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排序方式: 共有208条查询结果,搜索用时 0 毫秒
1.
S.T. Mileiko V.M. Kiiko K.A. Khvostunkov 《Theoretical and Applied Fracture Mechanics》2006,45(1):41-45
A micromechanical model of island-type fibre/matrix interface is described and experimental data are represented and analysed. Changes in the interface strength during a cycle loadings and, correspondingly, changes in the creep resistance of a composite due the island-like scheme of the fibre/matrix interface are described. 相似文献
2.
钇对Ti-1100高温钛合金热稳定性和蠕变行为的影响 总被引:3,自引:1,他引:3
量了Ti1100和Ti1100/01%Y(质量分数)高温钛合金在600℃/100h空气中暴露后的拉伸性能及在600℃/150MPa/100h条件下的蠕变性能,利用透射电镜观察了合金室温及蠕变后的组织。结果表明,Ti1100合金加入01%的Y后,由于原始β晶粒得到细化,明显改善了其热稳定性;固溶在基体中的硅原子阻碍位错滑移和攀移,使蠕变中的回复过程难于实现;稀土还抑制α2相的长大,所形成的氧化物也阻碍位错的运动。这些均有利于提高Ti1100合金的抗蠕变性能。 相似文献
3.
对已经商品化的Perkin-Elmer TMS-2型热机分析仪进行改进,用来测量聚合物材料的热释蠕变行为。按照7SCr分步加载的程序,用弯曲法测量了-83~300℃温度范围内低密度聚乙烯的玻璃化转变松弛过程,并从TSCr谱上计算其相应的分子参数,实验结果与用扭转的TSCr方法所得结果相等,因此这是一种研究聚合物材料松弛行为的方便可行的技术。 相似文献
4.
Spiders in electro-dynamic loudspeakers are most commonly concentrically corrugated fabric disks, and their viscoelastic behaviors affect the loudspeaker reproductions. A noncontact dynamic measuring technology is presented by a subwoofer closed box to excite the tested spiders pneumatically with a Laser Doppler Vibrometer (LDV) to measure the velocity of the moving spiders. Correlation techniques were employed to get an accurate and reliable acoustical transfer function between the measured velocity and sound pressure. The Young’s moduli of the tested spider composite materials were derived from the measured vibration modes. The creep effect and the level dependent behaviors of tested spiders were investigated. The results indicate that, the Young’s moduli of the tested spiders are frequency dependent. The mechanical stiffness increases with a small slope in low frequency range while a large slope in high frequency range. The loss factor exhibits the maximum around the resonance frequency, and after that it decreases with increasing frequency. The effective stiffness has a monotonic decrease with input voltage levels and the harder the spider, the less stiffness changes with input levels. 相似文献
5.
Kacem Saï 《International Journal of Plasticity》2011,27(2):250-281
The paper gives a review of the main features introduced in the multi-mechanism models, of the present possibilities and of further developments.In the two last decades, various materials and mechanical effects were studied using multi-mechanism model types. Particular attention was given to the possible link between the mechanism definitions and the physical deformation sources. The main results of these works are first recalled. Propositions of future development for the multi-mechanism models are finally given. 相似文献
6.
Abstract Blends of poly(pyridinium ethyl methacrylate perchloride) and poly[oligo(oxyethylene) methacrylate-co-acrylamide] were prepared, and the ionic conductivity and mobility of the blends were investigated. Results indicate that both the transference of perchlorate anion and the dissociation of the polymeric salt in the comblike polyether obey the thermoactivation mechanism, and that the perchlorate anion in the blends is free. 相似文献
7.
《Soft Materials》2013,11(2-3):125-144
Abstract New procedures involving depth‐sensing indentation are used to measure the submicron scale elastic modulus, hardness, viscosity, and activation energy and volume for creep of amorphous selenium below glass transition. The accurate measurement of Young's modulus in a highly viscoelastic situation using depth‐sensing indentation remains a challenge, and a creep correction procedure is employed here to measure the modulus. The measured Young's modulus exhibits a strong decreasing trend from ~10 GPa to 4.4 GPa as temperature increases from ~302 K to 309 K, in reasonably good agreement with bulk behavior. Two new procedures are also proposed here to measure the viscosity. The measured shear viscosity decreases from ~1×1012 Pa‐s to ~2×1010 Pa‐s when the temperature increases over the same range, and the variation with temperature is found to obey an Arrehnius rate equation. The activation energy for the viscous creep process is found to be ~463 kJ/mol. Both the viscosity and the activation energy are lower than the bulk values, and this is thought to be due to the much higher stress levels of over 200 MPa involved in the nanoindentation experiments here. The apparent activation volume exhibits a rising trend from 1.04×10?31 to 2.35×10?30 m3 over the same temperature range. 相似文献
8.
A new method has been proposed and verified to measure the viscoelastic properties of polymers by nanoindentation tests. With the mechanical response of load–displacement curves at different loading rates, the parameters of creep compliance and relaxation modulus are calculated through the viscoelastic contact model. Dynamic thermomechanical analysis (DMA) tests are conducted to compare the results by the proposed technique. The results show that the correlation coefficients between DMA tests and the new method are above 0.9 in the entire range, which verified the feasibility of the method. The loading curves fitted by the model are identical to the experimental curves within the discrete points and so it shows that this technique is more suitable for general linear viscoelastic materials. Numerical creep tests are carried out to examine the effectiveness of the proposed method by input the Prony series calculated by the three-element Maxwell model and the viscoelastic contact model. The good agreement shows that the proposed technique can be applied in practice. 相似文献
9.
This work aims to determine the tensile set behavior of a silicone rubber under different stress magnitudes and temperatures through digital image correlation implemented in an improved creep experimental set-up. Creep-recovery strains were measured with time at 20, 40 and 60 °C under tensile strengths of 98.1, 196.2 and 394.3 kPa, respectively. The behavior of creep and recovery strain with time at the different stress magnitudes and temperatures was successfully obtained by the experiments. The corresponding elastic and viscous components of the material for each condition were determined from the results. Overall, all obtained creep behaviors matched with the behavior of a four-element model of creep-recovery. The increase of temperature generated an increase of creep compliance at the three loads, but the increase of tensile load produced a decrease of creep compliance for the three temperatures. The strain was not recovered entirely in any case for the test time stated. 相似文献
10.
Microfibrillar composites (MFC) with in-situ generated short polymeric fibres feature, unlike composites containing inorganic rigid fibres/particles, lower creep resistance in comparison with analogous blends containing spheres. Further attribute is unprecedented decrease in creep resistance of the blend by graphite nanoplatelets (GNP). Explanation of this behaviour of the HDPE/PA66/GNP system consists in characterization of structure and finite element analysis (FEA) „mapping“ the effect of reinforcement and interface parameters on creep behaviour. Lowering of reinforcement modulus and its viscoelasticity may lead to worse creep resistance of fibrous composites. FEA also indicates marked negative effect of the soft interface, i.e. GNP-reduced crystallinity of HDPE near the interface, on creep resistance of the spheres-reinforced system in contrast to MFC. Structural changes are indicated by polarized light microscopy, SEM and TEM. The results reveal so far unknown complexity of the performance of polymer/polymer composites which may cause unprecedented antagonistic effects. 相似文献