超声导波技术检测长管拖车气瓶研究

为了解决长管拖车气瓶瓶体内部缺陷快速无损检测的难题，利用超声导波技术对长管拖车气瓶试块进行检测。结果显示：超声导波技术一次检测的距离沿波束方向可以达到1m，并且可以准确的发现不同大小的V形槽缺陷。缺陷的位置和长度大小可以准确的测量，并且和实际测量值取得了良好的符合。试验结果很好地证明了超声导波技术的快速准确的优点，对实际现场检测具有指导意义。     

Optimization to the tube-fin contact status of the tube expansion process

The tube-fin contact status is an important factor influencing both thermal resistance and service life of the tube-fin heat exchanger. Tube expansion process brings forming defects of gaps at the tube-fin interfaces. And elimination of this forming defect is proved to be difficult. This paper presents a novel method in improving the tube-fin contact status of heat exchanger. From simulation results, distribution of the contact pressure along the tube-fin interface can be obtained. Then, an optimization process integrated with FE simulation is established for the sectional profile of the fin collar. The fin collar is represented with spline curves. Results show that after the optimization, the gap at the tube-fin interfaces is basically eliminated and the tube-fin contact status is significantly improved. Furthermore, flanging process for the optimized sectional shape of the fin collar is discussed.     

Error evaluation on experimental stress–strain curve obtained from tube bulging test

To get precise material data for advanced numerical modelling of tube hydroforming process, the tube bulging test is recommended. Stresses and strains in the tube cannot be evaluated easily and several approaches have been proposed. A review is proposed and points out their advantages and drawbacks.     

蒸汽发生器管头焊缝撕裂的失效分析和解决办法

分析了蒸汽发生器管头焊缝发生撕裂事故的原因,提出了有针对性的改进措施,取得了明显的改进效果。     

Study on the real-time size distribution of smoke particles for each fire stage by using a steady-state tube furnace method

For the analysis of the adverse effects of smoke on health, it is essential to determine the amount and location of smoke particles deposited in the respiratory tract. However, the deposition characteristics of the particles are influenced by their morphology and size distribution. Moreover, the real-time particle size distribution during inhalation is important for determining smoke particle deposition in the lungs. Smoke particles generated under different fire conditions differ in their physical and chemical characteristics. Thus, there is a need to adopt international standard methods for characterizing the particles generated in fire. In the present study, the size distributions together with morphology of smoke particles were measured for each fire stage by using the steady-state tube furnace method given in ISO/TS 19700. The size distributions of smoke particles from wood and polypropylene (PP) were measured in real time by using an electric low-pressure impactor (ELPI⁺), and their morphologies were analyzed using transmission electron microscopy (TEM).     

A study of manufacturing tubes with nano/ultrafine grain structure by stagger spinning

A new method of manufacturing tubes with nano/ultrafine grain structure by stagger spinning and recrystallization annealing is proposed in this study. Two methods of the stagger spinning process are developed, the corresponding macroforming quality, microstructural evolution and mechanical properties of the spun tubes made of ASTM 1020 steel are analysed. The results reveal that a good surface smoothness and an improved spin-formability of spun parts can be obtained by the process combining of 3-pass spinning followed by a 580 °C × 0.5 h static recrystallization and 2-pass spinning with a 580 °C × 1 h static recrystallization annealing under the severe thinning ratio of wall thickness reduction. The ferritic grains with an average initial size of 50 μm are refined to 500 nm after stagger spinning under the 87% thinning ratio of wall thickness reduction. The equiaxial ferritic grains with an average size of 600 nm are generated through re-nucleation and grain growth by subsequent recrystallization annealing at 580 °C for 1 h heat preservation. The tensile strength of spun tubes has been founded to be proportional to the reciprocal of layer spacing of pearlite (LSP), and the elongation is inversely proportional to the reciprocal of LSP. This study shows that the developed method of stagger power spinning has the potential to be used to manufacture bulk metal components with nano/ultrafine grain structure.     

Primitive chain network study on uncrosslinked and crosslinked cis-polyisoprene polymers

In this paper, the polymer chain packing and primitive path (PP) network of uncrosslinked and crosslinked cis-polyisoprene (PI) polymer are analyzed upon employing coarse-grained molecular dynamics simulation. The crosslinking effect is found to enhance intra-chain packing of PI polymers, while weakening their inter-chain packing. Surprisingly, these effects cancel each other in the global packing behavior of this polymeric system. We systematically study the effects of molecular weight (MW) and crosslink density on the PP. Both the PP contour length and number of entanglements per chain, 〈Z〉, are found to increase linearly with MW for uncrosslinked cis-PI. The corresponding entanglement molecular length N_e of cis-PI is estimated to be 76 ± 1, in good agreement with experimental results. The polymer end-to-end distance, the PP contour length as well as 〈Z〉 of crosslinked PI are reduced by higher intra-chain packing density, compared with uncrosslinked PI, if the crosslinkers are ignored in the PP analysis. At the same time, the tube diameter of crosslinked PI is enlarged by the sparse inter-chain packing. By dividing the crosslinked cis-PI chain network into subchains through crosslinked or crosslinker beads, the PP networks of these partial systems are treated as well. We obtain scaling laws between MW/crosslinking density and 〈Z〉 for crosslinked PI polymers. The simulation results indicate that the random walk assumption, often encountered during the analysis of PPs, can only be applied to the entanglement-dominated (low crosslink density) polymers. For crosslink-dominated (high crosslink density) polymers, whose subchains have a molecular length below 100, this assumption would imply a greatly overestimated entanglement density; we thus avoid the assumption in our analysis. To our best knowledge, this is the first work to uncover the PP of crosslinked polymers.     

管材剪切新方法─带芯棒圆周剪切法的工作原理及其剪切过程分析

为了使切断管材时切口没有毛刺、断面平整、仍能保持原状而且没有金属损耗、没有噪音，提出了用带芯棒的圆周剪切法剪切管材。本文阐述了双芯棒圆周剪切法和单芯棒圆周剪切法的工作原理，并对其剪切过程进行了分析研究。     

包覆吸水性材料椭圆管式间接蒸发冷却器的理论与实验研究

从吸水性材料、换热器结构及布水方式入手，设计了采用功能性纤维套、铝箔椭圆管和间歇性供水方式等强化换热措施的间接蒸发冷却器结构。功能性纤维套采用异形涤纶和Lanseal纤维混纺而成，大大加强了水膜导热和水膜表面的蒸发能力；间歇性供水方式保证了管外纤维套凹坑及纤维凹槽不会被水膜堵塞，提供了足够的换热面积；使用铝箔椭圆管并对排列的几何参数进行优化设计，使间接蒸发冷却器的换热性能达到最优化。实验结果表明这种新型管式间接蒸发冷却器和板式间接蒸发冷却器有相近的换热效率E，但阻力明显小于板式。     

基于组态王的顶管机监控系统

本文介绍基于一种组态软件的顶管机监控系统的组成、通讯与主要画面及其功能。系统界面友好、生动直观、性价比高。