管状带式输送机在线纠扭托辊的研究与应用

管状带式输送机是一种新型环保的散状物料连续输送设备,在运行过程中受各种因素影响,头、尾过渡段经常会跑偏,管状段经常会扭转,常规停机调偏纠扭方法已不能胜任复杂路线长距离管带机稳定运行的要求。为适应市场发展趋势,设计人员分析了管带机扭转原因,结合纠扭基本原理及常规纠扭方法,新开发出一种在线(不停机)纠扭托辊并投入项目应用。     

捻因数对涤纶混纺纱强伸性能的影响

以混纺质量比60∶20∶20纺制10种捻因数的涤纶-高强度维纶-苎麻纤维混纺纱,测试了成纱断裂强力和断裂伸长率指标。结果表明:随着捻因数的增大,断裂强力和断裂伸长率都呈现出先增大后减小的趋势,断裂强力最大值出现在捻因数为420时,断裂伸长率最大值出现在捻因数为410时。     

尼龙束捻度对水泥砂浆界面粘结的影响

通过织物拔出试验、抗折强度试验和扫描电镜对水泥基体微观破坏形貌的分析，研究了织物中尼龙束捻度对其增韧水泥砂浆界面粘结的影响。研究结果表明：存在着1个尼龙束捻度范围，在该范围内，捻度的增加有助于复合材料的界面粘结，且界面粘结强度随之提高；超出这一范围，捻度的增加反而不利于复合材料的界面粘结，界面粘结强度随之下降。     

Comparison and Analysis of Twist Pitch Length Test Methods for ITER Nb3Sn and NbTi Strands

国际热核聚变反应堆ITER磁体采用的Nb3Sn及NbTi超导线为多丝扭绞结构。作为超导线设计和应用的重要参数,股线扭距及扭转方向必需满足ITER要求,并且该性能参数须进行复验。根据ITER PA要求,股线的扭距大小为15 mm ± 2 mm,扭转方向为右向。超导线扭距及扭转方向测试可以通过在一小段直的样品上判断其超导丝分布规律或者其超导丝的角度得到。这里描述和比较了多种不同的测试方法。对不同方法的测试精度,不确定度以及可行度进行了分析,同时提出了针对ITER超导股线扭距复验的推荐方法。     

标准麻花钻三维建模研究

根据锥后刀面标准麻花钻直线刃的数学方程求得其螺旋槽曲面参数方程及截形参数方程,根据该截形参数方程,借助Matlab软件的数据处理功能,计算得到标准麻花钻截形曲线上的数据离散点集。将此点集导入到UG软件中,利用UG软件拟合出标准麻花钻截形曲线,生成锥后刀面标准麻花钻钻体。最后,选择合适的锥后刀面标准麻花钻国标刃磨参数,用UG软件得到其后刀面。在建立锥后刀面标准麻花钻三维模型的基础上,本文还针对"翘尾"现象给出了一种用UG软件分析的方法。     

残影不良分析及改善对策研究

通过对大量残影不良样品进行分析,找到了残影不良产生的原因,并基于分析结果设计了改善残影的实验。通过分析发现:残影不良产生的原因是彩膜侧像素与黑矩阵之间的段差过大,在摩擦工程时段差过大区域形成了摩擦弱区,摩擦弱区内的液晶分子配向较弱,导致不良产生。为降低残影不良进行实验,结果显示:在彩膜侧加覆盖层可以有效降低残影不良的发生率,但不适用于量产;通过采用高预倾角的配向膜材料,同时控制配向膜工程到摩擦工程的时间,可使残影不良发生率由28.2%降低至0.2%,为企业的稳定高效生产奠定了基础。     

Study on spiral wall thickness unevenness of thin- walled tubes rolled by Assel rolling mill

In view of the internal thread defect of thin- walled tubes rolled by Assel 3- roll skew rolling mill, Assel cross- rolling process of X20Cr13 steel tube with typical specification of ??160mm??6. 5mm was numerically simulated by using 3D finite element analysis software Simufact. The influences of different mandrel movement modes, feeding angles and rolling strip profiles on the depth of internal thread were studied. The results show that the depth of the internal thread of steel tube rolled by the full floating mandrel is the most shallow, the second is that of the fixed mandrel and that of the pull mandrel is worst, and it will be gradually deepened when the feed angle increases; the hyperbolic rolling strip is more conducive to controlling the internal thread depth of the rolled tube. Under the condition of hyperbolic rolling strip, the amount of twist deformation of the rolled tube in the rolling process is about 35% smaller than that of the straight rolling strip.     

Polymer spherulites: A critical review

Polymeric and non-polymeric materials often crystallize as spherulites when crystallized from viscous melts or solutions at large undercooling. The essential component of a spherulite is fibrillar crystals that grow in predominantly radial directions and branch irregularly. We review the growth, branching and twisting of crystals in the light of theoretical and experimental advances of the last decade, while maintaining an appreciation for historical context.The crucial role of self-generated fields ahead of the crystal–melt interface is developed. Pressure gradients from volume contraction have been treated, as well as impurity gradients ahead of a growing crystal; fibril width W is predicted and found to be proportional to δ^1/2, where the diffusion length δ = D/G, the quotient of diffusivity and growth rate, conveys the extent of the field gradient. Ribbon-like spherulite radii grow at a constant rate under diffusion-coupled interface control.Non-crystallographic branching is required to maintain the volume occupied by fibrillar crystals as the spherulite radius increases. Topological giant screw dislocations and induced nucleation at cilia tethered to crystals are observed mechanisms leading to branching normal to the wide dimension of lamellar crystals; but the relative importance of each of these is not yet established. Repetitive tip splitting by kinetic interface instability has been suggested as a branching mechanism in the wide dimension of lamellar crystals.Larger molecular mass reduces the spherulite growth rate, more so at low undercoolings, for reasons that remain unresolved. Miscible diluents often profoundly reduce G by lowering both thermodynamic driving force and local transport dynamics that govern the secondary nucleation rate. Spherulite blend morphology is linked to the competition between radial growth rate G and diffusivity D of the diluent, expressed as the diffusion length δ.Polymer crystals in which chain helices all have the same sense show banded spherulites, as do crystals in which the chain axes are not perpendicular to the basal surfaces. Recent analyses with optical birefringence and X-ray micro-diffraction support the presence of helicoidally twisted ribbons, although other structural arrangements have sometimes been revealed by microscopy. Assessments of twist directions in spherulites of chiral polymers point to unbalanced basal surface stress as the source of twisting, although a general mechanical analysis is lacking. Another twisting model employs regular arrays of isochiral giant screw dislocations; results are mixed for this model.     

捻系数和毛羽值与棉纱强力的相关性分析

通过测试得到环锭纺棉纱的捻度、毛羽值和断裂强力的数据。对数据进行回归分析，结果显示：棉纱的捻系数和毛羽值对断裂强力的影响显著；而且毛羽值与断裂强力之间的关系可以用三次项模型描述。     

Experimental determination of torsion and shear properties of sandwich panels and laminated composites by the plate twist test

A recently developed sandwich plate twist test is employed here for determination of the transverse shear modulus of the core and twist stiffness (D₆₆) of a sandwich panel consisting of a soft (H45 PVC foam) core and glass/vinylester face sheets. The shear modulus of the H45 PVC foam core extracted from the twist test was in good agreement with shear modulus obtained from ASTM plate shear testing of the foam core. D₆₆ values obtained from the sandwich twist test were in good agreement with predictions from classical laminated plate theory. In addition, the twist test was used to determine the in-plane shear modulus of glass/vinylester laminates isolated and as face sheets in sandwich panels with a stiff (plywood) core. The in-plane shear modulus of the face sheets, isolated and as part of a sandwich panel, was in good agreement with shear modulus determined using the Iosipescu shear test. The results point to the potential of the twist test to determine both in-plane and out-of-plane shear moduli of the constituents of a sandwich structure, as well as D₆₆.