Mod.9Cr-1Mo不锈钢循环软化特性分析

对Mod.9Cr-1Mo不锈钢550℃下循环软化特性的应变范围和路径相关性进行了分析,并采用ABAQUS软件对Mod.9Cr-1Mo不锈钢的循环软化特性进行了模拟。结果表明,Mod.9Cr-1Mo不锈钢在550℃不同路径、不同应变范围下均表现出了明显的循环软化现象,应变路径对循环软化特性的影响大于应变范围的影响。其次,采用非线性随动硬化与各向同性硬化的Chaboche混合模型进行了不同条件下循环软化特性模拟,单轴不同应变范围下的模拟结果与实验结果前100周次内最大平均误差仅为4.2%。针对主应变比为-0.54、-0.64和-0.80的3种多轴路径下的软化特性进行模拟计算,得到的正应力与实验结果一致性较好;剪应力的模拟结果与实验结果误差略大于正应力的结果,但100周次内平均误差最大值仍仅为3.2%。     

沉积物中导热体周围水合物分解范围研究

沉积物水合物在热源周围的分解范围是水合物热开采以及相关灾害分析的重要基础数据. 该文针对平面内边界有恒温热源的水合物热分解范围问题进行了理论分析和四氢呋喃水合物沉积物模型实验,并将两者结果进行了对比. 结果表明：沉积物水合物最大分解范围主要取决于热源与环境温度的温差;热源周围水合物热分解最大范围的理论值与实验值接近,误差小于5%.     

F4/203A型锰铜压力计对撞击载荷的响应

通过一组撞击载荷实验建立了F4/203A型锰铜压力计在219万巴应力范围上的标定曲线。 应用此标定曲线从锰铜压力计的首次响应确定了一组在2IC万巴应力范围上的PT FE(聚四氟乙稀)雨贡纽状态点,结果与PTFE标准雨贡纽曲线非常一致;把我们的标定曲线与国外最新结果进行了比较,这两者都进一步肯定了我们的标定结果。     

气体动力学中Гриб-Рябинин方法在水力学中的应用与推广

本文将气体力学中方法(以下简称方法)应用到水力学中去,得到了比气体力学中更好的结果。此外,本文对该法近似解的应用范围以及解的误差作了详细地分析和讨论,扩大了方法的应用范围,提高了解的精度。     

分布式光纤传感器测量数据可靠性分析方法

分析了分布式光纤传感器测量结果的可靠性,提出从应变系数和温度系数标定到分布式光纤传感器物理量测量以及结果评价的方法,设计了分布式光纤传感器的应变系数和温度系数标定装置,同时分析了应变标定装置的不确定度来源,采用基于光频域反射技术的分布式光纤解调仪进行了实验验证.应变标定范围为-5000με?5000με,温度标定范围为...     

做大范围运动复合材料板的动力学建模研究

基于经典层合板理论建立了大范围运动复合材料板的动力学方程,考虑了传统建模方法忽略的二次耦合变形量。采用有限元法对复合材料板进行离散,利用Lagrange方法推导了大范围运动复合材料板的动力学方程。通过编制matlab程序计算了带中心刚体的旋转复合材料板的变形,将得到的结果分别与不计耦合变形量的传统方法的计算结果进行比较,随着转速的提高,本文方法收敛,而传统方法趋于发散。研究了铺层角度对作大范围运动复合材料板变形影响以及复合材料板和各向同性板在经历相同运动时角点最大变形的差异。     

大变形柔性多体系统非线性动力学数值仿真与实验研究

提出了一种作大范围运动柔性梁的非接触动态测试技术.在基于位移的柔性多体系统几何精确建模及非线性有限元分析技术的基础上,利用EAGLE-500运动分析系统及其相应的分析软件对作大范围运动钛合金柔性梁作了实验研究,并且利用之前提出的几何精确梁理论进行数值仿真.数值仿真结果与实验结果完全吻合,验证了作者所提的几何精确梁理论及...     

STUDY ON THE PARAMETER VALUE DOMAIN OF MACRO-MICRO CONSTITUTIVE MODEL

宏微观耦合本构模型的参数识别往往通过反分析方法进行,为了使参数识别结果具有高的置信度,需要确定合适的参数取值范围. 基于动态再结晶过程的微观机理以及相应本构方程的数学特征,提出一个确定参数取值范围的方法. 首先详细给出考虑动态再结晶的黏塑性本构模型,并根据模型构造物理机理,提出通过6 步确定该模型参数取值范围的方法;其次,对300M 低合金钢进行不同温度、应变速率下的热变形试验,测试宏观的流动应力-应变数据及微观的组织数据;然后应用提出的方法,依据试验数据,确定参数取值范围;最后,基于确定参数取值范围中获得的知识,对模型进行局部修改,使模型模拟结果更接近实验结果.     

岩石钻孔爆破粉碎区计算模型的改进

为了研究炮孔周围岩石的破坏机理,准确预测粉碎区的范围,提出了一种计算钻孔爆破粉碎区范围的改进模型。该四分区模型考虑了破裂区内侧的环向压应力和炮孔空腔膨胀的影响,假定粉碎区为丧失了内聚力但仍具有内摩擦力的散体介质。采用弹塑性力学理论推导了柱状装药起爆条件下的岩石钻孔爆破粉碎区半径公式。计算结果表明,岩石钻孔爆破粉碎区范围通常为1.2~5.0倍炮孔半径,不同种类岩石的粉碎区范围差别很大。与其他计算模型相比,本模型的计算结果与实验数据更吻合。     

基于波形预测小波包分析模型的降振微差时间选择

从计算机模拟的角度,利用波形预测的小波包分析模型进行了段微差时间间隔的优化选择研究。算例表明:不同的微差段数,有合适的微差时间间隔范围,在该范围选择不同的微差时间间隔,具有不同的结果;随着微差段数的增加,段微差时间间隔的选择范围变窄,且选择范围出现更细的划分。这说明在实施微差爆破过程中,段微差时间间隔应当选择更高的精度,才能满足相应的干扰降振要求。     

Elastoplastic stress analysis for cylindrical shell with flat strip imperfection

Based on unequidistant B-spline function, generalized spline subdomain displacement mode of rotational shell is obtained by taking double-direction interpolation of spline. The elastoplastic constitutive equation of shells is established by using the endochronic theory.According to the initial deflection theory of shells, the elastoplastic stress analysis of cylindrical shells with flat strip geometrical imperfection is studied. Numerical results show that the geometrical imperfection has a great effect on the stress distribution of shells.     

轴对称载荷下正交异性圆环壳的一般解

本文导出了在Kirchhoff假设下受轴对称载荷时、材料正交异性的圆环壳的复变量方程,给出了该方程的一般解,该解可用于α=a/R<1,其中a为环壳截面的半径,R为环壳的总体半径,文中并举例说明其应用,结果表明本文所提出的解是很有效的。     

Axisymmetric shells and plates on tensionless elastic foundations

This paper first describes a finite element method for the large deflection analysis of axisymmetric shells and plates on a nonlinear tensionless elastic foundation. Through the use of discrete data points, any form of nonlinear elastic foundation behaviour can be easily modelled. The analysis is then validated by comparison with existing results for circular plates and beams as the only existing results for shells on tensionless foundations are found to be in error. Following this verification, the analysis is applied to investigate the behaviour of shallow spherical shells subject to a central concentrated load on tensionless linear elastic foundations. A number of insightful conclusions regarding the behaviour of such structure-foundation systems are drawn. The numerical results for shells are believed to be the first correct results, which may be useful in benchmarking results from other sources in the future.     

Stability of compressed cylindrical shells with localized asymmetric deflections

The paper proposes a new approach to the problem of stability of imperfect shells, which is used to assess their quality. Numerical results for ribbed shells with initial deflections of two types are presented. Comparing them allows assessing the quality of shells. The approach is used to determine the minimum critical load of a smooth shell, which was experimentally examined before     

Vibrations and buckling of eccentrically loaded stiffened cylindrical shells

The influence of eccentricity of loading on the vibrations and buckling of stringer-stiffened shells is studied. An established nonlinear theory, which takes into account nonlinear prebuckling, is applied and the predictions are compared with experimental results. Two families of shells, one ‘heavily’ stiffened and the other ‘moderately’ stiffened, were tested but detailed results are presented only for the ‘heavily’ stiffened shells. In each family there are three identical shells, each with different eccentricity of loading. In all cases, different in-plane-boundary conditions are considered and correlated with experimental results.     

An approximation to red blood cells with a model of three-center-combined shells

Red blood cells present a biconcave shape and bear an inner pressure (osmotic pressure) when they are in the static state. In this paper, a model of “three-center-combined shells”, which consists of two spherical shells and a toroidal shell, is employed to describe the geometric shape of red blood cells. Surface area and volume of the combined shells model are very close to those measured from experiment. The stress distribution in the cell membrane is formulized as a closed form according to the Novozhilov's theory of the three-center-combined shells. Calculating results in terms of Novozhilov's formula give a good agreement with the numerical results given by ABAQUS when using actual measurements. It is concluded that the combined shells model can well approximate to the biconcave structure of red blood cells. In addition, stress calculation shows that the membrane of biconcave red blood cells can carry bending moments, and the moments reach a maximum value in the vicinity of joint line of the spherical shell and the toroidal shell in the combined shells model.     

Timoshenko-Type Theory in the Stability Analysis of Corrugated Cylindrical Shells

A technique is proposed for stability analysis of longitudinally corrugated shells under axial compression. The technique employs the equations of the Timoshenko-type nonlinear theory of shells. The geometrical parameters of shells are specified on discrete set of points and are approximated by segments of Fourier series. Infinite systems of homogeneous algebraic equations are derived from a variational equation written in displacements to determine the critical loads and buckling modes. Specific types of corrugated isotropic metal and fiberglass shells are considered. The calculated results are compared with those obtained within the framework of the classical theory of shells. It is shown that the Timoshenko-type theory extends significantly the possibility of exact allowance for the geometrical parameters and material properties of corrugated shells compared with Kirchhoff–Love theory.     

Stability analysis of loaded coaxial cylindrical shells with internal fluid flow

We present numerical results for dynamical stability of loaded coaxial shells of revolution interacting with the internal fluid flow. The motion of the incompressible fluid is described in the framework of the theory of frictionless potential flow, whereas the static load acting on the shells is caused by the steady forces of viscous drag arising in the viscous turbulent flow in a closed channel. For shells with different boundary conditions, we study how the stability boundary is affected by the value of the gap between the shells for different versions of the outer shell rigidity and fluid flow. We show that, as in the case of unloaded coaxial shells, there is a significant deviation from the previous numerical and analytical results.     

Experimental studies of the vibrations and dynamic stability of laminated composite shells

The paper discusses the results of systematic experimental studies of vibrations and dynamic instability of thin shells of revolution made of laminated composite materials (glassfiber-reinforced plastics). The basic patterns in the dynamic deformation of shells during natural, forced, and parametric vibrations are considered. The damping parameters of natural vibrations are analyzed. The wave deformation modes of shells subject to periodic excitation are studied. The effect of long-term vibratory loading (torsion) on the dynamic characteristics of three-layer glassfiber-reinforced plastic shells is examined     

Effect of thickness inhomogeneities in internally pressurized elastic-plastic spherical shells

The behaviour of elastic-plastic spherical shells under internal pressure is investigated numerically for thickness-to-radius ratios ranging from cases of thin shells to very thick shells. The shells under consideration are made of strain-hardening elastic-plastic material with a smooth yield-surface. Attention is restricted to axisymmetric deformations, and results are presented for initial thickness inhomogeneities in various axisymmetric shapes. For smooth thickness-variations in the shape of the critical bifurcation mode, the reduction in maximum pressure is studied together with the distribution of deformations in the final collapse mode. Also, the possibility of flow localization due to more localized, initially thin regions on a spherical shell is investigated.