Parametric investigation of the combined effect of Gear parameters on Tangential Force and Dynamic Tooth Load of 40 Ni2 Cr1 Mo 28 Steel Helical Gear
Global competitive business market had brought increasing awareness to optimize the gear design. Gears have the advantage over friction and belt drives in that they are positive drive, a feature which most of the machine tools require, since exact speed ratios are essential. The design and manufacture of precision cut gears, made from materials of high strength, have made it possible to produce gears which are capable of transmitting extremely large loads at extremely high circumferential speeds with very little noise, vibration and other undesirable aspects of gear drives. The present work is to focus on investigating the combined effect of gear parameters on tangential force and dynamic tooth load of helical gear.
Vibration and acoustic investigation for a deep hybrid transmission with power-split compound planetary gear set
A new compound planetary gear set was produced for hybrid transmission with advantages superior to classical Ravigneaux planetary gears. However, vibration and noise problems need more attention in order to meet the market demand. Vibration characteristics of the new power-split hybrid transmission with a four-shaft compound planetary gear set are investigated. An equivalent method for stepped shaft is proposed to simplify the motor E1 shaft. Based on six degrees of freedom of helical gear pair model and shaft-bearing model, a dynamic model for the planetary mechanism is established in pure electric driving mode. The numerical analysis of the distinctive natural frequencies and corresponding vibration modes is produced. Moreover, in order to identify the noise source, noise and vibration experiments are carried out on test rig. By comparing the numerical results and test data, the noise and vibration at a frequency of 696 Hz are evidently caused by the transverse vibration of motor E1 shaft, and the rotational vibration of ring gear exacerbates the vibration and noise. Not only the impact of torques from motors E1, E2 and semi-shaft but also the influences of carrier speed and preload on differential bearings are investigated.
Thermal stability of reconstituted collagen fibrils. Shrinkage characteristics upon in vitro maturation
Thermal stability measured as area shrinkage without tension during heating was determined for membranes of collagen fibrils reconstituted from solutions of highly purified rat skin collagens. Shrinkage in per cent of area at 25 degrees C and shrinkage temperature were quantitated in a standardized way and determined as a function of in vitro maturation time for 11 to 104 days after aggregation for the collagen membranes. Similar to reports on intact rat skin, shrinkage temperature remained constant and shrinkage per cent declined with a rate decreasing with time during maturation. Solubility in water at 80 degrees C for 2 hours was 95-96% and remained unchanged for the maturation time (about 2 months) studied. The decreased shrinkage reflecting a lower degree of collapse is ascribed to an increasing thermal stability of the membranes during maturation. Development of heat-stable bonds in the reconstituted collagen fibrils is taken up to be amenable to this increased stability. Similarity in changes of shrinkage characteristics during in vivo and in vitro maturation indicates that maturation changes in reconstituted collagen fibrils reflect those occurring in intact collagen during in vivo aging.