Selective Laser Melting of Maraging Steels Using Recycled Powders: A Comprehensive Microstructural and Mechanical Investigation

Selective laser melting (SLM) is an additive manufacturing (AM) technique designed to use a high energy density laser to fuse metallic powders for producing three-dimensional parts. So far, most studies of SLM have been focused on using virgin metal powders. There are few comprehensive studies on the microstructure and mechanical properties of SLM-produced parts using recycled powders, especially for maraging steels. In this study, we employ recycled steel powder (reused after 113 building cycles) in the SLM process to print multiple shaped components and systematically characterize the microstructure and mechanical properties (indentation, tensile, and Charpy testing). Our results show that maraging steel produced with recycled powder exhibit the nearly identical microstructure and mechanical properties (940 MPa yield strength, 1127 MPa ultimate tensile strength, 11 pct elongation, and 47.5 J room temperature impact fracture energy) to those produced using virgin powders. This study provides a useful generic guide towards using recycled metal powders in the SLM processing, promoting an economic solution to industrial productions.

     

自动翻越式玻璃幕墙清洁机器人设计

玻璃幕墙清洗高空作业的"蜘蛛人"存在极大的安全隐患,而现有自动擦窗机器人普遍是单面作业,无法实现高空全范围的清洗工作.设计一款可自动翻越式玻璃幕墙清洁机器人,对其结构、力学性能和可行性进行分析与研究.在机器人直线运动和跨越障碍两种状态下进行静力学分析,得出擦窗机器人各运动状态下的最小吸附力;利用有限元方法对真空箱体进行可行性分析,计算得到清洁机器人在两种工况下密封条的接触应力,从而确定真空箱体所需的真空度,为实际清洁机器人的应用提供理论支持.     

炭黑对给水用聚乙烯管材物理性能的影响

采用不同炭黑比例的聚乙烯(PE)管材,研究了炭黑对PE管材物理性能的影响.结果表明,炭黑对PE管材的氧化诱导时间(OIT)、拉伸性能、密度均有一定的影响;相同的原料和工艺下,密度与炭黑含量呈线性关系,随着炭黑含量的增加,密度也随之增大;在炭黑含量为1.43％～3.51％区间内,随着炭黑分散等级的增大,OIT变小,并且与...     

某火力发电厂600MW机组低温再热蒸汽管道恒力吊架吊杆断裂原因分析及解决方案

针对某火电厂锅炉低温再热蒸汽管道恒力吊架螺纹吊杆多次发生断裂现象,通过支吊架分布及其断裂分析、材质及其断口分析、断裂力学计算,得出吊杆断裂原因为管道异常振动对吊杆产生弯曲疲劳作用所致。根据恒力吊架本身结构特点及管道运行状况提出行之有效的解决方案,可提高机组安全经济运行。     

Parameter optimization of moving horizon estimation based on hybrid intelligent algorithm

In the application of moving horizon estimation (MHE) algorithm, the window length will affect the estimation accuracy and the computing efficiency. For this kind of problem, a method of parameter optimization is proposed to obtain suitable window length. Firstly, in order to facilitate online solution, the optimization problem involved in the algorithm is transformed into a quadratic programming (QP) problem in matrix form. Secondly, for the time index and the estimated residual index that measure different properties, the normalization idea is adopted to incorporate them into the same dimension to design the fitness function, and a genetic optimization algorithm based on simulated annealing mechanism is given to search for the optimal window length. Finally, the proposed parameter optimization method is verified by two cases. The results show that the parameter optimization method has the advantages of excellent local search ability and sufficient convergence, and the window length obtained by this method can better take into account the two performance indexes of the MHE algorithm and improve the estimation performance.     

Distributed second-order multi-agent constrained optimization algorithm with time-varying cost function

This paper mainly discusses distributed constrained optimization problem for second-order multi-agent system under undirected communication network. The task of all agents is to minimize the sum of the local convex functions, where each agent is individual and only accesses to one objective function. Different from the most existing results, where the objective functions are assumed to be time-invariable, this paper considers the situation of time-varying objective function. Besides, we don't require that the Hessian matrices are identical and the gradients are bounded. First, a novel time-varying optimization algorithm is proposed based on the projection algorithm. Second, by using convex analysis and Lyapunov theory, it is shown that the states of all agents can reach consensus and asymptotically converge to the neighborhood of the optimal solution. Finally, some numerical examples are given to verify the effectiveness of our algorithms.     

未来配电网的主要形态¾¾基于储能的低压直流微电网

储能技术的不断进步,为未来配电网的发展提供了新的思路。提出了一种未来配电网的可能形态——基于储能装置、以用户为单位的低压直流微电网。同时论述了该形态配电网的结构特征和优越性以及当前技术与这个设想之间的差距。在当前技术水平下,低压直流微电网和储能装置的充放电管理领域的技术已经能够满足设想需要,但是储能装置的能量体积比和能量重量比以及寿命还存在较大差距。随着储能技术的不断进步发展,未来配电网必将发生革命性的变革。     

迷彩伪装目标图像语义分割数据集的构建

数据集是基于深度学习语义分割技术的重要组成部分。为了将语义分割技术应用于野外战场环境,构建一个符合实战场景的数据集至关重要。针对迷彩伪装目标侦察识别的作战保障需求,分析了野外战场环境及战场侦察图像的特点,设计了特定场景数据集的构建流程与方法,构建了具有精细化语义标注的语义分割数据集CSS,并通过实验验证了该数据集在语义分割任务上的有效性。     

链箅机-回转窑工艺生产碱性球团矿工业试验

在实验室研究的基础上,开展了链箅机-回转窑工艺生产碱性球团矿工业试验.结果表明,生产二元碱度(CaO/SiO2)为1.0左右的球团矿时,与酸性球团矿生产工艺相比,将预热段温度提高30℃左右,回转窑窑头温度降低10℃左右,链箅机的机速降低0.3m/min左右,成品球团矿的抗压强度可达到或稍高于酸性球团矿.碱性球团的还原膨...