this work had been repeated in the University of Osaka with excellent correspondence. Though it puzzled me how they had got hold of our data, which had never been published. Looking back, it amazes me the magnitude of the projects carried out by final year undergraduates, as part of the requirement for the award of a first degree. These projects give a flavor of the kind of work we carried out under John Morrison. There was also a lot of ancillary testing and metallurgy carried out to fully describe the properties of the materials we tested. Specimens used were highly polished and Morrison designed and marketed automatic polishing machines for tension and torsion specimens and we also devised automatic honing machines to finish the bores of the thick-walled cylinders. All specimens were finally stress relieved in a high vacuum furnace. Meticulous care was taken in the preparation of specimens and qualifying the materials we tested. In the nine years from the start of the high pressure program in 1950, we had carried out an immense program of experimental research. This had involved the development of many original testing machines and the associated high-pressure technology. Looking back my regret is that we laid too much emphasis on designing testing machines and too little on exploiting them to advance our knowledge of the behavior of materials under three-dimensional fatigue loading. Morrison clearly felt that the design of an original machine was an essential part of training in research as well as the planning, execution, and analysis of an experimental program. The subsequent success of the handful of research students involved perhaps substantiated Morrison’s belief. Essentially, what we lacked at that time was financial support for research fellows who might have pursued the interpretation and understanding of the immense amount of data we had accumulated. In the late 1950s, I felt it was time to move on because though I had been promoted to a senior lectureship, there was no chance of a second chair being created. At the time, most of the engineering departments in UK universities were headed up by a single professor, and normally vacant chairs were filled from outside the University; fresh blood was considered important. So I started to apply for chairs which became vacant, and the Queen’s University of Belfast was the first post I was offered. I was 35 years old. As with so many engineering departments in the UK universities at that time, my department, along with electrical engineering, was based in the local technical college—the Belfast College of Technology. This was housed in an impressive Edwardian building in the center of the city, which had been officially opened in 1911. Much of the laboratory equipment dated from that time or earlier, and some of it merited being housed in a museum. It had, however, been agreed that the University courses together with non-degree courses in higher technology were to be housed in a new building in the University area. This building was to be administered by a new joint body between the City and the University. My post as Professor of Mechanical Engineering and Head of Department involved planning of the new building and its equipment, which was officially opened by Lord Ashby in 1965 and named the Ashby Institute. In the meanwhile, I was faced with introducing a modern curriculum and initiating research, where previously there had been very little. Our research, together with a modern workshop, was temporarily housed in a gaunt Victorian house, around which temporary buildings sprung up as research grew. Fortunately, ICI continued to support my research and I attracted significant research fundings from the Ministry of Defence to investigate the short term fatigue and fracture of gun barrels. With higher velocities, firing pressures were increasing and higher strength steels were being used, which posed serious problems of fatigue life and more importantly fast fracture. We also obtained Government research funding to study the creep of thick-walled cylinders under high internal pressure and at elevated temperature. The creep program was carried out by WJ Skelton, a postgraduate research student. This program appealed to me as excellently well balanced and Skelton was intellectually very gifted. He was also hard working and an excellent engineer who had come up the hard industrial route. He designed a high-pressure cylinder creep rig with a novel pressure compensator to accommodate the small changes of pressure resulting from the slow increase in internal volume. A kinematically designed diametrical extensometer with a displacement transducer and recording system was devised. A three-zone furnace with a temperature controller ensured a uniform temperature environment. To obtain ancilliary tension creep data, a high sensitivity tension creep machine with an axial extensometer fitted with a displacement transducer was designed. For the first time in my researches, the analysis of experimental data and the prediction of creep in a cylinder from tension data was carried out on the University’s newly installed Deuce computer; excellent training at that time. This was a substantial program involving creep tests with a duration of one year, which were completed in a little over three years. The correlation achieved between theory and experiment was excellent. For this work, published in the 1st High Pressure Technology Conference and in the Proceedings of the Institution of Mechanical Engineers, we were awarded the Thomas Hawksley Gold Medal. Skelton stayed on as a Whitworth Research Fellow and continued with the creep program. With RG Patton, he designed a high sensitivity torsion creep machine which provided more relevant data on which to base the calculation of the creep of thick-walled cylinders. Another research student, BA Austin, started-up the research program on the short–termed fatigue and fracture of gun barrels, including some fired specimens with thermal cracking. This was a beginning of a program involving the development of an understanding of fracture mechanics of single radial cracks in thick-walled cylinders, and multiply cracked cylinders as experienced in rifled guns. This involved the construction of repeated pressure fatigue machines for cylinders including sections of virgin and fired 105 mm tank guns and the development of compact tension tests to establish the fracture toughness of gun steels. It was a subject very much in its infancy, and at that time I was fortunate to spend a spell in Lehigh University where I met Paul Paris, George Sih, and the doyen of fracture mechanics, George R Irwin. The culmination of this program was the research carried out by RWE Shannon, another exceptional student who had come up the hard industrial route. His research was another well-balanced program. At a time when finite element programming was not fully established, he developed a computer program to establish the stress intensity factor for a radial crack in a thick-walled cylinder and for a multiply cracked cylinder. Interestingly, the stress intensity factor for a multiply cracked cylinder is less than for a single crack; the lesson is that if you are going to have a cracked cylinder it is preferable to have as many cracks as possible! He built a rig to grow a radial crack in a thick-walled cylinder, and he developed instrumentation to accurately monitor the depth of the crack, which was also applicable to compact tension specimens. Finally, he carried out static bursting tests on pre-cracked thick walled cylinders to determine the stress intensity factor. He found excellent correlation between theory and experiment. Shannon demonstrated the value of such research training. When he left us, he joined the On-line Testing Station of British Gas where he ultimately led a team of engineers in the development of the highly successful intelligent pig for the on-line inspection of gas and oil pipelines. This detects and quantifies defects in steel pipes and the surrounding concrete protective shield and records their position. The intelligent pig travels maybe tens of kilometres before being withdrawn and interrogated to determine defects which need to be rectified. The intelligent pig has been extensively used worldwide. During this period, ICI became concerned to assess the safety of their 250 liter autoclaves used in the production of polyethylene worldwide. After a meeting to discuss their concern, I proposed that one of their autoclaves should be sacrificed and tested under repeated high pressure to failure. We were asked to carry out the test simulating service pressures with one cycle in a hundred simulating the over pressure when the safety valve operated. It was a substantial task as we only had temporary laboratory accommodation. The vessel was 12 ins bore, and after each 1000 cycles, we were required to carry out a detailed NDT inspection to detect cracks. This was a demanding task requiring the construction of a high-pressure programable pulsator. The test was concluded successfully and established that the remaining life of the vessel under the then operating conditions was 180 years, and the crack grew steadily without the onset of fast fracture. For our high pressure research, we designed and developed a 14 kbar (200,000 psi) automatic intensifier with associated valves, pipe fittings and pressure transducers. This was successfully marketed worldwide. This unit was used in the work we carried out to determine the effect of pressures up to 14 kbar and temperatures of up to 200°C on the viscosity of lubricating oils. The program was sponsored by the Mobil Oil Company and aimed at achieving a more comprehensive understanding of the hydrodynamic lubrication of heavily loaded contact surfaces, such as in gearing and ball bearings. For this program, WRD Wilson developed a very compact falling plate viscometer, which required a 50 cc sample of the test fluid. The rate of approach of the falling plate was measured by the change of capacitance, while a standard gap allowed the dielectric constant to be measured. The compressibility of the sample was measured by the displacement of a flexible bellows. The unit was housed in a high-pressure vessel in a temperature controlled environment. Analysis showed that the edge effect of the falling plate was negligible. Its use was successfully demonstrated. Another postgraduate student, WP Boyle, developed a high rate of shear viscometer for use at high pressure. A capillary in a piston was the essential element. The piston could be forced down a closed cylinder, with a high background pressure, while the pressure difference could be measured by a sensitive differential pressure transducer. This rig was successfully demonstrated, though further work was required to investigate the flow regime at the outlet of the capillary, and the mean temperature of the oil flowing through it. These were two very specialized and novel pieces of equipment, and having demonstrated their viability funding came to an end, which was a bitter disappointment. As a consequence, they were never used to explore the properties of lubricating oils under high pressure, high shear rates and elevated temperature. On the positive side, Wilson subsequently made great use of the knowledge he gained in quantifying the role of lubrication in metal forming processes. In the diamond synthesis process the rams and cylinders are made of tungsten carbide, which operate at a pressure of many tens of kilobars and at high temperatures. Though tungsten carbide is normally considered to be brittle, the components of synthesis equipment showed plastic distortion. Clearly, to understand the design of the rams and cylinders compressive properties of tungsten carbide were needed at the operating pressure and temperature. De Beers Industrial Diamond Co commissioned us to carry out such a research. PA Brew designed a high pressure compression testing machine and at 14 kbar some grades of tungsten carbide showed plastic flow before failure. He also carried out some atmospheric pressure hot compression tests. The 14 kbar intensifier was developed as a gas compressor for argon and helium and its pressure capability was raised to 20 kbar. We developed a furnace for internal use in a high pressure vessel, and commenced construction of a high pressure high temperature compression machine, but at that stage, Brew left us unexpectedly and the research funding came to an end. The task was really too big for our support services, and though we were on the road to a successful conclusion, the research came to an end as at that time I was appointed as Senior Pro-Vice-Chancellor of the University. Back in 1960, I became involved in the use of high explosives in forming and welding. My dentist, when he had both hands in my mouth, criticized the inabi
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