边界效应与尺寸效应模型的本质区别及相关设计应用

发布时间：2018-06-04 12:27

本文选题：边界效应 + 尺寸效应　；参考：《水利学报》2017年08期

【摘要】：本文研究了边界效应模型(BEM)与尺寸效应模型(SEM)的本质区别及设计应用功能。研究发现:对于SEM,不同缝高比α的试件须应用4个不同的多参数经验方程,且SEM仅限于试验数据拟合功能。BEM仅有唯一解析解,一方面,可由试验数据拟合确定材料参数——断裂韧度KIC和拉伸强度ft;另一方面,可由已确定的KIC和ft建立描述结构破坏的完整设计曲线。基于BEM,进一步分析了试件到结构变化(尺寸高度W从25到25000 mm),对材料3种破坏模式(ft强度控制、KIC韧度控制、准脆性断裂)的本质影响规律。理论研究表明:对于裂缝非常长和尺寸非常大的结构,已满足线弹性断裂条件,因而无须采用尺寸效应模型。尺寸效应的研究仅可应用于裂缝尖端靠近前边界或者后边界的情况,尺寸效应仅为边界效应的特例。最后,基于W依次为40、93、215和500 mm,α依次为0、0.02、0.075、0.15和0.3的混凝土三点弯曲梁的断裂试验成果,采用BEM系统分析了不同试验数据的组合情况对材料参数KIC和ft确定的影响规律。试验结果分析表明:当试验数据满足一定数量后,从整体数据中任意删去1组或2组数据,采用BEM确定的KIC和ft变化较小而基本一致。由不同尺寸W而相同缝高比α的几何相似试件,或不同缝高比α而相同尺寸W试件的峰值荷载Pmax,都可确定出材料参数KIC和ft。本文所提BEM为解决由小尺寸试件确定无尺寸效应的材料参数,及由材料参数预测实际结构破坏等问题提供了新的思路。
[Abstract]:In this paper, the essential difference between the boundary effect model (BEMM) and the size effect model (SEM) and the function of design and application are studied. It is found that four different multiparameter empirical equations should be applied to the specimen with different ratio of seam to height, and SEM is limited to the fitting function of test data. BEM has only a unique analytical solution. On the one hand, The material parameters, fracture toughness (KIC) and tensile strength (ftt) can be determined by fitting the test data, and on the other hand, the complete design curves describing the structural failure can be established by the determined KIC and ft. Based on BEMs, the essential influence of structural changes (size height W ranging from 25 mm to 25000 mm) on the strength control of KIC and quasi-brittle fracture in three failure modes of materials is further analyzed. The theoretical study shows that the linear elastic fracture condition has been satisfied for the structure with very long cracks and very large size, so it is not necessary to adopt the size effect model. The study of size effect can only be applied to the case where the crack tip is near the front or back boundary, and the size effect is only a special case of the boundary effect. Finally, based on the fracture test results of concrete three-point bending beams with W being 40 ~ 93215 mm and a = 0. 02 0. 075 ~ 0. 15 mm and 伪 0. 3 respectively, the influence of the combination of different test data on the determination of material parameters KIC and ft is analyzed by BEM system. The experimental results show that when the experimental data meet a certain amount, one or two groups of data are deleted arbitrarily from the whole data. The change of KIC and ft determined by BEM is relatively small and basically consistent. The material parameters KIC and FT can be determined by the peak load Pmaxof W specimen with different sizes and the same joint height ratio 伪, or the same size W specimen with different joint height ratio 伪. The BEM proposed in this paper provides a new way to solve the problems of determining the material parameters without size effect from the small size specimen and predicting the actual structure failure by the material parameters.
【作者单位】：华北水利水电大学土木与交通学院;School
【基金】：国家自然科学基金重点项目(51339003);国家自然科学基金项目(51779095) 郑州市科技攻关项目(153PKJGG111)
【分类号】：TV431

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