Differential geometry properties of lines of curvature of parametric surfaces and their visualization

We present algorithms for computing the differential geometry properties of lines of curvature of parametric surfaces. We derive a unit tangent vector, curvature vector, binormal vector, torsion, and algorithms to evaluate their higher-order derivatives of lines of curvature of parametric surfaces. Among these quantities, it is shown that the curvature and its first derivative of the lines of curvature lend a hand for the formation of curved plates in shipbuilding. We also visualize the twist of lines of curvature, which enables us to observe how much the osculating plane of the line of curvature turns about the tangent vector.     

Torsion sensor based on two cascaded long period fiber gratings fabricated by CO2 laser pulse irradiation and HF etching technique respectively

A novel torsion sensor is proposed, which is composed of one long period fibre grating and one asymmetrically corrugated long period fibre grating based on the high-frequency CO₂ laser pulses technology and burning fibre coating and etching cladding technology, respectively. By combing the advantages of the two aforementioned elements, a sensitivity of 331.7 and 310.3 pm/(rad/m) towards clockwise and anticlockwise direction, respectively, is reached in the experiments.     

Effect of diet and fat content on the functional properties of thawed beef

The effect of animal diet (pasture versus grain) and fat content (1, 15 and 25%) on the functional properties and quality of beef stored for 8 months at −20 °C was determined. After storage, pasture-finished beef had significantly (P<0.001) less malondialdehyde than grain-finished. Grain-finished beef had a more vivid red colour than pasture-finished (P<0.01). The remaining functional properties determined in this study were not affected by diet. Protein solubility, emulsion activity index, and cooked batter torsion strain decreased and hue angle increased with increasing fat content. The solubility of total and sarcoplasmic proteins and cooked batter torsion stress and strain decreased (P<0.001) and hue angle increased (P<0.001) with storage time regardless of diet and fat content. It is concluded that there is not much difference in the functional properties of beef finished on pasture or grain. However, pasture-finished beef is more stable to lipid oxidation than the grain-finished, and hence may be more amenable to further processing.     

扭转机改造升级实践

介绍了ＮＮ—５０型扭转机改造的总体方案和实施过程，说明了光机电方案的优越性，指出了进一步改进的方法．     

Torsional shear strength behavior of advanced glass-ceramic sealants for SOFC/SOEC applications

Since reliable long term operation of SOFC and SOEC devices depends critically on the mechanical behavior of the sealant material, the current work focuses on the characterization of the shear strength by a torsion test of two different glass-ceramic sealants that are used to join Crofer22APU substrates in an application relevant configuration. The two glass-ceramic sealants differ in terms of characteristic temperatures and crystalline phases with possible impications on the joining behavior. Statistically identical shear stress values were measured at room temperature for joined hourglasses of different size with both sealants, thus confirming a size independence of the measured strength values. Experimental post-test examination results confirm that the interfaces play a strong role regarding the measured shear strength and provide important insights with respect to integration of metallic and glass-ceramic components in SOFC/SOEC stacks.     

Finite element optimization of sample geometry for measuring the torsional shear strength of glass/metal joints

Assessment of mechanical properties of glass/metal joints is a challenging process, especially when the application relevant conditions of the joints have to be considered in the test design. In this study, a finite element method (FEM) is implemented to analyze a torsional shear strength test designed for glass-ceramic/steel joints aiming towards solid oxide fuel/electrolysis cells application. Deviations from axial symmetry of the square flanges (ends) of respective hourglass-shaped specimens and also supporting and loading sockets of the test set-up are included in the model to simulate conditions close to reality. Undesirable tensile stress and also shear stress concentration appear at the outer edge of glass-ceramic layers, which are less for the hollow-full specimen. The simulation results show that for a specimen with either 9 mm thick square- or 6 mm thick triangular-flanges, locally enhanced tensile stresses almost disappear, resulting in a symmetric shear stress distribution. The difference between the analytically derived nominal shear strength and the real critical shear stress derived via simulation reduces with decreasing the fracture torque.     

垂直井眼中扭压载荷作用下管柱轴向稳定性分析

文章讨论了管柱垂直井眼中,考虑轴向压缩载荷、扭矩、管柱内外压力、摩擦力共同作用下的屈曲分析问题。运用能量法及变分原理得到了新的高阶非线性微分方程。同时能量法求解了考虑扭矩作用下管柱的临界载荷问题,推导出了新的临界载荷表达式,讨论了扭矩作用下对管柱临界载荷的影响。     

基于渐进损伤模型的机床复合材料传动轴扭转性能分析

利用考虑就地效应的Hashin失效准则和刚度非线性退化方法,并且引入Cohesive界面单元,采用ABAQUS有限元分析软件的子程序UMAT编写面内和层间渐进损伤模型,建立实体单元和Cohesive界面单元结合的实体模型,对纤维增强复合材料传动轴的扭转屈曲和后屈曲性能进行研究。利用模型对该项目试验结果进行验证,对某文献中的碳纤维复合材料轴进行有限元分析,并与试验数据进行比对,验证有限元模型的可靠性。结果表明：所建立的渐进损伤模型对拉伸载荷作用下的层合板失效强度的计算精度较高;压缩载荷作用下,利用该模型进行屈曲和后屈曲分析时的计算结果和试验结果吻合度较高;利用所提出的渐进损伤模型对碳纤维复合材料传动轴进行扭转屈曲和后屈曲失效分析,所得结果与试验结果吻合度较好。