复合分子泵转子离心变形与热变形的有限元分析

本文利用有限元分析软件ANSYS12.0对复合分子泵转子的离心变形与热变形进行了分析。通过施加惯性载荷和温度载荷,得到转子的离心变形与热变形。对不同载荷下分析结果的比较,了解了惯性载荷与温度载荷对分子泵转子变形影响大小。通过分析结果可直观了解分子泵在高速运转过程中转子变形情况,对分子泵设计时工作间隙的选取有重要的参考意义。     

论高层建筑物的变形监测与精度分析

变形对高层建筑物的安全影响是非常大的,所以,变形监测就显得非常重要。本文以高层建筑物静态变形监测为对象,首先,分析了高层建筑物变形监测的种类,并探讨了变形监测方案的设计思路,探讨了观测周期的确定方法,在此基础上,探讨了建筑变形监测的具体方法和精度分析。     

变形观测中建筑物变形判定的探讨

变形观测中,建筑物变形的几何分析尤为重要,而判定观测点是否有变动则需要将变形量与变形量中误差进行比较,但是多数的平差软件没直接计算变形量中误差。本文中作者由普通平差软件平差结果中的高程中误差、误差椭圆数据推算变形量中误差,并通过工程实例计算、分析,对建筑物几何变形进行了判定,为同行的变形观测几何分析提供了参考。     

TC4钛合金高温压缩变形行为的研究

采用等温压缩试验法,分析了TC4合金在高温低速变形过程中变形温度、应变速率对变形抗力及组织的影响,并通过回归分析得出了该合金高温变形过程中的流变应力方程,为TC4热变形工艺的制定提供参考依据。     

刍议焊接变形的危害及其防治措施

文章分析了结构焊接变形的产生及其危吾,提出了防止焊接变形的具体措施以及焊接变形的矫正方法。     

纤维缠绕壳体变形分析及失效评估

本文分析计算了基体开裂及大变形对纤维缠绕壳体变形的影响,得到了比较满意的理论分析结果。在变形分析的同时,对纤维缠绕壳体进行了失效评估分析,获得了切实可行的失效评估计算分析方法,为制定合理的水压检验规范提供了理论依据。     

深基坑开挖的大变形有限元分析

本文建立了基于初始构形的大变形增量有际元方程，讨论了非线性方程的求解过程，在此基础上，首次运用大变形理论对深基坑开挖过程中的大变形问题进行了研究，作为对比，也进行了相同材料模型下的小变形理论分析，通过了对比分析，从数值结果上分析了用小变形理论研究基坑变形问题时，可能会产生的误差，并以此定量地确定了大，小变形理论适用范围。     

大行程变形镜有限元分析

针对自适应光学系统对变形镜行程的更高要求,本文对提高变形镜行程技术进行了分析,提出了一种解决变形镜大行程的方法:匹配、优化变形镜的结构参数;利用有限元软件分析了该结构的各参数对变形镜主要性能指标:最大变形量、交连值及最大应力等的影响.根据分析结果,利用有限元分析方法对一自适应光学望远镜所用变形镜的镜面、驱动器结构参数进...     

三峡升船机塔柱施工期变形监测

从控制监测过程中的内部、外部要素以及现场作业条件着手,通过对几种典型监测方法精度分析及360°反射棱镜试验研究,最终选择全站仪极坐标法作为三峡升船机塔柱施工期变形监测的方法,并对运用该方法得到的长期监测数据成果进行了变形规律分析。分析结果表明:塔柱变形受温度影响大,温差越大,变形越大,温差小或恒温状态时变形很小甚至没有变形。     

常压低温液体容器破坏性变形分析与实例计算

对常压低温液体容器的受力与变形进行了分析,列出了在绝热与不绝热两种情况下,容器发生破坏性变形的条件。并结合一例液氮贮槽裸冷变形的实例进行计算与分析,指出在使用中应如何避免容器破坏性变形的发生。图5。     

有限元法中间构形初始解预示的Laplace-Beltrami方程法

一步有限元法具有高效的计算能力，在板料成形模拟方面得到了广泛的应用，但它存在应力计算精度不足的问题。为弥补这一不足，通过增加中间构形的方式，人们提出多步有限元法。而中间构形需根据初始解迭代计算获得，因此，初始解预示算法是多步有限元法的一个关键问题。该文把中间构形解耦分解为弯曲变形和拉伸变形两个独立的变形过程，且将弯曲变形作为中间构形的初始解预示，改善了多步有限元法的稳定性；并根据大位移小应变理论，建立了节点的位移约束条件；进一步，首次通过Laplace-Beltrami方程的建立和求解，实现了中间构形初始解的快速预示，该方法易于编程实现，稳定性好。通过典型零件数值算例的高效准确计算，验证了该算法的可行性和有效性。     

Electronic speckle pattern interferometry based on spatial fringe analysis method using two cameras

A new speckle measurement method is proposed by applying a spatial phase shifting method to multi-camera technology in order to perform a high resolution, high speed, and large deformation measurement. It is confirmed that the alignment of optical elements in this method is easier than the ordinary multi-camera methods because the optical system uses only two cameras. The validity of principle of the method is discussed by the results of experiments. It is shown that measurement precision of this method is about 1/50 wavelength in a small deformation measurement. Furthermore, the method is improved for a large deformation measurement method by accumulating the results of the small continuous deformation measurement. The optimum sampling process of the large deformation of an object is proposed in order to detect the phase map of the large deformation. It is confirmed that the large deformation can be precisely measured by this method.     

Mode I solution for micron-sized crack

The feature size of micro-electronic, optoelectronic and biomedical devices is in the sub-micron scale and is pushing toward the nanometer scale. Defects in these small structures are correspondingly smaller such that small crack behavior is becoming an important design consideration for reliability and performance of such devices. Analyses of small cracks are complicated by the rapid variation in the deformation in the crack tip zone. Strain gradients in the near tip zone, which can be ignored in large cracks, will influence the small crack behavior when the crack tip zone is in the order of the crack size. In this paper, we consider two-dimensional crack deformations with strain gradient effect and establish the dual formulations in terms of potentials. The formulations reduce to the conventional linear elastic fracture theory, when the material length scale parameters for the higher order deformation measures are zero. One of the formulations is in terms of two complex stress functions and two pseudo potentials. The complex stress functions are harmonic and the governing equations for the pseudo-potentials are two uncoupled second order partial differential equations. The solutions for these equations are coupled through the boundary conditions.A perturbation method is used to construct the solution for mode I cracks under a K-field when only the effect of the rotational gradient is included. The perturbation solution has induced singularity for the stresses. The induced deformation decays exponentially away from the crack tip. The induced stresses become insignificant beyond 3ε, the typical characteristics of a boundary layer type. To a first order approximation, the induced deformation energy normalized by that of the classical solution under constant applied crack opening load is linearly proportional to ε. This implies that the induced energy release rate is linearly proportional to the length scale parameter. The induced energy release rate under a fixed crack opening load is negative indicating that the rotational gradient shields the crack and lowers the total deformation energy release rate for small crack.     

桩基贯入过程中土体大变形分析与流动机理研究

土体大变形问题是海洋岩土工程界研究的难点,由于其变形梯度较大、流动机理复杂等特点,常规的岩土工程分析方法在求解该问题时表现出明显的局限性。因此,该文研究了求解土体大变形问题的解析方法,即Strain Path Method （SPM）和Shallow Strain Path Method （SSPM）,详细介绍了这两种方法的计算原理;并基于大、小应变理论,采用SSPM分析了理想土性条件下桩基础贯入过程中周围土体的流动机理和位移场变化规律;最后,将SPM和SSPM计算结果进行比较分析,阐明了两者之间的内在关系。基于大应变理论,采用SSPM计算得到的土体位移场与Sagaseta给出的结果具有较好的一致性,验证了计算结果的准确性。研究结果显示桩端上部土体会发生隆起现象,而桩端附近及底部土体具有下沉的位移,且在贯入深度位置处,土体下沉位移达到最大值。在径向位置r/R=3（距桩壁1倍直径）处,基于大、小应变理论计算结果具有较好的一致性。研究成果有助于了解土体的大变形特性,也可为数值计算结果的校验提供基本数据。     

A mortar formulation for 3D large deformation contact using NURBS-based isogeometric analysis and the augmented Lagrangian method

NURBS-based isogeometric analysis is applied to 3D frictionless large deformation contact problems. The contact constraints are treated with a mortar-based approach combined with a simplified integration method avoiding segmentation of the contact surfaces, and the discretization of the continuum is performed with arbitrary order NURBS and Lagrange polynomial elements. The contact constraints are satisfied exactly with the augmented Lagrangian formulation proposed by Alart and Curnier, whereby a Newton-like solution scheme is applied to solve the saddle point problem simultaneously for displacements and Lagrange multipliers. The numerical examples show that the proposed contact formulation in conjunction with the NURBS discretization delivers accurate and robust predictions. In both small and large deformation cases, the quality of the contact pressures is shown to improve significantly over that achieved with Lagrange discretizations. In large deformation and large sliding examples, the NURBS discretization provides an improved smoothness of the traction history curves. In both cases, increasing the order of the discretization is either beneficial or not influential when using isogeometric analysis, whereas it affects results negatively for Lagrange discretizations.     

初应力位形上附加变形线性理论的局限性及二次理论

初应力位形上附加变形线性理论的发展和应用受到附加变形微小性和零应力本构方程属超弹性固体的限制。尝试突破这种限制而建立一般理论。为此从连续介质力学理论出发,首先应用增量Lagrange 应力描写初应力位形上附加变形的控制方程和边界条件,然后利用量级分析的方法给出线性理论的适用范围和一个实用的改进方案棗二次理论,最后给出计算例对比二者的差异。结果表明二次理论成功的突破了线性理论的局限性而具有更大的适用范围和更高的精确性。     

圆柱壳几何大变形非线性频率求解的渐近摄动法

为解决圆柱壳在工作状态中由几何大变形而引起的弱非线性振动问题，将渐近摄动法引入求解考虑几何非线性的薄壁圆柱壳振动频率。首先，应用Donnell＇s简化壳理论获得了考虑几何大变形情况下具有位移三次项的非线性频率方程，把位移及频率以非线性参数的幂级数形式展开，并令同次幂的非线性项系数相等，由此得到非线性频率一次近似值与初始振幅的一系列耦合代数方程，引入Galerkin＇s方法对非线性频率方程进行解耦正交并忽略其中的永年项，考虑了对应实数根，各阶频率对应的振幅间不存在相互耦合的内共振现象，最终在引入小参数后用摄动法求出了非线性频率的一次近似解。计算结果表明，几何非线性使薄壁圆柱壳产生硬化，其非线性频率升高，并同时讨论了线性、非线性频率与节径数及初始位移之间的关系。     

B spline-based method for 2-D large deformation analysis

In this paper, quadratic cardinal B spline functions are used for solution of 2-D large deformation problems. Because the B spline functions are directly used in function approximation, no meshes are needed and the mesh distortion issues in nonlinear analyses are avoided in this method. Using the B spline functions, the solution formulations based on total Lagrangian (TL) approach for two dimensional large deformation problems are established. The numerical examples of 2-D large deformation problems indicate that the B spline method is effective and stable for solving complicated problems.     

软土地区侧压损失对盾构隧道受力及变形的影响

针对软土地区地铁沿线工程活动导致盾构隧道收敛变形增大的问题,采用1:10相似模型试验和精细化3D有限元模拟相结合的方法,研究了侧向压力损失对盾构隧道结构处于弹性阶段与塑性阶段的受力及变形的影响规律。研究结果表明:当侧向压力损失较小时,侧向压力损失与盾构隧道径向变形之间呈线性关系,盾构隧道结构处于弹性阶段;当侧向压力损失增大时,侧向压力损失与盾构隧道径向变形之间呈指数型关系,盾构隧道结构进入塑性阶段;增大管片厚度能有效提升管片的抗变形能力,但抗变形能力会随厚度增大而趋于平缓;从混凝土结构偏心受力的角度分析,盾隧道管片厚度增大会导致结构从小偏心受压向大偏心受压转变,但从结构应力/应变的角度分析,管片的最大应变值减小,从而使盾构隧道结构处于更安全的受力状态。     

Effect of Hot Deformation on Microstructure and Hardness of In-situ TiB2/7075 Composite

［1］P.Davies and J.L.F.Kellie: London and Scandinavian Co. Limited: Patent WO 93/05189, 1993. ［2］C.Bartels,D.Raabe,G.Gottstein and U.Huber:Mater. Sci. Eng., 1997, A237, 12.