新型树启发式搜索算法的机器人路径规划

面对三维空间移动机器人从起始点到终止点的最短路径问题,提出一种新型的边缘点树启发式搜索(TreeEP)算法,该方法将地图空间进行密度可调的三维离散化处理,根据障碍安全距离筛选出障碍物的可靠边缘点信息,再利用树扩散架构选出最能引导搜索方向的潜力点进行扩散搜索,最终得出最短路径。提出局部调整策略,得到改进的Tree-EP算法。实验结果表明,在带障碍复杂地形最短路径搜索应用中,提出的Tree-EP算法与已有方法相比,能找到更短的移动路径。     

Development and field test of the articulated mobile robot T2 Snake-4 for plant disaster prevention

Abstract

In this work, we develop an articulated mobile robot that can move in narrow spaces, climb stairs, gather information, and operate valves for plant disaster prevention. The robot can adopt a tall position using a folding arm and gather information using sensors mounted on the arm. In addition, this paper presents a stair climbing method using a single backward wave. This method enables the robot to climb stairs that have a short tread. The developed robot system is tested in a field test at the World Robot Summit 2018, and the lessons learned in the field test are discussed.     

Impact of gas formation on the transfer of Ti and O from TiO2-bearing basic-fluoride fluxes to submerged arc welded metals: A thermodynamic approach

Gas-slag-metal equilibrium calculations are performed to investigate the transfer of Ti and O to submerged arc welded metals with increasing TiO₂ addition in basic-fluoride fluxes. The results indicate that activities of TiO₂ and Ti₂O₃ considering slag-metal reactions alone do not account for Ti transfer behaviors since TiF₃ gas tends to form and reduce Ti-oxide activities. Thermodynamic simulation indicates that consideration of gases is essential to improve the prediction accuracy of Ti and O concentrations.     

硅对304不锈钢GMAW高速焊接头组织性能的影响

以不锈钢焊丝中Si元素含量不同对高速焊焊后焊缝成形以及接头组织性能为研究目的，采用GMAW焊接工艺方法，借助扫描电镜、XRD衍射图谱、拉伸以及微观硬度等力学性能测试作为分析手段，深入研究Si元素在焊缝内部空间分布规律，及其对焊后成形焊缝组织和力学性能的影响规律. 结果表明，焊丝中存在特定含量的Si元素，不仅能够增加熔池金属流动性，提高焊接过程稳定性，改善焊后焊缝成形；同时焊接速度可以大幅提高至120 cm/min；由于Si元素的存在，GMAW高速焊焊后接头组织主要为奥氏体+δ铁素体，焊缝组织得到优化. XRD衍射图谱中发现焊后接头组织中存在马氏体和渗碳体，焊后接头微观硬度有所增加，拉伸性能基本持平，且在拉伸断裂前有明显的颈缩，塑性及抗拉强度良好.     

Fatigue performance of friction stir welded Al2024 alloy in a different corrosive environment

The study examines the corrosion fatigue behavior of friction stir welded Al2024 alloy in the corrosive medium. The fatigue tests are conducted at a stress ratio of -1 in the different corrosive medium. The decrease in the fatigue life of welded joints in the corrosive environment is attributed to an increase in the crack initiation susceptibility in the presence of corrosive media. The fractured surfaces are investigated using the scanning electron microscopy (SEM). The formation of the corrosive compounds was studied using x-ray diffractometry.     

Effect of multi pulse current treatment on microstructure and microhardness of resistance spot welded dual phase steel DP590

In this paper, microhardness and microstructural characteristics of dual phase DP590 steel resistance spot weld joint under two different welding conditions (i. e. single pulse and multi pulse) were studied. It was observed that applying multi pulse currents resulted in quasi-equiaxed grains of tempered martensite in fusion zone (FZ) of the weldment. The refinement of microstructure in fusion zone using multi pulse current treatment resulted in reduced hardness of the weld joint.     

码垛机器人运动学分析及关节空间轨迹规划研究

以IRB-460工业机器人为研究对象,针对其运动学建模及在笛卡尔空间和关节空间下的轨迹规划方法展开研究并进行对比。对机器人本体进行了机器人运动学分析,利用多项式轨迹插值算法进行了关键点间的轨迹规划,完成了重叠型码垛的作业流程。利用Robotics Toolbox完成了轨迹规划算法仿真,并进行了结果分析。仿真结果表明在关节空间下进行轨迹插补所得的路径点更为优化,所得的轨迹更为满足作业任务,具备合理性。     

AlN对铁基合金等离子喷焊层组织和摩擦磨损性能的影响

目的 加入AlN提高铁基合金的摩擦磨损性能。方法 采用PTA-400E3-HB等离子喷焊设备在Q235钢表面制备添加AlN的铁基合金喷焊层。通过光学显微镜、扫描电镜（SEM）和X射线衍射仪（XRD）研究喷焊层的组织和相结构。利用显微硬度计、摩擦磨损试验机和台阶仪对喷焊层的硬度和摩擦磨损性能进行测试。结果 添加AlN的喷焊层主要物相为α-Fe、γ-Fe和(Fe,Cr)7C3。未添加AlN的喷焊层由等轴晶组成，添加AlN的喷焊层呈现柱状树枝晶，且随AlN量增加，树枝晶组织愈加粗大。添加1%AlN喷焊层的平均显微硬度最高，为(890.1±46.8)HV0.3，比铁基喷焊层的显微硬度高131.6HV0.3；当AlN含量增加，未转变奥氏体量增加，导致喷焊层的硬度降低。加入AlN的喷焊层的摩擦系数均降低，摩擦系数稳定在0.40~0.57之间。当AlN添加量为3%时，喷焊层的磨损形貌最光滑，磨损率为1.15×10-14 m3/(N?m)。添加AlN后，喷焊层的磨损机理从之前的粘着磨损变为磨粒磨损。结论 添加AlN能提高铁基喷焊层的摩擦磨损性能。     

焊接线能量对高强钢焊接接头组织性能的影响

采用1.3、1.6、1.9 kJ/mm 3种不同线能量对960QT钢进行焊接，研究了线能量对960QT钢焊接接头组织和性能的影响。研究表明，随着线能量的增加，焊接接头强度下降，但塑性提高，焊缝冲击韧性变化不大，热影响区冲击韧性先降低后增大，热影响区冲击韧性均高于焊缝。对3种线能量下960QT高强钢的焊接接头进行金相分析，发现焊缝组织主要为针状铁素体和粒状贝氏体。随着线能量的增加，针状铁素体发生粗化，数量相对减少，粒状贝氏体数量增多。焊接接头热影响区的金相组织主要为板条M/B和粒状贝氏体。随着焊接线能量的增大，冷却速率减小，粒状贝氏体组织数量相对增加，而板条贝氏体组织的数量逐渐减少。     

Effect of microstructure inhomogeneity on mechanical properties of different zones in TA15 electron beam welded joints

The effects of microstructure inhomogeneity on the mechanical properties of different zones in TA15 electron beam welded joints were investigated using a micromechanics-based finite element method. Considering the indentation size effect, the mechanical properties for constituent phases of the base metal (BM) and heat affected zone (HAZ) were determined by the instrumented nano-indentation test. The macroscopic mechanical properties of BM and HAZ obtained from the tensile test agree well with the numerical results. The incompatible deformation between the constituent phases tends to localize along the softer primary phase α where failure usually initiates in form of localized plastic strain. Compared with the BM, the mechanical properties of constituent phases in the HAZ differ substantially, leading to more serious strain localization behavior.