tailieunhanh - Clutches and brakes design and selection P1

1 Friction Materials Curves of the coefficient of friction as a function of load and of the speed differential between the lining and facings and their mating surface are no longer available from many manufacturers. Perhaps this is a consequence of the ease with which trial lawyers in the United States can collect large financial rewards for weak liability claims based upon often trivial, or unavoidable (due to physical limits on manufacturing tolerances), differences between published data and a particular specimen of the manufactured product. Furthermore, differences between published and operational coefficients of friction are beyond the control of the manufacturer because. | 1 Friction Materials Curves of the coefficient of friction as a function of load and of the speed differential between the lining and facings and their mating surface are no longer available from many manufacturers. Perhaps this is a consequence of the ease with which trial lawyers in the United States can collect large financial rewards for weak liability claims based upon often trivial or unavoidable due to physical limits on manufacturing tolerances differences between published data and a particular specimen of the manufactured product. Furthermore differences between published and operational coefficients of friction are beyond the control of the manufacturer because comparison of laboratory and operational data have shown that temperature humidity contamination and utilization cycles of the machinery using these linings and facings can cause significant changes in the effective coefficient of friction at any given moment. Consequently the coefficients of friction mentioned are nominal the following discussion is in generic terms and all curves shown should be understood to represent only the general character of the material under laboratory conditions. The value of laboratory data is twofold even though the data should not be used for design purposes. First the data provides a comparison of the performance of different lining materials under similar conditions such as given by the SAE 661 standard. Second comparison of the laboratory data with field data for a particular type of machine for several different linings may suggest an empirical relationship that yields an approximate means of predicting the field performance of other lining materials based upon their laboratory data. A history of the comparison of field and laboratory data Copyright 2004 Marcel Dekker Inc. may therefore serve as a starting point in the design of the prototype of a new machine of the same or similar type. Field testing of a new machine by customers under the most adverse .