磨抛机器人气电力控末端执行器负载特性研究

针对现有船舶制造业中人工打磨或砂带磨削等磨抛作业难以满足智能制造需求的现状,提出一种面向船舶磨抛机器人的气电混合式力控末端执行器,采用自适应变参数PID控制器对非对称气缸的气动力与大推力永磁直线同步电机的电磁力进行协调控制,实现作业接触力的实时补偿与精确控制。通过对气动系统、永磁直线同步电机系统、环境工件、力和速度控制器等进行建模与数值仿真,研究其负载波动响应与抗负载冲击特性。仿真结果表明,相比气动力控系统,气电混合式力控系统可消除气动系统振荡特性的影响,在35Hz范围内振动负载作用下的最大力波动幅值由138N(约为稳态值46%)减小至25N(约为稳态值8.4%)；在阶跃负载作用下气缸活塞杆位移振荡和接触力冲击次数显著减少,调整时间分别仅为前者的32.3%和27.3%,有效提高了抗负载波动与冲击特性,可提升船舶磨抛机器人作业质量。     

Strength analysis of fillet welds under longitudinal and transverse shear conditions

In support of the development of improved fillet weld sizing criteria for lightweight shipboard structures, a comprehensive static strength test program using longitudinal and transverse shear specimens according to AWS B4.0 Standards has been conducted. This test program covers base material with strength ranging from 71 ksi (490 MPa) to 96 ksi (660 MPa) and weld size ranging from 1/8″ (3 mm) to 3/8″ (10 mm). This paper focuses on a traction stress based analysis of the test data as an effort to establish a unified shear strength definition for load-carrying fillet weld specimens regardless of shear loading conditions. The proposed shear strength definition proves to be effective in correlating the fillet weld strength test data of the longitudinal and transverse shear specimens. The results of this investigation demonstrate that existing shear strength definitions used by various weld sizing criteria such as those given by Class Societies have two major limitations: (1) it cannot be related to a critical stress state on experimentally observed failure plane in transverse shear specimens; (2) it underestimates shear stress at failure due to severe stress concentration at weld end in typical longitudinal shear specimens. These two limitations have been shown to be the major cause for having two significantly different shear strength values: one is transverse shear strength obtained from transverse shear specimens and the other is longitudinal shear strength obtained from longitudinal shear specimens.     

大直径盾构隧道穿越建筑物群变形分析与控制措施北大核心CSCD

大直径盾构隧道掘进施工对土体造成扰动,导致地表产生沉降或隆起,继而严重威胁上部建筑物群的结构安全。文章依托某大直径盾构隧道穿越老旧小区密集建筑物群工程,首先利用二维有限元软件计算关键断面房屋的沉降变形,再对比三维有限元软件的计算结果,分析两种计算方法的适用范围;然后基于三维模型探究了不同初期荷载释放率对盾构穿越引起的地表和房屋变形的影响,最后利用Peck公式计算的理论地表沉降数据,梳理初期荷载释放率、地表沉降、地层损失率三者的内部联系并提出了控制变形的相关措施。研究结果表明,初期荷载释放率越小,地表及房屋沉降也越小,对应的地层损失也越小;对于控制地表变形,减小荷载释放率等同于减小地层损失率;初期荷载释放率、地表沉降、地层损失率这三者减小的量值呈线性关系。     

深水半潜式钻井平台总体强度分析及冰载荷下结构评估

本文主要概述了某深水半潜式钻井平台的特点,按照DNV的相关规范,采用了有限元法和设计波法,建立了总体有限元模型,分析了在风暴自存工况下的总体屈服强度和屈曲强度,并进行了冰载荷作用下的结构评估。可得到结论,总体屈服强度和屈曲强度是满足的。本文可以为以后同类平台的总体强度分析提供借鉴。     

强化处理工艺影响膜片弹簧载荷变形关系的分析

研究了强化处理工艺对膜片(碟形)弹簧载荷变形特性的影响机理,并进行了载荷变形特性试验,通过试验数据分析载荷变形与喷丸、强压等强化处理工艺的关系,发现残余应力是强化处理效果的主要表现形式.采用X射线应力仪对样件进行了残余应力测试,分析了残余应力的分布规律,发现残余应力和局部材料特性改变是影响载荷变形的主要因素,由此给出了初步解决方案.     

Load-leveling suspension system with a magnetorheological damper

In this paper, a load-leveling suspension system with a magnetorheological (MR) damper is investigated. In this suspension system, the MR damper is connected to a spring to form a load-leveling suspension system. The system effective stiffness and damping can be adjusted by controlling the MR damper. The characteristics of a load-leveling suspension system are studied first. When the linear damper is replaced with an MR damper, the averaging method is adopted to obtain the steady-state response of the nonlinear system. A comparison demonstrates that the results of the averaging method are in good agreement with those obtained by numerical simulations. The analytical results are then verified experimentally. The load-leveling suspension system studied here is able to adjust both suspension stiffness and damping and, hence, it may provide more effective vibration control in a wider frequency range, when the damper is controlled.     

采用简化方法的船体结构疲劳强度校核

本文介绍用简化方法进行船体结构疲劳强度校核的基本原理。这一方法已为中国船级社近期编制的《船体结构疲劳强度指南》所采纳。文中介绍了疲劳载荷的计算,疲劳应力的计算及疲劳累积损伤的计算,并给出例题说明这一方法的具体应用。     

轴载测定与轴载谱分析

在路面设计中轴载是很重要的交通参数，要获得实际轴载谱，最准确的方法就是进行轴载调查，目前国内对轴载调查的方法，调查的内容，使用的仪器要求以及轴载谱的表现形式等还没有进行过系统的研究，尚未形成统一的规定，本文论述了轴载测定与轴载谱分析的方法和各个环节的要求，并结合上海市的轴载测定给出了实例和建议，为标准轴载测定和轴载谱分析方法的形成提供参考。     

运输管理信息系统中车辆配载研究

提出货运优化调度中车辆配载所需的专家知识和策略,考虑一站零整车配载、货物配装优先级、同等优先级货物装车次序和危险品配装问题。建立了重量、体积和货物不规则性约束下的配装专家系统模型,给出详细的配载专家系统规则。采用VB和SQL编程实现运输管理信息系统,采用深圳市的某大型货运中心的实际数据进行试验,试验结果显示该方法合理可行。     

离岸结构所受到波浪载荷与风载荷的组合

给出了确定波浪载荷及风载荷组合特征值的一种新方法,其目的就是要估计波高与风速的非高斯性及相关性对组合载荷特征值的影响。利用Terada的矩估计法,确定组合载荷的统计矩、组合载荷过程导致的方差及波浪载荷与风载荷的相关系数。采用Winterstein的以矩为基础的上通率估计法,确定组合载荷的上通率及极值,数值例题展现了波高及风速的非高斯性及相关性对组合载荷特征值的影响,结果表明忽略非高斯性及相关性会导致组合载荷特征值的低估。