3D FEM simulation of flow velocity field for 5052 aluminum alloy multi-row sprocket in cold semi-precision forging process

Based on the design of the multi-row sprocket with a new tooth profile,a cold semi-precision forging process for manufacturing 5052 aluminum alloy multi-row sprocket was presented.Through simulating the forging process of 5052 aluminum alloy sprocket billet with 3D rigid-viscoplastic FEM,both the distributions of flow velocity field in axial(U_Z),radial(U_R) and circumferential(U_θ) directions and the curves of velocity component in different deformation regions were respectively obtained.By comparison and analysis of the velocity varying curves,the velocity component relation conditions for filling the die cavity were clarified.It shows that when the die cavity is almost fully filled,the circumferential velocity U_θ increases sharply,implying that U_θplays a key role in fully filling the die cavity.

2D FEM analysis for coupled thermo-hydro-mechanical-migratory processes in near field of hypothetical nuclear waste repository

In order to consider the influence of temperature and underground water movement, an elastoplastic model and a 2D FEM stress fields on the migration of radioactive nuclide with code for analysis of coupled thermo-hydro-mechanical （THM） processes in saturated and unsaturated porous media were extended and improved through introducing the percolation and migration equation, so that the code can be used for solving the temperature field, flow field, stress field and nuclide concentration field simultaneously. The states of temperatures, pore pressures and nuclide concentrations in the near field of a hypothetical nuclear waste repository were investigated. The influence of the half life of the radioactive nuclide on the temporal change of nuclide concentration was analyzed considering the thermo-hydro-mechanical-migratory coupling. The results show that, at the boundary of the vitrified waste, the concentration of radioactive nuclide with a half life of 10 a falls after a period of rising, with the maximum value of 0.182 mol/m3 and the minimum value of 0.181 mol/m^3 at the end of computation. For a half life of 1 000 a, the concentration of radioactive nuclide always increases with the increase of the time during the computation period; and the maximum value is 1.686 mol/m^3 at the end of the computation. Therefore, under the condition of THM coupling, the concentration of radioactive nuclide with a shorter half life will decrease more quickly with water flow; but for the radioactive nuclide with a longer half life, its concentration will keep at a higher level for a longer time in the migration process.

Mathematical Modelling and 3D FEM Analysis of the Influence of Initial Stresses on the ERR in a Band Crack’s Front in the Rectangular Orthotropic Thick Plate

This paper deals with the mathematical modelling and 3D FEM study of the energy release rate(ERR)in the band crack’s front contained in the orthotropic thick rectangular plate which is stretched or compressed initially before the loading of the crack's edge planes.The initial stretching or compressing of the plate causes uniformly distributed normal stress to appear acting in the direction which is parallel to the plane on which the band crack is located.After the appearance of the initial stress in the plate it is assumed that the crack's edge planes are loaded with additional uniformly distributed normal forces and the ERR caused with this additional loading is studied.The corresponding boundary value problem is formulated within the scope of the so-called 3D linearized theory of elasticity which allows the initial stress on the values of the ERR to be taken into consideration.Numerical results on the influence of the initial stress,anisotropy properties of the plate material,the crack’s length and its distance from the face planes of the plate on the values of the ERR,are presented and discussed.In particular,it is established that for the relatively greater length of the crack’s band,the initial stretching of the plate causes a decrease,but the initial compression causes an increase in the values of the ERR.

Analysis of ground vibrations induced by high-speed train moving on pile-supported subgrade using three-dimensional FEM

The pile-supported subgrade has been widely used in high-speed railway construction in China.To investigate the ground vibrations of such composite foundation subjected to moving loads induced by high-speed trains(HSTs),three-dimensional(3D)finite element method(FEM)models involving the pile,pile cap and cushion are established.Validation of the proposed model is conducted through comparison of model predictions with the field measurements.On this basis,ground vibrations generated by HSTs under different train speeds as well as the ground vibration attenuation with the distance away from the track centerline are investigated.In addition,the effects of piles and pile elastic modulus on ground vibrations are well studied.Results show that the pile-reinforcement of the subgrade could significantly contribute to the reduction of ground vibrations.In particular,the increase of elastic modulus of pile could lead to consistent reduction of ground vibrations.However,when the pile elastic modulus is beyond 10 GPa,this benefit of pile-reinforcement on vibration isolation can hardly be increased further.

大型高架桥无支架盖梁施工过程模板受力特性的3D-FEM模拟分析

以上海S32高速公路闵浦大桥西侧引桥段的盖梁施工为例,通过合理的边界条件处理,基于ABAQUS有限元分析软件建立了复杂结构的3D-FEM模型,并以混凝土弹性模量和泊松比的变化模拟实际施工,进而分析无支架盖梁的受力状态.计算结果与现场实测的结果基本吻合,为无支架盖梁施工技术的研究分析提供了参考方法.研究表明:混凝土浇注完成约10 h左右,即具有90%的设计强度,基本能承受自身重力荷载,盖梁的竖向及横向荷载逐渐向混凝土转移;同时,该时间的确定为现场确定拆模时间、提高施工进度提供了依据.

上颌前牙段Tip-Edge正畸矫治系统三维有限元模型的建立

目的:建立带Tip-Edge托槽的上颌前牙段牙齿(33)及牙周组织的三维有限元模型,为Tip-Edge矫治技术的生物力学分析奠定基础。方法:通过多层螺旋CT扫描上颌骨,采用Mimics10.01重建上颌骨与33牙齿;采用Geomagic stu-dio10软件去除坏点,并对上颌骨及牙齿进行面网格划分;在牙根表面向外均匀偏移0.25mm,生成牙周膜前体;利用UG5.0软件建立Tip-Edge托槽及尺寸为0.55mm×0.71mm的矩形弓丝的实体模型;利用ANSYS10.0软件进行布尔运算生成牙周膜并组装弓丝、Tip-Edge托槽、上颌骨、33牙齿及相应牙周膜,进行网格划分。结果:建立了带托槽的上颌骨、33牙齿及牙周组织的Tip-Edge矫治系统三维有限元模型。建模过程中托槽模型的轴倾角、转矩角等数据与托槽的实际数据是相一致的。对模型施加一定的约束与载荷之后即可进行相应的有限元力学分析。结论:结合运用Mimics、Geomagic studio、UG、ANSYS等软件建立的Tip-Edge矫治系统的三维有限元实体模型真实有效,建模方法实用,可根据需要进行不同的力学分析。

种植体支持对KennedyⅠ类可摘局部义齿应力分布的影响

目的:分析增加种植体支持对于KennedyⅠ类缺失可摘局部义齿应力分布影响。方法:应用三维有限元法,在不同加载条件下分析比较有无种植体支持对于双侧后牙游离缺失可摘局部义齿应力分布的影响。结果:增加种植体支持可以显著降低可摘局部义齿基托的位移,减小义齿基牙牙周膜和基托下支持组织的应力。结论:由种植体支持的可摘局部义齿有利于保护义齿基牙及基托下支持组织的健康。

真空-堆载联合预压软基中PVD单元的构造及应用

根据真空-堆载联合预压软基中塑料排水板的作用特点,提出了PVD单元的概念以及有限元格式、矩阵表达式,并将其结合到三维Biot固结有限元程序中.对真空-堆载联合预压计算例题,用PVD单元有限元法、常规有限元法进行了计算、比较,结果表明PVD单元有限元法能较好地模拟塑料排水板在真空-堆载联合预压地基中的应用.

Vibration and sound radiation of a rotating train wheel subject to a vertical harmonic wheel–rail force

The rapid development of high-speed railway networks requires advanced methods for analysing vibration and sound radiation characteristics of a fast rotating train wheel subject to a vertical harmonic wheel-rail force. In order to consider the rotation of the wheel and at the same time increase the computational efficiency, a procedure is adapted in this paper taking advantage of the axial symmetry of the wheel. In this procedure, a recently developed 2.5D finite element method, which can consider wheel rotation but only requires a 2D mesh over a cross section containing the wheel axis, is used to calculate the vibration response of the wheel. Then, the vibration response of the wheel is taken as acoustic boundary condition and the 2.5D acoustic boundary element method, which only requires a 1D mesh over the boundary of the above cross section, is utilised to calculate the sound radiation of the wheel. These 2.5D methods and relevant programs are validated by comparing results from this procedure with those from conventional 3D analyses using commercial software. The comparison also demonstrates that these 2.5D methods have a much higher computational efficiency. Using the 2.5D methods, we study the wheel rotation speed influences on the factors including the vertical receptance of the wheel at wheel-rail contact point, sound pressure level at a pre-defined standard measurement point, radiated sound power level, directivity of the radia- tion, and contribution of each part of the wheel. It can be concluded that the wheel rotation speed splits most peaks of the vertical receptance at the wheel-rail contact point, sound pressure levels at the field, and the sound power level of the wheel into two peaks. The directivity and power contribution of the wheel are also significantly changed by the wheel rotation speed. Therefore, the rotation of a train wheel should be taken into account when calculating its vibration and sound radiation.

Extended Kantorovich method for local stresses in composite laminates upon polynomial stress functions

The extended Kantorovich method is employed to study the local stress concentrations at the vicinity of free edges in symmetrically layered composite laminates subjected to uniaxial tensile load upon polynomial stress functions. The stress fields are initially assumed by means of the Lekhnitskii stress functions under the plane strain state. Applying the principle of complementary virtual work,the coupled ordinary differential equations are obtained in which the solutions can be obtained by solving a generalized eigenvalue problem. Then an iterative procedure is established to achieve convergent stress distributions. It should be noted that the stress function based extended Kantorovich method can satisfy both the traction-free and free edge stress boundary conditions during the iterative processes. The stress components near the free edges and in the interior regions are calculated and compared with those obtained results by finite element method（FEM）. The convergent stresses have good agreements with those results obtained by three dimensional（3D） FEM. For generality, various layup configurations are considered for the numerical analysis. The results show that the proposed polynomial stress function based extended Kantorovich method is accurate and efficient in predicting the local stresses in composite laminates and computationally much more efficient than the 3D FEM.

修正D-P模型在三峡二期围堰分析中的应用

为了考虑中主应力及材料剪胀性的影响,并验证堰体填筑材料参数,运用遗传神经网络对堰体填料进行参数反演,引入修正D-P模型进行围堰施工模拟.修正D-P模型采用非相适应的流动法则,可以模拟材料的各向同性硬化/软化及中主应力的影响,并可以考虑流变;遗传神经网络具有很强的非线性映射能力及全局优化功能.在运用遗传神经网络对堰体材料进行参数反演的基础上,利用修正D-P模型对三峡二期围堰填筑过程进行了模拟.实例分析表明,遗传神经网络能准确反演材料的力学参数;修正D-P模型适合分析围堰材料的力学性能;两者结合分析土石围堰时,计算结果与实际情况相符.修正D-P模型克服了Duncan-Chang模型不能模拟中主应力及材料剪胀性的缺点;遗传神经网络反演参数可以使计算参数与实际情况更接近,两者有机结合可提高分析精度.

Forced and Natural Vibrations of an Orthotropic Pre-Stressed Rectangular Plate with Neighboring Two Cylindrical Cavities

Forced and natural vibrations of a rectangular pre-stressed orthotropic compositeplate containing two neighboring cylindrical cavities whose cross sections are rectangularwith rounded-off corners are investigated numerically. It is assumed that all the end surfacesof the rectangular pre-stressed composite plate are simply supported and subjected to auniformly distributed normal time-harmonic force on the upper face plane. The consideredproblem is formulated within the Three-Dimensional Linearized Theory of Elastic Waves inInitially Stressed Bodies (TDLTEWISB). The influence of mechanical and geometricalparameters as well as the initial stresses and the effect of cylindrical cavities on the dynamicalcharacteristics of the rectangular orthotropic composite plate are analyzed and discussed.

RESEARCH ON INFLUENCE OF TEMPERATURE ON A PRECISION FORGING PROCESS OF BLADE WITH A TENON

The blade precision forging process is a forming process with high temperature and large plastic deformation. Interaction of deformation and heat conduction leads to large uneven distribution of temperature. The unevenness of temperature distribution has a great effect on mechanical properties and the microstracture of materials. So it is necessary to consider the influence of temperature on the precision forging process of blades. Taking a blade with a tenon into consideration, a 3D mechanical model in precision forging is built up. The distribution laws of temperature field and the influence of the temperature on the equivalem stress in the process are obtained by using 3-D coupled thermo-mechanical FEM code developed by the authors Theresuits obtained illustrate that the influence of the temperature field on the blade forging process is considerable. The achievements of predicting microstructure and mechanical properties for forged blades is significant.

Simulation of seafloor electrical resistivity measuring equipment based on 3D finite element method

In order to explore the mineral resources buried in sea mud,it is necessary to use seabed resistivity measuring equipment,which works closer to the sediments than ordinary ship-based geophysical measuring equipment. Because of the harsh environment of seafloor,high pressure and highly conductive seawater,marine magnetotelluric method developed slowly. The sea floor environment is similar to the environment of logging, According to the design of dual lateral logging equipment,a new equipment for seafloor electrical resistivity measurement is designed. Four 3D FEM models that contain resistivity abnormal targets are built to test the ability of this equipment to locate different shape of shallow buried resistivity abnormal targets in sea mud. The authors propose the method to correct the response curve while the bottom surface of this equipment is suspended or not parallel to the seafloor. The resistivity of targets can be calculated accurately.

Seismic Response of Magnetically Levitated House

This study explored the seismic response of a house supporting base sides with a polymeric displacement control material and by magnetically levitating the foundation base. In this paper, we explore the possibility and efficacy of a seismic-isolated detached house as described above from both a shaking table experiment of model and three-dimensional finite element analysis. The seismic-isolated model showed stable response and its acceleration response was significantly reduced compared to the base-fixed model in the shaking table test. Three-dimensional finite element analysis was possible to simulate the experimental results. In the seismic response analysis of a full-scale detached house, the seismic-isolated model showed response reduction and its residual displacement was smaller than that of the sliding-base isolation model.

上部结构-筏基-地基共同作用子结构法FEM分析

应用子结构法理论,将上部结构刚度矩阵凝聚到筏板基础,同时将采用D-P模型的地基土体弹塑性刚度矩阵也凝聚到筏板基础上,建立了考虑上部结构、基础、地基共同作用的三维弹塑性有限元模型理论。利用此理论建立某工程框架结构裙楼-框架芯筒结构主楼-筏板基础-地基共同作用FEM模型,通过ANSYS程序对此模型进行数值模拟。结果表明,主楼结构的柱、梁应力在考虑共同作用比不考虑共同作用有增大趋势,群楼柱轴应力在考虑共同作用比不考虑共同作用小,而群楼梁弯应力却相反。并进一步分析得出考虑共同作用基础沉降差引起上部结构杆件应力重新分布,尤其是基础沉降差引起主楼的柱轴应力、梁弯应力的变化率大于群楼柱轴应力、梁弯应力的变化率的结论,该结论对以后工程设计有重要参考价值。

MIDAS/Civil在预应力空心板简支梁桥结构抗震分析中的应用

以有限单元法基本理论为基础,介绍了有限元通用软件MIDAS/Civil在预应力空心板简支梁桥结构抗震计算中的应用问题.采用三维有限元法,实现了预应力空心板简支梁桥的动力特性模拟,分析了在E1、E2地震作用下,桥梁各控制截面的抗弯能力、抗剪能力,以及支座厚度和抗弯稳定性等抗震性能,并提出切实可行的抗震措施,为桥梁施工质量控制提供必要的理论指导与技术支持.

DEFORM-3D软件在叶片锻坯结构形式选取中的应用

在叶片锻造过程中,由于变形量大,锻出的叶片会出现如褶皱、裂纹这样的缺陷。为了提高生产效率,一般要求在螺旋压力机上一次锻造成形。因此,采用合理的毛坯结构形式在最小成形载荷下来获得最低程度的缺陷就显得十分重要。常规用来选择叶片锻坯合理结构形式的方法有诸多缺点,采用有限元方法将会在很大程度上弥补这些不足。

A Numerical-analytic Method for Quickly Predicting Springback of Numerical Control Bending of Thin-walled Tube

Springback is one of important factors influencing the forming quality of numerical control （NC） bending of thin-walled tube. In this paper, a numerical-analytic method for springback angle prediction of the process was put forward. The method is based on springback angle model derived using analytic method and simulation results from three-dimensional （3D） rigid-plastic finite element method （FEM）. The method is validated through comparison with experimental results. The features of the method are as follows： （1） The method is high in efficiency because it combines advantages of rigid-plastic FEM and analytic method. （2） The method is satisfactory in accuracy, since the field variables used in the model is resulting from 3D rigid-plastic FEM solution, and the effects both of axial force and strain neutral axis shift have been included. （3） Research on multi-factor effects can be carried out using the method due to its advantage inheriting from rigid-plastic FEM. The method described here is also of general significance to other bending processes.

Transient Temperature Field Analysis of Brake in Nonaxisymmetric Three-dimensional Model

The disk-pad brake used in automobile is divided i nt o two parts: the disk, geometrically axisymmetric, and the pad, of which the geo metry is three-dimensional. In the course of braking, all parameters of the pro cesses (velocity, load, temperature, physicomechanical and tribological characte ristics of materials of the couple, and conditions of contacts) vary with the ti me. Considerable evidence has show that the contact temperature is an integral f actor reflecting the specific power friction influence at the combined effect of load, speed, friction coefficient, thermo physical and durability properties of materials of a frictional couple. Furthermore, the physic mechanical state of t he interface of the disk and pads is determined not only by the contact temperat ure but also by the nonstationary temperature field. Using the two-dimensional model for thermal analysis implies that the contact conditions and frictiona l heat flux transfer are independent of θ. This may lead to false thermal elast ic distortions and unrealistic contact conditions. An analytical model is presen ted in this paper for the determination of contact temperature distribution on t he working surface of a brake. To consider the effects of the moving heat source (the pad) with relative sliding speed variation, a transient finite element tec hnique is used to characterize the temperature fields of the solid rotor with ap propriate thermal boundary conditions. And the transient heat conduction problem can be solved as a nominal 3-D transient heat transfer problem with an immovab le heat source. Numerical results shows that the operating characteristics of th e brake exert an essentially influence on the surface temperature distribution a nd the maximal contact temperature. The temperature field presents a noaxisymmet ric characteristic (a function of θ) and proves to be strongly localized and po ssesses a sharp gradient in both axial and radial directions.