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The standard view of mechanical adhesive contact is as a competition between a reduction in free energy when surfaces with bonding potential come into contact and an increase in free energy due to elastic deformation that is required to make these surfaces conform. An equilibrium state is defined by an incremental balance between these effects, akin to the Griffith crack growth criterion. In the case of adhesion of biological cells, the molecules that tend to form surface-to-surface bonds are confined to the cell wall but they are mobile within the wall, adding a new phenomenon of direct relevance to adhesive contact. In this article, the process of adhesive contact of an initially curved elastic plate to a flat surface is studied for the case in which the binders that account for adhesion are able to migrate within the plate. This is done by including entropic free energy of the binder distribution in the total free energy of the system. By adopting a constitutive assumption that binders migrate at a speed proportional to the local gradient in chemical potential, the transient growth of an adhesion zone due to binder transport is analyzed. For the case of a plate of very large extent, the problem can be solved in closed form, whereas numerical methods are invoked for the case of a plate of limited extent. Results are presented on the rate of growth of an adhesion zone in terms of system parameters, on the evolution of the distribution of binders and, in the case of a plate of limited extent, on the long-term limiting size of the adhesion zone. 相似文献
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化学镀非晶态Ni—P层的初期沉积过程研究 总被引:2,自引:0,他引:2
化学镀非晶态Ni-P镀层初期沉积过程和沉积层状态是影响结合强度的决定性因素.对不同基体材料初期沉积的观察发现,有些非晶态镀层的初期沉积中含有微晶.微晶的产生与否与基体材料以及镀层材料晶格的错配度有关,当镀层与基体材料点阵常数相差不大,镀层的初期沉积沿基体晶格外延生长出现微晶层,反之,点阵常数相差较大时,初期沉积物中未发现微晶. 相似文献
4.
生物特异性功能高分子 总被引:1,自引:0,他引:1
模仿天然生物活性高分子关键作用点的化学组成,在高分子链上接上各种官能团或化学残基,制备具有与该天然高分子相似生物活性的高分子,即生物特异性功能高分子。本文主要介绍拟肝素高分子和似粘连 蛋白高分子两种生物特异性功能高分子。 相似文献
5.
Precipitation temperature-total polymer concentration diagrams for toluene solutions of two styrene-acrylonitrile copolymers different in chemical composition and their mixtures were determined and then triangular phase diagrams of this system were constructed from these diagrams. It is speculated from the triangular phase diagrams and experimentally shown that the copolymer may be effectively fractionated by chemical composition in this system. 相似文献
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To intensify experimental research within the field of orthopaedic tribology, a three-station, dual motion, high frequency (25.3 Hz) circular translation pin-on-disc wear test device was recently introduced. In the present study, the pins were CoCr with a spherical, polished bearing surface of 28 mm radius, whereas the flat discs were conventional UHMWPE. This configuration was intended to simulate the wear mechanisms of total knee prostheses. The number of wear cycles run was as high as 200 million. The mean wear rate was 0.35 mg per one million cycles (0.77 mg/24 h) which corresponded to a mean wear factor of 3.5 × 10−6 mm3/Nm. The study provided further proof that a wear test for orthopaedic implant materials can be accelerated by substantially increasing the cycle frequency, provided that the sliding velocity remains close to the values obtained from biomechanical studies. Hence, the moderate frictional heating will not lead to unrealistic wear mechanisms. 相似文献
7.
Heqing Fu Hong Huang Qi Wang Hui Zhang Huanqin Chen 《Journal of Dispersion Science and Technology》2013,34(5):634-638
The aqueous polyurethane hybrid dispersion modified by the epoxy resin were synthesized using 1,4-butanediol ( BDO ) and dimethylolpropionic(DMPA) as chain extenders. A kind of automobile interior decoration adhesive was made by the modified hybrid dispersions. Effects of the content and the kinds of epoxide resin on the properties of dispersions and dispersion-cast films such as appearance, pot life, viscosity, particle size, molecular mass, hardness, swelling in water, contact angle, strength of stress, elongation at break, and other mechanical properties were studied. At the same time the effect of the E20 content on the peel strength of the adhesive for several automobile interior decoration substrates such as rubber/wood, poly(vinyl chloride)/wood; leather/wood, sponge/wood was investigated. The experimental results show that when the epoxy resin E20 content was 8%, the modified polyurethane hybrid dispersions possess better properties and the adhesive made by the modified dispersions posses better adhesion for automobile interior decoration substrates. The stress-strain curve of the modified aqueous polyurethane hybrid dispersions films shows the modified aqueous cast films possess better rigidity and toughness. 相似文献
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平面应力条件下闭合断续节理岩体力学特性试验研究 总被引:4,自引:0,他引:4
通过平面应力条件下闭合断续节理岩体的破坏试验,采用自行研制的高压柔性加载装置施加垂向和侧向荷载,用千分表和激光散斑照相技术量测试体位移场,用应变花量测试体平面应力场. 结果表明,激光散斑法用于测定闭合断续节理岩体的位移场效果良好,其测值比对应点千分表测值偏小14% 左右.据所测得的位移场和应力场,研究了裂纹尖端应力场的演变及裂纹扩展的路径,分析了试体的变形和破坏特征,测定了翼裂纹初裂角,探讨了试体的破坏机理. 相似文献
10.
A. M. Visco V. Brancato L. Torrisi M. Cutroneo 《International Journal of Polymer Analysis and Characterization》2014,19(6):489-499
Single-lap polymeric joints can be obtained using laser welding overlapping two polymeric sheets, with one laser transparent and the other laser adsorbent. In this study we employed crystalline carbon nanomaterials (in amounts of 0.2, 0.5, and 1.0 wt.%) as filler to enhance the absorption of polyethylene (UHMWPE type). A Nd:YAG laser operating at 1064 nm was used as a power source to make the welded joints. Morphological, mechanical, and calorimetrical tests were carried out to study the strength of the joints made. Serious attention was paid to find the best compromise between exposure time to laser light and filler amount. We found that in the optimal conditions (with 0.2 wt.% filler and 60 s exposure time) the joint exhibits a good shear strength with a regular welded area. In fact, the best conditions guarantee proper absorption power of the laser light and deep interpenetration of the chains between the two polymeric sheets without any damage. 相似文献