Optimizing loading path and die linetype of large length-to-diameter ratio metal stator screw lining hydroforming

In order to meet the high temperature environment requirement of deep and superdeep well exploitation, a technology of large length-to-diameter ratio metal stator screw lining meshing with rotor is presented. Based on the elastic-plasticity theory, and under the consideration of the effect of tube size, material mechanical parameters, friction coefficient and loading paths, the external pressure plastic forming mechanical model of metal stator screw lining is established, to study the optimal loading path of metal stator lining tube hydroforming process. The results show that wall thickness reduction of the external pressure tube hydroforming(THF) is about 4%, and three evaluation criteria of metal stator screw lining forming quality are presented: fillet stick mold coefficient, thickness relative error and forming quality coefficient. The smaller the three criteria are, the better the forming quality is.Each indicator has a trend of increase with the loading rate reducing, and the adjustment laws of die arc transition zone equidistance profile curve are acquired for improving tube forming quality. Hence, the research results prove the feasibility of external pressure THF used for processing high-accuracy large length-to-diameter ratio metal stator screw lining, and provide theoretical basis for designing new kind of stator structure which has better performance and longer service life.

Modeling of the loading path dependent magnetomechanical behavior of Galfenol alloy

The magnetomechanical behavior of single-crystal Galfenol alloy was found to be strongly dependent on the loading paths. An energy-based anisotropic domain rotation model, assuming that the interaction between domains can be ignored and the probability of the magnetic moment pointing along a particular direction is related to the free energy along this direction, is used to simulate the magnetostriction versus magnetic field and stress curve and to track the magnetic domain motion trail. The main reason for loading path dependent effect is the rotation/flipping of the magnetic domains under different loading paths. The effect of loading and unloading paths on 90° magnetic domain motion was studied by choosing different loading and unloading state and paths. The results show that prior loading magnetic field can make the 90° magnetic domains flip to the directions of 45°domains because the magnetic field is the driving force to make the domains rotate, and the final loading state and the loading path both have great influence on the motion of 90° magnetic domains.

Effective Virtual Reality Based Building Navigation Using Dynamic Loading and Path Optimization

Although computer capabilities have been improved significantly, a large-scale virtual reality （VR） system demands much more in terms of memory and computation than the current computer systems can offer. This paper discusses two important issues related to VR performance and applications in building navigation. These are dynamic loading of models based on cell segmentation for the optimal VR operation, and the route optimization based on path planning for easy navigation. The VR model of engineering and information technology complex （EITC） building at the University of Manitoba is built as an example to show the feasibility of the proposed methods. The reality, enhanced by three-dimensional （3D） real-time interactivity and visualization, leads navigators into a state of the virtual building immersion.

Effect of Loading Paths on Hydroforming Tubular Square Components

The influence of loading path on tube hydroforming process is discussed in this paper with finiteelement simulation. Four different loading paths are utilized in simulating the forming process of square tubular component with hydroforming and the result of different loading path is presented. Among the result. the thickness distribution of bilinear loading path is the most uniform one. It shows that the increase of punch displacement in the stage of high pressure is beneficial to the forming of component for optimized Stress condition.

PATH INTEGRAL SOLUTION OF NONLINEAR DYNAMIC BEHAVIOR OF STRUCTURE UNDER WIND EXCITATION

A numerical scheme for the nonlinear behavior of structure under wind excitation is investigated. With the white noise filter of turbulent-wind fluctuations, the nonlinear motion equation of structures subjected to wind load was modeled as the Ito＇ s stochastic differential equation. The state vector associated with such a model is a diffusion process. A continuous linearization strategy in the time-domain was adopted. Based on the solution series of its stochastic linearization equations, the formal probabilistic density of the structure response was developed by the path integral technique. It is shown by the numerical example of a guyed mast that compared with the frequency-domain method and the time-domain nonlinear analysis, the proposed approach is highlighted by high accuracy and effectiveness. The influence of the structure non-linearity on the dynamic reliability assessment is also analyzed in the example.

MTSS: multi-path traffic scheduling mechanism based on SDN

Large-scale and diverse businesses based on the cloud computing platform bring the heavy network traffic to cloud data centers.However,the unbalanced workload of cloud data center network easily leads to the network congestion,the low resource utilization rate,the long delay,the low reliability,and the low throughput.In order to improve the utilization efficiency and the quality of services(QoS)of cloud system,especially to solve the problem of network congestion,we propose MTSS,a multi-path traffic scheduling mechanism based on software defined networking(SDN).MTSS utilizes the data flow scheduling flexibility of SDN and the multi-path feature of the fat-tree structure to improve the traffic balance of the cloud data center network.A heuristic traffic balancing algorithm is presented for MTSS,which periodically monitors the network link and dynamically adjusts the traffic on the heavy link to achieve programmable data forwarding and load balancing.The experimental results show that MTSS outperforms equal-cost multi-path protocol(ECMP),by effectively reducing the packet loss rate and delay.In addition,MTSS improves the utilization efficiency,the reliability and the throughput rate of the cloud data center network.

On the Advantages of the Theories of Plasticity with Singular Loading Surface

This paper analyzes the peculiarities of plastic flow of metals for the case of non-proportional loading when the loading path consists of two portions—uniaxial tension and subsequent infinitesimal pure shear (torsion). The issue is discussed from the point of view of the hardening rules governing the kinetics of loading surface. Three cases are considered, flow plasticity theory with isotropic and kinematic hardening rule, as well as the synthetic theory of plastic deformation. As a result, the synthetic theory leads to the results that correlate with experiments, whereas the former two theories associated with smooth loading surfaces give a principal discrepancy with experimental data.

Influence of stress path change on the resistance to plastic deformation of cold rolled sheets

Flat workpieces have been tested in order to investigate the influence of stress path change （loading mode） while keeping strain path unchanged. These investigations are pertinent to the testing of cold rolled strips and to subsequent forming. The workpieces which first compressed by plane strain compression in thickness direction were then tested in perpendicular direction in order to measure the influence of strain and stress path. The tension workpieces came from flat die compression test at different deformation histories. Two different materials were investigated： 18/8 Ti stainless steel and AW-1050 aluminium. The results show that the plastic flow by tension in lengthwise direction after pre-strain by compression in thickness direction will begin at an appreciably lower stress than that of the workpieces unloaded after pre-compression. Comparing with two materials, it can be seen that both 18/8 Ti stainless steel and AW-1050 aluminium behave similarly. The drop in yield stress is lower for AW-1050 aluminium than that for 18/8 Ti stainless steel. However, reloading in different directions than in the precious step results in significantly higher strain hardening.

HSM strategy study for hardened die and mold steels manufacturing based on the mechanical and thermal load reduction strategy

The paper discussed cutter-work engagement situation hidden behind the mechanical and thermal load effect on cutting edges during high speed hard machining process. The engagement situation was investigated in great detail using experimental and geometrical analytic measures. Experiments were conducted using A1TiN-coated micro-grain carbide end mill cutters to cut hardened die steel. On the basis, a general high speed hard machining strategy, which aimed at eliminating excessive engagement situation during high-speed machining （HSM） hard machining, was proposed. The strategy includes the procedures to identify prone-to-overload areas where excessive engagement situation occurs and then to create a reliable tool path, which has the effect of cutting load reduction to remove the prone-to-overload areas.

一种基于曲率和B样条的矿区装载车辆连续路径规划方法

矿区装载车辆的任务是从进入点到装载点进行装载,然后离开矿区。在进入装载点前,车辆要在回转点改变行进方向,以便倒车进入装载点。针对装载车辆的任务特点,本文提出了一种基于曲率和B样条的路径规划方法。首先,基于车辆运动模型设计了A*算法的成本函数,获得了与车辆转弯半径相关的离散路径。为了进一步获得装载车辆的连续路径,又提出了改进的B样条插值法,使得连续路径两端切线符合车辆起始点和终点的位姿。随后,基于模拟退火算法,获得了车辆的回转点,使得车辆可以在进入装载点前改变前进方向。仿真结果表明,所提出的连续路径规划方法能够保证生成曲率连续的装载车辆路径,并保证路径两端符合车辆在起始点和终点的位姿,为矿区装载车辆的自动驾驶技术提供了基础。

工业厂房皮带廊结构改造托梁换柱加固技术

随着城市更新的推进,针对一些大型工业建筑,不仅要满足结构受力需要,而且更需满足现代城市生活功能。针对已报废停产的工业厂房皮带廊项目,为了满足城市园区交通需求,需拔除旧厂房皮带廊项目跨中的混凝土立柱。最后采用钢托梁替代原混凝土梁的方式,改变了结构传力路径,通过ANSYS进行结构受力验算,最终提出托梁换柱的加固改造方法,现场安装临时支撑千斤顶进行结构卸载,该方法不仅满足了原设计拆除部分支撑柱的要求,同时也实现了结构原状和其历史风貌保护。

不同加卸载路径下灵敏性粉土的变形特性

山西汾河中游一级阶地的施工中发现,饱和粉土地基受扰动后会产生很大的附加沉降,且迟迟不能稳定,表现出灵敏性。基于一维固结蠕变试验研究不同的加卸载路径对灵敏性粉土变形特性的影响,结果表明:加卸载路径和加卸荷比是影响压缩曲线的重要因素;压缩曲线在出现转折时对应的应力为结构屈服应力;加荷比越大,同级荷载下沉降值、固结系数、次固结系数和主固结比都会增大,同时其压缩曲线越趋近于线性,特征转折点消失,但加荷比越大,可大大减少工期;预压荷载的大小和卸荷比都会影响灵敏性粉土的回弹量,预压荷载大于结构屈服应力时,卸荷比越大,回弹量越大,因此需要采取分级卸载方法减小回弹量,保证预压效果;目标荷载小于结构屈服应力时,超载预压法降低工后沉降效果显著。

动态上下料路径下柔性产品族生产调度研究

针对汽车零部件柔性产品族制造单元考虑工序间动态上下料路径与时间的生产调度求解问题,文中提出一种用于动态上下料路径柔性作业调度问题优化的自适应离散差分进化算法。通过自适应缩放参数实现收敛速度提升,构建基于矩阵映射的离散编码规则实现变异操作离散化及基于机器人实际运动路径的动态调度解码。通过对某平台化车型架构的转向器壳体加工单元实例分析并验证了算法有效性及优越性。

Progressive Collapse Resistance of a New Staggered Story Isolated System

A new staggered isolated system developed from the mid-story isolated system is the new staggered story isolated system. There are not many studies on this structure currently. In this study, an 18-story new staggered story isolated system model is established using SAP2000. The dynamic nonlinear dynamic alternate method is used to analyze the structure against progressive collapse. Results show that the structure has good resistance to progressive collapse, and there is no progressive collapse under each working condition. The progressive collapse does not occur for the case of removing only one vertical structural member of the new staggered of isolated system. The side column has big influence on this isolated structures’ progressive collapse;the removal of vertical structural member of the isolation layer has less impact on the structure than the removal of the bottom vertical structural member. After the removing of the member, the internal force of the structure will be redistributed, and the axial force of the adjacent columns will change obviously, showing a trend of “near large and far small”.

非线性加载路径下金属薄板成形极限研究进展

成形极限图是评判金属薄板局部成形能力的重要工具,研究非线性加载路径下的成形极限图对提高实际生产过程中工艺设计的合理性和板料的成形性具有重要意义。总结分析了国内外学者对非线性加载路径下金属薄板成形极限的研究进展,主要包括试验方法、理论预测模型及路径无关成形极限图3个方面。重点研究了不同试验方法的适用范围及优缺点,阐述了多种预测非线性加载路径下成形极限图的理论模型及应用实例,并归纳了当前在应变路径无关的成形极限图方面取得的研究成果。最后,从上述3个方面总结了当前更具潜力的研究方向,并对未来的发展趋势以及面临的困难和挑战进行了展望。

不同加载速率及应力路径对饱和红黏土的力学响应

利用ABAQUS有限元软件,建立轴对称模型,分析赣南地区的红黏土在不同加载速率及应力路径下的力学响应,并验证数值模型的可行性。结果表明:不同应力路径下红黏土的应力-应变关系曲线、孔压-应变关系曲线变化特征不同,同一应力路径下加载速率的大小不影响整体发展趋势,但决定峰值大小;红黏土对侧向卸荷的敏感性高于轴向加载,高加载速率的敏感性大于低加载速率;三种应力路径下的孔压-加载速率关系曲线,均可用对数函数关系描述。

冲击加载-卸载-再加载条件下Cr-Ni-Mo钢的层裂损伤

基于一级轻气炮加载技术,利用不同类型的多层复合飞片,实现了冲击加载-卸载-再加载路径,结合回收表征以及一维流体力学模拟,对Cr-Ni-Mo钢在冲击加载-卸载-再加载路径下的层裂损伤行为进行了深入研究。结果表明,在冲击加载-卸载-再加载路径下,层裂面会重新闭合并形成微损伤带,而孔洞位置仍然位于原奥氏体边界和板条群边界处,裂纹仍保持穿晶+沿晶的混合断裂模式。此外,第1层飞片与样品之间存在的较大阻抗差异会导致自由面速度中的再加载信号缺失。这些发现为深入理解Cr-Ni-Mo钢在复杂加载路径下的层裂行为提供了重要参考。

基于传力路径的接骨板结构拓扑优化设计

目的 提出一种相对于传统拓扑优化方法能有效降低应力集中,并进一步提高断骨愈合效果的接骨板拓扑优化设计方法。方法 依据接骨板在断骨-接骨板系统中的载荷约束条件,采用改进的基于传力路径的拓扑优化方法对接骨板结构进行优化设计。随后采用基于偏应变的骨再生模拟模型,对胫骨骨干横向骨折情况进行骨再生模拟,依据骨再生过程数据对优化接骨板的受力状态、固定稳定性及愈合性能进行评估。结果 使用基于传力路径优化方法的优化接骨板在体积分数f=0.55、0.65时,接骨板最大应力分别为55.68、42.23 MPa,相较于传统拓扑优化方法优化接骨板分别降低32.96%、29.95%;骨愈合过程后骨痂平均弹性模量分别为1 439.47、1 355.71 MPa,相较于传统接骨板分别提升145.86%、131.06%。结论 提出的改进基于传力路径的拓扑优化方法,可以用于接骨板结构优化设计,优化后接骨板相比传统拓扑优化方法优化接骨板受力更加均匀,使用安全性更高,骨愈合性能相较传统接骨板有明显提升。研究结果为骨折内固定植入物的优化设计提供了一种新思路和方法。

列车荷载作用下压实花岗岩残积土累积变形特性试验研究

为研究列车荷载作用下应力及湿化条件对压实花岗岩残积土累积变形特性的影响,以围压、动应力幅值、含水率为变量,对压实花岗岩残积土进行循环空心扭剪和循环定向加载试验。结果表明:循环扭剪应力路径下主应力轴旋转效应增加了试样的累积变形量,甚至改变了累积变形的发展模式,该影响程度随试样含水率的增大而增大;试样的累积应变发展速率在加载初期(N<100)时完成大幅度衰减,围压增大可加快累积应变发展速率的衰减,动应力幅值的增加会延长累积应变发展速率的衰减时间,循环扭剪加载时试样的累积应变发展速率衰减程度小于循环定向加载试验,含水率越高该效应越显著。通过预测模型能够对两种动力加载应力路径下的稳定型和发展型累积应变发展曲线能够进行拟合,对压实花岗岩残积土的累积变形作出较好预测。

考虑分布式电源的配电网灾中-灾后两阶段协同韧性恢复决策

频繁的极端自然灾害极易引发配电网大规模故障,基于分布式电源的负荷恢复是提高配电网韧性水平的重要手段。然而,现有研究一般将灾中和灾后阶段进行独立决策,忽略了二者决策的连续性和耦合性,延缓了恢复进程。为此,文中提出一种基于灾中-灾后两阶段协同决策的配电网快速恢复方法,充分考虑灾中-灾后过程中的相互作用,综合分布式电源调度、网络拓扑改变、维修人员调度等在内的恢复措施,保障灾中-灾后阶段连续决策的最优性。首先,考虑灾后供能路径对灾中网络拓扑的需求关系,建立灾中阶段以分布式电源为核心的拓扑调整模型与负荷元胞恢复模型,实现部分重要负荷的供电;其次,考虑灾中决策对灾后恢复的影响,建立灾后阶段故障维修人员调度和负荷快速恢复的联合决策模型,实现所有负荷的有序恢复;然后,以灾中-灾后全阶段失负荷量最小为目标,实现灾中-灾后恢复的协同决策;最后,基于IEEE 123节点配电系统验证了所提模型的有效性。