Mechanical strength analysis of SMT solder joints by finite element method

0IntroductionTileapplicationofSMT(SurfaceMountTechnology)11asbeedacceleratedrecelltly.however.thestrellgtllofSMTsolderjointshasbeedextremelycollcerlledover.AnimportantreasonisthattileleadsofSMD(Sun'aceMountDevice)donotpasstllrougllthePCB.Asaresult.Illllik…     

Mechanical strength analysis of SMT solder joints by finite element method

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有限元模拟SiC增强Al基复合材料的力学行为

采用有限元方法和轴对称单胞模型模拟了增强体(SiC)形状、体积分数以及不同基体类型对铝基复合材料力学行为的影响。模拟结果表明:增强体的加入会阻碍基体的塑性流变,使基体内发生非均匀变形,在增强体尖角处出现应力集中;椭圆柱形增强体对基体塑性变形的阻力最大,传递载荷的能力最强,因此强化效果最好。在一定范围内,随着增强体体积分数的增加,基体与增强体之间的比表面积增大,有利于载荷的传递;增强体体积分数的增加导致颗粒间距减小,几何必须位错自由运动的路径减少,复合材料的强度也随之增加。此外,不同类型基体自身的塑性流变能力不同,Al-Zn-Mg基体强度最高,在拉伸变形过程中,受到增强体的阻碍作用最大,会有更多的载荷从基体传递到增强体,以Al-Zn-Mg为基体的复合材料的强度最高。     

基于ANSYS有限元法的某型车床主轴振动频率响应分析

Making an analysis for vibration modal and frequency response of the lathe spindle, respectively by using finite element method based on ANSYS and experiment of CA6140 type lathe in machining, and the calculation results are compared and analyzed, which verified the accuracy of ANSYS method. Numerical simulation and experimental results show that: Spindle in the first order and fifth order are prone to resonance, but did not reach resonance, the low order natural frequency have more effect than the high order natural frequency of the spindle vibration; by the experiments can conclude that the maximum vibration of the main shaft in the working state is mainly concentrated in the vicinity of its two ends, therefore, the improved bearing is an important way to reduce the vibration of the main shaft and ensure the machining accuracy, and the research results can provide a theoretical reference for the structural optimization design of the lathe.     

Sequential coupling simulation for electromagnetic–mechanical tube compression by finite element analysis

A sequential coupled field analysis of electromagnetic tube compression process has been performed by using the finite element method (FEM). A 2D axisymmetric electromagnetic model based on the magnetic vector potential is proposed for the calculation of magnetic field and magnetic forces; and Newmark integration method is used to calculate the dynamic plastic deformation of tube in the mechanical model. In each time step during the simulation, the transient magnetic forces acting on the tube are obtained from the electromagnetic model, which are then used as input load to the mechanical model. According to the tube deformation calculated, the geometry of the electromagnetic model is updated. Therefore, the sequential coupling simulation is realized between the electromagnetic model and the mechanical model, whose results are more accurate than the loosing coupling simulation method. The radial deformation along the outer generatrix of deformed tube wall is presented as a function of time and the plastic strain energy of electromagnetic tube compression is analyzed.     

基于有限元的轧机机架的机械性能分析

在对板簧轧机机架的结构形式进行深入分析的基础上,建立了轧机机架的三维模型.以ANSYS11.1有限元软件作为分析工具,对两种不同形式的轧机机架进行三维模型的有限元模拟,计算了机架的应力和位移,得到了机架的应力图与位移图,得出机架各单元和各节点的位移量及应力值.分析结果表明,有中间横梁机架的Y向位移明显小于无中间横梁的机架结构,且设备刚度提高了18.77%,为轧机机架的设计、改造、以及提高轧制精度提了供理论依据和参考数据.     

Mathematical simulation of a cathodic protection system by finite element method

A computer program was developed, to solve the numerical system generated by the variational formulation obtained by the Laplace bidimensional equation in rectangular coordinates at boundary conditions, Newman's type. The finite element method (FEM) was used to solve the numerical system. Compact support functions were used to simulate inert electrodes under an external current, this support was equal to the electrodes diameter. The validation of the model was corroborated when the results obtained by modeling were very similar to those given by experimentation. Three aspects of interest about cathodic protection were simulated; ? Electrodes distribution in the system. ? Low conductivity irregularities in the electrolyte. ? Different resistivities in the electrolyte.     

有限元分析在冲压模具设计中的应用

通过建立有限元模型，运用成形缺陷模拟和虚拟修模，解决由于不规则的形状而导致塑性流动的不均匀性所产生的拉裂和起皱，并运用在有限元分析过程中得到的工艺参考参数，如板料应力应变分布、厚度分布、成形力和压边力变化曲线等，缩短冲压模具设计周期。     

Three-dimensional analysis of elastic stress distribution of indented ceramic surface by finite element method

The three-dimensional stress distributions in the area surrounding indentation pattern for three different materials, Al2O3, Si3N4 and SiC were analyzed by finite element method（FEM）. Those theoretical results were also compared with the experimental ones by Rockwell hardness test. The effect of loading stress on the plastic deformation in specimens, surface was investigated on the assumption of shear strain energy theory by Huber-Mises when the materials were indented. The distributions of nomal stress, shear stress, and Mises stress were analysed with variations of loading conditions. It is clear that the analytical results for the stress distributions, the crack length and its density of probability are in good agreement with the experimental results.     

圆柱体平板镦粗应力场的有限元分析

应用刚粘塑性有限元法对圆柱体在两平板间镦粗时的应力场进行了分析 ,给出了毛坯在不同初始高径比时的心部应力随压下量的变化曲线。由此得出 :在变形过程中 ,圆柱体心部存在两向拉应力 ;并且在墩粗过程中 ,当瞬时高径比约为 1 .0时 ,心部σθ、σr 由拉应力转变为压应力。     

Fictive stress model based finite element analysis for bulk metallic glasses at an elevated temperature

It is important to manufacture micromachine parts and simulate the deformation behavior of bulk amorphous alloys in a superccoled liquid region. For these purposes, a correct constitutive model that can reproduce viscosity results is essential for good predictive capability. In this paper, finite element analyses of nonlinear behaviour in bulk metallic glasses during die compression in the supercooled liquid region have been carried out based on the fictive stress model in conjunction with the Maxwell viscoelastic model. The friction effect between the work piece and the die played an important role in inhomogeneous deformation.     

Three-dimensional analysis and computer simulation of shape rolling by the finite and slab element method

In this study a new simplified 3-D numerical method and the associated computer program have been developed to simulate the shape rolling process. The 2-D rigid-plastic finite element method (FEM), used for the generalized plane-strain condition, is combined with the slab method. This method, called FSEM (finite and slab element method), reduces the computational effort without losing much accuracy obtained in the 3-D computer simulation of the shape rolling process. The FSEM has been used to develop a computer program, called TASKS for three-dimensional analysis of shape-rolling as a kinematically steady-state process. The program TASKS has been used to simulate the metal flow and the bulge profile in flat rolling of slabs, the shape rolling of a simple H section, and the rolling of a practical H-beam section. In flat rolling, predicted spreads agreed well with experimental results, given in the literature. The metal flow in rolling of a simple H section was compared with results of a full 3-D simulation, obtained by other investigators. The comparison indicated that the present predictions give quite good results. Finally, the predictions made for a practical pass, used in rolling H sections, also compared well with experimental data.     

Die land optimization of section extrusion by finite element method

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耦合作用下的扁挤压筒有限元分析

由于扁挤压筒同时受到内压，预紧，热载荷作用，因此有必要考虑内压-预紧-热载荷的耦合作用。本文运用ANSYS分析软件，利用物理环境分析法建立了三层套组合式扁挤压筒内压-预紧-热载荷耦合有限元模型。模拟结果表明热应力的存在对扁挤压筒的等效应力分布影响较大，可以有效地降低内层套的最大等效应力值，但是扁挤压筒的应力分布形式并未改变，为进一步优化扁挤压筒结构尺寸、装配条件提供参考。同时表明了物理环境分析法分析耦合效应的可行性。     

超音速火焰喷涂流场有限元分析

在液体火箭发动机原理的基础上,建立了超音速火焰喷涂过程全流场分析模型,对KY-HVO(A)F多功能超音速火焰喷涂系统进行了流场分析,得到了HVOF与HVAF两种状态下燃气的速度、温度分布,分别体现了燃气欠膨胀与过膨胀的特点。在HVOF状态计算结果中有8个马赫锥而实际焰流照片中有8～9个马赫锥,所处位置基本对应,可以合理解释喷涂过程的激波现象,不同截面上的速度分布,体现了燃气速度在径向截面上的自模特性。     

Thermal analysis of a ceramic coating diesel engine piston using 3-D finite element method

In this study, firstly, thermal analyses are investigated on a conventional (uncoated) diesel piston, made of aluminum silicon alloy and steel. Secondly, thermal analyses are performed on pistons, coated with MgO-ZrO₂ material by means of using a commercial code, namely ANSYS. Finally, the results of four different pistons are compared with each other. The effects of coatings on the thermal behaviors of the pistons are investigated. It has been shown that the maximum surface temperature of the coated piston with material which has low thermal conductivity is improved approximately 48% for the AlSi alloy and 35% for the steel.     

Development of a thermo-viscoplastic cutting model using finite element method

In this paper, a cutting model is developed by applying the thereto-viscoplastic FEM (finite element method) to analyze the mechanics of steady state orthogonal cutting process. The model is capable of dealing with free chip geometry and chip-tool contact length. The coupling with thermal effects is also considered. In calculating temperature distributions, the “upwind” scheme is employed to remove spurious oscillations that occur in the solution and therefore it is possible to analyze high speed metal cutting. Orthogonal cutting experiments are performed for 0.2% carbon steel to validate the cutting model. Tool forces are measured and the results are discussed in comparison with the results of the FEM analysis.     

高强度涂层结合性能的试验研究及有限元分析

采用线切割沿涂层/基体界面切成对称切口,两边粘结后直接拉伸的试验方法对高强涂层抗拉结合强度进行评价.并借助有限单元法对涂层/基体交界面上的应力分布及切口附近的应力集中进行了分析,为正确评价涂层/基体的结合强度提供了理论依据.按此方法对不同工艺参数的热喷涂烧结涂层结合强度进行了评价.结果表明,此方法可对高强涂层与基体的结合强度进行评价.     

基于有限元法的平滑凹痕管道应力分析

针对管道上典型的平滑凹痕缺陷,根据管道的实际运行状况,建立了有限元模型;在其它参数不变的情况下,改变凹痕深度、管道壁厚、管道直径和凹痕纵向长度进行了大量计算;对计算结果进行了整理、归纳、作图,并对结果进行了单因素和多因素分析,得出应力随各参数的变化规律;采用非线性回归分析方法对计算结果进行了拟合.结果表明,在其它参数不变的情况下,凹痕管道最大应力与凹痕深度、壁厚、管径以及凹痕纵向长度之间的关系分别采用正弦模型、指数模型、线性模型和半对数线性模型最优,并且得到了具有一定适用范围下的具体关系式.