共查询到19条相似文献,搜索用时 156 毫秒
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提出基于神经网络的裂纹扩展过程实时预测方法,其计算效率比近场动力学(peridynamic,PD)模型提高.使用PD算法获取裂纹扩展过程中的损伤云图,构建裂纹扩展数据集.基于数据集构建生成对抗网络(generative adversarial networks,GAN)模型,根据不同加载条件实时生成损伤云图,从而快速预测裂纹的扩展过程.将PD模型计算得到的损伤云图中的RGB值与相应位置处的损伤值结合,构建多层前馈神经网络模型的数据库,并使用多层前馈神经网络模型分析GAN模型产生的损伤云图,得到相应的损伤值.通过数值算例证明该方法的效率和准确性. 相似文献
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基于二次插值重构有限元法(Twice interpolation Finite Element Method, TFEM)分析动态断裂力学问题并进行数值实验,考察TFEM在裂纹动态扩展模拟中的准确性和可靠性.由于TFEM保证节点处梯度场的连续性,因此裂尖附近的应力场可以得到较好的逼近.把该算法成功移植到自主开发的三维裂纹扩展仿真软件(ZonCrack)中.利用ZonCrack进行的裂纹扩展,分析结果表明:TFEM得到裂尖应力强度因子(Stress Intensity Factor, SIF)与解析解基本一致;裂纹扩展的模拟结果与实验值吻合良好. 相似文献
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使用近场动力学常规态理论对于弹体高速侵彻陶瓷/金属复合靶板进行了数值仿真,并讨论了态理论中的适用性问题.分别采用弹性和J2率无关弹塑性本构模型进行了陶瓷/金属靶板的PD建模,模拟了刚性弹体高速侵彻陶瓷复合靶板的过程,获得了弹体的速度时程曲线、靶板的破坏模式及靶板飞溅的情况,并将仿真结果与有限元结果及实验对比.采用不同的影响函数及近场作用范围计算得到靶板的裂纹扩展模式.结果表明通过采用合适的本构模型PD方法可以有效准确地模拟复合靶板受弹体高速侵彻的全过程,存在较优的影响函数与近场作用范围使得计算结果准确. 相似文献
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为了解决传统混凝土承载力算法存在峰值负荷计算值误差较大的问题,本文提出基于有限元模型的建筑混凝土柱屈曲承载力计算方法.通过有限元模型,对混凝土柱进行有限元数值模拟分析,模拟其屈曲力学性能,判断混凝土柱整体抗屈曲强度,确定屈曲承载力极限时的应力-应变关系曲线,并完成曲线参数计算.此次算法与两种传统算法进行对比实验,对三组混凝土柱试件进行破坏,比较峰值负荷计算值和试验值,结果表明,此次算法减小了峰值负荷的计算误差,此次算法的屈曲承载力计算结果更为准确. 相似文献
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为研究裂纹倾角对煤体破坏特征及声发射响应特征的影响,利用RFPA2D数值模拟软件对单轴压缩下含不同预制裂纹倾角的煤样进行模拟,分析裂纹倾角对试样裂纹扩展模式、力学性能和声发射响应特征的影响。结果表明,当预制裂纹倾角α为0°时,主破裂沿垂直于预制裂纹中间位置的方向扩展;对于α为15,30,45,60,75°的试样,其主裂纹扩展模式为典型的翼裂纹,或者是翼裂纹基础上发展而来的"Y"形裂纹;而α为90°的试样和完整试样,其主裂纹分布存在随机性。裂纹的存在降低了煤体的峰值强度和弹性模量,且峰值强度和弹性模量随裂纹倾角的增加而增加,前者呈二次函数的关系增加,后者呈倾斜的"S"形增加。此外,随着预制裂纹倾角的增加,煤样由延性破坏逐渐向脆性破坏过渡。破裂时声发射瞬时计数存在阶段性增长,即α为0~45,60~75,90°和完整试样,此3个阶段的试样破裂时瞬时声发射计数依次递增。 相似文献
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This study develops a novel hybrid method that combines the finite element method (FEM) and the scaled boundary finite element method (SBFEM) for crack propagation modelling in brittle and quasi-brittle materials. A very simple yet flexible local remeshing procedure, solely based on the FE mesh, is used to accommodate crack propagation. The crack-tip FE mesh is then replaced by a SBFEM rosette. This enables direct extraction of accurate stress intensity factors (SIFs) from the semi-analytical displacement or stress solutions of the SBFEM, which are then used to evaluate the crack propagation criterion. The fracture process zones are modelled using nonlinear cohesive interface elements that are automatically inserted into the FE mesh as the cracks propagate. Both the FEM’s flexibility in remeshing multiple cracks and the SBFEM’s high accuracy in calculating SIFs are exploited. The efficiency of the hybrid method in calculating SIFs is first demonstrated in two problems with stationary cracks. Nonlinear cohesive crack propagation in three notched concrete beams is then modelled. The results compare well with experimental and numerical results available in the literature. 相似文献
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在机器视觉疲劳裂纹扩展试验中,为了能够满足对裂纹宏观观察裂纹和准确定位裂纹尖端的要求,需要采用变焦镜头放大和缩小采集图像范围,针对于摄像头变焦后的聚焦问题,提出了摄像头的自动聚焦方法。首先建立图像采集系统,采集裂纹图像至计算机,通过中值滤波对图像预处理,去除噪声干扰,选取裂纹区域作为聚焦窗口,采用Laplace算子法作为清晰度评价函数,并提出一种变步长穷举法进行聚焦搜索。最后设计了以ARM7为核心的摄像头运动控制器。实验表明,所提出的方法能够实现疲劳裂纹扩展试验中摄像头在各种情况下的准确自动聚焦,为下一步精确测量疲劳裂纹扩展参数奠定基础。 相似文献
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Fast crack detection method for large-size concrete surface images using percolation-based image processing 总被引:3,自引:0,他引:3
The detection of cracks on concrete surfaces is the most important step during the inspection of concrete structures. Conventional crack detection methods are performed by experienced human inspectors who sketch crack patterns manually; however, such detection methods are expensive and subjective. Therefore, automated crack detection techniques that utilize image processing have been proposed. Although most the image-based approaches focus on the accuracy of crack detection, the computation time is also important for practical applications because the size of digital images has increased up to 10 megapixels. We introduce an efficient and high-speed crack detection method that employs percolation-based image processing. We propose termination- and skip-added procedures to reduce the computation time. The percolation process is terminated by calculating the circularity during the processing. Moreover, percolation processing can be skipped in subsequent pixels according to the circularity of neighboring pixels. The experimental result shows that the proposed approach efficiently reduces the computation cost. 相似文献
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Ali O. Ayhan 《Computers & Structures》2011,89(9-10):801-812
A three-dimensional methodology for simulation of fatigue crack propagation is presented. The method is leveraged by the use of enriched crack tip elements to compute the mixed-mode stress intensity factors. The crack growth model used and the crack propagation life calculation are also described. As examples, fatigue crack propagation of a mode-I surface crack and crack advancements of mixed-mode surface cracks are simulated. The predicted results showed excellent agreement with experimental data from the literature. Thus, it is concluded that the crack propagation method developed allows efficient and accurate simulation of three-dimensional fatigue crack propagation problems. 相似文献
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A numerical procedure based on the finite element method is developed for the geometric and material nonlinear analysis of reinforced concrete members containing steel fibres and subjected to monotonic loads. The proposed procedure is capable of tracing the displacements, strains, stresses, crack propagation, and member end actions of these structures up to their ultimate load ranges. A frame element with a composite layer system is used to model the structure. An iterative scheme based on Newton-Raphson's method is employed for the nonlinear solution algorithm. The constitutive models of the nonlinear material behaviour are presented to take into account the nonlinear stress-strain relationships, cracking, crushing of concrete, debonding and pull-out of the steel fibres, and yielding of the reinforcement. The geometric nonlinearity due to the geometrical change of both the structure and its elements are also represented. The numerical solution of a number of reinforced fibrous concrete members are compared with published experimental test results and showed good agreement. 相似文献
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为研究混凝土梁的断裂过程,提出用基于二维扩展有限元法(eXtended Finite ElementMethod,XFEM)的黏聚性裂缝模型模拟混凝土简支梁在集中载荷作用下的断裂过程.推导考虑近裂尖奇异性的基于XFEM的黏聚性裂缝模型,得出裂缝开度随裂缝长度的变化曲线;对上述模型与相关文献用有限元结合节点释放技术对相同时间的裂缝扩展的计算结果进行比较,二者结果吻合良好,并与实际裂缝扩展过程相符.计算结果证实基于XFEM的黏聚性裂缝模型能有效进行混凝土梁的断裂过程模拟. 相似文献
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This paper deals with a numerical and experimental investigation on the influence of residual stresses on fatigue crack growth in AA2024-T3 friction stir welded butt joints. The computational approach is based on the sequential usage of the Finite Element Method (FEM) and the Dual Boundary Element Method (DBEM). Linear elastic FE simulations are performed to evaluate the process induced residual stresses, by means of the contour method. The computed stress field is transferred to a DBEM environment and superimposed to the stress field produced by a remote fatigue traction load applied on a friction stir welded cracked specimen; the crack propagation is then simulated according to a two-parameter growth model. Numerical results have been compared with experimental data showing good agreement and evidencing the predictive capability of the proposed method. The obtained results highlight the influence of the residual stress distribution on crack growth. 相似文献
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《Advances in Engineering Software》2010,41(2):111-119
A numerical method for 2D LEFM crack propagation simulation is presented. This uses a Lepp–Delaunay based mesh refinement algorithm for triangular meshes which allows both the generation of the initial mesh and the local modification of the current mesh as the crack propagates. For any triangle t, Lepp(t) (Longest Edge Propagation Path of t) is a finite, ordered list of increasing longest edge neighbor triangles, that allows to find a pair of triangles over which mesh refinement operations are easily and locally performed. This is particularly useful for fracture mechanics analysis, where high gradients of element size are needed. The crack propagation is simulated by using a finite element model for each crack propagation step, then the mesh near the crack tip is modified to take into account the crack advance. Stress intensify factors are calculated using the displacement extrapolation technique while the crack propagation angle is calculated using the maximum circumferential stress method. Empirical testing shows that the behavior of the method is in complete agreement with experimental results reported in the literature. Good results are obtained in terms of accuracy and mesh element size across the geometry during the process. 相似文献
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BAO TengFei QIN Dong ZHOU XiWu & WU GuiFen State Key Laboratory of Hydrology-Water Resources Hydraulic Engineering Hohai University Nanjing China National Engineering Research Center of Water Resources Efficient Utilization Engineering Safety Jiangsu Province Water Resources Engineering Consulted Co. Ltd. Nanjing China Huadian Engineering Co. Ltd. Beijing 《中国科学:信息科学(英文版)》2011,(7)
The abnormality monitoring model (AMM) of cracks in concrete dams is established through integrating safety monitoring theories with abnormality diagnosis methods of cracks. In addition, emphasis is placed on the influence of crack depth on crack mouth opening displacement (CMOD). A linear hypothesis is proposed for the propagation process of cracks in concrete based on the fictitious crack model (FCM). Abnormality points are detected through testing methods of dynamical structure mutation and statistical m... 相似文献