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1.
为模拟地震作用时杆件在变动轴力和双向弯曲的耦合特点,基于简化纤维模型的多弹簧单元模型近年被广泛应用。本文作者在相关论文中提出了考虑剪切变形弹塑性刚度影响的多弹簧模型空间梁柱单元,杆件的计算模拟精度除了取决于单元模型之外,还决定于两个重要参数:弹簧位置及个数布置、塑性区长度,本文将针对其进行参数分析并提出合理建议取值。本文最后还提出了模拟杆件残余应力的合理弹簧布置方式。  相似文献   

2.
基于多弹簧模型的空间梁柱单元(Ⅱ):参数分析   总被引:1,自引:0,他引:1  
为模拟地震作用时杆件在变动轴力和双向弯曲的耦合特点,基于简化纤维模型的多弹簧单元模型近年被广泛应用.本文作者在相关论文中提出了考虑剪切变形弹塑性刚度影响的多弹簧模型空间梁柱单元,杆件的计算模拟精度除了取决于单元模型之外,还决定于两个重要参数:弹簧位置及个数布置、塑性区长度,本文将针对其进行参数分析并提出合理建议取值.本文最后还提出了模拟杆件残余应力的合理弹簧布置方式.  相似文献   

3.
在概念设计阶段,车身碰撞安全性能评价是一个难点问题,需要详细的结构模型,本文基于塑性铰理论提出采用梁单元简化模型对框架车身进行概念设计阶段的耐撞性评估和优化设计方法。首先,介绍了关于箱型截面薄壁梁弯曲特性研究的理论模型与计算过程,接着赋予梁单元塑性铰的特性,模拟薄壁梁变形,再对框架车身进行了碰撞仿真。将仿真结果与详细模型对比,以分析简化模型的精度及可靠性。最后,以此为基础对框架车身进行耐撞性优化。结果表明,该简化模型易于创建,且有较高的精度,可用于概念设计阶段梁结构的设计工作。  相似文献   

4.
针对组合空腹夹层板桥的刚度计算,基于实体单元模型的参数化分析结果,提出了采用刚度放大系数来修正杆系模型结果的实用方法。推导了考虑剪切变形的简支钢空腹梁的等代抗弯刚度,并乘以刚度放大系数来分析混凝土板对结构的影响;与已有试验进行对比,验证壳-实体有限元建模方法的正确性,进一步分析了混凝土板和钢空腹梁截面参数对刚度放大系数的影响规律。结果表明:混凝土板厚度,钢空腹梁的高度、网格尺寸、上(下)肋高度及腹板厚度对刚度放大系数的影响最大;限定6个参数的取值范围得到的4 050个壳-实体有限元模型,涵盖了组合空腹夹层板桥实际设计中的所有可能条件,拟合出了刚度放大系数的计算公式。  相似文献   

5.
针对正交各向异性织物,本文提出了一种含附加节点的三角形弹簧质点模型.通过冗余自由度的引入和缩聚,能够实现有限元模型和弹簧质点模型三角形单元刚度矩阵的精确相等;据此,针对一般正交各向异性材料常数和单元形状,推导出弹簧质点模型中弹簧刚度系数及附加节点位置的解析表达式,有效解决了传统弹簧质点模型在正交各向异性织物仿真中存在的计算精度不高、弹簧参数选取随意等缺陷;并进一步完善了基于弹簧质点模型的柔性织物空间变形算法.数值模拟表明本文提出的弹簧质点模型和变形算法在进行织物仿真计算时,具有精度好、通用性强等优点.  相似文献   

6.
以2010年上海世博会园区预制预应力综合管廊工程为背景, 基于内力平衡和变形协调条件, 并考虑接头拼缝变形形态、预应力筋伸长和遇水膨胀橡胶条弹性模量的影响, 提出了包含抗 弯刚度计算模型和抗弯承载力计算模型的采用预应力筋连接的预制预应力综合管廊接头设计 计算方法. 与现有试验结果的对比分析表明, 该方法的计算结果与试验结果吻合良 好. 该文的主要研究成果已成功应用于2010年上海世博会园区预制预应力综合管廊工程.  相似文献   

7.
针对构造上正交各向异性凹凸板等效刚度的研究问题,考虑经典弹性薄板理论和凹凸板的几何周期特性,划分出了以凸起为中心的典型单元,首先研究了典型单元的刚度特性,再通过刚度组合方法得到了凹凸板的等效弯曲刚度;然后以四边简支正交各向异性凹凸板为例,基于经典薄板理论中纳维二重三角级数推广到正交各向异性板的解,利用本文的等效刚度公式分别计算了在集中载荷作用下板的挠度和其自身的固有频率。计算结果与ANSYS有限元的模拟结果进行对比,理论计算与有限元模拟结果一致,验证了本文等效解析方法的合理性和精确性。最后讨论了凹凸板的各项尺寸参数对刚度等效精度的影响,并对其原因进行了分析。本文给出的等效刚度解析方法便于工程应用,尤其在应对大规模凹凸板刚度求解中具有计算简便的优点,研究结果对凹凸板静力学和动力学的研究以及实际工程应用具有重要的指导意义。  相似文献   

8.
动力调谐陀螺仪挠性接头的等刚度设计   总被引:2,自引:0,他引:2  
本文讨论了动力调谐陀螺仪挠性接头的等刚度设计,导出了双平衡环动调陀螺挠性接头轴向刚度和径向刚度的计算公式。通过分析计算,给出了满足等刚度要求的内、外平衡环接头细颈的有关参数尺寸。  相似文献   

9.
针对参数化结构系统的响应极值问题,提出了一种适用于快速分析结构静态响应极值的计算方法。该方法在有限元模型基础上,利用减基法原理建立减缩的优化模型,并结合遗传算法快速、准确地获取结构在测点处的静态响应极值,同时,为了更贴近工程应用,在建立优化模型和设计优化步骤时,考虑了求解多测点情况下的最大静态响应极值。算例分析和结果比较,表明该方法在保证响应极值求解精度的同时,具有极大的时效性。  相似文献   

10.
胶焊复合连接技术兼具胶接和点焊的优点,它因提高结构强度和刚度而使车辆轻量化成为可能.以胶接理论为基础,考虑了被粘体剪切应变,将焊点视为大剪切弹性模量胶粘剂,胶层和焊点沿其厚度方向的剪应力不变,建立了胶焊单搭拉剪接头的线弹性应力解析模型.在应力模型基础上,将接头各组成部分看作是独立承载的拉伸和剪切弹簧单元,得到了其刚度解析模型.应力模型中的正应力和剪应力与有限元解吻合得较好,证明理论模型正确,参数研究中确定了影响胶焊单搭接头应力分布特征的关键耦合参数.  相似文献   

11.
界面连接刚度参数辨识的子结构分析法   总被引:2,自引:0,他引:2  
以试验模态参数为基础,提出一种通过特征方程反问题辨识子结构界面连接刚度参数的子结构分析法。新方法以子结构动柔度矩阵特征方程为基础,建立求解界面结点内力和位移的方程,从而由子结构内部结点可测自由度上的位移用广义逆理论估计界面结点内力和位移。并通过迭代修正内部结点可测自由度上的试验值,以提高界面内力和位移的估计精度。最后通过连接子结构刚度矩阵建立的平衡方程求解相应的刚度参数。文中以太阳电池阵板间铰链副刚度参数辨识为例,将铰链副简化为两端结点各有6个自由度的弹簧连接元,考虑到自由度之间的耦合,推导了连接元的刚度矩阵。用上述方法辨识了铰链副6个自由度的刚度参数,得到满意的辨识结果。  相似文献   

12.
对包含几何误差的机械结合面进行离散化,离散后的微表面的基准平面高度满足结合面几何误差分布.每个微表面内,微凸体的高度只受粗糙度的影响.基于接触理论建立了微表面的法向刚度模型,通过对微表面模型集成获得了结合面的法向刚度模型.通过对所建模型的数值仿真,揭示了结合面法向刚度与间隙的非线性关系,几何误差的幅值和波长对法向刚度的影响以及非线性刚度对结合面振动特性的影响.计算结果表明:法向刚度随着间隙的减少而迅速增加,几何误差会导致结合面宏观上的局部接触和应力集中;在相同干涉量下,法向刚度随着几何误差幅值的增加而增加,但与结合面的波长没有关系;非线性刚度会导致结合面固有频率的下降和振动位移的不对称.  相似文献   

13.
针对碳酸盐岩中化学爆炸地震勘探激发地震波能量弱、频率高、信噪比低的现状,为对炮孔装药结构提出合理的改进措施,建立了耦合与不耦合装药孔壁爆炸载荷及透射波能量的计算模型,并借助MATLAB编程计算得到解析解.同时在灰岩场地进行了装药不耦合系数Kd对地震波能量影响的现场实验,应用基于功率谱的能量分析方法对实验数据进行了分析....  相似文献   

14.
This study is concerned with the motion and displacement of points on branches of a bio-inspired sympodial tree-like structure of a different hierarchy. First, displacements of points of a sympodial-like tree are recorded in pull-and-release experiments to get a qualitative insight into their behaviour. Then, a sympodial-type structure is analyzed, starting from its trunk, along a first-order branch and along an external and internal second-order branch. Given the fact that each point on branches performs in-plane vibration, their corresponding mechanical model consists of two orthogonal springs of unknown directions and unknown stiffness coefficients. Their directions actually correspond to the principal axes, which are obtained for the first time in the analytical form in terms of system’s geometrical and material parameters. The additional novelty lies in demonstrating how the position of their principal axes changes along each branch. Extreme displacements along principal axes are obtained as well, defining the ellipse of displacement for each point on branches of different order and position. The advantages of branched structures with respect to T-shaped structures that are commonly used in engineering are discussed and emphasized.  相似文献   

15.
The present paper analytically investigates the adhesive behavior of power-law graded elastic solids under a combined action of external normal loading and a substrate stretch-induced mismatch strain with the effect of mode-mixity taken into account. A plane strain non-slipping model, a plane strain non-coupling model and an axisymmetric non-coupling model have been analyzed, respectively. Our results show that under a finite normal force, the equilibrium of the adhesive system may lost its stability at a critical value of mismatch strain, which significantly depends on both the graded material constants and the degree of mode-mixity. This indicates that the strongest or weakest adhesion strength under substrate stretching can be achieved by designing the physical constants of the adhesive system appropriately. These results provide a theoretical foundation for novel applications of functional graded materials in adhesion systems.  相似文献   

16.
A discrete element method (DEM) called particle flow code (PFC2D) was used to construct a model for Brazilian disc splitting test in the present study. Based on the experimental results of intact Brazilian disc of rock-like material, a set of micro-parameters in PFC2D that reflected the macro-mechanical behavior of rock-like materials were obtained. And then PFC2D was used to simulate Brazilian splitting test for jointed rock mass specimens and specimen containing a central straight notch. The effect of joint angle and notch angle on the tensile strength and failure mode of jointed rock specimens was detailed analyzed. In order to reveal the meso-mechanical mechanism of crack coalescence, displacement trend lines were applied to analyze the displacement evolution during the crack initiation and propagation. The investigated conclusions can be described as follows. (1) The tensile strength of jointed rock mass disc specimen is dependent to the joint angle. As the joint angle increases, the tensile strength of jointed rock specimen takes on a nonlinear variance. (2) The tensile strength of jointed rock mass disc specimen containing a central straight notch distributes as a function of both joint angle and notch angle. (3) Three major failure modes, i.e., pure tensile failure, shear failure and mixed tension and shear failure mode are observed in jointed rock mass disc specimens under Brazilian test. (4) The notch angle roles on crack initiation and and joint angle play important propagation characteristics of jointed rock mass disc specimen containing a central straight notch under Brazilian test.  相似文献   

17.
18.
机器人关节位移及几何参数误差是导致位姿出现误差的主要原因,对二者进行高精度标定可提高机器人的绝对精度.传统标定方法的精度受机器人位姿的影响,且需多次实验.本文提出一种基于多点动态捕捉测量的标定方法,可通过单次实验,同时标定串联机器人的关节位移和几何参数.首先基于多点动捕测量获取机器人各连杆上靶标点的3D坐标,结合罗德里格斯变换实现关节位移的求解.其次结合机器人运动学模型和坐标转换关系,实现几何参数误差小量的标定.对方程线性化处理以提高计算效率,并用最小二乘法降低噪声对结果的影响.最后通过对6自由度串联机器人进行仿真,验证了该标定方法的可行性.  相似文献   

19.
The effects of adhesive thickness, adhesive type and scarf angle, which are determined as the main control parameters by the dimensional analysis, on the mechanical properties of a scarf adhesive joint (SJ) subjected to uniaxial tensile loading are examined using a mixed-mode cohesive zone model (CZM) with a bilinear shape to govern the interface separation. Particularly, the adhesive-dependence of the vital cohesive parameters of CZM, which mainly include initial stiffness, total fracture energy and separation strength, is introduced emphatically. The numerical results demonstrate that the ultimate tensile loading increases as the adhesive thickness decreases. Cross the ultimate tension, the joint loses the load-bearing capacity when adopting the brittle adhesive but sustains partial load-bearing capacity while selecting the ductile adhesive. In addition, for the joint with the ductile adhesive, the maximum applied displacement until the complete failure of it is directly proportional to the adhesive thickness, which is different from the case using the brittle adhesive. Taking the combination of the ultimate loading and applied displacement into account, failure energy is employed to evaluate the joint performances. The results show that the failure energy of the joint with the brittle adhesive increases as the adhesive thickness decreases. Conversely, the situation of the joint using the ductile adhesive is vice versa. Moreover, the effect of the adhesive thickness becomes more noticeable with decreasing the scarf angle owing to the variation of the proportion of each component of the mixed-mode. Furthermore, all the characteristic parameters (the ultimate tensile loading, the maximum applied displacement and the failure energy) that adopted to describe the performances of SJ increase as the scarf angle decreases. Finally, the numerical method employed in this study is validated by comparing with existing experimental results.  相似文献   

20.
A new model is put forward to bound the effective elastic moduli of composites with ellipsoidal inclusions. In the present paper, transition layer for each ellipsoidal inclusion is introduced to make the trial displacement field for the upper bound and the trial stress field for the lower bound satisfy the continuous interface conditions which are absolutely necessary for the application of variational principles. According to the principles of minimum potential energy and minimum complementary energy, the upper and lower bounds on the effective elastic moduli of composites with ellipsoidal inclusions are rigorously derived. The effects of the distribution and geometric parameters of ellipsoidal inclusions on the bounds of the effective elastic moduli are analyzed in details. The present upper and lower bounds are still finite when the bulk and shear moduli of ellipsoidal inclusions tend to infinity and zero, respectively. It should be mentioned that the present method is simple and needs not calculate the complex integrals of multi-point correlation functions. Meanwhile, the present paper provides an entirely different way to bound the effective elastic moduli of composites with ellipsoidal inclusions, which can be developed to obtain a series of bounds by taking different trial displacement and stress fields.  相似文献   

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