关于龙滩水电站碾压混凝土坝的抗剪断强度问题

本文就龙滩水电站碾压混凝土坝的抗剪断强度进行了叙述，认为所提出各项指标是合理的，但要满足这些指标必须采取一定的措施，以确保大坝的安全度     

热处理工艺对截齿钎焊接头强度的影响

为获得采煤机用截齿钎焊接头的优良性能，作者研究了钎焊后热处理工艺参数对钎缝抗剪强度的影响。试验表明，高温区停留时间在保证钎焊时钎料充分熔化的前提下越短越好；冷却速度对接头的强度有较大影响，一般情况下，钎焊后由880℃冷却到200℃的时间应控制在5～20min之间；回火温度在350～450℃之间抗剪强度有低谷区。截齿钎焊采用HL105钎料，配以合适的钎剂能获得较理想的接头性能。     

改性脲醛树脂胶粘剂的研究

主要利用混合改性剂，改进生产工艺以及施胶时加入填料等方法研究脲醛树脂胶粘剂的游离甲醛含量，剪切强度、耐水性等问题，得到低毒，综合性能良好的胶粘剂。     

In situ visualization of drop deformation,erosion, and breakup in high viscosity ratio polymeric systems under high shearing stress conditions

In this paper, deformation and breakup under simple shear of single molten polymer drops in a polymer matrix were investigated. Flow visualization was carried out in a Couette‐Flow apparatus under relatively high shear rates and temperatures up to 230°C. Drop/Matrix combinations were composed of polystyrene drops of 0.5–0.6 mm in diameter in polyethylene matrix, and ethylene–propylene copolymer drops of approximately the same size in polypropylene matrix. The deformation and breakup processes were studied under steady state and time‐dependent shearing conditions. Either for steady state or time‐dependant shearing conditions, drop elasticity generated at relatively high shear rates helped the drops to align perpendicular to the flow direction, i.e., parallel to vorticity axis. Also, the most striking non‐Newtonian effects for the high viscosity ratio systems were the surface erosion and the drop splitting mechanisms. The particles eroded off the main droplet surface were very fine, in the range of 10–50 μm, and led to a significant reduction in main drop size before its final breakup. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2582–2591, 2006     

螺杆挤压机混合能力的分析

分析螺槽中熔体的流动状态 ,运用加权平均总应变来评价螺杆挤压机的混合能力 ,进而提出提高混合能力的途径。对于单螺纹螺杆 ,稍长的计量段 ,稍浅的计量段螺槽及较高的螺杆转速 ,有利于混合作用 ;开发新型螺杆 ,如犁钉分流混合螺杆 ;研制高效混合型螺杆挤压机 ,如球窝型高效混合型螺杆挤压机     

电子剪切散斑技术在木材无损检测中的应用

复合板材及木制品等表面或内部的缺陷对材料性能有很大影响,如何快速准确地对其进行无损检测,并判断缺陷的位置大小是很有意义的.针对松木板试件,通过预置表面和内部隐藏缺陷来近似模拟实际缺陷情况,提出一种基于剪切散斑干涉技术的木材无损检测技术新方法,实现了对松木试件的无损检测.在表面缺陷的检测中讨论了剪切量对结果的影响,利用像素标定的方法,得到直径为6、5、3mm的缺陷信息;在内部隐藏缺陷检测中,借助热加载技术同时引入相移技术使剪切散斑检测技术不仅具有非接触、全场实时检测等特点,而且完成对内部隐藏近表面缺陷的定量无损检测.整个检测过程光路简单,实时快速,实验结果与实际情况符合较好.     

基于微缺陷累计成核数序列的岩石边坡滑移带尺度增长预测

岩石边坡滑移带是一个微损伤聚集带,每一个微损伤实际为一个微缺陷成核,因此,存在累计微缺陷成核数与滑移带尺度增长的对应关系.这个关系以裂纹系统的最大尺度cmax作为未知量,需要确定的参数有材料颗粒尺度δ,微裂纹尺-频分布分维数Dc,裂纹表面粗糙度分维数Ds,微裂纹总数Nd以及微缺陷成核累计数Nd.通过对边坡数值模拟微裂纹系统的统计分析,发现该尺度增长模型的预测值与实测值吻合较好.微缺陷成核数序列与声发射序列有较多的相似性,因此,研究结果为预测边坡内部裂纹增长提供了参考.     

薄带钢纵、横剪切生产线简介

介绍了横切机组和纵剪机组主要工艺特点、关键设备，及机组电气控制系统的主要特点。     

Three-dimensional spinal motion and risk of low back injury during sheep shearing

Sheep shearers are known to work in sustained flexed postures and have a high prevalence of low back pain (LBP). As sustained posture and spinal movement asymmetry under substantial loads are known risk factors for back injury our aim was to describe the 3D spinal movement of shearers while working. We hypothesised that thoraco-lumbar and lumbo-sacral movement would be tri-axial, asymmetric, and task specific. Sufficient retro-reflective markers were placed on the trunk of 12 shearers to define thoraco-lumbar and lumbo-sacral 3D motion during three tasks. Thoraco-lumbar movement consistently involved flexion, left lateral flexion, and right rotation. Lumbo-sacral movement consistently involved right lateral flexion in flexion with minimal rotation. Shearers therefore work in sustained spinal flexion where concurrent, asymmetric spinal movements into both lateral flexion and rotation occur. These asymmetric movements combined with repetitive loading may be risk factors leading to the high incidence of LBP in this occupational group.     

金属表面环氧漆漆膜拉伸剪切强度的测定

借鉴国标胶粘剂拉伸剪切强度测定方法测定了阳极、阴极环氧电泳漆与环氧涂料在底材为铝合金及钢材上漆膜的拉伸剪切强度，在铝件及钢铁件表面上阳极电泳漆漆膜的拉伸剪切强度为11．60MPa及17．91MPa，阴极电泳漆漆膜分别为17．60MPa及23．20MPa，喷涂环氧漆膜为7．93MPa 及13．40MPa，并介绍了测定试验中的实际操作经验和技术细节。