Study on a high frequency pulse tube cryocooler capable of achieving temperatures below 4 K by helium-4

High-frequency pulse tube cryocooler (HPTC) has advantages of compact structure, low vibration, high reliability and long operation time. In this study, Theoretical analysis and experimental tests have been conducted in four aspects based on a developed 4 K HPTC. Firstly, a compressor with larger power output capability was employed and the impedance match between the cold head and the compressor was discussed. Secondly, simply using inertance tube configuration to replace the traditional inertance tube-gas reservoir structure. Then, the type and the size of the regenerator materials working at 4–20 K have been experimentally optimized. Finally, the performance of double-inlet working at as low as 20 K has also been tested for the first time for the HPTC. The present prototype achieved a no-load temperature of 3.6 K, which is the lowest temperature record ever reported for HPTC using helium-4 as working gas. A cooling power of 6 mW/4.2 K was also obtained with 250 W input power and a precooling power of 12.1 W/77 K.     

地铁车站盖挖逆作钢管立柱受力机理及工程应用

以深圳地铁11号线与6号线换乘站松岗站的盖挖逆作法施工为工程研究对象,在介绍盖挖逆作设计方案的基础上,对钢管立柱—围护结构体系进行了受力分析计算,提出了盖挖钢管立柱施工方案,分析了施工的重点难点,最后提出了有效的施工处置措施。     

钢管混凝土支架沥青水泥砂浆可缩性接头可行性分析

目前钢管混凝土可缩性支架仍沿用U型钢可缩性支架的接头方式,致使钢管混凝土支架优良承载性能得不到发挥、总体承载能力不高。现提出一种钢管充填水泥沥青砂浆的可缩性接头。首先,需找出一种水泥沥青砂浆配合比,接头钢管充填该配合比浆体,在额定工作阻力作用下,位于接头钢管上的开孔开始向外排出浆体。需要对浆体配比、接头承载性能、接头钢管开孔面积等问题开展研究。     

37Mn5�ܲ��ڱڱ����Ϲİ�ȱ���γ�ԭ�����

针对37Mn5合金管坯经穿管后在管材内壁表面上形成大量条状鼓包缺陷,利用金相显微镜、扫描电镜及能谱分析等检测手段,对鼓包进行分析。结果表明,在管坯基体中存在较大尺寸的复合型条状夹杂物。此类夹杂物分割了金属基体的连续性,在管壁上形成小夹层。在穿管过程中因受到轴向摩擦力和轴向碾制力挤压,小夹层皱起并与基体脱离形成鼓包。因此,提高钢水的纯净度是减少或消除鼓包缺陷的主要措施。     

高翅管蒸汽加热器的设计及改进

介绍高翅管蒸汽加热器的结构形式、工艺流程和主要参数,详细分析其强度计算、材料选择等方面的设计特点,以及为保证运行安全而在结构和工艺方面所采取的设计改进。     

Heat transfer effects in nano-aluminum combustion at high temperatures

Recent measurements of nano-aluminum combustion in which burning time and peak particle temperature are measured simultaneously have suggested that heat transfer models currently used for burning nanoparticles may significantly overestimate heat losses during combustion. By applying conventional non-continuum heat transfer correlations to burning nano-aluminum particles, the observed peak temperatures, which greatly exceed the ambient temperature, should only be observable if the burning time were very short, of the order of 1 μs, whereas the observed burning time is two orders of magnitude larger. These observations can be reconciled if the energy accommodation coefficient for these conditions is of the order of 0.005, which is the value suggested by Altman, instead of approximately unity, which is the common assumption. Experimental data obtained in the heterogeneous shock tube under a wide array of conditions are compared with basic heat transfer models, and the agreement of both peak temperature values and emission intensity traces for low energy accommodation coefficients supports the hypothesis of Altman and co-workers.     

WHF型夹套反应釜筒体设计压力分析和校核

文章介绍了夹套反应釜的类型及受力分析，对夹套反应釜的实际操作受力情况进行了归纳，提出了夹套反应釜内简壁厚的设计关键是确定设计压力．总结出其设计思路和方法，在实际生产中得到验证。     

Strength prediction of sheet to tube single sided resistance spot welding

Single-Sided Spot Welding (SSSW) procedure is considered as a feasible method to join hydroformed or closed section parts to others in vehicle productions. A ‘doughnut’ shaped or ring nugget can be formed between the two workpieces during this process. The strengths of conventional button spot welds can be determined by the attributes of weldments and many functions that link weld diameter, sheet thickness and material properties to weld strength have been established. For welds of sheet to tube joining, the strength prediction model is greatly different from that of conventional welds for the completely different nugget form. In this study, computer experiments were conduced using the concept of design of experiments (DOE) and the method of finite element used to simulate the tensile-shear tests. The stress and strain distribution contour clouds during tensile-shear process were analyzed and quantitative relationship models were established to link a weld’s geometric and material properties to its tensile-shear strength. The results can give a simple judgment whether a ring spot weld was good only by its appearance.     

材料是保证微波电子管制造的决定因素

微波电子管设计与制造过程中合理选用材料，除了解材料的电性能、热性能、真空性能外，还要对材料的综合机械性能、物理和化学性能均有较高的要求。材料的性能是微波电子管的质量、可靠性、安全性和发展的决定性因素。     

厦门市BRT一期工程车站站台雨蓬制造技术

结合厦门市快速公交系统(BRT)一期工程车站站台雨蓬制造实践,针对站台雨棚弧形刚架的结构特点、工艺难点和现场施工条件,介绍了用钢板组拼方法自制弧形方钢管的重点工艺技术,以及防止焊接变形等的质量保证措施。