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根据黏弹性材料力学模型的假设,选取线性黏弹性力学模型中四元件模型的等效模型和非线性黏弹性力学模型中的欧林模型,基于材料相同但增强织物组织结构不同的3 种试样进行的应力松弛试验,通过MatLab 软件计算,拟合出四元件模型的等效模型及欧林模型的方程参数,并采用MatLab 软件计算机画图显示实测点和拟合曲线,从而进一步比较、分析得出最适合压延类柔性复合材料松弛性能的力学模型,证明PVC 压延类柔性复合材料具有非线性黏弹性的力学特征,属于非线性黏弹性的范畴,且增强织物的组织结构对这一属性影响不明显。 相似文献
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针对现有纱线拉伸力学模型描述不准确问题,以分数阶微积分模型对纱线拉伸行为进行分析。首先,引入分数阶微积分理论改进的黏壶模型建立了分数阶纱线蠕变模型,使用XL-2型纱线强伸度仪对不同线密度及不同张力纱线进行蠕变实验,获得纱线蠕变的全过程曲线。通过对不同线密度下的试验曲线进行回归分析得到了模型参数以及蠕变模型参数与施加张力大小的变化关系。最后,利用不同模型对不同张力的纱线蠕变曲线进行拟合和预测。结果表明:分数阶纱线蠕变模型,相比于三元件模型、整数阶模型和Burgers模型,具有结构简单、参数少的特点,并且对纱线蠕变的拟合和预测也具备较高的精度。 相似文献
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Anterior cruciate ligaments (ACL) have to meet a number of physiological and biomechanical requirements. Most of the permanent prostheses that have been developed suffer from fatigue, creep, and mechanical failure. This study aims to develop a new braided synthetic ligament which offers a high elasticity ensuring a long-term mechanical performance. Two braided structures were designed: a biaxial quadruple braid and a triaxial quadruple braid incorporating polyurethane filaments. The mechanical properties of these structures were measured and compared to those of the natural ligaments. The elastic recovery under a traumatic force was also studied in order to compare the elasticity of the manufactured samples. The obtained results showed that the elastic recuperation was improved, thanks to the incorporation of polyurethane yarns. These yarns provide prostheses with mechanical properties that closely match those of the native ACL. 相似文献
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The changes in the texture of cylindrical samples of potato tissues immersed in water at 60, 70, 80 and 90C for up to 80 min were monitored at each temperature in terms of tangent modulus of elasticity in axial and radial compression tests, and elasticity and viscosity parameters in creep and stress relaxation tests. The magnitude of all mechanical test parameters decreased with an increase in heating time and temperature. The creep and stress relaxation responses of individual potato samples were adequately represented by respective mechanical models (R2 = 0.94 to 0.99). The mechanical test parameters followed apparent first-order degradation kinetics due to the effect of thermal softening, and the rate constant was used as an index of the sensitivity of a mechanical test. The radial compression test was relatively more sensitive than the axial test. Based on an overall comparison, the parameters from creep and stress relaxation tests were found to be the most sensitive in describing the textural changes during thermal softening of potatoes. 相似文献
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为探究不同PTT/PET自卷曲长丝织物在后整理中的表现及其最终成品的弹性性能,选用3个厂家生产的PTT/PET自卷曲长丝试织织物,并在相同工艺条件下进行染整处理,再与氨纶织物进行对比,得到4种织物的质量损失率、纬向染缩率、弹性伸长率、弹性回复率。结果表明:单丝纤度越大,质量损失率越小,染色率越大;织造密度越大,质量损失率越小;弹性伸长率越大,弹性回复率越小。通过光学显微镜、扫描电镜观察及DSC辅助分析发现,PTT/PET复合丝由于单丝比较细,比表面积大,在染整处理过程中受到碱液腐蚀过大而发生2种组分分离的现象,从而失去了双组分丝应有的高弹性。 相似文献
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The mechanical and physical properties of modified timber were assessed by experimental work. The timber was modified using three different methods: acetylation with acetic anhydride, modification with methylated melamine formaldehyde resin and heat treatment in an oil bath. The wood material was sapwood of Scots pine (Pinus sylvestris) with dimensions of 45×70×1100 mm. A total of 99 specimens were included in this study. The following properties and their inter-relations were studied: density, modulus of elasticity (MOE), bending creep deflection and relative creep. It was found that all the modifications successfully reduced the relative creep. However, the performance properties of modified timber ought not to be calculated on the basis of density, as is the case for untreated wood. On the other hand, the long-term performance of modified timber can be assessed by its initial MOE and the difference in equilibrium moisture content (EMC) between two climates. 相似文献
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AbstractA detailed identification, using X-ray microtomography, of the filament trajectories within twisted single and multi-ply continuous filament yarns is presented in this article, to accurately determine the distributions of orientations of filaments which govern the mechanical behavior of those yarns and the mechanisms of failure. The resolution of the images obtained by means of the X-ray microtomography experimental setup associated to the capabilities of an in-house developed image processing software allowed the reconstruction of the trajectories of almost all filaments within different yarn specimens. Various structural information are derived from these trajectories, dealing in particular with the orientation of individual segments of filaments with respect either to the ply trajectory or to the yarn axis. Compared to orientation distributions provided by different analytical models available in the literature, those resulting from reconstructed trajectories show similar global trends, while providing more details in peripheral regions and regions close to contact zones between plies. Maps of radial and spatial distributions of orientations provide a comprehensive representation of how filaments are oriented within the plies, which gives valuable insight into the inner structural arrangement of fibers which is one of the sources of nonlinearities in the mechanical behavior of filament yarns. 相似文献
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Spaghetti enriched with resistant starch was produced to increase the dietary fibre intake of consumers. In the product base
it was compared to bran and control spaghetti regarding to viscoelastic properties. Viscoelastic properties were tested by
relaxation and creep tests by using TA-XT2i texture analyser. The viscoelastic properties gave structural information. Relaxation
and creep data were analysed by generalized Maxwell (two- and three-termed), Peleg & Normand, Burgers and Peleg models, respectively.
For relaxation three-termed Maxwell and for creep behaviour Burgers model represented viscoelastic behaviour satisfactorily.
In general, bran spaghetti was found to have the lowest elasticity. All the samples started to loose their elasticity as cooking
time proceeded and it became easy to deform them. Instrumentally, spaghetti with resistant starch was found to be better than
bran enriched spaghetti. 相似文献
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Bending creep performance of modified timber 总被引:1,自引:0,他引:1
Hannah Epmeier Marie Johansson Robert Kliger Mats Westin 《Holz als Roh- und Werkstoff》2007,65(5):343-351
The present study is a supplement to Epmeier and Kliger (2005), which investigated the effect of three different modification methods (acetylation, modification with methylated melamine resin and heat treatment in vegetable oil) on four material properties (density, modulus of elasticity (MOE), creep deflection and relative creep) and their inter-relations. In this study, another modification method (furfurylation) and four additional material parameters (“relative stiffness”, i.e. MOE/density, moisture content, change in moisture content and anti-creep efficiency) and their correlations are included. In addition, the creep curves were analysed to assess the development of bending creep performance. The properties were assessed by experimental work on 132 specimens of Scots pine sapwood with dimensions of 45×70×1100 mm3. It was found that modification leads to significant changes in material properties. Furfurylation increases density and reduces creep deflection, relative creep and moisture content. Modified timber tends to deflect and creep significantly less than untreated timber. However, the extent of reduction in relative creep appears not to be related to the extent of reduction in creep deflection. Initial deflection and/or modulus of elasticity are suitable for predicting the creep deflection of untreated and modified timber. 相似文献
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长丝变形纱的紊乱结构 总被引:3,自引:3,他引:0
化纤长丝的变形加工是使规则排列的长丝束变成具有一定稳定度、结构排列相对混乱的过程,因而可以将变形纱在结构上的次序性特征定义为紊乱结构。紊乱结构是变形纱的基本结构特征之一,较好地解释了变形纱诸多物理现象。变形纱紊乱结构的数学模型可从熵变的角度出发,并最终表达线性体系中单丝片段无序性与其空间状态体积数的关系,同时也可为三维直角坐标系中单丝片段分布的密度函数。相对紊乱度、相对熵变值及变形纱膨松度指数是重要的紊乱度参数,可通过测量变形线性体的线密度、表观直径等参数进行计算。 相似文献