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  • ASME International  (3)
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  • ASME International  (3)
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  • 1
    Online Resource
    Online Resource
    ASME International ; 2019
    In:  Journal of Applied Mechanics Vol. 86, No. 2 ( 2019-02-01)
    In: Journal of Applied Mechanics, ASME International, Vol. 86, No. 2 ( 2019-02-01)
    Abstract: The improvement of the accuracy and efficiency of microforming process of polymers is of great significance to meet the miniaturization of polymeric components. When the nonuniform deformation is reduced to the microscopic scale, however, the mechanics of polymers shows a strong reinforcement behavior. Traditional theoretical models of polymers which have not considered material feature lengths are difficult to describe the size effect in micron scale, and the process simulation models based on the traditional theory could not provide effective and precise guidance for polymer microfabrication techniques. The work reported here proposed strategies to simulate size effect behaviors of glassy polymers in microforming process. First, the strain gradient elastoviscoplastic model was derived to describe the size affected behaviors of glassy polymers. Based on the proposed constitutive model, an eight-node finite element with the consideration of nodes' rotation was developed. Then, the proposed finite element method was verified by comparisons between experiments and simulations for both uniaxial compression and microbending. Finally, based on the FE model, under the consideration of the effect of rotation gradient, the strain distribution, the deformation energy, and the processing load were discussed. These strategies are immediately applicable to other wide-ranging classes of microforming process of glassy polymers, thereby foreshadowing their use in process optimizations of microfabrication of polymer components.
    Type of Medium: Online Resource
    ISSN: 0021-8936 , 1528-9036
    Language: English
    Publisher: ASME International
    Publication Date: 2019
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  • 2
    In: Journal of Tribology, ASME International, Vol. 138, No. 3 ( 2016-07-01)
    Abstract: A combination technology of the solid lubricant and the laser surface texturing (LST) can significantly improve the tribological properties of friction pairs. The plate sample was textured by fiber laser and composite lubricant of polyimide (PI) and molybdenum disulfide (MoS2) powders were filled in the microdimples. Sliding friction performances of micron-sized composite lubricant and nano-sized composite lubricant were investigated by ring-plate tribometer at temperatures ranging from room temperature (RT) to 400 °C. On the one hand, the results of the micron-sized composite lubricant show that the friction coefficient of the textured surface filled with composite lubricant (TS) exhibits the lowest level and the highest stability compared to a textured surface without solid lubrication, smooth surface without lubrication, smooth surface burnished with a layer of composite solid lubricant. The better dimple density range is 35–46%. The friction coefficients of the sample surface filled with micron-composite solid lubricant with the texture density of 35% are maintained at a low level (about 0.1) at temperatures ranging from RT to 300 °C. On the other hand, the results of the nano-sized composite lubricant show that these friction properties are better than those of MoS2-PI micron-sized composite. The friction coefficients of MoS2-PI-CNTs nano-sized composite solid lubricant are lower than those of the MoS2-PI composite lubricant at temperatures ranging from RT to 400 °C. In addition, the possible mechanisms involving the synergetic effect of the surface texture and the solid lubricant are discussed in the present work.
    Type of Medium: Online Resource
    ISSN: 0742-4787 , 1528-8897
    Language: English
    Publisher: ASME International
    Publication Date: 2016
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  • 3
    In: Journal of Tribology, ASME International, Vol. 139, No. 2 ( 2017-03-01)
    Abstract: Experimental studies of friction and wear on textured surfaces filled with composite solid lubricant and lubricated with grease were conducted on a sliding plain bearing to enhance the working performance and lifetime under different conditions. Circular microdimples of different diameters were fabricated on GCr15 bearing steel specimens using the semiconductor sound and light pumped Nd:YAG laser machining equipment. Ring-on-ring tribological test configuration with GCr15 tribopairs under a combined non-Newtonian lubrication of grease and composite lubricant was performed. The results showed that the surface textures on specimen GCr15 bearing steel material filled composite solid lubricant and lubricated with grease (TLG), reduced the friction by 27%, 46%, and 75% of the grease only (TG), solid lubricant only (TL), and nonlubricated (T) specimens, respectively. The textured specimen with dimple diameter of 109 μm lowered the maximum coefficient of friction by 38% and enhanced the antiwear properties of GCr15 bearing steel material remarkably. This indicated that grease has great potential in promoting service life and working performance of sliding plain bearing when combined with composite solid lubricant in a laser-textured surface. It is therefore beneficial for applications in the machinery and automotive components industries in saving energy and reducing CO2 emission.
    Type of Medium: Online Resource
    ISSN: 0742-4787 , 1528-8897
    Language: English
    Publisher: ASME International
    Publication Date: 2017
    Location Call Number Limitation Availability
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