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Thermal buckling behavior of laminated composite plates: a finite-element study

Houdayfa OUNIS,Abdelouahab TATI,Adel BENCHABANE

《机械工程前沿（英文）》 2014年第9卷第1期页码 41-49 doi: 10.1007/s11465-014-0284-z

摘要：

In this paper, the thermal buckling behavior of composite laminated plates under a uniform temperature distribution is studied. A finite element of four nodes and 32 degrees of freedom (DOF), previously developed for the bending and mechanical buckling of laminated composite plates, is extended to investigate the thermal buckling behavior of laminated composite plates. Based upon the classical plate theory, the present finite element is a combination of a linear isoparametric membrane element and a high precision rectangular Hermitian element. The numerical implementation of the present finite element allowed the comparison of the numerical obtained results with results obtained from the literature: 1) with element of the same order, 2) the first order shear deformation theory, 3) the high order shear deformation theory and 4) the three-dimensional solution. It was found that the obtained results were very close to the reference results and the proposed element offers a good convergence speed. Furthermore, a parametrical study was also conducted to investigate the effect of the anisotropy of composite materials on the critical buckling temperature of laminated plates. The study showed that: 1) the critical buckling temperature generally decreases with the increasing of the modulus ratio E_L/E_T and thermal expansion ratio α_T/α_L, and 2) the boundary conditions and the orientation angles significantly affect the critical buckling temperature of laminated plates.

关键词： thermal buckling laminated composite plates anisotropy critical buckling temperature finite-element method high precision rectangular Hermitian element

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MHD effect on the critical temperature differences of oscillatory thermocapillary convection in two-layer

Hulin HUANG, Xiaoming ZHOU,

《能源前沿（英文）》 2010年第4卷第2期页码 155-160 doi: 10.1007/s11708-009-0063-4

摘要： The effect of different directional magnetic fields on critical temperature differences of oscillatory thermocapillary convection in a rectangular cavity with differentially heated side walls filled with two viscous, immiscible, incompressible fluids is simulated in the absence of gravity. In this two-layer fluid system, the upper layer fluid is the electrically non-conducting encapsulant boron oxide (BO), while the lower one is the electrically conducting molten indium phosphide (InP). The interface between the two fluids is assumed to be flat and non-deformable. The computational results show that all the magnetic fields along the , and directions can delay the transition from steady convection to oscillatory convection, and critical temperature differences increase with an increasing Hartmann number. Furthermore, the effect of a magnetic field along the direction is strongest, followed by that along the direction, and that along the direction is the weakest for the same intensity of the magnetic field.

关键词： magnetohydrodynamic magnetic fields thermocapillary convection critical temperature difference oscillatory convection two-layer fluid system

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板面弹性压板力对提升板料失稳临界应力的作用及其应用

宋爱平,王隆太,李吉中,王树峰

《中国工程科学》 2009年第11卷第2期页码 53-59

摘要：

从分析矩形薄板的受压失稳临界应力入手，提出在冲压成形板料的上下面设置弹性压板力，从而提升板料的失稳临界应力，减少板料的受压屈曲与起皱。根据这个原理设计的新型冲压模具可有效地控制板料的起皱，同时具有“一模多用”的作用。试验也表明，具有板面多点压板功能的冲压模具，可以显著地提升板料的失稳临界应力，减少板料的起皱。

关键词：起皱临界应力模具冲压工艺

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The critical role of autophagy in plant responses to abiotic stresses

Yu WANG,Jie ZHOU,Jingquan YU

《农业科学与工程前沿（英文）》 2017年第4卷第1期页码 28-36 doi: 10.15302/J-FASE-2017130

摘要： Autophagy is an evolutionary conserved recycling process in eukaryotes whereby intracellular components are engulfed by autophagosomes, which are subsequently transferred to the vacuoles for further degradation and reuse. In organisms like yeast and metazoans, autophagy is actively engaged during environmental perturbation either by degrading denatured proteins and organelles or by interfacing with stress related signaling molecules. Studies over the last decade have also revealed numerous important mechanisms where autophagy is widely involved in plant abiotic stress responses. Autophagy serves as a pivotal route for nutrient remobilization by the degradation of superfluous or damaged cellular cytoplasmic material and organelles. It is also reported to regulate the accumulation of reactive oxygen species, to maintain the cellular redox balance of plants under stressful conditions. Furthermore, autophagy is essential in regulating cellular toxicity by removing aggregated and/or denatured proteins and thereby improving plant stress tolerance. In this review, recent advances in our understanding of autophagy, along with pathways and regulatory networks through which it influences many aspects of plant growth and development in response to nutrient starvation, oxidative stress, osmotic stress and extreme temperatures are discussed.

关键词： abiotic stresses autophagy extreme temperature nutrient starvation osmotic stress oxidative stress

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Experimental study and numerical simulation on compressive buckling behavior of thin steel skins in unilateral

Nicholas KEAGE, Christopher MAIOLO, Rebecca PIEROTTI, Xing MA

《结构与土木工程前沿（英文）》 2011年第5卷第3期页码 335-343 doi: 10.1007/s11709-011-0121-y

摘要： In this paper, a practical test and finite element analysis has been undertaken to further investigate the effects of contact buckling. A test rig was designed and constructed to record vertical and transverse deflections of compressively loaded steel skin plates. The boundary conditions were modeled as fully fixed. A finite element analysis was also undertaken using the software package Strand7. Results from both analyses have been examined and compared to data established from previous studies on contact buckling. Both the finite element analysis and practical results correlate well with this data. The result of the investigation has confirmed contact buckling theories and has foreshadowed the onset of the newly observed phenomenon of secondary contact buckling.

关键词： compressive buckling thin steel skins unilateral contact rigid constraints

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Finding buckling points for nonlinear structures by dynamic relaxation scheme

Mohammad REZAIEE-PAJAND, Hossein ESTIRI

《结构与土木工程前沿（英文）》 2020年第14卷第1期页码 23-61 doi: 10.1007/s11709-019-0549-z

摘要： Dynamic Relaxation Method (DRM) is an explicit approach for solving the simultaneous systems of equations. In this tactic, the fictitious mass and damping are added to the static governing equations, and an artificial dynamic system is constructed. By using DRM for nonlinear analysis, the structural static equilibrium path is obtained. This outcome is extremely valuable, since it leads to the behavior of structures. Among the finding related to the structural static path are the critical and buckling points for nonlinear structures. In this paper, a new way for calculating the load factor is proposed by setting the external work zero. Mixing the dynamic relaxation scheme with external work technique has not been formulated so far. In all incremental-iterative methods, the load factor increment sign should be determinated by extra calculations. This sign leads to increase or decrease of the load increment. It is worth emphasizing that sign of the load factor increment changes at the load limit points. Therefore, the sign determinations are required in the common work control methods. These disadvantages are eliminated in the proposed algorithm. In fact, the suggested load factor depends only on the Dynamic Relaxation (DR) fictitious parameters. Besides, all DR calculations are performed via vector operation. Moreover, the load factor is calculated only by one formula, and it has the same relation in the all solution processes. In contrast to the arc length techniques, which requires the sign determined, the proposed scheme does not need any sign finding. It is shown that author’s technique is quicker than the other dynamic relaxation strategies. To prove the capability and efficiency of the presented scheme, several numerical tests are performed. The results indicate that the suggested approach can trace the complex structural static paths, even in the snap-back and snap-through parts.

关键词： load factor external work dynamic relaxation static equilibrium path large displacement

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Out-of-plane elastic buckling load and strength design of space truss arch with a rectangular section

Senping WANG; Xiaolong LIU; Bo YUAN; Minjie SHI; Yanhui WEI

《结构与土木工程前沿（英文）》 2022年第16卷第9期页码 1141-1152 doi: 10.1007/s11709-022-0866-5

摘要： The out-of-plane stability of the two-hinged space truss circular arch with a rectangular section is theoretically and numerically investigated in this paper. Firstly, the flexural stiffness and torsional stiffness of space truss arches are deduced. The calculation formula of out-of-plane elastic buckling loads of the space truss arch is derived based on the classical solution of out-of-plane flexural-torsional buckling loads of the solid web arch. However, since the classical solution cannot be used for the calculation of the arch with a small rise-span ratio, the formula for out-of-plane elastic buckling loads of space truss arches subjected to end bending moments is modified. Numerical research of the out-of-plane stability of space truss arches under different load cases shows that the theoretical formula proposed in this paper has good accuracy. Secondly, the design formulas to predict the out-of-plane elastoplastic stability strength of space truss arches subjected to the end bending moment and radial uniform load are presented through introducing a normalized slenderness ratio. By assuming that all components of space truss circular arches bear only axial force, the design formulas to prevent the local buckling of chord and transverse tubes are deduced. Finally, the bearing capacity design equations of space truss arches are proposed under vertical uniform load.

关键词： torsional stiffness strength design elastic buckling space truss arches out-of-plane

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Flexural-torsional buckling behavior of aluminum alloy beams

Xiaonong GUO,Zhe XIONG,Zuyan SHEN

《结构与土木工程前沿（英文）》 2015年第9卷第2期页码 163-175 doi: 10.1007/s11709-014-0272-8

摘要： This paper presents an investigation on the flexural-torsional buckling behavior of aluminum alloy beams (AAB). First, based on the tests of 14 aluminum alloy beams under concentrated loads, the failure pattern, load-deformation curves, bearing capacity and flexural-torsional buckling factor are studied. It is found that all the beam specimens collapsed in the flexural-torsional buckling with excessive deformation pattern. Moreover, the span, loading location and slenderness ratio influence the flexural-torsional buckling capacity of beams significantly. Secondly, besides the experiments, a finite element method (FEM) analysis on the flexural-torsional buckling behavior of AAB is also conducted. The main parameters in the FEM analysis are initial imperfection, material property, cross-section and loading scheme. According to the analytical results, it is indicated that the FEM is reasonable to capture mechanical behavior of AAB. Finally, on the basis of the experimental and analytical results, theoretical formulae to estimate the flexural-torsional buckling capacity of AAB are proposed, which could improve the application of present codes for AAB.

关键词： flexural-torsional buckling aluminum alloy beams (AAB) finite element method (FEM) theoretical formula

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Probabilistic stability of uncertain composite plates and stochastic irregularity in their buckling mode

《结构与土木工程前沿（英文）》页码 179-190 doi: 10.1007/s11709-022-0888-z

摘要： In this study, the mechanical properties of the composite plate were considered Gaussian random fields and their effects on the buckling load and corresponding mode shapes were studied by developing a semi-analytical non-intrusive approach. The random fields were decomposed by the Karhunen−Loève method. The strains were defined based on the assumptions of the first-order and higher-order shear-deformation theories. Stochastic equations of motion were extracted using Euler–Lagrange equations. The probabilistic response space was obtained by employing the non-intrusive polynomial chaos method. Finally, the effect of spatially varying stochastic properties on the critical load of the plate and the irregularity of buckling mode shapes and their sequences were studied for the first time. Our findings showed that different shear deformation plate theories could significantly influence the reliability of thicker plates under compressive loading. It is suggested that a linear relationship exists between the mechanical properties’ variation coefficient and critical loads’ variation coefficient. Also, in modeling the plate properties as random fields, a significant stochastic irregularity is obtained in buckling mode shapes, which is crucial in practical applications.

关键词： uncertain composite plate stochastic assume mode method Karhunen−Loève theorem polynomial chaos approach plate buckling irregularity in buckling mode shapes

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Fundamental buckling of circular plates with elastically restrained edges and resting on concentric rigid

Lokavarapu Bhaskara Rao, Chellapilla Kameswara Rao

《机械工程前沿（英文）》 2013年第8卷第3期页码 291-297 doi: 10.1007/s11465-013-0255-9

摘要：

This work presents the existence of buckling mode switching with respect to the radius of concentric rigid ring support. The buckling mode may not be axisymmetric as previously assumed. In general, the plate may buckle in an axisymmetric mode but when the radius of the ring support becomes small, the plate may buckle in an asymmetric mode. The optimum radius of the concentric rigid ring support for maximum buckling load is also determined. Introducing internal rigid ring support, when placed at an optimal position increases the elastic buckling load capacity by 149.39 percent. The numerical results obtained are in good agreement with the previously published data.

关键词： buckling circular plate elastically restrained edge rigid ring support mode switching

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Experimental study on slender buckling-restrained knee braces with round steel bar cores

《结构与土木工程前沿（英文）》 2023年第17卷第1期页码 99-121 doi: 10.1007/s11709-022-0875-4

摘要： This study aimed to investigate a novel slender buckling-restrained knee brace damper (BRKB) for welded and weld-free steel framing systems. The proposed BRKB adopts steel bar cores connected by a central coupler and restrained by tube buckling restrainers with a cover tube supporter. The advantages of the proposed damper include easy assembly compared to conventional buckling restrained braces, and high architectural flexibility for the retrofitting of large-span weld-free or welded steel moment-resisting systems. Specifically, by increasing the number of contraction allowances, undesirable failure mechanisms that are global instability and local buckling of the restrainer ends can be effectively suppressed because the more uniform plastic deformation of the core bar can be achieved longitudinally. In this study, displacement-controlled compression and cyclic loading tests were carried out to investigate the deformation capacities of the proposed BRKBs. Structural performance metrics associated with both loading tests, such as strength capacities, strains at the cover tubes and buckling restrainers, and hysteretic behaviors of the proposed damper under cyclic loads, were measured and discussed. Test results revealed that the geometrical characteristics of the cover tubes and adopted contraction allowances at the dampers play essential roles in their load-bearing capacities.

关键词： weld-free beam-to-column connections moment-resisting frame cyclic and compression loading tests buckling-restrained knee brace cover tube

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Lateral-torsional buckling capacity assessment of web opening steel girders by artificial neural networks

Yasser SHARIFI,Sajjad TOHIDI

《结构与土木工程前沿（英文）》 2014年第8卷第2期页码 167-177 doi: 10.1007/s11709-014-0236-z

摘要： Bridge girders exposed to aggressive environmental conditions are subject to time-variant changes in resistance. There is therefore a need for evaluation procedures that produce accurate predictions of the load-carrying capacity and reliability of bridge structures to allow rational decisions to be made about repair, rehabilitation and expected life-cycle costs. This study deals with the stability of damaged steel I-beams with web opening subjected to bending loads. A three-dimensional (3D) finite element (FE) model using ABAQUS for the elastic flexural torsional analysis of I-beams has been used to assess the effect of web opening on the lateral buckling moment capacity. Artificial neural network (ANN) approach has been also employed to derive empirical formulae for predicting the lateral-torsional buckling moment capacity of deteriorated steel I-beams with different sizes of rectangular web opening using obtained FE results. It is found out that the proposed formulae can accurately predict residual lateral buckling capacities of doubly-symmetric steel I-beams with rectangular web opening. Hence, the results of this study can be used for better prediction of buckling life of web opening of steel beams by practice engineers.

关键词： steel I-beams lateral-torsional buckling finite element (FE) method artificial neural network (ANN) approach

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拓扑优化中采用增材制造填充构件的结构屈曲荷载提升设计 Artical

Anders Clausen, Niels Aage, Ole Sigmund

《工程（英文）》 2016年第2卷第2期页码 250-257 doi: 10.1016/J.ENG.2016.02.006

摘要：

增材制造可实现优质多功能构件所具有的高度复杂几何构型的制备。可以直接制备内含多孔填充的结构部件是其独有特征的一个例证。现有的设计方法还难以充分利用这一设计自由度，直接获得类似结构的设计。本文将展示涂层方法 (coating approach) 的拓扑优化方法来作为多孔填充构件的设计方法，所设计的构件具有显著改进的临界屈曲载荷，从而使得整体结构部件的稳定性增强。传统的柔顺性拓扑优化方法极少在数学模型中考虑构件的屈曲约束，稳定性要求通常要经过后续的校核与改进过程满足。这一后续过程往往只能获得次优设计。本文所展示的方法弥补了传统柔顺性拓扑优化模型中难以考虑构件屈曲约束的缺陷。利用涂层拓扑优化方法与传统柔顺性拓扑优化同时对经典的MBB 梁进行设计，并采用熔丝增材制造技术对设计结果进行了制备。实验结果验证了涂层方法的数学模型的正确性。由于填充材料的性质，在相同条件下，涂层优化得到的多孔填充结构的屈曲载荷比传统优化得到的实体结构高四倍以上。

关键词：增材制造填充构件拓扑优化屈曲

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热塑性装饰材料点燃性能研究

徐亮,张和平,万玉田

《中国工程科学》 2007年第9卷第12期页码 39-43

摘要：利用锥形量热仪研究了典型热塑性装饰材料的点燃性能，并利用数值模拟结合线性回归方法导出了适合热中型材料的点燃模型。利用此模型对实验得到的点燃时间进行了分析，得到了材料的临界热辐射通量、点燃温度与热物性参数，结果表明研究得到的材料热辐射通量与点燃温度、点燃时间和文献中给出的值比较吻合，导出的模型具有较好的适用性。

关键词：热塑性材料点燃性能临界热辐射通量点燃温度

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Experiments on channel columns with inclined simple edge stiffeners under compression loading

WANG Chungang, ZHANG Yaochun, ZHANG Zhuangnan

《结构与土木工程前沿（英文）》 2007年第1卷第3期页码 312-321 doi: 10.1007/s11709-007-0041-z

摘要： In order to investigate the compression behavior of pin-ended cold-formed channel columns with inclined simple edge stiffeners, a total of 30 pin-ended cold-formed channel columns with three sections (sloping lip stiffener turned at 45º, 90º, and 135º to the flange, respectively) and three different lengths (500 mm, 1 250 mm, and 2 000 mm) were tested. It was found that the inclination angles and loading positions have an obvious effect on compression ultimate load-carrying capacities and failure modes. All three sections have certain post-buckling strength, and the failure modes of most of the specimens contained distortional buckling. The capacity of the specimens with 45º inclined angle for bearing compression is appreciably higher than the other two types of specimens with 90º or 135º inclined angles at the same negative eccentricity, but obviously lower than the other two at the same positive eccentricity. Furthermore, tests were simulated by finite element analysis. Results from the analysis are in great agreement with the experimental data.

关键词： different post-buckling strength capacity distortional buckling Furthermore