爆炸荷载下矩形板的塑性动力响应

本文采用Jones-Sawczuk控制方程,导出了脉冲荷载下矩形板最大残余挠度的简单理论计算公式,并应用该公式和动态屈服条件,计算了固支方板在爆炸荷载下的最大残余挠度值,与试验结果比较,取得了令人满意的结果。     

稀土处理玻璃纤维填充聚四氟乙烯复合材料在油润滑下的摩擦学性能

分别用偶联剂、稀土以及偶联剂 -稀土混合物处理玻璃纤维表面 ,以改善玻璃纤维与聚四氟乙烯之间的界面结合力 ,考察了玻璃纤维填充聚四氟乙烯复合材料在油润滑下的摩擦学性能 .结果表明 :在油润滑条件下 ,表面处理玻璃纤维填充聚四氟乙烯复合材料的摩擦系数比未经处理玻璃纤维填充聚四氟乙烯复合材料的低 ,耐磨性亦较优 ;而稀土处理玻璃纤维填充聚四氟乙烯复合材料具有最低的摩擦系数及最高的耐磨性和极限 pv值 ;未经处理玻璃纤维填充聚四氟乙烯复合材料的磨损形式主要为粘着转移 ,偶联剂处理玻璃纤维填充聚四氟乙烯复合材料和偶联剂与稀土处理玻璃纤维填充聚四氟乙烯复合材料均以磨粒磨损为主 ,而稀土处理玻璃纤维填充聚四氟乙烯复合材料的磨损机理主要为粘着磨损和轻微磨粒磨损     

Validation of Thermal Equilibrium Assumption in Transient Forced Convection Flow in Porous Channel

The validity of the local thermal equilibrium assumption in the transient forced convection channel flow is investigated analytically. Closed form expressions are presented for the temperatures of the fluid and solid domains and for the criterion which insures the validity of the local thermal equilibrium assumption. It is found that four dimensionless parameters control the local thermal equilibrium assumption. These parameters are the porosity , the volumetric Biot number Bi, the dimensionless channel length _max and the solid to fluid total thermal capacity ratio C _R. The qualitative and quantitative aspects of the effects of these four parameters on the channel thermal equilibrium relaxation time are investigated.     

Linear viscoelastic behavior of narrow molecular weight distribution 1,4 polybutadiene: Comparison with Doi-Edwards theory of reptation

Linear viscoelastic behavior of narrow molecular weight distribution 1,4 polybutadiene samples with molecular weights between 42500 and 779000 has been correlated with molecular structure using a simple modification of the Doi-Edwards theory of reptation. The entire GPC curve is required for the calculations of viscoelastic behavior.The plateau modulus obtained from the experimental data is comparable to literature values, while the equilibrium compliance (which is indicative of polydispersity) is greater than values reported in the literature for nearly monodisperse polybutadienes. Reasonable agreement between theory and experiment is obtained over the entire molecular weight range. The agreement between theory and experiment using the GPC curve is better than that obtained by assuming the polymer to be monodisperse or by using the Doi fluctuation model. The model appears to break down for a more polydisperse sample . This study indicates that it may be possible to use the Doi-Edwards theory to explain the viscoelastic behavior of narrow MWD polybutadienes without introducing any new concepts into the theory (fluctuations, constraints release, etc.).     

化学镀耐磨自润滑Ni-P复合镀层的摩擦磨损性能

利用化学复合镀技术制备了Ni-P-碳纳米管(Ni-P-CNTs)和Ni-P-无机类富勒烯WS2[Ni-P-(IF-WS2)]复合镀层,考察了复合镀层的减摩抗磨性能.结果表明,Ni-P-CNTs和Ni-P-(IF-WS2)复合镀层的减摩抗磨性能优于化学镀Ni-P和Ni-P-石墨镀层,其原因在于Ni-P-CNTs化学复合镀层中的碳纳米管具有优异力学性能和同轴石墨纳米管结构,而Ni-P-(IF-WS2)化学复合镀层中的IF-WS2具有封闭层状类富勒烯球形结构,二者均具有优异的自润滑性能.     

冲击速度和磨粒粒度对FeCrAl/WC复合涂层冲蚀性能的影响

采用粉芯丝材作为原料,利用高速电弧喷涂技术制备了具有良好抗高温冲蚀磨损性能的FeCrAl/WC复合涂层;考察了650℃下冲击速度和磨粒粒度对复合涂层高温冲蚀磨损性能的影响.结果表明,复合涂层和20G锅炉钢的耐高温冲蚀磨损能力随着磨粒粒度的增加而有所提高;30°攻角下冲蚀率随磨粒粒度的变化速率比90°攻角下的小;同20G锅炉钢相比,复合涂层对速更加敏感,速度越低,FeCrAl/WC复合涂层的抗冲蚀磨损性能越好.     

Local Rules: Emergence on Organizational Landscapes

This paper proposes that the theory of local rules provides a model for explaining organizational behavior as an emergent property of a fitness landscape. While local rule theory has its genesis in evolutionary biology, this paper links it to work in computational mathematical organizational theory. It further proposes that there are conditions, characterized by coadaptation, under which rules will survive in relatively stable forms, and other conditions, characterized by competition, under which local rules will change. The paper then discusses how catastrophe analysis can provide insights into changing patterns of organizational interactions. A discussion of methodology outline shows developments in agent-based simulation modeling can contribute to the development of local rule theory.     

The “decaying springs” model for irreversibility in polymer melts

In this work, entanglements in a polymer melt are modeled as a system of parallel springs which form and decay spontaneously. The springs are assumed to be nonlinear, and a certain fraction of them is torn apart by a certain strain.Based on these assumptions, a model of behavior in simple shear is developed. This model is shown to predict a behavior comprising that of a Wagner fluid, and is generalized to a tensorial model of single integral type. The integrand depends on a product of a material function, modeling reversible behavior, and a material functional which takes irreversible processes into account.Irreversibility of network disentanglement, which may occur when deformation changes or reverses direction, can be modeled in this way. It is shown that the two well-known Wagner constitutive equations with and without irreversibility assumptions are special cases of the model developed. In case of a deformation which does not change directions, the new material function and the material functional are multiplied to yield Wagner's damping function.When the rate of spring formation is a function of temperature, the developed model is shown to predict thermorheologically simple behavior. A constitutive equation for non-isothermal flow of polymers is developed with this assumption.