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FEM-based strain analysis study for multilayer sheet forming process

Rongjing ZHANG,Lihui LANG,Rizwan ZAFAR

《机械工程前沿（英文）》 2015年 第10卷 第4期   页码 373-379 doi: 10.1007/s11465-015-0371-9

摘要：

Fiber metal laminates have many advantages over traditional laminates (e.g., any type of fiber and resin material can be placed anywhere between the metallic layers without risk of failure of the composite fabric sheets). Furthermore, the process requirements to strictly control the temperature and punch force in fiber metal laminates are also less stringent than those in traditional laminates. To further explore the novel method, this study conducts a finite element method-based (FEM-based) strain analysis on multilayer blanks by using the 3A method. Different forming modes such as wrinkling and fracture are discussed by using experimental and numerical studies. Hydroforming is used for multilayer forming. The Barlat 2000 yield criteria and DYNAFORM/LS-DYNA are used for the simulations. Optimal process parameters are determined on the basis of fixed die-binder gap and variable cavity pressure. The results of this study will enhance the knowledge on the mechanics of multilayer structures formed by using the 3A method and expand its commercial applications.

关键词： finite element method (FEM)     strain analysis     multilayer sheet forming    

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Fictitious soil pile model for dynamic analysis of pipe piles under high-strain conditions

《结构与土木工程前沿（英文）》   页码 915-934 doi: 10.1007/s11709-023-0907-8

摘要： A fictitious soil pile (FSP) model is developed to simulate the behavior of pipe piles with soil plugs undergoing high-strain dynamic impact loading. The developed model simulates the base soil with a fictitious hollow pile fully filled with a soil plug extending at a cone angle from the pile toe to the bedrock. The friction on the outside and inside of the pile walls is distinguished using different shaft models, and the propagation of stress waves in the base soil and soil plug is considered. The motions of the pile−soil system are solved by discretizing them into spring-mass model based on the finite difference method. Comparisons of the predictions of the proposed model and conventional numerical models, as well as measurements for pipe piles in field tests subjected to impact loading, validate the accuracy of the proposed model. A parametric analysis is conducted to illustrate the influence of the model parameters on the pile dynamic response. Finally, the effective length of the FSP is proposed to approximate the affected soil zone below the pipe pile toe, and some guidance is provided for the selection of the model parameters.

关键词： fictitious soil pile     soil plug     pipe piles     high-strain dynamic analysis     one-dimensional wave theory     pile dynamics    

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Vibration analysis of nano-structure multilayered graphene sheets using modified strain gradient theory

Amir ALLAHBAKHSHI,Masih ALLAHBAKHSHI

《机械工程前沿（英文）》 2015年 第10卷 第2期   页码 187-197 doi: 10.1007/s11465-015-0339-9

摘要：

In this paper, for the first time, the modified strain gradient theory is used as a new size-dependent Kirchhoff micro-plate model to study the effect of interlayer van der Waals (vdW) force for the vibration analysis of multilayered graphene sheets (MLGSs). The model contains three material length scale parameters, which may effectively capture the size effect. The model can also degenerate into the modified couple stress plate model or the classical plate model, if two or all of the material length scale parameters are taken to be zero. After obtaining the governing equations based on modified strain gradient theory via principle of minimum potential energy, as only infinitesimal vibration is considered, the net pressure due to the vdW interaction is assumed to be linearly proportional to the deflection between two layers. To solve the governing equation subjected to the boundary conditions, the Fourier series is assumed for w=w(x, y). To show the accuracy of the formulations, present results in specific cases are compared with available results in literature and a good agreement can be seen. The results indicate that the present model can predict prominent natural frequency with the reduction of structural size, especially when the plate thickness is on the same order of the material length scale parameter.

关键词： graphene     van der Waals (vdW) force     modi- fied strain gradient elasticity theory     size effect parameter    

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Adaptive selective ES-FEM limit analysis of cracked plane-strain structures

H. NGUYEN-XUAN,T. RABCZUK

《结构与土木工程前沿（英文）》 2015年 第9卷 第4期   页码 478-490 doi: 10.1007/s11709-015-0317-7

摘要： This paper presents a simple and efficient approach for predicting the plastic limit loads in cracked plane-strain structures. We use two levels of mesh repartitioning for the finite element limit analysis. The master level handles an adaptive primal-mesh process through a dissipation-based indicator. The slave level performs the subdivision of each triangle into three sub-triangles and constitutes a dual mesh from a pair of two adjacent sub-triangles shared by common edges of the primal mesh. Applying a strain smoothing projection to the strain rates on the dual mesh, the incompressibility constraint and the flow rule constraint are imposed over the edge-based smoothing domains and everywhere in the problem domain. The limit analysis problem is recast into the compact form of a second-order cone programming (SOCP) for the purpose of exploiting interior-point solvers. The present method retains a low number of optimization variables. It offers a convenient way for designing and solving the large-scale optimization problems effectively. Several benchmark examples are given to show the simplicity and effectiveness of the present method.

关键词： cracked structure     limit analysis     von Mises criterion     edge-based strain smoothing     second-order cone programming     adaptive    

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Bioleaching of spent Ni-Cd batteries and phylogenetic analysis of an acidophilic strain in acidified

ZHAO Ling, WANG Liang, YANG Dong, ZHU Nanwen

《环境科学与工程前沿（英文）》 2007年 第1卷 第4期   页码 459-465 doi: 10.1007/s11783-007-0073-6

摘要： Biohydrometallurgy is a novel method to recycle discarded batteries, in which sewage sludge is used as microorganisms and culture due to the presence of indigenous . A two-step continuous flow leaching system co

关键词： Biohydrometallurgy     discarded     indigenous     two-step continuous     presence    

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Construction of an immortalized neural progenitor cell strain and analysis of its immunogenicity

AN Ke, XU Ying, TIAN Xuebi, GAO Feng, TIAN Yuke, YANG Hui, ZHANG Chuanhan

《医学前沿（英文）》 2008年 第2卷 第1期   页码 63-69 doi: 10.1007/s11684-008-0012-3

摘要： Neural progenitor cells (NPC) are those that are the source of neural cells for cell transplantation and gene therapy. The shortage in quantity and the limited life spans of primary cultured cells limit its widespread use in basic research. Immortalized NPC, which also possess the capacity of self-renewal and can proliferate infinitely, can produce a large number of NPCs with stable phenotype and genotype. Here we report that an immortalized neural progenitor cell strain, which we named as INPC, was successfully established by gene-transfer of simian virus 40 large T antigen gene mediated by liposomes. The INPC retained the biological characteristics of its original cells and provided a safe and reliable cell platform for the treatment of central nervous system diseases and transgenic cell transplantation. INPC could express low levels of MHC antigens which was down-regulated after differentiation. This indicates that INPC possesses poor immunogenicity. The immortalized cells may show good long-term survival and do not elicit an acute immunological response following transplantation.

关键词： immortalized     long-term survival     differentiation     capacity     genotype    

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基于高等分析的钢结构设计——材料建模与应变极限 Research Article

Leroy Gardner, Xiang Yun, Andreas Fieber, Lorenzo Macorini

《工程（英文）》 2019年 第5卷 第2期   页码 243-249 doi: 10.1016/j.eng.2018.11.026

摘要：

我们对于钢框架的结构分析通常通过梁单元来进行。然而，由于该类单元无法确切地捕捉钢材截面的局部屈曲行为，因此，传统的钢结构设计规范采用截面分类的概念来确定截面强度以及变形能力受材料局部屈曲影响的程度。而塑性设计方法的使用仅限于 1 级截面，其具有足够的转动能力以形成塑性铰并引发倒塌机制。在更高级截面中，局部屈曲阻止了具有这种转动能力的塑性铰的形成，除非出于计算需求而使用壳单元，否则我们需要对材料进行弹性分析。然而，本文证明了通过将连续强度法（CSM）及其应变极限纳入分析，可以在梁单元中有效地模拟局部屈曲。此外，通过进行几何非线性和材料非线性的高等分析，可确保无需进行额外的设计检查。如果采用适当而精确的应力 - 应变关系，我们在较粗截面中观察到的应变硬化所带来的积极影响亦可以得到有效应用；为此，我们在文详尽地描述了一个用于热轧钢的四元线性材料模型。对于一致的高等分析框架中任意细长比截面的分析问题， CSM 应变极限分析法均适用，同时还可以从荷载重新分配水平的优化中受益。本文所提出的方法可用于单个构件、连续梁单元及相关框架结构，并且在精度与一致性等方面与当前钢结构设计规范相比，本方法具有显著优势。

关键词： 高等分析     连续强度法     局部屈曲     材料建模     应变极限    

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Advanced finite element analysis of a complex deep excavation case history in Shanghai

Yuepeng DONG, Harvey BURD, Guy HOULSBY, Yongmao HOU

《结构与土木工程前沿（英文）》 2014年 第8卷 第1期   页码 93-100 doi: 10.1007/s11709-014-0232-3

摘要： The construction of the North Square Shopping Center of the Shanghai South Railway Station is a large scale complex top-down deep excavation project. The excavation is adjacent to several current and newly planned Metro lines, and influenced by a neighboring Exchange Station excavation. The highly irregular geometry of this excavation greatly increases the complexity in 3D Finite Element modeling. The advanced numerical modeling described in this paper includes detailed structural and geotechnical behavior. Important features are considered in the analysis, e.g., 1) the small-strain stiffness of the soil, 2) the construction joints in the diaphragm wall, 3) the shrinkage in the concrete floor slabs and beams, 4) the complex construction sequences, and 5) the shape effect of the deep excavation. The numerical results agree well with the field data, and some valuable conclusions are generated.

关键词： advanced finite element analysis     deep excavations     case history     small-strain stiffness    

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Concepts and implementation of strain-based criteria in design codes for steel structures

Reidar BJORHOVDE

《结构与土木工程前沿（英文）》 2012年 第6卷 第3期   页码 210-216 doi: 10.1007/s11709-012-0165-7

摘要： A uniaxial tension test is commonly used to determine the mechanical properties of steel, but it has no meaning for the response of the material in a structure. The test was developed as a consensus solution by producers, fabricators, designers and code writers, to have a standard by which similar materials could be compared to a common base. It does not represent the actual behavior of the steel in a structure, and was never intended to do so. To study the true behavior of the structure and how the material responds it would be better to determine the strains and deformations that will take place during actual service condition. Such characteristics reflect the real behavior, whether in the elastic or inelastic range. If stresses or forces are needed, these are easily determined by the value of the strain and the relevant material modulus, along with the type of cross section, whether elastic or inelastic. The paper addresses the properties of a range of structural steels, how these are incorporated into design standards and how the standards define deformation characteristics and demands for bolted and welded connections.

关键词： steel     stress-strain characteristics     tension test     strain design     actual behavior     improved design codes    

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Development of mix design method based on statistical analysis of different factors for geopolymer concrete

Paramveer SINGH; Kanish KAPOOR

《结构与土木工程前沿（英文）》 2022年 第16卷 第10期   页码 1315-1335 doi: 10.1007/s11709-022-0853-x

摘要： The present study proposes the mix design method of Fly Ash (FA) based geopolymer concrete using Response Surface Methodology (RSM). In this method, different factors, including binder content, alkali/binder ratio, NS/NH ratio (sodium silicate/sodium hydroxide), NH molarity, and water/solids ratio were considered for the mix design of geopolymer concrete. The 2D contour plots were used to setup the mix design method to achieve the target compressive strength. The proposed mix design method of geopolymer concrete is divided into three categories based on curing regime, specifically one ambient curing (25 °C) and two heat curing (60 and 90 °C). The proposed mix design method of geopolymer concrete was validated through experimentation of M30, M50, and M70 concrete mixes at all curing regimes. The observed experimental compressive strength results validate the mix design method by more than 90% of their target strength. Furthermore, the current study concluded that the required compressive strength can be achieved by varying any factor in the mix design. In addition, the factor analysis revealed that the NS/NH ratio significantly affects the compressive strength of geopolymer concrete.

关键词： geopolymer concrete     mix design     fly ash     response surface methodology     compressive strength     stress−strain    

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Cyclic stress-strain behavior of structural steel with yield-strength up to 460 N/mm

Yiyi CHEN,Wei SUN,Tak-Ming CHAN

《结构与土木工程前沿（英文）》 2014年 第8卷 第2期   页码 178-186 doi: 10.1007/s11709-014-0245-y

摘要： This paper presents a constitutive model based on Ramberg-Osgood equation to describe the hysteresis material behavior of structural carbon steel with nominal yield strength between 235 to 420 N/mm . The proposed model was calibrated against a series of cyclic material tests with strain amplitude varying from 0.5% to 2.0%. A simple relationship between the modular parameter and the yield strength was proposed. The calibrated Ramberg-Osgood model revealed excellent agreement with the experimental results and captured further the experimental behavior of test specimens with nominal yield strength of 460 N/mm . The proposed constitutive model was also adopted in conjunction with the combined kinematic/isotropic materials description in ABAQUS to mimic a full scale experimental test under cyclic loading. The numerical results revealed close agreement with the experimental observations.

关键词： constitutive model     finite element analysis     hysteresis curve     Ramberg-Osgood equation    

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Dynamic failure analysis on granite under uniaxial impact compressive load

ZHAI Yue, MA Guowei, HU Changming, ZHAO Junhai

《结构与土木工程前沿（英文）》 2008年 第2卷 第3期   页码 253-260 doi: 10.1007/s11709-008-0042-6

摘要： High strain-rate uniaxial compressive loading tests were produced in the modified split Hopkinson pressure bar (SHPB) with pulse shaper on granite samples. It was shown that the failure of the granite cylinder was typical tensile splitting failure mode by sudden splitting parallel to the direction of uniaxial compressive loading at different strain rates. Besides, it was concluded that not only the strength of granite increased, but also the fragment size decreased and the fragment numbers increased with the increasing strain rate. To quantitatively analyze the failure phenomena, the numerical calculation based on a dynamic interacting sliding microcrack model was adopted to investigate the influence of microcrack with the different initial crack length, crack angle, crack space and friction coefficient on the macro-mechanical properties of granite under different strain rates. Accordingly, the strain-dependency of the compression strength and the fragmentation degree of granite was explained reasonably.

关键词： numerical calculation     coefficient     cylinder     splitting parallel     strain-dependency    

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Deformation analysis of shape memory polymer for morphing wing skin under airflow

Weilong YIN, Jingcang LIU, Jinsong LENG,

《机械工程前沿（英文）》 2009年 第4卷 第4期   页码 447-449 doi: 10.1007/s11465-009-0062-5

摘要： The method for analyzing the out-of-plane deformation of a flexible skin under airflow is developed in this paper. The aerodynamic analysis is performed using the CFD software, and the structural analysis is performed using finite element method. The chief aim of the present study is to investigate the out-of-plane deformation of the shape memory polymer (SMP) skin at different temperatures. Numerical results show that the maximum out-of-plane displacement of the SMP skin increases with increasing temperature. When the SMP skin is heated to 53°C, the maximum out-of-plane displacement is about 7 mm. It decreases by 72%, when the SMP skin is applied with a uniform pre-strain of 0.1.

关键词： aircraft     morphing     skin     shape memory polymer (SMP)     deformation     pre-strain    

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Full-field dynamic strain reconstruction of an aero-engine blade from limited displacement responses

《机械工程前沿（英文）》 2023年 第18卷 第1期 doi: 10.1007/s11465-022-0731-1

摘要： Blade strain distribution and its change with time are crucial for reliability analysis and residual life evaluation in blade vibration tests. Traditional strain measurements are achieved by strain gauges (SGs) in a contact manner at discrete positions on the blades. This study proposes a method of full-field and real-time strain reconstruction of an aero-engine blade based on limited displacement responses. Limited optical measured displacement responses are utilized to reconstruct the full-field strain. The full-field strain distribution is in-time visualized. A displacement-to-strain transformation matrix is derived on the basis of the blade mode shapes in the modal coordinate. The proposed method is validated on an aero-engine blade in numerical and experimental cases. Three discrete vibrational displacement responses measured by laser triangulation sensors are used to reconstruct the full-field strain over the whole operating time. The reconstructed strain responses are compared with the results measured by SGs and numerical simulation. The high consistency between the reconstructed and measured results demonstrates the accurate strain reconstructed by the method. This paper provides a low-cost, real-time, and visualized measurement of blade full-field dynamic strain using displacement response, where the traditional SGs would fail.

关键词： aero-engine blade     displacement response     dynamic strain reconstruction     mode shape     strain gauge    

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An investigation into the vibration of harmonic drive systems

M. Masoumi, H. Alimohammadi

《机械工程前沿（英文）》 2013年 第8卷 第4期   页码 409-419 doi: 10.1007/s11465-013-0275-5

摘要：

Harmonic drive systems are precise and specific transmission gear systems which are beneficial in terms of the high transmission ratio and almost zero backlash. These inherent and spectacular properties result in using this mechanism in robotic and space sciences where the precision and lightwieght play an important role. This paper presents a vibration analysis of harmonic drive systems using the shell theory. Equations of vibration for the flexspline and the circular spline of the system are derived and used to find the natural frequencies for both parts and, moreover, vibration response of the system under the operating condition is calculated. Also, obtained vibration equations are utilized to study the effects of different involved parameters such as the geometry of the flexspline and its gear tooth, eccentricity, and unbalancing on the vibrational behavior of the system.

关键词： harmonic drive system     strain wave gearing mechanism     vibration analysis     natural frequencies    

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标题 作者 时间 类型 操作

FEM-based strain analysis study for multilayer sheet forming process

Rongjing ZHANG,Lihui LANG,Rizwan ZAFAR

期刊论文

Fictitious soil pile model for dynamic analysis of pipe piles under high-strain conditions

期刊论文

Vibration analysis of nano-structure multilayered graphene sheets using modified strain gradient theory

Amir ALLAHBAKHSHI,Masih ALLAHBAKHSHI

期刊论文

Adaptive selective ES-FEM limit analysis of cracked plane-strain structures

H. NGUYEN-XUAN,T. RABCZUK

期刊论文

Bioleaching of spent Ni-Cd batteries and phylogenetic analysis of an acidophilic strain in acidified

ZHAO Ling, WANG Liang, YANG Dong, ZHU Nanwen

期刊论文

Construction of an immortalized neural progenitor cell strain and analysis of its immunogenicity

AN Ke, XU Ying, TIAN Xuebi, GAO Feng, TIAN Yuke, YANG Hui, ZHANG Chuanhan

期刊论文

基于高等分析的钢结构设计——材料建模与应变极限

Leroy Gardner, Xiang Yun, Andreas Fieber, Lorenzo Macorini

期刊论文

Advanced finite element analysis of a complex deep excavation case history in Shanghai

Yuepeng DONG, Harvey BURD, Guy HOULSBY, Yongmao HOU

期刊论文

Concepts and implementation of strain-based criteria in design codes for steel structures

Reidar BJORHOVDE

期刊论文

Development of mix design method based on statistical analysis of different factors for geopolymer concrete

Paramveer SINGH; Kanish KAPOOR

期刊论文

Cyclic stress-strain behavior of structural steel with yield-strength up to 460 N/mm

Yiyi CHEN,Wei SUN,Tak-Ming CHAN

期刊论文

Dynamic failure analysis on granite under uniaxial impact compressive load

ZHAI Yue, MA Guowei, HU Changming, ZHAO Junhai

期刊论文

Deformation analysis of shape memory polymer for morphing wing skin under airflow

Weilong YIN, Jingcang LIU, Jinsong LENG,

期刊论文

Full-field dynamic strain reconstruction of an aero-engine blade from limited displacement responses

期刊论文

An investigation into the vibration of harmonic drive systems

M. Masoumi, H. Alimohammadi

期刊论文