机头几何尺寸对挤出成型的影响

0引言 影响挤出机成型效果的主要因素有主轴转速、螺旋导程、螺旋封闭长度、机头、机口尺寸及芯架阻力等。不同的原料一般应选用不同的挤出参数与之匹配才能达到最佳效果。我国制砖生产企业大部分缺乏在此方面的深入研究和探讨，造成一套技术参数打天下，从而降低了挤出效率和成型效果，既增加了能量消耗、增加了磨损；同时也影响了制品产量和质量。就机头而言，目前多数挤出机生产厂家也是一个机头打天下，充其量只是为适应制品的出口尺寸而选择机头出口尺寸，很少有从适应原料、满足制品高效成型的角度加以研究和设计。国外，如德国凯乐、林格等公司就非常重视机头对成型的影响，同型号挤出机有多种机头以适应不同地区不同原料成型。机头品种数量之多号称能开机头博览会。本文着重就机头对挤出成型的影响作如下探讨。     

砖坯的挤出成型（二）

简述了泥料在挤出成型时的运动原理和泥料挤出成型中可能出现的各种生产问题。分析了螺旋绞刀、机头、机口、芯具四大部件的功用及挤出成型时需要注意的事项。     

砖呸的挤出成型（一）

简述了泥料在挤出成型时的运动原理和泥料挤出成型中可能出现的各种生产问题。分析了螺旋绞刀、机头、机口、芯具四大部件的功用及挤出成型时需要注意的事项。     

挤出成型模具对烧结多孔砖和多孔砌块质量的影响

成型是烧结多孔砖和多孔砌块生产工艺的关键环节,模具的优劣对砖坯质量起到至关重要的影响。文中就成型模具对烧结多孔砖和多孔砌块质量的影响进行了阐述,对模具设计、加工中应注意的关键环节,如模具材料、结构设计、机械加工到耐磨处理等提出了意见与建议。     

不同几何尺寸纤维对混凝土力学性能的影响

选用不同几何尺寸的微细钢纤维、普通钢纤维、碳纤维,研究了它们对混凝土力学性能的影响。结果表明,增强作用按微细钢纤维、普通钢纤维、碳纤维次序递减;增韧作用按普通钢纤维、微细钢纤维、碳纤维次序递减。荷载与挠度曲线表明,碳纤维裂前增强与增韧作用优于微细钢纤维和普通钢纤维。     

挤出形状/尺寸对3D打印混凝土力学性能的影响

为了揭示3D打印挤出形状和尺寸对成型混凝土性能的影响机制,对比了模具成型、同挤出流量条件下不同挤出形状（三角形、方形和圆形）成型、同挤出形状条件下不同挤出尺寸成型、同挤出形状和同尺寸下不同打印条排列成型的混凝土断面形态、力学性能和空间孔隙分布,分析了不同挤出形状和尺寸条件下打印试件的层/条缺陷特征,探讨了打印试件孔隙率与其力学性能的对应关系.结果表明：层间和条间缺陷会显著影响打印试件的密实度,在同挤出流量条件下,由于层/条间的压紧作用,挤出形状呈三角形的打印试件具有最少的层间缺陷和最佳的力学性能;同形状的打印试件随着挤出尺寸的增大,其缺陷降低、力学性能提高;在挤出形状和尺寸均不变的情况下,打印口交错排列可提升打印试件力学性能13%～47%.     

对空心砖成型模具设计中几个主要问题的探讨

在空心砖生产中，除原料性能及原料处理对成型有重要影响外，在装备上影响成型的还有两个很重要的因素：一是挤出机的性能，主要指标包括挤出压力、真空度、最终压缩长度、转速及绞刀的结构参数；二是挤出成型的模具，包括机头、机口、芯具等。有关挤出机性能参数的影响，《砖瓦》杂志已有很多文章介绍，在此不再赘述。对于定型的挤出机，成型模具设计的合理与否，对空心砖裂纹及变形、外观尺寸、产量等影响很大，     

烧结砖成型工艺中硬塑挤出成型解析之我见

1 引言 烧结砖瓦工艺的出现已有二三千年的历史,也就是我们通常讲的秦砖汉瓦,但采用螺旋挤出机制砖生产工艺还不足二百年的历史,我国机制砖工艺的出现大约在20世纪初叶,且对挤出机的要求都不高,此种状况一直延续到20世纪80年代。     

塑料平开窗型材的几何尺寸及配合尺寸

总结了国内部分普通平开窗及三密封平开窗型材的几何尺寸及配合尺寸,并对平开窗型材的几何尺寸及配合尺寸的作用进行了详细的介绍。     

粉煤灰形态对高掺量粉煤灰烧结砖挤出成型工艺的影响

研究粉煤灰形态对粉煤灰掺量在70％以上的高掺量粉煤灰烧结砖挤出成型工艺的影响。指出由于粉煤灰的形态效应，致使利用挤出成型法生产高掺量粉煤灰烧结多孔砖出现挤出成型难度大、挤出压力高、成型水分不易控制和泥缸发热等弊病，是高掺量粉煤灰烧结多孔砖生产线普遍存在产量低、合格率低、掺灰率低和经济效益低的重要原因，并提出相应建议。     

The influence of geometry on the strength of shear wall panels in light steel construction

This paper investigated the potential benefits of using aerospace design methodologies in the new forms of lightweight dwelling construction which have received growing attention in recent years. The structural efficiency of new types of shear wall panels of various plan-form geometries are investigated, along with comparisons with the more usual rectangular type. The paper also discusses the likely benefits to the construction industry of adopting panels of this type when used in combination with recent developments in cold pressing and press-joining.     

LES study of the influence of the nose shape and yaw angles on flow structures around trains

Large-eddy simulation (LES) is made of the flow around a generic train model at two different yaw angles of 90^° and 35^°. The Reynolds numbers, based on the freestream velocity and the height of the train, are 3×10⁵ and 3.7×10⁵ for the yaw angles of 90^° and 35^°, respectively. The primary objective is to investigate the influence of the nose shape and yaw angles on the flow structures and the train aerodynamics. Both the time-averaged and instantaneous flows are explored. In the case of the 90^° yaw angle, the LES results show that the influence of the three-dimensional flow from the nose of the train on the time-averaged wake flow is limited to a region of a length of 3.5 train heights from the tip of the nose in the direction of the length of the train. The instantaneous flow shows an unsteady vortex shedding due to the shear layer instabilities on the periphery of the recirculation region and the exterior flow. In the case of the 35^° yaw angle, weak vortex shedding is found in the wake. Instead, unstable vortices are found in the lower part of the recirculation region. These vortices detach from and reattach to the train surface in a regular fashion leaving disturbances on the train surface and hence affecting the aerodynamic coefficients. The influence of the shape of the nose on the flow structures is investigated by repeating the simulations at the 90^° yaw angle on a short nose model. The short nose model is identical to the long nose model whilst the length of its nose is half that of the long nose. The short-nose simulation shows highly unsteady and three-dimensional flow around the nose yielding more vortex structures in the wake. These structures result in a surface flow that differs from that in the long-nose train flow. They also influence the dominating frequencies that arise due to the shear layer instabilities.     

影响挤出机挤出效率的因素

我国砖瓦企业有8万家之多，广泛分布于全国各地，量大面广，每年消耗的电能据统计在600亿kWh左右，约占三峡水电站满负荷发电量的40％，电力消耗相当惊人，因此搞好砖瓦企业的节能降耗意义十分重大。而对大部分砖瓦企业而言，挤出机所消耗的电能约占到总电能消耗的40％～60％。为此本文重点就影响挤出机挤出效率的一些因素作一分析探讨。     

二次热定型工艺对尼龙精密挤出型材性能的影响

本文研究了二次热定型尺寸整理装置对尼龙挤出制品性能的影响。通过与未采用二次热定型尺寸整理装置的挤出制品比较发现：这种工艺可以显著改善尼龙制品的表面光滑度、机械性能和吸水性。因此，二次热定型尺寸整理工艺是一种有效的提高尼龙精密挤出性能的工艺方法，可以提高尼龙制品的使用价值和商业价值。     

基于Sagaseta理论的桩基挤土效应计算

在Sagaseta理论的基础上,推导了半无限介质中,局部土体收缩引起土体中任意一点的竖向位移和水平位移的柱面坐标的计算公式,并以实测试验数据验证了公式的合理性。     

The effect of flow and geometry on concurrent flame spread

Flame spread is an important parameter used in the evaluation of hazards for fire safety applications. The problem of understanding and modeling flame spread has been approached before, however new developments continue to challenge our current view of the subject, necessitating future research efforts in the field. In this review, the problem of flame spread will be revisited, with a particular emphasis on the effect of flow and geometry on concurrent flame spread over solid fuels. The majority of this research is based on that of the senior author, who has worked on wind-driven flame spread, inclined fire spread, flame spread through discrete fuels and the particular problem of wildland fires, where all of the above scenarios play an important role. Recent developments in these areas have improved our understanding of flame-spread processes and will be reviewed, and areas for future research will be highlighted.     

挤压机在铜排生产中的应用

简要介绍了铜排挤压的工艺特点和难点,以及高速牵引技术和大口径水封头在25MN铜排挤压机上的应用。     

The influence of water on the performance of concrete

The powerful and pervasive influence of water on the performance of Portland cement concrete begins with the removal of water from either moist or wet raw cement feed and ends with application of curing water. Heat of hydration is normalized by mass of water. Due to its low density, water content mass in fresh concrete translates to porosity in hardened concrete, affecting both strength and durability. Water-cement ratio is here interpreted in terms of average spacing between adjacent cement particles, and workability, air, shrinkage, and service life are normalized to water content. Mixture proportioning and control of water content in the field are addressed.     

谈建筑对城市发展的影响

城市，作为社会生活的集汇点，既表现为社会生活的共同性，又表现为社会文化背景的个体特殊性和复合性。所以才有了天津与广州的不同，北京与上海的不同，伦敦与纽约的不同。建筑，作为人类时刻与之相容共处的物质空间，有它不可分割的两面性，一是建筑的外剖形态，构成着城市大空间，在城市中以空间元素形式存在；二是建筑的内部使用空间为人类提供各种使用性质的（物质的、精神的）安全场所。建筑是为城市而存在的，不是城市为建筑而发展建筑是由于人类的生活需要（物质性的）而出现，并有很长一段历史是纯功能的。建筑的艺术是基于功能基…