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粘塑性材料成形过程的有限元分析 总被引:1,自引:0,他引:1
为了确定大型铝机轮等温锻造的变形力及揭示轮缘处形成折叠的原因,本文用刚一粘塑性有限元法对模拟件的成形过程进行了全面数值模拟。模拟计算和实验结果表明,有限元确定的等温锻造过程的变形力,可作为选择设备吨位的依据,根据刚-粘塑性有限元法所预测的金属流动规律,发现零件的形状很大程度上决定了轮缘处容易形成折叠。适当改进模具结构和改善润滑条件,有助于避免折叠缺陷的产生。 相似文献
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In this work, the finite element analysis of the elasto-plastic plate bending problems is carried out using transition rectangular plate elements. The shape functions of the transition plate elements are derived based on a practical rule. The transition plate elements are all quadrilateral and can be used to obtain efficient finite element models using minimum number of elements. The mesh convergence rates of the models including the transition elements are compared with the regular element models. To verify the developed elements, simple tests are demonstrated and various elasto-plastic problems are solved. Their results are compared with ANSYS results.The English text was polished by Keren Wang. 相似文献
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脱层是复合材料层板结构中主要的缺陷形式之一。当脱层层板受到压力载荷的作用会造成脱层的局部屈曲和扩展,从而使结构的强度和刚度大为降低。含脱层层板的弯曲问题包含了脱层的压缩问题,却比压缩问题更加复杂。本文对含穿透脱层层板在纯弯载荷作用下的后屈曲问题进行了基于一阶剪切层板理论的几何非线性有限元分析,运用虚裂纹闭合技术求解了纯弯载荷作用下的脱层尖端的能量释放率各型分量,并用脱层扩展判据求解了脱层起始扩展载荷。 相似文献
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本文根据实际复杂工程结构独立随机变量多,计算工作量大的特点,提出了用广义随机变量替代一般的独立随机变量以减少基本随机变量的数目,用响应曲面法替代敏度法或摄动法以提高计算效率。算例证明,以上措施取得了良好的效果,有助于非线性随机有限元法在实际工程结构可靠性分析中的应用。 相似文献
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为提高功能梯度板动响应问题求解精度,基于一阶剪切变形板理论,提出了求解功能梯度板自由振动问题的Cell-Based 光滑有限元格式.功能梯度板材料属性沿厚度方向呈梯度连续变化,计算系统刚度矩阵时在光滑域内进行光滑梯度操作,可提高求解精度.采用Cell-Based 光滑有限元法,讨论了长厚比、形状因子和边界条件对两种典型功能梯度方板无量纲频率参数的影响,并与FEM法的解和文献中的解做了对比.数值算例的结果表明,光滑梯度操作可改善有限元系统的刚度,Cell-Based 光滑有限元法的计算结果更加逼近真实解,从而为功能梯度材料的进一步应用打下基础. 相似文献
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一种考虑剪切变形的平行四边形厚/薄板通用单元 总被引:2,自引:0,他引:2
根据Timoshenko二广义位移梁理论,构造了深梁位移场的插值函数。利用斜坐标系与直角坐标系的变换关系、有限条带思想和深梁位移插值函数,构造了一种考虑剪切变形的平行四边形厚/薄板弯曲通用单元的位移(曲率、剪应变、转角、横向位移)插值函数,导出了刚度矩阵和非结点荷载等效力。并对简支阍支方板、Razzaque斜板、四边简支斜交板弯曲进行了数值计算。算例表明此单元有较好的精度,对于薄板不出现剪切闭锁,可适应于目前桥梁建设中大量采用的斜交板桥结构分析。 相似文献
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In this paper, a circumferential external surface flaw in a metallic round pipe under cyclic bending loading is considered.
Because of very rapid changes in the geometrical parameters around the crack front region, the mesh generation of this region
must be done with great care. This may lead to an increase in the run time which makes it difficult to reach valid results
and conclusions. Because of the advantages of the sub-modeling technique in problems which need very high mesh density, this
method is used. Stress intensity factors in mode I condition are determined using three-dimensional finite element modeling
with 20 node iso-parametric brick elements in the ANSYS 9.0 standard code and the singular form of these finite elements at
the crack front. In order to estimate the analysis error, the structural parameter error in energy norm criterion was used.
Because of the advantages of non-dimensional analysis, this method is employed, and the stress intensity factors are normalized.
For the analysis of the fatigue crack growth, the Paris law is used. The propagation path of the surface flaw is obtained
from the diagram of aspect ratio versus relative crack depth. The fatigue crack growth analysis (the relative crack depth
against loading cycles diagram) of different initial crack aspect ratio under cyclic loading is also considered. Fatigue shape
development of initially semi-elliptical external surface defects is illustrated. The effect of the Paris exponent (material
constant) on fatigue crack propagation is shown as well. Moreover, the fatigue crack growth of several specimens is assessed
experimentally using a manually-constructed experimental set up. Finally, the experimental results obtained by cyclic bending
loading tests are compared with the numerical results. The experimental results show good conformity with the finite element
results. 相似文献
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用样条有限条塑性铰法分析了板梁的极限荷载。首先对条单元以样条位移函数表达的总势能进行求导而推导了位移-荷载关系式。然后用塑性铰法推导了单元的塑性刚度矩阵。因此该方法兼具二者优点:样条有限条法的位移量少和塑性铰法形成塑性刚度矩阵的便利。它还可以考虑梁的初始缺陷,如残余应力和初弯曲。通过与相关的试验数据比较,证明该方法有效与可靠。 相似文献
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A uniaxial tension sheet metal coupon with a tapered instead of a straight gage section has been used for centering the location
of diffuse neck and for measuring sheet stretchability in a non-uniform strain field. A finite element analysis of such a
tensile coupon made of automotive steel sheet metals has been carried out to assess the effect of the tapered gage section
geometry and material plastic strain hardening characteristics on the development of local plastic deformation pattern and
local stress state, especially beyond the onset of diffuse necking but before localized necking. In particular, the finite
element analysis was used in this study to evaluate the accuracy and reliability of an experimental data analysis method for
estimating the post-necking effective plastic stress-strain curve based on the direct local surface axial plastic strain measurements
for base metal, heat-affected zone, and weld metals of a dual-phase steel DP600. It is concluded that the estimated lower
and upper bounds of the effective stress-strain curve at large strains are not satisfactory for low strain-hardening materials
such as heat-affected zone and weld metals with the tapered tension coupons. A simple correction method utilizing only the
additional local surface strain measurement in the transverse direction is proposed and it is shown to be effective in correcting
the estimated effective stress-strain curve of dual-phase steel weld metals obtained for two tapered gage section geometries. 相似文献
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为验证鸟撞有机玻璃平板数值计算模型的正确性,同时为进一步设计研制具有高抗鸟撞能力的航空有机玻璃风挡提供有价值的数据,本文采用动态数据采集系统,对YB3航空有机玻璃平板在两种不同速度下的鸟体撞击动态响应全过程进行了详细研究。测量了YB3平板上三个点的位移、七个点的应变、鸟体撞击方向四个支反力等物理量随时间的变化历程,同时利用高速摄像系统记录了鸟体撞击下平板动态变形和破坏的全过程。分析了鸟撞实验结果的有效性,同时分析了有机玻璃被鸟体击穿后的破坏模式。重复性实验结果的一致性表明了本文实验测试结果的有效性和可靠性。 相似文献
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A fully coupled formulation combining reactive transport and an existing thermo-hydro-mechanical (THM) code is presented.
Special attention has been given to phenomena likely to be encountered in clay barriers used as part of containment systems
of nuclear waste. The types of processes considered include hydrolysis, complex formation, oxidation/reduction reactions,
acid/base reactions, precipitation/dissolution of minerals and cation exchange. Both kinetically-controlled and equilibrium-controlled
reactions have been incorporated. The total analytical concentrations (including precipitated minerals) are adopted as basic
transport variables and chemical equilibrium is achieved by minimizing Gibbs Free Energy. The formulation has been incorporated
in a general purpose computer code capable of performing numerical analysis of engineering problems. A validation exercise
concerning a laboratory experiment involving the heating and hydration of an expansive compacted clay is described. 相似文献
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聚合物熔体在模具中的均匀性决定板材成型的质量。熔体具有非线性记忆性的粘弹效应,同时流道十分复杂。为准确、简便地分析熔体流动情况,针对板材机头流道的特点,提出了流动计算新的方法——有限柱半解析法,即在流道的厚度方向采用富氏级数描述流动分布,把三维有限元方程简化成为二维,得到以流量和压力为未知量的有限元方程。同时采用K-BKZ积分型本构模型描述熔体的非线性记忆性,给出求解非线性方程组的迭代方法,取得较好的收敛性。对两种典型的板材模具进行了分析计算,得出模具出口处的流量分布,通过把结果与三维有限元分析的结果相比较,表明该方法可以准确地分析板材模具中熔体的流动。 相似文献
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板壳结构弹塑性稳定性的有限元分析 总被引:2,自引:0,他引:2
构造了20参数圆柱壳拟协调单元,同时采用分层模型的弹塑性稳定性分析.根据塑性屈曲的Stowell形变理论,用基于切线刚度矩阵的增量法和修正的Newton-Raphson方法,计算屈曲前的弹塑性内力分布,并用逆幂迭代法求解弹塑性屈曲荷载. 相似文献
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根据能量原理,引入大挠度Von-Karman方程,求解了应力不连续简支板的屈曲问题,得到了临界载荷和临界应力计算系数. 相似文献
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阻尼夹层筋板结构有限元动力分析 总被引:6,自引:2,他引:6
在小变形线弹性理论基础上,导出了粘弹性阻尼夹层筋板壳结构的有限元动力方程,构造了壳单元、阻尼夹层壳单元和开口薄壁梁单元。采用这些单元可以很好地模拟具有不连续阻尼夹层处理的筋板壳结构。数值分析采用[3]中提出的两次渐近法。通过一块阻尼加筋板的特征分析和振动测量,证实了所建立的有限元两次渐近法的良好精度和广泛的工程适用性。 相似文献