共查询到19条相似文献,搜索用时 390 毫秒
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鉴于含裂纹的巴西圆盘试验多集中于二维或表面裂纹,而对含纯封闭内裂纹的巴西圆盘断裂研究较少的问题,开展了含90°三维内裂纹的树脂巴西圆盘试样单轴压缩试验,分析了裂纹扩展过程特征,并基于M积分及最大拉应力准则研究了KⅠ、KⅡ、KⅢ分布规律,通过断裂力学有限元软件FRANC3D实现内裂纹扩展全过程模拟。结果表明,含90°内裂纹试样在单轴压缩下裂纹破坏形态为竖直张拉裂纹;达到峰值荷载29.13kN时试样瞬间被劈裂为两半,内裂纹扩展速度达到700mm/s,对试样扩展、破坏形态及断口特征产生显著影响;通过数值模拟得出内裂纹尖端扩展路径,短轴端扩展速率最大,且数值模拟结果与试验相符。 相似文献
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针对混凝土重力坝裂纹开裂扩展问题,基于扩展有限元(XFEM)理论,以Koyna大坝为例,分别建立基于附加质量法和无质量地基法的传统抗震分析模型和基于流固耦合法和粘弹性边界法的新型抗震分析模型,并针对两种模型进行线性时程分析和非线性裂纹扩展模拟分析。结果表明,以流固耦合法和粘弹性边界法建立的坝体-地基-库水抗震分析模型的动力峰值响应整体减小了约30%;传统模型的裂缝张开位移有一定程度的夸大,基于流固耦合法和粘弹性边界法建立的坝体-地基-库水抗震分析模型的裂纹扩展路径与实际振动台试验结果更接近。 相似文献
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运用ADINAT/ADINA有限元程序分析了船舶柴油机活塞的三维温度场和三维应力应变场,并采用带中央环状预裂纹的圆柱形试件在单轴疲劳试验机上进行了热疲劳裂纹扩展寿命模拟试验,根据高温度理论和断裂力学理论归纳了当量J积分范围评分准则,并将这一准则用于活塞的裂纹扩展寿命分析和安全性评定,评定结果具有普遍参考价值。 相似文献
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针对风力机叶片表面裂纹扩展对叶片产生危害的问题,文章对1.5 MW复合材料风力机叶片在19 m/s风速下的应力分布进行了流固耦合计算,发现叶根和叶中位置易产生裂纹。基于扩展有限元(XFEM)研究叶片表面裂纹受力后的扩展问题,90°裂纹的扩展速率最快,叶片表面裂纹主要沿弦向进行扩展。当时间步长为100时,均质和复合材料叶片表面裂纹扩展时的最大应力分别为127.50 MPa和65.34 MPa,且裂纹仅在后者的表层进行扩展,这说明复合材料能阻碍裂纹扩展对叶片的破坏,减少应力集中。同时裂纹在叶片内部的扩展更危险,初始尺寸越大的裂纹,扩展时裂尖越容易产生应力积累。 相似文献
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基于某汽油机硅铝合金活塞的最大爆发工况,建立了装有活塞销的活塞三维有限元模型.对其进行了热强度和机械强度的有限元分析.计算得到活塞的应力集中点的位置,也即裂纹源的位置,通过在活塞实体模型上增加裂纹面及裂纹体,得到裂纹尖端场的应力强度因子,并分析得出机械负荷作用下的应力强度因子对裂纹的扩展起决定作用. 相似文献
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本文根据汽轮机转子材料30CrMoV钢低周循环疲劳和高温疲劳裂纹扩展试验,用暂态变物性温度热弹塑性有限元对冷态启动工况下的汽轮机转子进行应力场分析结果分别进行无裂纹转子疲劳寿命损耗和转子疲劳裂纹扩展估算,并对估算方法及应力强度因子计算进行了初步分析。 相似文献
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A highly efficient numerical approach: extended cohesive damage model (ECDM) for predicting multicrack propagation is introduced in this paper. The ECDM is developed within the framework of the eXtended Finite Element Method (XFEM). Unlike XFEM the enriched degrees of freedom (DoFs) are eliminated from the final condensed equilibrium equations in the ECDM. To account for the cohesive crack effect, an equivalent damage scalar relating to a strain field is introduced in terms of energy dissipation. The ECDM is capable of characterizing discontinuities with conventional DoFs only, thus it is significantly efficient in modelling multicrack propagation. The basic formulations, numerical implementation and detailed investigation of the performance of the ECDM through modelling the selected benchmark specimens are given in this paper. This investigation shows the ECDM can effectively guarantee the convergent solutions in nonlinear fracture analysis and can efficiently reduce the computer CPU time in modelling selected fracture benchmark specimens by more than 60% compared to the XFEM in ABAQUS. Therefore, the ECDM is a robust computational approach for predicting multicrack failure mechanism in engineering materials and structures. 相似文献
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Siddharth Suman Mohd. Kaleem Khan Manabendra Pathak R.N. Singh 《International Journal of Hydrogen Energy》2017,42(29):18668-18673
Influence of hydride precipitated at the tip of the crack on crack propagation in zircaloy-4 is numerically investigated using the extended finite element method (XFEM). Numerical simulation is performed on compact tension specimen to understand the effects of crack and hydride lengths on crack propagation in terms of stress intensity factor and J-integral. The values of stress intensity factor and J-integral indicate that hydride induces the crack instability. The stress intensity factor decreases with the precipitation of brittle hydride phase at the crack tip, resulting in hydride-assisted crack propagation. A comparison of crack propagation behaviour with different hydride lengths is also presented. The crack remains stable in the absence of the hydride while it propagates when hydride is considered at its tip for the same applied load. The crack arrests only after reaching to the zircaloy metal matrix causing complete fracture of hydride. 相似文献
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《International Journal of Hydrogen Energy》2019,44(14):7168-7180
The hydraulic fracturing is extensively used to stimulate the production of fossil hydrogen energy. Perforation parameters have a great influence on the performance of hydraulically fractured horizontal wells in fossil hydrogen energy development. In this work, a practical model to study the effect of a completion scheme on simultaneous fracture propagation is proposed, in which the coupling fluid flow and stress interaction is considered, and a fracture propagation uniform index model is used to optimize the completion strategy. Moreover, this model is well validated by Wu's model and Zhang's model. The numerical study results indicate that a uniform completion scheme causes a non-uniform fracture development; an optimal completion method is proposed by reducing the cluster number, non-uniform spacing, and practical limited entry technique in a fracturing stage. Furthermore, the combined use of unequal cluster spacing and a limited entry strategy can significantly reduce the suppression effects between multiple clusters, improve the fluid flow into each cluster, and enhance the uniform propagation to achieve the maximum production. Our present work illustrates a better understanding of the effect of the completion strategy on the multiple fracture propagation, and paves a path for a more optimal completion design for fossil hydrogen energy development. 相似文献
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Slant ductile rupture is one of the common failure modes in the pressure vessel and piping industry. Such failure in tubing and casing can be the result of excessive internal pressure and/or axial loading. The underlying physics of ductile rupture is essential in predicting the fracture modes and the crack propagation path for ductile metals. The slant fracture phenomenon is studied numerically by adopting a recently developed damage plasticity theory. The damage plasticity theory incorporates all three stress invariants in a nonlinear damaging process of the material. The numerical integration algorithm for the new model is presented for small strain case. Three applications of different loading conditions are shown to illustrate its effectiveness in predicting ductile fracture. Emphasis is given to the influencing factors to slant fracture and the shear nature of the crack pattern in these applications. These numerical solutions are in good agreement with the experimental observations. 相似文献
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Qingchao Li Yudi Li Qiang Li Fuling Wang Jia Wei 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(15):1807-1813
Fracture reorientation affects hydraulic fracturing much in perforated wells. A finite element model used for investigating fracture reorientation is established using the extended finite element method with ABAQUS software. Based on this, both fracture reorientation and fracture propagation during fracturing operation in shale reservoirs are analyzed. Meanwhile, the effect of the difference between the maximum and minimum principal stresses on fracture reorientation during fracturing in shale reservoirs has also been studied. The results demonstrate that the fracture reorients to the direction of the maximum principal stress gradually, and the difference between the maximum and minimum principal stresses impacts the fracture reorientation more than fracture propagation. 相似文献
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《International Journal of Hydrogen Energy》2019,44(54):29047-29056
In order to determine the threshold stress intensity factor and critical hydride length for delayed hydride cracking in Zr-2.5Nb pressure tube alloy, the distribution of normal stress in the plastic zone of crack tip by the developed method that combines theory calculation with extended finite element method (XFEM) was improved. The fracture process of two-phase composites containing Zr-2.5Nb and hydride precipitate was simulated by XFEM. Based on that, critical hydride length corresponding to the theoretical model for K1H was estimated. Meanwhile, to illustrate the validity of theoretical and numerical methods, recent theoretical models and experimental measurements were utilized to verify the results of this paper. The theoretical model of DHC was improved to estimate the critical hydride length corresponding to threshold stress intensity factor. The predicted value of critical hydride length is close to the experimental values. 相似文献
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《International Journal of Hydrogen Energy》2022,47(14):9045-9057
We introduced a coupled peridynamic hydrogen diffusion and fracture model to solve the hydrogen embrittlement fracture of low alloy steel AISI 4340. In this model, the influence of temperature on hydrogen diffusion coefficient is considered, and a new peridynamic constitutive analysis method is used to simulate the crack propagation of hydrogen embrittlement. We verified the model in 3D using the experimental test of the hydrogen embrittlement cracking process of AISI 4340 steel in 0.1 N H2SO4 solution from the literature. Considering different ambient temperatures, it is found that the crack propagation is highly similar to the experimental results. Based on the numerical analysis of peridynamics, the model can numerically simulate the hydrogen embrittlement fracture of AISI 4340 steel, and obtain a visual demonstration of the entire process of hydrogen atom diffusion and crack growth. 相似文献