Finite element method for coupled diffusion-deformation theory in polymeric gel based on slip-link model

A polymeric gel is an aggregate of polymers and solvent molecules, which can retain its shape after a large deformation. The deformation behavior of polymeric gels was often described based on the Flory-Rehner free energy function without considering the influence of chain entanglements on the mechanical behavior of gels. In this paper,a new hybrid free energy function for gels is formulated by combining the EdwardsVilgis slip-link model and the Flory-Huggins mixing model to quantify the time-dependent concurrent process of large deformation and mass transport. The finite element method is developed to analyze examples of swelling-induced deformation. Simulation results are compared with available experimental data and show good agreement. The influence of entanglements on the time-dependent deformation behavior of gels is also demonstrated.The study of large deformation kinetics of polymeric gel is useful for diverse applications.

Thermo-hydro-mechanical-air coupling finite element method and its application to multi-phase problems

In this paper, a finite element method （FEM）-based multi-phase problem based on a newly proposed thermal elastoplastic constitutive model for saturated/unsaturated geomaterial is discussed. A program of FEM named as SOFT, adopting unified field equations for thermo-hydro-mechanical-air （THMA） behavior of geomaterial and using finite element-finite difference （FE-FD） scheme for so/l-water-air three-phase coupling problem, is used in the numerical simulation. As an application of the newly proposed numerical method, two engineering problems, one for slope failure in unsaturated model ground and another for in situ heating test related to deep geological repository of high-level radioactive waste （HLRW）, are simulated. The model tests on slope failure in unsaturated Shirasu ground, carried out by Kitamura et al. （2007）, is simulated in the framework of soil-water-air three-phase coupling under the condition of constant temperature. While the in situ heating test reported by Munoz （2006） is simulated in the same framework under the conditions of variable temperature hut constant air pressure.

Computational analysis of linear friction welding process and micromechanical modeling of deformation behavior for medium carbon steel

Finite element simulation of linear friction welding(LFW) medium carbon steel was carried out using the ABAQUS software. A two-dimensional(2D) coupled thermo-mechanical model was established. First, the temperature fields of medium carbon steel during LFW process were investigated. And then, the Mises stress and the 1st, 2nd and 3rd principal stresses fields' evolution of the steel during LFW process were studied. The deformation behavior of LFW carbon steel was analyzed by using micromechanics model based on ABAQUS with Python code. The Lode parameter was expressed using the Mohr stress circle and it was investigated in detail.

个性化头部生物力学模型的开发及验证

本文提出了一种个性化头部生物力学模型建模方法,并对所生成模型进行了有效性验证。该方法以图斯特50th百分位头部生物力学模型为基础,基于目标模型头部CT数据,采用三维点云配准和自由网格变形法,实现具有详实脑组织结构的个性化头部生物力学模型的快速建模。通过重构经典尸体试验,发现该方法构建的个性化头部生物力学模型在运动学和生物力学响应方面与尸体试验结果高度一致,且与通过逆向工程方法开发的头部生物力学模型并无明显差异,验证了本文方法所开发模型的有效性。因此,本文方法可用于快速构建具有详细解剖学结构的个性化头部生物力学模型,为损伤生物力学、临床医学和法医鉴定等领域的数字化需求提供基础计算分析工具。

2205/X65爆炸焊复合板JCO成型过程协同变形行为研究

为了研究JCO成型工艺参数对2205/X65爆炸复合板结合界面附近应变协调性的影响,建立了2205/X65爆炸复合板三点弯曲过程的有限元模型,结合数字图像相关法对模型进行了验证。采用该模型进行仿真研究,结果表明,上模半径越小,界面附近的最大应变差越大,复合板JCO在成型过程中变形不协调区域的宽度越小;跨距越小,复合板在JCO成型过程中变形不协调区域的宽度越大,跨度变化对界面附近最大应变差没有显著影响;下压量增大时,界面附近变形不协调区域的宽度增大,但界面附近最大应变差的变化不显著;下模半径大小和复合板厚度比对加工变形协调性影响不显著。在实际生产中,建议选用较大上模半径和较大跨距,采用小下压量多次成型。

A Coupling Model of the Discontinuous Deformation Analysis Method and the Finite Element Method

Neither the finite element method nor the discontinuous deformation analysis method can solve problems very well in rock mechanics and engineering due to their extreme complexities. A coupling method combining both of them should have wider applicability. Such a model coupling the discontinuous deforma- tion analysis method and the finite element method is proposed in this paper. In the model, so-called line blocks are introduced to deal with the interaction via the common interfacial boundary of the discontinuous deformation analysis domain with the finite element domain. The interfacial conditions during the incre- mental iteration process are satisfied by means of the line blocks. The requirement of gradual small dis- placements in each incremental step of this coupling method is met through a displacement control proce- dure. The model is simple in concept and is easy in numerical implementation. A numerical example is given. The displacement obtained by the coupling method agrees well with those obtained by the finite ele- ment method, which shows the rationality of this model and the validity of the implementation scheme.

P-FEMOL ANALYSIS OF PLATE BENDING PROBLEMS

In this paper, the p- version of the finite element method of lines (FEMOL) for the analysis of the Mindlin-Reissner plate bending problems is presented and a class of p-FEMOL elements with polynomial degrees as high as nine is developed. Numerical examples given in this paper show tremendous performance of the present method: namely, rapid convergence rate, high accuracy for both displacements and stress resultants, removal of shear-locking trouble, capability of dealing with difficult problems such as the boundary layer behavior near a free edge and stress concentration around a hole.

Effect of asymmetric rolling on mechanical characteristics,texture and misorientations in ferritic steel

The mechanical and microstructural properties as well as crystallographic textures of asymmetrically rolled low carbon steel were studied.The modelling of plastic deformation was carried out in two scales:in the macro-scale,using the finite elements method,and in the crystallographic scale,using the polycrystalline deformation model.The internal stress distribution in the rolling gap was calculated using the finite elements method and these stresses were then applied to the polycrystalline elasto-plastic deformation model.Selected mechanical properties,namely residual stress distribution,deformation work,applied force and torques,and bend amplitude,were calculated.The diffraction measurements,X-ray and electron backscatter diffraction,enabled the examination of texture heterogeneity and selected microstructure characteristics.The predicted textures agree well with those determined experimentally.The plastic anisotropy of cold rolled ferritic steel samples,connected with texture,was expressed by Lankford coefficient.

土石坝沥青混凝土心墙应力状态计算分析

构建了土石坝的材料本构模型和接触本构模型,采用有限元法分析了某工程沥青混凝土心墙坝的应力状态和变形情况,探讨了不同心墙材料参数、心墙底部与基座之间连接方式对心墙应力状态的影响。

铁路刚构-连续组合体系梁桥钢-混结合段静力试验研究

为研究大跨度铁路刚构-连续组合体系梁桥钢-混结合段的力学性能,以新建杭温铁路永嘉右行线跨甬台温特大桥主桥为背景,基于原桥节段有限元模型研究钢-混结合段的应力分布及传力特性,并基于缩尺模型试验对钢-混结合段承载能力、变形性能等进行分析。结果表明:刚构-连续组合体系梁桥钢-混结合段传力较为顺畅,钢-混结合段钢结构、混凝土结构纵向应力横向分布不均匀系数分别为0.72~1.42、0.63~1.31,钢-混结合段内纵向应力横向分布不均匀现象较过渡段更为显著;后承压板在传力过程中起着重要作用,结合段通过后承压板、剪力钉及PBL连接件分别可传递约56.4%、27.4%、16.2%的轴力,钢-混结合段中1.5 m钢格室段及2.5 m伸长段中钢结构分别将28.3%、15.3%的轴力传递给混凝土;结合段在1.8 P(P为设计荷载)作用下仍处于弹性工作状态,具有足够的承载能力,钢、混凝土强度安全系数分别不小于2.7、2.4;钢-混结合段挠度与三次多项式相符较好,变形较为平顺。

面向天线板热变形的有限元模型修正方法

为满足卫星天线板的在轨热变形测量要求,需要建立精确有限元模型模拟天线板热变形过程。蜂窝夹层板作为天线板主体结构,在有限元建模过程中通常需要对其进行简化处理,导致有限元计算结果与实验测量值之间存在差异。针对上述问题,进行了高温环境下天线板结构的热变形实验,得到温度场分布与热变形位移矩阵。通过对温度场拟合得到有限元模型热载荷。在此基础上,提出了利用天线板有限元模型与实验模型面外位移测量矩阵的均方根误差作为修正目标,基于多岛遗传算法的有限元模型修正方法,对模型材料参数与边界条件进行修正。修正后有限元模型的预测精度得到了明显提高。

高压工况上游泵送机械密封热力变形与密封性能分析

为研究高压工况下上游泵送机械密封的性能,考虑密封环与润滑液膜间的流固热力耦合作用,建立了其热弹流润滑模型,基于有限单元方法求解液膜润滑方程、密封环热传导方程和热力变形方程,采用三重迭代算法实现膜压、膜厚、温度和变形之间的耦合求解,研究了转速、密封压力和介质温度对上游泵送机械密封端面变形的影响规律,分析了热力变形作用下密封的上游泵送能力。研究结果表明,高压工况下密封端面产生了沿上游泵送方向收敛的液膜间隙,高密封压力下的力变形是主要原因,热变形部分抵消了压力变形带来的影响;随转速的增大,液膜沿上游泵送方向的收敛程度减小,上游泵送率增大,摩擦因数增大;随着密封介质压力的增大,液膜收敛程度增大,摩擦因数减小,上游泵送率大幅减小;随密封介质温度的升高,液膜收敛程度减小,摩擦因数减小,上游泵送率有所增加。研究结果可为高压上游泵送机械密封环的结构优化和设计提供理论参考。

Riveting Process Modeling and Simulating for Deformation Analysis of Aircraft＇s Thin-walled Sheet-metal Parts

The riveting joint is one of the important joint methods to permanently fasten two thin-walled sheet-metal parts. It is most ba- sic to efficiently analyze and estimate the deformation of the riveting joint for the performance, fatigue durability and damage of the riveting structure in the aircraft. This paper researches the riveting process mathematics modeling and simulating to more accurately analyze deformation of thin-walled sheet-metal parts. First, the mathematics and mechanics models for the elastic deformation, plastic deformation and springback of the rivet are built by mechanics theory. Second, on the basis of ABAQUS system, a finite element system, an instance made up of the rivet and two thin-walled sheet-metal parts of aluminum alloy is used to analyze and simulate the stress and deformation. What＇s more, a comparison is made between the results obtained by the mathematics and mechanics models and those by finite element method （FEM）. The models are proved true by the calculating and simulation results of the instance.

考虑土层变形特征的边坡稳定性分析方法研究

针对特长公路生态防护边坡的土体表面应力数据结果拟合度较低的问题,进行考虑土层变形特征的边坡稳定性分析方法研究。有限元分析防护边坡仿真结构,并结合极限平衡理论,设计特长公路生态防护边坡滑动模型。根据地层变形的沉降运动特征,结合圆弧滑动法计算土体内部剪应力和正应力,得到滑动力矩。结合其他边坡稳定性影响因素,利用模糊综合评估法进行边坡稳定性分析,按照最大隶属度原则生成稳定性分析结果。仿真试验结果表明:该方法应用下,相比其他方法,土体表面应力数据结果拟合度提升了23.86%、29.55%与43.18%。

基于参数辨识的变压器绕组变形在线监测方法

变压器绕组变形导致的内部匝间故障已经上升至事故率的首位,对电网安全性危害极大。为此,提出一种变压器绕组变形在线监测工程方法。利用以傅里叶为理论基础的动态向量模型,在保持高精度的条件下简化变压器电磁暂态模型,并讨论不同运行状态下模型参数辨识解的个数。当变压器空载合闸时辨识出绕组电阻参数,在变压器稳态运行时利用已辨识出的电阻参数修改参数辨识模型,并辨识漏感参数。利用绕组变形与漏电感参数之间的关系,实现对变压器绕组变形在监测。建立了变压器绕组变形的仿真模型,使用有限元方法计算变压器绕组变形的短路电感值,验证了变压器绕组在线监测方法的有效性。

刚-柔耦合多体系统动力学建模与数值仿真

柔性多体系统动力学传统的混合坐标建模方法忽略了变形位移的高次耦合变形量 ,是一种零次近似方法 [1 ] ,其适用范围受到限制。本文以中心刚体、柔性梁及末端质量组成的刚柔耦合系统为对象 ,考虑了有粘性阻尼及风阻的情况。在柔性梁的纵向变形位移中计及了横向位移引起的轴向变形 ,并采用有限元方法和 Hamilton变分原理导出了系统的刚柔耦合一次近似的动力学方程。该方程充分计及了中心刚体的大范围运动与柔性梁的弹性变形运动的相互耦合 ,并采用一致的方法引入了阻尼因素。文中最后提供了一个比“动力刚化”问题更具有一般性的仿真计算反例 ,进一步说明了零次近似方法在处理某些刚 -柔耦合动力学问题时的缺陷 。

板坯连铸结晶器内温度/应力场耦合模型

考虑结晶器铜板中水槽的结构尺寸和分布、结晶器锥度对铸坯温度场和变形的影 响,建立了连铸结晶器内热和应力状态的有限元耦合分析模型。利用该模型模拟了结晶器内 钢水凝固过程温度分布和铜板的热机械变形,结果与实际符合较好.

导洞隔离桩墙结构对浅埋暗挖隧道周边地层移动的限制作用

以北京城市铁路某浅埋暗挖区间隧道工程为例,分析了导洞隔离桩墙结构对中洞法双连拱隧道施工变形影响的限制作用。由于地面环境的制约,该工程在隧道侧上方开挖了两个小断面导洞,采用喷混凝土衬砌,并在导洞内向下施作钢筋混凝土排桩,以隔离隧道施工对附近两座高层建筑的不良影响。在分析导洞隔离桩墙工作机理的基础上,提出了一种解析解来估算隔离结构及附近地层的变形情况,并对施工过程的变形影响进行了三维有限元模拟。把解析解和有限元计算结果与施工监测数据进行了比较,总结了影响隔离结构作用效果的关键因素。

反倾岩质边坡变形破坏的节理有限元模拟计算

岩质边坡的倾倒破坏是地质环境中广泛存在的现象,通过模拟手段对边坡的响应规律进行科学准确预测显得尤为重要。采用基于强度折减法的节理有限元法(JFEM-SSR)对反倾层状边坡的变形破坏机制进行研究,该方法可同时考虑岩块和节理属性,并能充分体现岩层或岩块接触作用的非线性关系,在获得边坡应力、位移及塑性区的同时可以到边坡的稳定系数。首先,采用JFEM对R.E.Goodman和J.W.Bray提供的一个倾倒破坏的算例进行了模拟计算,证实该法应用于节理岩石边坡稳定性分析的合理性;然后,基于该方法,采用节理网络模型建立广乐高速公路一桥墩承台开挖边坡的地质模型,对其变形破坏机制及稳定性影响因素进行研究,重点探讨地下水渗流作用、地震作用、岩层倾角、岩面厚度对边坡变形破坏的影响,以便为工程决策提供依据。

织物变形的物理仿真技术

基于物理的仿真模型是织物变形仿真技术的主流 .文中对基于物理的织物变形仿真模型进行了综述 .首先 ,把模型分为两类 :一类是离散质点型模型 ,一类是连续介质型模型 .其次 ,评述了各种模型 ,分析了其优缺点 ,并对各种算法的效率进行了比较 .最后 ,对织物变形物理的仿真的发展方向提出了一些看法 ,特别强调了发展有限元模型 .