Weld Models Incorporating the HAZ Phase Transformation Effects, Comparison between Experimental and Numerical Results

lIntroductionEleCtricit6deFrance,Framatomeandbureaudecontr6ledeschaudi6resnucl6aires,hadledaresearchprogramonweldingfinitO-elemotsimulatonforthedsterminatonofnuclearcomPonensresidualstressesandinparticuarforsomesteelwithmetallurgicaltransformations.OneofthemainstagesofthswOrkistovalidatethemechancalmodelsimPlatedinfinite-elemotcodeswithinwhichthemetallurgicaltransformationseffectsareincorporated.ThisisthepurposeofthePresentpaper.ThetWocodesusedhereareSysweld(Framatome)andCOdeAster(EDF).…     

舰船主船体水线以下部分武器

采用符拉索夫计算法计算武器命中后的舰船浮态和外载荷的变化。以薄壁梁理论为基础,用迁移矩阵法计算武器命中后的舰船的内力,并以某舰船为计算模型进行了数值计算分析,找出正应力和剪应力随不同破口部位及尺寸的变化规律,从而为舰船破损后的剩余强度研究提供了依据。     

钢桥桥面铺装层间剪应力影响因素及简化计算

为了减小钢桥桥面铺装层间剪应力,建立桥面系三维有限元计算模型,分析了不同荷位、钢板厚度、U肋开口宽度、铺装厚度、铺装模量、层间接触条件以及轴载大小对铺装层间纵横向剪应力的影响,推导了实用的应力简化计算公式。研究发现桥面板不均匀变形使得铺装层间剪应力远大于同条件下的路面结构;影响显著的因素依次为轴载大小、钢板厚度、U肋开口宽度以及铺装参数;层间完全光滑有利于抗剪,但降低了桥面系整体刚度;控制重载,加强桥面系刚度与选择柔性层间粘结材料是减小层间剪应力的有效措施。     

T型接头焊接残余应力的有限元模拟

本文基于通用商业有限元ANSYS对T型接头焊接残余应力场进行模拟分析,克服了实验测量方法等缺点,对科学研究和工程实际都具有重要意义。     

A finite element model for unbonded flexible pipe under combined axisymmetric and bending loads

Flexible pipes are key equipment for offshore oil and gas production systems, conveying fluids between the platform and subsea wells. The structural arrangement of unbonded flexible pipes is quite complex, encompassing several layers with polymeric, metallic and textile materials. Different topologies and a large amount of intricate nonlinear contact interactions between and within their components, especially because of the relative stick-slip mechanism during bending, makes numerical analysis challenging. This paper presents an alternative three-dimensional nonlinear finite element model that describes the response of flexible pipes subjected to combined axisymmetric and bending loads. To simulate the response of a flexible pipe under axial tension or compression combined with uniform curvature, an equivalent thermal loading is employed on the external sheath, which is modelled as an orthotropic thermal expansion material with temperature-independent mechanical properties. To assess the feasibility of the proposed model, the bending moment versus curvature of the finite element solution is compared with experimental results obtained in literature and good agreements are found between them. Detailed finite element results such as contact pressures, armour wire slip displacements and friction, normal and transverse bending stresses are also shown and compared with available analytical models.     

碳纤维加固病害RC梁的力学性能研究

文章运用ANSYS软件,建立“实体一弹簧．壳”的有限元模型,对碳纤维板加固带有初始裂纹的纯弯曲病害钢筋混凝土梁（RC梁）的力学性能进行研究。结果表明：经碳纤维板加固后,病害RC梁的极限承载力、钢筋屈服荷载、开裂后的整体刚度均有明显提高,且碳纤维板越厚,加固效果越显著。此外还能有效抑制裂纹扩展、改善梁底受力状况,减小裂纹尖端应力强度因子,提高构件剩余疲劳寿命。     

Prediction of residual stresses induced by low transformation temperature weld wires and its validation using the contour method

Welding residual stresses are one of the main factors influencing the engineering properties of welded structures, and should be taken into account during designing and manufacturing products such as ships, bridges, etc. Recently, both computational and experimental methods play a significant role for providing residual stresses. The contour method (CM) became one of the most powerful techniques that can provide measurement of residual stresses normal to a plane of interest. In this method a component is cut at any plane of interest. Displacements normal to the cut surface are measured and then processed. Using the Thermal–Elastic–Plastic Finite Element Method (TEP-FEM), residual stresses after welding can be predicted. As well as, the elastic FEM can be used to reproduce residual stresses from measured longitudinal displacements in the CM.The main objective of this paper is to evaluate the effectiveness of different low transformation temperature (LTT) weld wires using TEP-FEM and the CM. In the simulation part, a computational approach is developed to numerically simulate both of welding and the CM. In the TEP-FEM, phase transformation is considered for LTT welds, additionally volume change and variation of mechanical properties with temperature are considered. In the simulated CM, welded specimens to be measured are replaced by TEP-FE models. Then the procedure of the CM is examined before applying it to real measurements. The simulated CM successfully predicted how the CM would reconstruct the residual stresses if applied experimentally. In the experimental part, welding is conducted using conventional and various LTT weld wires. Longitudinal residual stresses produced due to welding are measured using the CM. The results of TEP-FE simulation and the CM show the effectiveness of the different LTT weld wires in introducing compressive stresses in the weld. It is also observed that the applied LTT weld wires, which have almost the same martensitic transformation start temperatures, do not show big difference in the induced compressive residual stresses in the weld metal.     

板架弯曲二次应力对纵骨疲劳评估影响的研究

为了验证散货船、油船协调共同规范(HCSR)中在计算纵骨疲劳寿命时不考虑板架弯曲纵骨二次应力的合理性,讨论两种二次应力的计算方法,分别对散货船和油船板架的纵骨的二次应力进行计算,通过对是否考虑纵骨二次应力计算得到的疲劳寿命进行对比,验证HCSR中简化算法计算纵骨疲劳寿命的合理性。     

雷达跟踪目标的残差检测自适应多模型算法

提出了一种基于残差的自适应多模型算法，通过残差的大小来分配多模型中单个模型在整体估计中的权重。本算法无须机动检测，从理论上避免了延迟。通过Monte Carlo仿真表明本算法的有效性。     

Quasi-dynamic traffic assignment with residual point queues incorporating a first order node model

Static traffic assignment models are still widely applied for strategic transport planning purposes in spite of the fact that such models produce implausible traffic flows that exceed link capacities and predict incorrect congestion locations. There have been numerous attempts to constrain link flows to capacity. Capacity constrained models with residual queues are often referred to as quasi-dynamic traffic assignment models. After reviewing the literature, we come to the conclusion that an important piece of the puzzle has been missing so far, namely the inclusion of a first order node model. In this paper we propose a novel path-based static traffic assignment model for finding a stochastic user equilibrium in general transportation networks. This model includes a first order (steady-state) node model that yields more realistic turn capacities, which are then used to determine consistent capacity constrained traffic flows, residual point (vertical) queues (upstream bottleneck links), and path travel times consistent with queuing theory. The route choice part of the model is specified as a variational inequality problem, while the network loading part is formulated as a fixed point problem. Both problems are solved using existing techniques to find a solution. We illustrate the model using hypothetical examples, and also demonstrate feasibility on large-scale networks.