A CONSTITUTIVE MODEL FOR ELASTIC-PLASTIC DEFORMATION UNDER CYCLIC MULTIAXIAL STRAINING

Abstract— The yield criterion is interpreted as defining the metric of the stress space. Hydrostatic stresses correspond to null geodesies. The plastic strain increment represents a normal projection of the increment undergone by a certain scalar function (hardening function) which depends only on the distance between stress points. This establishes a flow rule formally equivalent to the Prandtl-Reuss equations. Consideration of un-loading processes leads to the analysis of equivalent paths and to the definition of a generalized length or separation which provides a new representation of kinematic hardening.     

Prediction of High-Temperature Long-Term Strength for Damaged Structures

A method is proposed for analytical estimation of the high-temperature long-term strength of structures with material discontinuities, which are stress raisers. We consider the processes involving the formation of diffusion pores. Diffusion processes in metals are strongly enhanced with increasing temperature and stresses.     

柔性冗余度机器人残余振动主动控制

研究柔性冗余度机器人的残余振动主动控制问题，设计了具有压电作动器与应变传感器的机敏杆件，建立了受控系统的状态空间表达式，采用独立模态空间控制理论设计LQR状态反馈控制器，并基于对偶原理设计了具有指定收敛特性的Luenberger全维状态观测器，最后，以平面3R柔性冗余度机器人为例进行了计算机仿真，结果表明，采用这种主动控制方法可以显著改善柔性冗余度机器人的动力学品质。     

An eight‐node hybrid‐stress solid‐shell element for geometric non‐linear analysis of elastic shells

This paper presents eight‐node solid‐shell elements for geometric non‐linear analysis of elastic shells. To subdue shear, trapezoidal and thickness locking, the assumed natural strain method and an ad hoc modified generalized laminate stiffness matrix are employed. A selectively reduced integrated element is formulated with its membrane and bending shear strain components taken to be constant and equal to the ones evaluated at the element centroid. With the generalized stresses arising from the modified generalized laminate stiffness matrix assumed to be independent from the ones obtained from the displacement, an extended Hellinger–Reissner functional can be derived. By choosing the assumed generalized stresses similar to the assumed stresses of a previous solid element, a hybrid‐stress solid‐shell element is formulated. Commonly employed geometric non‐linear homogeneous and laminated shell problems are attempted and our results are close to those of other state‐of‐the‐art elements. Moreover, the hybrid‐stress element converges more readily than the selectively reduced integrated element in all benchmark problems. Copyright © 2002 John Wiley & Sons, Ltd.     

正交异性材料在R.Hill屈服准则下平面应力问题的特征场(h>2)

大多数金属材料在承载时产生了各向异性强化的特点,因此,对这一类材料特性的深入研究显得十分必要,正确建立及分析理论模型将对在实际工程中的应用提供很好的理论依据。本文在R.Hill屈服准则下提出了无量纲化的解析应力解,讨论了屈服参数2>h时,正交异性材料平面应力问题的应力场及应力特征场,利用应力微分平衡方程得到了决定特征曲线特征的参数。结果说明特征线一般互不正交。特别地分析了平头冲压边界附近的情况,得到了各应力状态不同区域的应力特征场,应用数值分析的方法对过渡区进行了计算。     

实行全面质量管理 做好江口水电站工程设计

江口水电站是芙蓉江干流开发中的骨干工程。为认真履行江口工程的设计合同，确保优质、高效地完成江口工程的各项设计工作，长江委设计院实行全面质量管理，建立了一套规范化的统计管理程序，制订详细的设计计划，落实江口工程项目各级责任人的质量责任制，采取特殊技术措施，对工程设计过程中的各项质量活动进行全过程的管理，使江口工程在满足质量标准、合同进度的情况下，工程投资最省。     

河口水流、波浪、潮流、泥沙、河床变形二维数学模型

根据河口“波浪掀沙，潮流输沙”的泥沙运动机制，引入“波浪幅射应力”反应波浪对水体和泥沙的驱动力．考虑波浪对底部泥沙作用力、波浪对水流挟沙能力的影响及风场对水流和泥沙运动的影响．同时考虑泥沙粒径大小、水体含盐度、含沙量及水流紊动程度等因素对絮凝沉速的影响．用ＡＤＩ算法求解沿水深平均方程，破开算子法解悬移质不平衡输沙方程及河床变形方程，引入通度概念处理岸滩不规则边界，建立河口水流、波浪、潮流、泥沙、河床变形二维数学模型．通过实测资料及卫星摇感图像对所建数学模型进行检验，表明它可以较好地预测河口泥沙的运动     

压电超声微电机混合结构定子的固有频率特性分析

压电超声微电机是依靠定子振动变换能的功率器件，定子性能将直接关系到微电机能否实现，本文采用Ｒａｙｌｅｉｇｈ－Ｒｉｔｚ方法来分析机械中经常采用的多层膜结构（混合结构）定子的固有振动特性，推导中考虑了平面应力和弯曲应力对固有频率的影响，模拟计算和实验结果符合得较好，此外还讨论了定子有关参数对固有频率的影响。     

Measurements of Stress Intensity Factors of an Interface Crack Under Mixed Mode Loading

The optical method of caustics has been utilised to measure both the stress intensity factor for a crack lying along the interface of an aluminium/epoxy bimaterial specimen, and the mode mixity arising from the difference in the elastic properties across the interface. Measurements were carried out by using a novel modification to the method whereby caustics are produced and measured from both sides of the specimen, so compensating automatically for the distortion induced in the specimen due to misaligned loading fixtures. A flat reflective surface across the interface was obtained by adhering a reflective coating to the specimen. Verification that this coating does not affect measurement accuracy was obtained by comparing stress intensity factors measured from coated and uncoated monolithic aluminium specimens where good agreement was found to exist between both measurements.     

线加权余量法及其在正交异性板弯曲分析中的应用

利用有限差分法对控制方程和边界条件进行半离散化,使其定义在一些离散线上,然后采用加权余量法求解。这就是本文提出的线加权余量法,也可称之为有限差分-加权余量分维耦合法。文中以正交各向异性薄板弯曲平衡问题为例推导了有关具体算式,给出了数值算例,说明了本文方法的有效性。