粒子分离器鼓包柔性复合材料的本构模型研究

为了预测可变形粒子分离器鼓包复杂工况的力学行为,得到柔性帘线/橡胶复合材料结构的变形特性模型,基于连续介质力学的理论,建立了一种考虑帘线/橡胶之间剪切应变能的帘线/橡胶复合材料本构模型,通过ABAQUS的UANISOHYPER_INV接口编写各向异性超弹性材料的本构子程序,形成有效的帘线/橡胶复合材料的变形行为预测方法。结合橡胶材料Mooney—Rivilin本构模型,基于大变形不可压缩方法处理橡胶试验数据,运用最小二乘法拟合单轴拉伸试验数据,得到橡胶材料的参数C10=-0.27MPa与C01=1.12MPa;在橡胶超弹性本构的基础上,建立了帘线/橡胶复合材料的各向超弹性本构模型,并通过单轴拉伸试验拟合帘线和剪切应变能的参数;并进行单轴拉伸试验验证帘线/橡胶复合材料的各向超弹性本构模型。结果表明:拉伸变形量在20%内,数据吻合较好,进一步证明所建本构模型的准确性,为可变形粒子分离器鼓包有限元仿真分析奠定理论基础。

Combined torsional buckling of double-walled carbon nanotubes with axial load in the multi-field coupled condition

The present study has theoretically investigated the combined torsional buckling of double-walled carbon nanotubes (DWCNTs) with axial load in the multi-field coupled condition. The effects of torsion, axial load, thermal-electrical change, surrounding elastic medium and the Van der Waals forces are all taken into consideration. The governing equation of buckling for CNTs subjected to thermo-electro-mechanical loadings has been established based on an elastic shell model of continuum mechanics. Reasonable simplifications are made to get the explicit expression of the critical buckling shear stress of DWCNTs, and numerical experiments are conducted for further research. It is shown that under certain electric and temperature field the critical buckling shear stress of DWCNTs only depends on the wave number of buckling modes. On the other hand, all the related impact factors have enormous influence on the critical buckling shear stress under a certain buckling mode. The critical buckling shear stress changes linearly with the axial-to-shear stress ratio, as well as the thermal and electric change. Axial compression tends to make DWCNTs unstable, while axial tension benefits the buckling stability. The critical buckling shear stress is directly proportional to the applied voltage. At room or lower temperature, the critical shear stress for infinitesimal buckling increases as the temperature change increases, while it decreases at a higher temperature. The conclusions are useful for the design of nano-structures related to the buckling stability of DWCNTs.

Application of Lagrange＇s equation to rigid-elastic coupling dynamics

A consistent focus in theoretical mechanics has been on how to apply Lagrange's equation to continuum mechanics.This paper uses the concept of a variational derivative and its laws of operation to investigate the derivation of Lagrange's equation,which is then applied to nonlinear elasto-dynamics.In accordance with the work-energy principle and the energy conservation law,kinetic and potential energies are proposed for rigid-elastic coupling dynamics,whose governing equation is established by manipulating Lagrange's equation.In addition,case studies are used to demonstrate the application of the proposed method to spacecraft dynamics.

A New Dynamic Model for a Flexible Hub-Beam System

In this paper,a new dynamic model for the flexible hub-beam system is proposed by using the principle of continuum medium mechanics and the finite element discretization method.In the proposed model,the coupling deformation of any element of the beam is only related with the nodal coordinates of this element.So this model is suitable to the rotating beam in an arbitrary shape.Numerical examples of slender beams in straight and irregular shapes are carried out to demonstrate the validation of the proposed model.Simulation results indicate that the proposed model can be used valid for dynamic description of flexible rotating beam in irregular shape, and for both low and high rotation speeds.

A macroscopic constitutive model of shape memory alloy considering cyclic effects

This paper presents a macroscopic constitutive model reproducing the hysteretic behaviors of the superelastic shape memory alloy (SMA) under cyclic loading. The progressive increase of residual strain with the increased cycle number in such materials is assumed to be a consequence of the progressive increase of residual stress-induced martensitic volume fraction upon the cyclic effects. The progressive decrease of phase transformation critical stresses with the increased cycle number in such materials is assumed to be a result from the progressive increase of phase transformation critical temperatures upon the cyclic effects. A cyclic evolution equation is supposed to describe the influences of cycle effects on the material properties of the SMA under cyclic loading. A phase transformation equation expressing the phase transformation behaviors of the SMA under cyclic loading is established based on the differential relationship between martensitic volume fraction and the free energy increment of phase transformation. A mechanical constitutive equation predicting the mechanical characteristics of the SMA under cyclic loading is developed on the basis of thermodynamics and continuum mechanics. The cyclic evolution equation, phase transformation equation, and mechanical constitutive equation together compose the presented macroscopic constitutive model considering cyclic effects. Results of the numerical simulations illustrate that it can well reproduce the superelastic hysteretic behaviors of the SMA under cyclic loading.