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91.
The invariants in the K-BKZ constitutive equation for an incompressible viscoelastic fluid are usually taken to be the trace of the Finger strain tensor and its inverse. The basis for this choice of invariants is not derived from the K-BKZ theory, but rather is due to the perception that this is the most natural choice. Research into using other sets of invariants in the K-BKZ equation, such as the principal stretches or the eigenvalues of the Finger strain tensor (i.e., the squares of the principal stretches) is relatively new. We attempt here to derive a K-BKZ equation based on the squares of the principal stretches that models the behavior of a low-density polyethylene melt in simple shear and uniaxial elongational deformation. In doing so, two assumptions are made as to the form of the strain-dependent energy function: first, that there is a function f(q) such that the energy function can be written as the sum of f(q
i
),i = 1, 2, 3, where the q
i
'sare the squares of the principal stretches, and second that f is a power law. We find that the K-BKZ equation resulting from these two assumptions is inadequate to describe both the shear and elongational behavior of our material and we conclude that the second of the above assumptions is not valid. Further investigation, including predictions of the second normal stress difference and some finite element calculations reveals that the first assumption is also invalid for our material. 相似文献
92.
The paper presents a nonlinear model describing vibration of the landing gear relative to the fuselage. The model is intended
to analyze the dynamic stability of nonswiveling main-gear wheels. The model is used to show that the lateral component of
the fuselage speed has a significant effect on the critical shimmy speed
__________
Translated from Prikladnaya Mekhanika, Vol. 42, No. 9, pp. 134–142, September 2006. 相似文献
93.
抗磨可靠性寿命的加速试验与预测 总被引:3,自引:0,他引:3
在工程实际中,对新机器零件的抗磨可靠性寿命进行评估或预测非常重要,但是,由于磨损是一种受多因素制约的随机过程,目前在实验室广泛采用的模拟磨损试验,不仅周期较长,而且预测误差也比较大。因此,提出了一种在保持磨损机相似的前提下合理选用高PV值的抗磨可靠性寿命加速试验的新方法。 相似文献
94.
用有限元自适网格控制结构应力分析的精度 总被引:1,自引:0,他引:1
本文涉及有限元结构应务分析精度控制的三个基本方面:1)自适应的有限元网格自动生成技术;2)有限元应力分析的误差估计:3)用单元尺寸场将误差分布用于形成新网格。 相似文献
95.
The life analysis of engine components needs to take into account the residual stress relaxation induced by cyclic service loads. The paper recalls a new class of constitutive equations for cyclic viscoplasticity, using a series of kinematic hardening models with thresholds. The equations are introduced within a recently enlarged thermodynamic framework. Some attention is focused to the relations with multisurface approaches and to a specific determination procedure of the model parameters. The new model is applied to the calculation of the near surface residual stress relaxation after shot peening, when the structure is submitted to cyclic service loads. The simulated stabilized residual stresses are in good accordance with experimental results obtained on an N18 disk alloy at 650°C. In comparison, the classical model without threshold predicts the complete vanishing of the residual stresses, which is not satisfactory. 相似文献
96.
斜拉桥塔锚固区光弹性应力分析与等倾线图像处理 总被引:1,自引:2,他引:1
本文采用光弹性冻结应力法,对独塔斜拉桥塔锚固区进行了应力分析,给出了有关截面的边界应力分布及主应力迹线,从而为优化工程设计提供了重要的参考依据。本文还提出了一种新的提取等倾线的方法──图像对数增强相减法,实现了等倾线与等差线条纹的分离,同时使条纹得到了细化,提高了处理等倾线的速度与准确度。编制了自动绘制主应力迹线的程序,利用它绘制了桥塔截面的次主应力迹线。 相似文献
97.
本文用三维光弹性法,对地铁车站地下拱型结构进行了实验应力分析并绘出主应力迹线。文中还提出对加压用乳胶气囊进行高温、高压预处理工艺,使乳胶气囊和模型曲面很好地吻合,从而提高了加载的准确度。 相似文献
98.
99.
100.
In this paper, we generalize the notion of functional graph. Specifically, given an equation with variables X and Y over a finite field of odd characteristic, we define a digraph by choosing the elements in as vertices and drawing an edge from x to y if and only if . We call this graph as equational graph. In this paper, we study the equational graph when choosing with a polynomial over and λ a non-square element in . We show that if f is a permutation polynomial over , then every connected component of the graph has a Hamiltonian cycle. Moreover, these Hamiltonian cycles can be used to construct balancing binary sequences. By making computations for permutation polynomials f of low degree, it appears that almost all these graphs are strongly connected, and there are many Hamiltonian cycles in such a graph if it is connected. 相似文献