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利用模拟装置实现了卡瓦与套管在地面上的实验，使用电测的方法测量胀卡时套管外表面的应变．由实验数据获得计算网格节点处的应变，同时利用单位咬合力作用套管的有限元结果进行数值法计算，获得卡瓦各咬合齿对套管咬合力的分布，为卡瓦的优化设计提供了可靠数据．     

钢筋混凝土斜交刚构连续梁桥的实验与数值分析

本文利用三维光弹性法和ANSYS软件分析了铁路斜交刚构连续梁桥在一期、二期自重载荷和两种不同工作载荷下的梁体应力分布，数值研究中分别针对实验模型和建筑实物建立计算模型，并将计算结果与实验结果进行了比较，结果表明，桥梁的应力分布呈明显的不对称特征，有其自身的独到之处。     

拱脚结构的模型实验与有限元分析

本文应用环氧树脂材料浇铸成某大跨度桥梁预应力拱脚模型,采用精密铸造成型方法做出模型中的四条索道孔。用自行研制的传感器施加四条模拟钢索的索力,通过专门设计的加载装置,使用精确的滑轮导向,在5个截面上分别施加剪力Q、弯矩M和轴力N,并考虑自重载荷,进行了电测模型实验。应用ANSYS软件对拱脚实际结构进行了有限元分析,根据模型实验时索与索道孔壁的接触情况建立了力的边界条件,使有限元计算与真实情况接近,计算误差大为减小。同时将实验与有限元分析结果进行了比较,变化规律一致,数值较为接近。对拱脚的优化设计提供了重要的参考依据。     

稳态斜轧延伸过程的刚塑性伽辽金法模拟

将无网格伽辽金法(Element-Free Galerkin Method,EFGM)与三维刚塑性流动理论相结合,对斜轧延伸过程进行了数值模拟。详细推导了斜轧延伸过程EFGM数值模型的刚度方程,给出了初始速度场和速度边界条件的建立方法和刚性区域的处理技术。得到的轧件的物理形态和金属流动的速度场均与实际情况相符,证明了采用EFGM计算斜轧延伸过程的可行性与正确性,将无网格算法引入到了斜轧领域。并将轧制力和壁厚的计算结果与实验结果进行了比较,结果发现：实验得到的轧制力结果偏小而壁厚值却偏大,其主要原因是由于在建模时做了简化和假定,同时也受轧机弹跳的影响。     

整体式卡瓦断裂仿真及实验研究

整体式卡瓦在桥塞坐封后起到支撑桥塞、锁定胶筒的作用。针对其在断裂过程中不均匀断裂而导致的承压过程中破坏失效的问题,建立了真实工况下卡瓦断裂坐封的有限元模型。基于损伤演化理论中的位移破坏原理和延性损伤准则中的材料塑性变形叠加原理,首先通过单轴拉伸实验获得了卡瓦材料的真实应力、应变等力学参数;并将其引入金属延性损伤和塑性力学参数设置中,成功模拟了卡瓦的断裂过程。基于这种分析方法和卡瓦的断裂缺陷,对卡瓦的断裂形式改进后再次分析,整体式卡瓦可均匀裂为三瓣,卡瓦本体应力分布明显降低。最后实验验证此结构下,桥塞的封堵效果良好,可稳定承载4.5in套管截面受到的50MPa轴向载荷,达到了实际坐封要求。整体式卡瓦分瓣断裂比C字形断裂承压能力更高。研究成果对应用有限元法模拟桥塞坐封过程和整体式卡瓦结构设计具有参考价值。     

考虑温粘热效应的多瓦轴承模型及其应用

构筑了轴向解析、周向有限元压力分布的一维变粘度场有限宽轴承模型。在绝热边界条件下,忽略泊肃叶流项对速度的影响,不考虑温度轴向变化并沿油膜厚度方向积分,三维能量方程可降阶为平均温度场只沿周向分布的一维形式,结合滑动轴承非线性油膜力的一维直接解法,能量方程与雷诺方程可分别求解,既考虑了温粘效应对滑动轴承非线性动力学性能的影响,又提供了无需迭代直接确定油膜破裂边界和求解非线性油膜力的快速新方法。作为应用,针对进油槽位于水平两侧的椭圆瓦轴承进行了动力润滑热效应分析,与工程数据比较,计算结果吻合,证明该模型合理,适用于工程上多瓦轴承的分析计算。     

深井/超深井开窗钻头切削齿切削力学分析

针对深井/超深井套管开窗侧钻的特殊性问题中所研究设计的双作用强侧切开窗钻头的结构特点,基于金属切削理论、开窗钻头与布齿规律,建立了开窗钻头切削齿切削力学模型,推导出开窗钻头的几何学方程,完成了切削齿切削力学模型的求解;最后使用本文研制的双作用强侧切开窗钻头进行套管开窗实验,对切削齿切削力学计算模型、仿真结果进行验证。结果表明:在开窗钻头切入套管的初始阶段,仿真计算得到的主切削力比实验所得数据略大,在中间阶段略小,到后期又略大;仿真计算结果能够准确地反映主切削力的变化规律,基本能满足工程应用的要求。本文研究结果为开窗钻头切削力的分析计算提供了理论依据,为深井/超深井套管开窗钻头的设计及切削力学研究提供参考。     

用光力学和有限元法确定钢壳的动态响应

本文提出了壳体在冲击载荷作用下三维位移分布的光力学方法的实验解和有限元数值解。采用一种新型的电磁脉冲加载装置,实现了对试件施加重复性很好的冲击载荷,利用测得的力一时间关系曲线作为外力边界条件,用逐步积分法对壳体在冲击载荷下的动态响应作了分析。光力学方法的实验解和有限元数值解吻合较好。     

完整齿轮副的三维有限元应力分析

本文分析的三维有限元模型是一完整的齿轮副,不必假设切开表面上的力与位移边界条件,也不必在进行齿轮的应力分析前预估齿牙上作用的载荷。为了减少数据准备及计算工作量,用接触线代替了啮合齿间的接触面,把非线性接触问题简化为线性接触问题。利用这里所介绍的办法,可以得到齿向载荷分布结果、齿间载荷分配结果、以及完整齿轮副任一区域内的位移及应力结果。     

用全息光弹性法解三维应力分析问题

本文介绍了进行三维应力分析的全息光弹性方法及有关技术,分析了全息光弹性方法的主要困难在于冻结材料的应力光学常数比B/A接近-0.5,并提供了一种新的光弹性材料制作和冻结工艺。这种材料冻结时的应力光学常数比可以远离-0.5。用这种材料制成的三维模型,可以通过全息光弹性方法获得三维应力的全应力实验解答。用这种方法测定了对径受压圆球和高压压头对称断面上的应力分布。实验结果和理论解进行了比较。     

A nonlinear creep model based on the concept of slip

Relations between the creep strain and the stress are obtained for a complex stress state on basis of the hypothesis that the tangent strain components depend, in a certain slip system, only on the history of variation of the corresponding shear stress component. It is assumed that the slip system orientation is chaotically distributed over all directions and the total strain of the polycrystal is considered as the sum of contributions of all slips. This permits describing the creep strains in an arbitrary stress state by using a common operator defining the dislocation slip in a certain slip system. The model can be used for arbitrary creep operators. Computational results are analyzed and compared with experimental data obtained by other authors.     

Polarized speckle-photoelasticity for 3-D stress analysis

Combining speckle interferometry with photoelasticity, the absolute retardation fringes in 3-D model are obtained by interference of the polarized rays reflected from the two surfaces of a sandwiched plate inside the model. This method can avoid the troubles introduced by Poisson's ratio μ=0.5 and stress-optical constants' ratioA/B=-2 of the photoelastic material, in a stress-frozen state and yield the results which provide necessary supplementary information for the completely-experimental solution of 3-D stress state. A comparison of experimental results with theoretical ones shows the feasibility of the method proposed in the present paper. The project is supported by the National Natural Science Foundation of China.     

EFFECT OF WALL SLIP ON SQUEEZE FLOW OF RIGID-PLASTIC MEDIA BETWEEN PARALLEL DISK

The squeeze flow of a rigid-plastic medium between parallel disks is considered for small gaps with partial wall slip. The stress distribution and the squeeze force between parallel disks of a rigid-plastic medium with the following four different slip boundary conditions are obtained. (1) The Coulombic friction condition is applied, and the stress distribution on the wall is derived, which is linear or exponential distribution in the no-slip area or slip area. (2) It is assumed that the slip velocity at the disks increases linearly with the radius up to the rim slip velocity, with the stress distribution and the squeeze force gained. (3) The assumption that the slip velocity at the disks is related to the shear stress component is used, with the stress distribution and the squeeze force obtained, which is equivalent to the result given in (2). (4) Rational velocity components are introduced, and the stress distribution is satisfied.     

软弱地基上拱形围堰的光弹性研究

介绍目前水利水电工程设计中常遇到的软弱地基上拱形围堰的光弹性试验研究.其中包括异弹模组合模型浇制与粘结、水砂压荷载模拟及主要试验成果. 文中分析了在上述荷载作用下拱堰的受力特点和工作状态,探讨了低弹模基础和边界条件不对称性对堰体内力的作用和影响,提出了进一步改善应力和稳定条件的途径和措施.     

Linear and Nonlinear Algorithms for Stress Separation in Photoelasticity

An experimental-numerical hybrid method for the stress separation in photoelasticity is proposed in this study. In the proposed method, boundary conditions for a local finite element model, that is, tractions along boundaries are inversely determined from photoelastic fringes. Two algorithms are proposed for determining the boundary condition. One is a linear algorithm in which the tractions are obtained by the method of linear least-squares from both principal stress difference and principal direction. Another is the nonlinear algorithm in which the tractions are determined only from the principal stress difference. After determining the boundary conditions for the local finite element model, the stresses can be obtained by finite element direct analysis. The effectiveness is demonstrated by applying the proposed method to a perforated plate under tension and contact problems. Results show that the boundary conditions of the local finite element model can be determined from the photoelastic fringes and then the individual stresses can be obtained by the proposed method. Furthermore, the stresses can be evaluated even if the boundary condition is complicated such as at the contact surface. It is expected that the proposed method can be powerful tool for stress analysis.     

复合弹模光弹模型中粘结约束应力的消除方法

本文对变弹性模量三维光弹地质体模型中的粘结约束应力进行了分析和讨论。同时,提出了两种消除变弹模光弹模型中粘结约束应力的方法。本文对变弹性模量三维光弹性实验的应用和发展具有一定的参考价值。     

三维光弹性中预应力结构的应力冻结研究

本文提出用三维光弹性应力冻结法模拟分析预应力钢筋混凝土结构中的应力。通过模拟体与实体结构的相似性研究,给出了模型载荷比例系数Cq参数,通过参数合理的选取,有效的解决了应力冻结水平预测这一技术关键;用光弹性应力二次冻结法,将结构预应力和负载应力冻结在同一试件中;应分析精度对模型尺寸的要求,采用了精密浇铸的方法制作模型。此外,还研制了受力清晰明确的加载系统。对这些涉及应力冻结的若干关键问题结合工程实例进行探讨。实验应力分析结果与有限元数值法一致性较好。     

On the uniqueness of a rate-independent plasticity model for single crystals

This paper presents the uniqueness and existence conditions for a rate-independent plasticity model for single crystals under a general stress state. The model is based on multiple slips on three-dimensional slip systems. The uniqueness condition for the plastic slips in a single crystal with nonlinear hardening is derived using the implicit function theorem. The uniqueness condition is the non-singularity of a matrix defined by the Schmid tensors, the elasticity, and the hardening rates of the slip systems. When this matrix becomes singular, the limitations on the loading paths that can be accommodated by the active slip systems (i.e., the existence conditions) are also given explicitly. For the compatible loading paths, a particular solution is selected by requiring the solution vector to be orthogonal to the null space of the singular coefficient matrix. The paper also presents a fully implicit algorithm for the plasticity model. Numerical examples of an fcc copper single crystal under cyclic loadings (pure shear and uniaxial strain) are presented to demonstrate the main features of the algorithm.     

An extension of generalized plane stress for problems with out-of-plane restraint

The standard concept of generalized plane stress is extended to obtain a new mathematical model for studying the effect of local out-of-plane displacement restraint on the in-plane stresses and displacements in thin plates. It is pointed out how this model may be used by the photoelastician, whose otherwise plane-stress experiment introduces an unavoidable out-of-plane restraint condition in the model, to obtain some estimate of the deviation to be expected between the results of his experiment and the actual plane-stress solution of the problem. In this way, the model may be applied to aid in the interpretation of a large class of two-dimensional photoelastic analyses involving the determination of stresses near rigid inclusions and rigid boundaries. The extended model is then applied to the problem of an annular disk subjected to thermal shrinkage and completely restrained at its outer boundary. In view of the simplicity of the model, the predicted radial and circumferential stress distributions agree remarkably well with existing photoelastic data. In contrast, results obtained from standard generalized plane-stress theory, which cannot account for the out-of-plane displacement restraint at the outer boundary, show substantial deviation from experimental values, especially near the restrained boundary.