冷冻水冷器冷却强化与节能斜齿扭带技术

现有的热流体动力塑料光滑扭带的自转力矩较弱，不能用于较低流速的冷冻水冷器污垢的自动清洗。作者为此研制了一种强化自动清洗力矩的斜齿扭带。其原理是在扭带表面上以一定间距捧列反对称斜齿，被导向的传热流体对扭带的不对称反作用力形成一个旋转力矩。与现有光滑无齿的自转扭带相比，弧线形斜齿扭带自转清洗力矩增大了75％-101％、传热系数提高了186％。虽然阻力系数较高，但是设备阻力仍然不太大。对于6米长传热管、4管程的设备、0．5m/s流速时的设备阻力在36000pa左右，具有广阔的应用前景。因此，这种新技术很适合在0.5m/s以上的较低流速冷冻水冷器中用来自动清洗保洁和传热强化节能。     

一种自动清洗式传热强化新元件 ——旋流口椭圆齿平带

针对斜齿螺旋扭带的制造困难,提出了一种自动清洗式传热强化新元件--旋流口椭圆齿平带,每个椭圆齿都是使平带自转的流体动力结构元素,平带两侧的旋流口使管内的部分液体形成螺旋线流,因而具有近似斜齿螺旋扭带那样能够在较低流速下自转、实现管内污垢在线自动清洗的性能。同时流体经过椭圆齿后产生的大量涡流、管内部分液体转变成的螺旋线流以及螺旋线流与轴向流线不断交错混合等三方面的综合作用,使管内对流传热得到强化。对椭圆齿的齿距、斜角和旋流口三个因素进行了试验研究,结果表明：旋流口椭圆齿平带在管内流速为0.5 m/s左右就能可靠旋转运行;相对于光滑螺旋扭带,旋流口椭圆齿平带的管内侧传热系数可提高171％;其在管内流速为0.625 m/s时的流体阻力为3.25 kPa/m,流体阻力在一般工程许可的范围内。因此,旋流口椭圆齿平带具有良好的综合性能,并且又容易制造,具有较高的工程应用价值。     

制冷系统低流速冷凝器的斜齿扭带自动清洗技术

制冷系统的大多数水冷式冷凝器的流速低,普遍存在不同程度的污垢问题.光滑扭带的自动清洗力矩太弱,不能应用.为此研究能够显著强化自动清洗力矩的一种斜齿扭带.与光滑扭带相比,斜齿型扭带自转清洗力矩增大了260%,传热系数提高了35%,并且设备阻力不大,值得推广应用.     

管内清洗防垢螺旋齿管的流体动力优化设计

为了给螺旋齿管的结构优化提供设计理论,运用动量矩原理和自转牵连运动的运动学分析方法等,研究建立了传热管内流体动力螺旋齿管的自转清洗动力矩计算式,以此指导设计了不同结构参数的螺旋齿管进行试验比较。优化得到的D型塑料螺旋齿管与光滑纽带相比,自转动力矩增大141％,可以在0.4 m/s以上的较低流速下应用;传热系数平均提高50％;阻力在一般工程容许范围。     

冷凝器自转塑料纽带自动在线连续除垢防垢技术研究

本文介绍了自转塑料纽带的自动除垢防垢和传热强化的原理及其试验结果 ,并且进一步计算分析了应用该技术可以为电厂汽轮机带来的增产效益     

立式蒸发式冷凝器强化传热实验研究

在立式蒸发式冷凝器水蒸汽排汽冷凝实验基础上,对圆管、插入螺旋线圆管和波纹管3种管形的立式蒸发式冷凝器进行强化传热研究.结果表明:采用插入螺旋线圆管或者波纹管都可以起到强化传热的效果,总传热系数K比圆管分别高8.7%、12.9%,但要付出增加空气流动阻力作为代价;Rwa是整个传热过程的控制热阻,它具有改变总热阻的最大潜力;插入螺旋线对降低气-液界面的热阻尤为明显,降幅达20.65%;波纹管对降低凝结换热侧的热阻尤为明显,降幅达35.85%.     

新型强化生态塑料研制成功

芬兰国家技术研究中心最近研制出一种新型强化生态塑料。用玻璃纤维作为增强材料的传统塑料不仅不易回收,而且在燃烧处理的过程中会释放出二氧化碳,对     

LNG汽化器换热管内螺旋线圈传热性能强化研究

建立了LNG汽化器换热管内的流动传热模型,研究LNG与蒸气换热的传热特点。模拟结果显示由于换热温差过大,采用光管换热管会发生管内膜态沸腾,无法实现LNG的高效汽化。提出在换热管内添加螺旋线圈内插件抑制膜态沸腾,换热性能提升可达77.1%,出口温度可达230.1 K,能够满足LNG汽化器的技术指标。对螺旋线圈的结构尺寸进行对比分析。线径从1 mm增至1.4 mm能提升换热效率并且不增加压降,而将节距从10 mm增值15 mm会导致流动传热性能恶化。     

弥散强化铂基材料的研究现状

弥散强化铂基材料是一种先进的结构型与高温型贵金属复合材料,并且是玻璃纤维漏板材料发展的主要方向.综述了弥散强化铂基材料的制备方法及其优缺点,总结了目前弥散强化铂基材料中存在的固溶强化、晶界强化及弥散强化的强化机理及其研究进展,介绍了弥散强化铂基材料的组织结构特点及其蠕变特征、常温高温下的主要性能、应用以及新的发展动向,为弥散强化铂基材料的选择、研究以及工业化应用提供了参考依据.     

镁合金强化研究的发展现状

镁合金是一种新兴的金属结构材料,提高其室温和高温强度是扩大镁合金应用的有效途径之一.从细晶强化、热处理强化和稀土合金强化3个方面阐述了镁合金的强化问题,重点分析了不同强化方法的机理和特点,指出了镁合金强化存在的问题和今后的发展方向.     

The J-integral at Dugdale cracks perpendicular to interfaces of materials with dissimilar yield stresses

The J-integral is applied to a Dugdale crack perpendicular to an interface of materials with equal elastic properties but different yield stresses. It is shown that the integral is path independend with certain limitations to the integration path. Three essentially different paths can be distinguished. The first integration path is totally within the first material, it provides the local crack driving force. Performing the integral around the plastic zone in both materials gives the global crack driving force. An interface force can be defined by evaluating the integral along both sides of the plastically deformed region of the interface. A comparison of these three integrals reveals that the global crack driving force is equal to the sum of the local crack driving force and of the interface force. The derived expression for the J-integral are compared with the crack tip opening displacement published recently. This reveals that the local J describes the plastic deformation at the crack tip. Therefore it represents the crack driving force in bimaterials as it does the conventional J-integral in case of homogeneous materials. The analyses are also extended to cyclic plasticity, where an out-of-phase effect is observed. Finally it is discussed how these results can be used to explain fatigue tests at bimaterial specimens.     

Chemical driving force for dislocation motion in hydrogen embrittlement

Two major effects of hydrogen in metals, particularly iron and its alloys, are proposed here. The first is the effect of hydrogen on plastic behavior. It is proposed that during charging or discharging a large chemical driving force can generate and move dislocations to facilitate hydrogen transport. The second is the effect of hydrogen on fracture. It is proposed that the dislocations emitted by the chemical driving force can exert a sufficient stress intensity factor at the crack tip to cause propagation along the slip plane, even without any externally applied stress.     

Effect of dynamic plastic deformation on microstructure and annealing behaviour of modified 9Cr−1Mo steel

The effect of dynamic plastic deformation on the microstructure of a modified 9Cr?1Mo steel has been investigated in comparison with the effect of quasi-static compression. It is found that the boundary spacing after dynamic plastic deformation is smaller and the hardness is higher than those after quasi-static compression. The microstructure after dynamic plastic deformation is however less stable than the microstructure after quasi-static compression. Annealing at 675 and 700°C leads to structural coarsening and recrystallisation in each sample, but with recrystallisation occurring faster in the sample annealed after dynamic plastic deformation. The lower thermal stability of the microstructure produced by dynamic plastic deformation is attributed to a higher driving force for recrystallisation in the dynamically deformed material.     

Study of electrical characteristics of the ball bearing motor

The electrical characteristics of the ball bearing electric motor are studied for applied steady currents ranging from 43.5 to 70.15 A. It is found that the ball bearing behaves like a motor when it starts self-rotating meaning that the shaft and inner race of the pair of the ball bearing system start rotating by themselves without the help of any external agent, but with a small efficiency at high currents. During self-rotation the motor's counterelectromotive force depends on the angular velocity of the shaft and inner race. The ball bearing's behavior at low currents is also explained when it is not self-rotating, (i.e. rotating with the help of a conventional motor). In the latter case, the motor does not behave like a generator. A theory, based on the electromagnetic interactions developed within each ball, is proposed to explain the action of the ball bearing as a motor. These interactions are caused by the ball's primary currents and magnetic fields and the effects of the induced magnetic field from the current of the motor's shaft     

APPLICATION OF ENERGY DISSIPATION RATE ARGUMENTS TO DUCTILE INSTABILITY

Abstract— Equations are established for the final macro-unstable behaviour of a fully plastic cracked component in terms of the energy dissipation rate. Control by this first differential of energy occurs when the second differential of the energy absorbed is negative, a condition easily met for crack growth in certain fully plastic cases. The driving force for the instability is a term, I that becomes greater than the lefm term, G , as plasticity occurs. The additional component is an exchange of elastic to plastic energy, a term that is system dependent and is thus the main driving force for a fully plastic ductile instability. A possible relevance to brittle fracture and to a system dependence of both initiation toughness and the whole crack growth resistance curve is discussed.     

基于塑性铰模型的三塔斜拉桥抗震能力时程分析

摘要：采用非线性塑性铰考虑结构构件的混凝土开裂、钢筋屈服和材料滞回效应,利用APDL语言编制二分法程序使计算机进行自动计算和减少计算量,从而建立通过不断增大地震时程作用来计算斜拉桥结构抗震能力的方法,并以该方法分析研究了一座在建的三塔结合梁斜拉桥的抗震能力和地震反应特性。研究结果表明：在抗震能力状态,三塔斜拉桥中塔底内力响应要远大于边塔,但由地震引起的塔顶位移却相差很小,所以提高中塔抗震能力可以较快地提高整体结构的抗震能力;有塑性铰模型要比无塑性铰模型具有更高的抗震能力;采用二分法循环计算程序,不仅可以降低人工试算的烦琐而且能大幅减少循环计算次数,使大型结构的抗震能力分析较为简便。     

Mechanical analysis of indentation cracking in Al2O3/ZrO2 nanostructured laminated ceramics

Residual stress is not the only driving force for indentation cracking in Al2O3/ZrO2 laminated ceramics. An additional driving force is induced by martensitic transformation in the plastic zone beneath the indenter, whereas surface residual compressive stress controls the expansion of surface cracks. Contributions of the transformation driving force and surface residual stress are not considered in the traditional indentation and indentation-strength theory. Therefore, fracture toughness value measured by the traditional methods is usually lower than the practical one in Al2O3/ZrO2 laminated ceramics. When the improved SENB (Single edge notched beam method)-indentation-fracture method from Japanese Industrial Standard (No. JIS R 1607-1990) is used to measure fracture toughness of Al2O3/ZrO2 laminated ceramics, the value is more reliable.     

CFRP加固火灾作用后圆钢管混凝土构件的侧向撞击性能研究

建立了火灾作用后和碳纤维增强复合材料(CFRP)加固受火后圆钢管混凝土构件的侧向撞击数值模型,通过不同试验分别验证了模型的准确性.分析了加固受火后构件的撞击全过程,对比了构件的撞击力、跨中挠度和截面弯矩.对构件的抗撞击承载力和抗弯承载力,塑性变形和吸能能力,以及内力分布与发展进行了分析,并给出构件在撞击荷载作用下跨中最...