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41.
The transient recoverable deformation ratio after melt elongation at various elongational rates and maximum elongations was
investigated for pure polystyrene and for a 85 wt.% polystyrene/15 wt.% linear low density polyethylene (PS/LLDPE 85:15) blend
at a temperature of 170 oC. The ratio p of the zero shear rate viscosity of LLDPE to that of PS is p = 0.059 ≈ 1:17. Retraction of the elongated LLDPE droplets back to spheres and end-pinching is observed during recovery.
A simple additive rule is applied in order to extract the contribution of the recovery of the elongated droplets from the
total recovery of the blend. In that way, the recoverable portion of the PS/LLDPE blend induced by the interfacial tension
is determined and compared with the results of a theory based on an effective medium approximation. The effective medium approximation
reproduces well the time scale of the experimental data. In addition, the trends that the recoverable deformation increases
with elongational rate and maximum elongation are captured by the theoretical approach. 相似文献
42.
V. I. Odinokov A. M. Sergeeva 《Journal of Applied Mechanics and Technical Physics》2006,47(2):266-273
The spatial problem of determining the stress-strain state of an ice plate of finite thickness broken by a patented method
is solved using the theory of small elastoplastic strains and a proven numerical method.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 2, pp. 139–146, March–April, 2006. 相似文献
43.
冻结法施工在上海隧道建设中(如隧道旁通道、地下泵房等的设计与施工)得到广泛应用,也曾引发过严重的地质灾害(如上海地铁4号线外滩段的地质灾害)。因此安全、经济、合理地将冻结法用于上海软土地区隧道建设中已经成为上海工程建设中的一个重要的研究课题。本文以上海复兴东路越江隧道旁通道冻结法施工中遇到的第⑥层粉质粘土及第⑦层粉细砂为研究对象,针对设计冻结壁重要强度参数无侧限瞬时抗压强度,进行了室内试验研究,揭示了两种土的冻结强度随温度的变化关系,同时研究了粉细砂的冻结强度随含水率的变化规律。 相似文献
44.
A method is developed for determining the three displacement components by the method of holographic interferometry from two
interferograms used to measure residual stresses by hole drilling. The displacements are determined at the intersection points
of the principal axes and the hole boundary. The method is experimentally validated by measuring the stress state of a plate
under uniaxial tension
__________
Translated from Prikladnaya Mekhanika, Vol. 41, No. 8, pp. 111–117, August 2005. 相似文献
45.
The paper is concerned with a formulation of anisotropic finite strain inelasticity based on the multiplicative decomposition of the deformation gradient F=FeFp. A major feature of the theory is its invariance with respect to rotations superimposed on the inelastic part of the deformation gradient. The paper motivates and shows how such an invariance can be achieved. At the heart of the formulation is the mixed-variant transformation of the structural tensor, defined as the tensor product of the privileged directions of the material as given in a reference configuration, under the action of Fp. Issues related to the plastic material spin are discussed in detail. It is shown that, in contrast to the isotropic case, any flow function formulated purely in terms of stress quantities, necessarily exhibits a non-vanishing plastic material spin. The possible construction of spin-free rates is discussed as well, where it is shown that the flow rule must then depend not only on the stress but on the strain as well. 相似文献
46.
采用我国混凝土规范GB50010-2002规定的混凝土应力一应变关系,考虑混凝土强度、构件长细比及混凝土徐变,从构件的非线性理论出发对钢筋混凝土轴心受压构件的承载力进行了研究,给出了混凝土构件临界状态时的构件边缘应变和纵向弯曲系数的计算公式。研究表明,徐变对轴心受压构件的承载力有很大影响。当不考虑混凝土徐变时,按本文公... 相似文献
47.
Abstract An Equipement has been built for the generation of uniaxial pressure and of bending stress respectivety directly in the cavity of an X-band ESR spectrometer. Changes of the structure of paramagnetic centres (Fe3+ on Al3+ sites) could be detected in materials with a high content of corundum under the innuence of pressure and bending stress. The objects of investigation are not only suitable model system but also have practical relevance. The Fe3+-ions, incorporated in the materials react very sensitive on mechanically or thermally induced changes of the state of the matrix. They give insight into the materials at a microscopic level The interpretation of the observed intensity and shift effects is possible on the basis of an adequate spin-hamiltonian. 相似文献
48.
49.
为研究层状复合岩石高温作用下的力学特性,对相似材料制备的层状复合岩石进行20℃(室温),100℃,200℃和300℃热处理,并开展单轴压缩试验获取其物理力学参数。结果表明,随着温度升高,层状复合岩石质量变化率与体积膨胀率呈上升趋势,且在100℃时增幅明显。拟合各力学参数的经验公式发现,峰值强度及弹性模量趋于劣化并呈线性降低,峰值应变与温度成正相关。随着温度升高,层状复合岩石呈剪切–滑移型破坏,单一类岩石由剪切破坏向张拉–剪切破坏转化,破坏时微裂纹数量增多,在300℃时延性特征显著。引入考虑温度效应的岩石本构模型并拟合了不同温度下的应力应变曲线,该模型较好地表征了热处理后层状复合岩石的损伤演化规律及破坏特征,合理地揭示了层状复合岩石高温作用后的损伤机理。
相似文献50.
Shahida Sadiqi Muhammad Hamza Farooq Ali Sadia Alam Qismat Shakeela Shehzad Ahmed Asma Ayaz Sajid Ali Saddam Saqib Fazal Ullah Wajid Zaman 《Molecules (Basel, Switzerland)》2022,27(19)
Some soil microbes, with their diverse inhabitance, biologically active metabolites, and endospore formation, gave them characteristic predominance and recognition among other microbial communities. The present study collected ten soil samples from green land, agricultural and marshy soil sites of Khyber Pakhtunkhwa, Pakistan. After culturing on described media, the bacterial isolates were identified through phenotypic, biochemical and phylogenetic analysis. Our phylogenetic analysis revealed three bacterial isolates, A6S7, A1S6, and A1S10, showing 99% nucleotides sequence similarity with Brevibacillus formosus, Bacillus Subtilis and Paenibacillus dendritiformis. The crude extract was prepared from bacterial isolates to assess the anti-bacterial potential against various targeted multidrug-resistant strains (MDRS), including Acinetobacter baumannii (ATCC 19606), Methicillin-resistant Staphylococcus aureus (MRSA) (BAA-1683), Klebsiella pneumoniae (ATCC 13883), Pseudomonas aeruginosa (BAA-2108), Staphylococcus aureus (ATCC 292013), Escherichia coli (ATCC25922) and Salmonella typhi (ATCC 14028). Our analysis revealed that all bacterial extracts possess activity against Gram-negative and Gram-positive bacteria at a concentration of 5 mg/mL, efficiently restricting the growth of E. coli compared with positive control ciprofloxacin. The study concluded that the identified species have the potential to produce antimicrobial compounds which can be used to control different microbial infections, especially MDRS. Moreover, the analysis of the bacterial extracts through GC-MS indicated the presence of different antimicrobial compounds such as propanoic acid, oxalic acid, phenol and hexadecanoic acid. 相似文献