滚轴式金属屈服耗能阻尼器数值模拟研究

桥梁用阻尼器通常吨位和变形需求巨大, 普通金属屈服耗能阻尼器难以满足其性能要求. 为此该文提出一种新型的滚轴式金属屈服耗能阻尼器, 并对其进行数值模拟研究. 该阻尼器由一块平直耗能钢板及一组可转动辊轴组成, 耗能钢板在辊轴之间穿过, 受辊轴挤压产生塑性变形, 从而耗散地震能量. 该文采用在大型通用有限元软件ABAQUS建立了滚轴阻尼器的模型, 通过该模型研究了辊轴个数以及辊轴间隙对阻尼器耗能性能的影响. 分析结果表明:该阻尼器耗能性能受辊轴间隙和辊轴个数控制, 通过合理的设计可以保证滚轴式金属屈服耗能阻尼器具备优良的变形能力和耗能能力. 该文还提出了该阻尼器的恢复力计算公式, 结合有限元仿真结果对计算公式进行了修正.     

基于有限元法的CTP成像滚筒及版材的数值仿真

利用有限元分析软件ANSYS建立CTP成像滚筒的几何模型与有限元模型,选择接触单元模拟版材和滚筒表面之间的关系,以滚筒本体、滚筒与版材组合以及对滚筒内部吸真空的3种组合下进行有限元静力分析,获得滚筒自身变形对版材影响的大小,以及滚筒内抽吸真空对版材和滚筒变形的影响。结果表明,3种情况下滚筒和版材的最大变形量及位置均有所不同。其中,吸真空组合分析说明,版材在与滚筒表面密合状态下变形情况随从滚筒,滚筒表面的导槽对版材变形会产生一定影响,真实反映了工作状态,研究结果可以为CTP成像滚筒的设计与优化提供理论依据。     

Contact finite element analysis of three- and four-point short-beam bending of unidirectional composites

Detailed finite element stress analysis of both three-point and four-point short-beam bending specimens of a unidirectional glass-fibre/epoxy composite has been carried out. Contact elements are used to calculate the actual contact stresses and contact length at the roller. This gives more realistic stress distributions than those based on assumed load distributions. If the material is assumed to be linear, a parabolic assumption for the shear stress distribution is good for large parts of the beam between the loading and supporting rollers. However, higher shear stresses arise locally in the vicinity of the rollers. Taking account of the real nonlinear shear response of the material significantly reduces the shear stresses in the specimens.     

新型滚动轴承结构参数对印刷压力的影响

目的 为优化印刷滚筒的挠曲变形,有效提升其支承性能,改善印刷滚筒的压力分布。方法 选择预负荷弹性复合圆柱滚子轴承作为变刚度印刷滚筒传动支承部件,基于等效刚度模型计算不同填充度预负荷弹性复合圆柱滚子轴承的刚度,分析预负荷弹性复合圆柱滚子轴承结构参数变化对刚度的影响,构建变刚度印刷滚筒支承系统力学模型,通过有限元仿真分析预负荷弹性复合圆柱滚子轴承刚度对变刚度印刷滚筒印刷压力的影响。结果 结果表明,随着滚动体填充度的增加,预负荷弹性复合圆柱滚子轴承的径向刚度减小,变刚度印刷滚筒挠曲变形不同程度增大,结合疲劳寿命角度综合考虑,选择填充度在45%~50%的预负荷弹性复合圆柱滚子轴承作为印刷滚筒的弹性支承,其最大挠曲变形量较普通圆柱滚子轴承平均下降了9.5%。结论 在保证了疲劳寿命的前提下,有效改善了印刷滚筒压力分布的均匀性,提升了印刷质量。     

Numerical prediction of optimum hollowness and material of hollow rollers under combined loading

Fatigue life investigations have been made for cylindrical hollow rollers in pure rolling contact. In addition to normal loading, the rollers have been subjected to tangential loading of 1/3rd the normal load value. Sufficient coefficient of friction has been used to ensure no slipping occurs. Two main models were built with different hollowness percentages to investigate the hollowness percentage that gives the longest fatigue life. The first model consists of two cylindrical rollers of same size, while the second model consists of two rollers of different sizes. Two cases have been studied, when both rollers are hollow and when only one roller is hollow. The stress distribution in the roller body and the resulting deformation has been investigated using the finite element package, ABAQUS. Then the Ioannides–Harris (IH) theory was used to predict the fatigue life of the hollow rollers in pure rolling contact. Investigations have been made for five different materials, CVD 52100, Carburized steel, VIMVAR M50, M50NiL and Induction-hardened steel. It has been found that the optimum hollowness percentage with the longest fatigue life ranges is around 50%. Many factors affect the optimum hollowness percentage, like the kind of the material used for the cylindrical roller, whether the rollers in contact are of the same size or different size and whether the hollow roller is in contact with another hollow roller or in contact with solid roller.     

基于模具-制件相互作用的复合材料制件固化变形数值模型

针对复合材料制件在成型过程中的固化变形这一关键技术问题,通过在模具与复合材料制件之间引入剪切层的方法,建立了预测复合材料制件固化变形的解析计算模型和有限元仿真模型。剪切层的剪切模量用来衡量固化过程中模具与复合材料制件之间的相互作用,其数值大小通过与实验数据进行比对而得到。基于建立的固化变形模型,与文献中已有的实验结果进行了比较。结果表明:所建立的模型具有较高的可靠性。同时针对L型复合材料制件建立了三维有限元仿真模型,模型中除考虑材料各向异性和化学收缩效应以外,还将成型过程中模具与复合材料制件间的相互作用考虑在内。模拟结果表明:引入模具作用后L型零件的固化变形预测结果更加准确。      

实心和空心滚子结构阻尼的动态分析

结构阻尼是结构动力分析的重要参数之一,运用有限元方法研究实心和空心滚子在冲击载荷作用下的动态响应,并用傅立叶变换处理自由衰减中不同起点的两段相同长度的数据,求得滚子的结构阻尼,分析了滚子在不同冲击载荷、结构参数和材料参数下的阻尼特性。通过对滚子本身结构阻尼特性的研究,为轴承的振动研究提供了理论基础。     

Failure prediction on advanced grid stiffened composite cylinder under axial compression

Axial compression test is performed on an advanced grid stiffened (AGS) composite cylinder and the progress of failure is recorded by strain sensors and LVDT sensors. Failure prediction on the AGS composite cylinder is accomplished by a cyclical symmetrical finite element (FE) model which can improve the efficiency of numerical simulation. Numerical results and experimental data are compared to verify the proposed model. Various failure prediction criterion based on degradation principles for the AGS composite cylinder are employed to investigate the accuracy of the proposed model.     

对转圆柱滚子轴承动态特性分析

针对内外圈对转圆柱滚子轴承内部复杂的运动特性及相互作用力,通过分析轴承径向游隙的影响因素以及考虑滚子与滚道的接触变形和热效应对油膜厚度的影响,利用拟静力学法建立了轴承的分析模型,并采用NewtonRaphson法进行求解;同时,利用该模型对滚子打滑率进行计算,以验证所采用分析方法的正确性和可靠性。然后,进一步探讨了不同工况下对转圆柱滚子轴承内部组件的转速变化规律与接触特性。结果表明：滚子的自转转速、滚子与滚道的接触载荷均随径向载荷的增大而增大;内、外圈转速变化会使受载区滚子与滚道的接触载荷以一定的规律重新分配,且转速对最小油膜厚度的影响较径向载荷更为明显。研究结果可为对转圆柱滚子轴承的结构优化和生热机理分析提供理论依据。     

Numerical modeling of composite laminated cylinders in compression using a novel imperfections modeling method

The present study presents the finite element modeling procedure of two composite laminated cylinders exhibiting initial geometric imperfections. Using as input a set of experimental measurements of the cylinder geometry, the application of the skinning method leads to the analytical representation of the cylinder imperfect internal, external and middle surfaces. A finite element mesh is then easily constructed over these surfaces. The results of the analysis are in very good agreement with the experimental strains and buckling load measurements and are used to estimate the knockdown effect of the imperfections on the cylinder buckling behaviour. They are also compared to results obtained by other simpler finite element models, in an effort to evaluate the accuracy of various modeling simplifications.     

Finite element analysis of deformation and fracture of an exploded gas cylinder

This paper presents the finite element simulations of deformation and fracture of a gas cylinder which catastrophically failed as a result of an accidental explosion. The results of a previous detailed investigation of this incident indicated that detonation of a low-pressure oxygen-rich mixture of hydrogen and oxygen was the cause of the cylinder failure. In the current study, the finite element method was used to provide a more realistic modeling of geometry, material behavior, and boundary conditions of the cylinder. The overall transient dynamic response of the cylinder to gaseous detonation loading was studied using the ANSYS/LS-DYNA V10 package and the crack growth simulations were performed using the WARP3D-R15 research code. The crack growth analyses were performed using interface cohesive elements. The finite element results were validated using analytical solutions and data collected from the remains of the cylinder. The simulations clearly showed that the stresses caused by the assumed loading profile were indeed capable of creating local ruptures at the actual crack initiation sites. It was also shown that the self-similar growth of the initial axial crack in the main body of the cylinder was a fatigue-type incremental growth governed by the structural waves. The subsequent cyclic bulging of the crack flaps and the resultant crack curving and branching were also simulated.     

Numerical-analytical method for 3D dynamics study of spirally orthotropic multilayer cylinders

Based on the combination of the Fourier series expansions of variables with respect to the angular coordinate and a two-dimensional Wilkins algorithm, a numerical analytical method is developed to study the three-dimensional non-axisymmetric dynamics of multilayer thick-walled elastic spirally orthotropic cylinders of finite length. Verification of the proposed method is performed based on the comparison of the results with those obtained using the computational kernel of the LS-DYNA combined with the ANSYS/ED (an educational version of ANSYS finite element software). Some features of the dynamic behavior of a two-layer spirally reinforced cylinder under internal pulse loading produced by concentrated explosive charges are studied numerically.     

模具对复合材料层合板固化成型影响的数值分析

针对复合材料层合结构与模具在固化工艺中的相互作用进行研究以提高制备精度。考虑摩擦力和粘结力在模具和制件接触界面间的共同作用,改进一种复合材料层合结构固化应变及应力情况的数值计算模型并与已有实验结果进行比较。引入弹簧单元建立固化工艺有限元模型,并对解析模型进行验证。最后通过解析模型对固化变形的影响因素进行探究。结果表明:所建立的解析预报模型具有较高的计算精度及一定的实用性;考虑模具作用的有限元模型可以更好地对层合板的变形趋势进行预报和分析。通过解析模型探究发现层合板长度、模具材料和表面情况均会对固化过程中的层间滑移产生影响,对工艺条件制定具有更好的指导意义。      

预紧扁挤压筒内孔变形的研究

 扁挤压筒内层套壁厚变化大，过盈装配后使内腔发生不均匀变形而超过挤压筒规定的尺寸精度，给后续修模工作带来不便。因此，从扁挤压筒的结构改进着手，考虑几何相似性，采用外形呈椭圆状的扁挤压筒内层结构代替外形呈圆形的内层结构，应用ANSYS有限元分析软件，对两种受预紧作用的双层扁挤压筒分别进行数值模拟，研究其内孔变形规律，并用物理实验加以验证。结果表明：与采用圆形的内层结构相比，采用椭圆形状的内层结构其内孔变形量在整个圆周上分布较均匀，这为扁挤压筒修模工作带来了方便，同时也使模具的制造精度得到提高。     

Development of guide rollers using electroplated carbon fiber-epoxy composite for thin polymer film processing

Since thin polymer films can not sustain the large tension generated from the rotational inertia of a guide roller during start and stop periods of film processing and can be easily damaged by the rough surface of the guide roller, the guide roller should have low rotational inertia, low friction coefficient, high bending stiffness and fine surfaces.

The carbon fiber-epoxy composite material electroplated with chromium has excellent properties for the structure of the guide roller due to its high specific modulus and high damping, which reduces induced vibrations.

In this paper, the design and manufacturing methods as well as the static, dynamic and frictional characteristics of the carbon fiber-epoxy composite rollers electroplated with chromium were investigated using analytical and experimental methods to improve the performance of the high speed guide roller.     

柔性压辊拉形方式及其夹钳对板材成形的影响

为提高大型板类件拉形精度,介绍了传统整体夹钳拉形机的特点,提出了新型柔性压辊拉形原理.以球形件为例,分别对两种夹钳结构的拉伸成形过程建立有限元模型,并进行数值模拟,对比分析了两种夹钳结构作用下的成形结果.研究表明:柔性压辊拉形方式所得的成形件,其应力、应变分布均匀,成形质量较整体夹钳方式明显提高;而采用传统整体夹钳所成形的部件,其局部应力集中现象相对严重.利用柔性压辊拉形理论,分别对采用平板式结构夹钳和拉延筋式结构夹钳成形球形件的过程建立有限元模型并进行模拟分析,根据板材拉形过程的流动理论,对比分析两种夹持方式下板材的流动状态.研究发现:采用拉延筋式夹钳进行拉伸成形,处于夹钳中的板材流动效果较好;而利用平板式夹钳的成形过程中,板材流动量较小.实验验证结果与模拟结果趋势一致.     

Continuous flexible forming of three-dimensional surface parts using bendable rollers

A novel idea to form three-dimensional (3D) sheet metal parts using three bendable rollers is presented. It can realize a continuous flexible forming of sheet metal. The forming principle is introduced and forming equipment with three bendable rollers has been developed. The bendable roller with shape-adjusting device is designed based on a flexible shaft of steel wires. Some experiments were performed and typical 3D surface parts were formed. The experiments show that the transversal spine of 3D part is determined by the bended shape of the bendable rollers, and the longitudinal spine of the 3D part is determined by the relative displacement among the top roller and the two bottom rollers. The technology of forming 3D surface sheet metal using bendable rollers can produce 3D surface parts in a rapid and economical way.     

大型厚壁筒体斜插弯管结构焊接变形及其演变数值模拟

基于ANSYS有限元软件,建立了大型厚壁结构焊接变形有限元计算模型,分析了壁厚125mm的筒体斜插弯管接头焊接时小弯管与厚壁筒体间相对距离、筒体圆度变化及接头的位移演变过程.结果表明:小弯管位移以及厚壁筒体两侧圆周上的圆度改变在焊接与冷却过程中呈相反状态,而厚壁筒体两端的圆度变化率也有着明显差异;坡口下端最终会产生相对...     

A micromechanical analysis to predict the cord-rubber composite properties

Both three- and two-dimensional generalized plane strain finite element analyses based on a micromechanics approach were carried out to investigate the linear and nonlinear effective composite properties as well as the stress fields. A unit cell model of cord-rubber composite subjected to different loadings was studied to predict the effective composite properties. The numerical results of effective composite properties obtained from 2D and 3D finite element analyses were compared with experimental data and other finite element results available in the literature. The effects of rubber material nonlinearity and large deformation on the effective composite properties and interface stress distributions are presented and discussed.     

Exact stiffness matrix of mono-symmetric composite I-beams with arbitrary lamination

The exact stiffness matrix, based on the simultaneous solution of the ordinary differential equations, for the static analysis of mono-symmetric arbitrarily laminated composite I-beams is presented herein. For this, a general thin-walled composite beam theory with arbitrary lamination including torsional warping is developed by introducing Vlasov’s assumption. The equilibrium equations and force–deformation relations are derived from energy principles. The explicit expressions for displacement parameters are then derived using the displacement state vector consisting of 14 displacement parameters, and the exact stiffness matrix is determined using the force–deformation relations. In addition, the analytical solutions for symmetrically laminated composite beams with various boundary conditions are derived as a special case. Finally, a finite element procedure based on Hermitian interpolation polynomial is developed. To demonstrate the validity and the accuracy of this study, the numerical solutions are presented and compared with the analytical solutions and the finite element results using the Hermitian beam elements and ABAQUS’s shell element.