共查询到19条相似文献，搜索用时 31 毫秒
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采用随机骨料模型模拟混凝土的细观结构,利用有限元方法数值模拟混凝土试件单轴抗压的细观损伤断裂,并重点对单轴抗压强度尺寸效应进行研究。 相似文献
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采用随机骨料模型模拟混凝土的细观结构，利用有限元方法数值模拟混凝土试件单轴抗压的细观损伤断裂，并重点对单轴抗压强度尺寸效应进行研究。 相似文献
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鉴于目前岩石动态断裂韧度在研究方法上没有统一的标准,有必要对其进行研究。使用花岗岩制作中心裂纹圆盘试件,预制裂纹的宽度控制在1mm左右,在SHPB试验系统下进行动态冲击,得出试件两端的平均载荷带入到推广的中心裂纹圆盘试件应力强度因子计算公式算出动态断裂韧度。 相似文献
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采用反射式焦散线方法对水泥石中添加玻璃纤维后的强度变化问题进行了实验研究.首先,制作了不添加与添加玻璃纤维的2种水泥石试件,并采用镜面移植方法在试件的表面进行反射镜面的制作与加工.然后,采用多火花式高速摄影系统对试件在冲击断裂过程中的裂纹扩展和裂纹尖端焦散线的情景进行记录.最后,对2种试件的裂纹起裂时间、动态应力强度因子和裂纹扩展速度等参数进行计算和对比分析.分析发现,玻璃纤维提高了水泥石的断裂韧度、延迟了裂纹的起裂时间,对水泥石具有明显的强化效应.实验结果对研究水泥石的断裂力学属性特征具有一定意义. 相似文献
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研究目的:研究混凝土失稳韧度的理论预测方法。创新要点:1.提出混凝土失稳韧度的理论预测方法;2.利用楔入劈拉试件计算不同级配混凝土的失稳韧度;3.研究失稳韧度受拉伸软化曲线的影响。研究方法:1.基于起裂韧度扩展准则,采用理论分析手段研究混凝土的失稳韧度计算方法;2.利用楔入劈拉试件(见图3)计算不同级配混凝土的失稳韧度。重要结论:1.基于起裂韧度准则可合理地预测峰值荷载状态及失稳韧度;2.混凝土失稳韧度受断裂能的影响较小;3.拉伸软化曲线对混凝土失稳韧度的影响较小。 相似文献
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提出了一种利用非对称三点弯曲加载下的单边垂直切槽深梁试件(SEVNDB)开展岩石Ⅰ-Ⅱ复合断裂韧度测试方法。通过有限元法对试件的无量纲应力强度因子进行了数值分析与标定,研究了无量纲应力强度因子YⅠ、YⅡ及无量纲T应力T*与裂纹长度a、支座间距S1、S2之间的关系,定量刻画了实现纯Ⅱ型加载对应的裂纹长度a、支座间距(S1和S2)数值。研究结果表明,该方法在不改变试样裂缝倾角的前提下,通过调整裂缝长度a和支座间距S1、S2,即可方便地实现从纯Ⅰ型到纯Ⅱ型任意复合度载荷作用下的岩石断裂韧度测试。 相似文献
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呼玉琴 《安阳师范学院学报》2013,(2):36-38
采用ANSYN对四个简支部分外包混凝土组合梁试件的受力性能进行非线性分析。部分外包混凝土组合梁数值模拟结果与试验结果吻合较好,表明可以利用有限元方法研究组合梁的工作性能。 相似文献
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对混凝土立方体试件施加竖向荷载,同步进行应力应变测量,结合实时法预估混凝土出现宏观裂纹的时间,运用损伤力学理论,给出一种预估混凝土试件工作寿命的试验方法. 相似文献
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The fracture processes of concrete were described by a cohesive crack model based on initial toughness criterion. The corresponding analytical method to predict the instability state was proposed. In this model, the initial toughness was adopted as the crack propagation criterion and the weight function method was used to calculate the stress intensity factor and the crack opening displacement caused by the cohesive stress. The unstable toughness can be easily obtained using the proposed method without measuring parameters at the critical state that was necessary in traditional methods. The proposed method was verified by existing experimental data of wedge splitting specimens with different grades of concrete and the sensitivity of the results on the tensile softening curve was discussed. The results demonstrate that the proposed method can well predict the peak load, the critical effective crack length, and the unstable toughness of concrete specimens. Moreover, the calculated unstable toughness is not sensitive to the tensile softening curve. 相似文献
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The mechanism and criterion of crack initiation and propagation of rocks were investigated by many researchers,And the creep behaviour of rocks was also theoretically and experimentally studied by some scientists and engineers.The characteristics of crack initation and propagation of rocks under creep condition.however,are very improtant for rock engineering and still not paid enough attention by researchers,In this paper,the criterion and mechanism of crack initiation and propagation under creep condition were investigated using specimens collected from sandstone rock formations outcropping in the Emei Mountain,the Sichuan Province of China.Cuboid specimens under three point bending were used in this investigation.All specimens were classified into four sorts and used for Mode-I fracutre of creep frcture tests.The experimental result shows that due to creep deformation.rock crack will inevitably initialt and propagate under a load of KI,which is less than fracture toughness KIC but not less than a constant(marked as KIC2),KIC2 indicates the ability of rock to resist crack initiation and propagation under creep conditions and is less than fracture tough ness KIC.defined as creep fracture toughness in this paper,KIC2 should be considered as an importnat parameter on design and computation of rock engineering.The microstructureal mechanism for crack initiation and propagation of rock materials under creep condition was introduced based on competitive model between softening effect and hardening effect,and the validity of test result was explained.The test result was also verified in rheological theory.When KI is more than KIC2 but less than KIC,rock crack will initiate and propagate after a time interval of sustained loading under creep condition.In order to find the relation between duration of sustained lading.which can lead to crack initiation and propagation,and the initial stress intensity factor KI,an unequal0interval time sequence forecasting and predicting model was introduced,and the relation was obtained for homogeneous and isotropic fine-grained red sandstone.Finally a modified fracture toughness formula was given,in which the influence of fracture process zone(FPZ) was fully considered. 相似文献
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Xian-kui Zhu 《浙江大学学报(A卷英文版)》2009,10(11):1541-1560
In this paper a critical review is presented ofthe history and current state of the art of J-integral resistance curve testing and experimental evaluation methods in conjunction with a discussion of the development of the plane strain fracture toughness test standard ASTM E 1820 developed by American Society for Testing and Materials （ASTM）. Early research efforts on this topic are reviewed first, These include the J-integral concept, experimental estimates of the J-integral for stationary cracks, load line displacement （LLD） and crack mouth opening displacement （CMOD） based ηfactor equations, different formulations of J-integral incremental equations for growing cracks, crack growth corrected .JR curve determination, and experimental test methods. Recent developments in J-R curve testing and evaluation are then described, with emphasis on accurate J-integral incremental equations, a normalization method, a modified basic method, a CMOD direct method with use of incremental equations, relationships of plastic geometry factors, constraint-dependent J-R curve testing and correction approaches. An overview of the present fracture toughness test standard ASTM E1820-08a is then presented. The review shows that after more than 40 years of investigation and development, the J-integral resistance curve test methods in ASTM E1820 have become simpler, more cost-effective and more accurate. 相似文献
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为研究偏心距对钢-连续纤维复合筋(SFCB)混凝土柱的受压性能,对7根混凝土强度等级为C35的SFCB混凝土柱进行静力受压试验,其中纵筋采用内芯钢筋6mm外包BFRP的SFCB。分析了偏心距对试件承载力、挠度、裂缝及破坏形态的影响。研究表明,偏心距越大,柱中挠度越大,最大裂缝宽度越大,极限承载力越小。 相似文献
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王博 《商洛师范专科学校学报》2014,(4):42-45
以水泥混凝土路面的裂缝检测及特征提取为研究对象。利用Matlab的数字图像处理技术,对采集到的水泥路面裂缝图像进行了一系列处理,最终达到提取裂缝特征数据的目的。结果表明：对图像的灰度化、中值滤波、平滑、锐化分割以及形态学处理后,裂缝图像有明显去噪效果、平滑效果、边缘模糊影响最小,所用裂缝计算方法可以准确地得到线性裂缝的长度以及网状裂缝的面积。 相似文献
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杜志坚 《杨凌职业技术学院学报》2005,4(2):28-29
灌区节水改造工程项目,渠道衬砌多用现浇混凝土。工程交付使用一段时间后,由于冻害等原因,渠道衬砌产生不同程度的横向、纵向及不规则裂缝。结合渠基土性质及混凝土特性,对现浇混凝土衬砌裂缝产生的原因及其危害进行了分析,并提出相应的防治措施和管理办法。 相似文献
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夏俊海 《河北能源职业技术学院学报》2004,4(4):57-58,63
混凝土裂缝是建筑工程中最常见的质量通病之一,不同部位、不同程度的裂缝对工程质量都有不同的影响。规范对裂缝的程度做出了严格的界定。超过规范允许的裂缝,一旦处理不及时或处理方法不当,都会造成工程质量事故隐患。科学的分析裂缝产生的原因,采取正确的方法预防和处理。是我们每个工程技术人员都应树立的牢固思想。 相似文献
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罗文伟 《北京工业职业技术学院学报》2014,13(1):125-127
建筑物在建造和使用过程中,常常会出现各种情况的裂缝,引起建筑物裂缝的因素很多,有温度裂缝、混凝土干缩裂缝、施工不当等因素.建筑物出现裂缝后,从表面上看影响美观,当裂缝过大后将对建筑物结构产生影响,因此对建筑物产生的裂缝原因进行分析具有重要意义.通过对实际工程裂缝产生原因的分析,给出各种情况下的裂缝处理措施,并提出了在设计及施工阶段需要注意的问题. 相似文献
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Fully automatic finite element （FE） modelling of the fracture process in quasi-brittle materials such as concrete and rocks and ductile materials such as metals and alloys, is of great significance in assessing structural integrity and presents tremendous challenges to the engineering community. One challenge lies in the adoption of an objective and effective crack propagation criterion. This paper proposes a crack propagation criterion based on the principle of energy conservation and the cohesive zone model （CZM）. The virtual crack extension technique is used to calculate the differential terms in the criterion. A fully-automatic discrete crack modelling methodology, integrating the developed criterion, the CZM to model the crack, a simple remeshing procedure to accommodate crack propagation, the J2 flow theory implemented within the incremental plasticity framework to model the ductile materials, and a local arc-length solver to the nonlinear equation system, is developed and implemented in an in-house program. Three examples, i.e., a plain concrete beam with a single shear crack, a reinforced concrete （RC） beam with multiple cracks and a compact-tension steel specimen, are simulated. Good agreement between numerical predictions and experimental data is found, which demonstrates the applicability of the criterion to both quasi-brittle and ductile materials. 相似文献