不同介质中集团装药爆炸混凝土冲击响应的数值模拟

基于非线性有限元软件ANSYS/LS-DYNA,选用Holmquist-Johnson-Cook损伤本构模型,对不同介质中集团装药爆炸下混凝土的动态响应进行了数值模拟,研究了装药在不同介质中爆炸对混凝土的冲击响应和爆炸波在混凝土内的传播与衰减规律。结果表明,介质对混凝土内应力场、压力场、损伤和速度场的分布与衰减有着十分明显的影响。     

不同介质中集团装药爆炸混凝土冲击响应的数值模拟

基于非线性有限元软件ANSYS/LS-DYNA,选用Holmquist-Johnson-Cook损伤本构模型,对不同介质中集团装药爆炸下混凝土的动态响应进行了数值模拟,研究了装药在不同介质中爆炸对混凝土的冲击响应和爆炸波在混凝土内的传播与衰减规律。结果表明,介质对混凝土内应力场、压力场、损伤和速度场的分布与衰减有着十分明显的影响。     

坡膛结构变化对弹带挤进过程影响的研究

基于弹塑性有限元接触理论,引入了弹带材料的初始损伤及累计损伤模型,对弹带挤进、冲击坡膛的过程进行了理论分析,建立了弹带挤进、冲击坡膛的显式非线性有限元模型。对在两种不同结构坡膛条件下的弹带挤进过程进行了分析计算,得到了挤进过程弹丸及弹带的动力学响应,并通过计算分析了坡膛结构变化对挤进冲击力的影响,揭示了坡膛裂纹的形成机理。     

框架结构地震反应分析的有限元模型

本文提出一种用于框架结构地震反应分析的有限元模型。模型中采用四结点平面应力等参单元模拟上部框架结构的梁柱构件。地基中通过设置底部透射边界和侧面捆绑边界以考虑结构一地基的相互作用。文中算例表明上述框架结构地震反应分析的有限元模型给出了合理的结构地震反应，可进一步用于地震时结构几何与非线性响应直至结构破坏时的计算机仿真。     

水力割缝本煤层抽采煤层气应力场数值模拟

我国浅部煤炭资源逐渐开采枯竭，很多煤矿相继进入深部开采作业阶段。针对平顶山十矿深部煤层处在高地应力和高孔隙压力下实际情况，基于ANSYS有限元分析软件对水力割缝技术本煤层卸压抽采煤层气进行了数值模拟研究。分析了水力割缝技术与破煤机理，建立了水力割缝开采深部煤层气平面应变有限元模型，得到了钻井前后、水力割缝前后有限元模型的地应力场变化规律及其影响范围。数值模拟结果表明，水力割缝技术可达到使近井地带充分卸压的目的，应用水力割缝在深部煤层气开采中卸压效果明显。     

坝基界面在非线性水压力驱动下的非线性断裂过程模拟

基于多边形比例边界有限元法和粘聚裂缝模型提出了混凝土坝坝基界面在随缝宽非线性变化的水压力驱动下的非线性断裂数值模型。混凝土和基岩采用多边形比例边界单元模拟,界面裂缝的断裂过程区采用粘性界面单元模拟。因为界面裂缝总是处于复合断裂模态,故同时引入了法向和切向的界面单元,且考虑了裂纹面作用有法向和切向任意荷载时的应力强度因子求解。以裂尖为原点,裂尖附近的位移场和应力场在径向上解析求解,在环向具有有限元精度。因此无需在裂尖附近加密网格或采用富集技术即可求得高精度的解。对于界面断裂,可模拟出与两种材料差异性相关的非1/2奇异性。断裂过程区的水压力随缝面宽度变化,采用指数函数的形式进行表征,通过参数调整可实现不同分布的水压力的模拟。水压力与粘聚力考虑为与裂缝宽度相关的组合函数,便于非线性迭代的实现。结合多边形网格生成和重剖分技术,可方便地模拟界面裂缝在水力驱动下的扩展过程。算例研究表明了该文模型的有效性,从中也可看出考虑缝内水压及其具体分布形式对研究坝的稳定性具有重要影响。     

钨合金动态力学性能的三维数值模拟研究

采用数值模拟的方法对钨合金在冲击载荷作用下的动态力学响应进行了研究。运用有限元动力分析程序建立了具有典型微观结构钨合金三维有限元单胞模型,对钨合金在拉伸载荷作用下的动态力学性能进行了数值模拟研究,分析了应变率对其力学性能的影响,给出了不同应变率条件下单胞模型的应力和应变分布云图,在与实验结果对比的基础上验证了该有限元模型的可靠性。     

基于双轴拉伸试验的飞艇蒙皮材料非线性分析

飞艇蒙皮为多功能层压织物材料,力学行为呈现复杂的非线性,合理表征其非线性的力学模型对飞艇结构设计与分析至关重要。本文对飞艇蒙皮材料试件进行了7个应力比双轴拉伸试验,基于正交异性材料模型,采用应变残差平方和最小方法计算弹性常数,建立线性力学模型;根据试验数据建立应力弹性常数响应面,建立以应力为变量的完整三次式非线性力学模型。并根据此力学模型建立飞艇蒙皮材料有限元分析模型,通过数值模拟七种应力比下的双轴拉伸试验,分析结果的应力分布和分缝位移与试验现象一致。将分析得到的应力-应变曲线与试验结果进行对比,两者能很好的吻合,表明非线性力学模型及分析方法适用于飞艇结构分析。     

地震波斜入射下考虑场地非线性、地形效应和土结动力相互作用的大跨连续刚构桥地震响应分析

基于多源叠加粘弹性人工边界和等效线性化理论,建立了SV波斜入射下考虑场地非线性、地形效应和土-结构动力相互作用的大跨结构动力响应分析计算方法。该文首先给出了SV波斜入射下非线性场地的自由场等效线性化求解方法,然后利用ANSYS有限元软件对一座5跨连续刚构桥和场地建立了有限元模型,计算了考虑场地非线性情况下不同入射角、不同地形和不同场地刚度工况下连续刚构桥的动力响应。计算结果表明:桥墩轴力随着入射角的增大而增大,剪力则随着入射角的增大而减小;局部地形不规则程度对桥梁结构内力放大效应有所不同,地形变化越剧烈,放大效应越明显;土体刚度对考虑土-结构动力相互作用的桥梁结构动力响应有较大影响,土体越软,土-结构动力相互作用效应越明显。     

既有铁路钢桁梁桥基准有限元模型建立与验证

为了评估既有铁路钢桁梁桥的工作状态和使用安全，需要建立能够精确模拟结构目前状态的有限元模型。以南京长江大桥为例，根据灵敏度的物理意义，从简单实用的角度出发，充分利用现有的大型有限元分析程序，以结构设计参数为修改参数，以结构自振频率为目标函数对初始结构有限元模型进行修正，最后以结构主要杆件应力时程响应为验证参数建立了能够表征该桥目前状态有限元基准模型，为大桥的状态和疲劳寿命评估提供了科学基础。     

Discrete and continuum methods for numerical simulations of non‐linear wave propagation in discontinuous media

The main objective of this paper is to develop a methodology to model dynamic loading of various discontinuous media. Two methods for modeling non‐linear waves in a media with multiple discontinuities are considered. The first one, a discrete method, is based on the Simple Common Plane contact algorithm. This method can be applied both to compliant contacts characterized by finite thickness and elastic moduli (such as joints in geomechanics) as well as to non‐compliant frictional contacts traditionally described by the slide lines in finite element/finite difference codes. The second one, a continuum method, assumes that the contacts are not compliant and can be modeled as one or several weakness planes cutting through the elements of the computational mesh. Both discrete and continuum methods described in the paper can be applied to derive equivalent continuum properties for media with multiple discontinuities. An example of such application for a randomly jointed media is given in the paper. Copyright © 2010 John Wiley & Sons, Ltd.     

油管螺纹应力应变场的有限元分析与检测

利用ANSYS大型分析软件,建立了属于表面非线性和材料非线性相偶合问题的油管接头的弹塑性轴对称接触有限元模型,对油管接头在不同载荷工况和不同配合下的应力应变场进行了数值计算。又用电测法对油管接头的油管内壁进行了实际测量。对比两种不同方法得到的结果,验证了轴对称模型有限元法的适用范围。可靠地给出了工程中最危险截面应力应变场的各种变化规律,为研究油管的疲劳断裂问题提供了重要的理论分析依据和数据。     

子午线轮胎静负荷实验的有限元模拟

建立了一种子午线轮胎的三维非线性有限元模型,来模拟子午线轮胎的静负荷试验。模型中考虑了橡胶材料的非线性和不可压缩性、帘线-橡胶复合材料的各向异性、轮胎大变形导致的几何非线性以及轮胎与轮辋、轮胎与路面的接触非线性边界条件。提出了一种单元重叠技术,通过重叠不可压缩橡胶单元和描述帘线的单元来模拟帘线-橡胶复合材料,这种单元重叠技术产生的轮胎模型比正交各向异性模型计算过程更稳定。通过有限元分析,得到了子午线轮胎在充气压力和静负荷作用下的变形和应力分布情况以及接地区的压力分布情况,并将计算结果与试验结果进行了比较,两者吻合得很好。     

过盈配合和预紧力的混合作用对复合材料机械连接结构的影响及其机制

为研究钉孔过盈配合情况和紧固件预紧力及二者混合作用对复合材料连接强度的影响及其机制,提出了一种基于试验验证的有限元方法,在有限元模拟结果与两组不同配合复合材料与钛合金单剪双钉连接拉伸试验吻合良好的基础上,进一步模拟6种不同螺栓预紧力和7种不同钉孔配合模式的组合,共42种不同情况的结构承载能力。通过对模拟结果的分析发现：一定的干涉配合值和预紧力虽然可能导致钉孔周围在受载较小时提前出现较小破坏,但在载荷较大时反而可以改善孔周的接触条件,从而减小孔周的纤维破坏范围,并最终提高连接结构的破坏载荷。而且钉孔配合情况和螺栓预紧力对连接结构承载能力会相互影响,即在不同钉孔配合情况下所得到的紧固件预紧力优化值会有所不同,反之亦然。因此在进行复合材料机械连接结构承载能力优化时,必须同时考虑不同参数的影响,才能获得最优的结构设计。     

节理裂隙岩体爆破试验研究

首先利用超声波探测法对节理裂隙岩体进行了声波测试,对不同的节理裂隙岩体进行了质量评估.然后通过对节理裂隙岩体进行爆破漏斗试验,分析了节理裂隙对岩体中爆炸应力波传播、岩石破碎及爆破漏斗形成的影响,得出了一些有益结论,对节理裂隙岩体理论研究和指导工程实践具有一定的参考价值.     

A continuum finite element for single-set jointed media

In response to the need for an advanced computational model for wave propagation in jointed-rock media a new finite element for jointed media with a single set of regularly spaced joints is developed. The element is a numerical implementation of the higher-order homogenization model recently proposed by Murakami and Hegemier. Due to the dispersive effects induced by regularly spaced joints, wave phenomena in jointed media are altered significantly. Therefore, in order to improve the interpretation of seismograms for accurate source identification, it is necessary to develop a higher-order continuum element. The accuracy and efficiency of the new element is investigated by applying it to wave-guide and wave-normal problems of a jointed half-space and by comparing the wave response with that of DYNA2D. The analyses by DYNA2D discretize explicitly the details of the joint microstructure, and are adopted as numerically exact measures for the assessment of the proposed finite element; good correlations were obtained. The validation study also confirmed the importance of wave dispersion for non-linear as well as linear joint responses. Finally, as a more practical application of the proposed element, the problem of a jointed full-space with a cylindrical cavity pressurized by step and pulse loadings was solved. Velocities at several observation points were compared with the numerically exact results of DYNA2D. Similar analyses carried out for elastic isotropic media predicted totally different velocity responses and confirmed the need for the proposed element.     

Bending and Stability of a Glued Curvilinear Rod with Initial Irregularities

A differential equation has been derived for the bending of a glued curvilinear rod with initial deflections of its elements. Adhesive joints work in shear. The 2D stability, collapse and buckling are investigated for a jointed rod, and the formulas are derived to determine the critical values of its element parameters. Some separate cases are considered and examples are given. __________ Translated from Problemy Prochnosti, No. 6, pp. 114 – 123, November – December, 2005.     

Arbitrary discontinuities in finite elements

A technique for modelling arbitrary discontinuities in finite elements is presented. Both discontinuities in the function and its derivatives are considered. Methods for intersecting and branching discontinuities are given. In all cases, the discontinuous approximation is constructed in terms of a signed distance functions, so level sets can be used to update the position of the discontinuities. A standard displacement Galerkin method is used for developing the discrete equations. Examples of the following applications are given: crack growth, a journal bearing, a non‐bonded circular inclusion and a jointed rock mass. Copyright © 2001 John Wiley & Sons, Ltd.     

层状裂隙岩体弹塑性损伤断裂模型与岩质高边坡稳定分析

本文研究了层状裂隙岩体的弹塑性损伤断裂模型。文中按岩体等效柔度张量定义损伤张量,并对层状裂隙岩质高边坡的变形破坏过程建立了损伤演化方程,提出了包含软弱薄层塑性滑移与裂隙损伤扩展耦合性态的本构关系。最后将其应用于某水电站左坝肩高边坡开挖形成过程的稳定性分析中。     

Contact analysis of mechanically fastened joints in composite laminates by linear complementarity problem formulation

The contact phenomena and stress distributions in the vicinity of the hole on mechanically fastened joints are investigated in composite laminates exhibiting nonlinear elastic behavior. The effects of fastener stiffness, friction force between the fastener and the composite laminates, geometrical nonlinearities due to concentrated fastener load around the hole edge for the snug and clearance-fit in the [0 °]_S, [± 45 °]_S, [0°/± 45 °]_S and laminates are also considered. An efficient numerical procedure is developed for the solution of the contact problems with Coulomb friction between the fastener and the hole based on a linear complementarity problem (LCP) formulation in an incremental form. A nonlinear finite element code for stress analysis of laminated composites using Lemke's complementary pivoting algorithm is developed for solving the LCP. The nonlinear analysis is composed of the combination of updated Lagrangian formulation of the frictional contact problem and the nonlinear shear stress-strain relation in each ply. The accuracy, applicability and computational efficiency of the proposed method are confirmed by comparison with previous researches.