薄壁球壳焊缝的应力与应变

依据球壳轴对称弯曲理论,导出了球壳赤道圆上对接焊缝残余应力和变形的定量解答。讨论了几何尺寸 (R、t)及焊接因素(σ0,b)对残余应力与变形的影响。     

立式圆筒形钢制储罐焊接变形在焊接上的控制

根据立式钢制储罐在焊接过程中产生焊接变形的现象,分析了焊接变形的原因,提出了控制焊接中罐板变形的措施,以有效保证工程施工中的焊接质量和罐体制作质量。     

Finite element analysis for geometrically nonlinear deformations of smart functionally graded plates using vertically reinforced 1-3 piezoelectric composite

In this paper, a finite element model has been developed for the geometrically nonlinear static analysis of simply supported functionally graded (FG) plates integrated with a patch of vertically reinforced 1-3 piezoelectric composite material acting as a distributed actuator. The material properties of the functionally graded substrate plate are assumed to be graded only in the thickness direction according to the power-law distribution in terms of the volume fractions of the constituents. The analysis of the electro-elastic coupled problem includes the transverse deformations of the overall plate to utilize the transverse normal actuation by the distributed actuator for counteracting the nonlinear deformations of smart functionally graded plates. The nonlinear governing equations of equilibrium are solved by using direct iteration method with under-relaxation. The numerical illustrations suggest the potential use of the distributed actuator made of vertically reinforced 1-3 piezoelectric composite material for active control of nonlinear deformations of smart functionally graded plates. The effect of variation of piezoelectric fiber orientation in the distributed actuator on its control authority for counteracting the nonlinear deformations of smart functionally graded plates has also been investigated.     

Refined analysis for cold bending steel plate girders

Cold bending is a simple, economical fabrication method for curving steel elements primarily used in building applications. In this method, appropriate loads are applied to obtain the desired curvature. The authors recently developed approximate analytical solutions for curving unstiffened, symmetrical or non-symmetrical girders. These solutions relating loads to residual deformation were used to establish limits on geometry, maximum load and curvature so that Bauschinger effects did not have to be considered. This paper refines and extends the earlier solution by incorporating previously neglected factors relating to loading, support condition and girder geometry that resulted in under-estimation of the stiffness of the system. Revised equations are presented and their application described by an illustrative example.     

钛合金加工特性分析及刀具选择

钛合金因其性能的优越性,在航空、航天、石油、化工、汽车和核武器事业等生产领域得到了广泛的应用,但在数控加工钛合金过程中,存在切削效率低下、刀具耐磨性差、切削排屑困难等加工难题.本文通过多次加工试验和研究,总结出了一套加工钛合金的方法,取得了较为理想的切削效果.     

A modified numerical VBI element for vehicles with constant velocity including road irregularities

There has been a growing interest to model and analyze Vehicle-Bridge Interaction (VBI) of intricate vehicles on bridges. The objective of such an analysis is to realistically investigate the dynamic effects of moving vehicles particularly in case of high-speed trains, where the vehicle acceleration is a design criterion and should be calculated appropriately. One method of analysis is to eliminate the wheel degrees of freedom (DOF) that are in direct contact with the bridge surface resulting in a VBI element, which is a modified beam element acted upon directly by wheel(s) of a running vehicle. The contact force is the mutual force between the wheel and the bridge. The available formulation in the literature is used to formulate the contact forces, which are related to those in the beam element DOFs by the Hermitian interpolation functions. Considering suitable interpolation functions between the beam element displacement vector and those for contact points and also a new formulation for the contact points, a new formulation is proposed for the structural properties of the VBI element, resulting in a new element capable of capturing bridge and vehicle responses more realistically. A study is conducted on the model variables and their effects on the bridge dynamic amplification factor and also bridge and vehicle accelerations, in order to compare the new VBI method with the existing one. The studied parameters include vehicle and bridge damping, frequency parameter, system mass parameter, and a new parameter called vehicle mass parameter. Results generally demonstrate noticeable differences particularly for high speed vehicles. In addition, it is observed that the effect of shear deformations in a simply-supported bridge might not be negligible and should be considered for moving vehicle analysis. For double girder open-deck steel railway bridges, the difference in midspan deflection of models including or excluding shear deformation can vary from 18% to 8% for 4.0 m and 30.0 m spans, respectively, for a sample vehicle.     

组合楼板的全过程挠度分析

对组合楼板的挠度进行研究,其值直接取决于异性钢板与混凝土间连接的剪切刚度。基于架构理论,直接考虑连接的剪切刚度,提出计算组合楼板挠度的方法,考虑混凝土层在普通裂缝和受压下塑性变形对结构刚度的影响。采用本方法,可获得这些影响因素从初始阶段至极限状态全范围的变化情况。对异形钢板与混凝土的连接试件进行试验,结果表明:其连接性能分3个阶段。每个阶段都有不同的剪切特性,用于计算楼板挠度。从加载初期至极限状态,分析Holorib异形板组合楼板变形试验值的变化。采用本方法计算的楼板变形值与试验值吻合较好。     

Finite deformation frictional mortar contact using a semi‐smooth Newton method with consistent linearization

A two‐dimensional, finite deformation frictional contact formulation with Coulomb's law is presented. The approach considers multibody contact and is based on a mortar formulation. The enforcement of contact constraints is realized with dual Lagrange multipliers. These alternative multiplier spaces are constructed in a way that the multipliers can easily be eliminated from the global system of equations by static condensation such that the system size does not increase. Friction kinematic variables are formulated in an objective way and enter non‐smooth complementarity functions for expressing the contact constraints. An active set strategy is derived by applying a semi‐smooth Newton method, which treats contact nonlinearities, material and geometrical nonlinearities in one single iterative scheme. By further carrying out a consistent linearization for both normal and frictional contact forces and constraints, a robust and highly efficient algorithm for linear and higher‐order (quadratic) interpolation is achieved. Efficiency of the proposed method and quality of results are demonstrated in several examples. Copyright © 2010 John Wiley & Sons, Ltd.     

A finite deformation mortar contact formulation using a primal–dual active set strategy

In recent years, nonconforming domain decomposition techniques and, in particular, the mortar method have become popular in developing new contact algorithms. Here, we present an approach for 2D frictionless multibody contact based on a mortar formulation and using a primal–dual active set strategy for contact constraint enforcement. We consider linear and higher‐order (quadratic) interpolations throughout this work. So‐called dual Lagrange multipliers are introduced for the contact pressure but can be eliminated from the global system of equations by static condensation, thus avoiding an increase in system size. For this type of contact formulation, we provide a full linearization of both contact forces and normal (non‐penetration) and tangential (frictionless sliding) contact constraints in the finite deformation frame. The necessity of such a linearization in order to obtain a consistent Newton scheme is demonstrated. By further interpreting the active set search as a semi‐smooth Newton method, contact nonlinearity and geometrical and material nonlinearity can be resolved within one single iterative scheme. This yields a robust and highly efficient algorithm for frictionless finite deformation contact problems. Numerical examples illustrate the efficiency of our method and the high quality of results. Copyright © 2009 John Wiley & Sons, Ltd.