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。     

基于有限元分析的笔记本纸浆模塑包装方案研究

目的 设计出一款低重量、高栈板量的笔记本电脑纸浆模塑(简称纸塑)包装方案,预估及验证新方案在跌落测试中对电脑的保护性。方法 结合现有内翻和外翻纸塑方案各自结构的优势,设计出一种V型纸塑方案。基于跌落试验工况建立跌落仿真模型,通过ANSYS/LS-Dyna进行仿真分析,得到产品跌落加速度曲线和纸塑开裂变形图,并进行测试验证。结果 V型方案在端面、顶面和短棱跌落的加速度均低于原内翻方案,各工况下V型方案无明显开裂,仿真分析与跌落测试结果高度一致。结论 V型方案可在跌落测试中对电脑提供充分保护,满足落地条件,具有巨大的经济价值。有限元分析结果精度较高,可为各机型纸塑包装的开模定形提供依据,降低修模风险。     

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。     

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.     

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.     

Dispersion analysis and error estimation of Galerkin finite element methods for the Helmholtz equation

When applying numerical methods for the computation of stationary waves from the Helmholtz equation, one obtains ‘numerical waves’ that are dispersive also in non-dispersive media. The numerical wave displays a phase velocity that depends on the parameter k of the Helmholtz equation. In dispersion analysis, the phase difference between the exact and the numerical solutions is investigated. In this paper, the authors' recent result on the phase difference for one-dimensional problems is numerically evaluated and discussed in the context of other work directed to this topic. It is then shown that previous error estimates in H¹-norm are of nondispersive character but hold for medium or high wavenumber on extremely refined mesh only. On the other hand, recently proven error estimates for constant resolution contain a pollution term. With certain assumptions on the exact solution, this term is of the order of the phase difference. Thus a link is established between the results of dispersion analysis and the results of numerical analysis. Throughout the paper, the presentation and discussion of theoretical results is accompanied by numerical evaluation of several model problems. Special attention is given to the performance of the Galerkin method with a higher order of polynomial approximation p(h-p-version).     

Fracture mechanics analysis using the wavelet Galerkin method and extended finite element method

This paper presents fracture mechanics analysis using the wavelet Galerkin method and extended finite element method. The wavelet Galerkin method is a new methodology to solve partial differential equations where scaling/wavelet functions are used as basis functions. In solid/structural analyses, the analysis domain is divided into equally spaced structured cells and scaling functions are periodically placed throughout the domain. To improve accuracy, wavelet functions are superposed on the scaling functions within a region having a high stress concentration, such as near a hole or notch. Thus, the method can be considered a refinement technique in fixed‐grid approaches. However, because the basis functions are assumed to be continuous in applications of the wavelet Galerkin method, there are difficulties in treating displacement discontinuities across the crack surface. In the present research, we introduce enrichment functions in the wavelet Galerkin formulation to take into account the discontinuous displacements and high stress concentration around the crack tip by applying the concept of the extended finite element method. This paper presents the mathematical formulation and numerical implementation of the proposed technique. As numerical examples, stress intensity factor evaluations and crack propagation analyses for two‐dimensional cracks are presented. Copyright © 2012 John Wiley & Sons, Ltd.     

An Abaqus implementation of the extended finite element method

In this paper, we introduce an implementation of the extended finite element method for fracture problems within the finite element software ABAQUS^TM. User subroutine (UEL) in Abaqus is used to enable the incorporation of extended finite element capabilities. We provide details on the data input format together with the proposed user element subroutine, which constitutes the core of the finite element analysis; however, pre-processing tools that are necessary for an X-FEM implementation, but not directly related to Abaqus, are not provided. In addition to problems in linear elastic fracture mechanics, non-linear frictional contact analyses are also realized. Several numerical examples in fracture mechanics are presented to demonstrate the benefits of the proposed implementation.     

Applications of linear inverse finite element method in prediction of the optimum blank in sheet metal forming

A linear inverse finite element method has been developed and investigated to predict the optimum blank. To reduce the computation time, the part is unfolded properly on the flat sheet and treated as a 2D problem. This approach is employed primarily to design the optimum blank shape from the desired final shape with the linear formulations. The procedure is based on the minimization of energy for the unfolded elements. Two solution methods, Direct and Newton–Raphson methods have been examined for the solution of nodal displacements in the equilibrium equations. The convergence show high sensitivity to the initial guess for the strain path when assumed to be linear at the first step. Two applied examples are implemented to show the efficiency of this method. In S rail example, the thickness distributions have been compared with experimental analysis after obtaining the optimum blank with Linear IFEM. In circular cup example, the results have been compared with conventional forward incremental method. New calculation of the external forces vector has been displayed. In this calculation, both blank holder force (BHF) vector and in-plane force vector have been shown. Finally, in this approach good agreement was found between the forward incremental and Linear IFEM results.     

基于声辐射逆问题的故障诊断与噪声分析的研究

本文采用全特解场边界元求解声辐射逆问题的方法,通过对故障诊断和噪声源分析、相位分析、声环境设计的仿真计算与讨论,初步揭示了声源与其所发生声场的逆关系。计算结果可为噪声控制、故障诊断、声环境设计等工程实际应用提供有价值的参数。     

用三维有限元求解金属淬火过程的换热系数

在金属淬火过程的数值模拟中,换热系数的正确求解是工件温度场、应力/应变场模拟结果与实际相符合的先决条件.据此研究和分析了换热系数反求法的数学模型,分别采用一维和三维有限元法对该数学模型求解.研究表明:与采用一维有限差分的求解法相比较,计算过程由一维有限元法增加到三维有限元法,与实际情况更为接近;用有限元方法求解的换热系数曲线连续且平滑,结果可靠,且编程量小;用求得的换热系数计算金属淬火试件的中心温度场变化曲线,计算结果与实测数据相吻合.     

Natural frequencies of cracked functionally graded material plates by the extended finite element method

In this paper, the linear free flexural vibration of cracked functionally graded material plates is studied using the extended finite element method. A 4-noded quadrilateral plate bending element based on field and edge consistency requirement with 20 degrees of freedom per element is used for this study. The natural frequencies and mode shapes of simply supported and clamped square and rectangular plates are computed as a function of gradient index, crack length, crack orientation and crack location. The effect of thickness and influence of multiple cracks is also studied.     

Mechanical analysis of 3-D braided composites by the finite multiphase element method

A finite multiphase element method (FMEM), in which the element comprises more than one kind of material, has been proposed to predict the effective elastic properties of 3-D braided composites. This method is based on the variational principle and our previous geometric model that assumes the existence of different types of unit cells in the three regions in a 3-D braided composite, i.e. the interior, surface and corner. The numerical procedure involved two steps. First, a fine local mesh at the unit cell level is used to analyze the stress/strain of each unit cell. Then, a relatively coarse global mesh is used to obtain the overall responses of the composite at macroscopic level. By using the stress volume averaging method, the effective elastic properties of the composite can be calculated under the prescribed uniform strain boundary conditions. Finally, the predicted stress/strain curves are compared with experimental results, demonstrating the applicability of the FME method.