塔式起重机的金属结构设计与分析

基于有限元技术,利用有限元分析软件ANSYS对塔式起重机金属结构进行有限元建模分析,对建模中的结构简化、塔机载荷选择等进行了探讨和分析,并在此基础上对塔式起重机进行有限元求解分析,从分析中得到关于塔机强度、刚度、稳定性等信息。     

以ANSYS为平台的塔式起重机臂架有限元分析与关键技术研究

为了解决在传统设计方法下塔式起重机试制样机成本高、设计效率低等弊端,应用CAE软件ANSYS对QTZ40型塔式起重机的臂架进行建模与有限元分析,通过对臂架的强度校核和各阶模态的计算,验证了该型塔式起重机设计方案的合理性,也证实了有限元分析法的可行性.总结了建模时的等效简化处理以及约束、载荷施加等关键技术的经验,从而为塔式起重机产品的设计、生产和制造提供理论依据.     

基于ANSYS的塔式起重机臂架有限元参数化建模与分析

针对塔式起重机在有限元分析过程中建模工作量大的问题，将参数化思想引入有限元分析过程中，采用有限元参数化分析文本自动生成技术，以通用编程语言为基础编制程序，根据输入参数自动生成有限元建模分析所需的参数化文件，进行结构建模与分析，并以塔机臂架结构为例说明方法的可行性。     

基于Ansys的塔式起重机振动模态分析

塔式起重机的振动会引起较大的动态应力,模态分析就是确定其结构的振动特性,也是其他动力学的基础。以FTZ5510塔式起重机为研究对象,研究了其建模方法,建立了其整体结构的有限元模型,并以结构进行模态分析来计算结构的固有振动特性,确定结构的固有频率以及振型,为研究该型塔机的其他动力响应提供了依据。     

塔式起重机静态及模态安全性分析

采用有限元分析软件以某上回转塔式起重机为例,建立了塔式起重机整机结构的有限元模型,并对其进行了静力及模态分析,确定塔式起重机静态下的最大应力值及所在位置,并给出了其5阶固有频率和振型,对其结构及减震设计具有现实的指导意义.     

多载荷工况下塔式起重机的强度、刚度和安全裕度

基于有限元参数化建模技术,运用Ansys中的APDL程序语言编写了塔式起重机整机金属结构命令流,在自重、起升载荷、风载荷等共同作用下选择3种危险工况,进行结构强度、刚度有限元分析,得到塔式起重机结构最大应力发生的位置和变形最大出现的位置。对整机结构稳定性进行了研究,得到不同工况下的临界极限载荷,来确定塔式起重机不同工况下的安全裕度。     

基于APDL的塔式起重机有限元参数化建模与分析

为了快速高效地建立大量塔式起重机的有限元模型,结合C#语言和ANSYS提供的二次开发工具APDL开发了一种面向塔机对象的有限元参数化建模程序,并利用该程序对塔机的疲劳寿命进行了分析。分析结果表明,该程序能够提高有限元模型的建模效率,为塔机的安全评估提供了合理的参考依据,并为类似问题的解决提供了一条新途径。     

基于Ansys的塔式起重机结构有限元分析

利用有限元分析软件Ansys,对JC7050塔式起重机桁架结构进行有限元分析,得出其结构在典型工况下每个杆件的强度、刚度、整机及局部的稳定性,对塔式起重机的设计、寿命预测和结构优化提供一定的依据和数据支持。     

单螺栓预紧力对塔身顶端位移的影响研究

为研究单螺栓预紧力变化对塔式起重机顶端位移的影响,实现塔式起重机的在线安全评估和检测,文中基于多尺度建模策略,应用Ansys有限元软件对塔式起重机进行APDL参数化建模,具体包括对塔身联接螺栓部位采用实体单元精细建模,其余部位建立宏观尺度的梁杆模型,并采用创建刚性区域法装配成整机模型;通过对起重臂旋转和单螺栓预紧力变化...     

塔式起重机整体结构有限元分析

运用大型有限元软件ANSYS对某塔式起重机整体结构进行了静力分析和模态分析，并对建模的方法、技巧及注意问题进行了讨论。在静力分析的基础上获得了结构的应力分布，并将计算结果与实际测试结果进行了比较；通过模态分析获得结构的固有频率和振型，结合塔机实际情况，分析了前6阶模态的振型。     

考虑模型偏差的结构动力学模型修正

针对结构有限元模型修正后仍可能存在模型偏差的问题,提出用待修正参数的不确定性来表征模型偏差的有限元模型修正方法。首先,基于响应面方法识别得到待修正参数的最优值,并通过计算结果与试验结果比较获得模型偏差;然后,基于响应面模型并结合灵敏度分析计算得到模型偏差对待修正参数的影响,从而得到考虑模型偏差后待修正参数的区间;最后,通过一个悬臂梁工程实例的模型修正,验证了笔者所提出方法的可行性。结果表明,考虑模型偏差的修正可以提高模型可靠性。     

基于Evans-Johnson流变模型粘塑性流体弹流润滑的数值计算

推导了基于Evans-Johnson流变模型的雷诺方程,并进行了数值求解,将数值计算结果与基于理想粘塑性流变模型的数值结果进行了比较.结果表明,基于Evans-Johnson流变模型和基于理想粘塑性流变模型所得到的油膜压力分布没有本质的区别,但基于二者的油膜厚度却有很大的不同;在大滑滚比的工况下,由前者所得的中心膜厚度比由后者所得的中心膜厚度低,表明在考虑润滑剂粘塑性的弹流润滑研究中,选用合适的润滑剂流变模型很重要。     

基于特征模型的柴油机机体有限元结构分析

这里以某柴油机机体为研究对象,建立了机体的特征实体模型,对其进行了三维有限元自由振动模态分析和有限元强度分析,为增压改进提供了理论依据。在同一实体模型的基础上,以高精度的振动模态计算模型来验证实体模型简化的合理程度是一种既经济又快捷的手段。     

A two-phase damping model on tube bundles subjected to two-phase cross-flow

An analytical model is developed to estimate the two-phase damping ratio for upward cross-flow through horizontal tube bundles. The present model is formulated based on Feenstra’s model (2000) for void fraction and various models (homogeneous, Levy, Martinelli-Nelson and Marchaterre) for two-phase friction multiplier. The analytical results of drag coefficient on a cylinder and two-phase Euler number are compared with the experimental results by Sim-Mureithi (2013). The correlation factor between frictional pressure drop and the hydraulic drag coefficient is evaluated by considering the experimental results. The two-phase damping ratios given by the analytical model are compared with existing experimental results. The model based on Marchaterre’s model is suitable for air-water mixture, whereas the Martinelli-Nelson’s model is suitable for steam-water and Freon mixtures. The two-phase damping ratio is independent of pitch mass flux for air-water mixture, but is more or less influenced by the mass flux for steam-water/Freon (134) mixtures. The two-phase damping ratios given by the present model agree well with experimental results for a wide range of pitch mass ratio, quality, and p/d ratios.     

Designing safe job rotation schedules based upon workers’ skills

In this article a new model is developed to deal with safe skill-based job rotation scheduling (SSJRS). A multiobjective integer programming model is presented to determine job rotation schedules which considers two objective functions simultaneously. The first objective function aims to minimize maximum occupational noise exposure injuries, and the second one is designed to minimize the potential of worker’s low back injuries. The potential of worker low back injuries and the noise exposure levels of each job are assessed by job severity index (JSI) and daily noise dosage (DND), respectively. Thresholds for JSI and DND are also considered in the model. Finally, this model is solved as a single objective model, using the LP-metric method. To verify the efficiency of SSJRS, test problems are solved for each objective of the model separately, and the results are compared with the results from the SSJRS model. It has been found that the results from the SSJRS model dominate the results from single objective models.     

MODEL IMPROVEMENT AND EXPERIMENT VALIDATION OF PNEUMATIC ARTIFICIAL MUSCLES

According to the deficiency of the present model of pneumatic artificial muscles (PAM), a serial model is built up based on the PAM's essential working principle with the elastic theory, it is validated by the quasi-static and dynamic experiment results, which are gained from two experiment systems. The experiment results and the simulation results illustrate that the serial model has made a great success compared with Chou's model, which can describe the force characteristics of PAM more precisely. A compensation item considering the braid's elasticity and the coulomb damp is attached to the serial model based on the analysis of the experiment results. The dynamic experiment proves that the viscous damp of the PAM could be ignored in order to simplify the model of PAM. Finally, an improved serial model of PAM is obtained.     

Stress propagation through jointed beam systems using finite element theory

The propagation of disturbances through connected beams is considered using finite element theory: the Timoshenko beam model is considered since it exhibits the correct propagation behaviour in single beams. The joint is examined and three joint models are introduced into the model, namely the rigid block model, the filament model and finally a flexible joint model. The numerical results so obtained compare favourably with experimental results produced at UMIST.     

汽车碰撞过程中计及安全带约束的人体动力学响应分析

采用基于Euler绳索模型的理论 ,提出了一种新的带有滑移特性的安全带模型。采用多体动力学理论Kane Huston方法 ,进行了计及安全带约束的人体动力学建模及响应的分析 ,并与实验结果进行了比较 ,得到了较一致的结果 ,验证了模型的正确性 ,从而为进行汽车碰撞过程分析提供了有用的工具     

基于OrCAD／PSpice的MCT仿真研究

MCT是一种新型的电力电子开关器件,本文利用PSpice中的器件模型和电路模型建立了一个MCT的组合模型,并用多瞬态分析法提取了该模型的参数。文中还用该模型进行了MCT开关特性的仿真试验,将仿真的结果与实际的MCT的开关试验的结果相对照,两者基本相符。     

Efficient updating of PDE models for metrology

We describe a model selection methodology for partial differential equation (PDE) based models and show the results of applying it to a test problem. A methodology for comparing and choosing simplified models is of benefit to the model development process in metrology. It is assumed that the computational aim is not only to solve the model to obtain the results that the metrologist requires, but also to ensure that the model is no more complex than necessary to achieve this, and that results can be obtained in a reasonable time using the available computing resources. The advantage of the proposed method is that it avoids the need to solve directly the underlying complex model. We present the results of comparisons of four models of the test problem and identify the further work needed to improve the approach and to extend it to a wider range of problems.