The Effects of the Longitudinal Axis of Loading upon Bending, Shear and Torsion of a Thin-Walled Cantilever Channel Beam

Three aluminium channel sections of US standard extruded dimension are mounted as cantilevers with x-axis symmetry. The flexural bending and shear that arise with applied axial torsion are each considered theoretically and numerically in terms of two longitudinal axes of loading not coincident with the shear centre. In particular, the warping displacements, stiffness and stress distributions are calculated for torsion applied to longitudinal axes passing through the section’s centroid and its web centre. The stress conversions derived from each action are superimposed to reveal a net sectional stress distribution. Therein, the influence of the axis position upon the net axial and shear stress distributions is established compared to previous results for each beam when loading is referred to a flexural axis through the shear centre. Within the net stress analysis is, it is shown how the constraint to free warping presented by the end fixing modifies the axial stress. The latter can be identified with the action of a ‘bimoment’ upon each thin-walled section.

Theory of Flexural Shear, Bending and Torsion for a Thin-Walled Beam of Open Section

Aspects of the general Vlasov theory are examined separately as applied to a thin-walled channel section cantilever beam under free-end end loading. In particular, the flexural bending and shear that arise under transverse shear and axial torsional loading are each considered theoretically. These analyses involve the location of the shear centre at which transverse shear forces when applied do not produce torsion. This centre, when taken to be coincident with the centre of twist implies an equivalent reciprocal behaviour. That is, an axial torsion applied concentric with the shear centre will twist but not bend the beam. The respective bending and shear stress conversions are derived for each action applied to three aluminium alloy extruded channel sections mounted as cantilevers with a horizontal principal axis of symmetry. Bending and shear are considered more generally for other thin-walled sections when the transverse loading axes at the shear centre are not parallel to the section = s centroidal axes of principal second moments of area. The fixing at one end of the cantilever modifies the St Venant free angular twist and the free warping displacement. It is shown from the Wagner-Kappus torsion theory how the end constrained warping generates an axial stress distribution that varies with the length and across the cross-section for an axial torsion applied to the shear centre. It should be mentioned here for wider applications and validation of the Vlasov theory that attendant papers are to consider in detail bending and torsional loadings applied to other axes through each of the centroid and the web centre. Therein, both bending and twisting arise from transverse shear and axial torsion applied to each position being displaced from the shear centre. Here, the influence of the axis position upon the net axial and shear stress distributions is to be established. That is, the net axial stress from axial torsional loading is identified with the sum of axial stress due to bending and axial stress arising from constrained warping displacements at the fixing. The net shear stress distribution overlays the distributions from axial torsion and that from flexural shear under transverse loading. Both arise when transverse forces are displaced from the shear centre.

基于“板-梁理论”单轴对称FGM工字形梁组合扭转

针对目前功能梯度材料(Functionally Graded Materials,FGM)工字形截面梁为研究对象的研究较少,本研究以“板-梁理论”为基础,以上翼缘为矩形实体单轴对称的工字形截面梁为对象,展开组合扭转理论研究。基于“板-梁理论”,推导总应变能方程,得到梁的翘曲刚度和自由扭转刚度,然后通过外力势能公式和总应变能公式逐步推导得出总势能表达式。在此基础上,利用能量变分模型和微分方程模型,结合边界条件,推导出梁端部最大扭转角计算公式,将求出的最大扭转角与ANSYS建立的有限元模型结果进行对比。误差最小为0.01%,误差最大为1.85%。本文推导了FGM沿宽度变化上翼缘为矩形实体单轴对称工字形梁的组合扭转总应变能表达式,给出了一端固定、一端自由边界条件下扭转角及最大扭转角的表达式,从而进一步验证“板-梁理论”的正确性。

塔中隆起奥陶系油气性质及运聚富集模式

以构造、断裂分布、生产动态以及地球化学等资料为基础,对塔中地区奥陶系油气性质与产能分布特征进行了分析,从油气充注、输导体系、构造与油气运聚关系等3个方面对油气富集因素进行了分析,并建立了成藏模式。研究结果表明:①塔中地区奥陶系原油以轻质原油为主,具有低密度、低黏度、低含硫的特征,密度为0.75~0.85 g/m^(3),油气藏气油比为119~82367 m^(3)/m^(3),多相态油气藏并存,且油气相态无明显边界;天然气干燥系数为0.70~0.98,天然气甲烷碳同位素为-35.7‰~-61.4‰,变化范围大;不同区域金刚烷指数(MDI)差异较大,为0.33~0.64;8个主要油气充注点具有原油密度低、气油比高、天然气甲烷同位素及MDI高的特征,沿走滑断裂带向南或远离断裂带方向密度变大,气油比、甲烷碳同位素及MDI均变小,不同区块气侵强度不同造成变化规律存在局部差异。②研究区油气分布格局主要受点状油气充注影响,8个油气充注点周缘油气井通常具有较高的产量,受储层发育规模影响会出现低产井,产能分布具有“北气南油”、“中间气、两边油”及“普遍富气、局部含油”3种类型;远离充注点的低产井及水井大范围分布。③研究区奥陶系油气富集模式为张扭性大断裂控制油气垂向充注,不整合面及走滑断裂控制油气的侧向调整,断裂破碎带叠加层间岩溶为油气聚集提供了储集空间,局部构造高部位及平台区为油气聚集有利指向区。

双排斜槽纵-扭复合振动压电超声换能器

为了提升纵-扭复合振动换能器的输出效率,该文研究了双排斜槽纵-扭复合振动压电超声换能器,其由一个夹心式压电超声换能器和一个带有双排斜槽的空心圆柱传振杆组成。给出双排斜槽纵-扭复合振动压电超声换能器的等效电路图,推导了输入阻抗和频率方程。基于有限元仿真软件分析了斜槽的排数和双排斜槽的倾角、间距、长度、宽度、深度和传振杆周向刻槽数量等几何形状对纵-扭复合振动压电超声换能器共振频率和输出端平均扭转量的影响。设计和加工了换能器,实验测试表明理论共振频率与实验结果吻合较好,双排斜槽纵-扭复合振动压电超声换能器可以有效提升输出端平均扭转量和纵向-扭转振动的比率。

Torsional超声乳化模式治疗硬核白内障

目的探讨Torsional超声乳化模式治疗硬核白内障的效果。方法将220例(285眼)行白内障超声乳化术的硬核白内障患者随机分为普通超声乳化模式组与Torsional超声乳化模式组,比较术中晶状体核乳化时间和灌注液用量,术后检查记录角膜内皮细胞丢失率、最佳矫正视力。结果普通模式组术中晶状体核乳化时间平均164s,Torsional模式组平均117s;灌注液用量普通模式组为93mL,Torsional模式组为41mL;2组比较差异均有统计学意义(P<0.05)。术后1周角膜内皮细胞丢失率Torsional模式组为11.8%,普通模式组为20.3%,差异有统计学意义(P<0.05)。术后第1天和第30天Torsional模式组平均最佳矫正视力为0.4和0.6,普通模式组为0.1和0.4。结论Torsional超声乳化模式治疗硬核白内障与普通超声乳化模式相比,可以减少超声乳化时间、灌注液用量,从而降低角膜内皮细胞的丢失率,提高术后视力效果。

p-torsion模的性质

给出了p-torsion模的定义,并利用同调的方法讨论了p-torsion模的性质,目的是找到p-torsion模构成torsion类的条件以及构造p-torsionfree类,并最终找到了一个p-torsionfree类与投射维类的关系。

Tor-torsion pair与弱整体维数

利用torsion pair的方法讨论了Tor-torsion pair的一些性质,目的是找到Tor-torsion pair与环R的弱整体维数之间的关系,并得到了一个很好的不等式关系.

环的相对于余遗传Torsion Theory的Jacobson根

本文推广了环论中拟正则左理想的概念，引入τ－拟正则左理想的概念，给出环的相对于余遗传Ｔｏｒｓｉｏｎｔｈｅｏｒｙ的Ｊａｃｏｂｓｏｎ根的元素刻划．

Influence of Microstructures and Textures on the Torsional Behavior of Pearlitic Wires

The microstructure, texture characteristics and torsion ability of two kinds of steel wires were investigated. The eutectoid steel wires were produced by hot and cold drawing with severe deformation. The torsinability of steel wires was measured under two cases, i.e. there exists either fiber texture or circular texture. The results showed that the torsional behavior of the steel wires was affected by their textures and microstructures. The {110}<110> circular texture weakened the torsion ability of the wires. The torsion fracture behavior of {110}<110> texture wires is related to the fact that only two slip systems were activated under simple shear strain deformation.

Global Dynamic Characteristic of Nonlinear Torsional Vibration System under Harmonically Excitation

Torsional vibration generally causes serious instability and damage problems in many rotating machinery parts. The global dynamic characteristic of nonlinear torsional vibration system with nonlinear rigidity and nonlinear friction force is investigated. On the basis of the generalized dissipation Lagrange＇s equation, the dynamics equation of nonlinear torsional vibration system is deduced. The bifurcation and chaotic motion in the system subjected to an external harmonic excitation is studied by theoretical analysis and numerical simulation. The stability of unperturbed system is analyzed by using the stability theory of equilibrium positions of Hamiltonian systems. The criterion of existence of chaos phenomena under a periodic perturbation is given by means of Melnikov＇s method. It is shown that the existence of homoclinic and heteroclinic orbits in the unperturbed system implies chaos arising from breaking of homoclinic or heteroclinic orbits under perturbation. The validity of the result is checked numerically. Periodic doubling bifurcation route to chaos, quasi-periodic route to chaos, intermittency route to chaos are found to occur due to the amplitude varying in some range. The evolution of system dynamic responses is demonstrated in detail by Poincare maps and bifurcation diagrams when the system undergoes a sequence of periodic doubling or quasi-periodic bifurcations to chaos. The conclusion can provide reference for deeply researching the dynamic behavior of mechanical drive systems.

Immunohistopathology of the contralateral testis of rats undergoing experimental torsion of the spermatic cord

Aim： To evaluate the immunohistopathological changes in the contralateral testis of rats after an experimental spermatic cord torsion. Methods： Male Sprague-Dawley rats of 45-50 days old were subjected to a 720° unilateral spermatic cord torsion for 10, 30 and 80 days （experimental group, E）, respectively or sham operation （control group, C）. Histopathology of the contralateral testis as well as germ cell apoptosis were studied using the Terminal Deoxynucleotidyl Transferase Biotin-dUTP Nick End Labeling （TUNEL） technique. The number of testicular lymphocytes, mast cells and macrophages, and the expression of tumor necrosis factor-α （TNF-α） and its receptor （TNFR1） in testicular cells of the contralateral testis were quantified by histochemistry and immunohistochemistry. TNF-α concentration in testicular fluid was determined by ELISA. Results： In the contralateral testis of rats from the E group, the maximal degree of damage of the germinal epithelium was seen 30 days after torsion. At this time we observed in the E group vs. the C group increases： （i） the number of testicular T-lymphocytes; （ii） the number of testicular mast cells and macrophages; （iii） the percentage of macrophages expressing TNF-α; （iv） TNF-α concentration in testicular fluid; （v） the number of apoptotic germ cells; and （vi） the number of TNFR1^＋ germ cells. Conclusion： Experimental spermatic cord torsion induces, in the contralateral testis, a focal damage of seminiferous tubules characterized by apoptosis and sloughing of germ cells. Results suggest humoral and cellular immune mediated testicular cell damage in which macrophages and mast cells seem to be involved in the induction of germ cell apoptosis through the TNF-α/TNFR1 system and in the modulation of the inflammatory process.

Torsional phenomena in 2008 great Wenchuan earthquake

It is well known that there are some torsional damages in earthquakes. In Taibai park, Jiangyou city, Sichuan province, most of the stone statues, which were placed upon the banisters of one zigzag bridge, exhibited different torsional phenomena in 2008 Wenchuan earthquake. This paper introduces the torsional phenomena of all the statues on the zigzag bridge firstly. Then one eccentric- ity model is established and the equivalent rotational accelerations are calculated in order to analyze the causes of the torsional damage. In addition, the torsional components are synthesized by using translation accelerations recorded at Jiangyou station in the Wenchuan earthquake. The results show that the equivalent rotational acceleration is larger than the synthesized rotational components, which sug- gests that the torsional phenomena of the statues on the zigzag bridge might mainly come from its eccentricity. The comparison between the estimated torsional component at Jiangyou and that presented by Trifunac shows that they are in the same order. The research im- plies that the torsional phenomena in earthquakes are very complicated, and not only caused by torsional motions.

Comparison of corneal endothelial changes following phacoemulsification with transversal and torsional phacoemulsification machines

AIM:To compare and evaluate the phacoemulsification parameters and postoperative endothelial cell changes of two different phacoemulsification machines, each with different modes, but also to assess the relationship between postoperative endothelial cell loss and the phacoemulsification parameters, as well as the other factors in both groups.METHODS:This prospective observational study was comprised of consecutive eligible cataract patients operated with phacoemulsification technique performed by the same surgeon using either a WHITESTAR Signature Ellips FX(transversal, group 1) or Infiniti OZil IP(torsional, group 2) machine.RESULTS:The study included 86 patients. Baseline characteristics in the groups were similar. The median nuclear sclerosis grade was 3(2-4) in the first group and2(2-4) in the second group(P =0.265). Both groups had similar phacoemulsification needle times(group 1: 60.63±36 s; group 2: 55.98±30 s; P =0.789). The percentage of endothelial cell loss 30 d after surgery ranged from 3% to15% with a median of 7% in group 1, and from 2% to13% with a median of 6% in group 2; however, there was no statistically significant difference between the groups(P =0.407). Hexagonality(P =0.794) and the coefficient of variation(CV; P =0.142) did not differ significantly between the groups before and 30 d after surgery. Asignificant positive correlation was found between the endothelial cell loss and nuclear sclerosis grade(group1: P 【0.001; group 2: P 【0.001) and between the endothelial cell loss and average phacoemulsification power(group 1: P =0.007; group 2: P =0.008).CONCLUSION:Both of these machines were efficient,with similar endothelial cell loss. This endothelial cell loss was related to the increased nuclear sclerosis grade and increased phacoemulsification power.

Coupled flapwise-chordwise-axial-torsional dynamic responses of rotating pre-twisted and inclined cantilever beams subject to the base excitation

A rotating pre-twisted and inclined cantilever beam model (RPICBM) with the flapwise-chordwise-axial-torsional coupling is established with the Hamilton principle and the finite element (FE) method. The effectiveness of the model is verified via comparisons with the literatures and the FE models in ANSYS. The effects of the setting and pre-twisted angles on the dynamic responses of the RPICBM are analyzed. The results show that:(i) the increase in the setting or pre-twisted angle results in the increases in the first-order flapwise and torsional frequencies while the decrease in the first-order chordwise frequency under rotating conditions;(ii) a positive/negative setting angle leads to a positive/negative constant component, while a positive/negative pre-twisted angle leads to a negative/positive constant component;(iii) when the rotation speed is non-zero, the pre-twisted angle or non-zero setting angle will result in the coupled flapwise-chordwiseaxial- torsional vibration of the RPICBM under axial base excitation.

Torsional vibration of a pipe pile in transversely isotropic saturated soil

This study considers the torsional vibration of a pipe pile in a transversely isotropic saturated soil layer. Based on Biot＇s poroelastic theory and the constitutive relations of the transversely isotropic medium, the dynamic governing equations of the outer and inner transversely isotropic saturated soil layers are derived. The Laplace transform is used to solve the governing equations of the outer and inner soil layers. The dynamic torsional response of the pipe pile in the frequency domain is derived utilizing 1D elastic theory and the continuous conditions at the interfaces between the pipe pile and the soils. The time domain solution is obtained by Fourier inverse transform. A parametric study is conducted to demonstrate the influence of the anisotropies of the outer and inner soil on the torsional dynamic response of the pipe pile.

Acute abdomen in pregnancy due to isolated Fallopian tube torsion: The laparoscopic treatment of a rare case

In the last years, operative laparoscopy became a standard approach in gynaecology and general surgery. Even in pregnancy its use is becoming more widely accepted. In fact, it offers advantages similar to those in no pregnant women, associated with good maternal and fetal outcomes. Around 0.2% of pregnant women require abdominal surgery. The most common indications of laparoscopy in pregnancy are cholelithiasis complications, appendicitis, persistent ovarian cyst and adnexal torsion. Authors describe a very rare case of acute abdomen due to isolated Fallopian tube torsion in a 24 th weeks pregnant woman, managed by laparoscopic salpingectomy.

Pushover analysis of asymmetric-plan buildings based on distribution of the combined modal story shear and torsional moment

A pushover procedure with a load pattern based on the height-wise distribution of the combined modal story shear and torsional moment is proposed to estimate the seismic response of 3D asymmetric-plan building frames. Contribution of the higher modes and torsional response of asymmetric-plan buildings are incorporated into the proposed load pattern. The proposed pushover method is a single-run procedure, which enables tracing the nonlinear response of the structure during the analysis and averts the elusiveness of conducting multiple pushover analyses. The proposed method has been used to estimate the response of two moment-resisting building frames with 9 and 20 stories. The obtained results indicate the appropriate accuracy and efficiency of the proposed procedure in estimating the trend of the drift profiles of the structures resulted from nonlinear time history analyses.

Sample size effect on the dynamic torsional behaviour of the 2A12 aluminium alloy

In order to investigate the effect of sample size on the dynamic torsional behaviour of the 2A12 aluminium alloy. In this paper, torsional split Hopkinson bar tests are conducted on this alloy with different sample dimensions. It is found that with the decreasing gauge length and thickness, the tested yield strength increases. However, the sample innerlouter diameter has little effect on the dynamic torsional behaviour. Based on the finite element method, the stress states in the alloy with different sample sizes are analysed. Due to the effect of stress concentration zone （SCZ）, the shorter sample has a higher yield stress. Furthermore, the stress distributes more uniformly in the thinner sample, which leads to the higher tested yield stress. According to the experimental and simulation analysis, some suggestions on choosing the sample size are given as well.