国产卧式电极挤压机同步剪切技术探讨

就国产电极挤压机如何实现同步剪切，结合上海碳素厂25MN卧式电极挤压机更新改造的具体实践，从理论和实践两个方面详细阐述了具有档架结构的卧式压机实现同步剪切理论上的可行性，针对同步剪切各相关系统中的不同问题，借鉴德国引进30MN挤压机有益经验逐一加以解决，最终使得卧式挤压机真正实现同步剪切功能。     

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     

木浆纤维素/NMMO·H_2O溶液的流变性能研究

以含水率13.7%的N-甲基吗啉-N-氧化物(NMMO)为溶剂溶解木浆纤维素形成溶液,采用红外光谱分析仪对木浆纤维素的溶解过程进行表征,并采用黏度计研究了木浆纤维素/NMMO·H2O溶液的流变性能。结果表明:木浆纤维素在NMMO中先溶胀后溶解,且可完全溶解;木浆纤维素/NMMO·H2O溶液的流动呈现切力变稀的假塑性流体特征;木浆纤维素质量分数为6%时,溶液的非牛顿流动特征明显,溶液的表观黏度(ηa)随木浆纤维素浓度的增加明显增加,随剪切速率(γ)及温度的上升而下降,当γ高于一定值即logγ大于1.3时,溶液的ηa不受温度的影响,只随γ的上升而下降,且剪切应力不随γ变化而变化,为恒定值。     

Preparation,Mechanical and Thermal Properties of Polyurethane/Nanosilica Composites via High Pressure Shearing Methods

Nanosilica particles were dispersed into polymer diols by high pressure shearing homogenizer (HPSH), then polyurethane nanocomposites were prepared via in-situ polymerization of diphenylmethane diisocyanate (MDI) and polymer diols. FTIR analysis indicated that the -NCO groups of MDI had reacted with the hydroxy on the surface of nanosilica during in-situ polymerization. TGA suggested that polyurethane/nanosilica composites obtained by in-situ polymerization had better thermal stability than pure polyurethane. Meanwhile, the tensile and dynamic mechanical properties of the samples prepared by HPSH were superior to those by directly ultrasonic dispersing nanosilica, accompanied by more homogeneous dispersion of nanosilica particles in the polymer matrix.     

纤维缠绕压力容器表面损伤试验研究

通过制作纤维缠绕标准容器试样,并对部分试样表面纤维制作人工损伤,与标准容器试样比较爆破压力,并进行有限元分析、研究其破坏机理,对强度影响程度进行评估。结果表明：表面纤维损伤会造成压力容器在应力水平较低情况下局部发生层间剪切破坏,损伤容器爆破强度平均值降低22．4％,损伤修复后的容器爆破强度降低12．2％。     

HRB400E钢筋混凝土梁柱边节点的抗剪性能

为研究配置HRB400E钢筋混凝土梁柱边节点的抗剪性能,以混凝土强度、水平纵筋锚固方式、梁纵筋配筋率为主要研究参数,采用正交试验法设计了9个试件并完成了梁柱边节点的抗剪试验。试验结果表明：试件多发生梁端弯曲和核心区剪切破坏,但采用弯折锚固方式可有效减少节点核心区裂缝数量;在本文3个研究参数中,混凝土强度对初裂时节点核心区剪切变形影响最大,混凝土强度等级越高初裂阶段的节点剪切变形角越小;水平纵筋锚固方式对极限状态时节点核心区剪切变形影响最大,当采用90°弯折锚固方式时节点的剪切变形角最小;梁纵筋配筋率对节点水平剪力影响最大,配筋率越大节点水平剪力越大。采用正交试验原理结合极差、方差数理统计理论对梁柱边节点抗剪性能影响参数进行分析可梳理出各因素的主次关系和变化趋势。     

黄土基岩接触面滑坡滑带土物理力学特性及微观结构

滑带土抗剪强度取值及微观结构特性对于边坡稳定及防治具有重要意义。以陕西延安地区二庄科滑坡为研究对象,通过剪切试验、扫描电镜及X射线衍射仪等,对典型黄土基岩接触面滑坡滑带土物理力学特性及微观结构进行研究;通过剪切试验得到不同含水率、不同干密度条件下滑带土的抗剪强度参数及其与含水率、干密度之间的相关性函数;通过研究其微观结构及矿物成分,分析了不同干密度、不同垂直压力条件下的土样微观结构。结果表明:随着含水率的减小和干密度的增加,土样的抗剪强度参数均有所提高;黏聚力与含水率呈负指数关系,内摩擦角与含水率呈负线性关系,黏聚力、内摩擦角分别与干密度呈正线性关系;随着垂直压力的增大,孔隙离散指数增大,颗粒离散指数、孔隙(颗粒)平均形态系数、孔隙(颗粒)定向概率熵及孔隙(颗粒)定向分维数均减小;随着干密度的增大,颗粒定向概率熵及颗粒定向分维数均增大。     

环氧树脂建筑结构胶粘剂增韧改性研究

采用改性环氧树脂和添加增强填料等方法,提高胶粘剂的力学性能,增强其柔韧性。通过对比试验得出了玻璃纤维作为填充剂在胶粘剂中的合理含量,为其在粘接领域的应用提供了基础数据．     

OCP增粘剂在南阳基础油的应用评价

通过对四种OCP增粘剂的剪切稳定性能、低温性能进行评价,综合考虑确定了南阳原油生产润滑油的增粘剂的种类。利用本研究成果生产的油品经长时间检验后,证明油品剪切稳定性能优越。     

Characterization of mechanically sheared edges of dual phase steels

In recent years advanced high strength steels (AHSS) received increased interest for light structures with improved performance, but they are often sensitive to edge cracking during sheet metal forming. In this study mechanically sheared edges were characterized for three dual phase steels (DP600, DP780 and DP980), sheared with three die clearances (5%t, 10%t, 15%t) and along rolling and transverse directions. Microstructures of the materials were provided first, and then the sheared edges were examined by optical microscopy and scanning electron microscopy that reveal the morphology and random feature of the sheared edges. A factorial analysis was performed to reveal the general trends of the processing parameters on four edge zones. A new strain measurement method was used for characterizing strain distribution in the sheared region, which shows the peak strain to be higher than 3. The strain quickly decreases from sheared edge to interior, leaving a shear-affected zone of about 500 μm or 31% of the thickness. The fracture processes and involved mechanisms were discussed.