气体流量和牵引速度对熔制石英管尺寸的影响

石英管作为特种工业技术玻璃，具有透光性好、电绝缘性好、耐腐蚀、耐高温等性能。无接触拉管法拉制成型石英管的尺寸主要受到加热功率、母材尺寸、管内气体流量、牵引速度的影响。本文主要探究管内气体流量、牵引速度对石英管尺寸的影响。通过参数公式计算，可快速调整工艺操作拉制所需石英管。     

空调系统电热加湿段性能数值模拟研究

电热加湿器是空调系统的常用设备,具有加湿精度高、湿度易于调节等优点,但同时也存在加湿段风速较高时难以加湿的问题。本文分析了电热加湿器的工作原理及其存在的主要问题,采用试验和数值模拟相结合的方法,研究了电热加湿器加热功率对产汽量及蒸汽喷管出口压力的影响,以及加湿段截面积对加湿系统加湿性能的影响,研究结果表明：增大电热加湿器加热功率或增大加湿段截面积有利于提高加湿系统的加湿性能。     

点源法计算油罐火灾中的热辐射

在油罐火灾中，着火罐的火焰所释放出的热量通过热辐射的方式传到邻近罐的罐壁，对罐内液体、气体进行加热，当气体的压力增长超过罐顶泄压阀的泄压速度时，管内压力增长，压力超过一定值时导致罐体物理性爆炸。此文通过数学模型模拟假设整个热辐射过程，对辐射热进行定量分析。     

打破国外垄断研发世界一流石英玻璃

石英玻璃是现代科学技术的重要新材料,为电光源、电子、激光和航天航空等高技术领域提供了大量关键材料。普通石英玻璃是用天然水晶或硅石作原料经高温熔制而成的,高纯优质石英玻璃则使用无机或有机含硅的液体化合物（如四氯化硅）经火焰水解合成工艺制成,称为合成石英玻璃（Synthetic fused silica）。     

石英玻璃管成型过程中的几何参数与工艺参数关系研究

石英玻璃管成型过程中的几何参数(外径、壁厚)主要受工艺参数和设备精度的影响,包括温度、管内压力、牵引速度等几个方面,本论文主要研究管内压力和牵引速度对几何参数的影响,通过大量的试验并结合现代传感和计算机技术采集各相关工艺参数,建立工艺参数与几何参数间的回归模型,对高精度石英玻璃管的成型提供理论依据,从而提高产品几何精度。     

天然气水合物冻堵分解技术研究

针对天然气水合物冻堵问题建立一套感应加热实验装置,对比在不同内直径的反应釜内不同感应加热功率下的天然气水合物分解实验结果。对同一反应釜,感应加热功率越大,反应釜釜壁温度升高越快,水合物分解时间越短。感应加热功率恒定时,反应釜内直径越小,釜壁温度升高越快,水合物分解时间越短。     

碳纤维布补强压力管道试验研究及有限元分析

在粘贴不同厚度的碳纤维布(CFRP)的工况下来测定管道的环向应变与内水压力之间的变化规律,以此试验数据与ANSYS数值模拟值进行比较,可知模拟值和试验结果吻合得较好。通过建立有限元模型分析纤维复合材料的弹性模量、管道壁厚、管道直径对管道屈服时承压能力的影响,结果表明:高模量碳纤维加固的管道达到屈服强度时管内可施加的压力最大;管道外径的增大对粘贴了碳纤维布的管道屈服时内水压力值提高比例并无影响,而随着管道壁厚的增加,提高比例却依次降低。为碳纤维布修复补强大型输送管道的设计与施工提供试验基础依据。     

绿色光源──金卤灯

今天通用的照明技术基本上分两类白炽灯和放电灯。白炽灯类,如家居用的灯泡等,是通过加热钨丝来发光的;放电灯类,如荧光灯,高压钠,高压汞灯及金卤灯等,是通过电弧加热使用弧管内气体及金属卤化物丸蒸发膨胀而发光的。 金卤灯属于高压气体放电灯,它之所以会发出高效能的     

形状记忆合金管道连接件的连接性能研究

本文采用试验与数值模拟相结合的技术路线,以Fe基形状记忆合金管道连接件为研究对象,探索了加热训练、配合间隙、连接件壁厚以及连接件长度等因素对形状记忆合金管道连接件连接性能的影响规律。研究结果表明:形状记忆合金管道连接件的壁厚、轴向长度对连接性能的影响呈现双折线形态;减少管道连接件和被连接钢管之间的配合间隙,或者增加管道连接件的加热训练次数,均可以提高管道连接件和被连接钢管之间的径向应力。在实际设计过程中,应综合考虑形状记忆合金管道连接件的连接性能与制造成本,同时考虑被连接钢管的承压能力以及装配难度等因素。     

地面辐射供暖塑料管材最小壁厚的选择

根据累计破坏算法对低温热水地面辐射供暖中5种常用塑料加热管材的最小壁厚计算,给出供设计人员选择管材时的参考表格,并与目前资料介绍4级使用条件的计算壁厚进行比较,验证选用常用壁厚2.0mm和2.3mm在我国几个典型供暖城市的使用寿命以及安全性。     

外部加劲热轧钢管的分析和优化

利用非线性有限元法,分析了采用多种规格外部圆环加劲的圆柱形钢管的拟静力轴向破坏反应。加劲圆环将钢管沿竖向分为一系列的薄壁短柱结构。假定加劲肋的尺寸和形状由机械加工控制。研究了各种不同几何参数,如:钢管壁厚、环间距、环厚度和破坏时环的宽度,极限承载力和整体加劲钢管能量吸收的影响。将研究结果作为优化设计的基本原理。基于计算机模拟试验的分析,利用辐射函数,提出了关于平均承载力和能量消耗的后处理模型。运用单个对象和多个对象优化设计方程,得出不同反应特性的优化设计。根据渐进破坏屈曲得出的破坏模式依赖于加劲肋间距、加劲肋高度比、钢管壁厚以及加劲肋厚度比。优化结果显示,外加劲肋作为高效耗能构件是可靠的。     

配筋薄壁钢管高强混凝土柱的轴心受压性能研究

为了探索配筋对薄壁钢管高强度混凝土柱轴心受力性能的改善机理,进行了18根试件的轴心受压试验。试验中设计了2种混凝土保护层厚度的配筋钢管混凝土及对应的钢筋混凝土、钢管混凝土和素混凝土等6组试件,以弹性阶段、屈服阶段、强化阶段和破坏阶段的荷载与位移或荷载与应变关系、承载力、套箍系数为评价参数,研究了此类构件的基本力学特性,并发现:核心混凝土内配置钢筋后采用薄壁钢管是可行的;要提高钢管混凝土的工作性能,配置钢筋的效果明显优于增加钢管壁厚的效果。最终提出了适合此类构件的承载力计算公式。     

轴压下薄壁管断裂的可能性分析

在车辆的防撞设计中薄壁管作为耗能构件被广泛采用,轴压力是防撞部位承受的最典型荷载之一。为了减轻重量,薄壁管采用轻质材料诸如高强度钢材、铝和镁制成。然而,这些轻质材料中的大多数与传统的钢材相比更脆且易断裂。由于材料的应力、应变状态通常被作为判断其构造断裂点的依据,故对薄壁管的三轴应力分布和时程及其等效应变进行了有限元模拟。分析结果显示,三轴应力和等效应变沿着管长波动,方形薄壁管的断裂更可能发生在边缘而非其他位置。对于相同的轴压冲击,当初始冲击速度在6～24m/s变化时,方形薄壁管内部的应力、应变变化不大。对影响应力、应变状态的参数,包括横截面角的形状、壁厚和横截面形状分别进行研究。所得结果可为薄壁管的设计及轻质材料力学性能的试验特性研究提供参考。     

Axial crushing and optimal design of square tubes with graded thickness

Introducing thickness gradient in cross-section is a quite promising approach to increase the energy absorption efficiency and crashworthiness performance of thin-walled structures. This paper addresses the deformation mode and energy absorption of square tubes with graded thickness during axial loading. Experimental study is firstly carried out for square tubes with two types of thickness distributions and numerical analyses are then conducted to simulate the experiment. Both experimental and numerical results show that the introduction of graded thickness in cross-section can lead to up to 30–35% increase in energy absorption efficiency (specific energy absorption) without the increase of the initial peak force. In addition, structural optimization of the cross-section of a square tube with graded thickness is solved by response surface method and the optimization results validate that increasing the material in the corner regions can indeed increase the energy absorption efficiency of a square tube.     

Analysis and optimization of externally stiffened crush tubes

Nonlinear finite element analysis is used to investigate the quasi-static axial collapse response of cylindrical tubes which are externally stiffened by multiple identical rings. The rings divide the long tube into a series of short thin-walled tubes. It is assumed that the size and shape of integral stiffeners are controlled through a machining process. The effects of various geometric parameters such as wall thickness, ring spacing, ring thickness and width on the collapse response, crush force and energy absorption of monolithic, integrally stiffened steel tubes are studied and used as a general framework for a design optimization study. Through design and analysis of computer experiments, global metamodels are developed for the mean crush force and energy absorption, using the radial basis function approximation technique. Using both single- and multi-objective design optimization formulations, optimum designs for different response characteristics are found. The crush mode in the form of progressive collapse or buckling is found to heavily depend on the ratio of stiffener spacing to stiffener height as well as the ratio of wall thickness to stiffener thickness. The optimization results show the viability of externally stiffened tubes as efficient energy absorbers.     

On the fracture possibility of thin-walled tubes under axial crushing

Thin-walled tubes are widely used as energy absorption components in vehicle crashworthiness design where axial crushing is one of the most typical loading conditions. Lightweight materials such as high-strength steel, aluminum and magnesium have been applied for thin-walled tubes for weight reduction. Meanwhile, most of these lightweight materials are more brittle and easily fractured than traditional steel. Distribution and history of stress triaxiality and equivalent strain in the thin-walled tubes under axial crushing have been analyzed in this article with finite element simulation, as these two parameters of stress and strain states are commonly used for constructing fracture locus of materials. It is observed that both stress triaxiality and equivalent strain are transferring along the tube length like waves. Analysis results show that fracture is more likely to take place on the edge than the other positions of square thin-walled tubes. For identical axial crushing stroke, there is little difference of stress and strain states inside the square thin-walled tubes with initial impact velocity varying from 6 m/s to 24 m/s. Influence of geometrical parameters on the stress and strain states have also been analyzed, including the shape of cross-section corner, the wall thickness and the shape of cross-section, respectively. Analysis results in this article may offer references for design of thin-walled tubes and the necessary experimental characterization of mechanical properties for lightweight materials.     

外包薄壁钢管加固受火后混凝土柱的抗震性能

通过2根未受火钢筋混凝土柱、2根受火后未加固钢筋混凝土柱和10根外包薄壁钢管加固受火后钢筋混凝土柱的拟静力试验,考察了轴压比、剪跨比、钢管厚度及加固方式等参数对外包薄壁钢管加固受火后混凝土柱抗震性能的影响情况,建议了外包薄壁钢管加固受火后混凝土柱受剪承载力的计算公式。结果表明：薄壁钢管加固可显著提高受火后混凝土柱的受剪承载力、极限变形和累计滞回耗能,且加固后试件的割线刚度与未受火试件相比相差较小。受火后剪跨比为1.78和3.0的混凝土柱加固后的承载力分别比相应的未加固柱的承载力提高了41.8%~47.0%和38.5%~74.4%。轴压比对加固后试件的受剪承载力、刚度、耗能能力和延性影响较大,对极限变形影响较小。薄壁钢管厚度对加固后试件的耗能能力影响较大,对受剪承载力影响较小。薄壁钢管根部焊接角钢并用螺栓锚固的方式可提高加固效果。     

Analytical and experimental studies on quasi-static axial crush behavior of thin-walled tailor-made aluminum tubes

In this paper, the crush behavior of segmented circular tubes, made of aluminum alloy 6061 and subjected to quasi-static axial loading, has been analytically and experimentally investigated. Crush behavior of these tubes was modeled by integrating available analytical models and superposition principle. In the certain overall length of segmented circular tubes, effects of changing the wall thickness and length of each segment on the energy absorption characteristics have been evaluated. One successful approach toward obtaining lightweight energy absorbers with high energy absorption capacity is the use of thin-walled Tailor-Made Tubes (TMTs). In these tubes, the thickness and mechanical properties of the wall vary along the length of the tube. Applying these tubes; crush force can be controlled by changing the length and thickness of each tube segment, improving the performance of energy absorbing systems. Results of this research showed that Tailor-made tubes have higher energy absorption capacity at identical crush lengths, and they can absorb more energy per unit weight compared to simple tubes with constant wall thickness and mechanical properties. Moreover, for the same specific energy absorption, the TMTs exhibit a considerable reduction in the magnitude of the mean and initial maximum crush forces. With the use of TMTs, the maximum crush force shifts to the end of the crush range, reducing the exerted deceleration on occupants and equipments. Comparing mean crush force and specific energy absorption obtained by analytical and experimental approaches, it was observed that combining current analytical models with superposition principle can prepare a set of analytical formulations to predict TMTs crush characteristics within an acceptable proximity.     

石英玻璃厚壁管制备工艺的研究

研究了石英玻璃厚壁管加工设备、工装夹具、工艺参数对厚壁管精度及表面质量的影响,确定了厚壁管取芯工艺合适的取芯设备、冷却液、取芯钻头及工艺参数,珩磨工艺合适的珩磨头、冷却水过滤方式及工艺参数,外圆精密加工合适的工装夹具及工艺参数,对石英玻璃厚壁管加工工艺的选择有指导意义。