航空发动机整机静子建模与刚度验证

基于建立航空发动机整机状态的结构动力学分析有限元模型要求,对应用于静子机匣的不同有限元网格模型进行了对比分析,并将其组装成整机模型,进行了各支点的静柔度计算和对比试验。结果表明:对静子建模可分为主承力和其他机匣部件分别进行。承力机匣采用实体单元模型,有效模拟其刚度特性;传力机匣采用壳单元模型,在保证计算精度的前提下减小计算规模。通过对整机静子模型状态下轴承座静柔度计算与试验结果的对比,验证了整机静子模型刚度分布的有效性,经过质量修正后可以为整机状态结构动力学分析提供模型。

面板与坝体的分期施工高差对面板脱空变形的影响

【目的】研究高面板堆石坝面板与坝体的分期施工高差对于面板脱空变形的影响。【方法】在分析面板脱空机理的基础上,运用三维有限元子模型法,考虑堆石体的流变变形,以国内某高面板堆石坝工程为例,对不同面板与坝体分期施工高差方案所产生的面板脱空变形特征进行分析。【结果】面板与坝体的分期施工高差对各期面板的脱空变形影响显著,分期施工高差越大,各期面板的脱空变形相应越小;对于200m级的高面板堆石坝,为有效避免面板脱空现象,面板与坝体的分期施工高差宜控制在15m以上。【结论】对于采用分期施工方案的高面板堆石坝,应结合工程实际情况,通过有限元计算等方法合理选择适宜的面板与坝体的分期施工高差。

高土心墙堆石坝防渗墙与心墙连接部位高塑性粘土区设置研究

对于深厚覆盖层上的高土心墙堆石坝,防渗墙与心墙连接部位通常设置协调变形的高塑性粘土区,高塑性粘土区的合适的大小与坝高,坝体及坝基材料性能等多因素有关。本文采用基于子模型法的三维非线性有限元对长河坝水电站大坝防渗墙与土心墙连接部位不同的高塑性粘土区设置方案进行了研究,研究成果表明连接部位高塑性粘土区的大小对心墙、廊道和防渗墙的应力变形均有影响。

Finite element simulation and optimal analysis of surfacing on steel orthotropic bridge deck

To analyze the stress state of steel orthotropic deck pavement and provide reference for the design of the overlay, the inner stress state and strain distribution of surfacing under the load of the deformation of the whole bridge structure and tyre load are analyzed by the finite element method of submodeling. Influence of surfacing modulus on the strain state of the overlay is analyzed for the purpose of the optimal design of the overlay structure. Analysis results show that the deformation of the whole bridge structure has no evident influence on the stress state of the overlay. The key factor of the overlay design is the transverse tensile strain in the overlay above the upper edge of web plate of rib. The stress state of the overlay is influenced evidently by the modulus of rigidity transform overlay. And the stress state of the overlay can be optimized and lowered by increasing the modulus and thickness of rigidity transform overlay, The fatigue test has been done to evaluate the fatigue performance and modulus of different deck pavement materials such as epoxy asphalt, SBS modified asphalt, rosphalt asphalt which can provide reference for deck pavement structure design.

钩尾框尾部弯角疲劳裂纹扩展寿命预测研究

提出了一种预测工程构件疲劳裂纹扩展寿命的方法。应用能量释放率理论,通过3维子模型有限元技术,计算工程构件疲劳裂纹尖端的应力强度因子,由Paris公式预测工程构件在实际载荷谱下的疲劳裂纹扩展寿命。采用该方法预测的13号车钩钩尾框尾部弯角疲劳裂纹扩展寿命与实际检修统计结果一致。

提速货车钩尾框安全使用寿命的估算方法

提出一种估算提速货车钩尾框安全使用寿命的方法。该方法基于损伤容限设计思想 ,通过子模型有限元技术和虚拟裂纹扩展方法 ,仿真应力集中区的裂纹及其扩展 ,应用能量释放率理论计算裂纹前沿的应力强度因子 ,由Paris公式估算在实测载荷谱下钩尾框的裂纹扩展寿命。

Numerical simulation of tire/soil interaction using a verified 3D finite element model

The compaction and stress generation on terrain were always investigated based on empirical approaches or testing methods for tire/soil interaction.However,the analysis should be performed for various tires and at different soil strengths.With the increasing capacity of numerical computers and simulation software,finite element modeling of tire/terrain interaction seems a good approach for predicting the effect of change on the parameters.In this work,an elaborated 3D model fully complianning with the geometry of radial tire 115/60R13 was established,using commercial code Solidwork Simulation.The hyper-elastic and incompressible rubber as tire main material was analyzed by Moony-Rivlin model.The Drucker-Prager yield criterion was used to model the soil compaction.Results show that the model realistically predicts the laboratory tests outputs of the modeled tire on the soft soil.

Prevention of rockburst by guide holes based on numerical simulations

We studied variations in the stress field around guide holes drilled during tunnel excavation to understand the mechanical mechanism by which these holes help prevent rockburst.The study used elasto-plastic analysis of a circular chamber under non-axisymmetrical loads.The results showed that the unloading of in-situ stresses, and the forming of a secondary stress field, leads to a severe change in the stress field around the guide holes.This causes the formation of an X-shaped area of plastic deformation, which prevents the rockburst.Adopting a sub-model finite element technique, we analyzed the factors that influence the distribution of the plastic area, such as the guide hole distribution and the in-situ stress state.The calculations showed that higher initial stresses result in greater adjustment to the stress field.When the stress concentration is greater the size of the plastic area surrounding the guide hole is larger.A multi-row distribution of the guide holes shaped like a quincunx can increase the interconnectivity of the plastic areas and allow the plastic area to extend from the tunnel wall deep into the surrounding rock.An optimized design was put forward based on the distribution of the plastic area around guide holes and the factors that influence it.

Influence of Soft Filler on Stress Concentration Factor of Elliptic Holes in a Rectangular Plate

Finite element models were established to analyze the influence of soft filler on stress concentration for a rectangular plate with an elliptic hole in the center. The influence was quantified by means of stress concentration factor (SCF). Seven shape factors of the elliptic hole and three levels of elasticity modulus of the soft filler were considered. The reduction coefficient and sensitivity index of SCF are the two indicators in evaluating the influence of soft filler. It was found that the reduction coefficient of SCF increases significantly as the shape factor and the elasticity modulus of the filler increase, indicating that soft filler can reduce the concentrated stress effectively, especially when the shape factor is great. Analysis for the sensitivity index of SCF indicates that SCF is more sensitive to materials with small elasticity modulus than to materials with large one.

Electromagnetic design and dynamic analysis of large turbo-generator

Through a great deal calculation, the design and simulation analysis of stator parametric and rotor electromagnetic system of 1000MW turbo-generator are performed by using Ansoft Maxwell Rmxprt12.1 software. Besides. the basic parameters of the generator, the geometry dimensions of the stator and rotor, type and sizes of the slots, coils and windings parameters and the way of windings connection are determined. The finite element model of electromagnetic systems of generator stator and rotor was constructed by Ansoft Maxwe112D3D 12.1, and the transient electromagnetic characteristics of generator was analyzed and simulated. The 3D geometric models of turbo-generator were established respectively by using PROE software, and the dynamic finite element model of generator structure was built by ANSYS workbench 11.0. In addition, the dynamic characteristics of stator iron core, stator frame were calculated respectively. The simulation calculation has shown that the structural parameters, material parameters, and the electromagnetic characteristics parameters for large turbogenerator that are put forward by this paper should be optimal. and the design plan and method suggested by this paper should be feasible. The paper provides an effective solution for the development of larger turbo-generator than 1000 MW.

Anode Simulation and Cathode Design for Electrolytic Dressing of Diamond Profile Wheel

The design methods of anode and cathode are proposed for precision profile grinding. Based on the electrolytic machining theory, electrolytic equilibrium condition and Faraday′s law of electrolysis are applied to establishing the mathematical model of profile diamond dressing process- es. A finite element method (FEM) program is developed to solve the inverse boundary problem of Laplace′s equation. Desired anode contour or cathode shape is determined by computing the distribution of electric potential layer by layer. Electrolytic machining experiment is carried out to verify the simulated anode shape. The research result shows that shape deviation between designed cathode and profile wheel increases with the value of angle between feed rate and the normal to anode surface. The shape of simulated anode is consistent with the contour of metal-bonded diamond profile wheel for a given cathode. Based on the anode contour, cathode shape can also be designed accurately.

Computational Fracture Analysis of an AFM-Specimen under Mixed Mode Loading Conditions

Fracture processes in ship-building structures are in many cases of a 3-D character. A finite element （FE） model of an all fracture mode （AFM） specimen was built for the study of 3-D mixed mode crack fracture behavior including modes Ⅰ,Ⅱ, and Ⅲ. The stress intensity factors （SIFs） were calculated by the modified virtual crack closure integral （MVCCI） method, and the crack initiation angle assessment was based on a recently developed 3-D fracture criterion--the Richard criterion. It was shown that the FE model of the AFM-specimen is applicable for investigations under general mixed mode loading conditions, and the computational results of crack initiation angles are in agreement with some available experimental findings. Thus, the applicability of the FE model of the AFM-specimen for mixed mode loading conditions and the validity of the Richard criterion can be demonstrated.

Design Methods for Improving the Performance and Thermal Stability of Radar

The radar power supplies exhibit a complex electronics. The development of more and more compact systems leads to master the interaction between different parts of the power supply while reducing electronic circuits, magnetic and thermal couplings from the constitutive circuitry. The consideration of these phenomena is very difficult at the design of the power supply. This paper presents two complementary methods based first on a circuitry model for the quantification of heat sources and secondly on finite element model for heat diffusion. This approach can help a designer in the goal of improving the performances and thermal stability of radar tied to the supply circuit subset.

Light-induced electro-rotation:Microspheres spin in micro-manipulation using light-induced dielectrophoresis

According to the equivalent circuit model(ECM),finite element model(FEM) and physical experiment,the LIDEP force induced by the spatial variations of the phase of AC electric fields produced by the bright and dark regions on the photoconductive layer was demonstrated.Besides,the phenomenon of the light-induced electro-rotation(LIER) caused by the light-induced rotating electric field was confirmed numerically and experimentally for the first time.It may be helpful to go out of the dilemma that only the dipole moment model,based on the effect of light-induced partial potentials,can be used for LIDEP theoretical calculation currently.Through the FEM simulation and the electro-rotating experiment of yeast cells,it was found that the direction of yeast's LIER is relevant to the distance between its location and the edge of optical electrode,and the spin velocity of LIER is inversely proportional to that distance.Nevertheless,the LIER torques in the three-electrode mode show a non-uniform distribution where the LIDEP forces are harmful for a particle spinning stably around a fixed axis.Moreover,a four-electrode double-layer mode was proposed for the first time and the finite element simulation results agreed with the expected design,suggesting a new way for the dielectric spectrum measurement based on LIER.

Multi-scale finite element analysis of chloride diffusion in concrete incorporating paste/aggregate ITZs

In this paper,we propose a concurrent multi-scale finite element(FE) model coupling equations of the degree of freedoms of meso-scale model of ITZs and macroscopic model of bulk pastes.The multi-scale model is subsequently implemented and integrated into ABAQUS resulting in easy application to complex concrete structures.A few benchmark numerical examples are performed to test both the accuracy and efficiency of the developed model in analyzing chloride diffusion in concrete.These examples clearly demonstrate that high diffusivity of ITZs,primarily because of its porous microstructure,tends to accelerate chloride penetration along concentration gradient.The proposed model provides new guidelines for the durability analysis of concrete structures under adverse operating conditions.

New analytical solution for the analysis and design of permanent magnet thrust bearings

On the basis of the current sheet model, a new analytical solution for permanent magnet （PM） bearings is developed. Compared with analytical methods based on the coupling energy model and the magnetic dipole model, the proposed one is more physically intuitive and convenient for engineering designers. According to the analytical model, the thrust characteristics of a novel PM thrust bearing is studied and verified by finite element analysis （FEA）. In the proposed thrust bearing configuration, the rotor is composed of stacked PM tings with alternative axial magnetization directions, and the stator with alternative radial magnetization directions while copper rings are used to separate adjacent PM rings. A prototype PM thrust bearing with the proposed configuration is designed and fabricated. The performances of the PM thrust beating are experimentally validated. It is shown that the calculation accuracy of the presented analytical solution is satisfying.