Hydroforming Process Design Using Finite Element Simulation for a Vehicle Instrument Panel Support Frame

Tubular hydroforming has attracted increased attention in the vehicle industry recently. This paper covers a complete hydroforming process design for an instrum ent panel frame by finite element simulation using the explicit code LS-DYNA. The manufacturing process for the instrument panel frame consists of tube pre-be nding and final hydroforming. To accomplish hydroforming process design successf ully, a thorough investigation of proper combination of process parameters such as internal hydraulic pressure and axial feeding is carried out by finite element simulation to predict the tube wall thickness and shape. An optimized process parameter combination is obtained and verified by the instrument panel frame hyd roforming experiment. The experiment shows that designed process parameters can be used in real production through FEA simulation, but tubular thinned amplitu de by FEA is less than that with the experiment.

Frame-invariance in finite element formulations of geometrically exact rods

This article is concerned with finite element implementations of the three- dimensional geometrically exact rod. The special attention is paid to identifying the con- dition that ensures the frame invariance of the resulting discrete approximations. From the perspective of symmetry, this requirement is equivalent to the commutativity of the employed interpolation operator I with the action of the special Euclidean group SE（3）, or I is SE（3）-equivariant. This geometric criterion helps to clarify several subtle issues about the interpolation of finite rotation. It leads us to reexamine the finite element for- mulation first proposed by Simo in his work on energy-momentum conserving algorithms. That formulation is often mistakenly regarded as non-objective. However, we show that the obtained approximation is invariant under the superposed rigid body motions, and as a corollary, the objectivity of the continuum model is preserved. The key of this proof comes from the observation that since the numerical quadrature is used to compute the integrals, by storing the rotation field and its derivative at the Gauss points, the equiv- ariant conditions can be relaxed only at these points. Several numerical examples are presented to confirm the theoretical results and demonstrate the performance of this al- gorithm.

A Comparative Study on the Truck Frame Stiffness with Solid and Beam Element FEA Models

Truck frames should be designed and fabricated with enough rigidity to avoid excessive deflections. Finite element analysis (FEA) plays an important role in all stages of frame designs. While being accurate, 3D solid element FEA models are built upon frame configuration details which are not feasible in the preliminary design stage, partially because of limited available design data of frames and heavy computation costs. This research develops 1D beam element FEA models for simulating frame structures. In this paper, the CAD model of a truck frame is first created. The solid element FEA analysis, which is adopted as the baseline in this study, is subsequently conducted for the stiffness of the frame, Next, beam element FEA analysis is performed for validating the feasibility of the beam element FEA model by comparing the results from the solid and beam element FEA models. It is found that the beam element FEA model can predict the frame stiffness with acceptable accuracy and reduce the computation cost significantly.

A New Non-uniform Beam Element and Its Application to Buckling Analysis for Framed Structures

The non-uniform beam components are commonly used in engineering,while the method to analyze such component is not too satisfactory yet. A new non-uniform beam element with high precision was developed based on the non-linear analysis and the static condensation. Based on the interpolation theory, the displacement fields of the three-node non-uniform Euler-Bernoulli beam element were constructed at first: the quintic Hermite interpolation polynomial was used for the lateral displacement field and the quadratic Lagrange interpolation polynomial for the axial displacement field. Then,based on the basic assumptions of non-uniform Euler-Bernoulli beam whose section properties were continuously varying along its centroidal axis, the linear and geometric stiffness matrices of the three-node non-uniform beam element were derived according to the nonlinear finite element theory. Finally,the degrees of freedom ( DOFs) of the middle node of the element were eliminated using the static condensation method, and a new two-node non-uniform beam element including axial-force effect was obtained. The results indicate that each bar needs to be meshed with only one element could get a fairly accurate solution when it is applied to the stability analyses.

Framenet核心框架元素间关系研究

本文首先阐述了框架元素的类型:核心框架元素、外围框架元素和额外主题框架元素,然后再详细论述了Framenet中3种典型的核心框架元素关系:核心集关系、必要关系和排斥关系,并总结出继承关系的框架间核心框架元素关系的变化规律。

广义Frame的谱空间(英文)

本文在frame的范畴形式推广——广义frame上引进点、素元与谱空间的概念,并且证明任意广义frame都是完备、余完备的Cartesian闭范畴.进而说明一个广义frame上全体点与该广义frame上全体素元之间存在着范畴等价的关系,此关系不同于经典frame理论中相应的一一对应关系,并且讨论了广义Frame范畴与拓扑空间范畴之间的函子关系,最后,证明广义frame的谱空间是Sober空间。

Theoretical Research and Experimental Validation of Elastic Dynamic Load Spectra on Bogie Frame of High-speed Train

When a train runs at high speeds, the external exciting frequencies approach the natural frequencies of bogie critical components, thereby inducing strong elastic vibrations. The present international reliability test evaluation standard and design criteria of bogie frames are all based on the quasi-static deformation hypothesis. Structural fatigue damage generated by structural elastic vibrations has not yet been included. In this paper, theoretical research and experimental validation are done on elastic dynamic load spectra on bogie frame of high-speed train. The construction of the load series that correspond to elastic dynamic deformation modes is studied. The simplified form of the load series is obtained. A theory of simplified dynamic load–time histories is then deduced. Measured data from the Beijing–Shanghai Dedicated Passenger Line are introduced to derive the simplified dynamic load–time histories. The simplified dynamic discrete load spectra of bogie frame are established. Based on the damage consistency criterion and a genetic algorithm, damage consistency calibration of the simplified dynamic load spectra is finally performed. The computed result proves that the simplified load series is reasonable. The calibrated damage that corresponds to the elastic dynamic discrete load spectra can cover the actual damage at the operating conditions. The calibrated damage satisfies the safety requirement of damage consistency criterion for bogie frame. This research is helpful for investigating the standardized load spectra of bogie frame of high-speed train.

Light weight analysis of a skeleton vehicle frame using BS960 super-high-strength steel

Static strength finite element analysis was conducted to decrease the weight of a skeleton vehicle＇s frame. Results indicated that the maximum stress occurs on the front beam ＇s variable section area. Dynamic sensitivity analysis elucidated the relationship between the maximum stress and the thickness of a particular beam,e. g.,top,middle,and bottom beam. Displacement was analyzed by the key part that influenced the maximum stress. Finally,the new plan using BS960 super-high-strength beam steel and the preferred beam thickness was compared with the original plan. New combinations of beam thickness were introduced on the basis of different purposes; the maximum responding light w eight ratio was 21%.

Nonlinear Stability Analysis of Long Span Continuous Rigid Frame Bridge with Thin Wall High Piers

By utilizing the current finite element program ANSYS, two types of finite element models (FEM), the beam model (BM) and shell model (SM), are established for the nonlinear stability analysis of a practical rigid frame bridge—Longtanhe Great Bridge. In these analyses, geometrical and material nonlinearities are simultaneously taken into account. For geometrical nonlinearity, updated Lagrangian formulations are adopted to derive the tangent stiffness matrix. In order to simulate the nonlinear behavior of the plastic hinge of the piers, the multi lines spring element COMBIN39 is used in the SM while the bilinear rotational spring element COMBIN40 is employed in the BM. Numerical calculations show that satisfying results can be obtained in the stability analysis of the bridge when the double coupling nonlinearity effects are considered. In addition, the conclusion is significant for practical engineering.

A Simplified Approach to Analysis of High-Rise Frame Tube Structures

Based on finite element method and finite strip method, a simplified approach was presented to analyze high rise frame tube structures. The generalized strip element is introduced and then the generalized stiffness matrices for beam and column line are derived by using the displacement functions that describe the nodal displacements and displacement transforms. Furthermore, the formulas for the generalized stiffness matrix of generalized strip element and load arrays corresponding to the displacement parameters were developed. It is shown through a series of numerical computation that the nodal angular displacements at the same floor in a generalized strip element are approximately identical. A comparison of the finite element method and the finite strip method shows that the simplified approach not only is accurate, but also reduces the number of basic unknown quantities.

Independent continuous mapping for topological optimization of frame structures

Based on the Independent Continuous Mapping method （ICM）, a topological optimization model with continuous topological variables is built by introducing three filter functions for element weight, element allowable stress and element stiffness, which transform the 0-1 type discrete topological variables into continuous topological variables between 0 and 1. Two methods for the filter functions are adopted to avoid the structural singularity and recover falsely deleted elements： the weak material element method and the tiny section element method. Three criteria （no structural singularity, no violated constraints and no change of structural weight） are introduced to judge iteration convergence. These criteria allow finding an appropriate threshold by adjusting a discount factor in the iteration procedure. To improve the efficiency, the original optimization model is transformed into a dual problem according to the dual theory and solved in its dual space. By using MSC/Nastran as the structural solver and MSC/Patran as the developing platform, a topological optimization software of frame structures is accomplished. Numerical examples show that the ICM method is very efficient for the topological optimization of frame structures.

Fatigue Strength and Modal Analysis of Bogie Frame for DMUs Exported to Tunisia

The equivalent stress at key positions of Bogie Frame for DMUs Exported to Tunisia is obtained by using simulation analysis. The evaluation of static strength and fatigue strength is checked referring to UIC specification and Goodman sketch for welding materials. In addition, the modal analysis of the frame is made, and the vibrational modal of frame in given frequency domain is predetermined to evaluate the dynamical behavior of the frame in order to meet the dynamical design requirements. The results show that the key points of the calculated frame of the equivalent stress are less than allowable stress, and thus it could provide a theoretical foundation for the optimized design of frame structure and safety of industrial production.

Experimental Investigation of Progressive Collapse of Steel Frames

This paper reports two new tests conducted to augment available data highlighting the structural performance of multistory steel frames under progressive collapse. The investigated steel frames had different geometries, different boundary conditions, different collapse mechanisms, different damping ratios and different connections. Overall, the paper addresses how multistory frames would behave when subjected to local damage or loss of a main structural carrying element. The obtained results can form a data base for nonlinear finite element models. The deformations of the investigated steel frames and failure modes under progressive collapse were predicted from the finite element analysis, with detailed discussions presented.

Progressive Collapse of RC Frames Due to Heavy Impact Loads of Tsunami

Progressive collapse is a relatively rare event, as it requires both an abnormal loading to initiate the local damage and a structure that lacks adequate continuity, ductility and redundancy to resist the spread of damage. However, significant casualties can result when collapse occurs. Heavy impact loads due to tsunami against building can be one of the scenarios of progressive collapse during tsunami disaster. Since progressive collapse includes material and geometry nonlinearity during collapse propagation, in the present research capability of 2 models for the material nonlinearity in simulating actual behavior of structures during collapse is compared with recent experimental results of a Reinforced Concrete (RC) frame. The results demonstrate that a material nonlinearity model, that is based on the idealized component load-deformation behavior, is not a proper representation for the real behavior of structures during progressive collapse and is so conservative.

平衡车车架拓扑优化设计与仿真分析

目的本研究以平衡车车架为研究对象,旨在满足模型强度与刚度约束条件的前提下,通过拓扑优化设计实现车架质量的减轻,从而为平衡车车架的轻量化设计提供参考。方法首先,通过SolidWorks软件建立车架的三维模型,然后利用ANSYS Workbench对原始车架进行静力学分析,以获取车架的应力分布情况。在此基础上,采用AltairInspire软件对原模型进行拓扑优化,优化目标是减少车架的质量。结果经过拓扑优化设计,得到了优化后的重构模型。与原始车架相比,优化后的车架质量减少了约54.0%。虽然优化后的车架在满足使用规范的前提下,米塞斯应力有所上升,但仍小于材料的屈服强度,确保了车架的安全性和稳定性。结论本研究通过拓扑优化方法有效地减少了平衡车车架的质量,同时保持了必要的结构强度和刚度。尽管优化后车架的应力有所增加,但仍在材料允许范围内,证明了拓扑优化在车架轻量化设计中的可行性。该方法为未来平衡车车架部件的设计和改进提供了新的思路和参考。

NumericalAnalysisforBucklingandPost─BucklingBehaviorofPlanarFrames

Research on the problem of buckling and post buckling for structures is one of noticed directions in the field of engineering mechanics at present. Whether from the aspect of theory or from the aspect of numerical method, it is necessary to have a deep research on the problem. In this paper, a new geometrical nonlinear element and numerical implementation were presented. By some examples, the problem of buckling and post bukling for planar frames subjected to given loads was discussed in detail.

Modal Correlation Based Analysis on Dynamic Characters of a Commercial Semi-Trailer's Chassis Frames

In order to evaluate two different schemes＇ structural dynamic characters, dynamic response analysis of a commercial truck＇s main chassis frames is carried out. On the basis of correlation study between the tested and calculated modal results, the assembled frames＇ finite element analysis （FEA） models with sufficient precision are built up. Random response analysis in frequency domain is carried out with these FEA models, RMS values of yon Mises and main principle stresses of these two frames are obtained. It shows that the analysis resuits of the distributing tendency and concrete value ranges are coincident very well with test results. And from the results, it could be concluded that frames of scheme A endures relative better loading conditions and should be adopted as the final scheme.

轮辐式索承网格屋盖钢结构单道胎架施工技术

泰安体育场作为山东省泰安市的新地标,其钢结构屋盖采用轮辐式索承网格结构,通过68榀径向索和1道中央环索形成张拉结构体系,最大悬挑跨度为45 m。通过数值分析对施工过程进行了精细化稳定性分析,针对不规则构件吊装的工程技术难点,进行了吊装方案的设计与优化;考虑到成本控制与施工周期,极具创新性地采用了径向单道胎架作为屋盖施工过程中的临时支撑,结合工程实际情况设计了胎架转换结构,并对单道胎架整体在多种可能的荷载组合作用下进行验算与校核。通过对体育场屋盖施工全过程的模拟以及对安装过程中的重难点进行优化分析,为现场施工的安全顺利开展提供了技术保障,可为其他类似采用单道胎架施工方法的工程提供施工方案设计的新思路。

Effect of Increasing Speed on Stress of Biaxial Bogie Frames

Increasing the trains’ speed has always been one of the goals of any railway industry and train manufacturers. Also, the influence of the train speed on bogie’s dynamics has an immense importance. Therefore, it is important to analyze the effect of train speed on the stress distribution in different parts of train structure. In this study the result of the increasing speed on the applied stresses of a biaxial bogie frame has been examined. For this purpose, a biaxial bogie frame has been modeled using finite element analysis. Static and dynamic forces applied on the bogie with biaxial frame have been obtained for different speeds and rail roughness. The Von Mises stresses are adopted as equivalent stresses in the strength calculation. The results show that maximum stress always has been induced in the bogie bowl also the increase in bogie’s speed has remarkable effect on the increment of applied stresses in the bogie frame.

Progressive Collapse of Steel Frames

This paper investigates the behavior of steel frames under progressive collapse using the finite element method. Non-linear finite element models have been developed and verified against existing data reported in the literature as well as against tests conducted by the authors. The nonlinear material properties of steel and nonlinear geometry were considered in the finite element models. The validated models were used to perform extensive parametric studies investigating different parameters affecting the behavior of steel frames under progressive collapse. The investigated parameters are comprised of different geometries, different number of stories and different dynamic conditions. The force redistribution and failure modes were evaluated from the finite element analyses, with detailed discussions presented.