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The adhesion of vehicle tyres on icy surfaces
ABSTRACTS
119
106.
R. Weber (Univ. of Karlsruhe). The adhesion of vehicle tyres on icy surfaces. Auto. Industrie, 16 (2) 93-99 (April 1971). A tyre test-rig, in which the tyre runs on the internal surface of a drum, permitting measurements on braked and driven wheels, was adapted to allow measurements of tyre adhesion on simulated "black ice". The drum was closely surrounded by a metal housing, insulated by a 100-mm-thick layer of Styropor, to which aluminium foil was affixed. The air in the chamber thus formed could be cooled to 50 deg C below ambient temperature by a system comprising water-cooled compressor, evaporator and blower. A total-radiation pyrometer measured the surface-temperature of the ice which had formed on the drum surface just before wheel-contact. Since ice from tap water had a milky appearance, distilled water was used--this produced ice which was crystal-clear to the maximum permissible depth. Preliminary measurements showed that the friction coefficient rose with the number of drum rotations during a test, and more markedly the older was the ice, from realistic but not reproducible initial values to final values which correlated well in the various tests but greatly exceeded the known friction coefficients on natural ice. Since it was found that the coefficient did not increase significantly with duration of testing at temperatures above --5 deg C, test measurements were made at between 0 and 5 deg C. The rise in ice temperature produced by the tyre was measured, the increase normally not exceeding 0.5 deg C for the rolling tyre. For the actual tests, the dry drum and tyre were pre-cooled overnight. Distilled water was then applied with a sponge to the drum, revolving at 20 km/hr, until ice 2-mm-deep was formed, sufficient to cover emery-paper surface-irregularities. When the ice was 15 mm thick after three or four days of testing, the chamber was opened for the ice to melt. During testing, fresh ice was added via a small door in the chamber wall. (M.I.R.A.)
108.
R. N. Yong and E. McKyes. Yield and failure of clay under triaxial stresses. J. Soil Mech. Fndns. Div., Proc. ASCE, 97 (SM 1) Paper 7790, pp. 159-176 (January 1971). A study is made of the three-dimensional stress-deformation behavior of a normally consolidated saturated remoulded clay. It is demonstrated that unless certain requirements of analytical models (e.g. isotropy and volume change), are reconciled with the observed physical performance of the clay in yield, serious errors and misinterpretations would arise in the use of classical plasticity techniques for analysis. The true triaxial test results permit the measurement of associated deformations, and allow for the development of modifications to the classical theory. The adaptation of plasticity theory proposed in this study affords a suitable analytical model for the description of response behavior of the clay over a considerable range of applied stress levels. Beyond this range the changes in material properties accompanying shear deformation can no longer be compatible with the requirements of isotropic plasticity theory. In the ultimate stage of yielding, the clay performance tended to that of an internally frictional material. (Author's summary.)
These abstracts have been collected by A. D. Trapp of the Department of Agricultural Engineering, The University of Newcastle-upon-Tyne. The following is a list of publications searched : (1) British Technology Index, The Library Association, London. (2) Monthly Summaries, Motor Industry Research Association, Lindley. (3) Applied Mechanics Review, Am. Soc. Mech. Eng., New York. (4) U.S. Govt. Research Development Reports, Dept. of Commerce, Springfield. (5) J. Soil Mech. and Found. Div., Am. Soc. Civil Eng., New York. (6) Geotechnique, Inst. Civil Eng., London. (7) Civil Eng. and Public Works Review, London. (8) Soils and Fertilizers, Commonwealth Bureau of Soils, Harpenden. (9) J. Agric. Eng. Res., NIAE, Bedford. (10) Civil Engineering, Am. Soc. Civil Eng., New York. (11) Soil Science Proceedings, Am. Soc. of Soil Science, Washington. (12) J. Eng. Education, Am. Soc. Eng. Education, Washington. (13) Materials Research and Standards, Am. Soc. Testing Materials. (14) J. Strain Analysis, Inst. Mech. Eng., London. (15) Agricultural Engineering, Am. Soc. Agric. Eng., Michigan. (16) Soviet Soil Science (Translation of Poehovedeniye), Soil Sci. Soc. of Am., Wisconsin. (I 7) Canadian Geoteehnieal J., National Res. Council of Canada.
119
106.
R. Weber (Univ. of Karlsruhe). The adhesion of vehicle tyres on icy surfaces. Auto. Industrie, 16 (2) 93-99 (April 1971). A tyre test-rig, in which the tyre runs on the internal surface of a drum, permitting measurements on braked and driven wheels, was adapted to allow measurements of tyre adhesion on simulated "black ice". The drum was closely surrounded by a metal housing, insulated by a 100-mm-thick layer of Styropor, to which aluminium foil was affixed. The air in the chamber thus formed could be cooled to 50 deg C below ambient temperature by a system comprising water-cooled compressor, evaporator and blower. A total-radiation pyrometer measured the surface-temperature of the ice which had formed on the drum surface just before wheel-contact. Since ice from tap water had a milky appearance, distilled water was used--this produced ice which was crystal-clear to the maximum permissible depth. Preliminary measurements showed that the friction coefficient rose with the number of drum rotations during a test, and more markedly the older was the ice, from realistic but not reproducible initial values to final values which correlated well in the various tests but greatly exceeded the known friction coefficients on natural ice. Since it was found that the coefficient did not increase significantly with duration of testing at temperatures above --5 deg C, test measurements were made at between 0 and 5 deg C. The rise in ice temperature produced by the tyre was measured, the increase normally not exceeding 0.5 deg C for the rolling tyre. For the actual tests, the dry drum and tyre were pre-cooled overnight. Distilled water was then applied with a sponge to the drum, revolving at 20 km/hr, until ice 2-mm-deep was formed, sufficient to cover emery-paper surface-irregularities. When the ice was 15 mm thick after three or four days of testing, the chamber was opened for the ice to melt. During testing, fresh ice was added via a small door in the chamber wall. (M.I.R.A.)
108.
R. N. Yong and E. McKyes. Yield and failure of clay under triaxial stresses. J. Soil Mech. Fndns. Div., Proc. ASCE, 97 (SM 1) Paper 7790, pp. 159-176 (January 1971). A study is made of the three-dimensional stress-deformation behavior of a normally consolidated saturated remoulded clay. It is demonstrated that unless certain requirements of analytical models (e.g. isotropy and volume change), are reconciled with the observed physical performance of the clay in yield, serious errors and misinterpretations would arise in the use of classical plasticity techniques for analysis. The true triaxial test results permit the measurement of associated deformations, and allow for the development of modifications to the classical theory. The adaptation of plasticity theory proposed in this study affords a suitable analytical model for the description of response behavior of the clay over a considerable range of applied stress levels. Beyond this range the changes in material properties accompanying shear deformation can no longer be compatible with the requirements of isotropic plasticity theory. In the ultimate stage of yielding, the clay performance tended to that of an internally frictional material. (Author's summary.)
These abstracts have been collected by A. D. Trapp of the Department of Agricultural Engineering, The University of Newcastle-upon-Tyne. The following is a list of publications searched : (1) British Technology Index, The Library Association, London. (2) Monthly Summaries, Motor Industry Research Association, Lindley. (3) Applied Mechanics Review, Am. Soc. Mech. Eng., New York. (4) U.S. Govt. Research Development Reports, Dept. of Commerce, Springfield. (5) J. Soil Mech. and Found. Div., Am. Soc. Civil Eng., New York. (6) Geotechnique, Inst. Civil Eng., London. (7) Civil Eng. and Public Works Review, London. (8) Soils and Fertilizers, Commonwealth Bureau of Soils, Harpenden. (9) J. Agric. Eng. Res., NIAE, Bedford. (10) Civil Engineering, Am. Soc. Civil Eng., New York. (11) Soil Science Proceedings, Am. Soc. of Soil Science, Washington. (12) J. Eng. Education, Am. Soc. Eng. Education, Washington. (13) Materials Research and Standards, Am. Soc. Testing Materials. (14) J. Strain Analysis, Inst. Mech. Eng., London. (15) Agricultural Engineering, Am. Soc. Agric. Eng., Michigan. (16) Soviet Soil Science (Translation of Poehovedeniye), Soil Sci. Soc. of Am., Wisconsin. (I 7) Canadian Geoteehnieal J., National Res. Council of Canada.