In order to analyze causes of failures of heavy-loaded spur gears, the authors deal with their dynamic characteristics by considering a vibrating system composed of an effective mass of gear blanks and stiffness of meshing teeth with manufacturing errors under a given operating condition. Even in the case of gears with considerable errors the coincidence of the theoretical findings with experimental results is satisfactory. Under heavy-load conditions the plastic flow produced in the subsurface layers of gear teeth is found to affect the variation of the dynamic load considerably owing to a local change of the tooth profile. The interaction between the tooth deformation and the dynamic load is investigated experimentally and theoretically. The authors treat the conditions of initiation of the gear failures in the representative modes, e.g., pitting and scoring, in connection with the dynamic load.
Five rolling contact fatigue tests, Tests {1}–{5} have been conducted. In Tests {1}–{3}, when a fatigue crack was initiated on the surface of a follower, the test was halted. Then, in Test {1} the rotating direction was reversed. In Test {2} the follower and driver were interchanged, and in Test {3} the test was continued unchanged. In Test {3} the original crack grew to a pit. In Tests {1} and {2} the original crack immediately stopped propagating. In Tests {4} and {5}, mating with a harder roller, a softer roller was used as the follower in Test {4} and as the driver in Test {5}. A typical pit occurred in Test {4}. In Test {5}, surface damage substantially different from a typical pit was generated. Based on these experimental results, a 3-D crack analysis including the effect of frictional force on the contact surface and oil hydraulic pressure on crack surfaces, was conducted to elucidate the mechanisms of pit formation and surface damage in contact fatigue.
We report herein an efficient one‐step synthesis of 4,6‐benzylidene glycoside derivatives from aromatic aldehydes bearing electron‐donating or ‐withdrawing groups as well as polymerisable monomer groups. Glucose, mannose and galactose derivatives could also be used successfully. Several of the glucose derivatives thus obtained acted as gelators for various solvents, including water. 4‐(n‐Butoxybenzylidene)glucose derivative 3a produced both a clear squalane gel and a hydrogel at 0.1 wt.‐%. Furthermore, 3‐(n‐butoxybenzylidene)glucose derivative 3i produced a clear organogel and an opaque hydrogel. The critical gelation concentration (CGC) of 3i in squalane was determined to be 0.02 wt.‐%, which is one of the lowest CGC values reported so far. The organogels, hydrogels and aqueous solution gels produced from 3a and 3d exhibited thixotropy. The strength and thixotropy of the organo‐ and hydrogel produced from 3a were estimated by a rheometer. The gel morphologies were observed by field‐emission and wet‐scanning electron microscopy, and the self‐assembly modes were analysed by XRD. We have concluded that super‐gelators can be created by this method.
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