用数字相关测量方法研究纸浆模塑材料拉伸时的力学性能

研究纸浆模塑材料的力学性能,包括纸浆模塑材料拉伸时弹性模量、泊松比等参数的检测,从而为纸浆模塑缓冲包装结构的有限元分析和设计打下基础.由于纸浆模塑材料单向拉伸时横向变形非常小且不宜采用接触式应变测量方法,变形测量比较困难,所以文中将数字相关测量技术应用于横向变形的测量,较好地解决了纸浆模塑材料的横向变形系数测量问题.     

手机纸浆模塑包装热压定型模具有限元分析

建立手机纸浆模塑包装热压定型模具模型,使用有限元分析软件对其在特定条件下进行了结构分析.讨论了有限元分析中的前置处理及分析结果,对有限元分析云图中出现的局部应力集中、位移量较大的区域进行优化,同时对多余的材料浪费进行外削减.改进后的阴模、阳模结构材料更省、结构更合理,证明有限元分析对结构优化效果明显.     

手机用纸浆模塑盒的有限元分析

分析了纸浆模塑制品在包装应用中的缓冲机理,并将有限元方法引入到纸浆模塑材料的强度分析中,针对手机包装用纸浆模塑盒进行了有限元分析.结果表明,盒体结构强度及缓冲性能足够,产品能够得到有效保护.     

机电产品用纸浆模塑衬垫的有限元分析

在机电产品的纸浆模塑衬垫设计中,利用ANSYS软件进行有限元分析,研究静载作用下的衬垫受力及变形情况.结果表明,衬垫结构强度及缓冲性能良好,产品能够得到有效保护.     

纸浆模塑材料在不同加载条件下的力学特性

实验测量了纸浆模塑材料在不同加载条件下拉伸时的强度极限、弹性模量和泊松比等力学性能,同时给出了纸浆模塑材料的应力-应变曲线,为纸浆模塑缓冲包装结构的有限元分析和设计提供了基础数据.实验结果表明:当加载速率提高时,试件强度极限和弹性模量随之增加;当温度升高时,纸浆模塑材料的强度极限和弹性模量随之逐渐升高;当湿度升高时,纸浆模塑的强度极限和弹性模量随之降低.纸浆模塑材料单向拉伸时横向变形很小,且对温、湿度等环境因素影响敏感,泊松比的测量比较困难.数字图像相关测量方法具有灵敏度高、非接触、直接测量物体表面全场变形的特点,采用该测量方法解决了材料泊松比的测量问题.实验测得纸浆模塑材料泊松比为0.097.     

层叠式纸浆模塑平托盘结构设计与性能分析

在分析原有纸浆模塑托盘结构的不足的基础上,设计出层叠式纸浆模塑托盘。利用有限元法对静载和叉车作业进行了仿真,得到了托盘的变形和应力分布云图。仿真结果表明:与单层式托盘相比,新型托盘较好地解决了应力集中的问题,使载荷分布更加均匀,提高了承载能力,减小了变形量,降低了各向力学性能的差异。另外,层叠式托盘降低了单层厚度,易于干燥。     

纸浆模塑托盘构型三维设计及支腿结构 CAE 分析

运用 Pro/ E 软件对纸浆模塑托盘构型进行了三维设计,完成了托盘支腿和面板的零部件建模及相应的装配。 运用 ABAQUS 有限元分析软件对托盘支腿结构进行了强度计算,模拟分析了纸浆模塑托盘支腿在压缩载荷作用下的弹塑性变形,得到了模型受载变形全过程的载荷-位移曲线,从而确定了支腿的承载能力。     

纸浆模塑材料性能的研究现状和开发应用

介绍了国内外纸浆模塑材料性能的研究现状,重点论述了纸浆模塑材料的优点和开发应用,同时对今后纸浆模塑材料研究的发展方向提出了展望.     

纸浆模塑托盘支腿单元承载能力的数值分析

应用ABAQUS有限元软件,模拟分析了纸浆模塑托盘支腿在压缩载荷作用下的非线性变形特征和屈曲行为。通过建立简化的托盘支腿模型,设置不同壁厚,对各模型进行了有限元非线性屈曲分析,得到了模型受载变形全过程的力-位移曲线。结果显示,支腿最大承载能力随壁厚增加而增大,支腿承载能力取决于支腿壁厚区间。     

基于共振测量和有限元仿真的材料常数识别

利用共振测量和有限元仿真计算，在一个以材料弹性常数为控制变量的非线性优化过程中，极小化测量与计算了圆柱形试件的固有频率，从而间接地识别出各向异性合金材料的弹性常数，给出铁基合金PM2000在室温以及镍基单晶合金CMSX6，CMSX4，SSR99和MC2和20－1200℃温区弹性常数的识别结果。     

Using finite element analysis/optimum design in the determination of elastic constants by vibration testing

Abstract

Combining vibration testing and numerical methods is a potential alternative approach for determining elastic constants of materials because of nondestructive testing, single testing, and producing average properties. In order to simplify the modeling processes and to reduce complicated derivations in the numerical method, the combination of finite element analysis and optimum design is adopted in this work to inversely calculate the elastic constants. In this method, the effects of some parameters, including the finite element mesh, the mode number, constraints on state variables, the optimization method, and initial values and loops, are discussed. It is proved that the present method with 10×10 mesh, 6 vibration modes, 5% constraint on state variables, and subproblem approximation can obtain accurate results. Average values can be used to avoid the scatter in results due to different initial values, and do‐loops may not be necessary. It is also clearly demonstrated that the present method can correctly extract 2 or 5 elastic constants for isotropic or orthotropic materials.     

基于有限元分析的复杂结构弹性振动传递函数建模

为了解决复杂结构的弹性振动建模问题,提出了一种基于有限元分析的弹性振动传递函数建模方法。首先建立能够准确反映结构动力学特性的有限元模型;然后根据输入参数和辨识算法类型的不同,分别从时域和频域两方面进行传递函数建模,其中时域辨识建模以PRBS信号的瞬态响应结果为辨识数据进行时域参数辨识,频域辨识建模以结构的频率响应函数为辨识数据进行频域参数辨识;最后以“时域建模频域验证,频域建模时域验证”的方法检验传递函数的精度。通过建立悬臂梁、某运载火箭和某弹体局部结构的传递函数模型,证明了该方法的可行性和有效性,为该方法在工程实践中的应用提供参考。     

Equilibrium of an elastic finite cylinder: Filon's problem revisited

This paper deals with an analytical solution of the axisymmetric boundary-value problem of the theory of elasticity for a finite circular cylinder with free ends and arbitrary loaded curved surface. The object of this paper is to employ the method of superposition to obtain accurate values of the stress field near the boundaries. The classical Filon (1902) problem of uniformly distributed tangential load applied along two rings at the curved surface is addressed in full detail. The distribution of stresses along some typical sections of the cylinder are shown graphically.     

An inverse problem in estimating interfacial cracks in bimaterials by boundary element technique

An inverse elasticity problem by utilizing both the regularization method (RM) and the conjugate gradient method (CGM) is presented for estimating the interfacial cracks (including location and shape) of a bimaterial from the measurement of displacements at discrete locations internal to the domain and parallel to the interface. The present algorithm in determining the interfacial cracks is totally different from the conventional one. The comparisons of using the conjugate gradient method and commonly used regularization method are discussed systematically, moreover, the advantages and disadvantages in applying the large matrix (LM) and small matrix (SM) formulations are also examined. To the author's knowledge the present work is the first of its kind. Finally, the effects of the measurement errors on the inverse solutions are discussed. Results show that the present inverse algorithms are not sensitive to measurement errors. The CGM is recommended because it is straightforward, LM formulation is better than SM formulation without the consideration of computer time. Copyright © 1999 John Wiley & Sons, Ltd.     

Iterative solution of the random eigenvalue problem with application to spectral stochastic finite element systems

A new algorithm for the computation of the spectral expansion of the eigenvalues and eigenvectors of a random non‐symmetric matrix is proposed. The algorithm extends the deterministic inverse power method using a spectral discretization approach. The convergence and accuracy of the algorithm is studied for both symmetric and non‐symmetric matrices. The method turns out to be efficient and robust compared to existing methods for the computation of the spectral expansion of random eigenvalues and eigenvectors. Copyright © 2006 John Wiley & Sons, Ltd.     

Numerical simulation of elastic plastic fatigue crack growth in functionally graded material using the extended finite element method

In the present work, the extended finite element method has been used to simulate the fatigue crack growth problems in functionally graded material in the presence of holes, inclusions, and minor cracks under plastic and plane stress conditions for both edge and center cracks. Both soft and hard inclusions have been implemented in the problems. The validity of linear elastic fracture mechanics theory is limited to the brittle materials. Therefore, the elastic plastic fracture mechanics theory needs to be utilized to characterize the plastic behavior of the material. A generalized Ramberg-Osgood material model has been used for modeling purposes.     

The mixed finite element method for the quasi‐static and dynamic analysis of viscoelastic timoshenko beams

The quasi‐static and dynamic responses of a linear viscoelastic Timoshenko beam on Winkler foundation are studied numerically by using the hybrid Laplace–Carson and finite element method. In this analysis the field equation for viscoelastic material is used. In the transformed Laplace–Carson space two new functionals have been constructed for viscoelastic Timoshenko beams through a systematic procedure based on the Gâteaux differential. These functionals have six and two independent variables respectively. Two mixed finite element formulations are obtained; TB12 and TB4. For the inverse transform Schapery and Fourier methods are used. The numerical results for quasi‐static and dynamic responses of several visco‐elastic models are presented. Copyright © 1999 John Wiley & Sons, Ltd.     

Automatic image‐based stress analysis by the scaled boundary finite element method

Digital imaging technologies such as X‐ray scans and ultrasound provide a convenient and non‐invasive way to capture high‐resolution images. The colour intensity of digital images provides information on the geometrical features and material distribution which can be utilised for stress analysis. The proposed approach employs an automatic and robust algorithm to generate quadtree (2D) or octree (3D) meshes from digital images. The use of polygonal elements (2D) or polyhedral elements (3D) constructed by the scaled boundary finite element method avoids the issue of hanging nodes (mesh incompatibility) commonly encountered by finite elements on quadtree or octree meshes. The computational effort is reduced by considering the small number of cell patterns occurring in a quadtree or an octree mesh. Examples with analytical solutions in 2D and 3D are provided to show the validity of the approach. Other examples including the analysis of 2D and 3D microstructures of concrete specimens as well as of a domain containing multiple spherical holes are presented to demonstrate the versatility and the simplicity of the proposed technique. Copyright © 2016 John Wiley & Sons, Ltd.     

Numerical modelling of elastic wave scattering in frequency domain by the partition of unity finite element method

In this paper, we investigate a numerical approach based on the partition of unity finite element method, for the time‐harmonic elastic wave equations. The aim of the proposed work is to accurately model two‐dimensional elastic wave problems with fewer elements, capable of containing many wavelengths per nodal spacing, and without refining the mesh at each frequency. The approximation of the displacement field is performed via the standard finite element shape functions, enriched by superimposing pressure and shear plane wave basis, which incorporate knowledge of the wave propagation. A variational framework able to handle mixed boundary conditions is described. Numerical examples dealing with the radiation and the scattering of elastic waves by a circular body are presented. The results show the performance of the proposed method in both accuracy and efficiency. Copyright © 2008 John Wiley & Sons, Ltd.     

Investigations on boundary temperature control analysis considering a moving body based on the adjoint variable and the fictitious domain finite element methods

This paper presents an examination of moving‐boundary temperature control problems. With a moving‐boundary problem, a finite‐element mesh is generated at each time step to express the position of the boundary. On the other hand, if an overlapped domain, that is, comprising foreground and background meshes, is prepared, the moving boundary problem can be solved without mesh generation at each time step by using the fictitious domain method. In this study, boundary temperature control problems with a moving boundary are formulated using the finite element, the adjoint variable, and the fictitious domain methods, and several numerical experiments are carried out. Copyright © 2015 John Wiley & Sons, Ltd.