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881.
松弛与蠕变力学特性转换关系的研究 总被引:8,自引:0,他引:8
本文首先论述了拉伸应力松弛模量E(t)与拉伸蠕变柔量D(t)之间的近似与精确转换关系式,提出一种诊断D(t)的数值积分算法,通过应力松弛模量实验给出一种固体推进剂E(t)和D(t)的实测与转换计算结果,计算结果有较小的误差具有重要的实用价值。 相似文献
882.
In this paper, characteristics of the interface crack-tip stress and electric displacement fields in transversely isotropic piezoelectric bimaterials are studied. The authors have proven, within the framework of the generalized Stroh formalism for piezoelectric bimaterials, that there is no coexistence of the parameters (oscillating) and κ (non-oscillating) in the interface crack-tip generalized stress field for all transversely isotropic piezoelectric bimaterials. This leads to the classification of piezoelectric bimaterials into one group that exhibits the oscillating property in the interface crack-tip generalized stress field and the other that does not. Fifteen (15) pair-combinations of six (6) piezoelectric materials PZT-4, PZT-5H, PZT-6B, PZT-7A, P-7, and BaTiO3, which are commonly used in practice, are numerically analyzed in this study, and the results backup the above theoretical conclusions. Moreover, the associated eigenvectors for such material systems (with either =0 or κ=0) are also obtained numerically, and the result show that there still exist four linear independent associate eigenvectors for each bimaterial. 相似文献
883.
In this paper, non-linear deformation behavior of magnetostrictive materials is studied and three magnetoelastic coupling constitutive models are developed. The standard square (SS) constitutive model is developed by means of truncating the polynomial expansion of the Gibbs free energy. The hyperbolic tangent (HT) constitutive equations, which involve a hyperbolic tangent magnetic-field dependence, are proposed to model the magnetic-field-induced strain saturation of magnetostrictive materials in the region of intense magnetic fields. A new model based on density of domain switching (DDS) is established in terms of the basic truth that magnetic domain switching underlies magnetostrictive deformation. In this model, it is assumed that the relation between density of domain switching, defined by the quantity of magnetic domains switched by per unit magnetic field and magnetic field can be described by a density function with normal distribution. The moduli in these constitutive models can be determined by a material function that is proposed to describe the dependence of the peak piezomagnetic coefficient on the compressive pre-stress for one-dimensional cases based on the experimental results published. The accuracy of the non-linear constitutive relations is evaluated by comparing the theoretical values with experimental results of a Terfenol-D rod operated under both compressive pre-stress and bias magnetic field. Results indicate that the SS constitutive equations can accurately predict the experimental results under a low or moderate magnetic field while the HT model can, to some extent, reflect the trend of saturation of magnetostrictive strain under a high magnetic field. The model based on DDS, which is more effective in simulating the experimental curves, can capture the main characteristics of the mechanism of magnetoelastic coupling deformation of a Terfenol-D rod, such as the notable dependence of magnetoelastic response on external stress and the saturation of magnetostrictive strain under intense magnetic fields. In addition, the SS constitutive relation for a general three-dimensional problem is discussed and an approach to characterize the modulus tensors is proposed. 相似文献
884.
含初缺陷复合材料圆柱曲板的动力屈曲分析 总被引:1,自引:1,他引:1
基于修正的一阶剪切变形理论,利用Hamilton原理导出包含横向剪切变形和转动惯量的复合材料长圆柱曲板的非线性动力方程,通过将位移和载荷展开为Fourier级数,把非线性偏微分方程组转化为二阶常微分方程组,并可由四阶Runge-Kutta方法数值求解,通过算例,讨论了有关因素对迭层复合材料圆柱曲板动力屈曲的影响。 相似文献
885.
等离子喷涂碳化铬-镍铬涂层的摩擦学特性 总被引:3,自引:1,他引:3
在发展新型高效节能的汽车和飞机发动机用耐磨材料中,碳化铬-镍铬涂层是很有开发前景的材料之一.为了扩大这种涂层的应用领域并为其应用提供科学依据,用MM-200磨损试验机,研究了等离子喷涂碳化铬-镍铬(质量比为3∶1)涂层分别与不锈钢、热压烧结Si3N4和石墨组成摩擦副的摩擦学特性;用扫描电子显微镜、X射线能量色散谱仪和X射线衍射技术,考察了磨痕和磨屑的形貌、元素分布和物相组成;讨论了涂层分别与给定的3种材料配副时的磨损机理.结果表明:涂层与不同材料对摩时的磨损量差别很大,磨损机理也明显不同——涂层与不锈钢对摩时的磨损表现为层状颗粒的断裂与剥离;涂层与Si3N4对摩时的磨损主要表现为涂层颗粒的断裂和断裂颗粒的脱碳氧化;石墨对涂层具有润滑作用 相似文献
886.
A stochastic-structurally based three dimensional finite-strain damage model for fibrous soft tissue
José F. Rodríguez Fernando Cacho José A. Bea Manuel Doblaré 《Journal of the mechanics and physics of solids》2006,54(4):864-886
A fully three dimensional finite-strain damage model for fibrous soft tissue is developed. The model assumes uncoupled contributions for the matrix and collagen fibers, and uncoupled bulk and deviatoric response over any range of deformations. A simple isotropic damage mechanism within the framework of continuum damage mechanics has been used to describe the softening behavior under deformation for the matrix. On the other hand, statistical aspects related to the length distribution of the reinforcing fibers lead to a damage model for the reinforcing material. As a result, a general theoretical framework for constitutive modeling of biological soft tissue with continuum damage is obtained. A theoretical example consisting of a biaxial test of a soft tissue reinforced with two families of collagen fibers has been considered to demonstrate the capabilities of the proposed model and to study the sensitivity to changes in the statistical parameters associated with the reinforcing material. Also, a preliminary numerical example is included to demonstrate the model on a inhomogeneous boundary value problem. Results show that the model is able to capture the typical stress-strain behavior observed in fibrous soft tissue and seems to confirm the soundness of the proposed formulation. 相似文献
887.
888.
889.
Wenyi YanNoel P. O'Dowd Esteban P. Busso 《Journal of the mechanics and physics of solids》2002,50(3):449-470
A computational approach is proposed to predict the sliding wear caused by a loaded spherical pin contacting a rotating disc, a condition typical of the so-called pin-on-disc test widely used in tribological studies. The proposed framework relies on the understanding that, when the pin contacts and slides on the disc, a predominantly plane strain region exists at the centre of the disc wear track. The wear rate in this plane strain region can therefore be determined from a two dimensional idealisation of the contact problem, reducing the need for computationally expensive three dimensional contact analyses. Periodic unit cell techniques are used in conjunction with a ratchetting-based failure criterion to predict the wear rate in the central plane strain region. The overall three dimensional wear rate of the disc is then determined by scaling the plane strain wear rate with a conversion factor related to the predicted shape of the wear track. The approach is used to predict pin-on-disc test data from an Al-Si coating using a tungsten carbide pin. The predicted results are found to be consistent with measured data. 相似文献
890.
Y. Ootao R. Kawamura Y. Tanigawa T. Nakamura 《Archive of Applied Mechanics (Ingenieur Archiv)》1998,68(10):662-676
Summary A neural network model is applied to optimization problems of material compositions for a functionally graded material plate
with arbitrarily distributed and continuously varied material properties in the thickness direction. Unsteady temperature
distribution is evaluated by taking into account the bounds of the number of the layers. Thermal stress components for an
infinite functionally graded material plate are formulated under traction-free mechanical conditions. As a numerical example,
a plate composed of zirconium oxide and titanium alloy is considered. In the optimization problem of minimizing the thermal
stress distribution, the numerical calculations are carried out making use of the neural network. The optimum material composition
is determined by taking into account the effect of temperature-dependence of material properties. The results obtained by
neural network and ordinary nonlinear programming method are compared.
Received 3 March 1998; accepted for publication 22 May 1998 相似文献